Circuit breaker (English name: circuit breaker) refers to a switching device that can turn on, carry and turn off current under normal circuit conditions, and can turn on, carry and turn off current under abnormal circuit conditions (including short circuit conditions) within a specified time. [1] Circuit breakers can be used to distribute electric energy, not frequently start asynchronous motors, protect power lines and motors, and automatically cut off circuits in case of serious faults such as overload, short circuit, undervoltage, etc. Their functions are equivalent to the combination of fuse switches and over-and-under thermal relays. Moreover, it is generally not necessary to replace parts after breaking the fault current. It has been widely used at present. Circuit breakers are divided into high-voltage circuit breakers and low-voltage circuit breakers according to the scope of application. The boundary between high voltage and low voltage is vague, and those above 3kV are generally called high voltage appliances.