Electric Motor Defects: Comprehensive Spectral Analysis<\/title>\n\n<link rel=\"preconnect\" href=\"https:\/\/fonts.googleapis.com\">\n<link rel=\"preconnect\" href=\"https:\/\/fonts.gstatic.com\" crossorigin>\n<link href=\"https:\/\/fonts.googleapis.com\/css2?family=DM+Serif+Display:ital@0;1&family=Source+Sans+3:ital,wght@0,300;0,400;0,500;0,600;0,700;1,400;1,500&family=JetBrains+Mono:wght@400;500&display=swap\" rel=\"stylesheet\">\n<style>\n:root {\n --bg: #f5f2ed;\n --bg-warm: #ece8e1;\n --card: #ffffff;\n --card-alt: #faf8f5;\n --border: #d9d3c7;\n --border-light: #e8e3da;\n --accent: #2d5a27;\n --accent-light: #3d7a35;\n --accent-bg: #e8f0e6;\n --accent-bg2: rgba(45,90,39,0.06);\n --secondary: #8b6914;\n --secondary-light: #b8922e;\n --secondary-bg: #fdf6e3;\n --text: #2c2a26;\n --text-body: #3d3b36;\n --text-muted: #7a756b;\n --text-light: #9e9889;\n --heading: #1a1815;\n --red: #b8372b;\n --red-bg: #fdf0ee;\n --blue: #2a5a8c;\n --blue-bg: #eef4fa;\n --blue-light: #5a8ab8;\n 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.workflow-step:not(:last-child)::after{display:none}\n .workflow-step{border-radius:var(--radius-sm)!important;margin-bottom:8px}\n}\n<\/style>\n<\/head>\n<body>\n\n<div class=\"progress-bar\" id=\"progressBar\" style=\"width:0%\"><\/div>\n<button class=\"back-to-top\" id=\"backToTop\" onclick=\"window.scrollTo({top:0,behavior:'smooth'})\">\n <svg width=\"20\" height=\"20\" viewBox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2.5\" stroke-linecap=\"round\" stroke-linejoin=\"round\"><polyline points=\"18 15 12 9 6 15\"\/><\/svg>\n<\/button>\n\n<div class=\"page-wrapper\">\n\n\n<aside class=\"sidebar\">\n <div class=\"sidebar-logo\">VibroMera<\/div>\n <div class=\"sidebar-subtitle\">Technical Knowledge Base<\/div>\n <div class=\"toc-title\">Table of Contents<\/div>\n <ul class=\"toc-list\">\n <li><a href=\"#fundamentals\" data-section=\"fundamentals\">1. Electrical Fundamentals<\/a><\/li>\n <li><a href=\"#methods\" data-section=\"methods\">2. Diagnostic Methods<\/a><\/li>\n <li><a href=\"#stator\" data-section=\"stator\">3. Stator Defects<\/a><\/li>\n <li><a href=\"#stator-eccentricity\" data-section=\"stator-eccentricity\" class=\"toc-sub\">3.1 Stator Eccentricity<\/a><\/li>\n <li><a href=\"#loose-windings\" data-section=\"loose-windings\" class=\"toc-sub\">3.2 Loose Windings<\/a><\/li>\n <li><a href=\"#loose-cable\" data-section=\"loose-cable\" class=\"toc-sub\">3.3 Loose Power Cable<\/a><\/li>\n <li><a href=\"#shorted-laminations\" data-section=\"shorted-laminations\" class=\"toc-sub\">3.4 Shorted Laminations<\/a><\/li>\n <li><a href=\"#inter-turn\" data-section=\"inter-turn\" class=\"toc-sub\">3.5 Inter-Turn Short<\/a><\/li>\n <li><a href=\"#rotor\" data-section=\"rotor\">4. Rotor Defects<\/a><\/li>\n <li><a href=\"#broken-bars\" data-section=\"broken-bars\" class=\"toc-sub\">4.1 Broken Rotor Bars<\/a><\/li>\n <li><a href=\"#rotor-eccentricity\" data-section=\"rotor-eccentricity\" class=\"toc-sub\">4.2 Rotor Eccentricity<\/a><\/li>\n <li><a href=\"#rotor-bow\" data-section=\"rotor-bow\" class=\"toc-sub\">4.3 Thermal Rotor Bow<\/a><\/li>\n <li><a href=\"#em-field-shift\" data-section=\"em-field-shift\" class=\"toc-sub\">4.4 EM Field Displacement<\/a><\/li>\n <li><a href=\"#bearings-electrical\" data-section=\"bearings-electrical\">5. Bearing Electrical Defects<\/a><\/li>\n <li><a href=\"#vfd\" data-section=\"vfd\">6. VFD Effects<\/a><\/li>\n <li><a href=\"#differential\" data-section=\"differential\">7. Differential Diagnostics<\/a><\/li>\n <li><a href=\"#instrumentation\" data-section=\"instrumentation\">8. Instrumentation<\/a><\/li>\n <li><a href=\"#standards\" data-section=\"standards\">9. Normative References<\/a><\/li>\n <li><a href=\"#conclusion\" data-section=\"conclusion\">10. Conclusion<\/a><\/li>\n <\/ul>\n<\/aside>\n\n\n<main class=\"main-content\">\n\n\n<header class=\"hero\">\n <span class=\"hero-badge\">Spectral Vibration Analysis<\/span>\n <h1>Electric Motor Defects: Comprehensive Spectral Analysis<\/h1>\n <p class=\"hero-intro\">Electric motors consume approximately <strong>45% of all industrial electricity<\/strong> worldwide. According to EPRI studies, failures distribute as: <strong>~23% stator faults<\/strong>, <strong>~10% rotor defects<\/strong>, <strong>~41% bearing degradation<\/strong>, and <strong>~26% external factors<\/strong>. Many of these failure modes leave distinct fingerprints in the vibration spectrum \u2014 long before a catastrophic breakdown occurs.<\/p>\n <p class=\"hero-intro\">This article provides a comprehensive guide to identifying electric motor defects through spectral vibration analysis and complementary techniques: MCSA, ESA, and MCA.<\/p>\n <div class=\"hero-meta\">\n <span class=\"hero-meta-item\">\n <svg viewBox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\"><path d=\"M12 8v4l3 3\"\/><circle cx=\"12\" cy=\"12\" r=\"10\"\/><\/svg>\n 25 min read\n <\/span>\n <span class=\"hero-meta-item\">\n <svg viewBox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\"><path d=\"M4 19.5A2.5 2.5 0 0 1 6.5 17H20\"\/><path d=\"M6.5 2H20v20H6.5A2.5 2.5 0 0 1 4 19.5v-15A2.5 2.5 0 0 1 6.5 2z\"\/><\/svg>\n ISO 20816 \u00b7 IEC 60034 \u00b7 IEEE 1415\n <\/span>\n <span class=\"hero-meta-item\">\n <svg viewBox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\"><path d=\"M20 7h-9\"\/><path d=\"M14 17H5\"\/><circle cx=\"17\" cy=\"17\" r=\"3\"\/><circle cx=\"7\" cy=\"7\" r=\"3\"\/><\/svg>\n Balanset-1A\n <\/span>\n <\/div>\n<\/header>\n\n\n<div class=\"stat-row\">\n <div class=\"stat-card\"><div class=\"stat-number\">~23%<\/div><div class=\"stat-label\">Stator faults<\/div><\/div>\n <div class=\"stat-card\"><div class=\"stat-number\">~10%<\/div><div class=\"stat-label\">Rotor defects<\/div><\/div>\n <div class=\"stat-card\"><div class=\"stat-number\">~41%<\/div><div class=\"stat-label\">Bearing degradation<\/div><\/div>\n <div class=\"stat-card\"><div class=\"stat-number\">~26%<\/div><div class=\"stat-label\">External factors<\/div><\/div>\n<\/div>\n\n\n<h2 id=\"fundamentals\"><span class=\"section-num\">1.<\/span> Electrical Fundamentals for the Vibration Analyst<\/h2>\n\n<p>Before diagnosing motor defects from vibration spectra, it is essential to understand the key electrical frequencies that drive motor vibration.<\/p>\n\n<h3>1.1. Line Frequency (LF)<\/h3>\n<p>The AC supply frequency: <strong>50 Hz<\/strong> in most of Europe, Asia, Africa, and Russia; <strong>60 Hz<\/strong> in North America and parts of South America and Asia. All electromagnetic forces in the motor are derived from this frequency.<\/p>\n\n<h3>1.2. Twice Line Frequency (2\u00d7LF)<\/h3>\n<p>The <strong>dominant electromagnetic force frequency<\/strong> in AC motors. In a 50 Hz system, 2\u00d7LF = <strong>100 Hz<\/strong>; in a 60 Hz system, 2\u00d7LF = <strong>120 Hz<\/strong>. The magnetic attraction force between stator and rotor peaks twice per electrical cycle, making 2\u00d7LF the fundamental \"electrical vibration\" frequency of every AC motor.<\/p>\n\n<div class=\"formula\">2\u00d7LF = 2 \u00d7 f<sub>line<\/sub> = 100 Hz (50 Hz systems) | 120 Hz (60 Hz systems)<\/div>\n\n<h3>1.3. Synchronous Speed and Slip<\/h3>\n<p>The stator magnetic field rotates at synchronous speed:<\/p>\n<div class=\"formula\">N<sub>s<\/sub> = 120 \u00d7 f<sub>line<\/sub> \/ P (RPM)<\/div>\n<p>where <strong>P<\/strong> is the number of poles. An induction motor rotor always rotates slightly slower. This difference is <strong>slip<\/strong>:<\/p>\n<div class=\"formula\">s = (N<sub>s<\/sub> \u2212 N) \/ N<sub>s<\/sub><\/div>\n<p>Typical full-load slip for standard induction motors: <strong>1\u20135%<\/strong>. For a 2-pole motor at 50 Hz: N<sub>s<\/sub> = 3000 RPM, actual speed \u2248 2940\u20132970 RPM.<\/p>\n\n<h3>1.4. Pole Pass Frequency (F<sub>p<\/sub>)<\/h3>\n<p>The rate at which rotor poles \"slip past\" stator poles. The result is <strong>universal<\/strong> \u2014 independent of pole count:<\/p>\n<div class=\"formula\">F<sub>p<\/sub> = 2 \u00d7 s \u00d7 f<sub>line<\/sub> = 2 \u00d7 f<sub>s<\/sub> \u2014 independent of pole count P<\/div>\n<p>For a motor running at 50 Hz with 2% slip: F<sub>p<\/sub> = 2 \u00d7 0.02 \u00d7 50 = <strong>2 Hz<\/strong>. This frequency appears as characteristic sidebands in spectra of broken rotor bars.<\/p>\n\n<h3>1.5. Rotor Bar Pass Frequency<\/h3>\n<div class=\"formula\">f<sub>RBPF<\/sub> = R \u00d7 f<sub>rot<\/sub><\/div>\n<p>Where R is the number of rotor bars. This frequency and its sidebands become significant when rotor bars are damaged.<\/p>\n\n<h3>1.6. Key Frequency Reference Table<\/h3>\n<div class=\"table-wrap\">\n<table>\n<thead><tr><th>Symbol<\/th><th>Name<\/th><th>Formula<\/th><th>Example (50 Hz, 2-pole, 2% slip)<\/th><\/tr><\/thead>\n<tbody>\n<tr><td><code>LF<\/code><\/td><td>Line frequency<\/td><td>f<sub>line<\/sub><\/td><td>50 Hz<\/td><\/tr>\n<tr><td><code>2\u00d7LF<\/code><\/td><td>Twice line frequency<\/td><td>2 \u00d7 f<sub>line<\/sub><\/td><td>100 Hz<\/td><\/tr>\n<tr><td><code>f<sub>sync<\/sub><\/code><\/td><td>Synchronous frequency<\/td><td>2 \u00d7 f<sub>line<\/sub> \/ P<\/td><td>50 Hz (P=2) | 25 Hz (P=4)<\/td><\/tr>\n<tr><td><code>1X<\/code><\/td><td>Rotational frequency<\/td><td>(1 \u2212 s) \u00d7 f<sub>sync<\/sub><\/td><td>49 Hz (2940 RPM)<\/td><\/tr>\n<tr><td><code>F<sub>p<\/sub><\/code><\/td><td>Pole pass frequency<\/td><td>2 \u00d7 s \u00d7 f<sub>line<\/sub><\/td><td>2 Hz<\/td><\/tr>\n<tr><td><code>f<sub>RBPF<\/sub><\/code><\/td><td>Rotor bar pass freq.<\/td><td>R \u00d7 f<sub>rot<\/sub><\/td><td>16 \u00d7 49 = <strong>784 Hz<\/strong><\/td><\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n\n<div class=\"key-fact red\">\n <div class=\"key-fact-label\">Critical Note<\/div>\n <p>In a 50 Hz system, <code>2\u00d7LF = 100 Hz<\/code> and <code>2X \u2248 98 Hz<\/code> (for a 2-pole motor). These two peaks are only <strong>2 Hz apart<\/strong>. Spectral resolution of <strong>\u2264 0.5 Hz<\/strong> is required to separate them. Use <strong>record lengths of 4\u20138 s or more<\/strong>. Misidentifying 2X as 2\u00d7LF leads to fundamentally wrong diagnoses \u2014 confusing a mechanical defect with an electrical one. <em>This proximity is specific to 2-pole machines. For 4-pole: 2X \u2248 49 Hz \u2014 well separated from 2\u00d7LF = 100 Hz.<\/em><\/p>\n<\/div>\n\n\n<div class=\"infographic\">\n<div class=\"infographic-title\">Motor Cross-Section: Key Components and Air Gap<\/div>\n<svg viewBox=\"0 0 620 380\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" style=\"max-width:100%;\" role=\"img\">\n <rect x=\"0\" y=\"0\" width=\"620\" height=\"380\" rx=\"12\" fill=\"#faf8f5\"\/>\n <circle cx=\"210\" cy=\"195\" r=\"140\" fill=\"#e8e3da\" stroke=\"#2a5a8c\" stroke-width=\"2.5\"\/>\n <circle cx=\"210\" cy=\"195\" r=\"108\" fill=\"#faf8f5\" stroke=\"#2a5a8c\" stroke-width=\"1.5\"\/>\n <g fill=\"#eaf5f5\" stroke=\"#2a7a7a\" stroke-width=\"1\">\n <rect x=\"196\" y=\"56\" width=\"28\" height=\"16\" rx=\"3\"\/>\n <rect x=\"196\" y=\"318\" width=\"28\" height=\"16\" rx=\"3\"\/>\n <rect x=\"78\" y=\"122\" width=\"16\" height=\"24\" rx=\"3\" transform=\"rotate(-30 88 134)\"\/>\n <rect x=\"322\" y=\"122\" width=\"16\" height=\"24\" rx=\"3\" transform=\"rotate(30 332 134)\"\/>\n <rect x=\"78\" y=\"240\" width=\"16\" height=\"24\" rx=\"3\" transform=\"rotate(30 88 252)\"\/>\n <rect x=\"322\" y=\"240\" width=\"16\" height=\"24\" rx=\"3\" transform=\"rotate(-30 332 252)\"\/>\n <rect x=\"148\" y=\"60\" width=\"16\" height=\"22\" rx=\"3\" transform=\"rotate(-60 156 71)\"\/>\n <rect x=\"256\" y=\"60\" width=\"16\" height=\"22\" rx=\"3\" transform=\"rotate(60 264 71)\"\/>\n <rect x=\"60\" y=\"178\" width=\"16\" height=\"22\" rx=\"3\"\/>\n <rect x=\"344\" y=\"178\" width=\"16\" height=\"22\" rx=\"3\"\/>\n <rect x=\"148\" y=\"308\" width=\"16\" height=\"22\" rx=\"3\" transform=\"rotate(60 156 319)\"\/>\n <rect x=\"256\" y=\"308\" width=\"16\" height=\"22\" rx=\"3\" transform=\"rotate(-60 264 319)\"\/>\n <\/g>\n <circle cx=\"210\" cy=\"195\" r=\"90\" fill=\"none\" stroke=\"#9a6b12\" stroke-width=\"3\" stroke-dasharray=\"7,4\"\/>\n <circle cx=\"210\" cy=\"195\" r=\"82\" fill=\"#e8e3da\" stroke=\"#6b4a8c\" stroke-width=\"2\"\/>\n <g fill=\"#d9d3c7\" stroke=\"#7a756b\" stroke-width=\"0.7\">\n <circle cx=\"210\" cy=\"127\" r=\"5\"\/><circle cx=\"247\" cy=\"131\" r=\"5\"\/><circle cx=\"274\" cy=\"148\" r=\"5\"\/><circle cx=\"289\" cy=\"173\" r=\"5\"\/>\n <circle cx=\"289\" cy=\"200\" r=\"5\"\/><circle cx=\"278\" cy=\"227\" r=\"5\"\/><circle cx=\"256\" cy=\"248\" r=\"5\"\/><circle cx=\"227\" cy=\"259\" r=\"5\"\/>\n <circle cx=\"193\" cy=\"259\" r=\"5\"\/><circle cx=\"164\" cy=\"248\" r=\"5\"\/><circle cx=\"142\" cy=\"227\" r=\"5\"\/><circle cx=\"131\" cy=\"200\" r=\"5\"\/>\n <circle cx=\"131\" cy=\"173\" r=\"5\"\/><circle cx=\"142\" cy=\"148\" r=\"5\"\/><circle cx=\"164\" cy=\"131\" r=\"5\"\/><circle cx=\"185\" cy=\"127\" r=\"5\"\/>\n <\/g>\n <circle cx=\"210\" cy=\"195\" r=\"26\" fill=\"#e8e3da\" stroke=\"#7a756b\" stroke-width=\"2\"\/>\n <text x=\"210\" y=\"34\" fill=\"#2a5a8c\" font-size=\"14\" font-weight=\"700\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">STATOR<\/text>\n <line x1=\"232\" y1=\"64\" x2=\"268\" y2=\"50\" stroke=\"#2a7a7a\" stroke-width=\"1\"\/>\n <text x=\"272\" y=\"50\" fill=\"#2a7a7a\" font-size=\"11\" font-weight=\"600\" font-family=\"Source Sans 3,sans-serif\">Winding slots<\/text>\n <line x1=\"293\" y1=\"135\" x2=\"345\" y2=\"108\" stroke=\"#9a6b12\" stroke-width=\"1.2\"\/>\n <circle cx=\"293\" cy=\"135\" r=\"2.5\" fill=\"#9a6b12\"\/>\n <text x=\"350\" y=\"102\" fill=\"#9a6b12\" font-size=\"13\" font-weight=\"700\" font-family=\"Source Sans 3,sans-serif\">AIR GAP<\/text>\n <text x=\"350\" y=\"118\" fill=\"#9a6b12\" font-size=\"10\" font-family=\"Source Sans 3,sans-serif\">(0.25 \u2013 2 mm typical)<\/text>\n <text x=\"350\" y=\"133\" fill=\"#9a6b12\" font-size=\"10\" font-family=\"Source Sans 3,sans-serif\">(critical parameter)<\/text>\n <text x=\"210\" y=\"188\" fill=\"#3d3b36\" font-size=\"15\" font-weight=\"700\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">ROTOR<\/text>\n <line x1=\"240\" y1=\"260\" x2=\"310\" y2=\"280\" stroke=\"#7a756b\" stroke-width=\"1\"\/>\n <circle cx=\"240\" cy=\"260\" r=\"2.5\" fill=\"#7a756b\"\/>\n <text x=\"315\" y=\"276\" fill=\"#7a756b\" font-size=\"11\" font-weight=\"600\" font-family=\"Source Sans 3,sans-serif\">Rotor bars (shown: 16)<\/text>\n <text x=\"315\" y=\"291\" fill=\"#9e9889\" font-size=\"10\" font-family=\"Source Sans 3,sans-serif\">carry induced current<\/text>\n <text x=\"210\" y=\"200\" fill=\"#7a756b\" font-size=\"10\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">Shaft<\/text>\n <line x1=\"105\" y1=\"170\" x2=\"58\" y2=\"148\" stroke=\"#2a5a8c\" stroke-width=\"1\"\/>\n <circle cx=\"105\" cy=\"170\" r=\"2.5\" fill=\"#2a5a8c\"\/>\n <text x=\"14\" y=\"142\" fill=\"#2a5a8c\" font-size=\"11\" font-weight=\"600\" font-family=\"Source Sans 3,sans-serif\">Stator bore<\/text>\n <text x=\"14\" y=\"156\" fill=\"#9e9889\" font-size=\"9.5\" font-family=\"Source Sans 3,sans-serif\">(laminated core)<\/text>\n \n <g transform=\"translate(405,130)\">\n <rect x=\"0\" y=\"0\" width=\"208\" height=\"222\" rx=\"8\" fill=\"#f0ece5\" stroke=\"#d9d3c7\" stroke-width=\"1.5\"\/>\n <text x=\"104\" y=\"22\" fill=\"#2a5a8c\" font-size=\"13\" font-weight=\"700\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">Key Frequencies<\/text>\n <line x1=\"12\" y1=\"32\" x2=\"196\" y2=\"32\" stroke=\"#d9d3c7\" stroke-width=\"1\"\/>\n <text x=\"18\" y=\"52\" fill=\"#2a5a8c\" font-size=\"11\" font-family=\"Source Sans 3,sans-serif\">\u25b8 Stator \u2192 2\u00d7LF<\/text>\n <text x=\"18\" y=\"72\" fill=\"#9a6b12\" font-size=\"11\" font-family=\"Source Sans 3,sans-serif\">\u25b8 Air gap \u2192 2\u00d7LF \u00b1 1X<\/text>\n <text x=\"18\" y=\"92\" fill=\"#6b4a8c\" font-size=\"11\" font-family=\"Source Sans 3,sans-serif\">\u25b8 Broken bars \u2192 1X \u00b1 Fp<\/text>\n <text x=\"30\" y=\"107\" fill=\"#7a756b\" font-size=\"9.5\" font-family=\"Source Sans 3,sans-serif\">MCSA: LF \u00b1 Fp<\/text>\n <text x=\"18\" y=\"127\" fill=\"#7a756b\" font-size=\"11\" font-family=\"Source Sans 3,sans-serif\">\u25b8 Bar pass \u2192 R \u00d7 frot<\/text>\n <text x=\"18\" y=\"147\" fill=\"#2d6b30\" font-size=\"11\" font-family=\"Source Sans 3,sans-serif\">\u25b8 Mechanical \u2192 1X, 2X, nX<\/text>\n <text x=\"18\" y=\"167\" fill=\"#b8372b\" font-size=\"11\" font-family=\"Source Sans 3,sans-serif\">\u25b8 Axial shift \u2192 2\u00d7LF \u00b1 1X (ax.)<\/text>\n <line x1=\"12\" y1=\"178\" x2=\"196\" y2=\"178\" stroke=\"#d9d3c7\" stroke-width=\"1\"\/>\n <text x=\"18\" y=\"196\" fill=\"#7a756b\" font-size=\"10\" font-family=\"Source Sans 3,sans-serif\">At 50 Hz: 2\u00d7LF = 100 Hz<\/text>\n <text x=\"18\" y=\"212\" fill=\"#9e9889\" font-size=\"9\" font-style=\"italic\" font-family=\"Source Sans 3,sans-serif\">\u00b1 = sidebands (modulation)<\/text>\n <\/g>\n <text x=\"210\" y=\"374\" fill=\"#9e9889\" font-size=\"9.5\" font-style=\"italic\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">Schematic \u2014 not to scale. Actual slot\/bar count depends on motor design.<\/text>\n<\/svg>\n<\/div>\n<p class=\"infographic-note\"><span class=\"legend-blue legend-badge\">Stator<\/span><span class=\"legend-purple legend-badge\">Rotor<\/span><span class=\"legend-teal legend-badge\">Windings<\/span><span class=\"legend-yellow legend-badge\">Air gap<\/span><span class=\"legend-green legend-badge\">Mechanical<\/span><span class=\"legend-red legend-badge\">Axial<\/span> Any air-gap distortion directly changes magnetic pull, and that immediately changes the vibration pattern. Symbol \u00b1 denotes sidebands (modulation).<\/p>\n\n\n\n<h2 id=\"methods\"><span class=\"section-num\">2.<\/span> Overview of Diagnostic Methods<\/h2>\n\n<p>No single technique can detect all electric motor defects. A robust diagnostic program combines multiple complementary methods:<\/p>\n\n\n<div class=\"infographic\">\n<div class=\"infographic-title\">Electric Motor Diagnostic Methods<\/div>\n<svg viewBox=\"0 0 780 320\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" style=\"max-width:100%;\" role=\"img\">\n <rect x=\"0\" y=\"0\" width=\"780\" height=\"320\" rx=\"12\" fill=\"#faf8f5\"\/>\n <circle cx=\"390\" cy=\"160\" r=\"50\" fill=\"#e8e3da\" stroke=\"#2a5a8c\" stroke-width=\"2\"\/>\n <text x=\"390\" y=\"155\" fill=\"#3d3b36\" font-size=\"12\" font-weight=\"600\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">ELECTRIC<\/text>\n <text x=\"390\" y=\"172\" fill=\"#3d3b36\" font-size=\"12\" font-weight=\"600\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">MOTOR<\/text>\n \n <g transform=\"translate(40,30)\">\n <rect x=\"0\" y=\"0\" width=\"175\" height=\"90\" rx=\"8\" fill=\"var(--card)\" stroke=\"#2a5a8c\" stroke-width=\"1.5\"\/>\n <text x=\"88\" y=\"22\" fill=\"#2a5a8c\" font-size=\"12\" font-weight=\"600\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">1. Vibration Analysis<\/text>\n <text x=\"88\" y=\"40\" fill=\"#7a756b\" font-size=\"9.5\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">Spectra & time waveform<\/text>\n <text x=\"88\" y=\"55\" fill=\"#7a756b\" font-size=\"9.5\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">1X, 2X, 2\u00d7LF, harmonics<\/text>\n <text x=\"88\" y=\"70\" fill=\"#2d6b30\" font-size=\"9.5\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">\u2713 Mechanical + some electrical<\/text>\n <text x=\"88\" y=\"84\" fill=\"#b8372b\" font-size=\"9\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">\u2717 Cannot detect all electrical faults<\/text>\n <\/g>\n <line x1=\"215\" y1=\"90\" x2=\"345\" y2=\"140\" stroke=\"#2a5a8c\" stroke-width=\"1\" stroke-dasharray=\"4,3\"\/>\n \n <g transform=\"translate(40,190)\">\n <rect x=\"0\" y=\"0\" width=\"175\" height=\"90\" rx=\"8\" fill=\"var(--card)\" stroke=\"#9a6b12\" stroke-width=\"1.5\"\/>\n <text x=\"88\" y=\"22\" fill=\"#9a6b12\" font-size=\"12\" font-weight=\"600\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">2. MCSA<\/text>\n <text x=\"88\" y=\"38\" fill=\"#7a756b\" font-size=\"9.5\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">Motor Current Signature<\/text>\n <text x=\"88\" y=\"53\" fill=\"#7a756b\" font-size=\"9.5\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">Analysis \u2014 current clamp<\/text>\n <text x=\"88\" y=\"70\" fill=\"#2d6b30\" font-size=\"9.5\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">\u2713 Broken rotor bars, eccentricity<\/text>\n <text x=\"88\" y=\"84\" fill=\"#2d6b30\" font-size=\"9\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">\u2713 Online, non-invasive<\/text>\n <\/g>\n <line x1=\"215\" y1=\"240\" x2=\"345\" y2=\"180\" stroke=\"#9a6b12\" stroke-width=\"1\" stroke-dasharray=\"4,3\"\/>\n \n <g transform=\"translate(560,30)\">\n <rect x=\"0\" y=\"0\" width=\"175\" height=\"90\" rx=\"8\" fill=\"var(--card)\" stroke=\"#2d6b30\" stroke-width=\"1.5\"\/>\n <text x=\"88\" y=\"22\" fill=\"#2d6b30\" font-size=\"12\" font-weight=\"600\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">3. ESA<\/text>\n <text x=\"88\" y=\"38\" fill=\"#7a756b\" font-size=\"9.5\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">Electrical Signature Analysis<\/text>\n <text x=\"88\" y=\"53\" fill=\"#7a756b\" font-size=\"9.5\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">Voltage + current spectra<\/text>\n <text x=\"88\" y=\"70\" fill=\"#2d6b30\" font-size=\"9.5\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">\u2713 Supply quality, stator faults<\/text>\n <text x=\"88\" y=\"84\" fill=\"#2d6b30\" font-size=\"9\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">\u2713 Online, at MCC<\/text>\n <\/g>\n <line x1=\"560\" y1=\"90\" x2=\"435\" y2=\"140\" stroke=\"#2d6b30\" stroke-width=\"1\" stroke-dasharray=\"4,3\"\/>\n \n <g transform=\"translate(560,190)\">\n <rect x=\"0\" y=\"0\" width=\"175\" height=\"90\" rx=\"8\" fill=\"var(--card)\" stroke=\"#6b4a8c\" stroke-width=\"1.5\"\/>\n <text x=\"88\" y=\"22\" fill=\"#6b4a8c\" font-size=\"12\" font-weight=\"600\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">4. MCA<\/text>\n <text x=\"88\" y=\"38\" fill=\"#7a756b\" font-size=\"9.5\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">Motor Circuit Analysis<\/text>\n <text x=\"88\" y=\"53\" fill=\"#7a756b\" font-size=\"9.5\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">Impedance, resistance<\/text>\n <text x=\"88\" y=\"70\" fill=\"#2d6b30\" font-size=\"9.5\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">\u2713 Insulation, turn-to-turn shorts<\/text>\n <text x=\"88\" y=\"84\" fill=\"#b8372b\" font-size=\"9\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">\u2717 Offline only (motor stopped)<\/text>\n <\/g>\n <line x1=\"560\" y1=\"240\" x2=\"435\" y2=\"180\" stroke=\"#6b4a8c\" stroke-width=\"1\" stroke-dasharray=\"4,3\"\/>\n \n <g transform=\"translate(303,265)\">\n <rect x=\"0\" y=\"0\" width=\"175\" height=\"48\" rx=\"8\" fill=\"var(--card)\" stroke=\"#b8372b\" stroke-width=\"1.5\"\/>\n <text x=\"88\" y=\"20\" fill=\"#b8372b\" font-size=\"12\" font-weight=\"600\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">5. Thermography<\/text>\n <text x=\"88\" y=\"38\" fill=\"#7a756b\" font-size=\"9.5\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">Stator temp + bearing temp monitoring<\/text>\n <\/g>\n <line x1=\"390\" y1=\"210\" x2=\"390\" y2=\"265\" stroke=\"#b8372b\" stroke-width=\"1\" stroke-dasharray=\"4,3\"\/>\n<\/svg>\n<\/div>\n<p class=\"infographic-note\"><span class=\"legend-blue legend-badge\">Vibration<\/span><span class=\"legend-yellow legend-badge\">MCSA<\/span><span class=\"legend-green legend-badge\">ESA<\/span><span class=\"legend-purple legend-badge\">MCA<\/span><span class=\"legend-red legend-badge\">Thermography<\/span> No single method gives full coverage. A combined diagnostic approach is strongly recommended.<\/p>\n\n<h3>2.1. Vibration Spectral Analysis<\/h3>\n<p>The primary tool for most rotating equipment diagnostics. Accelerometers on bearing housings capture spectra revealing mechanical defects (unbalance, misalignment, bearing wear) and some electrical defects (uneven air gap, loose windings). However, <strong>vibration analysis alone cannot detect all motor electrical faults<\/strong>.<\/p>\n\n<h3>2.2. Motor Current Signature Analysis (MCSA)<\/h3>\n<p>A current clamp on one phase captures the current spectrum. Broken rotor bars produce sidebands at <code>LF \u00b1 F<sub>p<\/sub><\/code>. MCSA is performed online and is completely non-invasive.<\/p>\n\n<h3>2.3. Electrical Signature Analysis (ESA)<\/h3>\n<p>Analyzes both voltage and current spectra simultaneously at the MCC. Detects supply voltage asymmetry, harmonic distortion, and power quality issues.<\/p>\n\n<h3>2.4. Motor Circuit Analysis (MCA)<\/h3>\n<p>An <strong>offline<\/strong> test measuring phase-to-phase resistance, inductance, impedance, and insulation resistance. Essential during maintenance shutdowns.<\/p>\n\n<h3>2.5. Temperature Monitoring<\/h3>\n<p>Stator winding temperature and bearing temperature trending provide early warning of overload, cooling problems, and insulation degradation.<\/p>\n\n<div class=\"tip\">\n<p><strong>Practical approach.<\/strong> For a comprehensive motor diagnostic program, combine at minimum: (1) vibration spectral analysis, (2) MCSA with current clamp, and (3) regular conversations with electricians and motor repair personnel \u2014 their hands-on experience often reveals critical context that instruments alone cannot provide.<\/p>\n<\/div>\n\n\n\n<h2 id=\"stator\"><span class=\"section-num\">3.<\/span> Stator Defects<\/h2>\n\n<p>Stator defects are responsible for approximately <strong>23\u201337% of all motor failures<\/strong>. The stator is the stationary part containing the laminated iron core and windings. Defects produce vibration primarily at <strong>2\u00d7LF (100 Hz \/ 120 Hz)<\/strong> and its multiples.<\/p>\n\n<h3 id=\"stator-eccentricity\">3.1. Stator Eccentricity \u2014 Uneven Air Gap<\/h3>\n\n<p>The air gap between rotor and stator is typically <strong>0.25\u20132 mm<\/strong>. Even a 10% variation creates measurable electromagnetic force imbalance.<\/p>\n\n<h4>Causes<\/h4>\n<ul>\n <li><strong>Soft foot<\/strong> \u2014 the most common cause<\/li>\n <li>Worn or damaged bearing housings<\/li>\n <li>Frame deformation from improper transport or installation<\/li>\n <li>Thermal distortion under operating conditions<\/li>\n <li>Poor manufacturing tolerances<\/li>\n<\/ul>\n\n<h4>Spectral Signature<\/h4>\n<ul>\n <li><strong>Typically dominant 2\u00d7LF<\/strong> in the radial velocity spectrum<\/li>\n <li>Often accompanied by minor increase of <strong>1X<\/strong> and <strong>2X<\/strong> due to unbalanced magnetic pull (UMP)<\/li>\n <li>Static eccentricity: 2\u00d7LF dominates with little modulation<\/li>\n <li>Dynamic component: sidebands at <strong>2\u00d7LF \u00b1 1X<\/strong> may appear<\/li>\n<\/ul>\n\n<div class=\"formula\">Spectrum: prominent <strong>2\u00d7LF<\/strong> + minor <strong>1X<\/strong> and <strong>2X<\/strong> increase (radial direction)<\/div>\n\n<h4>Severity Assessment<\/h4>\n<div class=\"table-wrap\">\n<table>\n<thead><tr><th>2\u00d7LF amplitude (velocity RMS)<\/th><th>Assessment<\/th><\/tr><\/thead>\n<tbody>\n<tr><td>< 1 mm\/s<\/td><td>Normal for most motors<\/td><\/tr>\n<tr><td>1\u20133 mm\/s<\/td><td>Monitor \u2014 check soft foot, bearing clearance<\/td><\/tr>\n<tr><td>3\u20136 mm\/s<\/td><td>Alert \u2014 investigate and plan correction<\/td><\/tr>\n<tr><td>> 6 mm\/s<\/td><td>Danger \u2014 immediate action required<\/td><\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<p><em>Note: These are illustrative guidelines, not a formal standard. Always compare against the machine's own baseline.<\/em><\/p>\n\n<h4>Confirmation Test<\/h4>\n<p><strong>Power-off test<\/strong> (snap test): While monitoring vibration, de-energize the motor. If the 2\u00d7LF peak <strong>drops sharply<\/strong> \u2014 within seconds, much faster than mechanical coastdown \u2014 the source is electromagnetic.<\/p>\n\n<div class=\"key-fact warn\">\n <div class=\"key-fact-label\">Important<\/div>\n <p>Do not confuse stator eccentricity with misalignment. Both can produce elevated 2X. The key: 2\u00d7LF at exactly 100.00 Hz is electrical; 2X tracks rotor speed and shifts if speed changes. Ensure spectral resolution \u2264 0.5 Hz.<\/p>\n<\/div>\n\n\n<h3 id=\"loose-windings\">3.2. Loose Stator Windings<\/h3>\n\n<p>Stator windings are subjected to electromagnetic forces at 2\u00d7LF during every operating cycle. Over years, mechanical fixation (epoxy, varnish, wedges) can degrade. Loose windings vibrate at 2\u00d7LF with increasing amplitude, accelerating insulation wear through fretting.<\/p>\n\n<h4>Spectral Signature<\/h4>\n<div class=\"formula\">Elevated <strong>2\u00d7LF<\/strong> \u2014 often with increase over time (trending)<\/div>\n<ul>\n <li>Predominantly radial vibration<\/li>\n <li>2\u00d7LF may be less stable \u2014 slight amplitude fluctuations<\/li>\n <li>Severe cases: harmonics at 4\u00d7LF, 6\u00d7LF<\/li>\n<\/ul>\n\n<h4>Consequences<\/h4>\n<p>This is <strong>destructive for winding insulation<\/strong> \u2014 leads to accelerated degradation, unpredictable ground faults, and complete stator failure requiring rewind.<\/p>\n\n\n<h3 id=\"loose-cable\">3.3. Loose Power Cable \u2014 Phase Asymmetry<\/h3>\n\n<p>A poor contact creates resistance asymmetry. Even <strong>1% voltage asymmetry<\/strong> causes approximately <strong>6\u201310% current asymmetry<\/strong>. The unbalanced currents create a backward-rotating magnetic field component.<\/p>\n\n<h4>Spectral Signature<\/h4>\n<div class=\"formula\">Elevated <strong>2\u00d7LF<\/strong> \u2014 primary indicator of phase asymmetry<\/div>\n<ul>\n <li>2\u00d7LF amplitude increases due to unbalanced magnetic pull<\/li>\n <li>In some cases, <strong>sidebands near \u00b1\u2153\u00d7LF<\/strong> (~16.7 Hz in 50 Hz systems) around the 2\u00d7LF peak<\/li>\n <li>In current spectrum (MCSA): elevated negative-sequence current<\/li>\n<\/ul>\n\n<h4>Practical Checks<\/h4>\n<ul>\n <li>Check all cable terminations, bus bar connections, contactor contacts<\/li>\n <li>Measure phase-to-phase resistance \u2014 within 1% of each other<\/li>\n <li>Measure supply voltage on all three phases \u2014 asymmetry should not exceed 1%<\/li>\n <li>IR thermography of cable termination box<\/li>\n<\/ul>\n\n\n<h3 id=\"shorted-laminations\">3.4. Shorted Stator Laminations<\/h3>\n\n<p>Damage to inter-lamination insulation allows eddy currents to circulate, creating localized hot spots. Not always detectable in vibration spectra \u2014 <strong>IR thermography is the primary detection method<\/strong>. Offline: electromagnetic core test (EL-CID test).<\/p>\n\n\n<h3 id=\"inter-turn\">3.5. Inter-Turn Short Circuit<\/h3>\n\n<p>A turn-to-turn short creates a localized circulating current loop, reducing effective turns in the affected coil. Produces increased <strong>2\u00d7LF<\/strong>, elevated 3rd harmonic of LF in current, and phase current asymmetry. Best detected via MCA surge test offline.<\/p>\n\n\n<div class=\"infographic\">\n<div class=\"infographic-title\">Stator Defects \u2014 Spectral Signatures Summary<\/div>\n<svg viewBox=\"0 0 820 480\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" style=\"max-width:100%;\" role=\"img\">\n <rect x=\"0\" y=\"0\" width=\"820\" height=\"480\" rx=\"12\" fill=\"#faf8f5\"\/>\n \n <g transform=\"translate(580,14)\">\n <rect x=\"0\" y=\"0\" width=\"220\" height=\"76\" rx=\"6\" fill=\"#f0ece5\" stroke=\"#d9d3c7\" stroke-width=\"1.5\"\/>\n <text x=\"110\" y=\"18\" fill=\"#2a5a8c\" font-size=\"12\" font-weight=\"700\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">Legend<\/text>\n <line x1=\"10\" y1=\"25\" x2=\"210\" y2=\"25\" stroke=\"#d9d3c7\" stroke-width=\"1\"\/>\n <rect x=\"14\" y=\"34\" width=\"16\" height=\"10\" rx=\"2\" fill=\"#b8372b\"\/><text x=\"36\" y=\"44\" fill=\"#3d3b36\" font-size=\"11\" font-family=\"Source Sans 3,sans-serif\">2\u00d7LF peak (100 Hz) \u2014 electrical<\/text>\n <rect x=\"14\" y=\"50\" width=\"16\" height=\"10\" rx=\"2\" fill=\"#2d6b30\"\/><text x=\"36\" y=\"60\" fill=\"#3d3b36\" font-size=\"11\" font-family=\"Source Sans 3,sans-serif\">1X \/ 2X peaks \u2014 mechanical<\/text>\n <rect x=\"14\" y=\"66\" width=\"16\" height=\"10\" rx=\"2\" fill=\"#9a6b12\"\/><text x=\"36\" y=\"76\" fill=\"#3d3b36\" font-size=\"11\" font-family=\"Source Sans 3,sans-serif\">Sidebands (modulation)<\/text>\n <\/g>\n\n \n <text x=\"40\" y=\"30\" fill=\"#2a5a8c\" font-size=\"14\" font-weight=\"700\" font-family=\"Source Sans 3,sans-serif\">A. Stator eccentricity \/ Uneven air gap (\u00a73.1)<\/text>\n <text x=\"22\" y=\"138\" fill=\"#7a756b\" font-size=\"10\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\" transform=\"rotate(-90 22 138)\">Amplitude<\/text>\n <line x1=\"55\" y1=\"210\" x2=\"555\" y2=\"210\" stroke=\"#d9d3c7\" stroke-width=\"1.5\"\/>\n <line x1=\"55\" y1=\"45\" x2=\"55\" y2=\"210\" stroke=\"#d9d3c7\" stroke-width=\"1\"\/>\n <line x1=\"56\" y1=\"205\" x2=\"554\" y2=\"205\" stroke=\"#e8e3da\" stroke-width=\"1\" stroke-dasharray=\"2,4\"\/>\n \n <rect x=\"143\" y=\"168\" width=\"6\" height=\"37\" rx=\"2\" fill=\"#2d6b30\" opacity=\"0.8\"\/>\n <text x=\"146\" y=\"162\" fill=\"#2d6b30\" font-size=\"11\" font-weight=\"600\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">1X<\/text>\n \n <rect x=\"333\" y=\"156\" width=\"6\" height=\"49\" rx=\"2\" fill=\"#2d6b30\" opacity=\"0.8\"\/>\n <text x=\"336\" y=\"148\" fill=\"#2d6b30\" font-size=\"11\" font-weight=\"600\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">2X<\/text>\n \n <rect x=\"355\" y=\"52\" width=\"8\" height=\"153\" rx=\"2\" fill=\"#b8372b\" opacity=\"0.95\"\/>\n <text x=\"359\" y=\"46\" fill=\"#b8372b\" font-size=\"12\" font-weight=\"700\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">2\u00d7LF<\/text>\n \n <line x1=\"146\" y1=\"210\" x2=\"146\" y2=\"217\" stroke=\"#7a756b\" stroke-width=\"1\"\/><text x=\"146\" y=\"230\" fill=\"#7a756b\" font-size=\"10\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">49 Hz<\/text>\n <line x1=\"336\" y1=\"210\" x2=\"336\" y2=\"217\" stroke=\"#7a756b\" stroke-width=\"1\"\/><text x=\"326\" y=\"230\" fill=\"#7a756b\" font-size=\"10\" text-anchor=\"end\" font-family=\"Source Sans 3,sans-serif\">98<\/text>\n <line x1=\"359\" y1=\"210\" x2=\"359\" y2=\"217\" stroke=\"#7a756b\" stroke-width=\"1\"\/><text x=\"370\" y=\"230\" fill=\"#b8372b\" font-size=\"10\" font-family=\"Source Sans 3,sans-serif\">100 Hz<\/text>\n \n <line x1=\"339\" y1=\"240\" x2=\"356\" y2=\"240\" stroke=\"#7a756b\" stroke-width=\"1\"\/>\n <line x1=\"339\" y1=\"237\" x2=\"339\" y2=\"243\" stroke=\"#7a756b\" stroke-width=\"1\"\/>\n <line x1=\"356\" y1=\"237\" x2=\"356\" y2=\"243\" stroke=\"#7a756b\" stroke-width=\"1\"\/>\n <text x=\"348\" y=\"254\" fill=\"#7a756b\" font-size=\"9\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">2 Hz gap!<\/text>\n <text x=\"348\" y=\"266\" fill=\"#9e9889\" font-size=\"8.5\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">(need \u22640.5 Hz res.)<\/text>\n \n <line x1=\"380\" y1=\"72\" x2=\"430\" y2=\"62\" stroke=\"#b8372b\" stroke-width=\"1\"\/>\n <text x=\"435\" y=\"60\" fill=\"#b8372b\" font-size=\"11\" font-weight=\"600\" font-family=\"Source Sans 3,sans-serif\">2\u00d7LF DOMINANT<\/text>\n <text x=\"435\" y=\"76\" fill=\"#7a756b\" font-size=\"10\" font-family=\"Source Sans 3,sans-serif\">Radial direction<\/text>\n <text x=\"435\" y=\"92\" fill=\"#7a756b\" font-size=\"10\" font-family=\"Source Sans 3,sans-serif\">Vanishes on power-off<\/text>\n\n \n <line x1=\"20\" y1=\"280\" x2=\"800\" y2=\"280\" stroke=\"#d9d3c7\" stroke-width=\"1\" stroke-dasharray=\"4,4\"\/>\n <text x=\"40\" y=\"306\" fill=\"#9a6b12\" font-size=\"14\" font-weight=\"700\" font-family=\"Source Sans 3,sans-serif\">B. Loose power cable \/ Phase asymmetry (\u00a73.3)<\/text>\n <text x=\"22\" y=\"396\" fill=\"#7a756b\" font-size=\"10\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\" transform=\"rotate(-90 22 396)\">Amplitude<\/text>\n <line x1=\"55\" y1=\"450\" x2=\"730\" y2=\"450\" stroke=\"#d9d3c7\" stroke-width=\"1.5\"\/>\n <line x1=\"55\" y1=\"310\" x2=\"55\" y2=\"450\" stroke=\"#d9d3c7\" stroke-width=\"1\"\/>\n <line x1=\"56\" y1=\"445\" x2=\"729\" y2=\"445\" stroke=\"#e8e3da\" stroke-width=\"1\" stroke-dasharray=\"2,4\"\/>\n \n <rect x=\"253\" y=\"375\" width=\"6\" height=\"70\" rx=\"2\" fill=\"#9a6b12\" opacity=\"0.85\"\/>\n <text x=\"256\" y=\"368\" fill=\"#9a6b12\" font-size=\"11\" font-weight=\"600\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">83 Hz<\/text>\n \n <rect x=\"356\" y=\"318\" width=\"8\" height=\"127\" rx=\"2\" fill=\"#b8372b\" opacity=\"0.95\"\/>\n <text x=\"360\" y=\"312\" fill=\"#b8372b\" font-size=\"12\" font-weight=\"700\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">2\u00d7LF<\/text>\n \n <rect x=\"460\" y=\"375\" width=\"6\" height=\"70\" rx=\"2\" fill=\"#9a6b12\" opacity=\"0.85\"\/>\n <text x=\"463\" y=\"368\" fill=\"#9a6b12\" font-size=\"11\" font-weight=\"600\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">117 Hz<\/text>\n \n <path d=\"M256,363 L256,352 L360,340 L463,352 L463,363\" stroke=\"#9a6b12\" stroke-width=\"1.2\" fill=\"none\"\/>\n <text x=\"310\" y=\"347\" fill=\"#9a6b12\" font-size=\"10\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">\u2212\u2153LF<\/text>\n <text x=\"415\" y=\"347\" fill=\"#9a6b12\" font-size=\"10\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">+\u2153LF<\/text>\n <text x=\"360\" y=\"336\" fill=\"#9a6b12\" font-size=\"11\" font-weight=\"600\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">\u00b1 \u2153\u00d7LF sidebands (16.7 Hz)<\/text>\n \n <line x1=\"256\" y1=\"450\" x2=\"256\" y2=\"457\" stroke=\"#7a756b\" stroke-width=\"1\"\/><text x=\"256\" y=\"470\" fill=\"#7a756b\" font-size=\"10\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">83 Hz<\/text>\n <line x1=\"360\" y1=\"450\" x2=\"360\" y2=\"457\" stroke=\"#7a756b\" stroke-width=\"1\"\/><text x=\"360\" y=\"470\" fill=\"#b8372b\" font-size=\"10\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">100 Hz (2\u00d7LF)<\/text>\n <line x1=\"463\" y1=\"450\" x2=\"463\" y2=\"457\" stroke=\"#7a756b\" stroke-width=\"1\"\/><text x=\"463\" y=\"470\" fill=\"#7a756b\" font-size=\"10\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">117 Hz<\/text>\n \n <line x1=\"378\" y1=\"338\" x2=\"520\" y2=\"328\" stroke=\"#b8372b\" stroke-width=\"1\"\/>\n <text x=\"525\" y=\"326\" fill=\"#b8372b\" font-size=\"11\" font-weight=\"600\" font-family=\"Source Sans 3,sans-serif\">2\u00d7LF elevated<\/text>\n <text x=\"525\" y=\"342\" fill=\"#7a756b\" font-size=\"10\" font-family=\"Source Sans 3,sans-serif\">Phase resistance asymmetry<\/text>\n <text x=\"525\" y=\"358\" fill=\"#7a756b\" font-size=\"10\" font-family=\"Source Sans 3,sans-serif\">causes backward-rotating field<\/text>\n <line x1=\"260\" y1=\"400\" x2=\"120\" y2=\"400\" stroke=\"#9a6b12\" stroke-width=\"1\"\/>\n <text x=\"62\" y=\"396\" fill=\"#9a6b12\" font-size=\"10\" font-weight=\"600\" font-family=\"Source Sans 3,sans-serif\">Check:<\/text>\n <text x=\"62\" y=\"412\" fill=\"#7a756b\" font-size=\"10\" font-family=\"Source Sans 3,sans-serif\">\u2022 Cable terminations<\/text>\n <text x=\"62\" y=\"426\" fill=\"#7a756b\" font-size=\"10\" font-family=\"Source Sans 3,sans-serif\">\u2022 Phase-to-phase R<\/text>\n <text x=\"62\" y=\"440\" fill=\"#7a756b\" font-size=\"10\" font-family=\"Source Sans 3,sans-serif\">\u2022 IR thermography<\/text>\n<\/svg>\n<\/div>\n<p class=\"infographic-note\"><span class=\"legend-red legend-badge\">2\u00d7LF<\/span><span class=\"legend-green legend-badge\">1X \/ 2X<\/span><span class=\"legend-yellow legend-badge\">Sidebands<\/span> The power-off test confirms electromagnetic origin: if 2\u00d7LF drops sharply upon de-energization (much faster than coastdown), the source is electromagnetic.<\/p>\n\n\n\n<h2 id=\"rotor\"><span class=\"section-num\">4.<\/span> Rotor Defects<\/h2>\n\n<p>Rotor defects account for approximately <strong>5\u201310% of motor failures<\/strong> but are often the most challenging to detect early.<\/p>\n\n<h3 id=\"broken-bars\">4.1. Broken Rotor Bars and Cracked End Rings<\/h3>\n\n<p>When a bar breaks, current redistribution creates local magnetic asymmetry \u2014 effectively a \"magnetic heavy spot\" that rotates at slip frequency relative to the stator field.<\/p>\n\n<h4>Vibration Signature<\/h4>\n<ul>\n <li><strong>1X<\/strong> peak with <strong>sidebands at \u00b1 F<sub>p<\/sub><\/strong>. For 50 Hz \/ 2% slip: sidebands at 1X \u00b1 2 Hz<\/li>\n <li>Severe cases: additional sidebands at \u00b1 2F<sub>p<\/sub>, \u00b1 3F<sub>p<\/sub><\/li>\n <li><strong>2\u00d7LF<\/strong> may also show F<sub>p<\/sub> sidebands<\/li>\n<\/ul>\n\n<h4>MCSA Signature<\/h4>\n<div class=\"formula\">Current spectrum: <strong>LF \u00b1 F<sub>p<\/sub><\/strong> (50 \u00b1 2 Hz = 48 Hz and 52 Hz)<\/div>\n\n<h4>MCSA Severity Scale<\/h4>\n<div class=\"table-wrap\">\n<table>\n<thead><tr><th>Sideband level vs LF peak<\/th><th>Assessment<\/th><\/tr><\/thead>\n<tbody>\n<tr><td><strong>< \u221254 dB<\/strong><\/td><td>Generally healthy rotor<\/td><\/tr>\n<tr><td><strong>\u221254 to \u221248 dB<\/strong><\/td><td>May indicate 1\u20132 cracked bars \u2014 monitor trend<\/td><\/tr>\n<tr><td><strong>\u221248 to \u221240 dB<\/strong><\/td><td>Likely multiple broken bars \u2014 plan inspection<\/td><\/tr>\n<tr><td><strong>> \u221240 dB<\/strong><\/td><td>Severe damage \u2014 risk of secondary failures<\/td><\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<p><em>Important: MCSA requires steady load near rated conditions. At partial load, sideband amplitude drops.<\/em><\/p>\n\n<h4>Time Waveform<\/h4>\n<p>Broken rotor bars produce a characteristic <strong>\"beating\" pattern<\/strong> \u2014 amplitude modulates at the pole pass frequency. Often visible before spectral sidebands become prominent.<\/p>\n\n\n<div class=\"infographic\">\n<div class=\"infographic-title\">Broken Rotor Bars \u2014 Vibration and Current Spectral Patterns<\/div>\n<svg viewBox=\"0 0 840 500\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" style=\"max-width:100%;\" role=\"img\">\n <rect x=\"0\" y=\"0\" width=\"840\" height=\"500\" rx=\"12\" fill=\"#faf8f5\"\/>\n \n <text x=\"215\" y=\"28\" fill=\"#2a5a8c\" font-size=\"15\" font-weight=\"700\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">Vibration Spectrum<\/text>\n <text x=\"215\" y=\"46\" fill=\"#7a756b\" font-size=\"10\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">(velocity, radial direction)<\/text>\n <text x=\"26\" y=\"140\" fill=\"#7a756b\" font-size=\"10\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\" transform=\"rotate(-90 26 140)\">Amplitude<\/text>\n <line x1=\"50\" y1=\"55\" x2=\"50\" y2=\"215\" stroke=\"#d9d3c7\" stroke-width=\"1\"\/>\n <line x1=\"50\" y1=\"215\" x2=\"420\" y2=\"215\" stroke=\"#d9d3c7\" stroke-width=\"1.5\"\/>\n <line x1=\"51\" y1=\"210\" x2=\"419\" y2=\"210\" stroke=\"#e8e3da\" stroke-width=\"1\" stroke-dasharray=\"2,4\"\/>\n \n <rect x=\"124\" y=\"165\" width=\"5\" height=\"45\" rx=\"2\" fill=\"#9a6b12\" opacity=\"0.55\"\/>\n <rect x=\"160\" y=\"122\" width=\"6\" height=\"88\" rx=\"2\" fill=\"#9a6b12\" opacity=\"0.85\"\/>\n <rect x=\"197\" y=\"62\" width=\"8\" height=\"148\" rx=\"2\" fill=\"#2a5a8c\"\/>\n <rect x=\"236\" y=\"122\" width=\"6\" height=\"88\" rx=\"2\" fill=\"#9a6b12\" opacity=\"0.85\"\/>\n <rect x=\"272\" y=\"165\" width=\"5\" height=\"45\" rx=\"2\" fill=\"#9a6b12\" opacity=\"0.55\"\/>\n \n <line x1=\"127\" y1=\"215\" x2=\"127\" y2=\"222\" stroke=\"#7a756b\" stroke-width=\"1\"\/><text x=\"127\" y=\"236\" fill=\"#9a6b12\" font-size=\"9\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">\u22122Fp<\/text>\n <line x1=\"163\" y1=\"215\" x2=\"163\" y2=\"222\" stroke=\"#7a756b\" stroke-width=\"1\"\/><text x=\"163\" y=\"236\" fill=\"#9a6b12\" font-size=\"10\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">1X\u2212Fp<\/text>\n <line x1=\"201\" y1=\"215\" x2=\"201\" y2=\"222\" stroke=\"#7a756b\" stroke-width=\"1\"\/><text x=\"201\" y=\"236\" fill=\"#2a5a8c\" font-size=\"11\" font-weight=\"700\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">1X<\/text>\n <line x1=\"239\" y1=\"215\" x2=\"239\" y2=\"222\" stroke=\"#7a756b\" stroke-width=\"1\"\/><text x=\"239\" y=\"236\" fill=\"#9a6b12\" font-size=\"10\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">1X+Fp<\/text>\n <line x1=\"275\" y1=\"215\" x2=\"275\" y2=\"222\" stroke=\"#7a756b\" stroke-width=\"1\"\/><text x=\"275\" y=\"236\" fill=\"#9a6b12\" font-size=\"9\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">+2Fp<\/text>\n \n <path d=\"M163,118 L163,100 L201,88 L239,100 L239,118\" stroke=\"#9a6b12\" stroke-width=\"1.2\" fill=\"none\"\/>\n <text x=\"201\" y=\"82\" fill=\"#9a6b12\" font-size=\"11\" font-weight=\"600\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">\u00b1 Fp (pole pass frequency)<\/text>\n \n <g transform=\"translate(440,58)\">\n <rect x=\"0\" y=\"0\" width=\"220\" height=\"100\" rx=\"6\" fill=\"#f0ece5\" stroke=\"#d9d3c7\" stroke-width=\"1.5\"\/>\n <text x=\"110\" y=\"20\" fill=\"#2a5a8c\" font-size=\"12\" font-weight=\"700\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">Vibration pattern<\/text>\n <line x1=\"10\" y1=\"28\" x2=\"210\" y2=\"28\" stroke=\"#d9d3c7\" stroke-width=\"1\"\/>\n <text x=\"15\" y=\"46\" fill=\"#3d3b36\" font-size=\"10\" font-family=\"Source Sans 3,sans-serif\">\u2022 1X = carrier (rotational freq.)<\/text>\n <text x=\"15\" y=\"63\" fill=\"#9a6b12\" font-size=\"10\" font-family=\"Source Sans 3,sans-serif\">\u2022 \u00b1Fp sidebands = rotor asymmetry<\/text>\n <text x=\"15\" y=\"80\" fill=\"#7a756b\" font-size=\"10\" font-family=\"Source Sans 3,sans-serif\">\u2022 More sidebands = more bars<\/text>\n <text x=\"15\" y=\"96\" fill=\"#7a756b\" font-size=\"10\" font-family=\"Source Sans 3,sans-serif\">\u2022 \"Beating\" in time waveform<\/text>\n <\/g>\n <g transform=\"translate(440,172)\">\n <rect x=\"0\" y=\"0\" width=\"220\" height=\"62\" rx=\"6\" fill=\"#f0ece5\" stroke=\"#d9d3c7\" stroke-width=\"1\"\/>\n <text x=\"110\" y=\"18\" fill=\"#7a756b\" font-size=\"10\" font-weight=\"600\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">Example: 50 Hz, 2-pole, 2% slip<\/text>\n <text x=\"15\" y=\"36\" fill=\"#3d3b36\" font-size=\"10\" font-family=\"Source Sans 3,sans-serif\">1X = 49 Hz, Fp = 2 Hz<\/text>\n <text x=\"15\" y=\"52\" fill=\"#3d3b36\" font-size=\"10\" font-family=\"Source Sans 3,sans-serif\">Sidebands: 47 Hz and 51 Hz<\/text>\n <\/g>\n\n \n <line x1=\"20\" y1=\"260\" x2=\"820\" y2=\"260\" stroke=\"#d9d3c7\" stroke-width=\"1.5\" stroke-dasharray=\"6,4\"\/>\n\n \n <text x=\"215\" y=\"290\" fill=\"#2d6b30\" font-size=\"15\" font-weight=\"700\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">Current Spectrum (MCSA)<\/text>\n <text x=\"215\" y=\"308\" fill=\"#7a756b\" font-size=\"10\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">(motor supply current via clamp)<\/text>\n <text x=\"26\" y=\"395\" fill=\"#7a756b\" font-size=\"10\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\" transform=\"rotate(-90 26 395)\">Amplitude (dB)<\/text>\n <line x1=\"50\" y1=\"316\" x2=\"50\" y2=\"460\" stroke=\"#d9d3c7\" stroke-width=\"1\"\/>\n <line x1=\"50\" y1=\"460\" x2=\"420\" y2=\"460\" stroke=\"#d9d3c7\" stroke-width=\"1.5\"\/>\n <line x1=\"51\" y1=\"455\" x2=\"419\" y2=\"455\" stroke=\"#e8e3da\" stroke-width=\"1\" stroke-dasharray=\"2,4\"\/>\n \n <rect x=\"150\" y=\"378\" width=\"6\" height=\"77\" rx=\"2\" fill=\"#b8372b\" opacity=\"0.9\"\/>\n <rect x=\"200\" y=\"322\" width=\"8\" height=\"133\" rx=\"2\" fill=\"#2d6b30\"\/>\n <rect x=\"250\" y=\"378\" width=\"6\" height=\"77\" rx=\"2\" fill=\"#b8372b\" opacity=\"0.9\"\/>\n \n <line x1=\"153\" y1=\"460\" x2=\"153\" y2=\"467\" stroke=\"#7a756b\" stroke-width=\"1\"\/><text x=\"153\" y=\"480\" fill=\"#b8372b\" font-size=\"11\" font-weight=\"600\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">48 Hz<\/text><text x=\"153\" y=\"493\" fill=\"#b8372b\" font-size=\"9\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">LF \u2212 Fp<\/text>\n <line x1=\"204\" y1=\"460\" x2=\"204\" y2=\"467\" stroke=\"#7a756b\" stroke-width=\"1\"\/><text x=\"204\" y=\"480\" fill=\"#2d6b30\" font-size=\"12\" font-weight=\"700\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">50 Hz<\/text><text x=\"204\" y=\"493\" fill=\"#2d6b30\" font-size=\"9\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">LF<\/text>\n <line x1=\"253\" y1=\"460\" x2=\"253\" y2=\"467\" stroke=\"#7a756b\" stroke-width=\"1\"\/><text x=\"253\" y=\"480\" fill=\"#b8372b\" font-size=\"11\" font-weight=\"600\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">52 Hz<\/text><text x=\"253\" y=\"493\" fill=\"#b8372b\" font-size=\"9\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">LF + Fp<\/text>\n \n <path d=\"M153,373 L153,360 L204,348 L253,360 L253,373\" stroke=\"#b8372b\" stroke-width=\"1.2\" fill=\"none\"\/>\n <text x=\"204\" y=\"342\" fill=\"#b8372b\" font-size=\"11\" font-weight=\"600\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">\u00b1 Fp = \u00b1 2 Hz sidebands<\/text>\n \n <g transform=\"translate(440,310)\">\n <rect x=\"0\" y=\"0\" width=\"240\" height=\"145\" rx=\"8\" fill=\"#f0ece5\" stroke=\"#d9d3c7\" stroke-width=\"1.5\"\/>\n <text x=\"120\" y=\"22\" fill=\"#2a5a8c\" font-size=\"13\" font-weight=\"700\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">MCSA Severity Scale<\/text>\n <line x1=\"12\" y1=\"30\" x2=\"228\" y2=\"30\" stroke=\"#d9d3c7\" stroke-width=\"1\"\/>\n <text x=\"18\" y=\"50\" fill=\"#7a756b\" font-size=\"10\" font-family=\"Source Sans 3,sans-serif\">(sideband amplitude vs LF peak)<\/text>\n <rect x=\"18\" y=\"60\" width=\"12\" height=\"10\" rx=\"2\" fill=\"#2d6b30\"\/><text x=\"36\" y=\"70\" fill=\"#2d6b30\" font-size=\"11\" font-family=\"Source Sans 3,sans-serif\">< \u221254 dB \u2014 healthy rotor<\/text>\n <rect x=\"18\" y=\"80\" width=\"12\" height=\"10\" rx=\"2\" fill=\"#9a6b12\"\/><text x=\"36\" y=\"90\" fill=\"#9a6b12\" font-size=\"11\" font-family=\"Source Sans 3,sans-serif\">\u221254 to \u221248 dB \u2014 suspect 1-2 bars<\/text>\n <rect x=\"18\" y=\"100\" width=\"12\" height=\"10\" rx=\"2\" fill=\"#9a6b12\"\/><text x=\"36\" y=\"110\" fill=\"#9a6b12\" font-size=\"11\" font-family=\"Source Sans 3,sans-serif\">\u221248 to \u221240 dB \u2014 likely multiple<\/text>\n <rect x=\"18\" y=\"120\" width=\"12\" height=\"10\" rx=\"2\" fill=\"#b8372b\"\/><text x=\"36\" y=\"130\" fill=\"#b8372b\" font-size=\"11\" font-weight=\"600\" font-family=\"Source Sans 3,sans-serif\">> \u221240 dB \u2014 severe (plan repair)<\/text>\n <text x=\"18\" y=\"150\" fill=\"#9e9889\" font-size=\"8.5\" font-style=\"italic\" font-family=\"Source Sans 3,sans-serif\">Rule of thumb at rated load<\/text>\n <\/g>\n<\/svg>\n<\/div>\n<p class=\"infographic-note\"><span class=\"legend-blue legend-badge\">1X<\/span><span class=\"legend-yellow legend-badge\">\u00b1Fp sidebands<\/span><span class=\"legend-red legend-badge\">MCSA sidebands<\/span> Broken rotor bars are best confirmed via MCSA. The vibration spectrum suggests the defect; MCSA provides quantitative severity assessment.<\/p>\n\n\n<h3 id=\"rotor-eccentricity\">4.2. Rotor Eccentricity (Static and Dynamic)<\/h3>\n\n<h4>Static Eccentricity<\/h4>\n<p>Shaft centerline offset from stator bore. Produces elevated <strong>2\u00d7LF<\/strong>. In current: rotor slot harmonics at <strong>f<sub>RBPF<\/sub> \u00b1 LF<\/strong>.<\/p>\n\n<h4>Dynamic Eccentricity<\/h4>\n<p>Rotor center orbits around stator bore center. Produces <strong>1X with 2\u00d7LF sidebands<\/strong> and elevated rotor bar pass frequency. In current: sidebands at <strong>LF \u00b1 f<sub>rot<\/sub><\/strong>.<\/p>\n\n<p>In practice, both types are usually present simultaneously \u2014 the pattern is a superposition.<\/p>\n\n\n<h3 id=\"rotor-bow\">4.3. Thermal Rotor Bow<\/h3>\n\n<p>Large motors can develop a temperature gradient causing temporary bow. Produces <strong>1X that varies with time<\/strong> after startup \u2014 typically increasing for 15\u201360 minutes, then stabilizing. The phase angle drifts as the bow develops. Distinguish from mechanical unbalance (which is stable) by monitoring 1X amplitude and phase for 30\u201360 minutes post-startup.<\/p>\n\n\n<h3 id=\"em-field-shift\">4.4. Electromagnetic Field Displacement (Axial Shift)<\/h3>\n\n<p>If the rotor is <strong>axially displaced<\/strong> relative to the stator, the electromagnetic field distribution becomes asymmetric axially. The rotor experiences an oscillating <strong>axial electromagnetic force at 2\u00d7LF<\/strong>.<\/p>\n\n<h4>Causes<\/h4>\n<ul>\n <li>Incorrect rotor axial positioning during assembly or after bearing replacement<\/li>\n <li>Bearing wear allowing excessive axial play<\/li>\n <li>Shaft thrust from the driven machine<\/li>\n <li>Thermal expansion during operation<\/li>\n<\/ul>\n\n<div class=\"formula\"><strong>Axial 2\u00d7LF<\/strong> (dominant) & elevated <strong>1X<\/strong> \u2014 predominantly in the <strong>axial direction<\/strong><\/div>\n\n<div class=\"key-fact red\">\n <div class=\"key-fact-label\">Critical Defect<\/div>\n <p>This defect can be <strong>highly destructive for bearings<\/strong>. The oscillating axial force at 2\u00d7LF creates cyclic fatigue loading on thrust faces. <strong>Always mark the magnetic center position and verify it during bearing replacements.<\/strong> This is one of the most damaging \u2014 yet most preventable \u2014 motor defects.<\/p>\n<\/div>\n\n\n<div class=\"infographic\">\n<div class=\"infographic-title\">Electromagnetic Field Displacement \u2014 Axial Rotor Shift<\/div>\n<svg viewBox=\"0 0 840 520\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" style=\"max-width:100%;\" role=\"img\">\n <rect x=\"0\" y=\"0\" width=\"840\" height=\"520\" rx=\"12\" fill=\"#faf8f5\"\/>\n \n <text x=\"190\" y=\"26\" fill=\"#2d6b30\" font-size=\"15\" font-weight=\"700\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">Normal: Rotor Centered<\/text>\n <rect x=\"45\" y=\"55\" width=\"290\" height=\"115\" rx=\"8\" fill=\"#e8e3da\" stroke=\"#2a5a8c\" stroke-width=\"2\"\/>\n <text x=\"190\" y=\"74\" fill=\"#2a5a8c\" font-size=\"11\" font-weight=\"600\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">STATOR LAMINATION STACK<\/text>\n <rect x=\"70\" y=\"88\" width=\"240\" height=\"48\" rx=\"5\" fill=\"#d9d3c7\" stroke=\"#6b4a8c\" stroke-width=\"2\"\/>\n <text x=\"190\" y=\"118\" fill=\"#3d3b36\" font-size=\"13\" font-weight=\"700\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">ROTOR<\/text>\n <line x1=\"190\" y1=\"48\" x2=\"190\" y2=\"175\" stroke=\"#2d6b30\" stroke-width=\"1.4\" stroke-dasharray=\"5,3\"\/>\n <text x=\"190\" y=\"188\" fill=\"#2d6b30\" font-size=\"10\" font-weight=\"600\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">Stator CL = Rotor CL<\/text>\n <line x1=\"45\" y1=\"142\" x2=\"70\" y2=\"142\" stroke=\"#2d6b30\" stroke-width=\"1.5\"\/><line x1=\"45\" y1=\"137\" x2=\"45\" y2=\"147\" stroke=\"#2d6b30\" stroke-width=\"1.5\"\/><line x1=\"70\" y1=\"137\" x2=\"70\" y2=\"147\" stroke=\"#2d6b30\" stroke-width=\"1.5\"\/>\n <rect x=\"42\" y=\"148\" width=\"32\" height=\"14\" rx=\"3\" fill=\"#edf5ed\"\/><text x=\"58\" y=\"159\" fill=\"#2d6b30\" font-size=\"10\" font-weight=\"600\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">equal<\/text>\n <line x1=\"310\" y1=\"142\" x2=\"335\" y2=\"142\" stroke=\"#2d6b30\" stroke-width=\"1.5\"\/><line x1=\"310\" y1=\"137\" x2=\"310\" y2=\"147\" stroke=\"#2d6b30\" stroke-width=\"1.5\"\/><line x1=\"335\" y1=\"137\" x2=\"335\" y2=\"147\" stroke=\"#2d6b30\" stroke-width=\"1.5\"\/>\n <rect x=\"306\" y=\"148\" width=\"32\" height=\"14\" rx=\"3\" fill=\"#edf5ed\"\/><text x=\"322\" y=\"159\" fill=\"#2d6b30\" font-size=\"10\" font-weight=\"600\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">equal<\/text>\n <g transform=\"translate(45,202)\">\n <rect x=\"0\" y=\"0\" width=\"290\" height=\"70\" rx=\"6\" fill=\"#edf5ed\" stroke=\"#2d6b30\" stroke-width=\"1.5\"\/>\n <text x=\"145\" y=\"19\" fill=\"#2d6b30\" font-size=\"12\" font-weight=\"700\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">\u2713 Balanced axial EM forces<\/text>\n <text x=\"145\" y=\"37\" fill=\"#2d6b30\" font-size=\"11\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">Minimal axial vibration<\/text>\n <line x1=\"12\" y1=\"46\" x2=\"278\" y2=\"46\" stroke=\"#c5d8c2\" stroke-width=\"1\"\/>\n <text x=\"145\" y=\"62\" fill=\"#7a756b\" font-size=\"10\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">Magnetic center = net axial force \u2248 0<\/text>\n <\/g>\n \n <line x1=\"400\" y1=\"18\" x2=\"400\" y2=\"290\" stroke=\"#d9d3c7\" stroke-width=\"1.5\" stroke-dasharray=\"6,4\"\/>\n \n <text x=\"615\" y=\"26\" fill=\"#b8372b\" font-size=\"15\" font-weight=\"700\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">Defect: Rotor Shifted Axially<\/text>\n <rect x=\"430\" y=\"55\" width=\"290\" height=\"115\" rx=\"8\" fill=\"#e8e3da\" stroke=\"#2a5a8c\" stroke-width=\"2\"\/>\n <text x=\"575\" y=\"74\" fill=\"#2a5a8c\" font-size=\"11\" font-weight=\"600\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">STATOR LAMINATION STACK<\/text>\n <rect x=\"500\" y=\"88\" width=\"240\" height=\"48\" rx=\"5\" fill=\"#d9d3c7\" stroke=\"#b8372b\" stroke-width=\"2\"\/>\n <text x=\"620\" y=\"118\" fill=\"#3d3b36\" font-size=\"13\" font-weight=\"700\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">ROTOR<\/text>\n <line x1=\"575\" y1=\"40\" x2=\"575\" y2=\"175\" stroke=\"#2a5a8c\" stroke-width=\"1.4\" stroke-dasharray=\"5,3\"\/>\n <line x1=\"620\" y1=\"40\" x2=\"620\" y2=\"175\" stroke=\"#b8372b\" stroke-width=\"1.4\" stroke-dasharray=\"5,3\"\/>\n <text x=\"567\" y=\"188\" fill=\"#2a5a8c\" font-size=\"10\" font-weight=\"600\" text-anchor=\"end\" font-family=\"Source Sans 3,sans-serif\">Stator CL<\/text>\n <text x=\"628\" y=\"188\" fill=\"#b8372b\" font-size=\"10\" font-weight=\"600\" font-family=\"Source Sans 3,sans-serif\">Rotor CL<\/text>\n \n <line x1=\"575\" y1=\"44\" x2=\"575\" y2=\"38\" stroke=\"#9a6b12\" stroke-width=\"1.5\"\/>\n <line x1=\"620\" y1=\"44\" x2=\"620\" y2=\"38\" stroke=\"#9a6b12\" stroke-width=\"1.5\"\/>\n <line x1=\"578\" y1=\"41\" x2=\"617\" y2=\"41\" stroke=\"#9a6b12\" stroke-width=\"2\" marker-end=\"url(#arrowY5)\"\/>\n <text x=\"597\" y=\"35\" fill=\"#9a6b12\" font-size=\"11\" font-weight=\"700\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">\u0394x (axial shift)<\/text>\n \n <rect x=\"720\" y=\"88\" width=\"20\" height=\"48\" rx=\"3\" fill=\"rgba(154,107,18,0.12)\" stroke=\"#9a6b12\" stroke-width=\"2\" stroke-dasharray=\"4,3\"\/>\n <line x1=\"740\" y1=\"92\" x2=\"762\" y2=\"68\" stroke=\"#9a6b12\" stroke-width=\"1.2\"\/><circle cx=\"740\" cy=\"92\" r=\"2.5\" fill=\"#9a6b12\"\/>\n <text x=\"766\" y=\"58\" fill=\"#9a6b12\" font-size=\"11\" font-weight=\"600\" font-family=\"Source Sans 3,sans-serif\">Rotor extends<\/text>\n <text x=\"766\" y=\"73\" fill=\"#9a6b12\" font-size=\"11\" font-weight=\"600\" font-family=\"Source Sans 3,sans-serif\">beyond stator<\/text>\n \n <line x1=\"565\" y1=\"155\" x2=\"450\" y2=\"155\" stroke=\"#b8372b\" stroke-width=\"4\" marker-end=\"url(#arrowR6)\"\/>\n <text x=\"505\" y=\"172\" fill=\"#b8372b\" font-size=\"12\" font-weight=\"700\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">F axial at 2\u00d7LF<\/text>\n \n <g transform=\"translate(430,202)\">\n <rect x=\"0\" y=\"0\" width=\"290\" height=\"70\" rx=\"6\" fill=\"#fdf0ee\" stroke=\"#b8372b\" stroke-width=\"1.5\"\/>\n <text x=\"145\" y=\"18\" fill=\"#b8372b\" font-size=\"12\" font-weight=\"700\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">\u2717 Elevated axial 2\u00d7LF & 1X<\/text>\n <text x=\"145\" y=\"36\" fill=\"#b8372b\" font-size=\"11\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">Can accelerate thrust bearing wear<\/text>\n <line x1=\"12\" y1=\"46\" x2=\"278\" y2=\"46\" stroke=\"#e5c0b8\" stroke-width=\"1\"\/>\n <text x=\"145\" y=\"62\" fill=\"#7a756b\" font-size=\"10\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">Severity depends on shift magnitude<\/text>\n <\/g>\n \n <g transform=\"translate(20,295)\">\n <rect x=\"0\" y=\"0\" width=\"800\" height=\"80\" rx=\"10\" fill=\"#f0ece5\" stroke=\"#d9d3c7\" stroke-width=\"1.5\"\/>\n <text x=\"400\" y=\"20\" fill=\"#2a5a8c\" font-size=\"13\" font-weight=\"700\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">How to detect & confirm:<\/text>\n <line x1=\"15\" y1=\"28\" x2=\"785\" y2=\"28\" stroke=\"#d9d3c7\" stroke-width=\"1\"\/>\n <text x=\"20\" y=\"46\" fill=\"#2d6b30\" font-size=\"11\" font-family=\"Source Sans 3,sans-serif\">\u2713 Mark magnetic center during assembly<\/text>\n <text x=\"290\" y=\"46\" fill=\"#2d6b30\" font-size=\"11\" font-family=\"Source Sans 3,sans-serif\">\u2713 Verify position after bearing replacement<\/text>\n <text x=\"600\" y=\"46\" fill=\"#2d6b30\" font-size=\"11\" font-family=\"Source Sans 3,sans-serif\">\u2713 Measure axial vibr. at 2\u00d7LF<\/text>\n <text x=\"20\" y=\"64\" fill=\"#2d6b30\" font-size=\"11\" font-family=\"Source Sans 3,sans-serif\">\u2713 Power-off test: 2\u00d7LF disappears instantly<\/text>\n <text x=\"290\" y=\"64\" fill=\"#2d6b30\" font-size=\"11\" font-family=\"Source Sans 3,sans-serif\">\u2713 Compare coast-down: electrical vs mechanical<\/text>\n <text x=\"600\" y=\"64\" fill=\"#2d6b30\" font-size=\"11\" font-family=\"Source Sans 3,sans-serif\">\u2713 Check thrust bearing temp.<\/text>\n <\/g>\n <g transform=\"translate(20,390)\">\n <rect x=\"0\" y=\"0\" width=\"800\" height=\"80\" rx=\"10\" fill=\"#f0ece5\" stroke=\"#9a6b12\" stroke-width=\"1.5\"\/>\n <text x=\"400\" y=\"20\" fill=\"#9a6b12\" font-size=\"13\" font-weight=\"700\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">Rule out (similar symptoms):<\/text>\n <line x1=\"15\" y1=\"28\" x2=\"785\" y2=\"28\" stroke=\"#d9d3c7\" stroke-width=\"1\"\/>\n <text x=\"20\" y=\"46\" fill=\"#3d3b36\" font-size=\"10.5\" font-family=\"Source Sans 3,sans-serif\">\u2022 Coupling angular misalignment (axial 1X & 2X)<\/text>\n <text x=\"290\" y=\"46\" fill=\"#3d3b36\" font-size=\"10.5\" font-family=\"Source Sans 3,sans-serif\">\u2022 Axial structural resonance<\/text>\n <text x=\"540\" y=\"46\" fill=\"#3d3b36\" font-size=\"10.5\" font-family=\"Source Sans 3,sans-serif\">\u2022 Soft foot \/ looseness (axial component)<\/text>\n <text x=\"20\" y=\"64\" fill=\"#3d3b36\" font-size=\"10.5\" font-family=\"Source Sans 3,sans-serif\">\u2022 Flow-induced axial load (pumps, fans)<\/text>\n <text x=\"290\" y=\"64\" fill=\"#3d3b36\" font-size=\"10.5\" font-family=\"Source Sans 3,sans-serif\">\u2022 Supply voltage unbalance<\/text>\n <text x=\"540\" y=\"64\" fill=\"#3d3b36\" font-size=\"10.5\" font-family=\"Source Sans 3,sans-serif\">\u2022 Radial eccentricity (\u2192 2\u00d7LF radial)<\/text>\n <\/g>\n <text x=\"420\" y=\"495\" fill=\"#9e9889\" font-size=\"9.5\" font-style=\"italic\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">Schematic axial side view \u2014 not to scale.<\/text>\n <defs>\n <marker id=\"arrowR6\" markerWidth=\"10\" markerHeight=\"8\" refX=\"9\" refY=\"4\" orient=\"auto\"><polygon points=\"0 0, 10 4, 0 8\" fill=\"#b8372b\"\/><\/marker>\n <marker id=\"arrowY5\" markerWidth=\"8\" markerHeight=\"6\" refX=\"7\" refY=\"3\" orient=\"auto\"><polygon points=\"0 0, 8 3, 0 6\" fill=\"#9a6b12\"\/><\/marker>\n <\/defs>\n<\/svg>\n<\/div>\n<p class=\"infographic-note\"><span class=\"legend-red legend-badge\">Axial EM force<\/span><span class=\"legend-yellow legend-badge\">Shift \/ overhang<\/span><span class=\"legend-blue legend-badge\">Stator CL<\/span><span class=\"legend-green legend-badge\">Detection<\/span> Axial 2\u00d7LF that vanishes instantly on power-off is the key differentiator from mechanical causes.<\/p>\n\n\n\n<h2 id=\"bearings-electrical\"><span class=\"section-num\">5.<\/span> Bearing-Related Electrical Defects<\/h2>\n\n<h3>5.1. Bearing Currents and EDM<\/h3>\n<p>Voltage between shaft and housing causes current flow through bearings. Sources: magnetic asymmetry, VFD common-mode voltage, static charge. Repeated discharges create microscopic pits (<strong>Electrical Discharge Machining<\/strong>) leading to <strong>fluting<\/strong> \u2014 evenly spaced grooves on races.<\/p>\n\n<h4>Spectral Signature<\/h4>\n<ul>\n <li>Bearing defect frequencies (BPFO, BPFI, BSF) with very uniform, \"clean\" peaks<\/li>\n <li>Elevated high-frequency noise floor in acceleration spectrum<\/li>\n <li>Advanced: characteristic \"washboard\" sound<\/li>\n<\/ul>\n\n<h4>Prevention<\/h4>\n<ul>\n <li>Insulated bearings (coated rings)<\/li>\n <li>Shaft grounding brushes (especially for VFD applications)<\/li>\n <li>Common-mode filters on VFD output<\/li>\n <li>Regular shaft voltage measurement \u2014 below 0.5 V peak<\/li>\n<\/ul>\n\n\n\n<h2 id=\"vfd\"><span class=\"section-num\">6.<\/span> Variable Frequency Drive (VFD) Effects<\/h2>\n\n<h3>6.1. Frequency Shifting<\/h3>\n<p>All motor electrical frequencies shift proportionally with VFD output frequency. If VFD runs at 45 Hz, 2\u00d7LF becomes 90 Hz. Alarm bands must be <strong>speed-adaptive<\/strong>.<\/p>\n\n<h3>6.2. PWM Harmonics<\/h3>\n<p>Switching frequency (2\u201316 kHz) and sidebands appear in spectra. Can cause audible noise and bearing currents.<\/p>\n\n<h3>6.3. Torsional Excitation<\/h3>\n<p>Low-order harmonics (5th, 7th, 11th, 13th) create torque pulsations that can excite torsional natural frequencies.<\/p>\n\n<h3>6.4. Resonance Excitation<\/h3>\n<p>As VFD sweeps through a speed range, excitation frequencies may pass through structural natural frequencies. Critical speed maps should be established for VFD-driven equipment.<\/p>\n\n\n\n<h2 id=\"differential\"><span class=\"section-num\">7.<\/span> Differential Diagnostics Summary<\/h2>\n\n<div class=\"table-wrap\">\n<table>\n<thead><tr><th>Defect<\/th><th>Primary Freq.<\/th><th>Direction<\/th><th>Sidebands \/ Notes<\/th><th>Confirmation<\/th><\/tr><\/thead>\n<tbody>\n<tr><td><strong>Stator eccentricity<\/strong><\/td><td>2\u00d7LF<\/td><td>Radial<\/td><td>Minor 1X, 2X increase<\/td><td>Power-off test; soft foot check<\/td><\/tr>\n<tr><td><strong>Loose windings<\/strong><\/td><td>2\u00d7LF<\/td><td>Radial<\/td><td>Increasing trend; 4\u00d7LF, 6\u00d7LF<\/td><td>Trending; MCA surge test<\/td><\/tr>\n<tr><td><strong>Loose cable<\/strong><\/td><td>2\u00d7LF<\/td><td>Radial<\/td><td>\u00b1 \u2153\u00d7LF sidebands<\/td><td>Phase resistance; IR thermography<\/td><\/tr>\n<tr><td><strong>Inter-turn short<\/strong><\/td><td>2\u00d7LF<\/td><td>Radial<\/td><td>Current asymmetry; 3rd harmonic<\/td><td>MCA surge test; MCSA<\/td><\/tr>\n<tr><td><strong>Shorted laminations<\/strong><\/td><td>Minor 2\u00d7LF<\/td><td>\u2014<\/td><td>Primarily thermal<\/td><td>IR thermography; EL-CID<\/td><\/tr>\n<tr><td><strong>Broken rotor bars<\/strong><\/td><td>1X<\/td><td>Radial<\/td><td>\u00b1 F<sub>p<\/sub> sidebands; beating<\/td><td>MCSA: LF \u00b1 F<sub>p<\/sub> dB level<\/td><\/tr>\n<tr><td><strong>Rotor eccentricity (static)<\/strong><\/td><td>2\u00d7LF<\/td><td>Radial<\/td><td>Rotor slot harmonics \u00b1 LF<\/td><td>Air gap measurement; MCSA<\/td><\/tr>\n<tr><td><strong>Rotor eccentricity (dynamic)<\/strong><\/td><td>1X + 2\u00d7LF<\/td><td>Radial<\/td><td>f<sub>RBPF<\/sub> sidebands<\/td><td>Orbit analysis; MCSA<\/td><\/tr>\n<tr><td><strong>Thermal rotor bow<\/strong><\/td><td>1X (drifting)<\/td><td>Radial<\/td><td>Amp & phase change with temp.<\/td><td>30-60 min startup trending<\/td><\/tr>\n<tr><td><strong>EM field displacement<\/strong><\/td><td>2\u00d7LF + 1X<\/td><td><strong>Axial<\/strong><\/td><td>Strong axial 2\u00d7LF<\/td><td>Rotor axial position; power-off test<\/td><\/tr>\n<tr><td><strong>Bearing EDM \/ fluting<\/strong><\/td><td>BPFO \/ BPFI<\/td><td>Radial<\/td><td>Uniform peaks; high HF noise<\/td><td>Shaft voltage; visual inspection<\/td><\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n\n\n<div class=\"infographic\">\n<div class=\"infographic-title\">Motor Defect Diagnostic Flowchart<\/div>\n<svg viewBox=\"0 0 760 420\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" style=\"max-width:100%;\" role=\"img\">\n <rect x=\"0\" y=\"0\" width=\"760\" height=\"420\" rx=\"12\" fill=\"#faf8f5\"\/>\n \n <rect x=\"280\" y=\"12\" width=\"200\" height=\"36\" rx=\"18\" fill=\"#eef4fa\" stroke=\"#2a5a8c\" stroke-width=\"2\"\/>\n <text x=\"380\" y=\"36\" fill=\"#3d3b36\" font-size=\"12\" font-weight=\"600\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">Elevated motor vibration<\/text>\n <line x1=\"380\" y1=\"48\" x2=\"380\" y2=\"68\" stroke=\"#2a5a8c\" stroke-width=\"1.5\" marker-end=\"url(#aB3)\"\/>\n \n <polygon points=\"380,68 470,100 380,132 290,100\" fill=\"#fef9ec\" stroke=\"#9a6b12\" stroke-width=\"1.5\"\/>\n <text x=\"380\" y=\"96\" fill=\"#9a6b12\" font-size=\"10\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">Power-off<\/text>\n <text x=\"380\" y=\"110\" fill=\"#9a6b12\" font-size=\"10\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">snap test?<\/text>\n \n <line x1=\"290\" y1=\"100\" x2=\"190\" y2=\"100\" stroke=\"#b8372b\" stroke-width=\"1.5\"\/><text x=\"240\" y=\"93\" fill=\"#b8372b\" font-size=\"9\" font-family=\"Source Sans 3,sans-serif\">Instant drop<\/text>\n <rect x=\"60\" y=\"80\" width=\"130\" height=\"40\" rx=\"6\" fill=\"#fdf0ee\" stroke=\"#b8372b\" stroke-width=\"1.5\"\/>\n <text x=\"125\" y=\"98\" fill=\"#b8372b\" font-size=\"11\" font-weight=\"600\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">ELECTRICAL<\/text>\n <text x=\"125\" y=\"112\" fill=\"#3d3b36\" font-size=\"9\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">source confirmed<\/text>\n <line x1=\"125\" y1=\"120\" x2=\"125\" y2=\"148\" stroke=\"#b8372b\" stroke-width=\"1.5\" marker-end=\"url(#aR3)\"\/>\n \n <polygon points=\"125,148 215,180 125,212 35,180\" fill=\"#faf8f5\" stroke=\"#2a5a8c\" stroke-width=\"1.5\"\/>\n <text x=\"125\" y=\"176\" fill=\"#2a5a8c\" font-size=\"9\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">Dominant<\/text>\n <text x=\"125\" y=\"190\" fill=\"#2a5a8c\" font-size=\"9\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">frequency?<\/text>\n \n <line x1=\"35\" y1=\"180\" x2=\"15\" y2=\"180\" stroke=\"#2a5a8c\" stroke-width=\"1\"\/><line x1=\"15\" y1=\"180\" x2=\"15\" y2=\"250\" stroke=\"#2a5a8c\" stroke-width=\"1\"\/>\n <rect x=\"5\" y=\"252\" width=\"160\" height=\"70\" rx=\"6\" fill=\"#eef4fa\" stroke=\"#2a5a8c\" stroke-width=\"1\"\/>\n <text x=\"85\" y=\"268\" fill=\"#2a5a8c\" font-size=\"9.5\" font-weight=\"600\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">2\u00d7LF (radial):<\/text>\n <text x=\"85\" y=\"283\" fill=\"#7a756b\" font-size=\"8.5\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">\u2022 Eccentricity \/ air gap<\/text>\n <text x=\"85\" y=\"296\" fill=\"#7a756b\" font-size=\"8.5\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">\u2022 Loose windings (trending)<\/text>\n <text x=\"85\" y=\"309\" fill=\"#7a756b\" font-size=\"8.5\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">\u2022 Loose cable (+\u2153LF bands)<\/text>\n \n <line x1=\"125\" y1=\"212\" x2=\"125\" y2=\"252\" stroke=\"#b8372b\" stroke-width=\"1\"\/>\n <rect x=\"175\" y=\"252\" width=\"155\" height=\"50\" rx=\"6\" fill=\"#fdf0ee\" stroke=\"#b8372b\" stroke-width=\"1\"\/>\n <text x=\"252\" y=\"272\" fill=\"#b8372b\" font-size=\"9.5\" font-weight=\"600\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">EM field displacement<\/text>\n <text x=\"252\" y=\"288\" fill=\"#3d3b36\" font-size=\"8.5\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">Check rotor axial position!<\/text>\n \n <line x1=\"215\" y1=\"180\" x2=\"260\" y2=\"180\" stroke=\"#9a6b12\" stroke-width=\"1\"\/><line x1=\"260\" y1=\"180\" x2=\"260\" y2=\"252\" stroke=\"#9a6b12\" stroke-width=\"1\"\/>\n <rect x=\"345\" y=\"252\" width=\"140\" height=\"50\" rx=\"6\" fill=\"#fef9ec\" stroke=\"#9a6b12\" stroke-width=\"1\"\/>\n <text x=\"415\" y=\"272\" fill=\"#9a6b12\" font-size=\"9.5\" font-weight=\"600\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">Broken rotor bars<\/text>\n <text x=\"415\" y=\"288\" fill=\"#3d3b36\" font-size=\"8.5\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">Confirm with MCSA<\/text>\n \n <line x1=\"470\" y1=\"100\" x2=\"570\" y2=\"100\" stroke=\"#2d6b30\" stroke-width=\"1.5\"\/><text x=\"520\" y=\"93\" fill=\"#2d6b30\" font-size=\"9\" font-family=\"Source Sans 3,sans-serif\">Gradual decay<\/text>\n <rect x=\"570\" y=\"80\" width=\"130\" height=\"40\" rx=\"6\" fill=\"#edf5ed\" stroke=\"#2d6b30\" stroke-width=\"1.5\"\/>\n <text x=\"635\" y=\"98\" fill=\"#2d6b30\" font-size=\"11\" font-weight=\"600\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">MECHANICAL<\/text>\n <text x=\"635\" y=\"112\" fill=\"#3d3b36\" font-size=\"9\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">source confirmed<\/text>\n <line x1=\"635\" y1=\"120\" x2=\"635\" y2=\"148\" stroke=\"#2d6b30\" stroke-width=\"1.5\" marker-end=\"url(#aG3)\"\/>\n <rect x=\"555\" y=\"148\" width=\"160\" height=\"60\" rx=\"6\" fill=\"#edf5ed\" stroke=\"#2d6b30\" stroke-width=\"1\"\/>\n <text x=\"635\" y=\"166\" fill=\"#2d6b30\" font-size=\"9.5\" font-weight=\"600\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">Investigate:<\/text>\n <text x=\"635\" y=\"182\" fill=\"#7a756b\" font-size=\"8.5\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">\u2022 Unbalance, misalignment<\/text>\n <text x=\"635\" y=\"195\" fill=\"#7a756b\" font-size=\"8.5\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">\u2022 Bearing defects, soft foot<\/text>\n \n <rect x=\"180\" y=\"340\" width=\"400\" height=\"35\" rx=\"8\" fill=\"#eef4fa\" stroke=\"#2a5a8c\" stroke-width=\"1.5\"\/>\n <text x=\"380\" y=\"358\" fill=\"#2a5a8c\" font-size=\"11\" font-weight=\"600\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">Always combine: Vibration + MCSA + Power-off test + Trending<\/text>\n <rect x=\"180\" y=\"385\" width=\"400\" height=\"28\" rx=\"14\" fill=\"#edf5ed\" stroke=\"#2d6b30\" stroke-width=\"2\"\/>\n <text x=\"380\" y=\"404\" fill=\"#2d6b30\" font-size=\"11\" font-weight=\"600\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">Resolution reminder: \u2264 0.5 Hz to separate 2X from 2\u00d7LF<\/text>\n <defs>\n <marker id=\"aB3\" markerWidth=\"8\" markerHeight=\"6\" refX=\"4\" refY=\"3\" orient=\"auto\"><polygon points=\"0 0, 8 3, 0 6\" fill=\"#2a5a8c\"\/><\/marker>\n <marker id=\"aR3\" markerWidth=\"8\" markerHeight=\"6\" refX=\"4\" refY=\"3\" orient=\"auto\"><polygon points=\"0 0, 8 3, 0 6\" fill=\"#b8372b\"\/><\/marker>\n <marker id=\"aG3\" markerWidth=\"8\" markerHeight=\"6\" refX=\"4\" refY=\"3\" orient=\"auto\"><polygon points=\"0 0, 8 3, 0 6\" fill=\"#2d6b30\"\/><\/marker>\n <\/defs>\n<\/svg>\n<\/div>\n<p class=\"infographic-note\"><span class=\"legend-red legend-badge\">Electrical<\/span><span class=\"legend-green legend-badge\">Mechanical<\/span><span class=\"legend-blue legend-badge\">2\u00d7LF analysis<\/span><span class=\"legend-yellow legend-badge\">Rotor defects<\/span> The power-off snap test is the first fork in the diagnostic tree. Once electrical origin is confirmed, dominant frequency and direction narrow the diagnosis.<\/p>\n\n\n\n<h2 id=\"instrumentation\"><span class=\"section-num\">8.<\/span> Instrumentation and Measurement Techniques<\/h2>\n\n<h3>8.1. Vibration Measurement Requirements<\/h3>\n\n<div class=\"table-wrap\">\n<table>\n<thead><tr><th>Parameter<\/th><th>Requirement<\/th><th>Reason<\/th><\/tr><\/thead>\n<tbody>\n<tr><td><strong>Spectral resolution<\/strong><\/td><td>\u2264 0.5 Hz (preferably 0.125 Hz)<\/td><td>Separate 2X from 2\u00d7LF (2 Hz apart for 2-pole)<\/td><\/tr>\n<tr><td><strong>Frequency range<\/strong><\/td><td>2\u20131000 Hz (vel.); to 10 kHz (acc.)<\/td><td>Low range for 1X, 2\u00d7LF; high for bearings<\/td><\/tr>\n<tr><td><strong>Channels<\/strong><\/td><td>\u2265 2 simultaneous<\/td><td>Cross-phase analysis<\/td><\/tr>\n<tr><td><strong>Phase measurement<\/strong><\/td><td>0\u2013360\u00b0, \u00b12\u00b0<\/td><td>Critical for defect differentiation<\/td><\/tr>\n<tr><td><strong>Time waveform<\/strong><\/td><td>Synchronous averaging<\/td><td>Detect beating from broken bars<\/td><\/tr>\n<tr><td><strong>Current input<\/strong><\/td><td>Current clamp compatible<\/td><td>For MCSA diagnostics<\/td><\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n\n<h3>8.2. Balanset-1A for Motor Diagnostics<\/h3>\n\n<p>The portable dual-channel vibrometer <strong>Balanset-1A<\/strong> (VibroMera) provides core capabilities for motor vibration diagnostics:<\/p>\n\n<div class=\"spec-grid\">\n <div class=\"spec-item\"><span class=\"spec-item-label\">Vibration Channels<\/span><span class=\"spec-item-value\">2 (simultaneous)<\/span><\/div>\n <div class=\"spec-item\"><span class=\"spec-item-label\">Speed Range<\/span><span class=\"spec-item-value\">250\u201390,000 RPM<\/span><\/div>\n <div class=\"spec-item\"><span class=\"spec-item-label\">Vibration Velocity RMS<\/span><span class=\"spec-item-value\">0\u201380 mm\/s<\/span><\/div>\n <div class=\"spec-item\"><span class=\"spec-item-label\">Phase Accuracy<\/span><span class=\"spec-item-value\">0\u2013360\u00b0, \u00b12\u00b0<\/span><\/div>\n <div class=\"spec-item\"><span class=\"spec-item-label\">FFT Spectral Analysis<\/span><span class=\"spec-item-value\">Supported<\/span><\/div>\n <div class=\"spec-item\"><span class=\"spec-item-label\">Phase Sensor<\/span><span class=\"spec-item-value\">Photoelectric, included<\/span><\/div>\n <div class=\"spec-item\"><span class=\"spec-item-label\">Power Supply<\/span><span class=\"spec-item-value\">USB (7\u201320 V)<\/span><\/div>\n <div class=\"spec-item\"><span class=\"spec-item-label\">Balancing<\/span><span class=\"spec-item-value\">1 or 2 planes in-situ<\/span><\/div>\n<\/div>\n\n<p>After diagnosing and correcting the motor defect, the Balanset-1A can be used for <strong>in-situ rotor balancing<\/strong> \u2014 completing the full diagnostic-to-correction workflow without removing the motor.<\/p>\n\n<h3>8.3. Measurement Best Practices<\/h3>\n<ul>\n <li><strong>Three directions<\/strong> \u2014 vertical, horizontal, and axial \u2014 on each bearing. Axial is critical for EM field displacement<\/li>\n <li><strong>Prepare surfaces<\/strong> \u2014 remove paint, rust for reliable accelerometer coupling<\/li>\n <li><strong>Steady-state conditions<\/strong> \u2014 nominal speed, load, temperature<\/li>\n <li><strong>Record operating conditions<\/strong> \u2014 speed, load, voltage, current with each measurement<\/li>\n <li><strong>Consistent timing<\/strong> \u2014 same conditions for trend comparisons<\/li>\n <li><strong>Power-off test<\/strong> when electrical vibration is suspected \u2014 takes seconds, provides reliable source identification<\/li>\n<\/ul>\n\n\n\n<h2 id=\"standards\"><span class=\"section-num\">9.<\/span> Normative References<\/h2>\n\n<ul class=\"standards-list\">\n <li><strong>GOST R ISO 20816-1-2021<\/strong> \u2014 Vibration. Measurement and evaluation of machine vibration. Part 1. General guidelines.<\/li>\n <li><strong>GOST R ISO 18436-2-2005<\/strong> \u2014 Condition monitoring. Vibration condition monitoring. Part 2. Training and certification.<\/li>\n <li><strong>ISO 20816-1:2016<\/strong> \u2014 Mechanical vibration. Measurement and evaluation. Part 1: General guidelines.<\/li>\n <li><strong>ISO 10816-3:2009<\/strong> \u2014 Evaluation of machine vibration. Part 3: Industrial machines >15 kW.<\/li>\n <li><strong>IEC 60034-14:2018<\/strong> \u2014 Rotating electrical machines. Part 14: Mechanical vibration.<\/li>\n <li><strong>IEEE 43-2013<\/strong> \u2014 Recommended practice for testing insulation resistance.<\/li>\n <li><strong>IEEE 1415-2006<\/strong> \u2014 Guide for induction machinery maintenance testing.<\/li>\n <li><strong>NEMA MG 1-2021<\/strong> \u2014 Motors and generators. Vibration limits and testing.<\/li>\n <li><strong>ISO 1940-1:2003<\/strong> \u2014 Balance quality requirements for rotors.<\/li>\n<\/ul>\n\n\n\n<h2 id=\"conclusion\"><span class=\"section-num\">10.<\/span> Conclusion<\/h2>\n\n<div class=\"conclusion-box\">\n <h3>Key Diagnostic Principles<\/h3>\n <p>Electric motor defects leave characteristic fingerprints in vibration and current spectra \u2014 but only if you know where to look and have the right tools configured correctly.<\/p>\n<\/div>\n\n<ol>\n <li><strong>2\u00d7LF is the primary electromagnetic indicator.<\/strong> A prominent peak at exactly twice supply frequency strongly suggests an electromagnetic source. The power-off test provides confirmation.<\/li>\n <li><strong>Direction matters.<\/strong> Radial 2\u00d7LF \u2192 air gap \/ windings \/ supply. <strong>Axial<\/strong> 2\u00d7LF + 1X \u2192 electromagnetic field displacement \u2014 one of the most destructive defects.<\/li>\n <li><strong>Sidebands tell the story.<\/strong> \u00b1 \u2153\u00d7LF \u2192 supply cable problems. \u00b1 F<sub>p<\/sub> \u2192 broken rotor bars. The sideband pattern is often more diagnostic than the main peak.<\/li>\n <li><strong>Spectral resolution is critical.<\/strong> For 2-pole motors at 50 Hz, 2X and 2\u00d7LF are only ~2 Hz apart. Resolution \u2264 0.5 Hz is mandatory.<\/li>\n <li><strong>Combine methods.<\/strong> Vibration + MCSA + MCA + Thermography. No single method covers all defects.<\/li>\n <li><strong>Talk to the electricians.<\/strong> Motor repair personnel possess irreplaceable knowledge about specific motors, their history, and supply conditions.<\/li>\n<\/ol>\n\n<h4>Recommended Workflow<\/h4>\n\n<div class=\"workflow-strip\">\n <div class=\"workflow-step\"><div class=\"workflow-step-num\">1<\/div><div class=\"workflow-step-label\">Vibration Measurement<\/div><\/div>\n <div class=\"workflow-step\"><div class=\"workflow-step-num\">2<\/div><div class=\"workflow-step-label\">Power-Off Test<\/div><\/div>\n <div class=\"workflow-step\"><div class=\"workflow-step-num\">3<\/div><div class=\"workflow-step-label\">Spectral Analysis<\/div><\/div>\n <div class=\"workflow-step\"><div class=\"workflow-step-num\">4<\/div><div class=\"workflow-step-label\">MCSA (if rotor)<\/div><\/div>\n <div class=\"workflow-step\"><div class=\"workflow-step-num\">5<\/div><div class=\"workflow-step-label\">Correct & Balance<\/div><\/div>\n <div class=\"workflow-step\"><div class=\"workflow-step-num\">6<\/div><div class=\"workflow-step-label\">Verification \u2713<\/div><\/div>\n<\/div>\n\n\n<div class=\"infographic\">\n<div class=\"infographic-title\">Motor Diagnostics \u2014 Recommended Workflow<\/div>\n<svg viewBox=\"0 0 720 320\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" style=\"max-width:100%;\" role=\"img\">\n <rect x=\"0\" y=\"0\" width=\"720\" height=\"320\" rx=\"12\" fill=\"#faf8f5\"\/>\n <rect x=\"250\" y=\"12\" width=\"220\" height=\"40\" rx=\"8\" fill=\"#eef4fa\" stroke=\"#2a5a8c\" stroke-width=\"2\"\/>\n <text x=\"360\" y=\"30\" fill=\"#3d3b36\" font-size=\"11\" font-weight=\"600\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">1. Vibration measurement<\/text>\n <text x=\"360\" y=\"44\" fill=\"#7a756b\" font-size=\"9\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">3 directions, all bearings, \u22640.5 Hz res.<\/text>\n <line x1=\"360\" y1=\"52\" x2=\"360\" y2=\"68\" stroke=\"#2a5a8c\" stroke-width=\"1.5\" marker-end=\"url(#aB4)\"\/>\n <rect x=\"250\" y=\"68\" width=\"220\" height=\"40\" rx=\"8\" fill=\"#eef4fa\" stroke=\"#2a5a8c\" stroke-width=\"2\"\/>\n <text x=\"360\" y=\"86\" fill=\"#3d3b36\" font-size=\"11\" font-weight=\"600\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">2. Power-off snap test<\/text>\n <text x=\"360\" y=\"100\" fill=\"#7a756b\" font-size=\"9\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">Electrical vs. mechanical source<\/text>\n <line x1=\"360\" y1=\"108\" x2=\"360\" y2=\"124\" stroke=\"#2a5a8c\" stroke-width=\"1.5\" marker-end=\"url(#aB4)\"\/>\n <rect x=\"250\" y=\"124\" width=\"220\" height=\"40\" rx=\"8\" fill=\"#eef4fa\" stroke=\"#2a5a8c\" stroke-width=\"2\"\/>\n <text x=\"360\" y=\"142\" fill=\"#3d3b36\" font-size=\"11\" font-weight=\"600\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">3. Spectral analysis<\/text>\n <text x=\"360\" y=\"156\" fill=\"#7a756b\" font-size=\"9\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">2\u00d7LF, 1X, sidebands, direction<\/text>\n <line x1=\"360\" y1=\"164\" x2=\"360\" y2=\"180\" stroke=\"#2a5a8c\" stroke-width=\"1.5\" marker-end=\"url(#aB4)\"\/>\n <rect x=\"250\" y=\"180\" width=\"220\" height=\"40\" rx=\"8\" fill=\"#fef9ec\" stroke=\"#9a6b12\" stroke-width=\"2\"\/>\n <text x=\"360\" y=\"198\" fill=\"#3d3b36\" font-size=\"11\" font-weight=\"600\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">4. MCSA (if rotor suspected)<\/text>\n <text x=\"360\" y=\"212\" fill=\"#7a756b\" font-size=\"9\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">Current clamp, LF \u00b1 Fp analysis<\/text>\n <line x1=\"360\" y1=\"220\" x2=\"360\" y2=\"236\" stroke=\"#2a5a8c\" stroke-width=\"1.5\" marker-end=\"url(#aB4)\"\/>\n <rect x=\"250\" y=\"236\" width=\"220\" height=\"36\" rx=\"8\" fill=\"#eef4fa\" stroke=\"#5a8ab8\" stroke-width=\"1.5\"\/>\n <text x=\"360\" y=\"258\" fill=\"#3d3b36\" font-size=\"11\" font-weight=\"600\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">5. Correct & balance (Balanset-1A)<\/text>\n <line x1=\"360\" y1=\"272\" x2=\"360\" y2=\"286\" stroke=\"#2a5a8c\" stroke-width=\"1.5\" marker-end=\"url(#aB4)\"\/>\n <rect x=\"230\" y=\"286\" width=\"260\" height=\"26\" rx=\"13\" fill=\"#edf5ed\" stroke=\"#2d6b30\" stroke-width=\"2\"\/>\n <text x=\"360\" y=\"304\" fill=\"#2d6b30\" font-size=\"11\" font-weight=\"600\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">6. Verification measurement \u2713<\/text>\n <g transform=\"translate(15,15)\">\n <rect x=\"0\" y=\"0\" width=\"200\" height=\"70\" rx=\"6\" fill=\"#f0ece5\" stroke=\"#d9d3c7\" stroke-width=\"1\"\/>\n <text x=\"100\" y=\"18\" fill=\"#2a5a8c\" font-size=\"10\" font-weight=\"600\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">Balanset-1A covers:<\/text>\n <text x=\"100\" y=\"34\" fill=\"#7a756b\" font-size=\"9\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">\u25b8 Steps 1, 3 \u2014 vibration spectra<\/text>\n <text x=\"100\" y=\"48\" fill=\"#7a756b\" font-size=\"9\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">\u25b8 Step 5 \u2014 field balancing<\/text>\n <text x=\"100\" y=\"62\" fill=\"#7a756b\" font-size=\"9\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">\u25b8 Step 6 \u2014 verification<\/text>\n <\/g>\n <defs><marker id=\"aB4\" markerWidth=\"8\" markerHeight=\"6\" refX=\"4\" refY=\"3\" orient=\"auto\"><polygon points=\"0 0, 8 3, 0 6\" fill=\"#2a5a8c\"\/><\/marker><\/defs>\n<\/svg>\n<\/div>\n<p class=\"infographic-note\"><span class=\"legend-blue legend-badge\">Diagnostic steps<\/span><span class=\"legend-yellow legend-badge\">MCSA<\/span><span class=\"legend-green legend-badge\">Verification<\/span> Follow this sequence systematically. The power-off test (step 2) takes seconds and reliably distinguishes electrical vs. mechanical source.<\/p>\n\n<p>Modern portable dual-channel vibrometers such as the <strong>Balanset-1A<\/strong> enable field engineers to perform spectral vibration analysis with the resolution and phase accuracy required for motor defect identification \u2014 from detecting uneven air gaps through cross-phase analysis to subsequent in-situ rotor balancing.<\/p>\n\n<hr>\n\n<footer class=\"article-footer\">\n <p><em>Sources: field vibration diagnostics training programs; GOST R ISO 20816-1-2021; GOST R ISO 18436-2-2005; IEC 60034-14:2018; IEEE 1415-2006; ISO 1940-1:2003; VibroMera technical documentation (Balanset-1A); EPRI motor reliability studies.<\/em><\/p>\n<\/footer>\n\n<\/main>\n<\/div>\n\n<script>\nwindow.addEventListener('scroll',()=>{const h=document.documentElement.scrollHeight-document.documentElement.clientHeight;const s=(window.scrollY\/h)*100;document.getElementById('progressBar').style.width=s+'%';const b=document.getElementById('backToTop');b.classList.toggle('visible',window.scrollY>400)});\nconst sections=document.querySelectorAll('h2[id],h3[id]');const tocLinks=document.querySelectorAll('.toc-list a');\nconst observer=new IntersectionObserver(entries=>{entries.forEach(entry=>{if(entry.isIntersecting){const id=entry.target.getAttribute('id');tocLinks.forEach(link=>{link.classList.remove('active');if(link.getAttribute('data-section')===id)link.classList.add('active')})}})},{rootMargin:'-20% 0px -70% 0px'});\nsections.forEach(s=>observer.observe(s));\n<\/script>\n<\/body>\n<\/html><\/div><\/div><\/div><\/div><\/div>","protected":false},"excerpt":{"rendered":"<p>Electric Motor Defects: Comprehensive Spectral Analysis VibroMera Technical Knowledge Base Table of Contents 1. Electrical Fundamentals 2. Diagnostic Methods 3. Stator Defects 3.1 Stator Eccentricity 3.2 Loose Windings 3.3 Loose Power Cable 3.4 Shorted Laminations 3.5 Inter-Turn Short 4. Rotor Defects 4.1 Broken Rotor Bars 4.2 Rotor Eccentricity 4.3 Thermal […]<\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"ai_generated_summary":"","footnotes":""},"categories":[1],"tags":[],"class_list":["post-100667","post","type-post","status-publish","format-standard","hentry","category-uncategorized"],"_links":{"self":[{"href":"https:\/\/vibromera.eu\/nb\/wp-json\/wp\/v2\/posts\/100667","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/vibromera.eu\/nb\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/vibromera.eu\/nb\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/vibromera.eu\/nb\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/vibromera.eu\/nb\/wp-json\/wp\/v2\/comments?post=100667"}],"version-history":[{"count":8,"href":"https:\/\/vibromera.eu\/nb\/wp-json\/wp\/v2\/posts\/100667\/revisions"}],"predecessor-version":[{"id":100836,"href":"https:\/\/vibromera.eu\/nb\/wp-json\/wp\/v2\/posts\/100667\/revisions\/100836"}],"wp:attachment":[{"href":"https:\/\/vibromera.eu\/nb\/wp-json\/wp\/v2\/media?parent=100667"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/vibromera.eu\/nb\/wp-json\/wp\/v2\/categories?post=100667"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/vibromera.eu\/nb\/wp-json\/wp\/v2\/tags?post=100667"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}

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.workflow-step:not(:last-child)::after{display:none}\n .workflow-step{border-radius:var(--radius-sm)!important;margin-bottom:8px}\n}\n<\/style>\n<\/head>\n<body>\n\n<div class=\"progress-bar\" id=\"progressBar\" style=\"width:0%\"><\/div>\n<button class=\"back-to-top\" id=\"backToTop\" onclick=\"window.scrollTo({top:0,behavior:'smooth'})\">\n <svg width=\"20\" height=\"20\" viewBox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2.5\" stroke-linecap=\"round\" stroke-linejoin=\"round\"><polyline points=\"18 15 12 9 6 15\"\/><\/svg>\n<\/button>\n\n<div class=\"page-wrapper\">\n\n\n<aside class=\"sidebar\">\n <div class=\"sidebar-logo\">VibroMera<\/div>\n <div class=\"sidebar-subtitle\">Technical Knowledge Base<\/div>\n <div class=\"toc-title\">Table of Contents<\/div>\n <ul class=\"toc-list\">\n <li><a href=\"#fundamentals\" data-section=\"fundamentals\">1. Electrical Fundamentals<\/a><\/li>\n <li><a href=\"#methods\" data-section=\"methods\">2. Diagnostic Methods<\/a><\/li>\n <li><a href=\"#stator\" data-section=\"stator\">3. Stator Defects<\/a><\/li>\n <li><a href=\"#stator-eccentricity\" data-section=\"stator-eccentricity\" class=\"toc-sub\">3.1 Stator Eccentricity<\/a><\/li>\n <li><a href=\"#loose-windings\" data-section=\"loose-windings\" class=\"toc-sub\">3.2 Loose Windings<\/a><\/li>\n <li><a href=\"#loose-cable\" data-section=\"loose-cable\" class=\"toc-sub\">3.3 Loose Power Cable<\/a><\/li>\n <li><a href=\"#shorted-laminations\" data-section=\"shorted-laminations\" class=\"toc-sub\">3.4 Shorted Laminations<\/a><\/li>\n <li><a href=\"#inter-turn\" data-section=\"inter-turn\" class=\"toc-sub\">3.5 Inter-Turn Short<\/a><\/li>\n <li><a href=\"#rotor\" data-section=\"rotor\">4. Rotor Defects<\/a><\/li>\n <li><a href=\"#broken-bars\" data-section=\"broken-bars\" class=\"toc-sub\">4.1 Broken Rotor Bars<\/a><\/li>\n <li><a href=\"#rotor-eccentricity\" data-section=\"rotor-eccentricity\" class=\"toc-sub\">4.2 Rotor Eccentricity<\/a><\/li>\n <li><a href=\"#rotor-bow\" data-section=\"rotor-bow\" class=\"toc-sub\">4.3 Thermal Rotor Bow<\/a><\/li>\n <li><a href=\"#em-field-shift\" data-section=\"em-field-shift\" class=\"toc-sub\">4.4 EM Field Displacement<\/a><\/li>\n <li><a href=\"#bearings-electrical\" data-section=\"bearings-electrical\">5. Bearing Electrical Defects<\/a><\/li>\n <li><a href=\"#vfd\" data-section=\"vfd\">6. VFD Effects<\/a><\/li>\n <li><a href=\"#differential\" data-section=\"differential\">7. Differential Diagnostics<\/a><\/li>\n <li><a href=\"#instrumentation\" data-section=\"instrumentation\">8. Instrumentation<\/a><\/li>\n <li><a href=\"#standards\" data-section=\"standards\">9. Normative References<\/a><\/li>\n <li><a href=\"#conclusion\" data-section=\"conclusion\">10. Conclusion<\/a><\/li>\n <\/ul>\n<\/aside>\n\n\n<main class=\"main-content\">\n\n\n<header class=\"hero\">\n <span class=\"hero-badge\">Spectral Vibration Analysis<\/span>\n <h1>Electric Motor Defects: Comprehensive Spectral Analysis<\/h1>\n <p class=\"hero-intro\">Electric motors consume approximately <strong>45% of all industrial electricity<\/strong> worldwide. According to EPRI studies, failures distribute as: <strong>~23% stator faults<\/strong>, <strong>~10% rotor defects<\/strong>, <strong>~41% bearing degradation<\/strong>, and <strong>~26% external factors<\/strong>. Many of these failure modes leave distinct fingerprints in the vibration spectrum \u2014 long before a catastrophic breakdown occurs.<\/p>\n <p class=\"hero-intro\">This article provides a comprehensive guide to identifying electric motor defects through spectral vibration analysis and complementary techniques: MCSA, ESA, and MCA.<\/p>\n <div class=\"hero-meta\">\n <span class=\"hero-meta-item\">\n <svg viewBox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\"><path d=\"M12 8v4l3 3\"\/><circle cx=\"12\" cy=\"12\" r=\"10\"\/><\/svg>\n 25 min read\n <\/span>\n <span class=\"hero-meta-item\">\n <svg viewBox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\"><path d=\"M4 19.5A2.5 2.5 0 0 1 6.5 17H20\"\/><path d=\"M6.5 2H20v20H6.5A2.5 2.5 0 0 1 4 19.5v-15A2.5 2.5 0 0 1 6.5 2z\"\/><\/svg>\n ISO 20816 \u00b7 IEC 60034 \u00b7 IEEE 1415\n <\/span>\n <span class=\"hero-meta-item\">\n <svg viewBox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\"><path d=\"M20 7h-9\"\/><path d=\"M14 17H5\"\/><circle cx=\"17\" cy=\"17\" r=\"3\"\/><circle cx=\"7\" cy=\"7\" r=\"3\"\/><\/svg>\n Balanset-1A\n <\/span>\n <\/div>\n<\/header>\n\n\n<div class=\"stat-row\">\n <div class=\"stat-card\"><div class=\"stat-number\">~23%<\/div><div class=\"stat-label\">Stator faults<\/div><\/div>\n <div class=\"stat-card\"><div class=\"stat-number\">~10%<\/div><div class=\"stat-label\">Rotor defects<\/div><\/div>\n <div class=\"stat-card\"><div class=\"stat-number\">~41%<\/div><div class=\"stat-label\">Bearing degradation<\/div><\/div>\n <div class=\"stat-card\"><div class=\"stat-number\">~26%<\/div><div class=\"stat-label\">External factors<\/div><\/div>\n<\/div>\n\n\n<h2 id=\"fundamentals\"><span class=\"section-num\">1.<\/span> Electrical Fundamentals for the Vibration Analyst<\/h2>\n\n<p>Before diagnosing motor defects from vibration spectra, it is essential to understand the key electrical frequencies that drive motor vibration.<\/p>\n\n<h3>1.1. Line Frequency (LF)<\/h3>\n<p>The AC supply frequency: <strong>50 Hz<\/strong> in most of Europe, Asia, Africa, and Russia; <strong>60 Hz<\/strong> in North America and parts of South America and Asia. All electromagnetic forces in the motor are derived from this frequency.<\/p>\n\n<h3>1.2. Twice Line Frequency (2\u00d7LF)<\/h3>\n<p>The <strong>dominant electromagnetic force frequency<\/strong> in AC motors. In a 50 Hz system, 2\u00d7LF = <strong>100 Hz<\/strong>; in a 60 Hz system, 2\u00d7LF = <strong>120 Hz<\/strong>. The magnetic attraction force between stator and rotor peaks twice per electrical cycle, making 2\u00d7LF the fundamental \"electrical vibration\" frequency of every AC motor.<\/p>\n\n<div class=\"formula\">2\u00d7LF = 2 \u00d7 f<sub>line<\/sub> = 100 Hz (50 Hz systems) | 120 Hz (60 Hz systems)<\/div>\n\n<h3>1.3. Synchronous Speed and Slip<\/h3>\n<p>The stator magnetic field rotates at synchronous speed:<\/p>\n<div class=\"formula\">N<sub>s<\/sub> = 120 \u00d7 f<sub>line<\/sub> \/ P (RPM)<\/div>\n<p>where <strong>P<\/strong> is the number of poles. An induction motor rotor always rotates slightly slower. This difference is <strong>slip<\/strong>:<\/p>\n<div class=\"formula\">s = (N<sub>s<\/sub> \u2212 N) \/ N<sub>s<\/sub><\/div>\n<p>Typical full-load slip for standard induction motors: <strong>1\u20135%<\/strong>. For a 2-pole motor at 50 Hz: N<sub>s<\/sub> = 3000 RPM, actual speed \u2248 2940\u20132970 RPM.<\/p>\n\n<h3>1.4. Pole Pass Frequency (F<sub>p<\/sub>)<\/h3>\n<p>The rate at which rotor poles \"slip past\" stator poles. The result is <strong>universal<\/strong> \u2014 independent of pole count:<\/p>\n<div class=\"formula\">F<sub>p<\/sub> = 2 \u00d7 s \u00d7 f<sub>line<\/sub> = 2 \u00d7 f<sub>s<\/sub> \u2014 independent of pole count P<\/div>\n<p>For a motor running at 50 Hz with 2% slip: F<sub>p<\/sub> = 2 \u00d7 0.02 \u00d7 50 = <strong>2 Hz<\/strong>. This frequency appears as characteristic sidebands in spectra of broken rotor bars.<\/p>\n\n<h3>1.5. Rotor Bar Pass Frequency<\/h3>\n<div class=\"formula\">f<sub>RBPF<\/sub> = R \u00d7 f<sub>rot<\/sub><\/div>\n<p>Where R is the number of rotor bars. This frequency and its sidebands become significant when rotor bars are damaged.<\/p>\n\n<h3>1.6. Key Frequency Reference Table<\/h3>\n<div class=\"table-wrap\">\n<table>\n<thead><tr><th>Symbol<\/th><th>Name<\/th><th>Formula<\/th><th>Example (50 Hz, 2-pole, 2% slip)<\/th><\/tr><\/thead>\n<tbody>\n<tr><td><code>LF<\/code><\/td><td>Line frequency<\/td><td>f<sub>line<\/sub><\/td><td>50 Hz<\/td><\/tr>\n<tr><td><code>2\u00d7LF<\/code><\/td><td>Twice line frequency<\/td><td>2 \u00d7 f<sub>line<\/sub><\/td><td>100 Hz<\/td><\/tr>\n<tr><td><code>f<sub>sync<\/sub><\/code><\/td><td>Synchronous frequency<\/td><td>2 \u00d7 f<sub>line<\/sub> \/ P<\/td><td>50 Hz (P=2) | 25 Hz (P=4)<\/td><\/tr>\n<tr><td><code>1X<\/code><\/td><td>Rotational frequency<\/td><td>(1 \u2212 s) \u00d7 f<sub>sync<\/sub><\/td><td>49 Hz (2940 RPM)<\/td><\/tr>\n<tr><td><code>F<sub>p<\/sub><\/code><\/td><td>Pole pass frequency<\/td><td>2 \u00d7 s \u00d7 f<sub>line<\/sub><\/td><td>2 Hz<\/td><\/tr>\n<tr><td><code>f<sub>RBPF<\/sub><\/code><\/td><td>Rotor bar pass freq.<\/td><td>R \u00d7 f<sub>rot<\/sub><\/td><td>16 \u00d7 49 = <strong>784 Hz<\/strong><\/td><\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n\n<div class=\"key-fact red\">\n <div class=\"key-fact-label\">Critical Note<\/div>\n <p>In a 50 Hz system, <code>2\u00d7LF = 100 Hz<\/code> and <code>2X \u2248 98 Hz<\/code> (for a 2-pole motor). These two peaks are only <strong>2 Hz apart<\/strong>. Spectral resolution of <strong>\u2264 0.5 Hz<\/strong> is required to separate them. Use <strong>record lengths of 4\u20138 s or more<\/strong>. Misidentifying 2X as 2\u00d7LF leads to fundamentally wrong diagnoses \u2014 confusing a mechanical defect with an electrical one. <em>This proximity is specific to 2-pole machines. For 4-pole: 2X \u2248 49 Hz \u2014 well separated from 2\u00d7LF = 100 Hz.<\/em><\/p>\n<\/div>\n\n\n<div class=\"infographic\">\n<div class=\"infographic-title\">Motor Cross-Section: Key Components and Air Gap<\/div>\n<svg viewBox=\"0 0 620 380\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" style=\"max-width:100%;\" role=\"img\">\n <rect x=\"0\" y=\"0\" width=\"620\" height=\"380\" rx=\"12\" fill=\"#faf8f5\"\/>\n <circle cx=\"210\" cy=\"195\" r=\"140\" fill=\"#e8e3da\" stroke=\"#2a5a8c\" stroke-width=\"2.5\"\/>\n <circle cx=\"210\" cy=\"195\" r=\"108\" fill=\"#faf8f5\" stroke=\"#2a5a8c\" stroke-width=\"1.5\"\/>\n <g fill=\"#eaf5f5\" stroke=\"#2a7a7a\" stroke-width=\"1\">\n <rect x=\"196\" y=\"56\" width=\"28\" height=\"16\" rx=\"3\"\/>\n <rect x=\"196\" y=\"318\" width=\"28\" height=\"16\" rx=\"3\"\/>\n <rect x=\"78\" y=\"122\" width=\"16\" height=\"24\" rx=\"3\" transform=\"rotate(-30 88 134)\"\/>\n <rect x=\"322\" y=\"122\" width=\"16\" height=\"24\" rx=\"3\" transform=\"rotate(30 332 134)\"\/>\n <rect x=\"78\" y=\"240\" width=\"16\" height=\"24\" rx=\"3\" transform=\"rotate(30 88 252)\"\/>\n <rect x=\"322\" y=\"240\" width=\"16\" height=\"24\" rx=\"3\" transform=\"rotate(-30 332 252)\"\/>\n <rect x=\"148\" y=\"60\" width=\"16\" height=\"22\" rx=\"3\" transform=\"rotate(-60 156 71)\"\/>\n <rect x=\"256\" y=\"60\" width=\"16\" height=\"22\" rx=\"3\" transform=\"rotate(60 264 71)\"\/>\n <rect x=\"60\" y=\"178\" width=\"16\" height=\"22\" rx=\"3\"\/>\n <rect x=\"344\" y=\"178\" width=\"16\" height=\"22\" rx=\"3\"\/>\n <rect x=\"148\" y=\"308\" width=\"16\" height=\"22\" rx=\"3\" transform=\"rotate(60 156 319)\"\/>\n <rect x=\"256\" y=\"308\" width=\"16\" height=\"22\" rx=\"3\" transform=\"rotate(-60 264 319)\"\/>\n <\/g>\n <circle cx=\"210\" cy=\"195\" r=\"90\" fill=\"none\" stroke=\"#9a6b12\" stroke-width=\"3\" stroke-dasharray=\"7,4\"\/>\n <circle cx=\"210\" cy=\"195\" r=\"82\" fill=\"#e8e3da\" stroke=\"#6b4a8c\" stroke-width=\"2\"\/>\n <g fill=\"#d9d3c7\" stroke=\"#7a756b\" stroke-width=\"0.7\">\n <circle cx=\"210\" cy=\"127\" r=\"5\"\/><circle cx=\"247\" cy=\"131\" r=\"5\"\/><circle cx=\"274\" cy=\"148\" r=\"5\"\/><circle cx=\"289\" cy=\"173\" r=\"5\"\/>\n <circle cx=\"289\" cy=\"200\" r=\"5\"\/><circle cx=\"278\" cy=\"227\" r=\"5\"\/><circle cx=\"256\" cy=\"248\" r=\"5\"\/><circle cx=\"227\" cy=\"259\" r=\"5\"\/>\n <circle cx=\"193\" cy=\"259\" r=\"5\"\/><circle cx=\"164\" cy=\"248\" r=\"5\"\/><circle cx=\"142\" cy=\"227\" r=\"5\"\/><circle cx=\"131\" cy=\"200\" r=\"5\"\/>\n <circle cx=\"131\" cy=\"173\" r=\"5\"\/><circle cx=\"142\" cy=\"148\" r=\"5\"\/><circle cx=\"164\" cy=\"131\" r=\"5\"\/><circle cx=\"185\" cy=\"127\" r=\"5\"\/>\n <\/g>\n <circle cx=\"210\" cy=\"195\" r=\"26\" fill=\"#e8e3da\" stroke=\"#7a756b\" stroke-width=\"2\"\/>\n <text x=\"210\" y=\"34\" fill=\"#2a5a8c\" font-size=\"14\" font-weight=\"700\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">STATOR<\/text>\n <line x1=\"232\" y1=\"64\" x2=\"268\" y2=\"50\" stroke=\"#2a7a7a\" stroke-width=\"1\"\/>\n <text x=\"272\" y=\"50\" fill=\"#2a7a7a\" font-size=\"11\" font-weight=\"600\" font-family=\"Source Sans 3,sans-serif\">Winding slots<\/text>\n <line x1=\"293\" y1=\"135\" x2=\"345\" y2=\"108\" stroke=\"#9a6b12\" stroke-width=\"1.2\"\/>\n <circle cx=\"293\" cy=\"135\" r=\"2.5\" fill=\"#9a6b12\"\/>\n <text x=\"350\" y=\"102\" fill=\"#9a6b12\" font-size=\"13\" font-weight=\"700\" font-family=\"Source Sans 3,sans-serif\">AIR GAP<\/text>\n <text x=\"350\" y=\"118\" fill=\"#9a6b12\" font-size=\"10\" font-family=\"Source Sans 3,sans-serif\">(0.25 \u2013 2 mm typical)<\/text>\n <text x=\"350\" y=\"133\" fill=\"#9a6b12\" font-size=\"10\" font-family=\"Source Sans 3,sans-serif\">(critical parameter)<\/text>\n <text x=\"210\" y=\"188\" fill=\"#3d3b36\" font-size=\"15\" font-weight=\"700\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">ROTOR<\/text>\n <line x1=\"240\" y1=\"260\" x2=\"310\" y2=\"280\" stroke=\"#7a756b\" stroke-width=\"1\"\/>\n <circle cx=\"240\" cy=\"260\" r=\"2.5\" fill=\"#7a756b\"\/>\n <text x=\"315\" y=\"276\" fill=\"#7a756b\" font-size=\"11\" font-weight=\"600\" font-family=\"Source Sans 3,sans-serif\">Rotor bars (shown: 16)<\/text>\n <text x=\"315\" y=\"291\" fill=\"#9e9889\" font-size=\"10\" font-family=\"Source Sans 3,sans-serif\">carry induced current<\/text>\n <text x=\"210\" y=\"200\" fill=\"#7a756b\" font-size=\"10\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">Shaft<\/text>\n <line x1=\"105\" y1=\"170\" x2=\"58\" y2=\"148\" stroke=\"#2a5a8c\" stroke-width=\"1\"\/>\n <circle cx=\"105\" cy=\"170\" r=\"2.5\" fill=\"#2a5a8c\"\/>\n <text x=\"14\" y=\"142\" fill=\"#2a5a8c\" font-size=\"11\" font-weight=\"600\" font-family=\"Source Sans 3,sans-serif\">Stator bore<\/text>\n <text x=\"14\" y=\"156\" fill=\"#9e9889\" font-size=\"9.5\" font-family=\"Source Sans 3,sans-serif\">(laminated core)<\/text>\n \n <g transform=\"translate(405,130)\">\n <rect x=\"0\" y=\"0\" width=\"208\" height=\"222\" rx=\"8\" fill=\"#f0ece5\" stroke=\"#d9d3c7\" stroke-width=\"1.5\"\/>\n <text x=\"104\" y=\"22\" fill=\"#2a5a8c\" font-size=\"13\" font-weight=\"700\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">Key Frequencies<\/text>\n <line x1=\"12\" y1=\"32\" x2=\"196\" y2=\"32\" stroke=\"#d9d3c7\" stroke-width=\"1\"\/>\n <text x=\"18\" y=\"52\" fill=\"#2a5a8c\" font-size=\"11\" font-family=\"Source Sans 3,sans-serif\">\u25b8 Stator \u2192 2\u00d7LF<\/text>\n <text x=\"18\" y=\"72\" fill=\"#9a6b12\" font-size=\"11\" font-family=\"Source Sans 3,sans-serif\">\u25b8 Air gap \u2192 2\u00d7LF \u00b1 1X<\/text>\n <text x=\"18\" y=\"92\" fill=\"#6b4a8c\" font-size=\"11\" font-family=\"Source Sans 3,sans-serif\">\u25b8 Broken bars \u2192 1X \u00b1 Fp<\/text>\n <text x=\"30\" y=\"107\" fill=\"#7a756b\" font-size=\"9.5\" font-family=\"Source Sans 3,sans-serif\">MCSA: LF \u00b1 Fp<\/text>\n <text x=\"18\" y=\"127\" fill=\"#7a756b\" font-size=\"11\" font-family=\"Source Sans 3,sans-serif\">\u25b8 Bar pass \u2192 R \u00d7 frot<\/text>\n <text x=\"18\" y=\"147\" fill=\"#2d6b30\" font-size=\"11\" font-family=\"Source Sans 3,sans-serif\">\u25b8 Mechanical \u2192 1X, 2X, nX<\/text>\n <text x=\"18\" y=\"167\" fill=\"#b8372b\" font-size=\"11\" font-family=\"Source Sans 3,sans-serif\">\u25b8 Axial shift \u2192 2\u00d7LF \u00b1 1X (ax.)<\/text>\n <line x1=\"12\" y1=\"178\" x2=\"196\" y2=\"178\" stroke=\"#d9d3c7\" stroke-width=\"1\"\/>\n <text x=\"18\" y=\"196\" fill=\"#7a756b\" font-size=\"10\" font-family=\"Source Sans 3,sans-serif\">At 50 Hz: 2\u00d7LF = 100 Hz<\/text>\n <text x=\"18\" y=\"212\" fill=\"#9e9889\" font-size=\"9\" font-style=\"italic\" font-family=\"Source Sans 3,sans-serif\">\u00b1 = sidebands (modulation)<\/text>\n <\/g>\n <text x=\"210\" y=\"374\" fill=\"#9e9889\" font-size=\"9.5\" font-style=\"italic\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">Schematic \u2014 not to scale. Actual slot\/bar count depends on motor design.<\/text>\n<\/svg>\n<\/div>\n<p class=\"infographic-note\"><span class=\"legend-blue legend-badge\">Stator<\/span><span class=\"legend-purple legend-badge\">Rotor<\/span><span class=\"legend-teal legend-badge\">Windings<\/span><span class=\"legend-yellow legend-badge\">Air gap<\/span><span class=\"legend-green legend-badge\">Mechanical<\/span><span class=\"legend-red legend-badge\">Axial<\/span> Any air-gap distortion directly changes magnetic pull, and that immediately changes the vibration pattern. Symbol \u00b1 denotes sidebands (modulation).<\/p>\n\n\n\n<h2 id=\"methods\"><span class=\"section-num\">2.<\/span> Overview of Diagnostic Methods<\/h2>\n\n<p>No single technique can detect all electric motor defects. A robust diagnostic program combines multiple complementary methods:<\/p>\n\n\n<div class=\"infographic\">\n<div class=\"infographic-title\">Electric Motor Diagnostic Methods<\/div>\n<svg viewBox=\"0 0 780 320\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" style=\"max-width:100%;\" role=\"img\">\n <rect x=\"0\" y=\"0\" width=\"780\" height=\"320\" rx=\"12\" fill=\"#faf8f5\"\/>\n <circle cx=\"390\" cy=\"160\" r=\"50\" fill=\"#e8e3da\" stroke=\"#2a5a8c\" stroke-width=\"2\"\/>\n <text x=\"390\" y=\"155\" fill=\"#3d3b36\" font-size=\"12\" font-weight=\"600\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">ELECTRIC<\/text>\n <text x=\"390\" y=\"172\" fill=\"#3d3b36\" font-size=\"12\" font-weight=\"600\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">MOTOR<\/text>\n \n <g transform=\"translate(40,30)\">\n <rect x=\"0\" y=\"0\" width=\"175\" height=\"90\" rx=\"8\" fill=\"var(--card)\" stroke=\"#2a5a8c\" stroke-width=\"1.5\"\/>\n <text x=\"88\" y=\"22\" fill=\"#2a5a8c\" font-size=\"12\" font-weight=\"600\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">1. Vibration Analysis<\/text>\n <text x=\"88\" y=\"40\" fill=\"#7a756b\" font-size=\"9.5\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">Spectra & time waveform<\/text>\n <text x=\"88\" y=\"55\" fill=\"#7a756b\" font-size=\"9.5\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">1X, 2X, 2\u00d7LF, harmonics<\/text>\n <text x=\"88\" y=\"70\" fill=\"#2d6b30\" font-size=\"9.5\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">\u2713 Mechanical + some electrical<\/text>\n <text x=\"88\" y=\"84\" fill=\"#b8372b\" font-size=\"9\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">\u2717 Cannot detect all electrical faults<\/text>\n <\/g>\n <line x1=\"215\" y1=\"90\" x2=\"345\" y2=\"140\" stroke=\"#2a5a8c\" stroke-width=\"1\" stroke-dasharray=\"4,3\"\/>\n \n <g transform=\"translate(40,190)\">\n <rect x=\"0\" y=\"0\" width=\"175\" height=\"90\" rx=\"8\" fill=\"var(--card)\" stroke=\"#9a6b12\" stroke-width=\"1.5\"\/>\n <text x=\"88\" y=\"22\" fill=\"#9a6b12\" font-size=\"12\" font-weight=\"600\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">2. MCSA<\/text>\n <text x=\"88\" y=\"38\" fill=\"#7a756b\" font-size=\"9.5\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">Motor Current Signature<\/text>\n <text x=\"88\" y=\"53\" fill=\"#7a756b\" font-size=\"9.5\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">Analysis \u2014 current clamp<\/text>\n <text x=\"88\" y=\"70\" fill=\"#2d6b30\" font-size=\"9.5\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">\u2713 Broken rotor bars, eccentricity<\/text>\n <text x=\"88\" y=\"84\" fill=\"#2d6b30\" font-size=\"9\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">\u2713 Online, non-invasive<\/text>\n <\/g>\n <line x1=\"215\" y1=\"240\" x2=\"345\" y2=\"180\" stroke=\"#9a6b12\" stroke-width=\"1\" stroke-dasharray=\"4,3\"\/>\n \n <g transform=\"translate(560,30)\">\n <rect x=\"0\" y=\"0\" width=\"175\" height=\"90\" rx=\"8\" fill=\"var(--card)\" stroke=\"#2d6b30\" stroke-width=\"1.5\"\/>\n <text x=\"88\" y=\"22\" fill=\"#2d6b30\" font-size=\"12\" font-weight=\"600\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">3. ESA<\/text>\n <text x=\"88\" y=\"38\" fill=\"#7a756b\" font-size=\"9.5\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">Electrical Signature Analysis<\/text>\n <text x=\"88\" y=\"53\" fill=\"#7a756b\" font-size=\"9.5\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">Voltage + current spectra<\/text>\n <text x=\"88\" y=\"70\" fill=\"#2d6b30\" font-size=\"9.5\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">\u2713 Supply quality, stator faults<\/text>\n <text x=\"88\" y=\"84\" fill=\"#2d6b30\" font-size=\"9\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">\u2713 Online, at MCC<\/text>\n <\/g>\n <line x1=\"560\" y1=\"90\" x2=\"435\" y2=\"140\" stroke=\"#2d6b30\" stroke-width=\"1\" stroke-dasharray=\"4,3\"\/>\n \n <g transform=\"translate(560,190)\">\n <rect x=\"0\" y=\"0\" width=\"175\" height=\"90\" rx=\"8\" fill=\"var(--card)\" stroke=\"#6b4a8c\" stroke-width=\"1.5\"\/>\n <text x=\"88\" y=\"22\" fill=\"#6b4a8c\" font-size=\"12\" font-weight=\"600\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">4. MCA<\/text>\n <text x=\"88\" y=\"38\" fill=\"#7a756b\" font-size=\"9.5\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">Motor Circuit Analysis<\/text>\n <text x=\"88\" y=\"53\" fill=\"#7a756b\" font-size=\"9.5\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">Impedance, resistance<\/text>\n <text x=\"88\" y=\"70\" fill=\"#2d6b30\" font-size=\"9.5\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">\u2713 Insulation, turn-to-turn shorts<\/text>\n <text x=\"88\" y=\"84\" fill=\"#b8372b\" font-size=\"9\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">\u2717 Offline only (motor stopped)<\/text>\n <\/g>\n <line x1=\"560\" y1=\"240\" x2=\"435\" y2=\"180\" stroke=\"#6b4a8c\" stroke-width=\"1\" stroke-dasharray=\"4,3\"\/>\n \n <g transform=\"translate(303,265)\">\n <rect x=\"0\" y=\"0\" width=\"175\" height=\"48\" rx=\"8\" fill=\"var(--card)\" stroke=\"#b8372b\" stroke-width=\"1.5\"\/>\n <text x=\"88\" y=\"20\" fill=\"#b8372b\" font-size=\"12\" font-weight=\"600\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">5. Thermography<\/text>\n <text x=\"88\" y=\"38\" fill=\"#7a756b\" font-size=\"9.5\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">Stator temp + bearing temp monitoring<\/text>\n <\/g>\n <line x1=\"390\" y1=\"210\" x2=\"390\" y2=\"265\" stroke=\"#b8372b\" stroke-width=\"1\" stroke-dasharray=\"4,3\"\/>\n<\/svg>\n<\/div>\n<p class=\"infographic-note\"><span class=\"legend-blue legend-badge\">Vibration<\/span><span class=\"legend-yellow legend-badge\">MCSA<\/span><span class=\"legend-green legend-badge\">ESA<\/span><span class=\"legend-purple legend-badge\">MCA<\/span><span class=\"legend-red legend-badge\">Thermography<\/span> No single method gives full coverage. A combined diagnostic approach is strongly recommended.<\/p>\n\n<h3>2.1. Vibration Spectral Analysis<\/h3>\n<p>The primary tool for most rotating equipment diagnostics. Accelerometers on bearing housings capture spectra revealing mechanical defects (unbalance, misalignment, bearing wear) and some electrical defects (uneven air gap, loose windings). However, <strong>vibration analysis alone cannot detect all motor electrical faults<\/strong>.<\/p>\n\n<h3>2.2. Motor Current Signature Analysis (MCSA)<\/h3>\n<p>A current clamp on one phase captures the current spectrum. Broken rotor bars produce sidebands at <code>LF \u00b1 F<sub>p<\/sub><\/code>. MCSA is performed online and is completely non-invasive.<\/p>\n\n<h3>2.3. Electrical Signature Analysis (ESA)<\/h3>\n<p>Analyzes both voltage and current spectra simultaneously at the MCC. Detects supply voltage asymmetry, harmonic distortion, and power quality issues.<\/p>\n\n<h3>2.4. Motor Circuit Analysis (MCA)<\/h3>\n<p>An <strong>offline<\/strong> test measuring phase-to-phase resistance, inductance, impedance, and insulation resistance. Essential during maintenance shutdowns.<\/p>\n\n<h3>2.5. Temperature Monitoring<\/h3>\n<p>Stator winding temperature and bearing temperature trending provide early warning of overload, cooling problems, and insulation degradation.<\/p>\n\n<div class=\"tip\">\n<p><strong>Practical approach.<\/strong> For a comprehensive motor diagnostic program, combine at minimum: (1) vibration spectral analysis, (2) MCSA with current clamp, and (3) regular conversations with electricians and motor repair personnel \u2014 their hands-on experience often reveals critical context that instruments alone cannot provide.<\/p>\n<\/div>\n\n\n\n<h2 id=\"stator\"><span class=\"section-num\">3.<\/span> Stator Defects<\/h2>\n\n<p>Stator defects are responsible for approximately <strong>23\u201337% of all motor failures<\/strong>. The stator is the stationary part containing the laminated iron core and windings. Defects produce vibration primarily at <strong>2\u00d7LF (100 Hz \/ 120 Hz)<\/strong> and its multiples.<\/p>\n\n<h3 id=\"stator-eccentricity\">3.1. Stator Eccentricity \u2014 Uneven Air Gap<\/h3>\n\n<p>The air gap between rotor and stator is typically <strong>0.25\u20132 mm<\/strong>. Even a 10% variation creates measurable electromagnetic force imbalance.<\/p>\n\n<h4>Causes<\/h4>\n<ul>\n <li><strong>Soft foot<\/strong> \u2014 the most common cause<\/li>\n <li>Worn or damaged bearing housings<\/li>\n <li>Frame deformation from improper transport or installation<\/li>\n <li>Thermal distortion under operating conditions<\/li>\n <li>Poor manufacturing tolerances<\/li>\n<\/ul>\n\n<h4>Spectral Signature<\/h4>\n<ul>\n <li><strong>Typically dominant 2\u00d7LF<\/strong> in the radial velocity spectrum<\/li>\n <li>Often accompanied by minor increase of <strong>1X<\/strong> and <strong>2X<\/strong> due to unbalanced magnetic pull (UMP)<\/li>\n <li>Static eccentricity: 2\u00d7LF dominates with little modulation<\/li>\n <li>Dynamic component: sidebands at <strong>2\u00d7LF \u00b1 1X<\/strong> may appear<\/li>\n<\/ul>\n\n<div class=\"formula\">Spectrum: prominent <strong>2\u00d7LF<\/strong> + minor <strong>1X<\/strong> and <strong>2X<\/strong> increase (radial direction)<\/div>\n\n<h4>Severity Assessment<\/h4>\n<div class=\"table-wrap\">\n<table>\n<thead><tr><th>2\u00d7LF amplitude (velocity RMS)<\/th><th>Assessment<\/th><\/tr><\/thead>\n<tbody>\n<tr><td>< 1 mm\/s<\/td><td>Normal for most motors<\/td><\/tr>\n<tr><td>1\u20133 mm\/s<\/td><td>Monitor \u2014 check soft foot, bearing clearance<\/td><\/tr>\n<tr><td>3\u20136 mm\/s<\/td><td>Alert \u2014 investigate and plan correction<\/td><\/tr>\n<tr><td>> 6 mm\/s<\/td><td>Danger \u2014 immediate action required<\/td><\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<p><em>Note: These are illustrative guidelines, not a formal standard. Always compare against the machine's own baseline.<\/em><\/p>\n\n<h4>Confirmation Test<\/h4>\n<p><strong>Power-off test<\/strong> (snap test): While monitoring vibration, de-energize the motor. If the 2\u00d7LF peak <strong>drops sharply<\/strong> \u2014 within seconds, much faster than mechanical coastdown \u2014 the source is electromagnetic.<\/p>\n\n<div class=\"key-fact warn\">\n <div class=\"key-fact-label\">Important<\/div>\n <p>Do not confuse stator eccentricity with misalignment. Both can produce elevated 2X. The key: 2\u00d7LF at exactly 100.00 Hz is electrical; 2X tracks rotor speed and shifts if speed changes. Ensure spectral resolution \u2264 0.5 Hz.<\/p>\n<\/div>\n\n\n<h3 id=\"loose-windings\">3.2. Loose Stator Windings<\/h3>\n\n<p>Stator windings are subjected to electromagnetic forces at 2\u00d7LF during every operating cycle. Over years, mechanical fixation (epoxy, varnish, wedges) can degrade. Loose windings vibrate at 2\u00d7LF with increasing amplitude, accelerating insulation wear through fretting.<\/p>\n\n<h4>Spectral Signature<\/h4>\n<div class=\"formula\">Elevated <strong>2\u00d7LF<\/strong> \u2014 often with increase over time (trending)<\/div>\n<ul>\n <li>Predominantly radial vibration<\/li>\n <li>2\u00d7LF may be less stable \u2014 slight amplitude fluctuations<\/li>\n <li>Severe cases: harmonics at 4\u00d7LF, 6\u00d7LF<\/li>\n<\/ul>\n\n<h4>Consequences<\/h4>\n<p>This is <strong>destructive for winding insulation<\/strong> \u2014 leads to accelerated degradation, unpredictable ground faults, and complete stator failure requiring rewind.<\/p>\n\n\n<h3 id=\"loose-cable\">3.3. Loose Power Cable \u2014 Phase Asymmetry<\/h3>\n\n<p>A poor contact creates resistance asymmetry. Even <strong>1% voltage asymmetry<\/strong> causes approximately <strong>6\u201310% current asymmetry<\/strong>. The unbalanced currents create a backward-rotating magnetic field component.<\/p>\n\n<h4>Spectral Signature<\/h4>\n<div class=\"formula\">Elevated <strong>2\u00d7LF<\/strong> \u2014 primary indicator of phase asymmetry<\/div>\n<ul>\n <li>2\u00d7LF amplitude increases due to unbalanced magnetic pull<\/li>\n <li>In some cases, <strong>sidebands near \u00b1\u2153\u00d7LF<\/strong> (~16.7 Hz in 50 Hz systems) around the 2\u00d7LF peak<\/li>\n <li>In current spectrum (MCSA): elevated negative-sequence current<\/li>\n<\/ul>\n\n<h4>Practical Checks<\/h4>\n<ul>\n <li>Check all cable terminations, bus bar connections, contactor contacts<\/li>\n <li>Measure phase-to-phase resistance \u2014 within 1% of each other<\/li>\n <li>Measure supply voltage on all three phases \u2014 asymmetry should not exceed 1%<\/li>\n <li>IR thermography of cable termination box<\/li>\n<\/ul>\n\n\n<h3 id=\"shorted-laminations\">3.4. Shorted Stator Laminations<\/h3>\n\n<p>Damage to inter-lamination insulation allows eddy currents to circulate, creating localized hot spots. Not always detectable in vibration spectra \u2014 <strong>IR thermography is the primary detection method<\/strong>. Offline: electromagnetic core test (EL-CID test).<\/p>\n\n\n<h3 id=\"inter-turn\">3.5. Inter-Turn Short Circuit<\/h3>\n\n<p>A turn-to-turn short creates a localized circulating current loop, reducing effective turns in the affected coil. Produces increased <strong>2\u00d7LF<\/strong>, elevated 3rd harmonic of LF in current, and phase current asymmetry. Best detected via MCA surge test offline.<\/p>\n\n\n<div class=\"infographic\">\n<div class=\"infographic-title\">Stator Defects \u2014 Spectral Signatures Summary<\/div>\n<svg viewBox=\"0 0 820 480\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" style=\"max-width:100%;\" role=\"img\">\n <rect x=\"0\" y=\"0\" width=\"820\" height=\"480\" rx=\"12\" fill=\"#faf8f5\"\/>\n \n <g transform=\"translate(580,14)\">\n <rect x=\"0\" y=\"0\" width=\"220\" height=\"76\" rx=\"6\" fill=\"#f0ece5\" stroke=\"#d9d3c7\" stroke-width=\"1.5\"\/>\n <text x=\"110\" y=\"18\" fill=\"#2a5a8c\" font-size=\"12\" font-weight=\"700\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">Legend<\/text>\n <line x1=\"10\" y1=\"25\" x2=\"210\" y2=\"25\" stroke=\"#d9d3c7\" stroke-width=\"1\"\/>\n <rect x=\"14\" y=\"34\" width=\"16\" height=\"10\" rx=\"2\" fill=\"#b8372b\"\/><text x=\"36\" y=\"44\" fill=\"#3d3b36\" font-size=\"11\" font-family=\"Source Sans 3,sans-serif\">2\u00d7LF peak (100 Hz) \u2014 electrical<\/text>\n <rect x=\"14\" y=\"50\" width=\"16\" height=\"10\" rx=\"2\" fill=\"#2d6b30\"\/><text x=\"36\" y=\"60\" fill=\"#3d3b36\" font-size=\"11\" font-family=\"Source Sans 3,sans-serif\">1X \/ 2X peaks \u2014 mechanical<\/text>\n <rect x=\"14\" y=\"66\" width=\"16\" height=\"10\" rx=\"2\" fill=\"#9a6b12\"\/><text x=\"36\" y=\"76\" fill=\"#3d3b36\" font-size=\"11\" font-family=\"Source Sans 3,sans-serif\">Sidebands (modulation)<\/text>\n <\/g>\n\n \n <text x=\"40\" y=\"30\" fill=\"#2a5a8c\" font-size=\"14\" font-weight=\"700\" font-family=\"Source Sans 3,sans-serif\">A. Stator eccentricity \/ Uneven air gap (\u00a73.1)<\/text>\n <text x=\"22\" y=\"138\" fill=\"#7a756b\" font-size=\"10\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\" transform=\"rotate(-90 22 138)\">Amplitude<\/text>\n <line x1=\"55\" y1=\"210\" x2=\"555\" y2=\"210\" stroke=\"#d9d3c7\" stroke-width=\"1.5\"\/>\n <line x1=\"55\" y1=\"45\" x2=\"55\" y2=\"210\" stroke=\"#d9d3c7\" stroke-width=\"1\"\/>\n <line x1=\"56\" y1=\"205\" x2=\"554\" y2=\"205\" stroke=\"#e8e3da\" stroke-width=\"1\" stroke-dasharray=\"2,4\"\/>\n \n <rect x=\"143\" y=\"168\" width=\"6\" height=\"37\" rx=\"2\" fill=\"#2d6b30\" opacity=\"0.8\"\/>\n <text x=\"146\" y=\"162\" fill=\"#2d6b30\" font-size=\"11\" font-weight=\"600\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">1X<\/text>\n \n <rect x=\"333\" y=\"156\" width=\"6\" height=\"49\" rx=\"2\" fill=\"#2d6b30\" opacity=\"0.8\"\/>\n <text x=\"336\" y=\"148\" fill=\"#2d6b30\" font-size=\"11\" font-weight=\"600\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">2X<\/text>\n \n <rect x=\"355\" y=\"52\" width=\"8\" height=\"153\" rx=\"2\" fill=\"#b8372b\" opacity=\"0.95\"\/>\n <text x=\"359\" y=\"46\" fill=\"#b8372b\" font-size=\"12\" font-weight=\"700\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">2\u00d7LF<\/text>\n \n <line x1=\"146\" y1=\"210\" x2=\"146\" y2=\"217\" stroke=\"#7a756b\" stroke-width=\"1\"\/><text x=\"146\" y=\"230\" fill=\"#7a756b\" font-size=\"10\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">49 Hz<\/text>\n <line x1=\"336\" y1=\"210\" x2=\"336\" y2=\"217\" stroke=\"#7a756b\" stroke-width=\"1\"\/><text x=\"326\" y=\"230\" fill=\"#7a756b\" font-size=\"10\" text-anchor=\"end\" font-family=\"Source Sans 3,sans-serif\">98<\/text>\n <line x1=\"359\" y1=\"210\" x2=\"359\" y2=\"217\" stroke=\"#7a756b\" stroke-width=\"1\"\/><text x=\"370\" y=\"230\" fill=\"#b8372b\" font-size=\"10\" font-family=\"Source Sans 3,sans-serif\">100 Hz<\/text>\n \n <line x1=\"339\" y1=\"240\" x2=\"356\" y2=\"240\" stroke=\"#7a756b\" stroke-width=\"1\"\/>\n <line x1=\"339\" y1=\"237\" x2=\"339\" y2=\"243\" stroke=\"#7a756b\" stroke-width=\"1\"\/>\n <line x1=\"356\" y1=\"237\" x2=\"356\" y2=\"243\" stroke=\"#7a756b\" stroke-width=\"1\"\/>\n <text x=\"348\" y=\"254\" fill=\"#7a756b\" font-size=\"9\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">2 Hz gap!<\/text>\n <text x=\"348\" y=\"266\" fill=\"#9e9889\" font-size=\"8.5\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">(need \u22640.5 Hz res.)<\/text>\n \n <line x1=\"380\" y1=\"72\" x2=\"430\" y2=\"62\" stroke=\"#b8372b\" stroke-width=\"1\"\/>\n <text x=\"435\" y=\"60\" fill=\"#b8372b\" font-size=\"11\" font-weight=\"600\" font-family=\"Source Sans 3,sans-serif\">2\u00d7LF DOMINANT<\/text>\n <text x=\"435\" y=\"76\" fill=\"#7a756b\" font-size=\"10\" font-family=\"Source Sans 3,sans-serif\">Radial direction<\/text>\n <text x=\"435\" y=\"92\" fill=\"#7a756b\" font-size=\"10\" font-family=\"Source Sans 3,sans-serif\">Vanishes on power-off<\/text>\n\n \n <line x1=\"20\" y1=\"280\" x2=\"800\" y2=\"280\" stroke=\"#d9d3c7\" stroke-width=\"1\" stroke-dasharray=\"4,4\"\/>\n <text x=\"40\" y=\"306\" fill=\"#9a6b12\" font-size=\"14\" font-weight=\"700\" font-family=\"Source Sans 3,sans-serif\">B. Loose power cable \/ Phase asymmetry (\u00a73.3)<\/text>\n <text x=\"22\" y=\"396\" fill=\"#7a756b\" font-size=\"10\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\" transform=\"rotate(-90 22 396)\">Amplitude<\/text>\n <line x1=\"55\" y1=\"450\" x2=\"730\" y2=\"450\" stroke=\"#d9d3c7\" stroke-width=\"1.5\"\/>\n <line x1=\"55\" y1=\"310\" x2=\"55\" y2=\"450\" stroke=\"#d9d3c7\" stroke-width=\"1\"\/>\n <line x1=\"56\" y1=\"445\" x2=\"729\" y2=\"445\" stroke=\"#e8e3da\" stroke-width=\"1\" stroke-dasharray=\"2,4\"\/>\n \n <rect x=\"253\" y=\"375\" width=\"6\" height=\"70\" rx=\"2\" fill=\"#9a6b12\" opacity=\"0.85\"\/>\n <text x=\"256\" y=\"368\" fill=\"#9a6b12\" font-size=\"11\" font-weight=\"600\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">83 Hz<\/text>\n \n <rect x=\"356\" y=\"318\" width=\"8\" height=\"127\" rx=\"2\" fill=\"#b8372b\" opacity=\"0.95\"\/>\n <text x=\"360\" y=\"312\" fill=\"#b8372b\" font-size=\"12\" font-weight=\"700\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">2\u00d7LF<\/text>\n \n <rect x=\"460\" y=\"375\" width=\"6\" height=\"70\" rx=\"2\" fill=\"#9a6b12\" opacity=\"0.85\"\/>\n <text x=\"463\" y=\"368\" fill=\"#9a6b12\" font-size=\"11\" font-weight=\"600\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">117 Hz<\/text>\n \n <path d=\"M256,363 L256,352 L360,340 L463,352 L463,363\" stroke=\"#9a6b12\" stroke-width=\"1.2\" fill=\"none\"\/>\n <text x=\"310\" y=\"347\" fill=\"#9a6b12\" font-size=\"10\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">\u2212\u2153LF<\/text>\n <text x=\"415\" y=\"347\" fill=\"#9a6b12\" font-size=\"10\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">+\u2153LF<\/text>\n <text x=\"360\" y=\"336\" fill=\"#9a6b12\" font-size=\"11\" font-weight=\"600\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">\u00b1 \u2153\u00d7LF sidebands (16.7 Hz)<\/text>\n \n <line x1=\"256\" y1=\"450\" x2=\"256\" y2=\"457\" stroke=\"#7a756b\" stroke-width=\"1\"\/><text x=\"256\" y=\"470\" fill=\"#7a756b\" font-size=\"10\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">83 Hz<\/text>\n <line x1=\"360\" y1=\"450\" x2=\"360\" y2=\"457\" stroke=\"#7a756b\" stroke-width=\"1\"\/><text x=\"360\" y=\"470\" fill=\"#b8372b\" font-size=\"10\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">100 Hz (2\u00d7LF)<\/text>\n <line x1=\"463\" y1=\"450\" x2=\"463\" y2=\"457\" stroke=\"#7a756b\" stroke-width=\"1\"\/><text x=\"463\" y=\"470\" fill=\"#7a756b\" font-size=\"10\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">117 Hz<\/text>\n \n <line x1=\"378\" y1=\"338\" x2=\"520\" y2=\"328\" stroke=\"#b8372b\" stroke-width=\"1\"\/>\n <text x=\"525\" y=\"326\" fill=\"#b8372b\" font-size=\"11\" font-weight=\"600\" font-family=\"Source Sans 3,sans-serif\">2\u00d7LF elevated<\/text>\n <text x=\"525\" y=\"342\" fill=\"#7a756b\" font-size=\"10\" font-family=\"Source Sans 3,sans-serif\">Phase resistance asymmetry<\/text>\n <text x=\"525\" y=\"358\" fill=\"#7a756b\" font-size=\"10\" font-family=\"Source Sans 3,sans-serif\">causes backward-rotating field<\/text>\n <line x1=\"260\" y1=\"400\" x2=\"120\" y2=\"400\" stroke=\"#9a6b12\" stroke-width=\"1\"\/>\n <text x=\"62\" y=\"396\" fill=\"#9a6b12\" font-size=\"10\" font-weight=\"600\" font-family=\"Source Sans 3,sans-serif\">Check:<\/text>\n <text x=\"62\" y=\"412\" fill=\"#7a756b\" font-size=\"10\" font-family=\"Source Sans 3,sans-serif\">\u2022 Cable terminations<\/text>\n <text x=\"62\" y=\"426\" fill=\"#7a756b\" font-size=\"10\" font-family=\"Source Sans 3,sans-serif\">\u2022 Phase-to-phase R<\/text>\n <text x=\"62\" y=\"440\" fill=\"#7a756b\" font-size=\"10\" font-family=\"Source Sans 3,sans-serif\">\u2022 IR thermography<\/text>\n<\/svg>\n<\/div>\n<p class=\"infographic-note\"><span class=\"legend-red legend-badge\">2\u00d7LF<\/span><span class=\"legend-green legend-badge\">1X \/ 2X<\/span><span class=\"legend-yellow legend-badge\">Sidebands<\/span> The power-off test confirms electromagnetic origin: if 2\u00d7LF drops sharply upon de-energization (much faster than coastdown), the source is electromagnetic.<\/p>\n\n\n\n<h2 id=\"rotor\"><span class=\"section-num\">4.<\/span> Rotor Defects<\/h2>\n\n<p>Rotor defects account for approximately <strong>5\u201310% of motor failures<\/strong> but are often the most challenging to detect early.<\/p>\n\n<h3 id=\"broken-bars\">4.1. Broken Rotor Bars and Cracked End Rings<\/h3>\n\n<p>When a bar breaks, current redistribution creates local magnetic asymmetry \u2014 effectively a \"magnetic heavy spot\" that rotates at slip frequency relative to the stator field.<\/p>\n\n<h4>Vibration Signature<\/h4>\n<ul>\n <li><strong>1X<\/strong> peak with <strong>sidebands at \u00b1 F<sub>p<\/sub><\/strong>. For 50 Hz \/ 2% slip: sidebands at 1X \u00b1 2 Hz<\/li>\n <li>Severe cases: additional sidebands at \u00b1 2F<sub>p<\/sub>, \u00b1 3F<sub>p<\/sub><\/li>\n <li><strong>2\u00d7LF<\/strong> may also show F<sub>p<\/sub> sidebands<\/li>\n<\/ul>\n\n<h4>MCSA Signature<\/h4>\n<div class=\"formula\">Current spectrum: <strong>LF \u00b1 F<sub>p<\/sub><\/strong> (50 \u00b1 2 Hz = 48 Hz and 52 Hz)<\/div>\n\n<h4>MCSA Severity Scale<\/h4>\n<div class=\"table-wrap\">\n<table>\n<thead><tr><th>Sideband level vs LF peak<\/th><th>Assessment<\/th><\/tr><\/thead>\n<tbody>\n<tr><td><strong>< \u221254 dB<\/strong><\/td><td>Generally healthy rotor<\/td><\/tr>\n<tr><td><strong>\u221254 to \u221248 dB<\/strong><\/td><td>May indicate 1\u20132 cracked bars \u2014 monitor trend<\/td><\/tr>\n<tr><td><strong>\u221248 to \u221240 dB<\/strong><\/td><td>Likely multiple broken bars \u2014 plan inspection<\/td><\/tr>\n<tr><td><strong>> \u221240 dB<\/strong><\/td><td>Severe damage \u2014 risk of secondary failures<\/td><\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<p><em>Important: MCSA requires steady load near rated conditions. At partial load, sideband amplitude drops.<\/em><\/p>\n\n<h4>Time Waveform<\/h4>\n<p>Broken rotor bars produce a characteristic <strong>\"beating\" pattern<\/strong> \u2014 amplitude modulates at the pole pass frequency. Often visible before spectral sidebands become prominent.<\/p>\n\n\n<div class=\"infographic\">\n<div class=\"infographic-title\">Broken Rotor Bars \u2014 Vibration and Current Spectral Patterns<\/div>\n<svg viewBox=\"0 0 840 500\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" style=\"max-width:100%;\" role=\"img\">\n <rect x=\"0\" y=\"0\" width=\"840\" height=\"500\" rx=\"12\" fill=\"#faf8f5\"\/>\n \n <text x=\"215\" y=\"28\" fill=\"#2a5a8c\" font-size=\"15\" font-weight=\"700\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">Vibration Spectrum<\/text>\n <text x=\"215\" y=\"46\" fill=\"#7a756b\" font-size=\"10\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">(velocity, radial direction)<\/text>\n <text x=\"26\" y=\"140\" fill=\"#7a756b\" font-size=\"10\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\" transform=\"rotate(-90 26 140)\">Amplitude<\/text>\n <line x1=\"50\" y1=\"55\" x2=\"50\" y2=\"215\" stroke=\"#d9d3c7\" stroke-width=\"1\"\/>\n <line x1=\"50\" y1=\"215\" x2=\"420\" y2=\"215\" stroke=\"#d9d3c7\" stroke-width=\"1.5\"\/>\n <line x1=\"51\" y1=\"210\" x2=\"419\" y2=\"210\" stroke=\"#e8e3da\" stroke-width=\"1\" stroke-dasharray=\"2,4\"\/>\n \n <rect x=\"124\" y=\"165\" width=\"5\" height=\"45\" rx=\"2\" fill=\"#9a6b12\" opacity=\"0.55\"\/>\n <rect x=\"160\" y=\"122\" width=\"6\" height=\"88\" rx=\"2\" fill=\"#9a6b12\" opacity=\"0.85\"\/>\n <rect x=\"197\" y=\"62\" width=\"8\" height=\"148\" rx=\"2\" fill=\"#2a5a8c\"\/>\n <rect x=\"236\" y=\"122\" width=\"6\" height=\"88\" rx=\"2\" fill=\"#9a6b12\" opacity=\"0.85\"\/>\n <rect x=\"272\" y=\"165\" width=\"5\" height=\"45\" rx=\"2\" fill=\"#9a6b12\" opacity=\"0.55\"\/>\n \n <line x1=\"127\" y1=\"215\" x2=\"127\" y2=\"222\" stroke=\"#7a756b\" stroke-width=\"1\"\/><text x=\"127\" y=\"236\" fill=\"#9a6b12\" font-size=\"9\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">\u22122Fp<\/text>\n <line x1=\"163\" y1=\"215\" x2=\"163\" y2=\"222\" stroke=\"#7a756b\" stroke-width=\"1\"\/><text x=\"163\" y=\"236\" fill=\"#9a6b12\" font-size=\"10\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">1X\u2212Fp<\/text>\n <line x1=\"201\" y1=\"215\" x2=\"201\" y2=\"222\" stroke=\"#7a756b\" stroke-width=\"1\"\/><text x=\"201\" y=\"236\" fill=\"#2a5a8c\" font-size=\"11\" font-weight=\"700\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">1X<\/text>\n <line x1=\"239\" y1=\"215\" x2=\"239\" y2=\"222\" stroke=\"#7a756b\" stroke-width=\"1\"\/><text x=\"239\" y=\"236\" fill=\"#9a6b12\" font-size=\"10\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">1X+Fp<\/text>\n <line x1=\"275\" y1=\"215\" x2=\"275\" y2=\"222\" stroke=\"#7a756b\" stroke-width=\"1\"\/><text x=\"275\" y=\"236\" fill=\"#9a6b12\" font-size=\"9\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">+2Fp<\/text>\n \n <path d=\"M163,118 L163,100 L201,88 L239,100 L239,118\" stroke=\"#9a6b12\" stroke-width=\"1.2\" fill=\"none\"\/>\n <text x=\"201\" y=\"82\" fill=\"#9a6b12\" font-size=\"11\" font-weight=\"600\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">\u00b1 Fp (pole pass frequency)<\/text>\n \n <g transform=\"translate(440,58)\">\n <rect x=\"0\" y=\"0\" width=\"220\" height=\"100\" rx=\"6\" fill=\"#f0ece5\" stroke=\"#d9d3c7\" stroke-width=\"1.5\"\/>\n <text x=\"110\" y=\"20\" fill=\"#2a5a8c\" font-size=\"12\" font-weight=\"700\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">Vibration pattern<\/text>\n <line x1=\"10\" y1=\"28\" x2=\"210\" y2=\"28\" stroke=\"#d9d3c7\" stroke-width=\"1\"\/>\n <text x=\"15\" y=\"46\" fill=\"#3d3b36\" font-size=\"10\" font-family=\"Source Sans 3,sans-serif\">\u2022 1X = carrier (rotational freq.)<\/text>\n <text x=\"15\" y=\"63\" fill=\"#9a6b12\" font-size=\"10\" font-family=\"Source Sans 3,sans-serif\">\u2022 \u00b1Fp sidebands = rotor asymmetry<\/text>\n <text x=\"15\" y=\"80\" fill=\"#7a756b\" font-size=\"10\" font-family=\"Source Sans 3,sans-serif\">\u2022 More sidebands = more bars<\/text>\n <text x=\"15\" y=\"96\" fill=\"#7a756b\" font-size=\"10\" font-family=\"Source Sans 3,sans-serif\">\u2022 \"Beating\" in time waveform<\/text>\n <\/g>\n <g transform=\"translate(440,172)\">\n <rect x=\"0\" y=\"0\" width=\"220\" height=\"62\" rx=\"6\" fill=\"#f0ece5\" stroke=\"#d9d3c7\" stroke-width=\"1\"\/>\n <text x=\"110\" y=\"18\" fill=\"#7a756b\" font-size=\"10\" font-weight=\"600\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">Example: 50 Hz, 2-pole, 2% slip<\/text>\n <text x=\"15\" y=\"36\" fill=\"#3d3b36\" font-size=\"10\" font-family=\"Source Sans 3,sans-serif\">1X = 49 Hz, Fp = 2 Hz<\/text>\n <text x=\"15\" y=\"52\" fill=\"#3d3b36\" font-size=\"10\" font-family=\"Source Sans 3,sans-serif\">Sidebands: 47 Hz and 51 Hz<\/text>\n <\/g>\n\n \n <line x1=\"20\" y1=\"260\" x2=\"820\" y2=\"260\" stroke=\"#d9d3c7\" stroke-width=\"1.5\" stroke-dasharray=\"6,4\"\/>\n\n \n <text x=\"215\" y=\"290\" fill=\"#2d6b30\" font-size=\"15\" font-weight=\"700\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">Current Spectrum (MCSA)<\/text>\n <text x=\"215\" y=\"308\" fill=\"#7a756b\" font-size=\"10\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">(motor supply current via clamp)<\/text>\n <text x=\"26\" y=\"395\" fill=\"#7a756b\" font-size=\"10\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\" transform=\"rotate(-90 26 395)\">Amplitude (dB)<\/text>\n <line x1=\"50\" y1=\"316\" x2=\"50\" y2=\"460\" stroke=\"#d9d3c7\" stroke-width=\"1\"\/>\n <line x1=\"50\" y1=\"460\" x2=\"420\" y2=\"460\" stroke=\"#d9d3c7\" stroke-width=\"1.5\"\/>\n <line x1=\"51\" y1=\"455\" x2=\"419\" y2=\"455\" stroke=\"#e8e3da\" stroke-width=\"1\" stroke-dasharray=\"2,4\"\/>\n \n <rect x=\"150\" y=\"378\" width=\"6\" height=\"77\" rx=\"2\" fill=\"#b8372b\" opacity=\"0.9\"\/>\n <rect x=\"200\" y=\"322\" width=\"8\" height=\"133\" rx=\"2\" fill=\"#2d6b30\"\/>\n <rect x=\"250\" y=\"378\" width=\"6\" height=\"77\" rx=\"2\" fill=\"#b8372b\" opacity=\"0.9\"\/>\n \n <line x1=\"153\" y1=\"460\" x2=\"153\" y2=\"467\" stroke=\"#7a756b\" stroke-width=\"1\"\/><text x=\"153\" y=\"480\" fill=\"#b8372b\" font-size=\"11\" font-weight=\"600\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">48 Hz<\/text><text x=\"153\" y=\"493\" fill=\"#b8372b\" font-size=\"9\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">LF \u2212 Fp<\/text>\n <line x1=\"204\" y1=\"460\" x2=\"204\" y2=\"467\" stroke=\"#7a756b\" stroke-width=\"1\"\/><text x=\"204\" y=\"480\" fill=\"#2d6b30\" font-size=\"12\" font-weight=\"700\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">50 Hz<\/text><text x=\"204\" y=\"493\" fill=\"#2d6b30\" font-size=\"9\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">LF<\/text>\n <line x1=\"253\" y1=\"460\" x2=\"253\" y2=\"467\" stroke=\"#7a756b\" stroke-width=\"1\"\/><text x=\"253\" y=\"480\" fill=\"#b8372b\" font-size=\"11\" font-weight=\"600\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">52 Hz<\/text><text x=\"253\" y=\"493\" fill=\"#b8372b\" font-size=\"9\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">LF + Fp<\/text>\n \n <path d=\"M153,373 L153,360 L204,348 L253,360 L253,373\" stroke=\"#b8372b\" stroke-width=\"1.2\" fill=\"none\"\/>\n <text x=\"204\" y=\"342\" fill=\"#b8372b\" font-size=\"11\" font-weight=\"600\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">\u00b1 Fp = \u00b1 2 Hz sidebands<\/text>\n \n <g transform=\"translate(440,310)\">\n <rect x=\"0\" y=\"0\" width=\"240\" height=\"145\" rx=\"8\" fill=\"#f0ece5\" stroke=\"#d9d3c7\" stroke-width=\"1.5\"\/>\n <text x=\"120\" y=\"22\" fill=\"#2a5a8c\" font-size=\"13\" font-weight=\"700\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">MCSA Severity Scale<\/text>\n <line x1=\"12\" y1=\"30\" x2=\"228\" y2=\"30\" stroke=\"#d9d3c7\" stroke-width=\"1\"\/>\n <text x=\"18\" y=\"50\" fill=\"#7a756b\" font-size=\"10\" font-family=\"Source Sans 3,sans-serif\">(sideband amplitude vs LF peak)<\/text>\n <rect x=\"18\" y=\"60\" width=\"12\" height=\"10\" rx=\"2\" fill=\"#2d6b30\"\/><text x=\"36\" y=\"70\" fill=\"#2d6b30\" font-size=\"11\" font-family=\"Source Sans 3,sans-serif\">< \u221254 dB \u2014 healthy rotor<\/text>\n <rect x=\"18\" y=\"80\" width=\"12\" height=\"10\" rx=\"2\" fill=\"#9a6b12\"\/><text x=\"36\" y=\"90\" fill=\"#9a6b12\" font-size=\"11\" font-family=\"Source Sans 3,sans-serif\">\u221254 to \u221248 dB \u2014 suspect 1-2 bars<\/text>\n <rect x=\"18\" y=\"100\" width=\"12\" height=\"10\" rx=\"2\" fill=\"#9a6b12\"\/><text x=\"36\" y=\"110\" fill=\"#9a6b12\" font-size=\"11\" font-family=\"Source Sans 3,sans-serif\">\u221248 to \u221240 dB \u2014 likely multiple<\/text>\n <rect x=\"18\" y=\"120\" width=\"12\" height=\"10\" rx=\"2\" fill=\"#b8372b\"\/><text x=\"36\" y=\"130\" fill=\"#b8372b\" font-size=\"11\" font-weight=\"600\" font-family=\"Source Sans 3,sans-serif\">> \u221240 dB \u2014 severe (plan repair)<\/text>\n <text x=\"18\" y=\"150\" fill=\"#9e9889\" font-size=\"8.5\" font-style=\"italic\" font-family=\"Source Sans 3,sans-serif\">Rule of thumb at rated load<\/text>\n <\/g>\n<\/svg>\n<\/div>\n<p class=\"infographic-note\"><span class=\"legend-blue legend-badge\">1X<\/span><span class=\"legend-yellow legend-badge\">\u00b1Fp sidebands<\/span><span class=\"legend-red legend-badge\">MCSA sidebands<\/span> Broken rotor bars are best confirmed via MCSA. The vibration spectrum suggests the defect; MCSA provides quantitative severity assessment.<\/p>\n\n\n<h3 id=\"rotor-eccentricity\">4.2. Rotor Eccentricity (Static and Dynamic)<\/h3>\n\n<h4>Static Eccentricity<\/h4>\n<p>Shaft centerline offset from stator bore. Produces elevated <strong>2\u00d7LF<\/strong>. In current: rotor slot harmonics at <strong>f<sub>RBPF<\/sub> \u00b1 LF<\/strong>.<\/p>\n\n<h4>Dynamic Eccentricity<\/h4>\n<p>Rotor center orbits around stator bore center. Produces <strong>1X with 2\u00d7LF sidebands<\/strong> and elevated rotor bar pass frequency. In current: sidebands at <strong>LF \u00b1 f<sub>rot<\/sub><\/strong>.<\/p>\n\n<p>In practice, both types are usually present simultaneously \u2014 the pattern is a superposition.<\/p>\n\n\n<h3 id=\"rotor-bow\">4.3. Thermal Rotor Bow<\/h3>\n\n<p>Large motors can develop a temperature gradient causing temporary bow. Produces <strong>1X that varies with time<\/strong> after startup \u2014 typically increasing for 15\u201360 minutes, then stabilizing. The phase angle drifts as the bow develops. Distinguish from mechanical unbalance (which is stable) by monitoring 1X amplitude and phase for 30\u201360 minutes post-startup.<\/p>\n\n\n<h3 id=\"em-field-shift\">4.4. Electromagnetic Field Displacement (Axial Shift)<\/h3>\n\n<p>If the rotor is <strong>axially displaced<\/strong> relative to the stator, the electromagnetic field distribution becomes asymmetric axially. The rotor experiences an oscillating <strong>axial electromagnetic force at 2\u00d7LF<\/strong>.<\/p>\n\n<h4>Causes<\/h4>\n<ul>\n <li>Incorrect rotor axial positioning during assembly or after bearing replacement<\/li>\n <li>Bearing wear allowing excessive axial play<\/li>\n <li>Shaft thrust from the driven machine<\/li>\n <li>Thermal expansion during operation<\/li>\n<\/ul>\n\n<div class=\"formula\"><strong>Axial 2\u00d7LF<\/strong> (dominant) & elevated <strong>1X<\/strong> \u2014 predominantly in the <strong>axial direction<\/strong><\/div>\n\n<div class=\"key-fact red\">\n <div class=\"key-fact-label\">Critical Defect<\/div>\n <p>This defect can be <strong>highly destructive for bearings<\/strong>. The oscillating axial force at 2\u00d7LF creates cyclic fatigue loading on thrust faces. <strong>Always mark the magnetic center position and verify it during bearing replacements.<\/strong> This is one of the most damaging \u2014 yet most preventable \u2014 motor defects.<\/p>\n<\/div>\n\n\n<div class=\"infographic\">\n<div class=\"infographic-title\">Electromagnetic Field Displacement \u2014 Axial Rotor Shift<\/div>\n<svg viewBox=\"0 0 840 520\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" style=\"max-width:100%;\" role=\"img\">\n <rect x=\"0\" y=\"0\" width=\"840\" height=\"520\" rx=\"12\" fill=\"#faf8f5\"\/>\n \n <text x=\"190\" y=\"26\" fill=\"#2d6b30\" font-size=\"15\" font-weight=\"700\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">Normal: Rotor Centered<\/text>\n <rect x=\"45\" y=\"55\" width=\"290\" height=\"115\" rx=\"8\" fill=\"#e8e3da\" stroke=\"#2a5a8c\" stroke-width=\"2\"\/>\n <text x=\"190\" y=\"74\" fill=\"#2a5a8c\" font-size=\"11\" font-weight=\"600\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">STATOR LAMINATION STACK<\/text>\n <rect x=\"70\" y=\"88\" width=\"240\" height=\"48\" rx=\"5\" fill=\"#d9d3c7\" stroke=\"#6b4a8c\" stroke-width=\"2\"\/>\n <text x=\"190\" y=\"118\" fill=\"#3d3b36\" font-size=\"13\" font-weight=\"700\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">ROTOR<\/text>\n <line x1=\"190\" y1=\"48\" x2=\"190\" y2=\"175\" stroke=\"#2d6b30\" stroke-width=\"1.4\" stroke-dasharray=\"5,3\"\/>\n <text x=\"190\" y=\"188\" fill=\"#2d6b30\" font-size=\"10\" font-weight=\"600\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">Stator CL = Rotor CL<\/text>\n <line x1=\"45\" y1=\"142\" x2=\"70\" y2=\"142\" stroke=\"#2d6b30\" stroke-width=\"1.5\"\/><line x1=\"45\" y1=\"137\" x2=\"45\" y2=\"147\" stroke=\"#2d6b30\" stroke-width=\"1.5\"\/><line x1=\"70\" y1=\"137\" x2=\"70\" y2=\"147\" stroke=\"#2d6b30\" stroke-width=\"1.5\"\/>\n <rect x=\"42\" y=\"148\" width=\"32\" height=\"14\" rx=\"3\" fill=\"#edf5ed\"\/><text x=\"58\" y=\"159\" fill=\"#2d6b30\" font-size=\"10\" font-weight=\"600\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">equal<\/text>\n <line x1=\"310\" y1=\"142\" x2=\"335\" y2=\"142\" stroke=\"#2d6b30\" stroke-width=\"1.5\"\/><line x1=\"310\" y1=\"137\" x2=\"310\" y2=\"147\" stroke=\"#2d6b30\" stroke-width=\"1.5\"\/><line x1=\"335\" y1=\"137\" x2=\"335\" y2=\"147\" stroke=\"#2d6b30\" stroke-width=\"1.5\"\/>\n <rect x=\"306\" y=\"148\" width=\"32\" height=\"14\" rx=\"3\" fill=\"#edf5ed\"\/><text x=\"322\" y=\"159\" fill=\"#2d6b30\" font-size=\"10\" font-weight=\"600\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">equal<\/text>\n <g transform=\"translate(45,202)\">\n <rect x=\"0\" y=\"0\" width=\"290\" height=\"70\" rx=\"6\" fill=\"#edf5ed\" stroke=\"#2d6b30\" stroke-width=\"1.5\"\/>\n <text x=\"145\" y=\"19\" fill=\"#2d6b30\" font-size=\"12\" font-weight=\"700\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">\u2713 Balanced axial EM forces<\/text>\n <text x=\"145\" y=\"37\" fill=\"#2d6b30\" font-size=\"11\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">Minimal axial vibration<\/text>\n <line x1=\"12\" y1=\"46\" x2=\"278\" y2=\"46\" stroke=\"#c5d8c2\" stroke-width=\"1\"\/>\n <text x=\"145\" y=\"62\" fill=\"#7a756b\" font-size=\"10\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">Magnetic center = net axial force \u2248 0<\/text>\n <\/g>\n \n <line x1=\"400\" y1=\"18\" x2=\"400\" y2=\"290\" stroke=\"#d9d3c7\" stroke-width=\"1.5\" stroke-dasharray=\"6,4\"\/>\n \n <text x=\"615\" y=\"26\" fill=\"#b8372b\" font-size=\"15\" font-weight=\"700\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">Defect: Rotor Shifted Axially<\/text>\n <rect x=\"430\" y=\"55\" width=\"290\" height=\"115\" rx=\"8\" fill=\"#e8e3da\" stroke=\"#2a5a8c\" stroke-width=\"2\"\/>\n <text x=\"575\" y=\"74\" fill=\"#2a5a8c\" font-size=\"11\" font-weight=\"600\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">STATOR LAMINATION STACK<\/text>\n <rect x=\"500\" y=\"88\" width=\"240\" height=\"48\" rx=\"5\" fill=\"#d9d3c7\" stroke=\"#b8372b\" stroke-width=\"2\"\/>\n <text x=\"620\" y=\"118\" fill=\"#3d3b36\" font-size=\"13\" font-weight=\"700\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">ROTOR<\/text>\n <line x1=\"575\" y1=\"40\" x2=\"575\" y2=\"175\" stroke=\"#2a5a8c\" stroke-width=\"1.4\" stroke-dasharray=\"5,3\"\/>\n <line x1=\"620\" y1=\"40\" x2=\"620\" y2=\"175\" stroke=\"#b8372b\" stroke-width=\"1.4\" stroke-dasharray=\"5,3\"\/>\n <text x=\"567\" y=\"188\" fill=\"#2a5a8c\" font-size=\"10\" font-weight=\"600\" text-anchor=\"end\" font-family=\"Source Sans 3,sans-serif\">Stator CL<\/text>\n <text x=\"628\" y=\"188\" fill=\"#b8372b\" font-size=\"10\" font-weight=\"600\" font-family=\"Source Sans 3,sans-serif\">Rotor CL<\/text>\n \n <line x1=\"575\" y1=\"44\" x2=\"575\" y2=\"38\" stroke=\"#9a6b12\" stroke-width=\"1.5\"\/>\n <line x1=\"620\" y1=\"44\" x2=\"620\" y2=\"38\" stroke=\"#9a6b12\" stroke-width=\"1.5\"\/>\n <line x1=\"578\" y1=\"41\" x2=\"617\" y2=\"41\" stroke=\"#9a6b12\" stroke-width=\"2\" marker-end=\"url(#arrowY5)\"\/>\n <text x=\"597\" y=\"35\" fill=\"#9a6b12\" font-size=\"11\" font-weight=\"700\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">\u0394x (axial shift)<\/text>\n \n <rect x=\"720\" y=\"88\" width=\"20\" height=\"48\" rx=\"3\" fill=\"rgba(154,107,18,0.12)\" stroke=\"#9a6b12\" stroke-width=\"2\" stroke-dasharray=\"4,3\"\/>\n <line x1=\"740\" y1=\"92\" x2=\"762\" y2=\"68\" stroke=\"#9a6b12\" stroke-width=\"1.2\"\/><circle cx=\"740\" cy=\"92\" r=\"2.5\" fill=\"#9a6b12\"\/>\n <text x=\"766\" y=\"58\" fill=\"#9a6b12\" font-size=\"11\" font-weight=\"600\" font-family=\"Source Sans 3,sans-serif\">Rotor extends<\/text>\n <text x=\"766\" y=\"73\" fill=\"#9a6b12\" font-size=\"11\" font-weight=\"600\" font-family=\"Source Sans 3,sans-serif\">beyond stator<\/text>\n \n <line x1=\"565\" y1=\"155\" x2=\"450\" y2=\"155\" stroke=\"#b8372b\" stroke-width=\"4\" marker-end=\"url(#arrowR6)\"\/>\n <text x=\"505\" y=\"172\" fill=\"#b8372b\" font-size=\"12\" font-weight=\"700\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">F axial at 2\u00d7LF<\/text>\n \n <g transform=\"translate(430,202)\">\n <rect x=\"0\" y=\"0\" width=\"290\" height=\"70\" rx=\"6\" fill=\"#fdf0ee\" stroke=\"#b8372b\" stroke-width=\"1.5\"\/>\n <text x=\"145\" y=\"18\" fill=\"#b8372b\" font-size=\"12\" font-weight=\"700\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">\u2717 Elevated axial 2\u00d7LF & 1X<\/text>\n <text x=\"145\" y=\"36\" fill=\"#b8372b\" font-size=\"11\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">Can accelerate thrust bearing wear<\/text>\n <line x1=\"12\" y1=\"46\" x2=\"278\" y2=\"46\" stroke=\"#e5c0b8\" stroke-width=\"1\"\/>\n <text x=\"145\" y=\"62\" fill=\"#7a756b\" font-size=\"10\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">Severity depends on shift magnitude<\/text>\n <\/g>\n \n <g transform=\"translate(20,295)\">\n <rect x=\"0\" y=\"0\" width=\"800\" height=\"80\" rx=\"10\" fill=\"#f0ece5\" stroke=\"#d9d3c7\" stroke-width=\"1.5\"\/>\n <text x=\"400\" y=\"20\" fill=\"#2a5a8c\" font-size=\"13\" font-weight=\"700\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">How to detect & confirm:<\/text>\n <line x1=\"15\" y1=\"28\" x2=\"785\" y2=\"28\" stroke=\"#d9d3c7\" stroke-width=\"1\"\/>\n <text x=\"20\" y=\"46\" fill=\"#2d6b30\" font-size=\"11\" font-family=\"Source Sans 3,sans-serif\">\u2713 Mark magnetic center during assembly<\/text>\n <text x=\"290\" y=\"46\" fill=\"#2d6b30\" font-size=\"11\" font-family=\"Source Sans 3,sans-serif\">\u2713 Verify position after bearing replacement<\/text>\n <text x=\"600\" y=\"46\" fill=\"#2d6b30\" font-size=\"11\" font-family=\"Source Sans 3,sans-serif\">\u2713 Measure axial vibr. at 2\u00d7LF<\/text>\n <text x=\"20\" y=\"64\" fill=\"#2d6b30\" font-size=\"11\" font-family=\"Source Sans 3,sans-serif\">\u2713 Power-off test: 2\u00d7LF disappears instantly<\/text>\n <text x=\"290\" y=\"64\" fill=\"#2d6b30\" font-size=\"11\" font-family=\"Source Sans 3,sans-serif\">\u2713 Compare coast-down: electrical vs mechanical<\/text>\n <text x=\"600\" y=\"64\" fill=\"#2d6b30\" font-size=\"11\" font-family=\"Source Sans 3,sans-serif\">\u2713 Check thrust bearing temp.<\/text>\n <\/g>\n <g transform=\"translate(20,390)\">\n <rect x=\"0\" y=\"0\" width=\"800\" height=\"80\" rx=\"10\" fill=\"#f0ece5\" stroke=\"#9a6b12\" stroke-width=\"1.5\"\/>\n <text x=\"400\" y=\"20\" fill=\"#9a6b12\" font-size=\"13\" font-weight=\"700\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">Rule out (similar symptoms):<\/text>\n <line x1=\"15\" y1=\"28\" x2=\"785\" y2=\"28\" stroke=\"#d9d3c7\" stroke-width=\"1\"\/>\n <text x=\"20\" y=\"46\" fill=\"#3d3b36\" font-size=\"10.5\" font-family=\"Source Sans 3,sans-serif\">\u2022 Coupling angular misalignment (axial 1X & 2X)<\/text>\n <text x=\"290\" y=\"46\" fill=\"#3d3b36\" font-size=\"10.5\" font-family=\"Source Sans 3,sans-serif\">\u2022 Axial structural resonance<\/text>\n <text x=\"540\" y=\"46\" fill=\"#3d3b36\" font-size=\"10.5\" font-family=\"Source Sans 3,sans-serif\">\u2022 Soft foot \/ looseness (axial component)<\/text>\n <text x=\"20\" y=\"64\" fill=\"#3d3b36\" font-size=\"10.5\" font-family=\"Source Sans 3,sans-serif\">\u2022 Flow-induced axial load (pumps, fans)<\/text>\n <text x=\"290\" y=\"64\" fill=\"#3d3b36\" font-size=\"10.5\" font-family=\"Source Sans 3,sans-serif\">\u2022 Supply voltage unbalance<\/text>\n <text x=\"540\" y=\"64\" fill=\"#3d3b36\" font-size=\"10.5\" font-family=\"Source Sans 3,sans-serif\">\u2022 Radial eccentricity (\u2192 2\u00d7LF radial)<\/text>\n <\/g>\n <text x=\"420\" y=\"495\" fill=\"#9e9889\" font-size=\"9.5\" font-style=\"italic\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">Schematic axial side view \u2014 not to scale.<\/text>\n <defs>\n <marker id=\"arrowR6\" markerWidth=\"10\" markerHeight=\"8\" refX=\"9\" refY=\"4\" orient=\"auto\"><polygon points=\"0 0, 10 4, 0 8\" fill=\"#b8372b\"\/><\/marker>\n <marker id=\"arrowY5\" markerWidth=\"8\" markerHeight=\"6\" refX=\"7\" refY=\"3\" orient=\"auto\"><polygon points=\"0 0, 8 3, 0 6\" fill=\"#9a6b12\"\/><\/marker>\n <\/defs>\n<\/svg>\n<\/div>\n<p class=\"infographic-note\"><span class=\"legend-red legend-badge\">Axial EM force<\/span><span class=\"legend-yellow legend-badge\">Shift \/ overhang<\/span><span class=\"legend-blue legend-badge\">Stator CL<\/span><span class=\"legend-green legend-badge\">Detection<\/span> Axial 2\u00d7LF that vanishes instantly on power-off is the key differentiator from mechanical causes.<\/p>\n\n\n\n<h2 id=\"bearings-electrical\"><span class=\"section-num\">5.<\/span> Bearing-Related Electrical Defects<\/h2>\n\n<h3>5.1. Bearing Currents and EDM<\/h3>\n<p>Voltage between shaft and housing causes current flow through bearings. Sources: magnetic asymmetry, VFD common-mode voltage, static charge. Repeated discharges create microscopic pits (<strong>Electrical Discharge Machining<\/strong>) leading to <strong>fluting<\/strong> \u2014 evenly spaced grooves on races.<\/p>\n\n<h4>Spectral Signature<\/h4>\n<ul>\n <li>Bearing defect frequencies (BPFO, BPFI, BSF) with very uniform, \"clean\" peaks<\/li>\n <li>Elevated high-frequency noise floor in acceleration spectrum<\/li>\n <li>Advanced: characteristic \"washboard\" sound<\/li>\n<\/ul>\n\n<h4>Prevention<\/h4>\n<ul>\n <li>Insulated bearings (coated rings)<\/li>\n <li>Shaft grounding brushes (especially for VFD applications)<\/li>\n <li>Common-mode filters on VFD output<\/li>\n <li>Regular shaft voltage measurement \u2014 below 0.5 V peak<\/li>\n<\/ul>\n\n\n\n<h2 id=\"vfd\"><span class=\"section-num\">6.<\/span> Variable Frequency Drive (VFD) Effects<\/h2>\n\n<h3>6.1. Frequency Shifting<\/h3>\n<p>All motor electrical frequencies shift proportionally with VFD output frequency. If VFD runs at 45 Hz, 2\u00d7LF becomes 90 Hz. Alarm bands must be <strong>speed-adaptive<\/strong>.<\/p>\n\n<h3>6.2. PWM Harmonics<\/h3>\n<p>Switching frequency (2\u201316 kHz) and sidebands appear in spectra. Can cause audible noise and bearing currents.<\/p>\n\n<h3>6.3. Torsional Excitation<\/h3>\n<p>Low-order harmonics (5th, 7th, 11th, 13th) create torque pulsations that can excite torsional natural frequencies.<\/p>\n\n<h3>6.4. Resonance Excitation<\/h3>\n<p>As VFD sweeps through a speed range, excitation frequencies may pass through structural natural frequencies. Critical speed maps should be established for VFD-driven equipment.<\/p>\n\n\n\n<h2 id=\"differential\"><span class=\"section-num\">7.<\/span> Differential Diagnostics Summary<\/h2>\n\n<div class=\"table-wrap\">\n<table>\n<thead><tr><th>Defect<\/th><th>Primary Freq.<\/th><th>Direction<\/th><th>Sidebands \/ Notes<\/th><th>Confirmation<\/th><\/tr><\/thead>\n<tbody>\n<tr><td><strong>Stator eccentricity<\/strong><\/td><td>2\u00d7LF<\/td><td>Radial<\/td><td>Minor 1X, 2X increase<\/td><td>Power-off test; soft foot check<\/td><\/tr>\n<tr><td><strong>Loose windings<\/strong><\/td><td>2\u00d7LF<\/td><td>Radial<\/td><td>Increasing trend; 4\u00d7LF, 6\u00d7LF<\/td><td>Trending; MCA surge test<\/td><\/tr>\n<tr><td><strong>Loose cable<\/strong><\/td><td>2\u00d7LF<\/td><td>Radial<\/td><td>\u00b1 \u2153\u00d7LF sidebands<\/td><td>Phase resistance; IR thermography<\/td><\/tr>\n<tr><td><strong>Inter-turn short<\/strong><\/td><td>2\u00d7LF<\/td><td>Radial<\/td><td>Current asymmetry; 3rd harmonic<\/td><td>MCA surge test; MCSA<\/td><\/tr>\n<tr><td><strong>Shorted laminations<\/strong><\/td><td>Minor 2\u00d7LF<\/td><td>\u2014<\/td><td>Primarily thermal<\/td><td>IR thermography; EL-CID<\/td><\/tr>\n<tr><td><strong>Broken rotor bars<\/strong><\/td><td>1X<\/td><td>Radial<\/td><td>\u00b1 F<sub>p<\/sub> sidebands; beating<\/td><td>MCSA: LF \u00b1 F<sub>p<\/sub> dB level<\/td><\/tr>\n<tr><td><strong>Rotor eccentricity (static)<\/strong><\/td><td>2\u00d7LF<\/td><td>Radial<\/td><td>Rotor slot harmonics \u00b1 LF<\/td><td>Air gap measurement; MCSA<\/td><\/tr>\n<tr><td><strong>Rotor eccentricity (dynamic)<\/strong><\/td><td>1X + 2\u00d7LF<\/td><td>Radial<\/td><td>f<sub>RBPF<\/sub> sidebands<\/td><td>Orbit analysis; MCSA<\/td><\/tr>\n<tr><td><strong>Thermal rotor bow<\/strong><\/td><td>1X (drifting)<\/td><td>Radial<\/td><td>Amp & phase change with temp.<\/td><td>30-60 min startup trending<\/td><\/tr>\n<tr><td><strong>EM field displacement<\/strong><\/td><td>2\u00d7LF + 1X<\/td><td><strong>Axial<\/strong><\/td><td>Strong axial 2\u00d7LF<\/td><td>Rotor axial position; power-off test<\/td><\/tr>\n<tr><td><strong>Bearing EDM \/ fluting<\/strong><\/td><td>BPFO \/ BPFI<\/td><td>Radial<\/td><td>Uniform peaks; high HF noise<\/td><td>Shaft voltage; visual inspection<\/td><\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n\n\n<div class=\"infographic\">\n<div class=\"infographic-title\">Motor Defect Diagnostic Flowchart<\/div>\n<svg viewBox=\"0 0 760 420\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" style=\"max-width:100%;\" role=\"img\">\n <rect x=\"0\" y=\"0\" width=\"760\" height=\"420\" rx=\"12\" fill=\"#faf8f5\"\/>\n \n <rect x=\"280\" y=\"12\" width=\"200\" height=\"36\" rx=\"18\" fill=\"#eef4fa\" stroke=\"#2a5a8c\" stroke-width=\"2\"\/>\n <text x=\"380\" y=\"36\" fill=\"#3d3b36\" font-size=\"12\" font-weight=\"600\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">Elevated motor vibration<\/text>\n <line x1=\"380\" y1=\"48\" x2=\"380\" y2=\"68\" stroke=\"#2a5a8c\" stroke-width=\"1.5\" marker-end=\"url(#aB3)\"\/>\n \n <polygon points=\"380,68 470,100 380,132 290,100\" fill=\"#fef9ec\" stroke=\"#9a6b12\" stroke-width=\"1.5\"\/>\n <text x=\"380\" y=\"96\" fill=\"#9a6b12\" font-size=\"10\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">Power-off<\/text>\n <text x=\"380\" y=\"110\" fill=\"#9a6b12\" font-size=\"10\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">snap test?<\/text>\n \n <line x1=\"290\" y1=\"100\" x2=\"190\" y2=\"100\" stroke=\"#b8372b\" stroke-width=\"1.5\"\/><text x=\"240\" y=\"93\" fill=\"#b8372b\" font-size=\"9\" font-family=\"Source Sans 3,sans-serif\">Instant drop<\/text>\n <rect x=\"60\" y=\"80\" width=\"130\" height=\"40\" rx=\"6\" fill=\"#fdf0ee\" stroke=\"#b8372b\" stroke-width=\"1.5\"\/>\n <text x=\"125\" y=\"98\" fill=\"#b8372b\" font-size=\"11\" font-weight=\"600\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">ELECTRICAL<\/text>\n <text x=\"125\" y=\"112\" fill=\"#3d3b36\" font-size=\"9\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">source confirmed<\/text>\n <line x1=\"125\" y1=\"120\" x2=\"125\" y2=\"148\" stroke=\"#b8372b\" stroke-width=\"1.5\" marker-end=\"url(#aR3)\"\/>\n \n <polygon points=\"125,148 215,180 125,212 35,180\" fill=\"#faf8f5\" stroke=\"#2a5a8c\" stroke-width=\"1.5\"\/>\n <text x=\"125\" y=\"176\" fill=\"#2a5a8c\" font-size=\"9\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">Dominant<\/text>\n <text x=\"125\" y=\"190\" fill=\"#2a5a8c\" font-size=\"9\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">frequency?<\/text>\n \n <line x1=\"35\" y1=\"180\" x2=\"15\" y2=\"180\" stroke=\"#2a5a8c\" stroke-width=\"1\"\/><line x1=\"15\" y1=\"180\" x2=\"15\" y2=\"250\" stroke=\"#2a5a8c\" stroke-width=\"1\"\/>\n <rect x=\"5\" y=\"252\" width=\"160\" height=\"70\" rx=\"6\" fill=\"#eef4fa\" stroke=\"#2a5a8c\" stroke-width=\"1\"\/>\n <text x=\"85\" y=\"268\" fill=\"#2a5a8c\" font-size=\"9.5\" font-weight=\"600\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">2\u00d7LF (radial):<\/text>\n <text x=\"85\" y=\"283\" fill=\"#7a756b\" font-size=\"8.5\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">\u2022 Eccentricity \/ air gap<\/text>\n <text x=\"85\" y=\"296\" fill=\"#7a756b\" font-size=\"8.5\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">\u2022 Loose windings (trending)<\/text>\n <text x=\"85\" y=\"309\" fill=\"#7a756b\" font-size=\"8.5\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">\u2022 Loose cable (+\u2153LF bands)<\/text>\n \n <line x1=\"125\" y1=\"212\" x2=\"125\" y2=\"252\" stroke=\"#b8372b\" stroke-width=\"1\"\/>\n <rect x=\"175\" y=\"252\" width=\"155\" height=\"50\" rx=\"6\" fill=\"#fdf0ee\" stroke=\"#b8372b\" stroke-width=\"1\"\/>\n <text x=\"252\" y=\"272\" fill=\"#b8372b\" font-size=\"9.5\" font-weight=\"600\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">EM field displacement<\/text>\n <text x=\"252\" y=\"288\" fill=\"#3d3b36\" font-size=\"8.5\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">Check rotor axial position!<\/text>\n \n <line x1=\"215\" y1=\"180\" x2=\"260\" y2=\"180\" stroke=\"#9a6b12\" stroke-width=\"1\"\/><line x1=\"260\" y1=\"180\" x2=\"260\" y2=\"252\" stroke=\"#9a6b12\" stroke-width=\"1\"\/>\n <rect x=\"345\" y=\"252\" width=\"140\" height=\"50\" rx=\"6\" fill=\"#fef9ec\" stroke=\"#9a6b12\" stroke-width=\"1\"\/>\n <text x=\"415\" y=\"272\" fill=\"#9a6b12\" font-size=\"9.5\" font-weight=\"600\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">Broken rotor bars<\/text>\n <text x=\"415\" y=\"288\" fill=\"#3d3b36\" font-size=\"8.5\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">Confirm with MCSA<\/text>\n \n <line x1=\"470\" y1=\"100\" x2=\"570\" y2=\"100\" stroke=\"#2d6b30\" stroke-width=\"1.5\"\/><text x=\"520\" y=\"93\" fill=\"#2d6b30\" font-size=\"9\" font-family=\"Source Sans 3,sans-serif\">Gradual decay<\/text>\n <rect x=\"570\" y=\"80\" width=\"130\" height=\"40\" rx=\"6\" fill=\"#edf5ed\" stroke=\"#2d6b30\" stroke-width=\"1.5\"\/>\n <text x=\"635\" y=\"98\" fill=\"#2d6b30\" font-size=\"11\" font-weight=\"600\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">MECHANICAL<\/text>\n <text x=\"635\" y=\"112\" fill=\"#3d3b36\" font-size=\"9\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">source confirmed<\/text>\n <line x1=\"635\" y1=\"120\" x2=\"635\" y2=\"148\" stroke=\"#2d6b30\" stroke-width=\"1.5\" marker-end=\"url(#aG3)\"\/>\n <rect x=\"555\" y=\"148\" width=\"160\" height=\"60\" rx=\"6\" fill=\"#edf5ed\" stroke=\"#2d6b30\" stroke-width=\"1\"\/>\n <text x=\"635\" y=\"166\" fill=\"#2d6b30\" font-size=\"9.5\" font-weight=\"600\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">Investigate:<\/text>\n <text x=\"635\" y=\"182\" fill=\"#7a756b\" font-size=\"8.5\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">\u2022 Unbalance, misalignment<\/text>\n <text x=\"635\" y=\"195\" fill=\"#7a756b\" font-size=\"8.5\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">\u2022 Bearing defects, soft foot<\/text>\n \n <rect x=\"180\" y=\"340\" width=\"400\" height=\"35\" rx=\"8\" fill=\"#eef4fa\" stroke=\"#2a5a8c\" stroke-width=\"1.5\"\/>\n <text x=\"380\" y=\"358\" fill=\"#2a5a8c\" font-size=\"11\" font-weight=\"600\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">Always combine: Vibration + MCSA + Power-off test + Trending<\/text>\n <rect x=\"180\" y=\"385\" width=\"400\" height=\"28\" rx=\"14\" fill=\"#edf5ed\" stroke=\"#2d6b30\" stroke-width=\"2\"\/>\n <text x=\"380\" y=\"404\" fill=\"#2d6b30\" font-size=\"11\" font-weight=\"600\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">Resolution reminder: \u2264 0.5 Hz to separate 2X from 2\u00d7LF<\/text>\n <defs>\n <marker id=\"aB3\" markerWidth=\"8\" markerHeight=\"6\" refX=\"4\" refY=\"3\" orient=\"auto\"><polygon points=\"0 0, 8 3, 0 6\" fill=\"#2a5a8c\"\/><\/marker>\n <marker id=\"aR3\" markerWidth=\"8\" markerHeight=\"6\" refX=\"4\" refY=\"3\" orient=\"auto\"><polygon points=\"0 0, 8 3, 0 6\" fill=\"#b8372b\"\/><\/marker>\n <marker id=\"aG3\" markerWidth=\"8\" markerHeight=\"6\" refX=\"4\" refY=\"3\" orient=\"auto\"><polygon points=\"0 0, 8 3, 0 6\" fill=\"#2d6b30\"\/><\/marker>\n <\/defs>\n<\/svg>\n<\/div>\n<p class=\"infographic-note\"><span class=\"legend-red legend-badge\">Electrical<\/span><span class=\"legend-green legend-badge\">Mechanical<\/span><span class=\"legend-blue legend-badge\">2\u00d7LF analysis<\/span><span class=\"legend-yellow legend-badge\">Rotor defects<\/span> The power-off snap test is the first fork in the diagnostic tree. Once electrical origin is confirmed, dominant frequency and direction narrow the diagnosis.<\/p>\n\n\n\n<h2 id=\"instrumentation\"><span class=\"section-num\">8.<\/span> Instrumentation and Measurement Techniques<\/h2>\n\n<h3>8.1. Vibration Measurement Requirements<\/h3>\n\n<div class=\"table-wrap\">\n<table>\n<thead><tr><th>Parameter<\/th><th>Requirement<\/th><th>Reason<\/th><\/tr><\/thead>\n<tbody>\n<tr><td><strong>Spectral resolution<\/strong><\/td><td>\u2264 0.5 Hz (preferably 0.125 Hz)<\/td><td>Separate 2X from 2\u00d7LF (2 Hz apart for 2-pole)<\/td><\/tr>\n<tr><td><strong>Frequency range<\/strong><\/td><td>2\u20131000 Hz (vel.); to 10 kHz (acc.)<\/td><td>Low range for 1X, 2\u00d7LF; high for bearings<\/td><\/tr>\n<tr><td><strong>Channels<\/strong><\/td><td>\u2265 2 simultaneous<\/td><td>Cross-phase analysis<\/td><\/tr>\n<tr><td><strong>Phase measurement<\/strong><\/td><td>0\u2013360\u00b0, \u00b12\u00b0<\/td><td>Critical for defect differentiation<\/td><\/tr>\n<tr><td><strong>Time waveform<\/strong><\/td><td>Synchronous averaging<\/td><td>Detect beating from broken bars<\/td><\/tr>\n<tr><td><strong>Current input<\/strong><\/td><td>Current clamp compatible<\/td><td>For MCSA diagnostics<\/td><\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n\n<h3>8.2. Balanset-1A for Motor Diagnostics<\/h3>\n\n<p>The portable dual-channel vibrometer <strong>Balanset-1A<\/strong> (VibroMera) provides core capabilities for motor vibration diagnostics:<\/p>\n\n<div class=\"spec-grid\">\n <div class=\"spec-item\"><span class=\"spec-item-label\">Vibration Channels<\/span><span class=\"spec-item-value\">2 (simultaneous)<\/span><\/div>\n <div class=\"spec-item\"><span class=\"spec-item-label\">Speed Range<\/span><span class=\"spec-item-value\">250\u201390,000 RPM<\/span><\/div>\n <div class=\"spec-item\"><span class=\"spec-item-label\">Vibration Velocity RMS<\/span><span class=\"spec-item-value\">0\u201380 mm\/s<\/span><\/div>\n <div class=\"spec-item\"><span class=\"spec-item-label\">Phase Accuracy<\/span><span class=\"spec-item-value\">0\u2013360\u00b0, \u00b12\u00b0<\/span><\/div>\n <div class=\"spec-item\"><span class=\"spec-item-label\">FFT Spectral Analysis<\/span><span class=\"spec-item-value\">Supported<\/span><\/div>\n <div class=\"spec-item\"><span class=\"spec-item-label\">Phase Sensor<\/span><span class=\"spec-item-value\">Photoelectric, included<\/span><\/div>\n <div class=\"spec-item\"><span class=\"spec-item-label\">Power Supply<\/span><span class=\"spec-item-value\">USB (7\u201320 V)<\/span><\/div>\n <div class=\"spec-item\"><span class=\"spec-item-label\">Balancing<\/span><span class=\"spec-item-value\">1 or 2 planes in-situ<\/span><\/div>\n<\/div>\n\n<p>After diagnosing and correcting the motor defect, the Balanset-1A can be used for <strong>in-situ rotor balancing<\/strong> \u2014 completing the full diagnostic-to-correction workflow without removing the motor.<\/p>\n\n<h3>8.3. Measurement Best Practices<\/h3>\n<ul>\n <li><strong>Three directions<\/strong> \u2014 vertical, horizontal, and axial \u2014 on each bearing. Axial is critical for EM field displacement<\/li>\n <li><strong>Prepare surfaces<\/strong> \u2014 remove paint, rust for reliable accelerometer coupling<\/li>\n <li><strong>Steady-state conditions<\/strong> \u2014 nominal speed, load, temperature<\/li>\n <li><strong>Record operating conditions<\/strong> \u2014 speed, load, voltage, current with each measurement<\/li>\n <li><strong>Consistent timing<\/strong> \u2014 same conditions for trend comparisons<\/li>\n <li><strong>Power-off test<\/strong> when electrical vibration is suspected \u2014 takes seconds, provides reliable source identification<\/li>\n<\/ul>\n\n\n\n<h2 id=\"standards\"><span class=\"section-num\">9.<\/span> Normative References<\/h2>\n\n<ul class=\"standards-list\">\n <li><strong>GOST R ISO 20816-1-2021<\/strong> \u2014 Vibration. Measurement and evaluation of machine vibration. Part 1. General guidelines.<\/li>\n <li><strong>GOST R ISO 18436-2-2005<\/strong> \u2014 Condition monitoring. Vibration condition monitoring. Part 2. Training and certification.<\/li>\n <li><strong>ISO 20816-1:2016<\/strong> \u2014 Mechanical vibration. Measurement and evaluation. Part 1: General guidelines.<\/li>\n <li><strong>ISO 10816-3:2009<\/strong> \u2014 Evaluation of machine vibration. Part 3: Industrial machines >15 kW.<\/li>\n <li><strong>IEC 60034-14:2018<\/strong> \u2014 Rotating electrical machines. Part 14: Mechanical vibration.<\/li>\n <li><strong>IEEE 43-2013<\/strong> \u2014 Recommended practice for testing insulation resistance.<\/li>\n <li><strong>IEEE 1415-2006<\/strong> \u2014 Guide for induction machinery maintenance testing.<\/li>\n <li><strong>NEMA MG 1-2021<\/strong> \u2014 Motors and generators. Vibration limits and testing.<\/li>\n <li><strong>ISO 1940-1:2003<\/strong> \u2014 Balance quality requirements for rotors.<\/li>\n<\/ul>\n\n\n\n<h2 id=\"conclusion\"><span class=\"section-num\">10.<\/span> Conclusion<\/h2>\n\n<div class=\"conclusion-box\">\n <h3>Key Diagnostic Principles<\/h3>\n <p>Electric motor defects leave characteristic fingerprints in vibration and current spectra \u2014 but only if you know where to look and have the right tools configured correctly.<\/p>\n<\/div>\n\n<ol>\n <li><strong>2\u00d7LF is the primary electromagnetic indicator.<\/strong> A prominent peak at exactly twice supply frequency strongly suggests an electromagnetic source. The power-off test provides confirmation.<\/li>\n <li><strong>Direction matters.<\/strong> Radial 2\u00d7LF \u2192 air gap \/ windings \/ supply. <strong>Axial<\/strong> 2\u00d7LF + 1X \u2192 electromagnetic field displacement \u2014 one of the most destructive defects.<\/li>\n <li><strong>Sidebands tell the story.<\/strong> \u00b1 \u2153\u00d7LF \u2192 supply cable problems. \u00b1 F<sub>p<\/sub> \u2192 broken rotor bars. The sideband pattern is often more diagnostic than the main peak.<\/li>\n <li><strong>Spectral resolution is critical.<\/strong> For 2-pole motors at 50 Hz, 2X and 2\u00d7LF are only ~2 Hz apart. Resolution \u2264 0.5 Hz is mandatory.<\/li>\n <li><strong>Combine methods.<\/strong> Vibration + MCSA + MCA + Thermography. No single method covers all defects.<\/li>\n <li><strong>Talk to the electricians.<\/strong> Motor repair personnel possess irreplaceable knowledge about specific motors, their history, and supply conditions.<\/li>\n<\/ol>\n\n<h4>Recommended Workflow<\/h4>\n\n<div class=\"workflow-strip\">\n <div class=\"workflow-step\"><div class=\"workflow-step-num\">1<\/div><div class=\"workflow-step-label\">Vibration Measurement<\/div><\/div>\n <div class=\"workflow-step\"><div class=\"workflow-step-num\">2<\/div><div class=\"workflow-step-label\">Power-Off Test<\/div><\/div>\n <div class=\"workflow-step\"><div class=\"workflow-step-num\">3<\/div><div class=\"workflow-step-label\">Spectral Analysis<\/div><\/div>\n <div class=\"workflow-step\"><div class=\"workflow-step-num\">4<\/div><div class=\"workflow-step-label\">MCSA (if rotor)<\/div><\/div>\n <div class=\"workflow-step\"><div class=\"workflow-step-num\">5<\/div><div class=\"workflow-step-label\">Correct & Balance<\/div><\/div>\n <div class=\"workflow-step\"><div class=\"workflow-step-num\">6<\/div><div class=\"workflow-step-label\">Verification \u2713<\/div><\/div>\n<\/div>\n\n\n<div class=\"infographic\">\n<div class=\"infographic-title\">Motor Diagnostics \u2014 Recommended Workflow<\/div>\n<svg viewBox=\"0 0 720 320\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" style=\"max-width:100%;\" role=\"img\">\n <rect x=\"0\" y=\"0\" width=\"720\" height=\"320\" rx=\"12\" fill=\"#faf8f5\"\/>\n <rect x=\"250\" y=\"12\" width=\"220\" height=\"40\" rx=\"8\" fill=\"#eef4fa\" stroke=\"#2a5a8c\" stroke-width=\"2\"\/>\n <text x=\"360\" y=\"30\" fill=\"#3d3b36\" font-size=\"11\" font-weight=\"600\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">1. Vibration measurement<\/text>\n <text x=\"360\" y=\"44\" fill=\"#7a756b\" font-size=\"9\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">3 directions, all bearings, \u22640.5 Hz res.<\/text>\n <line x1=\"360\" y1=\"52\" x2=\"360\" y2=\"68\" stroke=\"#2a5a8c\" stroke-width=\"1.5\" marker-end=\"url(#aB4)\"\/>\n <rect x=\"250\" y=\"68\" width=\"220\" height=\"40\" rx=\"8\" fill=\"#eef4fa\" stroke=\"#2a5a8c\" stroke-width=\"2\"\/>\n <text x=\"360\" y=\"86\" fill=\"#3d3b36\" font-size=\"11\" font-weight=\"600\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">2. Power-off snap test<\/text>\n <text x=\"360\" y=\"100\" fill=\"#7a756b\" font-size=\"9\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">Electrical vs. mechanical source<\/text>\n <line x1=\"360\" y1=\"108\" x2=\"360\" y2=\"124\" stroke=\"#2a5a8c\" stroke-width=\"1.5\" marker-end=\"url(#aB4)\"\/>\n <rect x=\"250\" y=\"124\" width=\"220\" height=\"40\" rx=\"8\" fill=\"#eef4fa\" stroke=\"#2a5a8c\" stroke-width=\"2\"\/>\n <text x=\"360\" y=\"142\" fill=\"#3d3b36\" font-size=\"11\" font-weight=\"600\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">3. Spectral analysis<\/text>\n <text x=\"360\" y=\"156\" fill=\"#7a756b\" font-size=\"9\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">2\u00d7LF, 1X, sidebands, direction<\/text>\n <line x1=\"360\" y1=\"164\" x2=\"360\" y2=\"180\" stroke=\"#2a5a8c\" stroke-width=\"1.5\" marker-end=\"url(#aB4)\"\/>\n <rect x=\"250\" y=\"180\" width=\"220\" height=\"40\" rx=\"8\" fill=\"#fef9ec\" stroke=\"#9a6b12\" stroke-width=\"2\"\/>\n <text x=\"360\" y=\"198\" fill=\"#3d3b36\" font-size=\"11\" font-weight=\"600\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">4. MCSA (if rotor suspected)<\/text>\n <text x=\"360\" y=\"212\" fill=\"#7a756b\" font-size=\"9\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">Current clamp, LF \u00b1 Fp analysis<\/text>\n <line x1=\"360\" y1=\"220\" x2=\"360\" y2=\"236\" stroke=\"#2a5a8c\" stroke-width=\"1.5\" marker-end=\"url(#aB4)\"\/>\n <rect x=\"250\" y=\"236\" width=\"220\" height=\"36\" rx=\"8\" fill=\"#eef4fa\" stroke=\"#5a8ab8\" stroke-width=\"1.5\"\/>\n <text x=\"360\" y=\"258\" fill=\"#3d3b36\" font-size=\"11\" font-weight=\"600\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">5. Correct & balance (Balanset-1A)<\/text>\n <line x1=\"360\" y1=\"272\" x2=\"360\" y2=\"286\" stroke=\"#2a5a8c\" stroke-width=\"1.5\" marker-end=\"url(#aB4)\"\/>\n <rect x=\"230\" y=\"286\" width=\"260\" height=\"26\" rx=\"13\" fill=\"#edf5ed\" stroke=\"#2d6b30\" stroke-width=\"2\"\/>\n <text x=\"360\" y=\"304\" fill=\"#2d6b30\" font-size=\"11\" font-weight=\"600\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">6. Verification measurement \u2713<\/text>\n <g transform=\"translate(15,15)\">\n <rect x=\"0\" y=\"0\" width=\"200\" height=\"70\" rx=\"6\" fill=\"#f0ece5\" stroke=\"#d9d3c7\" stroke-width=\"1\"\/>\n <text x=\"100\" y=\"18\" fill=\"#2a5a8c\" font-size=\"10\" font-weight=\"600\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">Balanset-1A covers:<\/text>\n <text x=\"100\" y=\"34\" fill=\"#7a756b\" font-size=\"9\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">\u25b8 Steps 1, 3 \u2014 vibration spectra<\/text>\n <text x=\"100\" y=\"48\" fill=\"#7a756b\" font-size=\"9\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">\u25b8 Step 5 \u2014 field balancing<\/text>\n <text x=\"100\" y=\"62\" fill=\"#7a756b\" font-size=\"9\" text-anchor=\"middle\" font-family=\"Source Sans 3,sans-serif\">\u25b8 Step 6 \u2014 verification<\/text>\n <\/g>\n <defs><marker id=\"aB4\" markerWidth=\"8\" markerHeight=\"6\" refX=\"4\" refY=\"3\" orient=\"auto\"><polygon points=\"0 0, 8 3, 0 6\" fill=\"#2a5a8c\"\/><\/marker><\/defs>\n<\/svg>\n<\/div>\n<p class=\"infographic-note\"><span class=\"legend-blue legend-badge\">Diagnostic steps<\/span><span class=\"legend-yellow legend-badge\">MCSA<\/span><span class=\"legend-green legend-badge\">Verification<\/span> Follow this sequence systematically. The power-off test (step 2) takes seconds and reliably distinguishes electrical vs. mechanical source.<\/p>\n\n<p>Modern portable dual-channel vibrometers such as the <strong>Balanset-1A<\/strong> enable field engineers to perform spectral vibration analysis with the resolution and phase accuracy required for motor defect identification \u2014 from detecting uneven air gaps through cross-phase analysis to subsequent in-situ rotor balancing.<\/p>\n\n<hr>\n\n<footer class=\"article-footer\">\n <p><em>Sources: field vibration diagnostics training programs; GOST R ISO 20816-1-2021; GOST R ISO 18436-2-2005; IEC 60034-14:2018; IEEE 1415-2006; ISO 1940-1:2003; VibroMera technical documentation (Balanset-1A); EPRI motor reliability studies.<\/em><\/p>\n<\/footer>\n\n<\/main>\n<\/div>\n\n<script>\nwindow.addEventListener('scroll',()=>{const h=document.documentElement.scrollHeight-document.documentElement.clientHeight;const s=(window.scrollY\/h)*100;document.getElementById('progressBar').style.width=s+'%';const b=document.getElementById('backToTop');b.classList.toggle('visible',window.scrollY>400)});\nconst sections=document.querySelectorAll('h2[id],h3[id]');const tocLinks=document.querySelectorAll('.toc-list a');\nconst observer=new IntersectionObserver(entries=>{entries.forEach(entry=>{if(entry.isIntersecting){const id=entry.target.getAttribute('id');tocLinks.forEach(link=>{link.classList.remove('active');if(link.getAttribute('data-section')===id)link.classList.add('active')})}})},{rootMargin:'-20% 0px -70% 0px'});\nsections.forEach(s=>observer.observe(s));\n<\/script>\n<\/body>\n<\/html><\/div><\/div><\/div><\/div><\/div>","protected":false},"excerpt":{"rendered":"<p>Electric Motor Defects: Comprehensive Spectral Analysis VibroMera Technical Knowledge Base Table of Contents 1. Electrical Fundamentals 2. Diagnostic Methods 3. Stator Defects 3.1 Stator Eccentricity 3.2 Loose Windings 3.3 Loose Power Cable 3.4 Shorted Laminations 3.5 Inter-Turn Short 4. Rotor Defects 4.1 Broken Rotor Bars 4.2 Rotor Eccentricity 4.3 Thermal […]<\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"ai_generated_summary":"","footnotes":""},"categories":[1],"tags":[],"class_list":["post-100667","post","type-post","status-publish","format-standard","hentry","category-uncategorized"],"_links":{"self":[{"href":"https:\/\/vibromera.eu\/nb\/wp-json\/wp\/v2\/posts\/100667","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/vibromera.eu\/nb\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/vibromera.eu\/nb\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/vibromera.eu\/nb\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/vibromera.eu\/nb\/wp-json\/wp\/v2\/comments?post=100667"}],"version-history":[{"count":8,"href":"https:\/\/vibromera.eu\/nb\/wp-json\/wp\/v2\/posts\/100667\/revisions"}],"predecessor-version":[{"id":100836,"href":"https:\/\/vibromera.eu\/nb\/wp-json\/wp\/v2\/posts\/100667\/revisions\/100836"}],"wp:attachment":[{"href":"https:\/\/vibromera.eu\/nb\/wp-json\/wp\/v2\/media?parent=100667"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/vibromera.eu\/nb\/wp-json\/wp\/v2\/categories?post=100667"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/vibromera.eu\/nb\/wp-json\/wp\/v2\/tags?post=100667"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}