Circuit breakers for distribution are generally circuit breakers used in low-voltage power grids to distribute electrical energy, including main power circuit breakers and load branch circuit breakers. When selecting this type of circuit breaker, pay special attention to the following selection principles:
1) The allowable current carrying capacity of the line is not less than the setting value of the long-delay operating current of the circuit breaker. If wires and cables are used, the long-delay operating current setting value of the circuit breaker can be 80% of the allowable current carrying capacity of the wires and cables.
2) The starting time of the motor with the highest starting current in the circuit is not more than 3 times the returnable time of the set value of the long delay action current.
3) Instantaneous current setting value I1: I1=1.1 (Ijx+klkIedm). Among them: kl is the impact coefficient of the motor starting current, generally kl=1.7~2; Iedm is the maximum rated current of a motor.