A circuit breaker is an automatically-operated electrical switch designed to protect an electrical circuit from damage caused by excess current.
Its basic function is to interrupt current flow after a fault is detected, typically resulting from an overload or short circuit. Unlike a fuse, which operates once and then must be replaced, a circuit breaker can be reset to resume normal operation.
Classifications of circuit breakers can be made based on voltage class, construction type, interrupting type, and structural features. Circuit breakers also come in a variety of sizes: from small devices that protect low-current circuits or individual household appliances, up to large switchgear designed to protect high voltage circuits feeding heavy machinery.