Three-phase motor open phase protection and current changes

Its working principle: Combination switch Q closed first, prepare for motor starting. The main circuit and control circuit and electricity, connect to A, C and two ac contactor coil KM2 electricity, iron core is sucked, concatenated in ac contactor KM1 normally open contacts closed KM2. When press the starting button SB2, ac contactor KM1 electric suction, main circuit of the three main contact closure, auxiliary contact since locking, starting motor M. When there is lack of phase motor, if the lack of A phase or C phase, ac contactor coil KM2, losing electricity concatenated in ac contactor coil KM1 contact KM2 disconnect, make the ac contactor coil KM1 lost electricity, so the lock off contact, the contact is disconnected, the motor can't start losing electricity (right now) or stop; If lack of phase B, ac contactor coil KM1 losing electricity, the lock off contact, main contact disconnect, motor power, can't start (right now) or stop the operation. Thus ensure the motor in diesel generating set the circuit of phase is not 8500w gasoline generator destroyed.