Automatic transfer switch is mainly used in emergency power supply system, switch the load circuit automatically from one power source to another power switch, so as to ensure the continuous and reliable operation of important load. Therefore, the automatic transfer switch is often used in the important electric field, and its product reliability is particularly important. Once the transformation fails, it will cause one of the following two kinds of hazards. The short circuit or important load of the power supply will cause serious consequences, which will not only bring about economic losses, but also cause social problems. Therefore, the developed countries have listed the production and use of the double power automatic switch as the key product to be restricted and regulated.

Automatic transfer switch is composed of two parts: switch body + controller. The switch body is divided into PC and CB.

PC: Automatic transfer switch that can connect, bear, but not break short-circuit current.

CB: Automatic transfer switch with over current trip, its main contact can connect and break short-circuit current.

Controller is mainly used to detect the working condition of power supply monitoring, when the monitored power failure, the controller sends commands, the switch body with a load from a power supply automatic switching to another power controller, and the switch body is connected into the line.

There are four kinds of products used in the domestic market for two-way power conversion appliances:

1. Automatic transfer switch with contactor;

2. Automatic transfer switch with circuit breaker;

3. The products which use electric load switch to complete the conversion of two power supply;

4. PC level Automatic transfer switch.