The working principle of DC contactor (such as cj20 dc contactor): when the coil is energized, the magnetic field generating coil current, the stator generates electromagnetic attraction on the moving core, and drives the contact action: normally closed contact is disconnected, normally open contacts, the two are linked. When the coil is powered off, the electromagnetic attraction disappears and the armature is released under the release of the spring so that the contact is restored and the normally open contact is broken and the normally closed contact is closed.
The same with the working principle of AC contactor, the difference is to attract the contactor coil by AC power supply, DC contactor coil attract by DC power supply, in addition to the pass into the DC contactor coil is DC, DC is not instantaneous, at any time effective value is equal, not zero, so the DC contactor the armature doesn't require to prevent the suction force smaller zero voltage of a low, short circuit ring caused by the phenomenon of vibration sound contactor.