Molded case circuit breaker is an important safety protection device and a basic component of power distribution system. Widely used in electric power industry, electronic industry, environmental protection industry, shipbuilding, metallurgical industry and other industries constitute stable and reliable power distribution system. The Molded case circuit breaker is a device that automatically cuts off the current when the current exceeds the tripping setting. The Molded case refers to the shell of the device with a plastic insulator, which is used to isolate the conductors and the grounded metal part. The Molded case circuit breaker has the function of leakage, short circuit and overload delay protection. The Molded case circuit breaker can not only close, carry and break the current of the normal circuit, but also shut off the abnormal operation or overload of the electric appliance. If there is a short circuit fault, the molded case circuit breaker will receive the command to automatically disconnect the switch, so as to protect the line. The molded case circuit breaker has the leakage protection device of high precision and sensitivity, so it has the super function of leakage protection. Once it exceeds the limited range of equipment, there is a danger of destroying electrical appliances and other equipment, do not cut off the power immediately, can ease for a period of time.

Molded case circuit breaker has isolation effect. The shell device of the molded case circuit breaker itself is made of plastic insulator, which is used to isolate the conductor and ground metal part. The plastic shell is sealed with all the parts, compact structure, the current exceeds the jump setting automatically cut off the current, so as to play a role in isolating and protecting the electrical equipment and personal safety.

Molded case circuit breaker limited flow breaking effect. The ability to safely cut off the fault current is a special function of the molded case circuit breaker, which has four rated short-circuit breaking capacity: rated short-circuit breaking capacity Icn, rated short-circuit breaking capacity Icu, rated short-circuit breaking capacity Ics, rated short-circuit breaking capacity Icw. The molded case circuit breaker works the same as the ordinary circuit breaker. When the short circuit is short, the magnetic field generated by the large current (generally 10 to 12 times) overcomes the reaction spring, and the trip device pulls the operating mechanism to act, and the switch trips instantaneously. When overload, the current becomes larger, the heat intensifies, the bimetal sheet deforms, and the mechanism moves (the greater the current, the shorter the operation time).