The main purpose of AC contactor is to control the power supply circuit at the primary side, such as ① connecting or disconnecting the switching power supply of the motor to make the motor run or terminate according to the required logic; ② main power switch for soft starter or servo amplifier; ③ connecting or disconnecting the high-power machinery and equipment such as heating pipe and electric heating rod.

It can also be used to control the power supply circuit of the secondary side, such as the main switch power supply of the secondary side, the brake pedal solenoid coil of some frequent postures, etc.

AC contactor can't be used to control DC power supply. For high-power machinery and equipment, such as DC power supply of electromagnet sucker, this one has special DC contactor control.

By the way, the auxiliary contact of AC contactor can't control the primary and secondary circuit. Of course, the auxiliary contact can control the secondary circuit.

It's a wireless relay. It is used to control large current with small current or high voltage with low voltage. The main contact point is connected with three-phase five wire and group outgoing line, A1A2 is connected with electromagnetic coil, auxiliary contact is used for locking, self-locking and interlock, signal indicator light displays information or alarm signs, etc. Because I am a beginner, this is my understanding.

AC contactor is often encountered, its key function is to turn on and off the load. In addition, it can also complete self maintenance and chain joining. If it is used with other electrical appliances, such as thermal relay, it can also complete the maintenance of load. It can be said that it is the most common electrical appliances. It's also very common.