A circuit breaker is a switch device that can close, load and break the current under normal circuit conditions and can close, load and break the current under abnormal circuit conditions within the specified time.
Circuit breaker according to its scope of use is divided into high-voltage circuit breaker and low-voltage circuit breaker, high and low-pressure line division is relatively vague, generally will be more than 3kV is called high voltage electrical appliances. Circuit breakers can be used to distribute electricity, do not frequently start asynchronous motors, power lines and motor protection, when they occur serious overload or short-circuit and under-voltage and other failures to automatically cut off the circuit, its function is equivalent to fuse-type switch and over-heat relay and other combinations. It is generally not necessary to change the components after breaking the fault current.
At present, a wide range of applications have been obtained. In the generation, transmission and use of electricity, distribution is an extremely important link. Distribution system includes transformers and various high and low voltage electrical equipment, low-voltage circuit breaker is a large-scale use of electrical appliances.