Power supply protector, also known as air circuit breaker, is a kind of circuit breaker. It is a switch that will automatically disconnect as long as the current in the circuit exceeds the rated current. Power protector is a very important electrical appliance in low-voltage distribution network and electric drive system, which integrates control and multiple protection functions. In addition to completing the contact and breaking circuit, it can also protect the circuit or electrical equipment from short circuit, serious overload and undervoltage, and can also be used to start the motor infrequently.