AC contactor is a kind of electromagnetic AC contactor with open main contacts, three poles and air as arc extinguishing medium. 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, arc extinguishing hood and other components. AC contactors are CJO, CJIO, CJ12 and other products. The configuration of CJO-20 AC contactors commonly used in China is shown as its main components. As shown in the following figure:
Electromagnetic system: It includes coil, static core and movable core (also known as armature).
Contact system: It includes main contact and auxiliary contact. The main contact can pass through a larger current to turn on and off the main circuit. The maximum current (rated current) allowed by the main contact is usually used as one of the technical parameters of the contactor. Auxiliary contacts are only allowed to pass through small currents and are usually connected to control circuits when used.
The main contacts of AC contactors are usually open contacts, and the auxiliary contacts are usually open or closed. The contactor with lower rated current has four auxiliary contacts, and the contactor with larger rated current has six auxiliary contacts. The three main contacts of CJ10-20 contactor are usually open; it has four auxiliary contacts, two are normally open and two are normally closed.
The so-called normally open and normally closed contact refers to the state of the contact before the electromagnetism system is not turned on. That is to say, when the coil is not turned on, its dynamic and static contacts are in the state of disconnection. When the coil is turned on, the dynamic and static contacts are closed. So the often open contact is also called the dynamic and static contacts when the coil is not electrified. When the coil is electrified, the dynamic and static contacts are closed: but when the coil is turned on, they are disconnected, so they are often closed. Also known as breaking contact.
The use of arc extinguishing device of AC contactor working principle diagram is to quickly cut off the arc when the main contact is interrupted. It can be seen as a great current. If not cut off quickly, the main contact will be burned and welded, so the AC contactor generally has arc extinguishing device. For AC contactors with large capacity, arc-extinguishing grid disaster arc is often used.
The working principle and structure of the AC contactor are shown in the following figure. When the coil is electrified, the iron core is magnetized and the armature is attracted to move downward, which makes the normally closed contacts open and closed. When the coil is cut off, the magnetic force disappears. Under the action of the reaction spring, the armature returns to its original position, even if the contact restores to its original state.
