The composition and working principle of ac contactor

Promulgator : TAIXIDate : 2018-08-27Views : 1765

Contactor is mainly composed of electromagnetic system, contact system and arc extinguishing device. It is a kind of low-voltage control device widely used in automatic control system and electric drive system. Household Contactor can be divided into two types: AC contactor and DC contactor.

1. AC contactor electromagnetic system
Din Rail Mounted Contactor is used for closing and breaking contacts, including coils, moving cores and static cores. The coil is made of insulated copper conductor and is generally made into a thick and short cylindrical shape. There is a certain gap between the coil and the iron core to avoid direct contact with the iron core and burning. The core is laminated by silicon steel sheet to reduce eddy current loss in the core and avoid overheating of the core. A short-circuit ring is installed on the iron core to reduce the vibration and noise produced by the suction of the Din Rail Mounted Contactor, so it is also called a damping ring.

2. Contact system
The main contact points and auxiliary contacts are used to directly connect and break the AC main circuit and control circuit.
The main contacts are used to turn on and off the main circuit with large current, and the volume is large. Generally, there are three pairs of movable contacts; the auxiliary contacts are used to turn on and off the control circuit with low current, and the volume is small. There are movable and movable contacts. The contact is made of copper with good electrical conductivity, and silver or silver alloy blocks are embedded in the contact part to reduce the contact resistance.

3. Arc extinguishing device
Din Rail Mounted Contactor is used to rapidly extinguish the arc produced by the main contact in the breaking circuit, to protect the contact from arc burning, and to shorten the breaking time. Household Contactor with capacities of more than 10A have arc extinguishing devices. For small capacity contactors, double broken bridge contacts are often used to facilitate arc extinguishing, and a ceramic arc extinguishing cover is arranged on them. For large capacity contactors, longitudinal seam arc extinguishing cover and grid arc extinguishing structure are often adopted.

4. Other components
Other components include reaction spring, transmission mechanism and wiring post.

5. Working principle
When the coil is fed into the current, a strong magnetic field is formed in the iron core, and the moving iron core is attracted to the static iron core by the electromagnetic force. However, the movement of the moving iron core is resisted by the spring reaction force, so only when the electromagnetic force is greater than the spring reaction force, the moving iron core can be absorbed by the static iron core. When the moving iron core is sucked down, the moving contacts are contacted with the static contacts, thereby enabling the controlled circuit to be connected. When the coil is cut off, the moving iron core quickly leaves the static iron core under the action of the reaction spring, so that the dynamic and static contacts are separated and the controlled circuit is disconnected.

6. How to install AC contactor?
(1) Household Contactor should generally be installed on the vertical surface, inclination should not exceed 5 degrees; if there is a cooling hole, the hole should be placed in the vertical direction to facilitate heat dissipation; and according to the provisions of the appropriate arc space, so as to avoid arc burning adjacent electrical appliances.
(2) When installing and wiring, be careful not to lose parts or fall into the contactor. Bolts for mounting holes shall be fitted with spring washers and plain washers, and screws shall be tightened to prevent vibration from loosening.
(3) After installation, check the connection is correct and correct, operate several times without electrifying the main contact, then measure the action value and release value of the product, the measured data should meet the requirements of the product.