How to choose: ACB or MCCB?
This guide introduces the factors which affect circuit breaker selection: Load Fault level Discrimination Its purpose is to prompt further investigation rather than to provide a calculational procedure. Terasaki offers detailed training and further information on circuit breaker selection. The construction and operation of air circuit breakers (ACBs) and moulded case circuit breakers (MCCBs) have common features. A contact system with arc-quenching, a mechanism to operate the breaker, a system to provide a means of protection, control, and indication. However, there are some fundamental differences in the application that should be considered. Load The current carrying capacity (In, A) of the breaker should be higher than the expected load in the circuit. MCCBs are available up to 4000A from Terasaki but become less cost-effective for very large ratings (2000A and above). The advantage of MCCBs for very large ratings is their compact size. An ACB is physically larger but more cost-effe...