What is DC Contactor
DC contactors are mainly used for remote connection and disconnection of DC circuits, frequent start, stop, reverse and reverse connection of DC motors for braking, as well as frequent connection and disconnection of lifting electromagnets, solenoid valves, electromagnetic coils of clutches, etc.
Schematic of Contactor
Modern DC contactors are essential in new energy vehicles. There are two kinds of structures for DC contactor: three-dimensional layout and plane layout. Some products are derived from AC contactor. Therefore, the structure and working principle of DC contactor are basically the same as that of AC contactor, which is mainly composed of electromagnetic mechanism, contact system and arc extinguishing device.
Electromagnetic mechanism
The electromagnetic mechanism of DC contactor is composed of iron core, coil, armature and so on, and it mostly adopts the beat type structure which rotates around the edge angle. Due to the DC current in the coil, there will be no eddy current in the iron core during normal operation, the iron core will not be heated, and there will be no iron loss, so the iron core can be made of whole cast iron or cast steel. The coil turns of DC contactor are many. In order to make the coil cool well, the coil is usually wound into a long and thin cylinder. Because the flux in the core is constant, there is no need for a short-circuit ring on the pole surface of the core.
Contact system
DC contactor has main contact and auxiliary contact. The main contact is generally made into single pole or double pole. Because the current of contact making or breaking is large, the finger contact of rolling contact is adopted. The on-off current of the auxiliary contact is small, and the double break point bridge contact is often used.
Arc extinguishing device
Because DC arc does not have natural zero crossing like AC arc, when the main contact of DC contactor breaks large current (DC circuit), it is more difficult to extinguish arc, which often produces strong arc, easy to burn contact and delay power-off. In order to quickly extinguish the arc, the DC contactor generally adopts the magnetic blow type arc extinguishing device, which is equipped with partition board and ceramic arc extinguishing cover.
Structure Diagram of Contactor