AC contactor is an intermediate control element, its advantage is that it can frequently turn on and off the line, and control the large current with small current. It can also play a certain overload protection role for load equipment in combination with the work of thermal relay. Because it is operated by electromagnetic field suction, it is more efficient and flexible to use than manual opening and closing circuit. It can open and close multiple load lines at the same time, and also has self-locking function. After being sucked in by manual short circuit, it can enter the self-locking state for continuous work.

AC contactor is the most common low voltage control device in electric drive and automatic control system. As an executive element, it is used for connecting, breaking the line, or frequently controlling the operation of the motor and other equipment. It is composed of dynamic and static main contacts, arc extinguishing cover, dynamic and static iron core, auxiliary contacts and bracket shell. After the solenoid is energized, the moving iron core is absorbed under the action of electromagnetic force, and the dynamic contact is contacted with the static contact directly or through lever transmission, and the circuit is connected. After the power failure of the solenoid, the moving core will return automatically under the action of the return spring, which is commonly known as release, contact separation and circuit breaking.

More than 90% of the automatic control power systems use contactors, which shows how wide it is.

Working principle of AC contactor

When the coil is energized, the static iron core generates electromagnetic suction, which draws the dynamic iron core together. Because the contact system is linked with the dynamic core, the dynamic iron core drives three moving contacts to act simultaneously, the main contact is closed, the auxiliary normally closed contact connected with the main contact machine is disconnected, and the auxiliary normally open contact point is closed, so as to connect the power supply. When the coil is de energized, the suction disappears, and the linkage part of the moving iron core is separated by the reaction force of the spring, which makes the main contact open, the auxiliary normally closed contact mechanically connected with the main contact is closed, and the auxiliary normally open contact is disconnected, thus cutting off the power supply.

1： Generally, there are 8 points in total, three-way input, three-way output, and two control points. The output and input are corresponding and can be easily seen. If you want to add self-locking, you need to connect the wire from one of the terminals of the output point to the control point.

2： First of all, we should know the principle of AC contactor. He uses external power to add the coil to produce electromagnetic fields. Power on and pull in, and the contact point will be disconnected after power failure. After you know the principle, you should make sure that the contact of the external power supply, namely the two contacts of the coil, is generally at the lower part of the contactor and each side. Other input and output are generally on the upper part, as soon as they are seen. Also pay attention to the voltage of the external power supply (220V or 380V), generally marked. And pay attention to whether the contact point is normally closed or normally open. If there is self-locking control, it is OK to arrange the line according to the principle.

The load-carrying current of AC contactor is very large. Generally, the internal suction coil controls its action or not, and the control coil is operated by various types of relays connected with it. After thunder, it will trip because the relay of AC contactor has over current or grounding protection function. When lightning falls on the line, it will control the action of AC contactor and cut off the load power supply , to protect the equipment from high voltage, high current damage or safety risk of grounding

AC contactor is widely used as the power off and control circuit. AC contactor uses main contact to open and close circuit, and auxiliary contact is used to execute control command. The main contact is usually only normally open, while the auxiliary contact usually has two pairs of contacts with the function of normally open and normally closed. Small contactors are often used as intermediate relays to cooperate with the main circuit. Thus, it can control the strong current remotely or weakly

The contact of AC contactor is made of silver tungsten alloy, which has good conductivity and high temperature corrosion resistance. The contactor is also divided into permanent magnet AC contactor and electromagnetic AC contactor

The action power of AC contactor is from AC electromagnet, which is made of two "mountain" shaped young silicon steel sheets, one of which is fixed and coil is set on it, and the working voltage is available for selection. In order to make the magnetic force stable, the suction surface of the core is added with the short circuit ring. After the AC contactor is off, it depends on the spring to reset. The other is the movable core, which is constructed as the fixed core to drive the opening of the main contact and auxiliary contact.

Permanent magnet contactor is a new type of micro power contactor which replaces traditional electromagnetic drive mechanism with permanent drive mechanism

The principle of the work is to use the principle of the same-sex repulsion and the opposite phase absorption of the magnetic pole. Because the polarity of permanent magnet installed on the contactor linkage mechanism is fixed and the soft iron fixed on the contactor base under the action of external control signal, the electronic module which is solidified together produces more than ten to twenty milliseconds of positive and negative pulse current, which makes the soft iron produce different polarity, so that the main contact of the contactor can achieve the purpose of suction, retention and release.

The advantages of permanent magnet contactor are as follows: (1) the work reliability is good, and it is not interfered by the network voltage at all. (2) The speed of action is fast, which is 0.12-0.15s, and the traditional one is 0.35-0.38s. (3) It is quiet in operation, without AC noise and is not affected by dust and oil pollution. (4) The module has no temperature rise, and it is resistant to aging, corrosion and has a long service life of three times that of the traditional. (5) Maintenance free, super energy saving and environmental protection, and the power saving rate is 99%. The contactor with more than 20 amps is equipped with arc extinguishing cover, which can quickly pull off the arc by using the electromagnetic force generated when the circuit is disconnected to protect the contact.

AC contactor is made as a whole, and its appearance and performance are also improving, but its function is always unchanged. No matter how far the technology develops, AC contactor still has its important position.