Instantaneous vs. Inverse Time Circuit Breakers for Motors What difference does it make?

摘要

Article 430 in the National Electrical Code (NEC) recognizes two types of molded case circuit breakers (MC-CBs) - instantaneous and inverse time - for motor branch circuit short circuit and ground fault protection, in addition to fuses. There's an important difference between these two types of circuit breakers. Instantaneous trip breakers do exactly what the name implies. When the current in the circuit reaches a value that the breaker trip mechanism is set to, it will trip off instantaneously with no time delay. Instantaneous breakers are magnetic trip only. Instantaneous breakers are also referred to as motor circuit protector breakers or MCPs.