{"id":1826,"date":"2026-07-27T10:31:49","date_gmt":"2026-07-27T02:31:49","guid":{"rendered":"https:\/\/jutrion.com\/?page_id=1826"},"modified":"2026-07-27T10:35:00","modified_gmt":"2026-07-27T02:35:00","slug":"%d0%ba%d0%b0%d0%bb%d1%8c%d0%ba%d1%83%d0%bb%d1%8f%d1%82%d0%be%d1%80-%d0%b2%d1%8b%d0%b1%d0%be%d1%80%d0%b0-%d0%ba%d0%be%d0%bd%d1%82%d0%b0%d0%ba%d1%82%d0%be%d1%80%d0%b0-%d0%bf%d0%b5%d1%80%d0%b5%d0%bc","status":"publish","type":"page","link":"https:\/\/jutrion.com\/ru\/tools\/ac-contactor-sizing-calculator\/","title":{"rendered":"\u041a\u0430\u043b\u044c\u043a\u0443\u043b\u044f\u0442\u043e\u0440 \u0432\u044b\u0431\u043e\u0440\u0430 \u043a\u043e\u043d\u0442\u0430\u043a\u0442\u043e\u0440\u0430 \u043f\u0435\u0440\u0435\u043c\u0435\u043d\u043d\u043e\u0433\u043e \u0442\u043e\u043a\u0430"},"content":{"rendered":"\n<!-- ===== JUTRION AC Contactor Sizing Calculator \u2014 paste into a WordPress \"Custom HTML\" block ===== -->\n<div class=\"jt-calc\">\n  <p class=\"eyebrow\">Motor &amp; switching<\/p>\n  <h1>AC Contactor Sizing Calculator (Motor FLC &amp; AC-3)<\/h1>\n  <p class=\"tool-lede\">Enter the motor rating to estimate the full-load current (FLC) and the minimum AC-3 contactor rating you need. The motor nameplate current always governs the final choice \u2014 this is a fast starting point, not a substitute for the manufacturer&#8217;s table.<\/p>\n\n  <div class=\"jt-card\"><div class=\"jt-grid\">\n    <div class=\"jt-inputs\">\n      <div class=\"jt-field\"><label>Motor rating<\/label>\n        <div class=\"jt-inline\">\n          <input type=\"number\" id=\"jt-power\" value=\"11\" min=\"0\" step=\"0.1\" inputmode=\"decimal\" aria-label=\"Motor power value\">\n          <select id=\"jt-unit\" aria-label=\"Power unit\"><option value=\"kw\" selected>kW<\/option><option value=\"hp\">HP<\/option><\/select>\n        <\/div>\n      <\/div>\n      <div class=\"jt-field\"><label>Supply<\/label>\n        <div class=\"jt-seg\" id=\"jt-phase\"><button type=\"button\" data-ph=\"3\" aria-pressed=\"true\">Three-phase<\/button><button type=\"button\" data-ph=\"1\" aria-pressed=\"false\">Single-phase<\/button><\/div>\n      <\/div>\n      <div class=\"jt-field\"><label for=\"jt-volt\">Operational voltage (V)<\/label><input type=\"number\" id=\"jt-volt\" value=\"400\" min=\"1\" step=\"1\" inputmode=\"numeric\"><\/div>\n      <div class=\"jt-two\">\n        <div class=\"jt-field\"><label for=\"jt-eff\">Efficiency \u03b7<\/label><input type=\"number\" id=\"jt-eff\" value=\"0.90\" min=\"0.1\" max=\"1\" step=\"0.01\" inputmode=\"decimal\"><\/div>\n        <div class=\"jt-field\"><label for=\"jt-pf\">Power factor cos \u03c6<\/label><input type=\"number\" id=\"jt-pf\" value=\"0.85\" min=\"0.1\" max=\"1\" step=\"0.01\" inputmode=\"decimal\"><\/div>\n      <\/div>\n      <div class=\"jt-field\"><label for=\"jt-cat\">Switching duty<\/label>\n        <select id=\"jt-cat\"><option value=\"ac3\" selected>AC-3 \u2014 normal starting &amp; running (pumps, fans, compressors)<\/option><option value=\"ac4\">AC-4 \u2014 jogging, plugging, reversing (severe duty)<\/option><\/select>\n      <\/div>\n    <\/div>\n    <div class=\"jt-readout\">\n      <div><div class=\"jt-rl\">Full-load current (est.)<\/div><div class=\"jt-flc\"><span id=\"jt-flc\">\u2014<\/span> <span>A<\/span><\/div><\/div>\n      <div class=\"jt-rec\"><div class=\"k\">Minimum AC-3 rating needed<\/div><div class=\"v\" id=\"jt-min\">\u2014 A<\/div><\/div>\n      <div class=\"jt-rec\"><div class=\"k\">Next typical AC-3 frame<\/div><div class=\"v\" id=\"jt-frame\">\u2014<\/div><\/div>\n      <button type=\"button\" class=\"jt-copy\" id=\"jt-copy\">Copy result<\/button>\n    <\/div>\n  <\/div><\/div>\n\n  <div class=\"jt-content\">\n    <div class=\"jt-note\" id=\"jt-note-ac4\"><span>\u26a0<\/span><span><b>AC-4 duty selected.<\/b> Jogging, plugging, and frequent reversing cause much heavier contact wear than AC-3. Do not size on FLC alone \u2014 select from the manufacturer&#8217;s AC-4 rating table (significantly lower than AC-3 for the same frame), or move up one or more frame sizes.<\/span><\/div>\n\n    <h2>How the calculation works<\/h2>\n    <p>A contactor is chosen from the motor&#8217;s full-load current under the correct utilization category, not from the motor power alone. For a three-phase motor:<\/p>\n    <div class=\"jt-eq\">I = P \/ (\u221a3 \u00d7 V \u00d7 \u03b7 \u00d7 cos \u03c6)<\/div>\n    <p>For a single-phase motor: I = P \/ (V \u00d7 \u03b7 \u00d7 cos \u03c6). Horsepower is converted with 1 HP = 0.746 kW. The result estimates the range; the <b>motor nameplate current governs<\/b> the final comparison.<\/p>\n\n    <h2>Why the utilization category changes the answer<\/h2>\n    <div class=\"jt-table-wrap\"><table>\n      <thead><tr><th>Category<\/th><th>Typical duty<\/th><th>Effect on selection<\/th><\/tr><\/thead>\n      <tbody>\n        <tr><td>AC-1<\/td><td>Non-inductive \/ resistive (heaters)<\/td><td>Highest current per frame; not for motors<\/td><\/tr>\n        <tr><td>AC-3<\/td><td>Starting squirrel-cage motors, switching off while running<\/td><td>The normal basis for a direct-on-line motor contactor<\/td><\/tr>\n        <tr><td>AC-4<\/td><td>Inching, plugging, reversing before speed<\/td><td>Much lower permissible current per frame; size up<\/td><\/tr>\n      <\/tbody>\n    <\/table><\/div>\n\n    <h2>What this contactor does not do<\/h2>\n    <p>A contactor switches the power circuit; it does not protect the motor. Every motor circuit still needs an overload relay for sustained overcurrent and a short-circuit protective device (breaker or fuse), coordinated for the voltage and fault level. The coil is selected separately from the control voltage and does not have to match the motor voltage.<\/p>\n\n    <h2>Frequently asked questions<\/h2>\n    <div class=\"jt-faq\">\n      <details><summary>How do I size a contactor for a three-phase motor?<\/summary><p>Start from the motor nameplate full-load current at the operational voltage, select AC-3 for normal starting and stopping, and choose a contactor whose AC-3 rating equals or exceeds that current. Then coordinate an overload relay and a short-circuit device.<\/p><\/details>\n      <details><summary>Is the coil voltage the same as the motor voltage?<\/summary><p>No. The main contacts are chosen for the motor circuit; the coil for the control circuit. A contactor can switch a 400 V motor with a 24 V DC or 230 V AC coil.<\/p><\/details>\n      <details><summary>Why is AC-4 different from AC-3?<\/summary><p>AC-4 covers jogging, plugging, and frequent reversing, where both making and breaking occur at high motor current \u2014 far more contact wear, so the permissible current per frame is much lower.<\/p><\/details>\n    <\/div>\n\n    <div class=\"jt-cta\">\n      <h2>Ready to choose the contactor?<\/h2>\n      <p>With the required AC-3 rating, compare configurations, coil options, and auxiliary contacts, or send the load and coil requirements for a recommendation.<\/p>\n      <div class=\"jt-cta-btns\">\n        <a class=\"jt-btn\" href=\"https:\/\/jutrion.com\/ac-contactor\/\">Explore JUTRION AC contactors<\/a>\n        <a class=\"jt-btn ghost\" href=\"https:\/\/jutrion.com\/contact\/\">Get a free quote<\/a>\n      <\/div>\n      <p class=\"jt-related\">Related products: <a href=\"https:\/\/jutrion.com\/ac-contactor\/\">AC Contactor<\/a> \u00b7 <a href=\"https:\/\/jutrion.com\/mccb\/\">MCCB<\/a> \u00b7 <a href=\"https:\/\/jutrion.com\/products\/\">All products<\/a><\/p>\n    <\/div>\n\n    <div class=\"jt-std\"><strong>Standards referenced<\/strong>IEC 60947-4-1 (electromechanical contactors &amp; motor-starters, AC-1 \/ AC-3 \/ AC-4 utilization categories).<\/div>\n    <p class=\"jt-fine\">Engineering estimate for guidance only. Final motor-circuit design, protection coordination, and product selection must be verified by a qualified person against the motor nameplate, the applicable standards, and the manufacturer&#8217;s datasheet.<\/p>\n  <\/div>\n<\/div>\n\n<script>\n(function(){\n  var $=function(id){return document.getElementById(id);};\n  var power=$('jt-power'),unit=$('jt-unit'),volt=$('jt-volt'),eff=$('jt-eff'),pf=$('jt-pf'),cat=$('jt-cat'),\n      flcEl=$('jt-flc'),minEl=$('jt-min'),frameEl=$('jt-frame'),note4=$('jt-note-ac4');\n  var phase=3, LADDER=[9,12,18,25,32,40,50,65,80,95,115,150,185,225,265,300,330,400,500,630,800];\n  document.querySelectorAll('#jt-phase button').forEach(function(b){b.addEventListener('click',function(){phase=parseInt(b.dataset.ph,10);document.querySelectorAll('#jt-phase button').forEach(function(x){x.setAttribute('aria-pressed',x===b?'true':'false');});if(phase===1&&(volt.value==='400'||volt.value==='690'))volt.value='230';if(phase===3&&volt.value==='230')volt.value='400';calc();});});\n  function nextFrame(i){for(var k=0;k<LADDER.length;k++){if(LADDER[k]>=i)return LADDER[k];}return null;}\n  function calc(){\n    var p=parseFloat(power.value),v=parseFloat(volt.value),e=parseFloat(eff.value),f=parseFloat(pf.value);\n    if(!(p>0&&v>0&&e>0&&f>0)){flcEl.textContent='\u2014';minEl.textContent='\u2014 A';frameEl.textContent='\u2014';return;}\n    var kw=unit.value==='hp'?p*0.746:p,w=kw*1000,denom=(phase===3?Math.sqrt(3)*v:v)*e*f,i=w\/denom,iR=Math.round(i*10)\/10;\n    flcEl.textContent=iR.toFixed(1);minEl.textContent=iR.toFixed(1)+' A';\n    var nf=nextFrame(i);frameEl.textContent=nf?(nf+' A'):'above 800 A \u2014 use MCCB \/ ACB switching';\n    note4.style.display=(cat.value==='ac4')?'flex':'none';\n  }\n  [power,unit,volt,eff,pf,cat].forEach(function(el){el.addEventListener('input',calc);el.addEventListener('change',calc);});\n  $('jt-copy').addEventListener('click',function(){var b=$('jt-copy');var txt='Motor: '+power.value+' '+unit.value.toUpperCase()+', '+(phase===3?'3-phase':'1-phase')+', '+volt.value+' V\\nEstimated FLC: '+flcEl.textContent+' A\\nMinimum AC-3 rating: '+minEl.textContent+'\\nNext typical AC-3 frame: '+frameEl.textContent;navigator.clipboard.writeText(txt).then(function(){var o=b.textContent;b.textContent='Copied \u2713';setTimeout(function(){b.textContent=o;},1500);}).catch(function(){b.textContent='Press Ctrl+C';});});\n  note4.style.display='none';calc();\n})();\n<\/script>\n<!-- ===== end block ===== -->\n\n","protected":false},"excerpt":{"rendered":"<p>Motor &amp; switching AC Contactor Sizing Calculator (Motor FLC &amp; AC-3) Enter the motor rating to estimate the full-load current (FLC) and the minimum AC-3 contactor rating you need. The motor nameplate current always governs the final choice \u2014 this is a fast starting point, not a substitute for the manufacturer&#8217;s table. Motor rating kWHP [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":1778,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-1826","page","type-page","status-publish","hentry"],"blocksy_meta":[],"_links":{"self":[{"href":"https:\/\/jutrion.com\/ru\/wp-json\/wp\/v2\/pages\/1826","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/jutrion.com\/ru\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/jutrion.com\/ru\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/jutrion.com\/ru\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/jutrion.com\/ru\/wp-json\/wp\/v2\/comments?post=1826"}],"version-history":[{"count":1,"href":"https:\/\/jutrion.com\/ru\/wp-json\/wp\/v2\/pages\/1826\/revisions"}],"predecessor-version":[{"id":1827,"href":"https:\/\/jutrion.com\/ru\/wp-json\/wp\/v2\/pages\/1826\/revisions\/1827"}],"up":[{"embeddable":true,"href":"https:\/\/jutrion.com\/ru\/wp-json\/wp\/v2\/pages\/1778"}],"wp:attachment":[{"href":"https:\/\/jutrion.com\/ru\/wp-json\/wp\/v2\/media?parent=1826"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}