{"id":1808,"date":"2026-07-27T10:32:46","date_gmt":"2026-07-27T02:32:46","guid":{"rendered":"https:\/\/jutrion.com\/?page_id=1808"},"modified":"2026-07-27T10:37:51","modified_gmt":"2026-07-27T02:37:51","slug":"%d8%ad%d8%a7%d8%b3%d8%a8%d8%a9-%d9%85%d8%b1%d8%ad%d9%84-%d8%a7%d9%84%d8%ad%d9%85%d9%84-%d8%a7%d9%84%d8%b2%d8%a7%d8%a6%d8%af-%d9%84%d9%84%d9%85%d8%ad%d8%b1%d9%83","status":"publish","type":"page","link":"https:\/\/jutrion.com\/ar\/tools\/motor-overload-relay-calculator\/","title":{"rendered":"\u062d\u0627\u0633\u0628\u0629 \u0636\u0628\u0637 \u0645\u0631\u062d\u0644 \u0627\u0644\u062d\u0645\u0644 \u0627\u0644\u0632\u0627\u0626\u062f \u0644\u0644\u0645\u062d\u0631\u0643"},"content":{"rendered":"\n<!-- ===== JUTRION Motor Overload Relay Setting \u2014 paste into a WordPress \"Custom HTML\" block ===== -->\n<div class=\"jt-calc\">\n  <p class=\"eyebrow\">Motor &amp; switching<\/p>\n  <h1>Motor Overload Relay Setting Calculator<\/h1>\n  <p class=\"tool-lede\">Turn the motor nameplate current, service factor, and starting duty into a preliminary thermal-overload dial setting and trip class for a contactor-mounted overload relay. The nameplate current governs \u2014 these are starting points to be trimmed on commissioning.<\/p>\n\n  <div class=\"jt-card\"><div class=\"jt-grid\">\n    <div class=\"jt-inputs\">\n      <div class=\"jt-field\"><label for=\"jt-flc\">Motor nameplate current \u2014 FLC (A)<\/label><input type=\"number\" id=\"jt-flc\" value=\"18\" min=\"0.1\" step=\"0.1\" inputmode=\"decimal\"><\/div>\n      <div class=\"jt-field\"><label for=\"jt-sf\">Service factor<\/label>\n        <select id=\"jt-sf\"><option value=\"1.0\">1.0 \u2014 no service factor<\/option><option value=\"1.15\" selected>1.15 \u2014 with service factor<\/option><\/select>\n      <\/div>\n      <div class=\"jt-field\"><label for=\"jt-start\">Starting duty<\/label>\n        <select id=\"jt-start\"><option value=\"10\" selected>Normal \u2014 start &lt; 10 s (pumps, fans)<\/option><option value=\"20\">Heavy \u2014 10\u201320 s (loaded conveyors)<\/option><option value=\"30\">Very heavy \u2014 &gt; 20 s (crushers, centrifuges)<\/option><\/select>\n      <\/div>\n      <div class=\"jt-field\"><label class=\"jt-check\"><input type=\"checkbox\" id=\"jt-amb\"> Relay ambient differs from motor (needs temperature compensation)<\/label><\/div>\n    <\/div>\n    <div class=\"jt-readout\">\n      <div><div class=\"jt-rl\">Recommended dial setting<\/div><div class=\"jt-big\"><span id=\"jt-set\">\u2014<\/span> <span>A<\/span><\/div><\/div>\n      <div class=\"jt-rec row\"><div class=\"k\">Setting range<\/div><div class=\"v\" id=\"jt-range\">\u2014<\/div><\/div>\n      <div class=\"jt-rec row\"><div class=\"k\">Trip class<\/div><div class=\"v\" id=\"jt-class\">\u2014<\/div><\/div>\n      <div class=\"jt-rec\"><div class=\"k\">Guidance<\/div><div class=\"v\" id=\"jt-guide\" style=\"font-size:13px\">\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    <h2>Setting: dial to the motor, not the cable<\/h2>\n    <p>A thermal overload relay protects the <b>motor windings<\/b>, so it is set from the motor&#8217;s actual full-load current, taken from the nameplate. The service factor sets the allowable margin above it:<\/p>\n    <div class=\"jt-eq\">Service factor 1.0   : set \u2248 100\u2013115 % of FLC\nService factor 1.15+ : set \u2248 115\u2013125 % of FLC<\/div>\n    <p>Start at the FLC on the dial and trim upward within the range only if the motor nuisance-trips at a genuinely acceptable load. Setting above the range removes winding protection; setting far below it causes nuisance trips.<\/p>\n\n    <h2>Trip class: match the start time<\/h2>\n    <div class=\"jt-table-wrap\"><table>\n      <thead><tr><th>Class<\/th><th>Trip time at 7.2 \u00d7 setting<\/th><th>Use<\/th><\/tr><\/thead>\n      <tbody>\n        <tr><td class=\"mono\">Class 10<\/td><td class=\"mono\">\u2264 10 s<\/td><td>Normal starting \u2014 pumps, fans, standard loads<\/td><\/tr>\n        <tr><td class=\"mono\">Class 20<\/td><td class=\"mono\">\u2264 20 s<\/td><td>Heavy starting \u2014 loaded conveyors, mixers<\/td><\/tr>\n        <tr><td class=\"mono\">Class 30<\/td><td class=\"mono\">\u2264 30 s<\/td><td>Very heavy \/ high-inertia \u2014 crushers, centrifuges<\/td><\/tr>\n      <\/tbody>\n    <\/table><\/div>\n    <p>The class must let the motor accelerate without tripping, yet still protect the windings during a stalled or locked-rotor condition. A long-starting motor on a Class 10 relay trips on every start; too high a class on a quick-starting motor slows protection.<\/p>\n\n    <div class=\"jt-note\"><span>\u26a0<\/span><span><b>Temperature compensation matters.<\/b> A non-compensated bimetallic relay shifts its trip point with its own ambient. Where the relay sits in a hot enclosure or a different ambient from the motor, use a temperature-compensated relay or apply the manufacturer&#8217;s correction.<\/span><\/div>\n\n    <h2>Frequently asked questions<\/h2>\n    <div class=\"jt-faq\">\n      <details><summary>Do I use the nameplate current or the cable rating?<\/summary><p>Always the motor nameplate FLC. The overload protects the motor; the cable and short-circuit protection are handled separately by the breaker or fuse.<\/p><\/details>\n      <details><summary>My motor trips during start \u2014 raise the setting?<\/summary><p>Usually no. First check the trip class matches the start time \u2014 a heavy or high-inertia load often needs Class 20 or 30. Only trim the current setting within its range, and never above the service-factor limit.<\/p><\/details>\n      <details><summary>Electronic overload or bimetallic?<\/summary><p>Electronic overloads offer wider setting ranges, selectable classes, phase-loss and phase-imbalance protection, and better temperature stability. Bimetallic relays are simple and economical for standard duties.<\/p><\/details>\n    <\/div>\n\n    <div class=\"jt-cta\">\n      <h2>Build the starter<\/h2>\n      <p>Pair the overload relay with a correctly rated AC contactor and short-circuit protection for a complete motor starter.<\/p>\n      <div class=\"jt-cta-btns\">\n        <a class=\"jt-btn\" href=\"https:\/\/jutrion.com\/ac-contactor\/\">Explore JUTRION 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\/relay\/\">Relay<\/a><\/p>\n    <\/div>\n\n    <div class=\"jt-std\"><strong>Standards referenced<\/strong>IEC 60947-4-1 (contactors &amp; motor-starters, overload relays &amp; trip classes) \u00b7 motor nameplate data.<\/div>\n    <p class=\"jt-fine\">Preliminary setting for guidance only. The final overload setting and trip class must be confirmed by a qualified person against the motor nameplate, the driven load, and the relay manufacturer&#8217;s data, then verified on commissioning.<\/p>\n  <\/div>\n<\/div>\n\n<script>\n(function(){\n  var $=function(id){return document.getElementById(id);};\n  var flc=$('jt-flc'),sf=$('jt-sf'),start=$('jt-start'),amb=$('jt-amb'),\n      setEl=$('jt-set'),rangeEl=$('jt-range'),classEl=$('jt-class'),guideEl=$('jt-guide');\n  function r1(x){return Math.round(x*10)\/10;}\n  function calc(){\n    var I=parseFloat(flc.value),s=parseFloat(sf.value);\n    if(!(I>0)){setEl.textContent='\u2014';rangeEl.textContent=classEl.textContent=guideEl.textContent='\u2014';return;}\n    var hiFac=(s>=1.15)?1.25:1.15;\n    var rec=(s>=1.15)?I*1.15:I; \/\/ start at FLC (or 115% with SF), trim up to limit\n    setEl.textContent=r1(rec);\n    rangeEl.textContent=r1(I)+' \u2013 '+r1(I*hiFac)+' A';\n    classEl.textContent='Class '+start.value;\n    guideEl.textContent=amb.checked?'Use a temperature-compensated relay':'Dial to nameplate, trim on test';\n  }\n  [flc,sf,start].forEach(function(el){el.addEventListener('input',calc);el.addEventListener('change',calc);});\n  amb.addEventListener('change',calc);\n  $('jt-copy').addEventListener('click',function(){var b=$('jt-copy');var txt='Motor FLC: '+flc.value+' A, SF '+sf.value+'\\nRecommended setting: '+setEl.textContent+' A\\nSetting range: '+rangeEl.textContent+'\\nTrip class: '+classEl.textContent+'\\nGuidance: '+guideEl.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  calc();\n})();\n<\/script>\n<!-- ===== end block ===== -->\n\n","protected":false},"excerpt":{"rendered":"<p>Motor &amp; switching Motor Overload Relay Setting Calculator Turn the motor nameplate current, service factor, and starting duty into a preliminary thermal-overload dial setting and trip class for a contactor-mounted overload relay. The nameplate current governs \u2014 these are starting points to be trimmed on commissioning. Motor nameplate current \u2014 FLC (A) Service factor 1.0 [&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-1808","page","type-page","status-publish","hentry"],"blocksy_meta":[],"_links":{"self":[{"href":"https:\/\/jutrion.com\/ar\/wp-json\/wp\/v2\/pages\/1808","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/jutrion.com\/ar\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/jutrion.com\/ar\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/jutrion.com\/ar\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/jutrion.com\/ar\/wp-json\/wp\/v2\/comments?post=1808"}],"version-history":[{"count":1,"href":"https:\/\/jutrion.com\/ar\/wp-json\/wp\/v2\/pages\/1808\/revisions"}],"predecessor-version":[{"id":1809,"href":"https:\/\/jutrion.com\/ar\/wp-json\/wp\/v2\/pages\/1808\/revisions\/1809"}],"up":[{"embeddable":true,"href":"https:\/\/jutrion.com\/ar\/wp-json\/wp\/v2\/pages\/1778"}],"wp:attachment":[{"href":"https:\/\/jutrion.com\/ar\/wp-json\/wp\/v2\/media?parent=1808"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}