{"id":20937,"date":"2026-11-06T10:14:48","date_gmt":"2026-11-06T02:14:48","guid":{"rendered":"https:\/\/www.wehopower.com\/news\/external-output-capacitor-fault-energy-lrs50\/"},"modified":"2026-11-06T10:14:48","modified_gmt":"2026-11-06T02:14:48","slug":"external-output-capacitor-fault-energy-lrs50","status":"publish","type":"news","link":"https:\/\/www.wehopower.com\/ar\/news\/external-output-capacitor-fault-energy-lrs50\/","title":{"rendered":"External Output Capacitors: Review Fault Energy Beyond the Power Supply Current Limit"},"content":{"rendered":"<figure class=\"hero\"><a href=\"https:\/\/www.wehopower.com\/ar\/product\/lrs-series-50w-ac-to-dc-single-output-switching-power-supply\/\"><img decoding=\"async\" src=\"https:\/\/www.wehopower.com\/wp-content\/uploads\/2026\/11\/hero-21.webp\" alt=\"External Output Capacitors: Review Fault Energy Beyond the Power Supply Current Limit  title=\" fetchpriority=\"high\" external output capacitors: review fault energy beyond the power supply current limit title=\"\"><\/a><figcaption>AI-assisted application illustration with original LRS-50-24 artwork. The adjacent capacitor assembly is generic; concealed fixing, terminal contacts and the complete protected capacitor circuit are not verified. No customer installation or test is represented.<\/figcaption><a class=\"original-link\" href=\"https:\/\/www.wehopower.com\/wp-content\/uploads\/2026\/11\/original-14.jpg\">View original product image<\/a><\/figure>\n<p><strong>A power supply current limit does not, by itself, limit the first discharge from a capacitor already charged across its output.<\/strong> Before adding bulk capacitance to a 24 V branch, review where that stored energy can flow during a wiring or receiver fault. Starting successfully and meeting a voltage-dip target are separate acceptance questions.<\/p>\n<p>This article is for an OEM designer reviewing an external capacitor added downstream of a WEHO LRS-50-24. It provides an energy and fault-path record. It does not specify an approved capacitance, fuse, resistor or protection device for this supply.<\/p>\n<nav class=\"toc\" aria-label=\"On this page\">\n<ol>\n<li><a href=\"#separate-the-sources\">Draw the converter and capacitor as separate energy contributors<\/a><\/li>\n<li><a href=\"#calculate-energy\">Calculate stored energy before selecting a protective solution<\/a><\/li>\n<li><a href=\"#find-the-unprotected-path\">Look for a discharge path that bypasses the intended protection<\/a><\/li>\n<li><a href=\"#test-distinct-events\">Keep startup, load support and fault response as distinct checks<\/a><\/li>\n<li><a href=\"#release-the-change\">Release the capacitor as an assembly change<\/a><\/li>\n<\/ol>\n<\/nav>\n<section id=\"separate-the-sources\">\n<div id=\"ez-toc-container\" class=\"ez-toc-v2_0_86 counter-hierarchy ez-toc-counter ez-toc-grey ez-toc-container-direction\">\n<div class=\"ez-toc-title-container\">\n<p class=\"ez-toc-title\" style=\"cursor:inherit\">\u062c\u062f\u0648\u0644 \u0627\u0644\u0645\u062d\u062a\u0648\u064a\u0627\u062a<\/p>\n<span class=\"ez-toc-title-toggle\"><a href=\"#\" class=\"ez-toc-pull-right ez-toc-btn ez-toc-btn-xs ez-toc-btn-default ez-toc-toggle\" aria-label=\"Toggle Table of Content\"><span class=\"ez-toc-js-icon-con\"><span class=\"\"><span class=\"eztoc-hide\" style=\"display:none;\">\u062a\u0628\u062f\u064a\u0644<\/span><span class=\"ez-toc-icon-toggle-span\"><svg style=\"fill: #999;color:#999\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" class=\"list-377408\" width=\"20px\" height=\"20px\" viewbox=\"0 0 24 24\" fill=\"none\"><path d=\"M6 6H4v2h2V6zm14 0H8v2h12V6zM4 11h2v2H4v-2zm16 0H8v2h12v-2zM4 16h2v2H4v-2zm16 0H8v2h12v-2z\" fill=\"currentColor\"><\/path><\/svg><svg style=\"fill: #999;color:#999\" class=\"arrow-unsorted-368013\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"10px\" height=\"10px\" viewbox=\"0 0 24 24\" version=\"1.2\" baseprofile=\"tiny\"><path d=\"M18.2 9.3l-6.2-6.3-6.2 6.3c-.2.2-.3.4-.3.7s.1.5.3.7c.2.2.4.3.7.3h11c.3 0 .5-.1.7-.3.2-.2.3-.5.3-.7s-.1-.5-.3-.7zM5.8 14.7l6.2 6.3 6.2-6.3c.2-.2.3-.5.3-.7s-.1-.5-.3-.7c-.2-.2-.4-.3-.7-.3h-11c-.3 0-.5.1-.7.3-.2.2-.3.5-.3.7s.1.5.3.7z\"\/><\/svg><\/span><\/span><\/span><\/a><\/span><\/div>\n<nav><ul class='ez-toc-list ez-toc-list-level-1' ><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-1\" href=\"https:\/\/www.wehopower.com\/ar\/news\/external-output-capacitor-fault-energy-lrs50\/#Draw_the_converter_and_capacitor_as_separate_energy_contributors\" >Draw the converter and capacitor as separate energy contributors<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-2\" href=\"https:\/\/www.wehopower.com\/ar\/news\/external-output-capacitor-fault-energy-lrs50\/#Calculate_stored_energy_before_selecting_a_protective_solution\" >Calculate stored energy before selecting a protective solution<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-3\" href=\"https:\/\/www.wehopower.com\/ar\/news\/external-output-capacitor-fault-energy-lrs50\/#Look_for_a_discharge_path_that_bypasses_the_intended_protection\" >Look for a discharge path that bypasses the intended protection<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-4\" href=\"https:\/\/www.wehopower.com\/ar\/news\/external-output-capacitor-fault-energy-lrs50\/#Keep_startup_load_support_and_fault_response_as_distinct_checks\" >Keep startup, load support and fault response as distinct checks<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-5\" href=\"https:\/\/www.wehopower.com\/ar\/news\/external-output-capacitor-fault-energy-lrs50\/#Release_the_capacitor_as_an_assembly_change\" >Release the capacitor as an assembly change<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-6\" href=\"https:\/\/www.wehopower.com\/ar\/news\/external-output-capacitor-fault-energy-lrs50\/#External_capacitor_change_record\" >External capacitor change record<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-7\" href=\"https:\/\/www.wehopower.com\/ar\/news\/external-output-capacitor-fault-energy-lrs50\/#Sources_and_further_reading\" >Sources and further reading<\/a><\/li><\/ul><\/nav><\/div>\n<h2><span class=\"ez-toc-section\" id=\"Draw_the_converter_and_capacitor_as_separate_energy_contributors\"><\/span>Draw the converter and capacitor as separate energy contributors<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p>The LRS-50-24 manufacturer photograph is marked 24 V and 2.1 A. That output description is useful for identifying the pictured variant, but it is not a rating for every transient through an attached capacitor. During a fault, current may arrive both from the converter and from stored energy in the external branch.<\/p>\n<p>Draw the external capacitor at its physical location, not merely next to the supply symbol. Trace its positive connection, return, receiver terminals, distribution protection and service connector. A protective device upstream of a capacitor can interrupt the supply path while the capacitor still has a local path to the fault.<\/p>\n<figure id=\"fig-original\" class=\"product-original\"><a href=\"https:\/\/www.wehopower.com\/ar\/product\/lrs-series-50w-ac-to-dc-single-output-switching-power-supply\/\"><img decoding=\"async\" src=\"https:\/\/www.wehopower.com\/wp-content\/uploads\/2026\/11\/original-14.jpg\" alt=\"External Output Capacitors: Review Fault Energy Beyond the Power Supply Current Limit  title=\" loading=\"lazy\" external output capacitors: review fault energy beyond the power supply current limit title=\"\"><\/a><figcaption>Manufacturer image showing the WEHO LRS-50-24; the photograph identifies the pictured unit and does not establish equipment-level suitability.<\/figcaption><a class=\"original-link\" href=\"https:\/\/www.wehopower.com\/wp-content\/uploads\/2026\/11\/original-14.jpg\">View original image<\/a><\/figure>\n<\/section>\n<section id=\"calculate-energy\">\n<h2><span class=\"ez-toc-section\" id=\"Calculate_stored_energy_before_selecting_a_protective_solution\"><\/span>Calculate stored energy before selecting a protective solution<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p>For an ideal capacitor, <strong>E = \u00bdCV\u00b2<\/strong>, with capacitance in farads, voltage in volts and energy in joules. The <a href=\"https:\/\/www.us.lambda.tdk.com\/resources\/blogs\/20200415.html\" target=\"_blank\" rel=\"noopener\">TDK-Lambda hold-up explanation<\/a> uses this energy relationship and also identifies startup problems introduced by extra output capacitance. Its product examples do not establish a WEHO limit.<\/p>\n<p>As a hypothetical comparison at 24 V, 4,700 \u00b5F stores 0.5 \u00d7 0.0047 \u00d7 24\u00b2 = <strong>1.3536 J<\/strong>; 47,000 \u00b5F stores <strong>13.536 J<\/strong>. Increasing capacitance tenfold increases this ideal energy tenfold. Neither result predicts a peak fault current or proves that a contact can interrupt it.<\/p>\n<p>Use the actual maximum permitted branch voltage and the capacitance tolerance for a worst-case review. Energy varies with the square of voltage. ESR, ESL, conductor impedance, component failure behavior and the fault location shape the discharge. They must not be replaced with the converter current rating in the calculation.<\/p>\n<figure id=\"fig-diagram\" class=\"diagram\"><img decoding=\"async\" class=\"technical-desktop\" src=\"https:\/\/www.wehopower.com\/wp-content\/uploads\/2026\/11\/diagram-21.svg\" alt=\"External Output Capacitors: Review Fault Energy Beyond the Power Supply Current Limit  title=\" loading=\"lazy\" external output capacitors: review fault energy beyond the power supply current limit title=\"\"><img decoding=\"async\" class=\"technical-mobile\" src=\"https:\/\/www.wehopower.com\/wp-content\/uploads\/2026\/11\/diagram-mobile-21.svg\" alt=\"External Output Capacitors: Review Fault Energy Beyond the Power Supply Current Limit  title=\" loading=\"lazy\" external output capacitors: review fault energy beyond the power supply current limit title=\"\"><figcaption>Functional fault-path review; no component or protective-device rating is assigned.<\/figcaption><a class=\"original-link\" href=\"https:\/\/www.wehopower.com\/wp-content\/uploads\/2026\/11\/diagram-21.svg\">Open full-size technical illustration<\/a><\/figure>\n<\/section>\n<section id=\"find-the-unprotected-path\">\n<h2><span class=\"ez-toc-section\" id=\"Look_for_a_discharge_path_that_bypasses_the_intended_protection\"><\/span>Look for a discharge path that bypasses the intended protection<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<div class=\"table-scroll\">\n<table>\n<thead>\n<tr>\n<th scope=\"col\">Location to review<\/th>\n<th scope=\"col\">Question<\/th>\n<th scope=\"col\">Record needed<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>Capacitor near receiver<\/td>\n<td>Is a short downstream of the capacitor also downstream of the fuse?<\/td>\n<td>Physical circuit and protective-device position<\/td>\n<\/tr>\n<tr>\n<td>Service connector<\/td>\n<td>Can the capacitor remain on either half after separation?<\/td>\n<td>Voltage and discharge-state record<\/td>\n<\/tr>\n<tr>\n<td>Shared return<\/td>\n<td>Can another branch complete a return path?<\/td>\n<td>Complete return and bonding diagram<\/td>\n<\/tr>\n<tr>\n<td>Receiver input<\/td>\n<td>Is local stored energy covered by the receiver fault analysis?<\/td>\n<td>Receiver limits and assembly assessment<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<p>Do not move a fuse or add a discharge component from this table alone. Interrupting capability, coordination, component ratings, normal current and the relevant equipment requirements must be assessed together. The purpose of the path sketch is to expose a missing question before hardware is committed.<\/p>\n<\/section>\n<section id=\"test-distinct-events\">\n<h2><span class=\"ez-toc-section\" id=\"Keep_startup_load_support_and_fault_response_as_distinct_checks\"><\/span>Keep startup, load support and fault response as distinct checks<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p>First confirm the supply can start with the proposed capacitance under its stated input, load and environmental conditions. Then verify receiver voltage during the intended load event. Separately assess fault energy and isolation. Passing one check cannot substitute for the other two.<\/p>\n<p>TDK-Lambda describes how an initially discharged capacitor can drive an ordinary constant-voltage supply into overcurrent protection. That is a reason to obtain the LRS-50 revision-specific permitted load conditions, rather than assume the added capacitor is harmless because its steady-state current is small.<\/p>\n<p>Do not create uncontrolled shorts to obtain a dramatic current trace. A qualified test plan should state the approved fault simulation, protected test arrangement, instrumentation limits and stopping conditions. Retain the actual circuit revision and measured traces if such testing is authorized.<\/p>\n<\/section>\n<section id=\"release-the-change\">\n<h2><span class=\"ez-toc-section\" id=\"Release_the_capacitor_as_an_assembly_change\"><\/span>Release the capacitor as an assembly change<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p>Record why the capacitor was added, its approved part and tolerance, the maximum operating voltage, the actual energy path and the remaining evidence. Reopen the review when the capacitor moves to another board or a field cable is shortened: the stored energy may be unchanged while the discharge path changes.<\/p>\n<p>The useful release output is a signed circuit and evidence record, not a statement that a larger capacitor made the power supply stronger. If the fault-path assessment is incomplete, keep that assembly change out of the released BOM while continuing the independent supply and load checks.<\/p>\n<\/section>\n<section class=\"cta\">\n<p>For the proposed <a href=\"https:\/\/www.wehopower.com\/ar\/product\/lrs-series-50w-ac-to-dc-single-output-switching-power-supply\/\">LRS-50-24 assembly<\/a>, send the external-capacitance range, maximum permitted voltage, discharge-path sketch and protection record. Ask WEHO for the offered revision\u2019s output-capacitance and startup conditions; qualify the downstream fault path separately with the equipment designer.<\/p>\n<\/section>\n<section id=\"worksheet\" class=\"sheet\">\n<h2><span class=\"ez-toc-section\" id=\"External_capacitor_change_record\"><\/span>External capacitor change record<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<div class=\"sheet-row\"><label>Supply revision<input aria-label=\"Supply revision\"><\/label><label>Capacitor part and tolerance<input aria-label=\"Capacitor part and tolerance\"><\/label><label>Maximum branch voltage<input aria-label=\"Maximum branch voltage\"><\/label><label>Circuit revision<input aria-label=\"Circuit revision\"><\/label><label>Review owner<input aria-label=\"Review owner\"><\/label><\/div>\n<div class=\"table-scroll\">\n<table>\n<thead>\n<tr>\n<th scope=\"col\">Event<\/th>\n<th scope=\"col\">Energy or operating demand<\/th>\n<th scope=\"col\">Path and protection<\/th>\n<th scope=\"col\">Evidence<\/th>\n<th scope=\"col\">Decision<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td contenteditable=\"true\" aria-label=\"Worksheet cell\"><\/td>\n<td contenteditable=\"true\" aria-label=\"Worksheet cell\"><\/td>\n<td contenteditable=\"true\" aria-label=\"Worksheet cell\"><\/td>\n<td contenteditable=\"true\" aria-label=\"Worksheet cell\"><\/td>\n<td contenteditable=\"true\" aria-label=\"Worksheet cell\"><\/td>\n<\/tr>\n<tr>\n<td contenteditable=\"true\" aria-label=\"Worksheet cell\"><\/td>\n<td contenteditable=\"true\" aria-label=\"Worksheet cell\"><\/td>\n<td contenteditable=\"true\" aria-label=\"Worksheet cell\"><\/td>\n<td contenteditable=\"true\" aria-label=\"Worksheet cell\"><\/td>\n<td contenteditable=\"true\" aria-label=\"Worksheet cell\"><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<p>Blank project worksheet. Enter verified project data; example calculations above are not measurements.<\/p>\n<\/section>\n<section class=\"source-list\">\n<h2><span class=\"ez-toc-section\" id=\"Sources_and_further_reading\"><\/span>Sources and further reading<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<ol>\n<li><a href=\"https:\/\/www.wehopower.com\/ar\/product\/lrs-series-50w-ac-to-dc-single-output-switching-power-supply\/\">WEHO LRS-50 product information<\/a><\/li>\n<li><a href=\"https:\/\/www.wehopower.com\/wp-content\/uploads\/2025\/07\/LRS-50-a07.pdf\">WEHO LRS-50 specification<\/a><\/li>\n<li><a href=\"https:\/\/www.us.lambda.tdk.com\/resources\/blogs\/20200415.html\" target=\"_blank\" rel=\"noopener\">TDK-Lambda: How can I increase a power supply\u2019s hold-up time?<\/a><\/li>\n<\/ol>\n<\/section>","protected":false},"excerpt":{"rendered":"<p>Calculate stored energy, map the discharge path and separate converter current limiting from downstream capacitor discharge when reviewing a 24 V supply.<\/p>","protected":false},"author":2,"featured_media":20921,"parent":0,"menu_order":8,"comment_status":"","ping_status":"","template":"","format":"standard","meta":{"_acf_changed":false,"_joinchat":[],"footnotes":""},"news_category":[284],"class_list":["post-20937","news","type-news","status-publish","format-standard","has-post-thumbnail","hentry","news_category-product-articles","entry"],"acf":[],"post_mailing_queue_ids":[],"_links":{"self":[{"href":"https:\/\/www.wehopower.com\/ar\/wp-json\/wp\/v2\/news\/20937","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.wehopower.com\/ar\/wp-json\/wp\/v2\/news"}],"about":[{"href":"https:\/\/www.wehopower.com\/ar\/wp-json\/wp\/v2\/types\/news"}],"author":[{"embeddable":true,"href":"https:\/\/www.wehopower.com\/ar\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.wehopower.com\/ar\/wp-json\/wp\/v2\/comments?post=20937"}],"version-history":[{"count":0,"href":"https:\/\/www.wehopower.com\/ar\/wp-json\/wp\/v2\/news\/20937\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.wehopower.com\/ar\/wp-json\/wp\/v2\/media\/20921"}],"wp:attachment":[{"href":"https:\/\/www.wehopower.com\/ar\/wp-json\/wp\/v2\/media?parent=20937"}],"wp:term":[{"taxonomy":"news_category","embeddable":true,"href":"https:\/\/www.wehopower.com\/ar\/wp-json\/wp\/v2\/news_category?post=20937"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}