The contactor is a widely used switching device. The contactor is mainly used to frequently turn on or off the AC and DC main circuit and the large-capacity control circuit. It can be operated from a long distance. It can realize timing operation, interlocking control, various quantitative control, and loss and undervoltage protection. Widely used in automatic control circuit, the main control object is the motor, can also be used to control other electrical loads, such as electric heaters, lighting, welding machine, capacitor bank and so on.
According to the type of controlled current, the contactor can be divided into AC contactor and DC contactor. Here mainly introduces commonly used AC contactors. AC contactors can be divided into two kinds of electromagnetic and vacuum.
The contactor is mainly composed of an electromagnetic system, a contact system, an arc extinguishing system and other parts.
(1) Electromagnetic system: Electromagnetic system includes electromagnetic coil and iron core, which is an important part of the contactor, relying on it to bring the contact to close and open.
(2) Contact system: The contact is the executive part of the contactor, including the main contact and the auxiliary contact. The function of the main contacts is to switch on and off the main circuit and control the larger current, while the auxiliary contacts are in the control loop to meet the requirements of various control methods.
(3) Arc-extinguishing system: The arc-extinguishing device is used to ensure that the arc generated when the contact breaks the circuit is reliably extinguished and the damage to the contacts by the arc is reduced. In order to quickly extinguish the arc at the time of disconnection, the contactor is usually equipped with an arc extinguishing device, generally a semi-sealing longitudinal joint clay arc extinguishing hood is equipped with a strong magnetic arc blowing circuit.
(4) Other parts: Insulative housing, spring, short circuit ring, transmission mechanism, etc.