Motors have two characteristics: one is that the starting current is usually several times the rated current; the other is that it has a certain overload capacity. Therefore, when choosing a circuit breaker to protect the motor, we must pay attention to these two characteristics of the motor. To ensure the reliable operation of the motor, the following points should be paid attention to when selecting the circuit breaker:
1) Determine the long-delay operating current setting value of the circuit breaker with the rated current of the motor.
2) The returnable time of the 6 times long delay action current setting value of the circuit breaker> the actual starting time of the motor.
3) The instantaneous operating current setting value of the circuit breaker: cage motors should be 8-15 times the rated current of the trip unit; winding motors should be 3-6 times the rated current of the trip unit.