{"id":5539,"date":"2022-03-29T16:57:00","date_gmt":"2022-03-29T14:57:00","guid":{"rendered":"https:\/\/www.idro-elettrica.it\/esperto-risponde\/what-type-of-differential-switch-should-be-used-when-protecting-an-inverter-controlled-pressurization-unit\/"},"modified":"2026-07-01T09:47:37","modified_gmt":"2026-07-01T07:47:37","slug":"what-type-of-differential-switch-should-be-used-when-protecting-an-inverter-controlled-pressurization-unit","status":"publish","type":"esperto-risponde","link":"https:\/\/www.idro-elettrica.it\/en\/esperto-risponde\/what-type-of-differential-switch-should-be-used-when-protecting-an-inverter-controlled-pressurization-unit\/","title":{"rendered":"Type B Ground-Fault Circuit Interrupter and Inverter: A Safe Choice"},"content":{"rendered":"\n<p class=\"wp-block-paragraph\"><em>A Type B ground-fault circuit interrupter<\/em> is the recommended choice when you need to protect an inverter-controlled pressurization unit, because ground fault currents can also be continuous.<\/p>\n\n<p class=\"wp-block-paragraph\">In this response, we clarify the different classes (AC, A, and B), fault current waveforms, and selection criteria, with one key point: <strong>sensitivity and response time cannot be \u201cguessed<\/strong>, <strong>\u201d<\/strong> but must be defined during the design phase based on the system\u2019s configuration.<br\/><\/p>\n\n<div class=\"wp-block-rank-math-toc-block\" id=\"rank-math-toc\"><h2>Table of Contents<\/h2><nav><ul><li class=\"\"><a href=\"#cose-un-interruttore-differenziale-e-cosa-vede\">What is a ground-fault circuit interrupter, and what does it \u201cdetect\u201d?<\/a><\/li><li class=\"\"><a href=\"#perche-linverter-cambia-il-tipo-di-corrente-di-dispersione\">Why does the inverter change the type of ground fault current?<\/a><\/li><li class=\"\"><a href=\"#classificazione-differenziale-tipo-ac-a-e-b\">Classification: AC, A, and B differential types<\/a><\/li><li class=\"\"><a href=\"#interruttore-differenziale-tipo-b-con-inverter-quando-e-perche\">Type B Ground-Fault Circuit Interrupter with Inverter: When and Why<\/a><\/li><li class=\"\"><a href=\"#sensibilita-e-tempi-di-intervento-cosa-deve-stabilire-il-progettista\">Sensitivity and Response Times: What the Designer Must Determine<\/a><\/li><li class=\"\"><a href=\"#errori-tipici-da-evitare-nella-scelta-del-differenziale\">Common Mistakes to Avoid When Choosing a Differential<\/a><\/li><li class=\"\"><a href=\"#conclusione\">Conclusion<\/a><\/li><\/ul><\/nav><\/div>\n\n<h2 id=\"cose-un-interruttore-differenziale-e-cosa-vede\" class=\"wp-block-heading\">What is a ground-fault circuit interrupter, and what does it \u201cdetect\u201d?<\/h2>\n\n<p class=\"wp-block-paragraph\">A ground-fault circuit interrupter (GFCI) is a safety device that <strong>automatically cuts off the power supply<\/strong> when it detects a <strong>ground fault current exceeding a certain threshold<\/strong>.<\/p>\n\n<p class=\"wp-block-paragraph\">There are various types of differentials on the market, which are classified according to different parameters. Among the most important is the <strong>\u201cclass\u201d<\/strong> (or type), which is related to the differential\u2019s ability to <strong>detect certain<\/strong> current <strong>waveforms<\/strong>. <\/p>\n\n<h2 id=\"perche-linverter-cambia-il-tipo-di-corrente-di-dispersione\" class=\"wp-block-heading\">Why does the inverter change the type of ground fault current?<\/h2>\n\n<p class=\"wp-block-paragraph\">The now widespread use of electronic devices in both civilian and industrial settings can result in leakage currents to ground with <strong>non-sinusoidal<\/strong> components in the event of <strong>an insulation failure<\/strong>.<\/p>\n\n<p class=\"wp-block-paragraph\">In practice, in addition to the case of sinusoidal current, leakage currents may occur:<\/p>\n\n<ul class=\"wp-block-list\">\n<li><strong>unidirectional<\/strong>,<\/li>\n\n\n\n<li><strong>buttons<\/strong>,<\/li>\n\n\n\n<li><strong>continue<\/strong>.<\/li>\n<\/ul>\n\n<p class=\"wp-block-paragraph\">In the case of an <strong>inverter-controlled pressurization unit<\/strong>, this is precisely the condition associated with a <strong>continuous leakage current<\/strong>. And this is where the choice of residual current device (RCD) becomes critical. <\/p>\n\n<h2 id=\"classificazione-differenziale-tipo-ac-a-e-b\" class=\"wp-block-heading\">Classification: AC, A, and B differential types<\/h2>\n\n<p class=\"wp-block-paragraph\">With regard to the leakage currents to which the residual current device is sensitive, the rules classify them into <strong>three types: AC, A, and B<\/strong>.<\/p>\n\n<p class=\"wp-block-paragraph\">The key point is not \u201cwhich one is absolutely better,\u201d but <strong>which one is consistent with the waveform<\/strong> of the possible ground fault currents that the system can generate.<\/p>\n\n<p class=\"wp-block-paragraph\">When electronic equipment (such as inverter drives) is present, this check becomes even more important, because leakage currents may deviate from the \u201ctraditional\u201d sinusoidal behavior.<\/p>\n\n<h2 id=\"interruttore-differenziale-tipo-b-con-inverter-quando-e-perche\" class=\"wp-block-heading\">Type B Ground-Fault Circuit Interrupter with Inverter: When and Why<\/h2>\n\n<p class=\"wp-block-paragraph\">If the pressurization unit is controlled by an inverter and a <strong>continuous leakage current<\/strong> condition is present, a conventional residual current device <strong>will not function properly<\/strong>.<\/p>\n\n<p class=\"wp-block-paragraph\"><strong>Class B residual current devices<\/strong>, manufactured in accordance with <strong>IEC\/EN 62423<\/strong>, are capable of:<\/p>\n\n<ul class=\"wp-block-list\">\n<li>detect all waveforms normally detectable by Class <strong>AC<\/strong> and <strong>A<\/strong> differential meters;<\/li>\n\n\n\n<li>In addition, it can also detect <strong>continuous<\/strong> ground fault currents.<\/li>\n<\/ul>\n\n<p class=\"wp-block-paragraph\">For this reason, their use is <strong>highly recommended<\/strong> in presence of <strong>inverter drives<\/strong>\u2014that is, devices capable of generating continuous fault currents. In other words: if the inverter can cause a \u201ccontinuous fault,\u201d you need a residual current device that <strong>is sensitive to that type of fault as well<\/strong>. <\/p>\n\n<h2 id=\"sensibilita-e-tempi-di-intervento-cosa-deve-stabilire-il-progettista\" class=\"wp-block-heading\">Sensitivity and Response Times: What the Designer Must Determine<\/h2>\n\n<p class=\"wp-block-paragraph\">Even once the correct type has been identified (for example, <em>a Type B ground-fault circuit interrupter<\/em>), there are still two key aspects that should not be treated as \u201cstandard sizes\u201d that are always valid:<\/p>\n\n<ul class=\"wp-block-list\">\n<li><strong>Sensitivity<\/strong> (nominal differential operating current)<\/li>\n\n\n\n<li><strong>Response time<\/strong><\/li>\n<\/ul>\n\n<p class=\"wp-block-paragraph\">These parameters <strong>must be calculated by the electrical designer<\/strong> based on the <strong>specific configuration of the system<\/strong>. This is an essential step because it is the actual configuration\u2014not a general concept of the system\u2014that determines which combination of sensitivity and response times is consistent with the required protection. <\/p>\n\n<h2 id=\"errori-tipici-da-evitare-nella-scelta-del-differenziale\" class=\"wp-block-heading\">Common Mistakes to Avoid When Choosing a Differential<\/h2>\n\n<p class=\"wp-block-paragraph\">When protecting an inverter-controlled pressurization unit, some common mistakes stem from underestimating the role of leakage current waveforms.<\/p>\n\n<p class=\"wp-block-paragraph\">In particular, be careful not to:<\/p>\n\n<ul class=\"wp-block-list\">\n<li>choosing a \u201ctraditional\u201d residual current device <strong>without verifying<\/strong> whether it is suitable for use in the presence of <strong>continuous<\/strong> ground faults;<\/li>\n\n\n\n<li>confusing the \u201cclass\u201d (AC, A, B) with a simple preference for a brand or model, while ignoring the <strong>ability to detect<\/strong> waveforms;<\/li>\n\n\n\n<li>determine <strong>sensitivity and timing<\/strong> without a calculation based on the system configuration (a decision that is up to the electrical designer).<\/li>\n<\/ul>\n\n<h2 id=\"conclusione\" class=\"wp-block-heading\">Conclusion<\/h2>\n\n<p class=\"wp-block-paragraph\">For an inverter-controlled pressurization unit, the potential presence of <strong>continuous leakage currents<\/strong> makes the selection of the residual current device a matter of technical precision:<strong>a Type B residual current device<\/strong> (IEC\/EN 62423) is <strong>highly recommended<\/strong> because it detects continuous earth fault currents in addition to those normally detected by AC and Type A devices.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Type B residual current device (RCD): This is the recommended choice when a pressurization unit is controlled by an inverter. In the presence of continuous ground faults, a traditional RCD may not be suitable. The sensitivity and response times must be determined by the electrical designer based on the specific system.  <\/p>\n","protected":false},"featured_media":5540,"parent":0,"template":"","meta":{"_acf_changed":false,"_angie_page":false,"footnotes":"","_members_access_role":[],"_members_access_error":""},"tags":[1284,1282,1287,1286,1274,1285,621,1283],"class_list":["post-5539","esperto-risponde","type-esperto-risponde","status-publish","has-post-thumbnail","hentry","tag-electrical-protection","tag-ground-fault-circuit-interrupter","tag-iec-en-62423","tag-insulation-failure","tag-inverter","tag-leakage-currents","tag-pressurization-unit","tag-type-b-differential"],"acf":[],"_links":{"self":[{"href":"https:\/\/www.idro-elettrica.it\/en\/wp-json\/wp\/v2\/esperto-risponde\/5539","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.idro-elettrica.it\/en\/wp-json\/wp\/v2\/esperto-risponde"}],"about":[{"href":"https:\/\/www.idro-elettrica.it\/en\/wp-json\/wp\/v2\/types\/esperto-risponde"}],"version-history":[{"count":0,"href":"https:\/\/www.idro-elettrica.it\/en\/wp-json\/wp\/v2\/esperto-risponde\/5539\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.idro-elettrica.it\/en\/wp-json\/wp\/v2\/media\/5540"}],"wp:attachment":[{"href":"https:\/\/www.idro-elettrica.it\/en\/wp-json\/wp\/v2\/media?parent=5539"}],"wp:term":[{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.idro-elettrica.it\/en\/wp-json\/wp\/v2\/tags?post=5539"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}