断路器是指能够关合、承载和开断正常回路条件下的电流并能关合、在规定的时间内承载和开断异常回路条件下的电流的开关装置。断路器按其使用范围分为高压断路器与低压断路器，高低压界线划分比较模糊，一般将3kV以上的称为高压电器。
Circuit breaker is a kind of switching device which can turn on, load and break the current in normal circuit and can turn on, load and break the current in abnormal circuit within a specified time. Circuit breakers are divided into high-voltage circuit breakers and low-voltage circuit breakers according to their application scope. The demarcation line between high-voltage and low-voltage is relatively vague. Generally, more than 3kV is called high-voltage electrical appliances.
断路器可用来分配电能，不频繁地启动异步电动机，对电源线路及电动机等实行保护，当它们发生严重的过载或者短路及欠压等故障时能自动切断电路，其功能相当于熔断器式开关与过欠热继电器等的组合。而且在分断故障电流后一般不需要变更零部件。目前，已获得了广泛的应用。
Circuit breakers can be used to distribute electric energy, start asynchronous motors infrequently, and protect power lines and motors. When they have serious overload or short circuit and undervoltage faults, they can automatically cut off the circuit. Their functions are equivalent to the combination of fuse switches and overheating relays. And after breaking the fault current, there is no need to change parts. At present, it has been widely used.
电的产生、输送、使用中，配电是一个极其重要的环节。配电系统包括变压器和各种高低压电器设备，低压断路器则是一种使用量大面广的电器。
Distribution is an extremely important link in the generation, transmission and use of electricity. Distribution system includes transformer and various high and low voltage electrical equipment. Low voltage circuit breaker is a kind of widely used electrical equipment.