KNM6 series moulded case circuit breaker applies at the circuit of AC 50/60Hz,rated operation voltage of 600V(690V)and below, DC250V and below and rated current of from 12.5A up to 800A to distribute the electric power, and performs the low frequency of opening and closing under normal condition and the overload protection, short-circuit protection and under-voltage protection. The circuit breaker with a rated current of frame of 400A and below could also perform the low frequency of starting of the squirrel- cage motor and the protection in terms of operation breaking, and protect the motor in terms of overload, short circuit and under-voltage. This product conforms to the requirement of IEC60947-2, GB14048.2 standards.