A circuit breaker is a switching device that can make, carry and break current under normal circuit conditions and can make, carry and break current under abnormal circuit conditions (including short-circuit conditions) within a specified time.

A circuit breaker is a switching device that can close, carry and break current under normal circuit conditions and can close, carry and break current under abnormal circuit conditions (including short-circuit conditions) within a specified time. Circuit breakers can be used to distribute electrical energy, to start infrequent asynchronous motors and to protect power supply lines and motors. They can automatically close the circuit in the event of severe overload, short circuit or undervoltage faults. Their function is similar to that of a fuse switch. Combination with overheating and underheating relays, etc. In addition, it is generally not necessary to replace the components after the fault current has been interrupted. At present it is widely used.

A circuit breaker generally consists of a contact system, an arc extinguishing system, an operating mechanism, a release and a case. Circuit breakers are classified according to their structure into miniature circuit breakers, moulded case circuit breakers and frame circuit breakers.