3HM1(CMl) series of moulded case circuit breaker is one of our new type products developed and manufactured by adopting international advance technology. It is supplied with rated voltage 660V and used for circuit of A．C．50Hz，rated operating voltage AC 380V．(or below)，rated operating current up to 800A for infrequent changing over and starting of the motors.Equipped with the protection devices for over-current．short circuit and undervoltage，the products are cappable of preventing damamge of circuits and supply units.
Classification of mccb
According to product poles，two kinds of three-pole and four pole are provided．
The neutral pole(N pole) of four pole has four types：
Type A：No current trip-release on N pole which making all the time；not closing and opening with the other three poles．
Type B：No current trip-release on N pole which closing and opening with the other three poles．
Type C：With current trip-release on N pole which closing and opening with tile other three poles．
Type D：With current trip-release on N pole which making all the time；not closing and opening with the other three poles．