Disconnect and connect the load circuit and disconnect the fault circuit to prevent the accident from spreading and to ensure safe operation. The high voltage circuit breaker must interrupt 1500V arcs with a current of 1500-2000A. These arcs can stretch up to 2m and continue to burn without being quenched. Arc extinction is therefore a problem that high voltage circuit breakers must solve.

Low-voltage circuit-breakers, also known as air circuit-breakers, can be used to switch load circuits on and off, as well as to control infrequently starting motors. Its function is equivalent to the sum of some or all of the functions of electrical devices such as knife switches, overcurrent relays, voltage loss relays, thermal relays and leakage protectors. It is an important electrical protection device in the low voltage distribution network.

Low-voltage circuit breakers have the advantages of various protection functions (overload, short-circuit, undervoltage protection, etc.), adjustable action value, high breaking capacity, convenient operation and safety, so they are widely used at present. Structure and operation The low-voltage circuit breaker consists of the operating mechanism, contacts, protective devices (various trip units) and arc extinguishing system.