– Icu: rated ultimate short circuit breaking capacity.

The rated breaking capacity (Icu) is the maximum fault-current a circuit breaker can successfully interrupt safely for one time. functionality is not guaranteed after it interrupts one time.

 

– Ics: rated service short circuit breaking capacity.

Ics is expressed as a percentage of Icu. 25, 50, 75, 100% for industrial circuit breakers.

It’s the short circuit value that MMS could with stand for three successive times (disconnect 3 minutes).  Whenever, Ics percentage of Icu is increased. The ability of MMS to withstand more short circuit values is increased.

– People consider Ics as short circuit capacity in design.