MCCB Ics and Icu 1

[incognito1]

can anyone explain meaning of these Icu and Ics values?

what is the meaning of that Ics=100% of Icu?

how Icu and Ics differs for different voltages?

why Icu and Ics values defined for single phase voltages as well even though MCCB is a multi pole device which will always get voltage over 400V?

 

[wbd]

Those are terms from IEC 60947 which are defined as:
Icu - Rated ultimate short circuit breaking capacity
Ics - Rated service short circuit breaking capacity

I have attached an excerpt that goes into details.

 

[incognito1]

what is the practical meaning of Ics and Icu?

 

[ScottyUK]

After opening a fault at the Ics rating the breaker should be capable of being put back into service after interrupting the fault. After opening a fault at the Icu rating the breaker may have been irrepairably damaged by interrupting the current and be incapable of further service.

The other value occasionally seen is Icw which is the withstand value for a through fault without the breaker operating - this value is found on ACBs rather than MCCBs.