Precautions for selection of molded case circuit breakers

1. The ability to break is different

There are two important goals for the breaking capacity of molded case circuit breakers: the additional operation short-circuit breaking capacity Ics (the breaking capacity required for the circuit breaker to continuously carry its additional current according to the prescribed test procedures) and the additional limit short-circuit breaking capacity Icu (the breaking capacity required for the circuit breaker to continuously carry its additional current according to the prescribed test procedures). The difference between the two lies in the additional limit short-circuit breaking ability, which refers to the ability of the circuit breaker to operate again and break the three-phase short-circuit current at the output terminal after breaking it. As for whether it can be connected and disconnected normally in the future, it is not guaranteed. However, in order to break the short circuit during operation, it is necessary to be able to break it normally multiple times under the above conditions.

2. Cooperative application between circuit breakers

The selection of a single circuit breaker directly affects the selection of all accessory circuits and wire cross-sections. Circuit breakers need to be selected based on the overall composition of the system. To ensure that any malfunction at any point of the circuit can be eliminated by the adjacent higher-level circuit breaker.