Low voltage circuit breakers can be seen everywhere in electrical product exhibitions and the electrical appliance market, especially plastic case circuit breakers are highly favored. Molded case circuit breakers have a two-stage protection function of overload long delay and short circuit instantaneous action, and can also be used in conjunction with module units such as leakage devices, measurement, and electrical operation. In low-voltage distribution systems, it is commonly used as a terminal switch or branch switch, replacing the commonly used fuses and knife switches in the past.