1. Short time withstand current  ICW

In the MCCB with three section protection characteristics, another electrical parameter is the rated short-time withstand current ICW, which means the concept of dynamic thermal stable current, that is, the withstand current value within 1 s, which will not affect the continuous use of the circuit breaker after withstand. It is mainly to check the circuit breaker in the short delay state, to continue to ensure that the circuit breaker's own electrical parameters remain unchanged, the shell and components do not deform. There is no such value in MCCB with two section protection characteristics.

2. Protection category  A B

The traditional MCCB adopts thermal protection and electromagnetic backup protection, which can only realize the basic protection functions of overload delay and short-circuit instantaneous action, that is, it has two-stage protection characteristics. Therefore, there is no selectivity under short-circuit conditions. Generally, it can only be used as feeder circuit breaker, but not as main circuit breaker. At present, there is a large capacity and high breaking MCCB with mature three section adjustable protection characteristics of overload long delay, short-circuit short delay and super large short-circuit instantaneous action, so that MCCB can be used not only as main circuit breaker, but also in all levels with good selectivity. Therefore, MCCB is divided into non selective circuit breaker (A) and selective circuit breaker (B).