Use a circuit breaker to protect the electric motor must be the motor (mainly AC induction motor) two features: one is a certain overload capability; the second is the starting current is often times the rated current (reversible operation or reverse braking even up to more than 10 times). Therefore, in order to ensure reliable motor operation and smooth start, the choice of circuit breakers should be guided by the following principles:
(1) according to the rated current of the motor to determine the current setting for the long-delayed action circuit breakers.
(2) circuit breakers 6 times returns the current setting for the long time lag action value time longer than the actual start time of the motor.
(3) the circuit breaker instantaneous current set value: squirrel-cage motor should 8~15 times rated current of release; winding motor should 3~6 times rated current of release.
Of course, the need for frequent starting of the motor, if they run the chances are not high or open-phase protection device, fuses and magnetic starter with ways to control and protection, is more appropriate, since such protection for remote control.