MCB selection consideration for 400Hz.

Depending on the technologies used, modular circuit breakers designed for 50/60 Hz can be used at 400 Hz.

To choose the performance of a modular circuit breaker:

->do not take any thermal derating into account (In at 400 Hz is equivalent to In at 50 Hz).

->increase the magnetic tripping threshold, according to the table attached below.

->check that the short-circuit current on the installation is less than the breaking capacity of the circuit breaker. The breaking capacity of the circuit breakers at a frequency of 400 Hz is the same as at frequencies of 50/60 Hz. This characteristic is generally complied with, due to the fact that the short-circuit current of a 400 Hz

generator is relatively low. In most cases, the generator Isc does not exceed four times the rated current.

Released for: Schneider Electric India