DC contactors are mainly used for remote connection and breaking of DC circuits and frequent start, stop, reverse and reverse brake DC motors, also used to frequently turn on and off the lifting solenoid, solenoid valve, clutch Of the electromagnetic coil and so on. DC contactor with three-dimensional arrangement and flat layout of the two structures, and some products are based on the AC contactor derived. Therefore, the DC contactor structure and working principle and AC contactor is basically the same, mainly by the electromagnetic mechanism, contact system and arc extinguishing device composed of three parts.

Electromagnetic mechanism DC contactor Electromagnetic mechanism by the iron core, coil and armature, etc., and more use around the angular rotation of the clutch structure. As the coil is through the direct current, the normal work, the core will not produce eddy current, the core does not heat, no iron loss, so the core can be made of whole cast iron or cast steel. DC contactor coil turns more, in order to make the coil heat is good, usually the coil wound into a long and thin cylindrical. As the magnetic flux in the core is constant, there is no need for a short circuit ring on the pole surface. In order to ensure reliable release of the armature, often between the core and the armature pad with non-magnetic gasket to reduce the impact of remanence. 250A or more DC contactors are often used in series double winding coil, as shown in Figure 3-2. In the figure, the coil l is the starting coil, the coil 2 is the holding coil, and a normally closed contact of the contactor is connected in parallel with the holding coil. In the circuit just after the moment, the coil 2 is normally closed contact short circuit, the coil l can get a larger current and suction. When the contactor moves, the normally closed contact is disconnected, the coil 1 and the coil 2 are connected in series. Since the voltage is constant, the current is small, but the armature can be kept to be lifted to save power and extend the life of the solenoid the goal of.

Contact system The DC contactor has main contacts and auxiliary contacts. The main contacts are generally made of unipolar or bipolar, due to contact with or disconnect the current is large, so the use of rolling contact finger contact. Auxiliary contact of the on-off current is small, often with point contact double break point bridge contact.

Oxygen extinguishing device Since the DC arc does not have a natural zero-crossing of the AC arc, the main contact of the DC contactor is more difficult to arc when breaking large currents (DC circuits), often producing strong arcs, Delayed power down. In order to quickly arc, DC contactor is generally used magnetic blowing arc extinguishing device, and equipped with partitions and clay arc cover. The use of small capacity DC contactors are also used