AC contactor is an intermediate control element. Its advantage is that it can connect and break the circuit frequently, and control the high current with small current. Working with thermal relay can also play a role of overload protection for load equipment. Because it is through the electromagnetic field suction, broken work, compared with manual division and closing circuit, it is more efficient, more flexible use, can be divided and multiple load lines, and self locking function, through manual short connection after suction, can enter the self lock state to work continuously.

AC contactor is the most commonly used low voltage control appliance in electric drive and automatic control system. As an executive element, it is used to connect, break lines, or frequently control the operation of motors and other devices. It is composed of moving and static main contacts, arc extinguishing covers, moving and static cores, auxiliary contacts and support housing. After the electromagnetic coil is energized, the moving iron core is absorbed under the electromagnetic force, directly or through the lever transmission, causes the moving contact to contact with the static contact, and connects the circuit. After the electromagnetic coil is cut off, the moving iron core is automatically returned under the action of the reset spring, commonly known as release, the contacts are separated, and the circuit is broken.

More than 90% of the automatic control power system has used AC contactor, so it can be seen how wide the scope of use is.