Contactors are certainly familiar to power workers. It is no exaggeration to say that contactors are the most frequently used electrical components in power operation so far. Contactors are not only the electronic control cabinets, but also the effective components of distribution cabinets. They play an important role in power control.

The use of Din Rail Mounted Contactor almost laid the foundation of electrical technology, the correct understanding and use of contactors is a necessary skill for every electrical workers, the following are three basic knowledge of contactors.

Taking AC contactor as an example, the principle of DC contactor is similar.

First. The basic structure of AC contactor.

Contactors are generally made up of contactor electromagnetic mechanism, contact system, arc extinguishing device, spring mechanism, bracket and pedestal and other components, for electrical workers, the most important thing we use is: AC contactor coil and contactor contact system.
The contacts of Household Contactor can be divided into main contact and auxiliary contact. The main contact is normally opened and applied in the main circuit. The auxiliary contact cooperates with the contactor coil in the control loop, and indirectly controls the operation of the circuit by controlling the contactor coil.

Two. The function of AC contactor.

The basic functions of AC contactor: after Household Contactor is electrified, the main contact is closed, the circuit is switched on, the auxiliary contact is usually closed, and the normally closed point is disconnected, so as to make the circuit have a certain dynamic change and control the normal operation of the circuit.

Three. The function and use of main contact and auxiliary contact.

1. The main contact function.
The main contact is connected in series in the main circuit (mostly motor) to connect or disconnect the circuit, so as to control the circuit (motor operation), the main contact is relatively simple.

2. Auxiliary contact function. Auxiliary contacts generally have three functions:
(1) Self locking circuit is formed. Self locking loop is the most essential and widely used basic circuit in power control.
When the start button is pressed, the coil of the Din Rail Mounted Contactor is electrically sucked in, and the main contact  of the AC contactor is closed and connected in the corresponding main circuit, which assists the normal open contact to close and forms a self-locking, so as to ensure that the circuit remains self-sustaining after the start button is released.
Practical application: the self lock circuit uses the normally open contact of the contactor and is parallel to the start button.
(2) Forming interlocking circuit.
The interlock circuit of contactor is also widely used in basic circuits.
The normal and closed contacts of the Household Contactor 1 are connected in series in the coil circuit of the AC contactor 2. Correspondingly, the normal and closed contacts of the AC contactor 2 are connected in series in the coil circuit of the AC contactor a. To put it bluntly, the two AC contactors can not work simultaneously.
Practical application: in the interlocking circuit of contactor, the constant closing point of contactor is used, and the interlocking contactor coil is connected in series.
(3) Carry out the signal transmission of the circuit.
Normally, the signal of the switch can be transmitted by the auxiliary constant opening point or constant closing point of the contactor. The simplest example: contactor control motor operation, motor stop and running signal!

Generally speaking, we use the normal opening point of the Din Rail Mounted Contactor as the indication of motor operation signal and the constant closing point as the indication of motor stop signal. Normally, the motor is in standby state, the contactor often closed point is used to turn on the stop indicator signal, telling us that the motor in the stop position, when the motor is running, the contactor closes, often open point closed, often closed point disconnected, the corresponding "stop" indicator circuit power off, "operation" indicator circuit on, at this time The signal transmitted is: stop indicating lights out and run the indicator light.