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What is the working principle of AC contactor?

From: Quisure2020-08-21

The AC contactor is an electromagnetic AC contactor with a NO main contact, three poles, and air as the arc extinguishing medium. Its components include: coil, short-circuit ring, static iron core, moving iron core, moving contact, static contact, auxiliary NO contact, auxiliary NC contact, pressure spring sheet, reaction spring, buffer spring, arc extinguishing The cover is composed of original parts. The appearance structure of the common AC contactor is shown in the figure below:


What is the working principle of AC contactor?


Electromagnetic system: It includes coil, static iron core and moving iron core (also called armature).


Contact system: It includes main contacts and auxiliary contacts. The main contact allows a larger current to pass through and plays the role of connecting and cutting off the main circuit. Usually, the maximum current allowed by the main contact (ie, the rated current) is one of the technical parameters of the contactor. Auxiliary contacts are only allowed to pass small currents, and are generally connected to the control circuit when used.


The main contacts of AC contactors are generally NO contacts, and the auxiliary contacts are either NO or NC. A contactor with a smaller rated current has four auxiliary contacts; a contactor with a larger rated current has six auxiliary contacts.


NO and NC refer to the state of the contacts before the electromagnetic system is energized. That is, the NO contact means that when the coil is not energized, its moving and static contacts are in an open state, and the coil is closed after it is energized. NC contact means that when the coil is not energized, its moving and static contacts are closed, and when the coil is energized, it is disconnected.


The function of the arc extinguishing device is to quickly cut off the arc when the main contact is broken. If it is not cut off quickly, the main contact singeing and welding will occur. Therefore, AC contactors generally have arc extinguishing devices. For AC contactors with larger capacity, arc extinguishing grids are often used.


The working principle structure of the AC contactor is shown in the figure below. When the coil is energized, the iron core is magnetized, attracting the armature to move downward, making the normally closed contact open and the normally open contact closed. When the coil is de-energized, the magnetic force disappears. Under the action of the reaction spring, the armature returns to the original position and the contact returns to the original state.


What is the working principle of AC contactor?


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