{"id":100158,"date":"2026-02-15T20:21:35","date_gmt":"2026-02-15T20:21:35","guid":{"rendered":"https:\/\/vibromera.eu\/?post_type=calculator&#038;p=100158"},"modified":"2026-07-12T21:12:14","modified_gmt":"2026-07-12T21:12:14","slug":"motor-nameplate-current","status":"publish","type":"calculator","link":"https:\/\/vibromera.eu\/fr\/calculators\/motor-nameplate-current\/","title":{"rendered":"AC Motor Operating-Point Line-Current Estimate"},"content":{"rendered":"\n<script type=\"application\/ld+json\">{\"@context\":\"https:\/\/schema.org\",\"@type\":\"WebApplication\",\"name\":\"AC Motor Operating-Point Line-Current Estimate\",\"description\":\"Estimate single-phase or balanced three-phase motor line current from documented active power,power factor,voltage and optional efficiency at one operating point.\",\"url\":\"https:\/\/vibromera.eu\/calculators\/motor-nameplate-current\/\",\"applicationCategory\":\"Engineering Reference\",\"operatingSystem\":\"Any\",\"offers\":{\"@type\":\"Offer\",\"price\":\"0\",\"priceCurrency\":\"EUR\"},\"creator\":{\"@type\":\"Organization\",\"name\":\"Vibromera\",\"url\":\"https:\/\/vibromera.eu\/\"},\"dateModified\":\"2026-07-12\",\"inLanguage\":\"en\",\"isAccessibleForFree\":true}<\/script>\n<style>\n.mi-wrap{--ink:#17212b;--muted:#586675;--line:#d8e0e7;--soft:#f4f7f9;--blue:#1769aa;--blue2:#0f4f84;--warn:#fff7e5;max-width:980px;margin:0 auto;padding:20px 16px 46px;color:var(--ink);font:15px\/1.58 system-ui,-apple-system,\"Segoe UI\",sans-serif}.mi-wrap *{box-sizing:border-box}.mi-wrap [hidden]{display:none!important}.mi-hero{padding:38px 30px;border:1px solid var(--line);border-radius:18px;background:linear-gradient(135deg,#eef7ff,#fff 68%);box-shadow:0 10px 30px rgba(20,54,80,.07)}.mi-kicker{color:var(--blue);font-size:12px;font-weight:800;letter-spacing:.1em;text-transform:uppercase}.mi-hero h1{margin:8px 0 10px;font-size:clamp(27px,4vw,42px);line-height:1.12}.mi-lead{max-width:780px;margin:0;color:var(--muted);font-size:17px}.mi-badges{display:flex;flex-wrap:wrap;gap:8px;margin-top:18px}.mi-badge{padding:5px 10px;border:1px solid #b9d4e8;border-radius:999px;background:#fff;color:var(--blue2);font-size:12px;font-weight:700}.mi-main{display:grid;grid-template-columns:minmax(0,1fr);gap:18px;margin-top:20px}.mi-panel,.mi-section{border:1px solid var(--line);border-radius:14px;background:#fff;box-shadow:0 5px 18px rgba(23,33,43,.05)}.mi-panel{padding:24px}.mi-panel h2,.mi-section h2{margin:0 0 8px;font-size:21px}.mi-note{margin:0 0 18px;color:var(--muted)}.mi-grid{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:16px}.mi-field{display:flex;flex-direction:column;gap:6px}.mi-wide{grid-column:1\/-1}.mi-label{font-weight:750}.mi-help{color:var(--muted);font-size:12px}.mi-input,.mi-select,.mi-textarea{width:100%;border:1.5px solid #bcc9d3;border-radius:8px;background:#fff;color:var(--ink);font:inherit;padding:10px 12px}.mi-textarea{min-height:92px;resize:vertical}.mi-input:focus,.mi-select:focus,.mi-textarea:focus{outline:3px solid rgba(23,105,170,.16);border-color:var(--blue)}.mi-error{min-height:24px;margin:14px 0 0;color:#a22727;font-weight:700}.mi-results{margin-top:20px;border:1px solid #b9d4e8;border-radius:12px;background:#f7fbff;padding:20px}.mi-rhead{display:flex;justify-content:space-between;gap:14px;align-items:flex-start}.mi-rtitle{font-size:19px;font-weight:800}.mi-rsub{max-width:580px;text-align:right;color:var(--muted);font-size:12px}.mi-rgrid{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:11px;margin-top:14px}.mi-card{padding:14px;border:1px solid #d7e5f0;border-radius:10px;background:#fff}.mi-card h3{margin:0 0 7px;color:var(--muted);font-size:12px;text-transform:uppercase;letter-spacing:.04em}.mi-val{font-size:20px;font-weight:800;overflow-wrap:anywhere}.mi-unit{margin-top:3px;color:var(--muted);font-size:11px}.mi-alert{margin-top:18px;padding:15px 17px;border:1px solid #e8cf91;border-radius:10px;background:var(--warn);color:#624b13}.mi-section{margin-top:18px;padding:22px 24px}.mi-section p{margin:8px 0;color:var(--muted)}.mi-section ul{margin:10px 0 0;padding-left:22px;color:var(--muted)}.mi-code{font-family:ui-monospace,SFMono-Regular,Consolas,monospace;color:#113d62}.mi-table{width:100%;border-collapse:collapse;margin-top:12px}.mi-table th,.mi-table td{padding:10px;border:1px solid var(--line);text-align:left;vertical-align:top}.mi-table th{background:var(--soft)}.mi-section a{color:var(--blue2)}@media(max-width:700px){.mi-grid,.mi-rgrid{grid-template-columns:1fr}.mi-wide{grid-column:auto}.mi-hero{padding:26px 20px}.mi-panel,.mi-section{padding:19px}.mi-rhead{display:block}.mi-rsub{text-align:left;margin-top:5px}}@media print{.mi-wrap{max-width:none}.mi-hero,.mi-panel,.mi-section{box-shadow:none}}\n<\/style>\n<div class=\"mi-wrap\">\n<header class=\"mi-hero\"><div class=\"mi-kicker\">Documented operating point \u00b7 RMS quantities \u00b7 no automatic equipment selection<\/div><h1>AC Motor Operating-Point Line-Current Estimate<\/h1><p class=\"mi-lead\">Estimate current from active power,voltage and power factor for one single-phase sinusoidal or balanced three-phase sinusoidal operating point. If the manufacturer states rated current,use that value for the rated configuration instead of reconstructing it here.<\/p><div class=\"mi-badges\"><span class=\"mi-badge\">Starts blank<\/span><span class=\"mi-badge\">Single operating point<\/span><span class=\"mi-badge\">True power-factor definition<\/span><span class=\"mi-badge\">Not cable\/protection sizing<\/span><\/div><\/header>\n<main class=\"mi-main\"><section class=\"mi-panel\"><h2>Document the electrical state<\/h2><p class=\"mi-note\">Voltage,power,power factor and efficiency must describe the same stable state and wiring configuration. The three-phase model requires symmetric sinusoidal line quantities.<\/p><form id=\"mi-form\" novalidate><div class=\"mi-grid\">\n<div class=\"mi-field\"><label class=\"mi-label\" for=\"mi-model\">Supply model<\/label><select class=\"mi-select\" id=\"mi-model\"><option value=\"\">Select\u2026<\/option><option value=\"three-balanced-sinusoidal\">Balanced three-phase sinusoidal<\/option><option value=\"single-sinusoidal\">Single-phase sinusoidal<\/option><\/select><\/div>\n<div class=\"mi-field\"><label class=\"mi-label\" for=\"mi-basis\">Power basis<\/label><select class=\"mi-select\" id=\"mi-basis\"><option value=\"\">Select\u2026<\/option><option value=\"shaft-output\">Shaft output power Pout;efficiency required<\/option><option value=\"input-active\">Electrical active input power Pin;efficiency not used<\/option><\/select><\/div>\n<div class=\"mi-field\"><label class=\"mi-label\" for=\"mi-power\">Documented power P (kW)<\/label><input class=\"mi-input\" id=\"mi-power\" inputmode=\"decimal\" autocomplete=\"off\"><span class=\"mi-help\" id=\"mi-power-help\">Select a power basis.<\/span><\/div>\n<div class=\"mi-field\"><label class=\"mi-label\" for=\"mi-voltage\">RMS voltage U (V)<\/label><input class=\"mi-input\" id=\"mi-voltage\" inputmode=\"decimal\" autocomplete=\"off\"><span class=\"mi-help\" id=\"mi-voltage-help\">Three-phase:line-to-line RMS. Single-phase:terminal RMS.<\/span><\/div>\n<div class=\"mi-field\"><label class=\"mi-label\" for=\"mi-pf\">Power factor \u03bb=P<sub>in<\/sub>\/S<\/label><input class=\"mi-input\" id=\"mi-pf\" inputmode=\"decimal\" autocomplete=\"off\"><span class=\"mi-help\">Ratio for this operating point,0&lt;\u03bb\u22641. Under sinusoidal conditions this equals |cos\u03c6|.<\/span><\/div>\n<div class=\"mi-field\" id=\"mi-eff-field\" hidden><label class=\"mi-label\" for=\"mi-eff\">Efficiency \u03b7=P<sub>out<\/sub>\/P<sub>in<\/sub><\/label><input class=\"mi-input\" id=\"mi-eff\" inputmode=\"decimal\" autocomplete=\"off\"><span class=\"mi-help\">Applicable measured,manufacturer or test value at this same point,0&lt;\u03b7\u22641.<\/span><\/div>\n<div class=\"mi-field mi-wide\"><label class=\"mi-label\" for=\"mi-source\">Motor,state and source record<\/label><textarea class=\"mi-textarea\" id=\"mi-source\" maxlength=\"1800\" placeholder=\"Motor and connection identity;supply or converter;frequency\/speed\/load;power,voltage,power-factor and efficiency sources;measurement dates\/methods;phase balance and waveform evidence\"><\/textarea><\/div>\n<\/div><p class=\"mi-error\" id=\"mi-error\" role=\"alert\"><\/p><\/form>\n<section class=\"mi-results\" id=\"mi-results\" hidden data-json=\"\"><div class=\"mi-rhead\"><div class=\"mi-rtitle\">Arithmetic estimate<\/div><div class=\"mi-rsub\" id=\"mi-summary\">\u2014<\/div><\/div><div class=\"mi-rgrid\">\n<article class=\"mi-card\"><h3>Estimated line current<\/h3><div class=\"mi-val\" id=\"mi-r-current\">\u2014<\/div><div class=\"mi-unit\">RMS under the selected model<\/div><\/article>\n<article class=\"mi-card\"><h3>Electrical active input<\/h3><div class=\"mi-val\" id=\"mi-r-pin\">\u2014<\/div><div class=\"mi-unit\">P<sub>in<\/sub><\/div><\/article>\n<article class=\"mi-card\"><h3>Apparent power<\/h3><div class=\"mi-val\" id=\"mi-r-s\">\u2014<\/div><div class=\"mi-unit\">S=P<sub>in<\/sub>\/\u03bb<\/div><\/article>\n<article class=\"mi-card\"><h3>Shaft output<\/h3><div class=\"mi-val\" id=\"mi-r-pout\">\u2014<\/div><div class=\"mi-unit\">reported only for output-power basis<\/div><\/article>\n<article class=\"mi-card\"><h3>Motor loss<\/h3><div class=\"mi-val\" id=\"mi-r-loss\">\u2014<\/div><div class=\"mi-unit\">P<sub>in<\/sub>\u2212P<sub>out<\/sub>;output-power basis only<\/div><\/article>\n<article class=\"mi-card\"><h3>Model<\/h3><div class=\"mi-val\" id=\"mi-r-model\">\u2014<\/div><div class=\"mi-unit\" id=\"mi-r-denom\">\u2014<\/div><\/article>\n<\/div><\/section>\n<div class=\"mi-alert\"><strong>Decision boundary:<\/strong> this is not a nameplate-current substitute,IEC acceptance result,starting-current estimate,or cable,contactor,overload-relay,breaker,fuse or protective-device sizing tool. Use manufacturer data and the applicable installation\/product rules.<\/div><\/section><\/main>\n<section class=\"mi-section\"><h2>Equations and units<\/h2><table class=\"mi-table\"><thead><tr><th>Model<\/th><th>Derived current equation<\/th><th>Required voltage<\/th><\/tr><\/thead><tbody><tr><td>Single-phase sinusoidal<\/td><td><span class=\"mi-code\">I=P<sub>in<\/sub>\u00b71000\/(U\u00b7\u03bb)<\/span><\/td><td>Terminal RMS voltage U<\/td><\/tr><tr><td>Balanced three-phase sinusoidal<\/td><td><span class=\"mi-code\">I<sub>L<\/sub>=P<sub>in<\/sub>\u00b71000\/(\u221a3\u00b7U<sub>LL<\/sub>\u00b7\u03bb)<\/span><\/td><td>Line-to-line RMS voltage U<sub>LL<\/sub><\/td><\/tr><\/tbody><\/table><p>For an output-power input,<span class=\"mi-code\">P<sub>in<\/sub>=P<sub>out<\/sub>\/\u03b7<\/span>. For an active-input-power input,no efficiency is applied. Power is entered in kW and multiplied by1000 to use watts with volts and amperes. \u03bb and \u03b7 are dimensionless.<\/p><p>The three-phase expression follows from the symmetric sinusoidal active-power relation. The single-phase expression follows from <span class=\"mi-code\">S=UI<\/span> and <span class=\"mi-code\">\u03bb=|P|\/S<\/span>. These are general electrical relations and a derivation from definitions\u2014not a calculator or acceptance formula prescribed by IEC60034.<\/p><\/section>\n<section class=\"mi-section\"><h2>Sources and standard boundary<\/h2><p>IEC Electropedia defines rotating-machine <a href=\"https:\/\/www.electropedia.org\/iev\/iev.nsf\/display?ievref=411-53-08&amp;openform=\" target=\"_blank\" rel=\"noopener\">efficiency,IEV411-53-08<\/a>,as active output divided by active input power;defines <a href=\"https:\/\/www.electropedia.org\/iev\/iev.nsf\/display?ievref=131-11-46&amp;openform=\" target=\"_blank\" rel=\"noopener\">power factor,IEV131-11-46<\/a>,as |P|\/S under periodic conditions;and defines <a href=\"https:\/\/www.electropedia.org\/iev\/iev.nsf\/display?ievref=131-11-41&amp;openform=\" target=\"_blank\" rel=\"noopener\">apparent power,IEV131-11-41<\/a>,as RMS voltage times RMS current for a two-terminal circuit. IEV141-03-11 gives <a href=\"https:\/\/www.electropedia.org\/iev\/iev.nsf\/display?ievref=141-03-11&amp;openform=\" target=\"_blank\" rel=\"noopener\">P=\u221a3UIcos\u03c6<\/a> only for a symmetric sinusoidal three-phase line.<\/p><p><a href=\"https:\/\/webstore.iec.ch\/en\/publication\/89961\" target=\"_blank\" rel=\"noopener\">IEC60034-1:2026,Edition15<\/a> is the current rating-and-performance standard and replaced the2022 edition. <a href=\"https:\/\/webstore.iec.ch\/en\/publication\/67756\" target=\"_blank\" rel=\"noopener\">IEC60034-2-1:2024,Edition3<\/a> covers test methods for losses and efficiency of mains-operated machines. <a href=\"https:\/\/webstore.iec.ch\/en\/publication\/67758\" target=\"_blank\" rel=\"noopener\">IEC60034-2-3:2024,Edition2<\/a> covers converter-fed motor efficiency and explicitly distinguishes standardized comparison conditions from a specific final converter application. Exact rating\/marking,test-method,tolerance and installation requirements remain <span class=\"mi-code\">NEEDS_LICENSED_SOURCE<\/span>.<\/p><\/section>\n<section class=\"mi-section\"><h2>Applicability and interpretation<\/h2><ul><li>Use rated current printed by the manufacturer for the stated rated voltage,frequency,connection and duty whenever it is available. Reconstructed current is only an estimate from the entered operating-point data.<\/li><li>Power factor and efficiency vary with load,speed,frequency,temperature and supply. Motor current is not generally proportional to shaft load because magnetizing current and losses remain and \u03bb and \u03b7 change.<\/li><li>For an unbalanced supply,calculate or measure each phase with an appropriate polyphase method. One line-to-line voltage and one current cannot represent the phase set.<\/li><li>For PWM\/converter supply,harmonics and measurement definitions matter. Do not substitute displacement cos\u03c6 for total \u03bb unless the waveform\/method makes them equivalent;use applicable motor-plus-converter data.<\/li><li>Do not use this result for starting,inrush,locked-rotor,transient,protection or conductor sizing.<\/li><\/ul><\/section>\n<section class=\"mi-section\"><h2>What was corrected<\/h2><p>The former formula was arithmetically valid only when every input represented the same appropriate operating point,but the page called the result nameplate FLA,used an unqualified cos\u03c6,preloaded typical values and accepted negative or greater-than-one efficiency\/power factor in JavaScript. Any phase selector value other than3 silently used the single-phase branch.<\/p><p>The replacement starts blank,uses strict complete-number parsing,requires an explicit model\/power basis\/source record,enforces0&lt;\u03bb\u22641 and0&lt;\u03b7\u22641,and separates active-input from shaft-output power. Unsupported typical IE ranges,DC-support claim,presets,local history,automatic copy markup and the claim that current is proportional to load were removed.<\/p><\/section>\n<\/div>\n<script>(function(){'use strict';function $(id){return document.getElementById(id)}function num(s){s=String(s).trim();if(!s||s.includes('.')&&s.includes(',')||!\/^[+-]?(?:\\d+(?:[.,]\\d*)?|[.,]\\d+)(?:[eE][+-]?\\d+)?$\/.test(s))return NaN;var n=Number(s.replace(',','.'));return Number.isFinite(n)&&Math.abs(n)<=1e100?n:NaN}function fmt(n){if(n===0)return'0';var a=Math.abs(n);return a>=1e12||a<1e-8?n.toExponential(9):Number(n.toPrecision(12)).toLocaleString('en-US',{maximumFractionDigits:20})}function clear(){['mi-r-current','mi-r-pin','mi-r-s','mi-r-pout','mi-r-loss','mi-r-model','mi-r-denom','mi-summary'].forEach(function(id){$(id).textContent='\u2014'});$('mi-results').hidden=true;$('mi-results').dataset.json=''}function fail(m){clear();$('mi-error').textContent=m}function sync(){var basis=$('mi-basis').value,model=$('mi-model').value;$('mi-eff-field').hidden=basis!=='shaft-output';if(basis!=='shaft-output')$('mi-eff').value='';$('mi-power-help').textContent=basis==='shaft-output'?'Mechanical shaft output power for this state.':basis==='input-active'?'Electrical active input power for this state.':'Select a power basis.';$('mi-voltage-help').textContent=model==='three-balanced-sinusoidal'?'Line-to-line RMS voltage for the symmetric three-phase state.':model==='single-sinusoidal'?'Terminal RMS voltage for the single-phase state.':'Three-phase:line-to-line RMS. 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I = P \/ (\u221a3 \u00d7 V \u00d7 cos \u03c6 \u00d7 \u03b7) pour un moteur triphas\u00e9, I = P \/ (V \u00d7 cos \u03c6 \u00d7 \u03b7) pour un moteur monophas\u00e9. Calculez l&#039;intensit\u00e9 nominale \u00e0 partir des donn\u00e9es de la plaque signal\u00e9tique.<\/p>","protected":false},"featured_media":0,"template":"","meta":{"ai_generated_summary":"","footnotes":""},"categories":[],"tags":[],"class_list":["post-100158","calculator","type-calculator","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/vibromera.eu\/fr\/wp-json\/wp\/v2\/calculator\/100158","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/vibromera.eu\/fr\/wp-json\/wp\/v2\/calculator"}],"about":[{"href":"https:\/\/vibromera.eu\/fr\/wp-json\/wp\/v2\/types\/calculator"}],"version-history":[{"count":3,"href":"https:\/\/vibromera.eu\/fr\/wp-json\/wp\/v2\/calculator\/100158\/revisions"}],"predecessor-version":[{"id":102494,"href":"https:\/\/vibromera.eu\/fr\/wp-json\/wp\/v2\/calculator\/100158\/revisions\/102494"}],"wp:attachment":[{"href":"https:\/\/vibromera.eu\/fr\/wp-json\/wp\/v2\/media?parent=100158"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/vibromera.eu\/fr\/wp-json\/wp\/v2\/categories?post=100158"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/vibromera.eu\/fr\/wp-json\/wp\/v2\/tags?post=100158"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}