ATSE double power automatic transfer switch by one (or several) switch electrical appliances and other necessary appliances (switching controller) which is used to monitor the power supply circuit, and the switch one or several load circuit from a power source to another power. Automatic transfer switch as end fire load or other important load change-over device, allowing the load to choose normal power supply, emergency power supply, automatic conversion and connecting the power supply, it has been widely used in projects. The correct selection of Automatic transfer switch is a key problem in the distribution system of the important load.

Automatic transfer switch has experienced four stages of development in our country, namely the contactor, circuit breaker, load switch and double throw type. Contactor switch for the first generation, is China's first production of dual power ATS automatic transfer switch, it is composed of two sets of AC contactor and its mechanical and electrical interlocking device, this device is not reliable, because of disadvantages of mechanical chain of large power consumption, less in engineering is used. Breaker type switch for the second generation, is the national standard of China and IEC standard called CB ATS automatic transfer switch, which is composed of two sets of circuit breakers and mechanical and electrical interlocking device with short circuit and overcurrent protection function, but the mechanical linkage is not reliable. Load switch type switch for the third generation, which is composed of two switch and a built-in chain combination, reliable mechanical interlock, converted by the electromagnetic coil attraction to drive the switching speed. Double throw switch to the fourth generation, which is driven by the electromagnetic force, the inner mechanical connections to maintain state, the integration of single pole double throw switch, has the advantages of simple structure, small size, its chain, conversion speed, safe and reliable, is PC ATS automatic transfer switch.