{"id":1814,"date":"2026-07-27T10:32:32","date_gmt":"2026-07-27T02:32:32","guid":{"rendered":"https:\/\/jutrion.com\/?page_id=1814"},"modified":"2026-07-27T10:35:12","modified_gmt":"2026-07-27T02:35:12","slug":"acb-lsig-%ec%84%a4%ec%a0%95-%ec%9b%8c%ed%81%ac%ec%8b%9c%ed%8a%b8","status":"publish","type":"page","link":"https:\/\/jutrion.com\/ko\/tools\/acb-lsig-setting-worksheet\/","title":{"rendered":"acb lsig \uc124\uc815"},"content":{"rendered":"\n<!-- ===== JUTRION ACB Frame & LSIG Setting Worksheet \u2014 paste into a WordPress \"Custom HTML\" block ===== -->\n<div class=\"jt-calc\">\n  <p class=\"eyebrow\">Circuit protection<\/p>\n  <h1>ACB Frame &amp; LSIG Trip-Setting Worksheet<\/h1>\n  <p class=\"tool-lede\">Build preliminary air circuit breaker frame size and Long-time, Short-time, Instantaneous, and Ground-fault (LSIG) setting ranges from the feeder load current, cable capacity, fault level, and the largest downstream device. Starting ranges for a coordination study \u2014 final settings come from the manufacturer&#8217;s curves.<\/p>\n\n  <div class=\"jt-card\"><div class=\"jt-grid\">\n    <div class=\"jt-inputs\">\n      <div class=\"jt-two\">\n        <div class=\"jt-field\"><label for=\"jt-ib\">Feeder design current I<sub>b<\/sub> (A)<\/label><input type=\"number\" id=\"jt-ib\" value=\"1500\" min=\"1\" step=\"10\" inputmode=\"numeric\"><\/div>\n        <div class=\"jt-field\"><label for=\"jt-iz\">Busbar \/ cable capacity I<sub>z<\/sub> (A)<\/label><input type=\"number\" id=\"jt-iz\" value=\"2000\" min=\"1\" step=\"10\" inputmode=\"numeric\"><\/div>\n      <\/div>\n      <div class=\"jt-two\">\n        <div class=\"jt-field\"><label for=\"jt-isc\">Prospective I<sub>sc<\/sub> (kA)<\/label><input type=\"number\" id=\"jt-isc\" value=\"50\" min=\"1\" step=\"1\" inputmode=\"numeric\"><\/div>\n        <div class=\"jt-field\"><label for=\"jt-down\">Largest downstream device (A)<\/label><input type=\"number\" id=\"jt-down\" value=\"400\" min=\"0\" step=\"10\" inputmode=\"numeric\"><\/div>\n      <\/div>\n      <div class=\"jt-note\"><span>\u24d8<\/span><span>Long-time protects the cable (I<sub>b<\/sub> \u2264 I<sub>r<\/sub> \u2264 I<sub>z<\/sub>). Short-time is set above the downstream device so the ACB holds during a downstream fault \u2014 the basis of selectivity.<\/span><\/div>\n    <\/div>\n    <div class=\"jt-readout\">\n      <div><div class=\"jt-rl\">ACB frame I<sub>n<\/sub><\/div><div class=\"jt-level\" id=\"jt-frame\">\u2014<\/div><\/div>\n      <div class=\"jt-rec row\"><div class=\"k\">L \u2014 Long-time I<sub>r<\/sub><\/div><div class=\"v\" id=\"jt-ir\">\u2014<\/div><\/div>\n      <div class=\"jt-rec row\"><div class=\"k\">S \u2014 Short-time I<sub>sd<\/sub><\/div><div class=\"v\" id=\"jt-isd\">\u2014<\/div><\/div>\n      <div class=\"jt-rec row\"><div class=\"k\">I \u2014 Instantaneous I<sub>i<\/sub><\/div><div class=\"v\" id=\"jt-ii\">\u2014<\/div><\/div>\n      <div class=\"jt-rec row\"><div class=\"k\">G \u2014 Ground fault I<sub>g<\/sub><\/div><div class=\"v\" id=\"jt-ig\">\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>What each LSIG band does<\/h2>\n    <div class=\"jt-table-wrap\"><table>\n      <thead><tr><th>Band<\/th><th>Function<\/th><th>Typical setting range<\/th><\/tr><\/thead>\n      <tbody>\n        <tr><td class=\"mono\">L<\/td><td>Long-time overload \u2014 protects the conductor<\/td><td class=\"mono\">I<sub>r<\/sub> = 0.4\u20131.0 \u00d7 I<sub>n<\/sub><\/td><\/tr>\n        <tr><td class=\"mono\">S<\/td><td>Short-time \u2014 rides through downstream faults for selectivity<\/td><td class=\"mono\">I<sub>sd<\/sub> = 1.5\u201310 \u00d7 I<sub>r<\/sub>, delay 0.1\u20130.4 s<\/td><\/tr>\n        <tr><td class=\"mono\">I<\/td><td>Instantaneous \u2014 clears close-up high faults<\/td><td class=\"mono\">I<sub>i<\/sub> = 2\u201315 \u00d7 I<sub>n<\/sub>, or OFF (ZSI)<\/td><\/tr>\n        <tr><td class=\"mono\">G<\/td><td>Ground fault \u2014 earth-fault pickup with delay<\/td><td class=\"mono\">I<sub>g<\/sub> = 0.2\u20131.0 \u00d7 I<sub>n<\/sub>, delay 0.1\u20130.5 s<\/td><\/tr>\n      <\/tbody>\n    <\/table><\/div>\n\n    <h2>How the worksheet builds the settings<\/h2>\n    <ul>\n      <li><b>Frame I<sub>n<\/sub>:<\/b> the next standard ACB frame at or above the feeder design current.<\/li>\n      <li><b>Long-time I<sub>r<\/sub>:<\/b> set to carry the load yet protect the conductor, so I<sub>b<\/sub> \u2264 I<sub>r<\/sub> \u2264 I<sub>z<\/sub>. The worksheet starts I<sub>r<\/sub> just above I<sub>b<\/sub>.<\/li>\n      <li><b>Short-time I<sub>sd<\/sub>:<\/b> raised above the downstream device&#8217;s clearing region with a short delay, so the ACB waits while the downstream breaker clears its own fault.<\/li>\n      <li><b>Instantaneous I<sub>i<\/sub>:<\/b> covers a close-up fault. It can be switched off where the ACB&#8217;s short-time withstand (I<sub>cw<\/sub>) and zone-selective interlocking provide full selectivity.<\/li>\n      <li><b>Ground fault I<sub>g<\/sub>:<\/b> a lower earth-fault pickup with a delay, coordinated with downstream earth-fault protection.<\/li>\n    <\/ul>\n    <div class=\"jt-note\"><span>\u26a0<\/span><span><b>These are starting ranges, not a coordination study.<\/b> Real selectivity, the short-time withstand rating I<sub>cw<\/sub>, and the delay grading must be verified against the actual manufacturer time\u2013current curves and the fault levels at each level of the installation.<\/span><\/div>\n\n    <h2>Frequently asked questions<\/h2>\n    <div class=\"jt-faq\">\n      <details><summary>Why turn the instantaneous band off?<\/summary><p>To achieve full selectivity with a downstream breaker, the ACB must hold during a downstream fault. If its short-time withstand (I<sub>cw<\/sub>) covers the fault level, the instantaneous element can be disabled so only the downstream device trips.<\/p><\/details>\n      <details><summary>What is I<sub>cw<\/sub> and why does it matter?<\/summary><p>I<sub>cw<\/sub> is the current the ACB can carry for a short, rated time (for example 0.5 s or 1 s) without tripping or damage. It sets how long the short-time delay can safely be, and therefore how much selectivity is achievable.<\/p><\/details>\n      <details><summary>ACB or MCCB for this feeder?<\/summary><p>ACBs suit large frames (typically 630\u20136300 A), high short-time withstand, and full LSIG adjustability for main and tie duties. Below that, or where breaking-only performance is enough, an MCCB is usually more economical.<\/p><\/details>\n    <\/div>\n\n    <div class=\"jt-cta\">\n      <h2>Select the ACB<\/h2>\n      <p>Match the frame, I<sub>cw<\/sub>, trip unit, and poles to a device, then confirm the settings with a coordination study.<\/p>\n      <div class=\"jt-cta-btns\">\n        <a class=\"jt-btn\" href=\"https:\/\/jutrion.com\/acb\/\">Explore JUTRION ACBs<\/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\/acb\/\">ACB<\/a> \u00b7 <a href=\"https:\/\/jutrion.com\/mccb\/\">MCCB<\/a> \u00b7 <a href=\"https:\/\/jutrion.com\/ats\/\">ATS<\/a><\/p>\n    <\/div>\n\n    <div class=\"jt-std\"><strong>Standards referenced<\/strong>IEC 60947-2 (circuit-breakers, I<sub>cu<\/sub>\/I<sub>cs<\/sub>\/I<sub>cw<\/sub>, trip units) \u00b7 IEC 60364-4-43 \/ 5-53 (overload, fault, and coordination).<\/div>\n    <p class=\"jt-fine\">Preliminary ranges for guidance only. Final frame, ratings, and LSIG settings must be established by a qualified person through a protection-coordination study using the manufacturer&#8217;s curves and the installation&#8217;s fault levels.<\/p>\n  <\/div>\n<\/div>\n\n<script>\n(function(){\n  var $=function(id){return document.getElementById(id);};\n  var ib=$('jt-ib'),iz=$('jt-iz'),isc=$('jt-isc'),down=$('jt-down'),\n      frameEl=$('jt-frame'),irEl=$('jt-ir'),isdEl=$('jt-isd'),iiEl=$('jt-ii'),igEl=$('jt-ig');\n  var FRAMES=[630,800,1000,1250,1600,2000,2500,3200,4000,5000,6300];\n  function nextFrame(x){for(var i=0;i<FRAMES.length;i++){if(FRAMES[i]>=x)return FRAMES[i];}return null;}\n  function r10(x){return Math.round(x\/10)*10;}\n  function calc(){\n    var Ib=parseFloat(ib.value),Iz=parseFloat(iz.value),D=parseFloat(down.value);\n    if(!(Ib>0)){frameEl.textContent='\u2014';irEl.textContent=isdEl.textContent=iiEl.textContent=igEl.textContent='\u2014';return;}\n    var In=nextFrame(Ib);\n    if(In===null){frameEl.textContent='> 6300 A';return;}\n    frameEl.textContent=In+' A';\n    var Ir=r10(Ib*1.05); if(Iz>0&&Ir>Iz)Ir=r10(Iz);\n    var frac=(Ir\/In); irEl.textContent=Ir+' A ('+frac.toFixed(2)+'\u00d7In)';\n    \/\/ short-time: above downstream, min 1.5x Ir, default ~6x Ir, capped 10x Ir\n    var isd=Math.max(6*Ir,(D>0?1.5*D*10:0));\n    isd=Math.min(isd,10*Ir); if(isd<1.5*Ir)isd=1.5*Ir;\n    isdEl.textContent=r10(isd)+' A ('+(isd\/Ir).toFixed(1)+'\u00d7Ir) \u00b7 delay ~0.2 s';\n    iiEl.textContent=(10*In)+' A (10\u00d7In) \u00b7 or OFF if Icw covers Isc';\n    igEl.textContent=r10(0.5*In)+' A (0.5\u00d7In) \u00b7 delay ~0.2 s';\n  }\n  [ib,iz,isc,down].forEach(function(el){el.addEventListener('input',calc);el.addEventListener('change',calc);});\n  $('jt-copy').addEventListener('click',function(){var b=$('jt-copy');var txt='Feeder Ib: '+ib.value+' A, Iz: '+iz.value+' A, Isc: '+isc.value+' kA\\nACB frame In: '+frameEl.textContent+'\\nL - Ir: '+irEl.textContent+'\\nS - Isd: '+isdEl.textContent+'\\nI - Ii: '+iiEl.textContent+'\\nG - Ig: '+igEl.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>Circuit protection ACB Frame &amp; LSIG Trip-Setting Worksheet Build preliminary air circuit breaker frame size and Long-time, Short-time, Instantaneous, and Ground-fault (LSIG) setting ranges from the feeder load current, cable capacity, fault level, and the largest downstream device. Starting ranges for a coordination study \u2014 final settings come from the manufacturer&#8217;s curves. Feeder design current [&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-1814","page","type-page","status-publish","hentry"],"blocksy_meta":[],"_links":{"self":[{"href":"https:\/\/jutrion.com\/ko\/wp-json\/wp\/v2\/pages\/1814","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/jutrion.com\/ko\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/jutrion.com\/ko\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/jutrion.com\/ko\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/jutrion.com\/ko\/wp-json\/wp\/v2\/comments?post=1814"}],"version-history":[{"count":1,"href":"https:\/\/jutrion.com\/ko\/wp-json\/wp\/v2\/pages\/1814\/revisions"}],"predecessor-version":[{"id":1815,"href":"https:\/\/jutrion.com\/ko\/wp-json\/wp\/v2\/pages\/1814\/revisions\/1815"}],"up":[{"embeddable":true,"href":"https:\/\/jutrion.com\/ko\/wp-json\/wp\/v2\/pages\/1778"}],"wp:attachment":[{"href":"https:\/\/jutrion.com\/ko\/wp-json\/wp\/v2\/media?parent=1814"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}