Molded case circuit breakers are also known as device-type circuit breakers. All parts are sealed in plastic housings. Auxiliary contacts, undervoltage release and shunt release are modular. Due to the very compact structure, the molded case circuit breaker is basically inaccessible. It is mostly manual, and the large capacity can be selected for electric splitting.

The molded case circuit breaker is equipped with a contact, an arc extinguishing chamber, a trip unit and an operating mechanism in a plastic case, generally not considering maintenance, and is suitable for a protection switch for a branch circuit, and the overcurrent release device has a thermal magnetic field. Both the type and the electronic type, the general thermomagnetic molded case circuit breaker is a non-selective circuit breaker, only the overload long delay and short circuit instantaneous protection. The electronic molded case circuit breaker has overload long delay and short circuit. Four protection functions: delay, short-circuit transient and ground fault. Some of the new electronic molded case circuit breakers also feature a regioselective chain function. Most molded case circuit breakers are operated manually and some have motor operating mechanisms.