How to Select Circuit Breaker
According to its use, circuit breakers can be divided into distribution circuit breakers, motor protective circuit breakers, household protective circuit breakers, leakage circuit breakers, etc. According to their different protection characteristics, this paper introduces how to choose suitable circuit breakers, so that the selection of circuit breakers is as the basis.
1. Selection of circuit breakers for distribution
Distribution circuit breakers are generally used in the low-voltage network specially for the distribution of electrical energy circuit breakers, including power supply circuit breaker and load branch circuit breaker.In the selection of this type of circuit breaker, special attention should be paid 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 action current of the circuit breaker.If it is the case of wire and cable, the long delay action current setting value of the circuit breaker is desirable 80% of the allowable carrying current of the wire and cable.2) The starting time of the motor with the largest starting current in the circuit shall not be greater than the return time of the setting value of the long-delay operating current.3) Instantaneous current setting value I1:I1=1.1 (IJX + KLKIEDM).Where, Kl is the impact coefficient of the starting current of the motor, which is generally taken as Kl =1.7 ~ 2;IEDM is the rated current of a motor of the largest size.
