{"id":20268,"date":"2025-11-19T00:42:19","date_gmt":"2025-11-18T16:42:19","guid":{"rendered":"https:\/\/viox.com\/?p=20268"},"modified":"2025-11-19T00:42:21","modified_gmt":"2025-11-18T16:42:21","slug":"circuit-breaker-ratings-icu-ics-icw-icm","status":"publish","type":"post","link":"https:\/\/test.viox.com\/cs\/circuit-breaker-ratings-icu-ics-icw-icm\/","title":{"rendered":"Vysv\u011btlen\u00ed jmenovit\u00fdch hodnot jisti\u010d\u016f: Icu, Ics, Icw, Icm"},"content":{"rendered":"<div class=\"product-intro\">\n<p>Technick\u00fd list vypadal perfektn\u011b. Jmenovit\u00e1 zkratov\u00e1 vyp\u00ednac\u00ed schopnost Icu 50 kA, co\u017e je v\u00fdrazn\u011b nad vypo\u010dten\u00fdm zkratov\u00fdm proudem 38 kA. Objedn\u00e1vku jste schv\u00e1lili, jisti\u010d byl dod\u00e1n a instalace prob\u011bhla hladce.<\/p>\n<p>O t\u0159i m\u011bs\u00edce pozd\u011bji do\u0161lo ke zkratu na hlavn\u00ed rozvodn\u00e9 sb\u011brnici. Jisti\u010d odstranil poruchu v milisekund\u00e1ch \u2013 p\u0159esn\u011b podle n\u00e1vrhu. Kdy\u017e ale v\u00e1\u0161 t\u00fdm znovu zapnul nap\u00e1jen\u00ed a spustil diagnostiku, kontaktn\u00ed odpor jisti\u010de se ztrojn\u00e1sobil. Obloukov\u00e1 komora vykazovala tepeln\u00e9 po\u0161kozen\u00ed. To, co bylo dimenzov\u00e1no na des\u00edtky let provozu, bylo po jedin\u00e9m p\u0159eru\u0161en\u00ed poruchy na hran\u011b pou\u017eitelnosti. V\u00fdroba byla obnovena, ale objednali jste n\u00e1hradn\u00ed d\u00edl a podali zpr\u00e1vu o poru\u0161e.<\/p>\n<p>Hlavn\u00ed p\u0159\u00ed\u010dina? Zkontrolovali jste Icu \u2013 schopnost jisti\u010de jednou p\u0159eru\u0161it maxim\u00e1ln\u00ed zkratov\u00fd proud. Nezkontrolovali jste Ics \u2013 provozn\u00ed vyp\u00ednac\u00ed schopnost, kter\u00e1 ur\u010duje, zda jisti\u010d z\u016fstane spolehliv\u00fd i po proveden\u00ed sv\u00e9 pr\u00e1ce. V\u00e1\u0161 jisti\u010d s hodnotou 50 kA m\u011bl jmenovitou hodnotu Ics pouze 25 kA (50 % Icu). Zkrat 38 kA byl hluboko v r\u00e1mci Icu, ale daleko za hranic\u00ed Ics. Jisti\u010d fungoval jako <strong>\u201cHrdina na jedno pou\u017eit\u00ed\u201d<\/strong>\u2013 zachr\u00e1nil v\u00e1\u0161 syst\u00e9m, ale u\u017e to nemohl ud\u011blat znovu.<\/p>\n<p>Toto je <strong>\u201cSlep\u00e1 skvrna Ics,\u201d<\/strong> a je to chyba specifikace jisti\u010de v pr\u016fmyslov\u00fdch instalac\u00edch.<\/p>\n<hr \/>\n<h2>\u010cty\u0159i jmenovit\u00e9 hodnoty: Co v\u00e1m v\u00e1\u0161 datov\u00fd list ne\u0159\u00edk\u00e1<\/h2>\n<p>Otev\u0159ete si jak\u00fdkoli datov\u00fd list jisti\u010de \u2013<a href=\"https:\/\/test.viox.com\/cs\/mccb\/\">MCCB<\/a>, ACB, nez\u00e1le\u017e\u00ed na tom \u2013 a najdete \u010dty\u0159i jmenovit\u00e9 hodnoty zkratu uveden\u00e9 s minim\u00e1ln\u00edm kontextem:<\/p>\n<ul>\n<li><strong>Icu<\/strong> (jmenovit\u00e1 mezn\u00ed zkratov\u00e1 vyp\u00ednac\u00ed schopnost)<\/li>\n<li><strong>Ics<\/strong> (jmenovit\u00e1 provozn\u00ed zkratov\u00e1 vyp\u00ednac\u00ed schopnost)<\/li>\n<li><strong>Icw<\/strong> (jmenovit\u00fd kr\u00e1tkodob\u00fd v\u00fddr\u017en\u00fd proud)<\/li>\n<li><strong>Icm<\/strong> (jmenovit\u00e1 zkratov\u00e1 zap\u00ednac\u00ed schopnost)<\/li>\n<\/ul>\n<p>\u010cty\u0159i zkratky. \u010cty\u0159i \u010d\u00edsla, obvykle v kA nebo kA peak. A pokud jste nespecifikovali stovky jisti\u010d\u016f, t\u00e9m\u011b\u0159 \u017e\u00e1dn\u00e1 intuice, kter\u00e9 z nich skute\u010dn\u011b \u0159\u00edd\u00ed spolehlivost ve VA\u0160\u00cd aplikaci.<\/p>\n<p>Zde je to, co v\u00e1m datov\u00fd list ne\u0159\u00edk\u00e1: <strong>Tyto jmenovit\u00e9 hodnoty nejsou rovnocenn\u00e9.<\/strong> Pro motorov\u00fd nap\u00e1jec\u00ed obvod dominuj\u00ed va\u0161\u00ed spolehlivosti Icu a Ics \u2013 Icw se ani nepou\u017eije. Pro hlavn\u00ed p\u0159\u00edvod s \u010dasov\u011b zpo\u017ed\u011bnou selektivitou se Icw st\u00e1v\u00e1 kritick\u00fdm. Pro p\u0159ep\u00edna\u010d, kter\u00fd by se mohl sepnout do st\u00e1vaj\u00edc\u00ed poruchy, je nezbytn\u00e9 ov\u011b\u0159en\u00ed Icm.<\/p>\n<p>Jmenovit\u00e9 hodnoty jsou definov\u00e1ny normou IEC 60947-2:2024 (nejnov\u011bj\u0161\u00ed vyd\u00e1n\u00ed, publikov\u00e1no v z\u00e1\u0159\u00ed 2024) a jsou p\u0159esn\u00e9, testovateln\u00e9 a povinn\u00e9. Ale pochopen\u00ed toho, co znamenaj\u00ed \u2013 a co je d\u016fle\u017eit\u011bj\u0161\u00ed, kdy na ka\u017ed\u00e9 z nich z\u00e1le\u017e\u00ed \u2013 vy\u017eaduje p\u0159eklad jazyka normy do aplika\u010dn\u00ed logiky.<\/p>\n<p>Poj\u010fme dek\u00f3dovat v\u0161echny \u010dty\u0159i, po\u010d\u00ednaje t\u00edm, kter\u00fd si ka\u017ed\u00fd kontroluje, ale \u010dasto mu nerozum\u00ed.<\/p>\n<hr \/>\n<h2>Icu: Hrdina na jedno pou\u017eit\u00ed (mezn\u00ed vyp\u00ednac\u00ed schopnost)<\/h2>\n<p><strong>Icu<\/strong> je maxim\u00e1ln\u00ed p\u0159edpokl\u00e1dan\u00fd zkratov\u00fd proud, kter\u00fd m\u016f\u017ee jisti\u010d p\u0159eru\u0161it p\u0159i sv\u00e9m jmenovit\u00e9m nap\u011bt\u00ed, ani\u017e by byl zni\u010den. Je to kone\u010dn\u00e1 hranice \u2013 nejvy\u0161\u0161\u00ed porucha, kterou m\u016f\u017ee jisti\u010d odstranit a p\u0159esto se fyzicky otev\u0159\u00edt, uhasit oblouk a zabr\u00e1nit katastrof\u00e1ln\u00edmu selh\u00e1n\u00ed.<\/p>\n<p>Ale zde je z\u00e1sadn\u00ed nuance: Icu se testuje podle specifick\u00e9 sekvence IEC: O\u2011t\u2011CO. Jisti\u010d se Otev\u0159e, aby odstranil poruchu, dojde k \u010dasov\u00e9mu zpo\u017ed\u011bn\u00ed (t), pot\u00e9 se Zav\u0159e a okam\u017eit\u011b znovu Otev\u0159e, aby odstranil druhou poruchu na \u00farovni Icu. Pokud jisti\u010d p\u0159e\u017eije \u2013 co\u017e znamen\u00e1, \u017ee \u00fasp\u011b\u0161n\u011b p\u0159eru\u0161\u00ed ob\u011b poruchy bez sva\u0159ov\u00e1n\u00ed kontakt\u016f, v\u00fdbuchu nebo selh\u00e1n\u00ed otev\u0159en\u00ed \u2013 projde testem Icu.<\/p>\n<p>Co test NEov\u011b\u0159uje, je, zda je jisti\u010d pot\u00e9 st\u00e1le v dobr\u00e9m stavu. Po testu Icu m\u016f\u017ee m\u00edt za\u0159\u00edzen\u00ed erozi kontakt\u016f, po\u0161kozen\u00ed obloukov\u00e9 komory nebo mechanick\u00e9 opot\u0159eben\u00ed, kter\u00e9 jej \u010din\u00ed nevhodn\u00fdm pro dal\u0161\u00ed provoz. P\u0159edstavte si Icu jako schopnost jisti\u010de zem\u0159\u00edt hrdinsky \u2013 ochr\u00e1n\u00ed va\u0161i instalaci p\u0159ed nejhor\u0161\u00ed poruchou, i kdy\u017e pot\u00e9 u\u017e toho moc nezvl\u00e1dne.<\/p>\n<p>Proto tomu \u0159\u00edk\u00e1me <strong>\u201cHrdina na jedno pou\u017eit\u00ed.\u201d<\/strong><\/p>\n<h3>Pro\u010d samotn\u00e1 Icu nesta\u010d\u00ed<\/h3>\n<p>V\u011bt\u0161ina in\u017een\u00fdr\u016f v\u00ed, \u017ee je t\u0159eba ov\u011b\u0159it, zda Icu \u2265 p\u0159edpokl\u00e1dan\u00fd zkratov\u00fd proud v m\u00edst\u011b instalace. To je prvn\u00ed krok a je nezbytn\u00fd. Jisti\u010d s nedostate\u010dnou Icu je katastrof\u00e1ln\u00ed selh\u00e1n\u00ed, kter\u00e9 \u010dek\u00e1 na to, a\u017e se stane \u2013 kontakty se mohou sva\u0159it, obloukov\u00e9 komory se mohou protrhnout a to, co by m\u011blo b\u00fdt \u0159\u00edzenou ochranou, se stane nekontrolovanou ud\u00e1lost\u00ed.<\/p>\n<p>Ale Icu v\u00e1m nic ne\u0159\u00edk\u00e1 o spolehlivosti pot\u00e9, co jisti\u010d odvede svou pr\u00e1ci. Bude spr\u00e1vn\u011b fungovat p\u0159i dal\u0161\u00ed poru\u0161e? Bude st\u00e1le spl\u0148ovat sv\u00e9 jmenovit\u00e9 hodnoty tepeln\u00e9 a mechanick\u00e9 odolnosti? To Icu netestuje. Pro tuto jistotu se mus\u00edte pod\u00edvat na dal\u0161\u00ed jmenovitou hodnotu: Ics.<\/p>\n<p>Typick\u00e9 pr\u016fmyslov\u00e9 MCCB a ACB maj\u00ed jmenovit\u00e9 hodnoty Icu v rozmez\u00ed od 10 kA do 150 kA, v z\u00e1vislosti na velikosti r\u00e1mu a aplikaci. Va\u0161\u00edm \u00fakolem je zajistit, aby Icu p\u0159ekro\u010dila maxim\u00e1ln\u00ed p\u0159edpokl\u00e1dan\u00fd zkratov\u00fd proud v m\u00edst\u011b instalace, obvykle s bezpe\u010dnostn\u00ed rezervou 10\u201320 % pro zohledn\u011bn\u00ed zm\u011bn syst\u00e9mu b\u011bhem \u017eivotnosti instalace (p\u0159idan\u00e1 v\u00fdroba, sn\u00ed\u017een\u00e1 impedance atd.).<\/p>\n<p>Ale to je jen vstupn\u00ed po\u017eadavek. Icu v\u00e1s dostane dovnit\u0159. Ics ur\u010duje, zda m\u016f\u017eete z\u016fstat.<\/p>\n<hr \/>\n<h2>Ics: Bojovn\u00edk od pond\u011bl\u00ed do p\u00e1tku (provozn\u00ed vyp\u00ednac\u00ed schopnost)<\/h2>\n<p><strong>Ics<\/strong> je jmenovit\u00e1 provozn\u00ed zkratov\u00e1 vyp\u00ednac\u00ed schopnost \u2013 maxim\u00e1ln\u00ed zkratov\u00fd proud, p\u0159i kter\u00e9m je ov\u011b\u0159eno, \u017ee jisti\u010d z\u016fstane po p\u0159eru\u0161en\u00ed v dobr\u00e9m provozn\u00edm stavu. Toto je jmenovit\u00e1 hodnota, kter\u00e1 ur\u010duje, zda bude v\u00e1\u0161 jisti\u010d po odstran\u011bn\u00ed poruchy st\u00e1le spolehliv\u011b fungovat.<\/p>\n<p>Ics se testuje podle n\u00e1ro\u010dn\u011bj\u0161\u00ed sekvence ne\u017e Icu: O\u2011CO\u2011CO. Jisti\u010d se Otev\u0159e, aby odstranil poruchu na \u00farovni Ics, Zav\u0159e a okam\u017eit\u011b znovu Otev\u0159e (CO), pot\u00e9 cyklus opakuje (CO) celkem pro t\u0159i p\u0159eru\u0161en\u00ed poruchy. Po t\u00e9to sekvenci mus\u00ed jisti\u010d st\u00e1le spl\u0148ovat v\u0161echny sv\u00e9 v\u00fdkonnostn\u00ed specifikace \u2013 kontaktn\u00ed odpor v mez\u00edch, hladk\u00fd mechanick\u00fd provoz, tepeln\u00e1 a elektrick\u00e1 odolnost neovlivn\u011bna. Pot\u00e9 je podroben dal\u0161\u00edm ov\u011b\u0159ovac\u00edm test\u016fm, v\u010detn\u011b dielektrick\u00e9 v\u00fddr\u017ee a z\u00e1v\u011bre\u010dn\u00fdch funk\u010dn\u00edch kontrol.<\/p>\n<p>Pokud projde, je jisti\u010d certifikov\u00e1n pro provoz p\u0159i t\u00e9to proudov\u00e9 \u00farovni. Toto je <strong>\u201cBojovn\u00edk od pond\u011bl\u00ed do p\u00e1tku\u201d<\/strong>\u2013 jisti\u010d, na kter\u00fd se m\u016f\u017eete spolehnout, \u017ee bude spr\u00e1vn\u011b fungovat nejen jednou, ale opakovan\u011b po celou dobu \u017eivotnosti instalace.<\/p>\n<h3>Pom\u011br Ics k Icu: Mezera ve spolehlivosti<\/h3>\n<p>Zde je to, co je kritick\u00e9: <strong>Ics je v\u017edy vyj\u00e1d\u0159eno jako procento Icu.<\/strong> B\u011b\u017en\u00e9 pom\u011bry pro pr\u016fmyslov\u00e9 jisti\u010de:<\/p>\n<ul>\n<li><strong>25 % Icu<\/strong> (levn\u00e9 MCCB pro obytn\u00e9 budovy)<\/li>\n<li><strong>50 % Icu<\/strong> (z\u00e1kladn\u00ed pr\u016fmyslov\u00e9 MCCB)<\/li>\n<li><strong>75 % Icu<\/strong> (standardn\u00ed pr\u016fmyslov\u00e9 MCCB)<\/li>\n<li><strong>100 % Icu<\/strong> (pr\u00e9miov\u00e9 pr\u016fmyslov\u00e9 MCCB a v\u011bt\u0161ina ACB)<\/li>\n<\/ul>\n<p>Jisti\u010d s 80 kA Icu a 40 kA Ics (pom\u011br 50 %) je certifikov\u00e1n pro spolehliv\u00fd provoz pouze do 40 kA p\u0159eru\u0161en\u00ed poruchy. Mezi 40 kA a 80 kA je v meze\u0159e spolehlivosti \u2013 odstran\u00ed poruchu (to Icu zaru\u010duje), ale nemus\u00ed b\u00fdt pot\u00e9 provozuschopn\u00fd.<\/p>\n<p>Toto je <strong>\u201cSlep\u00e1 skvrna Ics\u201d<\/strong> v akci: Ov\u011b\u0159\u00edte Icu, p\u0159edpokl\u00e1d\u00e1te, \u017ee jisti\u010d je \u201cdimenzov\u00e1n\u201d pro va\u0161i \u00farove\u0148 poruchy, a nikdy nezkontrolujete, zda Ics pokr\u00fdv\u00e1 v\u00e1\u0161 skute\u010dn\u00fd p\u0159edpokl\u00e1dan\u00fd zkratov\u00fd proud. Pak dojde k prvn\u00ed skute\u010dn\u00e9 poru\u0161e, jisti\u010d pracuje p\u0159i 55 kA a pot\u00e9 je znehodnocen. Mo\u017en\u00e1 st\u00e1le funguje \u2013 nebo se kontaktn\u00ed odpor zv\u00fd\u0161il, kalibrace vypnut\u00ed se posunula a d\u00edv\u00e1te se na nespolehliv\u00e9 za\u0159\u00edzen\u00ed v kritick\u00e9 pozici.<\/p>\n<p><strong>Pro-Tip #1:<\/strong> V evropsk\u00e9 pr\u016fmyslov\u00e9 praxi je specifikace Ics = 100 % Icu standardem pro kritick\u00e9 aplikace. Cenov\u00fd rozd\u00edl je minim\u00e1ln\u00ed \u2013 obvykle o 300\u2013600 K\u010d v\u00edce za jisti\u010d se 100 % Ics oproti modelu s 50 % Ics ve stejn\u00e9 velikosti r\u00e1mu. Rozd\u00edl ve spolehlivosti je obrovsk\u00fd. Jisti\u010d s 50 kA Icu a 25 kA Ics (50 %) m\u016f\u017ee b\u00fdt po prvn\u00edm velk\u00e9m p\u0159eru\u0161en\u00ed poruchy nepou\u017eiteln\u00fd. Jisti\u010d s 50 kA Icu a 50 kA Ics (100 %) je certifikov\u00e1n pro opakovan\u00fd provoz p\u0159i pln\u00e9 poruchov\u00e9 kapacit\u011b.<\/p>\n<h3>Kdy se Ics rovn\u00e1 Icu (a kdy ne)<\/h3>\n<p>U ACB (vzduchov\u00fdch jisti\u010d\u016f) a pr\u00e9miov\u00fdch MCCB se Ics obvykle rovn\u00e1 Icu \u2013 pom\u011br 100 %. Tyto jisti\u010de jsou navr\u017eeny pro n\u00e1ro\u010dn\u00fd pr\u016fmyslov\u00fd provoz, kde je spolehlivost po poru\u0161e nezbytn\u00e1.<\/p>\n<p>U ekonomick\u00fdch MCCB a za\u0159\u00edzen\u00ed pro obytn\u00e9 budovy m\u016f\u017ee b\u00fdt Ics 25 % nebo 50 % Icu. Tyto jisti\u010de jsou ur\u010deny pro aplikace, kde jsou zkratov\u00e9 proudy ni\u017e\u0161\u00ed, nebo kde se s jisti\u010dem zach\u00e1z\u00ed jako s ob\u011btn\u00edm za\u0159\u00edzen\u00edm, kter\u00e9 se po velk\u00e9 poru\u0161e vym\u011bn\u00ed.<\/p>\n<p>Ot\u00e1zka, na kterou mus\u00edte odpov\u011bd\u011bt: Je va\u0161e instalace takov\u00e1, kde se jisti\u010d vym\u011b\u0148uje po ka\u017ed\u00e9 velk\u00e9 poru\u0161e? Nebo pot\u0159ebujete, aby z\u016fstal provozuschopn\u00fd?<\/p>\n<p><strong>Profesion\u00e1ln\u00ed tip #5:<\/strong> Nikdy nep\u0159edpokl\u00e1dejte, \u017ee vysok\u00e1 Icu automaticky znamen\u00e1 adekv\u00e1tn\u00ed Ics. Jisti\u010d se 100 kA Icu a 25 kA Ics (pom\u011br 25 %, b\u011b\u017en\u00fd u MCCB pro obytn\u00e9 budovy) NEN\u00cd vhodn\u00fd pro pr\u016fmyslov\u00e9 aplikace, kde je v\u00e1\u0161 p\u0159edpokl\u00e1dan\u00fd zkratov\u00fd proud 60 kA a z\u00e1le\u017e\u00ed na provozuschopnosti po poru\u0161e. V\u017edy ov\u011b\u0159te, zda Ics \u2265 p\u0159edpokl\u00e1dan\u00fd zkratov\u00fd proud pro spolehliv\u00fd provoz.<\/p>\n<figure><img fetchpriority=\"high\" decoding=\"async\" class=\"alignnone size-full wp-image-20269\" src=\"https:\/\/test.viox.com\/wp-content\/uploads\/2025\/11\/Icu-vs-Ics-Reliability-Comparison-chart.webp\" alt=\"Icu vs Ics Reliability Comparison chart\" width=\"800\" height=\"450\" srcset=\"https:\/\/test.viox.com\/wp-content\/uploads\/2025\/11\/Icu-vs-Ics-Reliability-Comparison-chart.webp 800w, https:\/\/test.viox.com\/wp-content\/uploads\/2025\/11\/Icu-vs-Ics-Reliability-Comparison-chart-300x169.webp 300w, https:\/\/test.viox.com\/wp-content\/uploads\/2025\/11\/Icu-vs-Ics-Reliability-Comparison-chart-768x432.webp 768w, https:\/\/test.viox.com\/wp-content\/uploads\/2025\/11\/Icu-vs-Ics-Reliability-Comparison-chart-18x10.webp 18w, https:\/\/test.viox.com\/wp-content\/uploads\/2025\/11\/Icu-vs-Ics-Reliability-Comparison-chart-600x338.webp 600w\" sizes=\"(max-width: 800px) 100vw, 800px\" \/><figcaption>Obr\u00e1zek 1: Srovn\u00e1n\u00ed spolehlivosti Icu vs Ics. Vlevo: Jisti\u010d s vysokou Icu, ale n\u00edzkou Ics (pom\u011br 50 %) se m\u016f\u017ee po\u0161kodit a st\u00e1t se nespolehliv\u00fdm po prvn\u00edm velk\u00e9m p\u0159eru\u0161en\u00ed poruchy. Vpravo: Jisti\u010d s Ics = 100 % Icu je certifikov\u00e1n pro opakovan\u00fd provoz p\u0159i pln\u00e9 poruchov\u00e9 kapacit\u011b \u2013 \u201cBojovn\u00edk od pond\u011bl\u00ed do p\u00e1tku\u201d, kter\u00fd z\u016fst\u00e1v\u00e1 provozuschopn\u00fd po odstran\u011bn\u00ed poruch. Tento vizu\u00e1l ilustruje kritickou mezeru ve spolehlivosti, kterou in\u017een\u00fd\u0159i \u010dasto p\u0159ehl\u00e9dnou, kdy\u017e kontroluj\u00ed pouze Icu.<\/figcaption><\/figure>\n<hr \/>\n<h2>Icw: Str\u00e1\u017ece selektivity (kr\u00e1tkodob\u00fd v\u00fddr\u017en\u00fd proud)<\/h2>\n<p><strong>Icw<\/strong> je jmenovit\u00fd kr\u00e1tkodob\u00fd v\u00fddr\u017en\u00fd proud \u2013 maxim\u00e1ln\u00ed zkratov\u00fd proud, kter\u00fd m\u016f\u017ee jisti\u010d v\u00e9st po stanovenou kr\u00e1tkou dobu (obvykle 0,05, 0,1, 0,25, 0,5 nebo 1,0 sekundy) bez vypnut\u00ed nebo po\u0161kozen\u00ed. Tato jmenovit\u00e1 hodnota existuje, aby umo\u017enila \u010dasov\u011b zpo\u017ed\u011bnou selektivitu v distribu\u010dn\u00edch syst\u00e9mech.<\/p>\n<p>Ale zde je prvn\u00ed v\u011bc, kterou mus\u00edte v\u011bd\u011bt: <strong>Ne v\u0161echny jisti\u010de maj\u00ed jmenovitou hodnotu Icw.<\/strong><\/p>\n<p>IEC 60947-2 definuje dv\u011b kategorie selektivity:<\/p>\n<ul>\n<li><strong>Kategorie A:<\/strong> Jisti\u010de bez \u00famysln\u00e9ho zpo\u017ed\u011bn\u00ed zkratu. Tyto vyp\u00ednaj\u00ed okam\u017eit\u011b (nebo t\u00e9m\u011b\u0159 okam\u017eit\u011b), kdy\u017e poruchov\u00fd proud p\u0159ekro\u010d\u00ed jejich okam\u017eit\u00e9 nastaven\u00ed vypnut\u00ed. V\u011bt\u0161ina MCCB pro motorov\u00e9 v\u00fdvody, koncov\u00e9 rozvody a odbo\u010dn\u00e9 obvody jsou za\u0159\u00edzen\u00ed kategorie A. <strong>Jisti\u010de kategorie A nemaj\u00ed jmenovitou hodnotu Icw.<\/strong><\/li>\n<li><strong>Kategorie B:<\/strong> Jisti\u010de, kter\u00e9 lze nastavit s \u00famysln\u00fdm zpo\u017ed\u011bn\u00edm zkratu, co\u017e umo\u017e\u0148uje za\u0159\u00edzen\u00edm um\u00edst\u011bn\u00fdm n\u00ed\u017ee v s\u00edti nejprve odstranit poruchy (selektivita). Tyto jisti\u010de mus\u00ed vydr\u017eet poruchov\u00fd proud po dobu zpo\u017ed\u011bn\u00ed bez po\u0161kozen\u00ed. <strong>Pouze jisti\u010de kategorie B maj\u00ed jmenovitou hodnotu Icw.<\/strong><\/li>\n<\/ul>\n<p>Typicky, ACBs a vysoce v\u00fdkonn\u00e9 MCCB pou\u017e\u00edvan\u00e9 jako hlavn\u00ed p\u0159\u00edvody, propojovac\u00ed jisti\u010de nebo v\u00fdvodov\u00e9 jisti\u010de v odstup\u0148ovan\u00fdch distribu\u010dn\u00edch syst\u00e9mech jsou za\u0159\u00edzen\u00ed kategorie B.<\/p>\n<h3>Pro\u010d na Icw z\u00e1le\u017e\u00ed: Selektivita v akci<\/h3>\n<p>P\u0159edstavte si t\u0159\u00edstup\u0148ov\u00fd distribu\u010dn\u00ed syst\u00e9m:<\/p>\n<ol>\n<li><strong>Hlavn\u00ed p\u0159\u00edvodn\u00ed jisti\u010d<\/strong> (Kategorie B, s jmenovitou hodnotou Icw)<\/li>\n<li><strong>V\u00fdvodov\u00e9 jisti\u010de<\/strong> do r\u016fzn\u00fdch sekc\u00ed z\u00e1vodu (kategorie A nebo B, v z\u00e1vislosti na velikosti)<\/li>\n<li><strong>Jisti\u010de odbo\u010dn\u00fdch obvod\u016f<\/strong> pro jednotliv\u00e9 z\u00e1t\u011b\u017ee (kategorie A)<\/li>\n<\/ol>\n<p>Dojde k poru\u0161e na odbo\u010dn\u00e9m obvodu. Chcete, aby vypnul pouze jisti\u010d odbo\u010dn\u00e9ho obvodu, p\u0159i\u010dem\u017e v\u00fdvodov\u00fd a hlavn\u00ed p\u0159\u00edvodn\u00ed jisti\u010d z\u016fstanou sepnut\u00e9, aby zbytek z\u00e1vodu z\u016fstal v provozu. To je selektivita.<\/p>\n<p>K dosa\u017een\u00ed tohoto c\u00edle mus\u00ed m\u00edt v\u00fdvodov\u00e9 a hlavn\u00ed p\u0159\u00edvodn\u00ed jisti\u010de nastaven\u00ed zpo\u017ed\u011bn\u00ed zkratu: \u201cPo\u010dkejte 0,1 sekundy, abyste zjistili, zda n\u011bco n\u00ed\u017ee v s\u00edti odstran\u00ed poruchu, ne\u017e vypnu.\u201d B\u011bhem t\u00e9to 0,1sekundov\u00e9 prodlevy nese jisti\u010d um\u00edst\u011bn\u00fd v\u00fd\u0161e v s\u00edti pln\u00fd poruchov\u00fd proud. Pokud je porucha 40 kA a jmenovit\u00e1 hodnota Icw hlavn\u00edho p\u0159\u00edvodu je pouze 30 kA po dobu 0,1 sekundy, jisti\u010d utrp\u00ed tepeln\u00e9 a mechanick\u00e9 po\u0161kozen\u00ed b\u011bhem prodlevy \u2013 i kdy\u017e \u00fasp\u011b\u0161n\u011b zpozdil sv\u00e9 vypnut\u00ed.<\/p>\n<p>Proto se Icw naz\u00fdv\u00e1 <strong>\u201cStr\u00e1\u017ece selektivity\u201d<\/strong>\u2014ur\u010duje, zda v\u00e1\u0161 jisti\u010d um\u00edst\u011bn\u00fd v\u00fd\u0161e v s\u00edti dok\u00e1\u017ee udr\u017eet br\u00e1nu dostate\u010dn\u011b dlouho, aby mohla zas\u00e1hnout ochrana um\u00edst\u011bn\u00e1 n\u00ed\u017ee v s\u00edti.<\/p>\n<p><strong>Pro-Tip #2:<\/strong> Pokud v\u00e1\u0161 jisti\u010d nem\u00e1 ve sv\u00e9m datov\u00e9m listu jmenovitou hodnotu Icw, jedn\u00e1 se o za\u0159\u00edzen\u00ed kategorie A s okam\u017eit\u00fdm vypnut\u00edm \u2013 nepokou\u0161ejte se jej pou\u017e\u00edvat pro selektivitu s \u00famysln\u00fdm zpo\u017ed\u011bn\u00edm zkratu. Pouze jisti\u010de kategorie B (typicky ACBs a vysoce v\u00fdkonn\u00e9 MCCB) mohou podporovat \u010dasov\u011b zpo\u017ed\u011bnou koordinaci prost\u0159ednictv\u00edm Icw. Pokus o vnucen\u00ed jisti\u010de kategorie A do role selektivity povede k ru\u0161iv\u00e9mu vyp\u00edn\u00e1n\u00ed nebo po\u0161kozen\u00ed jisti\u010de.<\/p>\n<h3>Kdy na Icw nez\u00e1le\u017e\u00ed<\/h3>\n<p>Pro obvody motorov\u00fdch v\u00fdvod\u016f, koncov\u00e9 rozvodn\u00e9 panely a v\u011bt\u0161inu aplikac\u00ed odbo\u010dn\u00fdch obvod\u016f je Icw irelevantn\u00ed. Tyto jisti\u010de jsou za\u0159\u00edzen\u00ed kategorie A navr\u017een\u00e1 tak, aby vypnula co nejrychleji, kdy\u017e dojde k poru\u0161e. \u017d\u00e1dn\u00e9 zpo\u017ed\u011bn\u00ed, \u017e\u00e1dn\u00e1 selektivn\u00ed koordinace na \u00farovni jisti\u010de (m\u016f\u017eete pou\u017e\u00edt pojistky nebo jin\u00e1 za\u0159\u00edzen\u00ed pro koordinaci), a proto nen\u00ed pot\u0159eba kr\u00e1tkodob\u00e1 v\u00fddr\u017e.<\/p>\n<p>V\u00e1\u0161 kontroln\u00ed seznam specifikac\u00ed pro tyto aplikace: Icu a Ics. To je v\u0161e. Icw se nepou\u017eije.<\/p>\n<figure><img decoding=\"async\" class=\"alignnone size-full wp-image-20270\" src=\"https:\/\/test.viox.com\/wp-content\/uploads\/2025\/11\/IEC-60947-2-Selectivity-Categories-Diagram.webp\" alt=\"IEC 60947-2 Selectivity Categories Diagram\" width=\"800\" height=\"450\" srcset=\"https:\/\/test.viox.com\/wp-content\/uploads\/2025\/11\/IEC-60947-2-Selectivity-Categories-Diagram.webp 800w, https:\/\/test.viox.com\/wp-content\/uploads\/2025\/11\/IEC-60947-2-Selectivity-Categories-Diagram-300x169.webp 300w, https:\/\/test.viox.com\/wp-content\/uploads\/2025\/11\/IEC-60947-2-Selectivity-Categories-Diagram-768x432.webp 768w, https:\/\/test.viox.com\/wp-content\/uploads\/2025\/11\/IEC-60947-2-Selectivity-Categories-Diagram-18x10.webp 18w, https:\/\/test.viox.com\/wp-content\/uploads\/2025\/11\/IEC-60947-2-Selectivity-Categories-Diagram-600x338.webp 600w\" sizes=\"(max-width: 800px) 100vw, 800px\" \/><figcaption>Obr\u00e1zek 2: Kategorie selektivity podle IEC 60947-2. Jisti\u010de kategorie A vyp\u00ednaj\u00ed okam\u017eit\u011b a nemaj\u00ed jmenovit\u00e9 hodnoty Icw \u2013 vhodn\u00e9 pro motorov\u00e9 v\u00fdvody a koncov\u00e9 rozvody. Jisti\u010de kategorie B lze nastavit s \u00famysln\u00fdm zpo\u017ed\u011bn\u00edm zkratu a maj\u00ed jmenovit\u00e9 hodnoty Icw \u2013 nezbytn\u00e9 pro hlavn\u00ed p\u0159\u00edvody a propojovac\u00ed jisti\u010de, kde je vy\u017eadov\u00e1na selektivn\u00ed koordinace. Pokus o pou\u017eit\u00ed jisti\u010de kategorie A v roli selektivity povede k ru\u0161iv\u00e9mu vyp\u00edn\u00e1n\u00ed nebo po\u0161kozen\u00ed.<\/figcaption><\/figure>\n<hr \/>\n<h2>Icm: Okam\u017eik sepnut\u00ed (mezn\u00ed zap\u00ednac\u00ed schopnost p\u0159i zkratu)<\/h2>\n<p><strong>Icm<\/strong> je jmenovit\u00e1 mezn\u00ed zap\u00ednac\u00ed schopnost p\u0159i zkratu \u2013 nejvy\u0161\u0161\u00ed \u0161pi\u010dkov\u00fd okam\u017eit\u00fd proud, kter\u00fd m\u016f\u017ee jisti\u010d sepnout (sepnout do) za specifikovan\u00fdch testovac\u00edch podm\u00ednek. Tato jmenovit\u00e1 hodnota se t\u00fdk\u00e1 sc\u00e9n\u00e1\u0159e, na kter\u00fd v\u011bt\u0161ina in\u017een\u00fdr\u016f nemysl\u00ed: Co se stane, kdy\u017e sepnete jisti\u010d, kdy\u017e ji\u017e v obvodu existuje porucha?<\/p>\n<p>Zn\u00ed to jako okrajov\u00fd p\u0159\u00edpad, ale nen\u00ed:<\/p>\n<ul>\n<li><strong>Automatick\u00e9 p\u0159ep\u00edna\u010de<\/strong> kter\u00e9 se mohou sepnout do ji\u017e existuj\u00edc\u00ed poruchy b\u011bhem p\u0159ep\u00edn\u00e1n\u00ed zdroje<\/li>\n<li><strong>Ru\u010dn\u00ed op\u011btovn\u00e9 zapnut\u00ed<\/strong> po poru\u0161e, kter\u00e1 nebyla lokalizov\u00e1na a odstran\u011bna<\/li>\n<li><strong>Paraleln\u00ed operace<\/strong> kde se jisti\u010de sepnou, aby se synchronizovaly s \u017eivou sb\u011brnic\u00ed<\/li>\n<li><strong>Obnoven\u00ed zdroje<\/strong> po odstran\u011bn\u00ed poruchy v\u00fd\u0161e v s\u00edti, kde p\u0159etrv\u00e1vaj\u00ed poruchy n\u00ed\u017ee v s\u00edti<\/li>\n<\/ul>\n<p>V okam\u017eiku, kdy se jisti\u010d sepne do poruchy, jsou zap\u00ednac\u00ed s\u00edly obrovsk\u00e9 \u2013 mnohem vy\u0161\u0161\u00ed ne\u017e ust\u00e1len\u00fd poruchov\u00fd proud. Prvn\u00ed p\u016flvlna proudu zahrnuje \u0161pi\u010dkovou nesymetrickou slo\u017eku, kter\u00e1 m\u016f\u017ee b\u00fdt 2,0 a\u017e 2,5kr\u00e1t vy\u0161\u0161\u00ed ne\u017e efektivn\u00ed hodnota ust\u00e1len\u00e9ho poruchov\u00e9ho proudu, v z\u00e1vislosti na \u00fa\u010din\u00edku obvodu (nebo pom\u011bru X\/R).<\/p>\n<p>Toto je <strong>\u201cOkam\u017eik sepnut\u00ed\u201d<\/strong>\u2014nejn\u00e1siln\u011bj\u0161\u00ed okam\u017eik v provozn\u00edm \u017eivot\u011b jisti\u010de.<\/p>\n<h3>V\u00fdpo\u010det Icm: Vztah k-faktoru<\/h3>\n<p>IEC 60947-2 definuje Icm pomoc\u00ed multiplik\u00e1toru (k-faktoru) aplikovan\u00e9ho na Icu. K-faktor z\u00e1vis\u00ed na \u00fa\u010din\u00edku zkratu (cos\u03c6) testovac\u00edho obvodu, kter\u00fd se m\u011bn\u00ed s jmenovitou hodnotou Icu:<\/p>\n<table border=\"1\">\n<thead>\n<tr>\n<th>Rozsah Icu<\/th>\n<th>Testovac\u00ed \u00fa\u010din\u00edk (cos\u03c6)<\/th>\n<th>k-Faktor<\/th>\n<th>\u0160pi\u010dka Icm<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>6\u201310 kA<\/td>\n<td>0.5<\/td>\n<td>1.7<\/td>\n<td>1,7 \u00d7 Icu<\/td>\n<\/tr>\n<tr>\n<td>10\u201320 kA<\/td>\n<td>0.3<\/td>\n<td>2.0<\/td>\n<td>2,0 \u00d7 Icu<\/td>\n<\/tr>\n<tr>\n<td>20\u201350 kA<\/td>\n<td>0.25<\/td>\n<td>2.1<\/td>\n<td>2.1 \u00d7 Icu<\/td>\n<\/tr>\n<tr>\n<td>\u226550 kA<\/td>\n<td>0.2<\/td>\n<td>2.2<\/td>\n<td>2,2 \u00d7 Icu<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p><strong>P\u0159\u00edklad:<\/strong> Jisti\u010d se 100 kA Icu (v rozsahu \u226550 kA) m\u00e1 standardizovanou hodnotu Icm alespo\u0148 2,2 \u00d7 100 kA = <strong>220 kA \u0161pi\u010dka<\/strong>.<\/p>\n<p>Pokud je potenci\u00e1ln\u00ed poruchov\u00fd proud va\u0161eho syst\u00e9mu 90 kA RMS a pom\u011br X\/R indikuje \u0161pi\u010dkovou nesymetrickou slo\u017eku 200 kA, mus\u00ed b\u00fdt Icm va\u0161eho jisti\u010de alespo\u0148 200 kA \u0161pi\u010dka, aby se bezpe\u010dn\u011b sepnul do t\u00e9to poruchy.<\/p>\n<p><strong>Profesion\u00e1ln\u00ed tip #3:<\/strong> Pro ov\u011b\u0159en\u00ed zap\u00ednac\u00ed schopnosti pou\u017eijte standardizovan\u00fd k-faktor z IEC 60947-2: Pro jisti\u010de se jmenovitou hodnotou \u226550 kA Icu by m\u011bla b\u00fdt hodnota Icm alespo\u0148 2,2 \u00d7 Icu (\u0161pi\u010dka). Jisti\u010d se 100 kA pot\u0159ebuje Icm \u2265 220 kA \u0161pi\u010dka, aby se bezpe\u010dn\u011b sepnul do poruchy. V\u011bt\u0161ina modern\u00edch jisti\u010d\u016f je navr\u017eena s Icm odpov\u00eddaj\u00edc\u00ed jejich jmenovit\u00e9 hodnot\u011b Icu, ale v\u017edy ov\u011b\u0159te tuto specifikaci pro aplikace p\u0159ep\u00edna\u010d\u016f, automatick\u00e9 op\u011btovn\u00e9 zap\u00edn\u00e1n\u00ed nebo jak\u00fdkoli sc\u00e9n\u00e1\u0159, kdy by se jisti\u010d mohl sepnout za podm\u00ednek poruchy.<\/p>\n<figure><img decoding=\"async\" class=\"alignnone size-full wp-image-20271\" src=\"https:\/\/test.viox.com\/wp-content\/uploads\/2025\/11\/Icm-Making-Capacity-Calculation-table.webp\" alt=\"Icm Making Capacity Calculation table\" width=\"800\" height=\"450\" srcset=\"https:\/\/test.viox.com\/wp-content\/uploads\/2025\/11\/Icm-Making-Capacity-Calculation-table.webp 800w, https:\/\/test.viox.com\/wp-content\/uploads\/2025\/11\/Icm-Making-Capacity-Calculation-table-300x169.webp 300w, https:\/\/test.viox.com\/wp-content\/uploads\/2025\/11\/Icm-Making-Capacity-Calculation-table-768x432.webp 768w, https:\/\/test.viox.com\/wp-content\/uploads\/2025\/11\/Icm-Making-Capacity-Calculation-table-18x10.webp 18w, https:\/\/test.viox.com\/wp-content\/uploads\/2025\/11\/Icm-Making-Capacity-Calculation-table-600x338.webp 600w\" sizes=\"(max-width: 800px) 100vw, 800px\" \/><figcaption>Obr\u00e1zek 3: V\u00fdpo\u010det zap\u00ednac\u00ed schopnosti Icm podle IEC 60947-2. K-faktor (multiplik\u00e1tor z Icu na \u0161pi\u010dkovou Icm) z\u00e1vis\u00ed na \u00fa\u010din\u00edku zkratu, kter\u00fd se m\u011bn\u00ed s jmenovitou hodnotou Icu. Pro jisti\u010de se jmenovitou hodnotou \u226550 kA Icu mus\u00ed b\u00fdt Icm alespo\u0148 2,2 \u00d7 Icu \u0161pi\u010dka. P\u0159\u00edklad: Jisti\u010d se 100 kA pot\u0159ebuje Icm \u2265 220 kA \u0161pi\u010dka, aby se bezpe\u010dn\u011b sepnul do poruchy. Pou\u017eijte tuto tabulku k ov\u011b\u0159en\u00ed zap\u00ednac\u00ed schopnosti pro p\u0159ep\u00edna\u010de, automatick\u00e9 op\u011btovn\u00e9 zap\u00edn\u00e1n\u00ed a paraleln\u00ed aplikace.<\/figcaption><\/figure>\n<h3>Kdy na Icm z\u00e1le\u017e\u00ed nejv\u00edce<\/h3>\n<p>Pro v\u011bt\u0161inu pevn\u00fdch instalac\u00ed, kde se jisti\u010de sepnou za norm\u00e1ln\u00edch (bezporuchov\u00fdch) podm\u00ednek a pouze se otev\u00edraj\u00ed, aby odstranily poruchy, je ov\u011b\u0159en\u00ed Icm sekund\u00e1rn\u00ed \u2013 standardn\u00ed Icm v\u00fdrobce pro danou Icu je obvykle dosta\u010duj\u00edc\u00ed.<\/p>\n<p>Ale pro p\u0159ep\u00edna\u010de, automatick\u00e9 syst\u00e9my op\u011btovn\u00e9ho zap\u00edn\u00e1n\u00ed nebo aplikace, kde je sepnut\u00ed do poruchy v\u011brohodn\u00fd sc\u00e9n\u00e1\u0159, se Icm st\u00e1v\u00e1 prim\u00e1rn\u00ed specifikac\u00ed. Ov\u011b\u0159te oboj\u00ed:<\/p>\n<ol>\n<li>Icm \u2265 \u0161pi\u010dkov\u00fd nesymetrick\u00fd poruchov\u00fd proud pro v\u00e1\u0161 syst\u00e9m<\/li>\n<li>Mechanick\u00e1 a elektrick\u00e1 konstrukce jisti\u010de je vhodn\u00e1 pro zap\u00ednac\u00ed provoz (n\u011bkter\u00e9 jisti\u010de jsou \u201cpouze vyp\u00ednac\u00ed\u201d a nejsou dimenzov\u00e1ny pro zap\u00edn\u00e1n\u00ed do poruch)<\/li>\n<\/ol>\n<hr \/>\n<h2>Na kter\u00fdch jmenovit\u00fdch hodnot\u00e1ch z\u00e1le\u017e\u00ed pro va\u0161i aplikaci<\/h2>\n<p>Nyn\u00ed, kdy\u017e rozum\u00edte tomu, co ka\u017ed\u00e1 jmenovit\u00e1 hodnota znamen\u00e1, zde je aplika\u010dn\u00ed logika:<\/p>\n<h3>Obvody motorov\u00fdch v\u00fdvod\u016f (kategorie A, okam\u017eit\u00e9 vypnut\u00ed)<\/h3>\n<ul>\n<li><strong>Priorita 1:<\/strong> Icu \u2265 potenci\u00e1ln\u00edmu poruchov\u00e9mu proudu (s rezervou 10-20 %)<\/li>\n<li><strong>Priorita 2:<\/strong> Ics co nejvy\u0161\u0161\u00ed \u2013 ide\u00e1ln\u011b 75-100 % Icu pro pr\u016fmyslovou spolehlivost<\/li>\n<li><strong>Priorita 3:<\/strong> Ov\u011b\u0159te Icm \u2265 k \u00d7 Icu dle normy IEC (obvykle automatick\u00e9, pokud je jisti\u010d spr\u00e1vn\u011b vybr\u00e1n)<\/li>\n<li><strong>Nepou\u017eiteln\u00e9:<\/strong> Icw (jisti\u010de kategorie A nemaj\u00ed zpo\u017ed\u011bn\u00ed zkratov\u00e9 spou\u0161t\u011b)<\/li>\n<\/ul>\n<p>Tyto jisti\u010de vyp\u00ednaj\u00ed okam\u017eit\u011b p\u0159i poru\u0161e. Va\u0161e spolehlivost z\u00e1vis\u00ed na Ics. Rozd\u00edl v cen\u011b mezi jisti\u010dem s 50% Ics a 100% Ics ve stejn\u00e9m r\u00e1mu je zanedbateln\u00fd ve srovn\u00e1n\u00ed s n\u00e1klady na v\u00fdm\u011bnu jisti\u010de po poru\u0161e a prostoje v\u00fdroby.<\/p>\n<h3>Hlavn\u00ed p\u0159\u00edvody a propojovac\u00ed jisti\u010de (kategorie B, selektivn\u00ed koordinace)<\/h3>\n<ul>\n<li><strong>Priorita 1:<\/strong> Icu \u2265 potenci\u00e1ln\u00ed poruchov\u00fd proud<\/li>\n<li><strong>Priorita 2:<\/strong> Icw \u2265 potenci\u00e1ln\u00edmu poruchov\u00e9mu proudu pro nastaven\u00e9 zpo\u017ed\u011bn\u00ed zkratov\u00e9 spou\u0161t\u011b (ov\u011b\u0159te proud I \u010das: nap\u0159. Icw = 50 kA po dobu 0,5 sekundy)<\/li>\n<li><strong>Priorita 3:<\/strong> Ics = 100 % Icu (standard pro ACBs a pr\u00e9miov\u00e9 MCCBs)<\/li>\n<li><strong>Priorita 4:<\/strong> Ov\u011b\u0159te Icm \u2265 k \u00d7 Icu<\/li>\n<\/ul>\n<p>Pro tyto aplikace se Icw st\u00e1v\u00e1 kritick\u00fdm. Pokud nastav\u00edte 0,5sekundov\u00e9 zpo\u017ed\u011bn\u00ed zkratov\u00e9 spou\u0161t\u011b pro selektivitu, Icw jisti\u010de mus\u00ed pokr\u00fdt v\u00e1\u0161 potenci\u00e1ln\u00ed poruchov\u00fd proud po celou tuto dobu.<\/p>\n<h3>P\u0159ep\u00edna\u010de (potenci\u00e1ln\u00ed sepnut\u00ed do zkratu)<\/h3>\n<ul>\n<li><strong>Priorita 1:<\/strong> Icu \u2265 potenci\u00e1ln\u00ed poruchov\u00fd proud<\/li>\n<li><strong>Priorita 2:<\/strong> Icm \u2265 \u0161pi\u010dkov\u00e9mu asymetrick\u00e9mu poruchov\u00e9mu proudu (vypo\u010d\u00edtat z pom\u011bru X\/R va\u0161eho syst\u00e9mu)<\/li>\n<li><strong>Priorita 3:<\/strong> Ics = 100 % Icu<\/li>\n<li><strong>Priorita 4:<\/strong> Ov\u011b\u0159te, zda je jisti\u010d dimenzov\u00e1n pro sp\u00ednac\u00ed povinnost (ne v\u0161echny jisti\u010de jsou)<\/li>\n<\/ul>\n<p>Pro p\u0159ep\u00edna\u010de a automatick\u00e9 zp\u011btn\u00e9 zap\u00edn\u00e1n\u00ed se Icm posouv\u00e1 v seznamu priorit v\u00fd\u0161e. Pot\u0159ebujete m\u00edt jistotu, \u017ee jisti\u010d m\u016f\u017ee sepnout do zkratu bez sva\u0159en\u00ed kontakt\u016f nebo mechanick\u00e9ho selh\u00e1n\u00ed.<\/p>\n<p><strong>Profesion\u00e1ln\u00ed tip \u010d. 4:<\/strong> Pro obvody motorov\u00fdch v\u00fdvod\u016f s okam\u017eitou spou\u0161t\u00ed je va\u0161e hierarchie specifikac\u00ed: 1) Icu \u2265 potenci\u00e1ln\u00edmu poruchov\u00e9mu proudu, 2) Ics co nejvy\u0161\u0161\u00ed (ide\u00e1ln\u011b 75-100 % Icu), 3) Icw se nepou\u017eije, 4) Ov\u011b\u0159te Icm \u2265 k \u00d7 Icu. Pro hlavn\u00ed p\u0159\u00edvody se selektivitou p\u0159idejte Icw jako prioritu \u010d. 2 a ujist\u011bte se, \u017ee odpov\u00edd\u00e1 d\u00e9lce nastaven\u00e9ho \u010dasov\u00e9ho zpo\u017ed\u011bn\u00ed.<\/p>\n<figure><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-20272\" src=\"https:\/\/test.viox.com\/wp-content\/uploads\/2025\/11\/Application-Specific-Ratings-Matrix.webp\" alt=\"Application-Specific Ratings Matrix\" width=\"800\" height=\"450\" srcset=\"https:\/\/test.viox.com\/wp-content\/uploads\/2025\/11\/Application-Specific-Ratings-Matrix.webp 800w, https:\/\/test.viox.com\/wp-content\/uploads\/2025\/11\/Application-Specific-Ratings-Matrix-300x169.webp 300w, https:\/\/test.viox.com\/wp-content\/uploads\/2025\/11\/Application-Specific-Ratings-Matrix-768x432.webp 768w, https:\/\/test.viox.com\/wp-content\/uploads\/2025\/11\/Application-Specific-Ratings-Matrix-18x10.webp 18w, https:\/\/test.viox.com\/wp-content\/uploads\/2025\/11\/Application-Specific-Ratings-Matrix-600x338.webp 600w\" sizes=\"(max-width: 800px) 100vw, 800px\" \/><figcaption>Obr\u00e1zek 4: Matice jmenovit\u00fdch hodnot specifick\u00fdch pro aplikace. Tato stru\u010dn\u00e1 referen\u010dn\u00ed p\u0159\u00edru\u010dka ukazuje, kter\u00e9 jmenovit\u00e9 hodnoty jisti\u010d\u016f jsou kritick\u00e9, sekund\u00e1rn\u00ed nebo nepou\u017eiteln\u00e9 pro b\u011b\u017en\u00e9 aplikace. Motorov\u00e9 v\u00fdvody se zam\u011b\u0159uj\u00ed na Icu\/Ics; hlavn\u00ed p\u0159\u00edvody p\u0159id\u00e1vaj\u00ed Icw pro selektivitu; p\u0159ep\u00edna\u010de zvy\u0161uj\u00ed prioritu Icm. Ne v\u0161echny jmenovit\u00e9 hodnoty jsou stejn\u011b d\u016fle\u017eit\u00e9 pro ka\u017edou aplikaci \u2013 znalost toho, kter\u00e9 \u0159\u00edd\u00ed spolehlivost VA\u0160\u00cd instalace, je kl\u00ed\u010dem ke spr\u00e1vn\u00e9 specifikaci.<\/figcaption><\/figure>\n<hr \/>\n<h2>Z\u00e1v\u011br: Za hranice zkratek<\/h2>\n<p>Zp\u011bt k tomu selhan\u00e9mu jisti\u010di z \u00favodu: 50 kA Icu, 25 kA Ics, instalovan\u00fd v syst\u00e9mu s poruchov\u00fdm proudem 38 kA. Chyba ve specifikaci nebyla chybn\u00fd v\u00fdpo\u010det \u2013 bylo to kontrolov\u00e1n\u00ed nespr\u00e1vn\u00e9 jmenovit\u00e9 hodnoty.<\/p>\n<p>Icu, Ics, Icw a Icm nejsou zam\u011bniteln\u00e9. Ne v\u0161echny jsou stejn\u011b d\u016fle\u017eit\u00e9 pro ka\u017edou aplikaci. A datov\u00fd list v\u00e1m ne\u0159ekne, kter\u00e9 \u0159\u00edd\u00ed spolehlivost VA\u0160\u00cd instalace.<\/p>\n<p>Hierarchie je:<\/p>\n<ul>\n<li><strong>Icu<\/strong> je v\u00e1\u0161 vstupn\u00ed po\u017eadavek \u2013 jisti\u010d mus\u00ed zvl\u00e1dnout maxim\u00e1ln\u00ed potenci\u00e1ln\u00ed poruchov\u00fd proud.<\/li>\n<li><strong>Ics<\/strong> je va\u0161e metrika spolehlivosti \u2013 jmenovit\u00e1 hodnota, kter\u00e1 ur\u010duje provozuschopnost po poru\u0161e.<\/li>\n<li><strong>Icw<\/strong> je v\u00e1\u0161 n\u00e1stroj pro selektivitu \u2013 relevantn\u00ed pouze pro jisti\u010de kategorie B se zpo\u017ed\u011bn\u00edm zkratov\u00e9 spou\u0161t\u011b.<\/li>\n<li><strong>Icm<\/strong> je va\u0161e ov\u011b\u0159en\u00ed sp\u00ednac\u00ed schopnosti \u2013 kritick\u00e9 pro p\u0159ep\u00edna\u010de a aplikace s automatick\u00fdm zp\u011btn\u00fdm zap\u00edn\u00e1n\u00edm.<\/li>\n<\/ul>\n<p>V\u011bt\u0161ina chyb ve specifikac\u00edch se stane v kroku dva: adekv\u00e1tn\u00ed Icu, nedostate\u010dn\u00e9 Ics. \u0158e\u0161en\u00ed je jednoduch\u00e9 \u2013 specifikujte Ics \u2265 potenci\u00e1ln\u00edmu poruchov\u00e9mu proudu a pro kritick\u00e9 pr\u016fmyslov\u00e9 aplikace trvejte na Ics = 100 % Icu. Cenov\u00fd rozd\u00edl je mal\u00fd. Zv\u00fd\u0161en\u00ed spolehlivosti je z\u00e1sadn\u00ed.<\/p>\n<p>Va\u0161e <a href=\"https:\/\/test.viox.com\/cs\/mcb\/\">jisti\u010d<\/a>\u2018m\u00e1 za \u00fakol chr\u00e1nit va\u0161i instalaci a z\u016fstat p\u0159ipraven na dal\u0161\u00ed poruchu. V\u0161echny \u010dty\u0159i jmenovit\u00e9 hodnoty jsou d\u016fle\u017eit\u00e9 \u2013 ale pouze pokud v\u00edte, kter\u00e9 zkontrolovat pro va\u0161i aplikaci.<\/p>\n<p><strong>Norem A Zdroj\u016f, Kter\u00e9 Odkazuje:<\/strong><\/p>\n<ul>\n<li>IEC 60947-2:2024 (Sp\u00ednac\u00ed a \u0159\u00eddic\u00ed p\u0159\u00edstroje nn \u2013 \u010c\u00e1st 2: Jisti\u010de)<\/li>\n<li>IEC 60947-2:2024 Definice kategori\u00ed selektivity (kategorie A a B)<\/li>\n<li>IEC 60947-2:2024 Zku\u0161ebn\u00ed postupy zkratu (O\u2011t\u2011CO pro Icu, O\u2011CO\u2011CO pro Ics)<\/li>\n<li>IEC 60947-2:2024 Tabulky sou\u010dinitele k sp\u00ednac\u00ed schopnosti<\/li>\n<\/ul>\n<p><strong>Aktu\u00e1lnost Prohl\u00e1\u0161en\u00ed:<\/strong> V\u0161echny technick\u00e9 specifikace, definice jmenovit\u00fdch hodnot a standardn\u00ed odkazy jsou platn\u00e9 k listopadu 2025. IEC 60947-2:2024 (vyd\u00e1n\u00ed 6.0) je aktu\u00e1ln\u00ed verze, publikovan\u00e1 v z\u00e1\u0159\u00ed 2024.<\/p>\n<\/div>","protected":false},"excerpt":{"rendered":"<p>The spec sheet looked perfect. 50 kA Icu rating, well above your calculated 38 kA fault current. You signed off on the order, the breaker shipped, installation went smoothly. Three months later, a short circuit on the main distribution bus. The breaker cleared the fault in milliseconds\u2014exactly as designed. But when your team powered back [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":20276,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"inline_featured_image":false,"site-sidebar-layout":"default","site-content-layout":"","ast-site-content-layout":"default","site-content-style":"default","site-sidebar-style":"default","ast-global-header-display":"","ast-banner-title-visibility":"","ast-main-header-display":"","ast-hfb-above-header-display":"","ast-hfb-below-header-display":"","ast-hfb-mobile-header-display":"","site-post-title":"","ast-breadcrumbs-content":"","ast-featured-img":"","footer-sml-layout":"","ast-disable-related-posts":"","theme-transparent-header-meta":"","adv-header-id-meta":"","stick-header-meta":"","header-above-stick-meta":"","header-main-stick-meta":"","header-below-stick-meta":"","astra-migrate-meta-layouts":"set","ast-page-background-enabled":"default","ast-page-background-meta":{"desktop":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"ast-content-background-meta":{"desktop":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"footnotes":""},"categories":[1],"tags":[],"class_list":["post-20268","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-blog"],"_links":{"self":[{"href":"https:\/\/test.viox.com\/cs\/wp-json\/wp\/v2\/posts\/20268","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/test.viox.com\/cs\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/test.viox.com\/cs\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/test.viox.com\/cs\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/test.viox.com\/cs\/wp-json\/wp\/v2\/comments?post=20268"}],"version-history":[{"count":3,"href":"https:\/\/test.viox.com\/cs\/wp-json\/wp\/v2\/posts\/20268\/revisions"}],"predecessor-version":[{"id":20275,"href":"https:\/\/test.viox.com\/cs\/wp-json\/wp\/v2\/posts\/20268\/revisions\/20275"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/test.viox.com\/cs\/wp-json\/wp\/v2\/media\/20276"}],"wp:attachment":[{"href":"https:\/\/test.viox.com\/cs\/wp-json\/wp\/v2\/media?parent=20268"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/test.viox.com\/cs\/wp-json\/wp\/v2\/categories?post=20268"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/test.viox.com\/cs\/wp-json\/wp\/v2\/tags?post=20268"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}