{"id":100157,"date":"2026-02-15T20:21:31","date_gmt":"2026-02-15T20:21:31","guid":{"rendered":"https:\/\/vibromera.eu\/?post_type=calculator&#038;p=100157"},"modified":"2026-02-15T20:21:31","modified_gmt":"2026-02-15T20:21:31","slug":"motor-electrical-frequencies","status":"publish","type":"calculator","link":"https:\/\/vibromera.eu\/bn\/calculators\/motor-electrical-frequencies\/","title":{"rendered":"\u09ae\u09cb\u099f\u09b0 \u09ac\u09c8\u09a6\u09cd\u09af\u09c1\u09a4\u09bf\u0995 \u09a4\u09cd\u09b0\u09c1\u099f\u09bf \u09ab\u09cd\u09b0\u09bf\u0995\u09cb\u09af\u09bc\u09c7\u09a8\u09cd\u09b8\u09bf \u0995\u09cd\u09af\u09be\u09b2\u0995\u09c1\u09b2\u09c7\u099f\u09b0"},"content":{"rendered":"\n<script type=\"application\/ld+json\">\n{\"@context\":\"https:\/\/schema.org\",\"@type\":\"WebApplication\",\"name\":\"Motor Electrical Defect Frequency Calculator\",\"alternateName\":[\"Motor Slip Calculator\",\"Pole Pass Frequency Calculator\",\"Rotor Bar Frequency Calculator\"],\"description\":\"Free online engineering calculator for motor electrical defect frequencies. Computes synchronous speed, slip, 2\u00d7 line frequency, pole pass frequency, rotor bar pass frequency, and diagnostic sidebands.\",\"url\":\"https:\/\/vibromera.eu\/calculators\/motor-electrical-frequencies\/\",\"applicationCategory\":\"Engineering Calculator\",\"operatingSystem\":\"Any (Web Browser)\",\"offers\":{\"@type\":\"Offer\",\"price\":\"0\",\"priceCurrency\":\"EUR\"},\"creator\":{\"@type\":\"Organization\",\"name\":\"Vibromera\",\"url\":\"https:\/\/vibromera.eu\/\"},\"datePublished\":\"2025-01-01\",\"dateModified\":\"2026-02-14\",\"inLanguage\":\"en\",\"isAccessibleForFree\":true,\"featureList\":[\"Synchronous speed calculation\",\"Slip and slip frequency\",\"2\u00d7 line frequency\",\"Pole pass frequency\",\"Rotor bar pass frequency\",\"Rotor bar sidebands\",\"Common motor presets\",\"Auto-calculation on input change\",\"URL parameter sharing\"],\"keywords\":\"motor electrical frequency, slip, pole pass, rotor bar, 2\u00d7 line, motor diagnostics\"}\n<\/script>\n\n<script type=\"application\/ld+json\">\n{\"@context\":\"https:\/\/schema.org\",\"@type\":\"FAQPage\",\"mainEntity\":[\n{\"@type\":\"Question\",\"name\":\"What is 2\u00d7 line frequency?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"2\u00d7 line frequency (100 Hz for 50 Hz systems, 120 Hz for 60 Hz systems) is the vibration frequency caused by the alternating magnetic field in an electric motor. It is always present at some level. Elevated 2\u00d7 line frequency can indicate electrical problems such as stator eccentricity, shorted laminations, unbalanced phase voltages, or loose iron.\"}},\n{\"@type\":\"Question\",\"name\":\"What indicates broken rotor bars?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"Broken rotor bars are indicated by sidebands around 1\u00d7 line frequency spaced at pole pass frequency (2 \u00d7 slip \u00d7 line frequency). In current spectrum analysis (MCSA), look for sidebands at f_line \u00b1 n \u00d7 pole_pass. In vibration, look for rotor bar pass frequency with sidebands at 2\u00d7 line frequency.\"}},\n{\"@type\":\"Question\",\"name\":\"How to distinguish electrical from mechanical unbalance?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"Key test: turn off power and observe coast-down. If the 1\u00d7 vibration drops instantly at power cutoff, the source is electrical (magnetic unbalance). If it decreases gradually with speed, the source is mechanical. Electrical unbalance at 1\u00d7 appears at exactly line frequency or 2\u00d7 line, while mechanical unbalance appears at shaft running speed.\"}},\n{\"@type\":\"Question\",\"name\":\"What is slip frequency?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"Slip frequency is the difference between the synchronous speed and actual rotor speed, expressed as a frequency: f_slip = s \u00d7 f_line, where s = (Ns - N)\/Ns. Slip is necessary for torque production in induction motors. Typical full-load slip is 1-5% depending on motor size and design.\"}},\n{\"@type\":\"Question\",\"name\":\"How to distinguish electrical from mechanical faults?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"Use the power-off test: electrical vibration disappears instantly when power is removed, while mechanical vibration decreases gradually with coast-down. Electrical faults typically produce vibration at exact multiples of line frequency (100\/120 Hz), while mechanical faults produce vibration at shaft speed and its multiples. Current signature analysis (MCSA) can further isolate rotor-specific faults.\"}}\n]}\n<\/script>\n\n<script type=\"application\/ld+json\">\n{\"@context\":\"https:\/\/schema.org\",\"@type\":\"BreadcrumbList\",\"itemListElement\":[\n{\"@type\":\"ListItem\",\"position\":1,\"name\":\"Home\",\"item\":\"https:\/\/vibromera.eu\/\"},\n{\"@type\":\"ListItem\",\"position\":2,\"name\":\"Calculators\",\"item\":\"https:\/\/vibromera.eu\/calculators\/\"},\n{\"@type\":\"ListItem\",\"position\":3,\"name\":\"Motor Electrical Frequencies\",\"item\":\"https:\/\/vibromera.eu\/calculators\/motor-electrical-frequencies\/\"}\n]}\n<\/script>\n\n<link rel=\"preconnect\" href=\"https:\/\/fonts.googleapis.com\">\n\n<link rel=\"preconnect\" href=\"https:\/\/fonts.gstatic.com\" crossorigin>\n\n<link href=\"https:\/\/fonts.googleapis.com\/css2?family=DM+Sans:ital,opsz,wght@0,9..40,300;0,9..40,400;0,9..40,500;0,9..40,600;0,9..40,700;1,9..40,400&#038;family=JetBrains+Mono:wght@400;500;600&#038;family=Fraunces:opsz,wght@9..144,700;9..144,800&#038;display=swap\" rel=\"stylesheet\">\n\n<link rel=\"stylesheet\" href=\"https:\/\/cdn.jsdelivr.net\/npm\/katex@0.16.11\/dist\/katex.min.css\">\n\n<style>\n:root {\n    --vc-bg: #f4f1ec;\n    --vc-surface: #ffffff;\n    --vc-surface-alt: #f8f6f2;\n    --vc-ink: #1a1a1a;\n    --vc-ink-secondary: #5a5650;\n    --vc-ink-muted: #8a857e;\n    --vc-accent: #c85a2a;\n    --vc-accent-hover: #b04d22;\n    --vc-accent-light: #fdf0ea;\n    --vc-blue: #2a5c8c;\n    --vc-blue-light: #eaf1f8;\n    --vc-green: #2a7a4b;\n    --vc-green-light: #eaf8ef;\n    --vc-yellow: #a67c00;\n    --vc-yellow-light: #fef9e8;\n    --vc-red: #b91c1c;\n    --vc-red-light: #fef2f2;\n    --vc-border: #d9d4cc;\n    --vc-border-light: #e8e4dd;\n    --vc-shadow: 0 1px 3px rgba(26,26,26,0.06), 0 4px 12px rgba(26,26,26,0.04);\n    --vc-shadow-lg: 0 4px 12px rgba(26,26,26,0.08), 0 16px 40px rgba(26,26,26,0.06);\n    --vc-radius: 8px;\n    --vc-radius-lg: 12px;\n    --vc-font: 'DM Sans', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;\n    --vc-mono: 'JetBrains Mono', 'Consolas', 'Monaco', monospace;\n    --vc-display: 'Fraunces', Georgia, serif;\n}\n\n.vc-calculator {\n    font-family: var(--vc-font);\n    font-size: 15px;\n    line-height: 1.65;\n    color: var(--vc-ink);\n    max-width: 960px;\n    margin: 0 auto;\n    padding: 20px 16px 40px;\n    -webkit-font-smoothing: antialiased;\n}\n.vc-calculator *, .vc-calculator *::before, .vc-calculator *::after { box-sizing: border-box; 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}\n.vc-faq-item.vc-open .vc-faq-chevron { transform:rotate(180deg); }\n.vc-faq-a { max-height:0; overflow:hidden; transition:max-height 0.35s; }\n.vc-faq-item.vc-open .vc-faq-a { max-height:1200px; }\n.vc-faq-a-inner { padding:14px 16px; border-top:1px solid var(--vc-border-light); font-size:14px; color:var(--vc-ink-secondary); }\n.vc-faq-a-inner p { margin:0 0 8px; }\n.vc-faq-a-inner p:last-child { margin-bottom:0; }\n.vc-faq-a-inner ul { margin:4px 0 8px 16px; padding:0; }\n.vc-faq-a-inner li { margin-bottom:3px; }\n\n\/* \u2500\u2500 RELATED \u2500\u2500 *\/\n.vc-related { display:flex; flex-wrap:wrap; gap:10px; margin-top:16px; }\n.vc-related-link { display:inline-block; padding:8px 16px; font-family:var(--vc-font); font-size:13px; font-weight:600; background:var(--vc-surface-alt); color:var(--vc-ink-secondary); border:1px solid var(--vc-border); border-radius:var(--vc-radius); text-decoration:none; transition:all 0.15s; }\n.vc-related-link:hover { border-color:var(--vc-accent); color:var(--vc-accent); background:var(--vc-accent-light); }\n\n\/* \u2500\u2500 PROMO \u2500\u2500 *\/\n.vc-promo { margin-top:24px; padding:20px; background:linear-gradient(135deg, var(--vc-accent-light), var(--vc-surface)); border:1px solid var(--vc-border); border-radius:var(--vc-radius-lg); display:flex; align-items:center; gap:16px; }\n.vc-promo-text { flex:1; font-size:14px; color:var(--vc-ink-secondary); }\n.vc-promo-text strong { color:var(--vc-ink); }\n.vc-promo-link { padding:8px 20px; font-size:13px; font-weight:700; color:#fff; background:var(--vc-accent); border-radius:var(--vc-radius); text-decoration:none; white-space:nowrap; transition:background 0.15s; }\n.vc-promo-link:hover { background:var(--vc-accent-hover); }\n\n\/* \u2500\u2500 FOOTER \u2500\u2500 *\/\n.vc-footer { text-align:center; padding:32px 16px; font-size:13px; color:var(--vc-ink-muted); }\n.vc-footer a { color:var(--vc-accent); text-decoration:none; }\n.vc-footer a:hover { text-decoration:underline; }\n.vc-footer-links { margin-top:8px; font-size:12px; }\n.vc-footer-links a { margin:0 8px; }\n\n\/* \u2500\u2500 PRINT \u2500\u2500 *\/\n@media print {\n    .vc-section-body { max-height:none!important; }\n    .vc-faq-a { max-height:none!important; }\n    .vc-results { max-height:none!important; padding:24px!important; }\n    .vc-copy-btn, .vc-section-chevron, .vc-faq-chevron, .vc-presets, .vc-promo { display:none!important; }\n}\n<\/style>\n\n<div class=\"vc-calculator\" id=\"vc-motor-elec\">\n\n<!-- Header -->\n<header class=\"vc-header\">\n    <p class=\"vc-header-eyebrow\">Free Engineering Tool #039<\/p>\n    <h1 class=\"vc-header-title\">Motor Electrical Defect Frequency Calculator<\/h1>\n    <p class=\"vc-header-subtitle\">Calculate synchronous speed, slip, 2&times; line frequency, pole pass frequency, rotor bar pass frequency, and diagnostic sidebands for electric motor analysis.<\/p>\n    <div class=\"vc-badges\">\n        <span class=\"vc-badge\">Slip<\/span>\n        <span class=\"vc-badge\">2&times; Line<\/span>\n        <span class=\"vc-badge\">Pole Pass<\/span>\n        <span class=\"vc-badge\">Rotor Bars<\/span>\n    <\/div>\n<\/header>\n\n<!-- Calculator Card -->\n<div class=\"vc-card\">\n    <form class=\"vc-form\" id=\"vc-form\" autocomplete=\"off\">\n        <div class=\"vc-form-grid\">\n            <div class=\"vc-field\">\n                <label class=\"vc-label\" for=\"vc-fline\">Line Frequency<\/label>\n                <select class=\"vc-select\" id=\"vc-fline\">\n                    <option value=\"50\" selected>50 Hz (Europe, Asia, Africa)<\/option>\n                    <option value=\"60\">60 Hz (Americas, Japan 60Hz)<\/option>\n                <\/select>\n            <\/div>\n            <div class=\"vc-field\">\n                <label class=\"vc-label\" for=\"vc-poles\">Number of Poles<\/label>\n                <select class=\"vc-select\" id=\"vc-poles\">\n                    <option value=\"2\">2 poles<\/option>\n                    <option value=\"4\" selected>4 poles<\/option>\n                    <option value=\"6\">6 poles<\/option>\n                    <option value=\"8\">8 poles<\/option>\n                <\/select>\n            <\/div>\n            <div class=\"vc-field\">\n                <label class=\"vc-label\" for=\"vc-rpm\">Motor Speed <span class=\"vc-label-hint\">(RPM)<\/span><\/label>\n                <input class=\"vc-input\" type=\"number\" id=\"vc-rpm\" inputmode=\"decimal\" step=\"any\" min=\"1\" placeholder=\"e.g. 1475\" value=\"1475\">\n            <\/div>\n            <div class=\"vc-field\">\n                <label class=\"vc-label\" for=\"vc-bars\">Rotor Bars <span class=\"vc-label-hint\">(optional)<\/span><\/label>\n                <input class=\"vc-input\" type=\"number\" id=\"vc-bars\" inputmode=\"numeric\" step=\"1\" min=\"0\" placeholder=\"e.g. 28 (leave empty if unknown)\" value=\"\">\n            <\/div>\n        <\/div>\n\n        <!-- Presets -->\n        <div class=\"vc-presets\">\n            <div class=\"vc-presets-label\">Quick presets<\/div>\n            <button type=\"button\" class=\"vc-preset-btn\" data-f=\"50\" data-p=\"2\" data-rpm=\"2970\" data-bars=\"\">2-pole 50 Hz, 2970 RPM<\/button>\n            <button type=\"button\" class=\"vc-preset-btn\" data-f=\"50\" data-p=\"4\" data-rpm=\"1475\" data-bars=\"\">4-pole 50 Hz, 1475 RPM<\/button>\n            <button type=\"button\" class=\"vc-preset-btn\" data-f=\"60\" data-p=\"2\" data-rpm=\"3560\" data-bars=\"\">2-pole 60 Hz, 3560 RPM<\/button>\n        <\/div>\n    <\/form>\n\n    <!-- Results -->\n    <div class=\"vc-results\" id=\"vc-results\">\n        <div class=\"vc-results-head\">\n            <h2 class=\"vc-results-title\">Results<\/h2>\n            <button type=\"button\" class=\"vc-copy-btn\" id=\"vc-copy-btn\">\n                <svg width=\"14\" height=\"14\" viewBox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\"><rect x=\"9\" y=\"9\" width=\"13\" height=\"13\" rx=\"2\"\/><path d=\"M5 15H4a2 2 0 01-2-2V4a2 2 0 012-2h9a2 2 0 012 2v1\"\/><\/svg>\n                Copy\n            <\/button>\n        <\/div>\n        <div class=\"vc-result-grid\">\n            <div class=\"vc-rcard vc-rcard-primary\">\n                <div class=\"vc-rcard-label\">Synchronous Speed<\/div>\n                <div class=\"vc-rcard-value\" id=\"vc-r-ns\">\u2014<\/div>\n            <\/div>\n            <div class=\"vc-rcard\">\n                <div class=\"vc-rcard-label\">Slip<\/div>\n                <div class=\"vc-rcard-value\" id=\"vc-r-slip\">\u2014<\/div>\n            <\/div>\n            <div class=\"vc-rcard\">\n                <div class=\"vc-rcard-label\">Slip Frequency<\/div>\n                <div class=\"vc-rcard-value\" id=\"vc-r-fslip\">\u2014<\/div>\n            <\/div>\n            <div class=\"vc-rcard\">\n                <div class=\"vc-rcard-label\">1&times; Line Frequency<\/div>\n                <div class=\"vc-rcard-value\" id=\"vc-r-1xline\">\u2014<\/div>\n            <\/div>\n            <div class=\"vc-rcard\">\n                <div class=\"vc-rcard-label\">2&times; Line Frequency<\/div>\n                <div class=\"vc-rcard-value\" id=\"vc-r-2xline\">\u2014<\/div>\n            <\/div>\n            <div class=\"vc-rcard\">\n                <div class=\"vc-rcard-label\">Pole Pass Frequency<\/div>\n                <div class=\"vc-rcard-value\" id=\"vc-r-ppf\">\u2014<\/div>\n            <\/div>\n            <div class=\"vc-rcard\">\n                <div class=\"vc-rcard-label\">Shaft Frequency (1&times;)<\/div>\n                <div class=\"vc-rcard-value\" id=\"vc-r-fshaft\">\u2014<\/div>\n            <\/div>\n        <\/div>\n\n        <!-- Rotor bar section (conditional) -->\n        <div class=\"vc-rotor-section\" id=\"vc-rotor-section\" style=\"display:none;\">\n            <h3 style=\"font-family:var(--vc-display);font-size:17px;font-weight:700;margin:0 0 12px;\">Rotor Bar Analysis<\/h3>\n            <div class=\"vc-result-grid\" style=\"margin-bottom:12px;\">\n                <div class=\"vc-rcard\">\n                    <div class=\"vc-rcard-label\">Rotor Bar Pass Frequency<\/div>\n                    <div class=\"vc-rcard-value\" id=\"vc-r-rbpf\">\u2014<\/div>\n                <\/div>\n            <\/div>\n            <h4 style=\"font-family:var(--vc-mono);font-size:12px;font-weight:600;text-transform:uppercase;letter-spacing:0.05em;color:var(--vc-ink-secondary);margin:12px 0 8px;\">Rotor Bar Sidebands (f<sub>line<\/sub> &plusmn; n &times; f<sub>pole pass<\/sub>)<\/h4>\n            <div style=\"overflow-x:auto;\">\n                <table class=\"vc-sb-table\" id=\"vc-rb-tbl\">\n                    <thead>\n                        <tr>\n                            <th>n<\/th>\n                            <th>f<sub>line<\/sub> &minus; n&times;PPF (Hz)<\/th>\n                            <th>f<sub>line<\/sub> + n&times;PPF (Hz)<\/th>\n                        <\/tr>\n                    <\/thead>\n                    <tbody id=\"vc-rb-body\"><\/tbody>\n                <\/table>\n            <\/div>\n        <\/div>\n    <\/div>\n<\/div>\n\n<!-- Theory & Reference -->\n<div class=\"vc-section vc-open\" id=\"vc-sec-theory\">\n    <button type=\"button\" class=\"vc-section-toggle\" aria-expanded=\"true\">\n        <span class=\"vc-section-toggle-text\">\n            <span class=\"vc-section-icon\">\ud83d\udcd8<\/span>\n            <span class=\"vc-section-title\">Theory &amp; Formulas<\/span>\n        <\/span>\n        <svg class=\"vc-section-chevron\" viewBox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\"><path d=\"M6 9l6 6 6-6\"\/><\/svg>\n    <\/button>\n    <div class=\"vc-section-body\">\n        <div class=\"vc-section-inner vc-theory\">\n            <h3>Synchronous Speed<\/h3>\n            <p>The synchronous speed of an AC induction motor depends on line frequency and number of poles:<\/p>\n            <div class=\"vc-formula-box\" id=\"vc-katex-ns\"><\/div>\n\n            <h3>Slip<\/h3>\n            <p>Slip is the difference between synchronous and actual rotor speed, expressed as a fraction or percentage:<\/p>\n            <div class=\"vc-formula-box\" id=\"vc-katex-slip\"><\/div>\n            <p>Typical full-load slip for standard induction motors is 1\u20135%.<\/p>\n\n            <h3>Slip Frequency<\/h3>\n            <div class=\"vc-formula-box\" id=\"vc-katex-fslip\"><\/div>\n\n            <h3>2&times; Line Frequency<\/h3>\n            <div class=\"vc-formula-box\" id=\"vc-katex-2xline\"><\/div>\n            <p>This frequency (100 Hz at 50 Hz supply, 120 Hz at 60 Hz) is always present in motor vibration due to the alternating magnetic field. Elevated 2\u00d7 line indicates electrical issues: unbalanced phases, air gap eccentricity, or stator winding faults.<\/p>\n\n            <h3>Pole Pass Frequency<\/h3>\n            <div class=\"vc-formula-box\" id=\"vc-katex-ppf\"><\/div>\n            <p>Pole pass frequency is a key indicator for broken rotor bar analysis. Sidebands at pole pass frequency around 1\u00d7 line frequency in current spectra (MCSA) are a classic rotor bar fault signature.<\/p>\n\n            <h3>Rotor Bar Pass Frequency<\/h3>\n            <div class=\"vc-formula-box\" id=\"vc-katex-rbpf\"><\/div>\n\n            <h3>Practical Example<\/h3>\n            <div class=\"vc-example-box\">\n                <div class=\"vc-example-title\">Example \u2014 4-pole motor, 50 Hz, 1475 RPM<\/div>\n                <p><strong>Given:<\/strong> f<sub>line<\/sub> = 50 Hz, Poles = 4, N = 1475 RPM<\/p>\n                <p>N<sub>s<\/sub> = 120 \u00d7 50 \/ 4 = <strong>1500 RPM<\/strong><\/p>\n                <p>s = (1500 \u2212 1475) \/ 1500 = <strong>1.67%<\/strong><\/p>\n                <p>f<sub>slip<\/sub> = 0.0167 \u00d7 50 = <strong>0.833 Hz<\/strong><\/p>\n                <p>2\u00d7 line = 2 \u00d7 50 = <strong>100 Hz<\/strong><\/p>\n                <p>Pole pass = s \u00d7 f<sub>line<\/sub> \u00d7 Poles = 0.0167 \u00d7 50 \u00d7 4 = <strong>3.33 Hz<\/strong><\/p>\n            <\/div>\n\n            <div class=\"vc-warning-box\">\n                <p style=\"margin:0;font-size:14px;color:var(--vc-ink-secondary);\"><strong>\u26a0\ufe0f Note:<\/strong> Motor speed varies with load. Ensure you use the actual measured speed under operating conditions, not the nameplate speed. A tachometer or strobe measurement gives the most accurate results for slip-dependent calculations.<\/p>\n            <\/div>\n        <\/div>\n    <\/div>\n<\/div>\n\n<!-- Related Calculators -->\n<div class=\"vc-section\" id=\"vc-sec-related\">\n    <button type=\"button\" class=\"vc-section-toggle\" aria-expanded=\"false\">\n        <span class=\"vc-section-toggle-text\">\n            <span class=\"vc-section-icon\">\ud83d\udd17<\/span>\n            <span class=\"vc-section-title\">Related Calculators<\/span>\n        <\/span>\n        <svg class=\"vc-section-chevron\" viewBox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\"><path d=\"M6 9l6 6 6-6\"\/><\/svg>\n    <\/button>\n    <div class=\"vc-section-body\">\n        <div class=\"vc-section-inner\">\n            <div class=\"vc-related\">\n                <a class=\"vc-related-link\" href=\"\/calculators\/bearing-defect-frequencies\/\">Bearing Defect Frequencies<\/a>\n                <a class=\"vc-related-link\" href=\"\/calculators\/gear-mesh-frequency\/\">Gear Mesh Frequency<\/a>\n                <a class=\"vc-related-link\" href=\"\/calculators\/blade-pass-frequency\/\">Blade Pass Frequency<\/a>\n                <a class=\"vc-related-link\" href=\"\/calculators\/vibration-velocity\/\">Vibration Velocity (ISO 10816)<\/a>\n                <a class=\"vc-related-link\" href=\"\/calculators\/residual-unbalance-iso1940\/\">Residual Unbalance (ISO 1940)<\/a>\n            <\/div>\n        <\/div>\n    <\/div>\n<\/div>\n\n<!-- FAQ -->\n<div class=\"vc-section\" id=\"vc-sec-faq\">\n    <button type=\"button\" class=\"vc-section-toggle\" aria-expanded=\"false\">\n        <span class=\"vc-section-toggle-text\">\n            <span class=\"vc-section-icon\">\u2753<\/span>\n            <span class=\"vc-section-title\">Frequently Asked Questions<\/span>\n        <\/span>\n        <svg class=\"vc-section-chevron\" viewBox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\"><path d=\"M6 9l6 6 6-6\"\/><\/svg>\n    <\/button>\n    <div class=\"vc-section-body\">\n        <div class=\"vc-section-inner\">\n            <div class=\"vc-faq-list\" id=\"vc-faq-list\"><\/div>\n        <\/div>\n    <\/div>\n<\/div>\n\n<!-- Promo -->\n<div class=\"vc-promo\">\n    <div class=\"vc-promo-text\">\n        <strong>Vibromera \u2014 Portable Balancing &amp; Vibration Analysis<\/strong><br>\n        Professional vibration analysis instruments for motor diagnostics, field balancing, and condition monitoring. Used in 50+ countries.\n    <\/div>\n    <a class=\"vc-promo-link\" href=\"https:\/\/vibromera.eu\/\" target=\"_blank\" rel=\"noopener\">Learn More<\/a>\n<\/div>\n\n<!-- Footer -->\n<footer class=\"vc-footer\">\n    <p>&copy; 2024\u20132026 <a href=\"https:\/\/vibromera.eu\/\">Vibromera<\/a> \u2014 Engineering Calculators<\/p>\n    <p style=\"font-size:12px;margin-top:4px;\">Motor electrical frequency formulas per standard induction motor theory. Last updated: February 2026<\/p>\n    <div class=\"vc-footer-links\">\n        <a href=\"\/calculators\/engineering-calculators\/\">All Calculators<\/a>\n        <a href=\"https:\/\/vibromera.eu\/contacts\/\">Contact<\/a>\n    <\/div>\n<\/footer>\n\n<\/div>\n\n<script src=\"https:\/\/cdn.jsdelivr.net\/npm\/katex@0.16.11\/dist\/katex.min.js\"><\/script>\n<script>\n(function() {\n    'use strict';\n\n    var SLUG = 'motor-electrical-frequencies';\n\n    function $(id) { return document.getElementById(id); }\n    function fmt(n, d) { if (isNaN(n) || !isFinite(n)) return '\u2014'; var f = n.toFixed(d === undefined ? 2 : d); return f.replace(\/(\\.\\d*?)0+$\/, '$1').replace(\/\\.$\/, ''); }\n\n    \/* \u2500\u2500 CALCULATION \u2500\u2500 *\/\n    function calculate() {\n        var fLine = parseFloat($('vc-fline').value);\n        var poles = parseInt($('vc-poles').value);\n        var RPM = parseFloat($('vc-rpm').value);\n        var bars = parseInt($('vc-bars').value) || 0;\n\n        if (!fLine || !poles || !RPM || RPM <= 0) {\n            $('vc-results').classList.remove('vc-visible');\n            return;\n        }\n\n        var Ns = 120 * fLine \/ poles;\n        var slip = (Ns - RPM) \/ Ns;\n        var slipPct = slip * 100;\n        var fSlip = slip * fLine;\n        var fShaft = RPM \/ 60;\n        var twoXLine = 2 * fLine;\n        var polePas = slip * fLine * poles;\n\n        \/\/ Display results\n        $('vc-r-ns').innerHTML = fmt(Ns, 0) + ' <span class=\"vc-rcard-unit\">RPM<\/span> <span class=\"vc-rcard-unit\">(' + fmt(Ns \/ 60, 2) + ' Hz)<\/span>';\n        $('vc-r-slip').innerHTML = fmt(slipPct, 2) + ' <span class=\"vc-rcard-unit\">%<\/span> <span class=\"vc-rcard-unit\">(s = ' + fmt(slip, 4) + ')<\/span>';\n        $('vc-r-fslip').innerHTML = fmt(fSlip, 3) + ' <span class=\"vc-rcard-unit\">Hz<\/span>';\n        $('vc-r-1xline').innerHTML = fmt(fLine, 0) + ' <span class=\"vc-rcard-unit\">Hz<\/span>';\n        $('vc-r-2xline').innerHTML = fmt(twoXLine, 0) + ' <span class=\"vc-rcard-unit\">Hz<\/span>';\n        $('vc-r-ppf').innerHTML = fmt(polePas, 3) + ' <span class=\"vc-rcard-unit\">Hz<\/span>';\n        $('vc-r-fshaft').innerHTML = fmt(fShaft, 2) + ' <span class=\"vc-rcard-unit\">Hz<\/span> <span class=\"vc-rcard-unit\">(' + fmt(RPM) + ' RPM)<\/span>';\n\n        \/\/ Rotor bar section\n        if (bars > 0) {\n            var rbpf = bars * RPM \/ 60;\n            $('vc-r-rbpf').innerHTML = fmt(rbpf, 2) + ' <span class=\"vc-rcard-unit\">Hz<\/span> <span class=\"vc-rcard-unit\">(' + fmt(rbpf \/ fShaft, 1) + '\u00d7 shaft)<\/span>';\n\n            \/\/ Rotor bar sidebands: fLine \u00b1 n \u00d7 polePas\n            var rbBody = $('vc-rb-body');\n            rbBody.innerHTML = '';\n            for (var n = 1; n <= 3; n++) {\n                var row = '<tr>';\n                row += '<td><strong>' + n + '<\/strong><\/td>';\n                row += '<td>' + fmt(fLine - n * polePas, 3) + '<\/td>';\n                row += '<td>' + fmt(fLine + n * polePas, 3) + '<\/td>';\n                row += '<\/tr>';\n                rbBody.innerHTML += row;\n            }\n            $('vc-rotor-section').style.display = 'block';\n        } else {\n            $('vc-rotor-section').style.display = 'none';\n        }\n\n        $('vc-results').classList.add('vc-visible');\n\n        \/\/ URL params\n        var u = new URL(window.location);\n        u.searchParams.set('fline', fLine);\n        u.searchParams.set('poles', poles);\n        u.searchParams.set('rpm', RPM);\n        if (bars > 0) u.searchParams.set('bars', bars);\n        else u.searchParams.delete('bars');\n        history.replaceState(null, '', u.toString());\n\n        \/\/ History\n        saveHistory({\n            fline: fLine, poles: poles, rpm: RPM, bars: bars || '',\n            _summary: poles + '-pole ' + fLine + 'Hz, ' + RPM + ' RPM, slip=' + fmt(slipPct, 1) + '%'\n        });\n    }\n\n    \/* \u2500\u2500 PRESETS \u2500\u2500 *\/\n    document.querySelectorAll('.vc-preset-btn').forEach(function(btn) {\n        btn.addEventListener('click', function(e) {\n            e.preventDefault();\n            $('vc-fline').value = this.getAttribute('data-f');\n            $('vc-poles').value = this.getAttribute('data-p');\n            $('vc-rpm').value = this.getAttribute('data-rpm');\n            $('vc-bars').value = this.getAttribute('data-bars') || '';\n            calculate();\n        });\n    });\n\n    \/* \u2500\u2500 AUTO-CALCULATE \u2500\u2500 *\/\n    $('vc-form').addEventListener('input', calculate);\n    $('vc-form').addEventListener('change', calculate);\n\n    \/* \u2500\u2500 COPY \u2500\u2500 *\/\n    $('vc-copy-btn').addEventListener('click', function() {\n        var barsVal = $('vc-bars').value;\n        var text = 'Motor Electrical Frequency Calculation\\n' +\n            '\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\\n' +\n            'Line frequency: ' + $('vc-fline').value + ' Hz\\n' +\n            'Poles: ' + $('vc-poles').value + '\\n' +\n            'Motor speed: ' + $('vc-rpm').value + ' RPM\\n' +\n            (barsVal ? 'Rotor bars: ' + barsVal + '\\n' : '') +\n            '\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\\n' +\n            'Synchronous speed: ' + $('vc-r-ns').textContent + '\\n' +\n            'Slip: ' + $('vc-r-slip').textContent + '\\n' +\n            'Slip frequency: ' + $('vc-r-fslip').textContent + '\\n' +\n            '2\u00d7 line frequency: ' + $('vc-r-2xline').textContent + '\\n' +\n            'Pole pass frequency: ' + $('vc-r-ppf').textContent + '\\n' +\n            (barsVal ? 'Rotor bar pass: ' + $('vc-r-rbpf').textContent + '\\n' : '') +\n            '\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\\n' +\n            'vibromera.eu\/calculators\/motor-electrical-frequencies\/';\n\n        if (navigator.clipboard) {\n            navigator.clipboard.writeText(text).then(function() {\n                var btn = $('vc-copy-btn');\n                btn.classList.add('vc-copied');\n                btn.innerHTML = '<svg width=\"14\" height=\"14\" viewBox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\"><polyline points=\"20 6 9 17 4 12\"\/><\/svg> Copied!';\n                setTimeout(function() {\n                    btn.classList.remove('vc-copied');\n                    btn.innerHTML = '<svg width=\"14\" height=\"14\" viewBox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\"><rect x=\"9\" y=\"9\" width=\"13\" height=\"13\" rx=\"2\"\/><path d=\"M5 15H4a2 2 0 01-2-2V4a2 2 0 012-2h9a2 2 0 012 2v1\"\/><\/svg> Copy';\n                }, 2000);\n            });\n        }\n    });\n\n    \/* \u2500\u2500 COLLAPSIBLE SECTIONS \u2500\u2500 *\/\n    document.querySelectorAll('.vc-section-toggle').forEach(function(btn) {\n        btn.addEventListener('click', function() {\n            var section = this.closest('.vc-section');\n            var isOpen = section.classList.contains('vc-open');\n            section.classList.toggle('vc-open');\n            this.setAttribute('aria-expanded', !isOpen);\n        });\n    });\n\n    \/* \u2500\u2500 FAQ \u2500\u2500 *\/\n    var faqData = [\n        { q: 'What is 2\u00d7 line frequency?', a: '<p>2\u00d7 line frequency (2FL) is 100 Hz for 50 Hz systems and 120 Hz for 60 Hz systems. It is the vibration frequency generated by the alternating magnetic attraction in the motor air gap (the magnetic field reverses twice per cycle, creating a force at 2\u00d7 the supply frequency).<\/p><p>It is always present in motor vibration at some level. Elevated 2FL can indicate:<\/p><ul><li>Stator eccentricity (uneven air gap)<\/li><li>Shorted stator laminations<\/li><li>Unbalanced supply voltage or phase problems<\/li><li>Loose stator iron<\/li><\/ul>' },\n        { q: 'What indicates broken rotor bars?', a: '<p>Broken rotor bars produce characteristic patterns in both vibration and current spectra:<\/p><ul><li><strong>Current spectrum (MCSA):<\/strong> Sidebands at f<sub>line<\/sub> \u00b1 n \u00d7 f<sub>pole pass<\/sub> around the supply frequency peak<\/li><li><strong>Vibration:<\/strong> Rotor bar pass frequency with sidebands at 2\u00d7 line frequency<\/li><li><strong>Amplitude modulation:<\/strong> The 1\u00d7 vibration amplitude varies at pole pass frequency rate<\/li><li><strong>Speed variation:<\/strong> Slight cyclic speed fluctuation at pole pass frequency<\/li><\/ul><p>The severity is judged by the amplitude difference (dB) between the line frequency peak and the pole-pass sidebands in the current spectrum.<\/p>' },\n        { q: 'How to distinguish electrical from mechanical unbalance?', a: '<p>Both electrical and mechanical unbalance produce vibration at or near 1\u00d7 shaft speed. The key tests:<\/p><ul><li><strong>Power-off test:<\/strong> Turn off power and observe. If vibration drops instantly at disconnect, it\\'s electrical. If it coasts down with speed, it\\'s mechanical.<\/li><li><strong>Frequency precision:<\/strong> Electrical unbalance peaks appear at exact line frequency or 2\u00d7 line. Mechanical unbalance appears at shaft running speed.<\/li><li><strong>Sidebands:<\/strong> Electrical problems show sidebands at slip frequency or pole pass frequency around line frequency harmonics.<\/li><\/ul>' },\n        { q: 'What is slip frequency?', a: '<p>Slip frequency is the electrical frequency corresponding to the difference between synchronous and actual rotor speed:<\/p><p><strong>f<sub>slip<\/sub> = s \u00d7 f<sub>line<\/sub><\/strong><\/p><p>where s = (N<sub>s<\/sub> \u2212 N) \/ N<sub>s<\/sub><\/p><p>Slip is essential for torque production in induction motors \u2014 without slip, no current is induced in the rotor. Typical full-load slip values:<\/p><ul><li>Large motors (>100 kW): 1\u20132%<\/li><li>Medium motors (10\u2013100 kW): 2\u20134%<\/li><li>Small motors (<10 kW): 3\u20135%<\/li><\/ul>' },\n        { q: 'How to distinguish electrical from mechanical faults?', a: '<p>Systematic approach to identifying fault origin:<\/p><ul><li><strong>Step 1 \u2014 Power-off test:<\/strong> Instantly disappearing vibration = electrical source<\/li><li><strong>Step 2 \u2014 Frequency analysis:<\/strong> Peaks at exact multiples of line frequency = electrical; peaks at shaft speed multiples = mechanical<\/li><li><strong>Step 3 \u2014 Sideband analysis:<\/strong> Slip-related sidebands = rotor electrical fault; bearing frequencies = mechanical<\/li><li><strong>Step 4 \u2014 Current analysis:<\/strong> Use MCSA to identify rotor bar, eccentricity, or stator faults independently of vibration<\/li><li><strong>Step 5 \u2014 Phase analysis:<\/strong> Electrical 2\u00d7 line is typically in-phase across all measurements; mechanical unbalance shows phase shift between positions<\/li><\/ul>' }\n    ];\n\n    var faqList = $('vc-faq-list');\n    faqData.forEach(function(faq) {\n        faqList.innerHTML += '<div class=\"vc-faq-item\"><button type=\"button\" class=\"vc-faq-q\"><span>' + faq.q + '<\/span><svg class=\"vc-faq-chevron\" viewBox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\"><path d=\"M6 9l6 6 6-6\"\/><\/svg><\/button><div class=\"vc-faq-a\"><div class=\"vc-faq-a-inner\">' + faq.a + '<\/div><\/div><\/div>';\n    });\n    faqList.addEventListener('click', function(e) {\n        var btn = e.target.closest('.vc-faq-q');\n        if (!btn) return;\n        btn.closest('.vc-faq-item').classList.toggle('vc-open');\n    });\n\n    \/* \u2500\u2500 HISTORY \u2500\u2500 *\/\n    function saveHistory(entry) {\n        var key = 'vc_history_' + SLUG;\n        var arr = [];\n        try { arr = JSON.parse(localStorage.getItem(key)) || []; } catch(e) {}\n        entry._ts = new Date().toISOString();\n        arr.unshift(entry);\n        if (arr.length > 10) arr = arr.slice(0, 10);\n        try { localStorage.setItem(key, JSON.stringify(arr)); } catch(e) {}\n    }\n\n    \/* \u2500\u2500 URL PARAMS \u2500\u2500 *\/\n    function loadParams() {\n        var p = new URLSearchParams(window.location.search);\n        if (p.has('fline')) $('vc-fline').value = p.get('fline');\n        if (p.has('poles')) $('vc-poles').value = p.get('poles');\n        if (p.has('rpm')) $('vc-rpm').value = p.get('rpm');\n        if (p.has('bars')) $('vc-bars').value = p.get('bars');\n    }\n\n    \/* \u2500\u2500 KATEX \u2500\u2500 *\/\n    function renderFormulas() {\n        try {\n            katex.render('N_s = \\\\frac{120 \\\\times f_{\\\\text{line}}}{P} \\\\quad [\\\\text{RPM}]', $('vc-katex-ns'), { displayMode: true, throwOnError: false });\n            katex.render('s = \\\\frac{N_s - N}{N_s}', $('vc-katex-slip'), { displayMode: true, throwOnError: false });\n            katex.render('f_{\\\\text{slip}} = s \\\\times f_{\\\\text{line}} \\\\quad [\\\\text{Hz}]', $('vc-katex-fslip'), { displayMode: true, throwOnError: false });\n            katex.render('2 \\\\times f_{\\\\text{line}} = 2FL \\\\quad [\\\\text{Hz}]', $('vc-katex-2xline'), { displayMode: true, throwOnError: false });\n            katex.render('f_{\\\\text{pole pass}} = s \\\\times f_{\\\\text{line}} \\\\times P \\\\quad [\\\\text{Hz}]', $('vc-katex-ppf'), { displayMode: true, throwOnError: false });\n            katex.render('f_{\\\\text{RBPF}} = N_{\\\\text{bars}} \\\\times \\\\frac{\\\\text{RPM}}{60} \\\\quad [\\\\text{Hz}]', $('vc-katex-rbpf'), { displayMode: true, throwOnError: false });\n        } catch(e) {}\n    }\n\n    \/* \u2500\u2500 INIT \u2500\u2500 *\/\n    function init() {\n        loadParams();\n        renderFormulas();\n        calculate();\n    }\n\n    if (document.readyState === 'loading') {\n        document.addEventListener('DOMContentLoaded', init);\n    } else {\n        init();\n    }\n})();\n<\/script>\n","protected":false},"excerpt":{"rendered":"<p>Free online motor electrical defect frequency calculator. Compute synchronous speed, slip, 2\u00d7 line frequency, pole pass frequency, rotor bar pass frequency, and sidebands for motor diagnostics.<\/p>","protected":false},"featured_media":0,"template":"","meta":{"ai_generated_summary":"","footnotes":""},"categories":[],"tags":[],"class_list":["post-100157","calculator","type-calculator","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/vibromera.eu\/bn\/wp-json\/wp\/v2\/calculator\/100157","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/vibromera.eu\/bn\/wp-json\/wp\/v2\/calculator"}],"about":[{"href":"https:\/\/vibromera.eu\/bn\/wp-json\/wp\/v2\/types\/calculator"}],"version-history":[{"count":1,"href":"https:\/\/vibromera.eu\/bn\/wp-json\/wp\/v2\/calculator\/100157\/revisions"}],"predecessor-version":[{"id":100471,"href":"https:\/\/vibromera.eu\/bn\/wp-json\/wp\/v2\/calculator\/100157\/revisions\/100471"}],"wp:attachment":[{"href":"https:\/\/vibromera.eu\/bn\/wp-json\/wp\/v2\/media?parent=100157"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/vibromera.eu\/bn\/wp-json\/wp\/v2\/categories?post=100157"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/vibromera.eu\/bn\/wp-json\/wp\/v2\/tags?post=100157"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}