DC contactors are mainly emplyed to open and disconnect DC circuits over long distances, frequently start, stop, reverse and reverse brake DC motors, and frequently open and close lift solenoid valves, solenoid valves, clutch solenoid valves, etc.
DC Contactor Structure
DC contactors have two kinds of structures, which are three-dimensional layout and plane layout. Some products are derived from AC contactors. Therefore, the DC contactor structure and DC contactor working principle are basically the same as that of AC contactor, which are mainly composed of electromagnetic mechanism, contact system and arc extinguishing device.
- Electromagnetic Mechanism
The electromagnetic mechanism of DC contactor is composed of an iron core, a coil and an armature and a flapping structure with edge rotation and angle rotation is mainly adopted. Since the DC contactor coil is connected to the direct current, there is no eddy current in the iron core during normal operation, the iron core does not generate heat and there is no iron loss. Thus, the iron core can be made of all cast iron or cast steel. There are many DC contactor coils. In order to make the coil dissipate in a good way, the coil is usually wound into a thin cylinder. Since the magnetic flux in the magnetic core is constant, a short-circuit ring on the pole face of the magnetic core in not needed to provide. In order to ensure the reliable release of the armature, it is usually necessary to set a non-magnetic spacer between the iron core and the armature to reduce the impact on residual magnetic resistance.
- Contact System
The contact system of DC contactor comes with main contacts and auxiliary contacts. The main contacts are generally unipolar or bipolar (single pole or double pole). Because the contacts are connected or disconnected with high current, the rolling contact---finger contactor is used. On the contrary, auxiliary contacts have small switching currents and double-breakpoint bridge-type point contacts are often used.
- Arc-control Device
Since the DC arc does not have the natural zero-crossing point like the AC arc, the main contact of the DC contactor is more difficult to disconnect the large current (DC circuit) and it tends to produce a strong arc, which is easy to burn the contacts and delay the power failure. In order to quickly extinguish the arc, the DC contactor generally uses a magnetic blowing arc extinguishing device, equipped with a baffle and a clay arc extinguishing cover. The permanent magnet is used in small-capacity DC contactors to generates magnetic blowing force. While medium and large-capacity contactors adopts longitudinal slit arc extinguishing and magnetic blowing arc extinguishing method.
DC Contactor Working Principle
When the contactor coil is energized, the coil current generates a magnetic field, which causes the static iron core to generate electromagnetic attraction to attract the moving iron core and drive the contact action --- the normally closed contact is disconnected and the normally open contact is closed. The two are linked. When the coil is powered off, the electromagnetic attraction disappears and the armature is released under the action of the release spring to restore the contacts --- the normally open contact is disconnected, and the normally closed contact is closed.
Peaco Support provides a wide range of DC contactors, including DC reversing contactors, high voltage DC contactors and DC magnetic contactors. 12V DC contactors, 24V DC contactors and 48V DC contactors are available. Other coil votages can be customized.