In order to understand about the kA rating of any breaker, you must know about the kA rating, what it is actually?
kA rating actually determines how much current the circuit breaker can withstand or withhold under any fault or short circuit conditions.
The circuit breaker only has to withstand this for a brief period of time, usually the time it takes for the circuit breaker to trip.
For example:
A value of 6kA means that the circuit breaker can withstand 6,000 amps of current under fault conditions during the brief time it takes to trip the Circuit Breaker.
Miniature Circuit Breaker or (MCB) is fast, and it is normally used for LV and MV systems but has a limited breaking capacity up to 10 kA only.
Note: The above existing rating of MCB is 10 kA at the rated voltage of 220/400 V.
