{"id":1786,"date":"2026-07-27T10:33:33","date_gmt":"2026-07-27T02:33:33","guid":{"rendered":"https:\/\/jutrion.com\/?page_id=1786"},"modified":"2026-07-27T10:38:03","modified_gmt":"2026-07-27T02:38:03","slug":"pv-dc-ats-calculator","status":"publish","type":"page","link":"https:\/\/jutrion.com\/pl\/tools\/pv-dc-ats-calculator\/","title":{"rendered":"PV \/ Battery DC Transfer Switch Calculator"},"content":{"rendered":"\n<!-- ===== JUTRION PV DC ATS Calculator \u2014 paste into a WordPress \"Custom HTML\" block ===== -->\n<div class=\"jt-calc\">\n  <p class=\"eyebrow\">Solar &amp; DC<\/p>\n  <h1>PV \/ Battery DC Transfer Switch Calculator<\/h1>\n  <p class=\"tool-lede\">Size the DC design current and organise the voltage, pole, and switching requirements for a DC transfer switch between two DC sources \u2014 for example solar and battery, or two battery banks. DC transfer is arc-critical: the switch must make and break at full DC voltage with the correct polarity handling.<\/p>\n\n  <div class=\"jt-card\"><div class=\"jt-grid\">\n    <div class=\"jt-inputs\">\n      <div class=\"jt-field\"><label>Known value<\/label>\n        <div class=\"jt-inline\">\n          <input type=\"number\" id=\"jt-val\" value=\"10\" min=\"0.1\" step=\"0.1\" inputmode=\"decimal\" aria-label=\"Value\">\n          <select id=\"jt-mode\" aria-label=\"Known quantity\"><option value=\"kw\" selected>kW<\/option><option value=\"a\">A<\/option><\/select>\n        <\/div>\n      <\/div>\n      <div class=\"jt-field\"><label for=\"jt-vdc\">System voltage V<sub>dc<\/sub> (V)<\/label><input type=\"number\" id=\"jt-vdc\" value=\"48\" min=\"1\" step=\"1\" inputmode=\"numeric\"><\/div>\n      <div class=\"jt-two\">\n        <div class=\"jt-field\"><label for=\"jt-fac\">Current margin<\/label>\n          <select id=\"jt-fac\"><option value=\"1.25\" selected>1.25 \u00d7<\/option><option value=\"1.4\">1.4 \u00d7<\/option><\/select>\n        <\/div>\n        <div class=\"jt-field\"><label for=\"jt-pol\">Configuration<\/label>\n          <select id=\"jt-pol\"><option value=\"2\" selected>2-pole (switch both poles)<\/option><option value=\"4\">Bipolar \/ 4-pole<\/option><\/select>\n        <\/div>\n      <\/div>\n      <div class=\"jt-note\"><span>\u24d8<\/span><span>Switching both DC poles isolates the load fully. Enter the maximum continuous DC power or current the transfer switch must carry.<\/span><\/div>\n    <\/div>\n    <div class=\"jt-readout\">\n      <div><div class=\"jt-rl\">DC design current<\/div><div class=\"jt-big\"><span id=\"jt-i\">\u2014<\/span> <span>A<\/span><\/div><\/div>\n      <div class=\"jt-rec row\"><div class=\"k\">Transfer switch I<sub>e<\/sub><\/div><div class=\"v\" id=\"jt-ie\">\u2014<\/div><\/div>\n      <div class=\"jt-rec row\"><div class=\"k\">Rated voltage U<sub>e<\/sub><\/div><div class=\"v\" id=\"jt-ue\">\u2014<\/div><\/div>\n      <div class=\"jt-rec row\"><div class=\"k\">Poles<\/div><div class=\"v\" id=\"jt-poles\">\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>How the rating is built<\/h2>\n    <div class=\"jt-eq\">DC current: I = P \/ V<sub>dc<\/sub>  (or entered directly)\nTransfer switch I<sub>e<\/sub> \u2265 1.25 \u00d7 I\nRated voltage U<sub>e<\/sub> \u2265 system V<sub>dc<\/sub><\/div>\n    <p>The transfer switch carries the full DC load continuously, so the current rating takes the design current with a duty margin. The voltage rating must cover the highest DC bus voltage, and both poles are normally switched so the load is fully isolated during transfer between the two sources.<\/p>\n\n    <h2>Why DC transfer is different<\/h2>\n    <p>Direct current has no natural zero crossing, so a DC transfer switch must quench the arc entirely on its own during the make-break of each transfer. That demands a device with a genuine DC voltage rating, DC-rated contacts, and \u2014 depending on the topology \u2014 correct polarity handling, not an AC changeover switch pressed into DC service. In solar-plus-storage systems the transfer also has to respect source characteristics: a battery can deliver very high fault current, while a PV source is current-limited near its short-circuit value.<\/p>\n    <div class=\"jt-note\"><span>\u26a0<\/span><span><b>Sequence and break-before-make matter.<\/b> Two DC sources must not be paralleled unintentionally during transfer. Use a switch and control scheme designed for DC source transfer, and coordinate it with DC isolation and protection on each source.<\/span><\/div>\n\n    <h2>Frequently asked questions<\/h2>\n    <div class=\"jt-faq\">\n      <details><summary>Can I use an AC ATS on a DC system?<\/summary><p>No, unless it carries an explicit DC voltage and current rating with DC-rated contacts. AC transfer switches rely on the AC current zero to clear the arc, which a DC circuit does not provide.<\/p><\/details>\n      <details><summary>Two poles or four?<\/summary><p>Two poles isolate a single DC bus (positive and negative). A bipolar or 4-pole arrangement suits split or bipolar DC systems, or where each source&#8217;s poles are switched independently. Follow the system topology.<\/p><\/details>\n      <details><summary>How do I handle the different fault levels?<\/summary><p>Size the current and interrupting duty for the worst case \u2014 usually the battery, which can source very high fault current \u2014 while respecting the PV source&#8217;s current-limited behaviour. Coordinate with the DC protection on each source.<\/p><\/details>\n    <\/div>\n\n    <div class=\"jt-cta\">\n      <h2>Select the DC transfer switch<\/h2>\n      <p>Match the current, DC voltage, and pole arrangement to a transfer switch rated for DC source changeover.<\/p>\n      <div class=\"jt-cta-btns\">\n        <a class=\"jt-btn\" href=\"https:\/\/jutrion.com\/ats\/\">Explore JUTRION ATS<\/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\/ats\/\">ATS<\/a> \u00b7 <a href=\"https:\/\/jutrion.com\/dc-mccb\/\">DC MCCB<\/a> \u00b7 <a href=\"https:\/\/jutrion.com\/isolator-switch\/\">Isolator switch<\/a><\/p>\n    <\/div>\n\n    <div class=\"jt-std\"><strong>Standards referenced<\/strong>IEC 60947-6-1 (transfer switching equipment) \u00b7 IEC 60947-3 (DC switching) \u00b7 IEC 62548 \/ IEC 60364-7-712 (PV) \u00b7 manufacturer DC ratings.<\/div>\n    <p class=\"jt-fine\">Planning estimate for guidance only. Final transfer-switch ratings, DC interrupting duty, polarity handling, and control sequence must be confirmed by a qualified person against the system topology and the manufacturer&#8217;s DC data.<\/p>\n  <\/div>\n<\/div>\n\n<script>\n(function(){\n  var $=function(id){return document.getElementById(id);};\n  var val=$('jt-val'),mode=$('jt-mode'),vdc=$('jt-vdc'),fac=$('jt-fac'),pol=$('jt-pol'),\n      iEl=$('jt-i'),ieEl=$('jt-ie'),ueEl=$('jt-ue'),polesEl=$('jt-poles');\n  var LADDER=[16,20,25,32,40,50,63,80,100,125,160,200,250,320,400,500,630,800,1000,1250,1600,2000,2500,3200];\n  function nextIe(x){for(var k=0;k<LADDER.length;k++){if(LADDER[k]>=x)return LADDER[k];}return null;}\n  function calc(){\n    var x=parseFloat(val.value),V=parseFloat(vdc.value),f=parseFloat(fac.value);\n    if(!(x>0&&V>0)){iEl.textContent='\u2014';ieEl.textContent=ueEl.textContent=polesEl.textContent='\u2014';return;}\n    var I=(mode.value==='a')?x:(x*1000\/V);\n    iEl.textContent=I.toFixed(1);\n    var need=f*I,r=nextIe(need);\n    ieEl.textContent=(r?r+' A':'> 3200 A')+' (\u2265 '+need.toFixed(0)+' A)';\n    ueEl.textContent='\u2265 '+V+' V DC';\n    polesEl.textContent=pol.value+'-pole';\n  }\n  [val,mode,vdc,fac,pol].forEach(function(el){el.addEventListener('input',calc);el.addEventListener('change',calc);});\n  $('jt-copy').addEventListener('click',function(){var b=$('jt-copy');var txt='DC source transfer: '+val.value+' '+mode.value.toUpperCase()+' @ '+vdc.value+' V\\nDesign current: '+iEl.textContent+' A\\nSwitch Ie: '+ieEl.textContent+'\\nRated voltage Ue: '+ueEl.textContent+'\\nPoles: '+polesEl.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>Solar &amp; DC PV \/ Battery DC Transfer Switch Calculator Size the DC design current and organise the voltage, pole, and switching requirements for a DC transfer switch between two DC sources \u2014 for example solar and battery, or two battery banks. DC transfer is arc-critical: the switch must make and break at full DC [&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-1786","page","type-page","status-publish","hentry"],"blocksy_meta":[],"_links":{"self":[{"href":"https:\/\/jutrion.com\/pl\/wp-json\/wp\/v2\/pages\/1786","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/jutrion.com\/pl\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/jutrion.com\/pl\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/jutrion.com\/pl\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/jutrion.com\/pl\/wp-json\/wp\/v2\/comments?post=1786"}],"version-history":[{"count":1,"href":"https:\/\/jutrion.com\/pl\/wp-json\/wp\/v2\/pages\/1786\/revisions"}],"predecessor-version":[{"id":1787,"href":"https:\/\/jutrion.com\/pl\/wp-json\/wp\/v2\/pages\/1786\/revisions\/1787"}],"up":[{"embeddable":true,"href":"https:\/\/jutrion.com\/pl\/wp-json\/wp\/v2\/pages\/1778"}],"wp:attachment":[{"href":"https:\/\/jutrion.com\/pl\/wp-json\/wp\/v2\/media?parent=1786"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}