AC contactor a main contact normally open, three-pole, air as the arc extinguishing medium of electromagnetic low-voltage control appliances.
A, AC contactor role
1, the role of the AC contactor is to protect the circuit, can allow a large current through.
2, in the power transmission system, as a frequent or break the loaded circuit control appliances.
Second, the working principle
When the coil is energized, the static iron core generates electromagnetic suction, which sucks the movable iron core closed, because the contact system is linked with the movable iron core, so the movable iron core drives the three movable contacts to act at the same time, and the main contact closes, and the auxiliary normally-closed contact mechanically connected to the main contact is disconnected, and the auxiliary normally-open contact is closed, so as to turn on the power supply.
When the coil is disconnected, the suction disappears, and the linkage part of the movable iron core is separated by the reaction force of the spring, so that the main contact is disconnected, the auxiliary normally-closed contact mechanically linked to the main contact is closed, and the auxiliary normally-open contact is disconnected, thus cutting off the power supply.
ExpansionExpansion information
Common faults of AC contactors:
1, the main contact resistance is too large. This type of failure mostly occurs after the line short-circuit, the main contact partially ablated, uneven contact surface or oxidized metal attached. Open the contact box to check the contact erosion is not serious in the case can be filed to polish the contacts, restore the contact area to remove metal oxides. Try not to sandpaper contacts, it is said that the sandpaper on the diamond sand will be left on the contacts to affect the electrical performance.
2, contact welding. Various reasons caused by the main contact or auxiliary contact welding, the solution is only to replace the contact. In most cases, there is a contact welding, the contactor will also be attached to a lot of metal sublimation after the conductive material, affecting the dielectric properties, so it is recommended to directly replace the contactor as a whole.
3, coil joints de-welded, due to the frequent work of the contactor, especially high-current contactor work vibration. Coil joints are easy to desolder, resulting in the contactor does not work.
Reference: Baidu encyclopedia-AC contactor
Baidu encyclopedia-contactors