What is an AC contactor? AC contactors are not easily accessible to ordinary families and are generally unfamiliar, but AC contactors can often be seen in electrical control cabinets. It is mainly used to connect power, used to achieve automatic control, line connection is more complex, self-locking function, can achieve long-distance control. For example, a three-phase power supply, a water pump, etc. must be turned on and off by an AC contactor. In fact, to be clear and simple, the AC contactor is an intermediate control element. It can realize frequent on and off lines and control large currents with small currents. In our production and life, it is widely used and it is of vital importance. The status. In addition, it can also be used in conjunction with thermal relays to provide some overload protection for load devices.
The principle of AC contactor
The AC contactor is a normally open, three-pole, main-contact, air-exchanging electromagnetic contactor. Its components include coils, short-circuit rings, static iron cores, moving iron cores, moving contacts, static contacts, auxiliary normally open contacts, auxiliary normally closed contacts, pressure springs, reaction springs, buffer springs, and arc extinction. Covers and other original components, AC contactor CJO, CJIO, CJ12 and other products:
Electromagnetic system: It includes coils, static iron cores and moving iron cores (also called armatures).
Contact system: It includes main contacts and auxiliary contacts. The main contact allows the main circuit to be switched on and off by means of a relatively large current, usually as one of the technical parameters of the contactor with the maximum current (ie rated current) allowed to pass through the main contact. Auxiliary contacts are only allowed to pass a relatively small current and are normally connected to the control circuit when used.
The main contacts of AC contactors are normally open contacts. The auxiliary contacts are normally open and normally closed. AC contactor with a lower rated current has four auxiliary contacts; a larger rated current with six auxiliary contacts. The three main contacts of the MAXGE SGC1 contactor are normally open; it has four auxiliary contacts, two normally open and two normally closed.
When the coil is energized, the static iron core generates an electromagnetic suction force, which attracts the moving iron core. Since the contact system is linked with the moving iron core, the moving iron core drives three moving contact pieces to act simultaneously, the main contact is closed, and the main The auxiliary mechanically connected auxiliary normally closed contact is open, and the auxiliary normally open contact is closed, thus turning on the power. When the coil is de-energized, the suction disappears. The moving part of the moving iron core separates by means of the reaction force of the spring, so that the main contact opens, the auxiliary normally closed contact mechanically connected to the main contact is closed, and the auxiliary normally open contact opens. To cut off the power supply.
The so-called normally open, normally closed refers to the state of the contact before the electromagnetic system is not energized, that is, the normally open contact means that when the coil is not energized, its moving and static contacts are in the disconnected state, and the coil is closed after being energized, so Normally open contact, also known as dynamic contact and normally closed contact, means that when the coil is not energized, its dynamic and static contacts are closed: When the coil is energized, it is disconnected, so the normally closed contact is also called a broken contact.
The use of the arc extinguishing device arc extinguishing device is to quickly cut off the arc when the main contact breaks, and can be regarded as a large current. If it is not cut off quickly, singeing and welding of the main contact will occur, so the AC Contactors generally have arc extinguishing devices. For large-capacity AC contactors, arc arc arcs are often used.
Use of AC contactor
1, the general three-phase contactor a total of 8 points, three input, three output, there are two control points. The output and input are corresponding and can be easily seen. If you want to add a self-lock, you also need to connect the wire to the control input point from one of the terminals of the output point.
2, first of all should know the principle of AC contactor. He uses external power to add to the coil to generate an electromagnetic field. After power on, the contact points will be disconnected after power off. After knowing the principle, you should make it clear that the contacts of the external power supply, that is, the two contacts of the coil, are generally at the lower part of the contactor, and each is on one side. The other few inputs and outputs are generally in the upper part and are known at a glance. Also pay attention to the voltage of the external power supply (220V or 380V), which is generally marked. Also note whether the contact point is normally closed or normally open. If you have a self-locking control, you can manage the circuit according to the principle.