The operation principle of DC contactor is similar to that of AC contactor, but the magnetic field energy stored by inductive load is released instantaneously during DC breaking, high-energy arc is generated at breakpoint, so DC contactor is required to have certain arc extinguishing function. Medium / large capacity DC contactors usually adopt the overall structure of single break point plane layout, which is characterized by long arc distance during breaking arc extinguishing enclosure containing arc extinguishing grid. Small capacity DC contactor adopts double break point three-dimensional layout structure.

Pay attention to the following points when selecting contactor.

1. The rated voltage of the main contact is greater than equal to the rated voltage of the load.

2. The rated current of main contact shall be no less than 1.3 times of load rated current.

3. Rated voltage of coil. When the circuit is simple the use of electrical appliances is less, 220 V 380 V can be selected; when the line is complex, the use of more electrical appliances less safe places, can choose 36V, 110V 127V.

4. The number type of contact of contactor shall meet the requirements of control circuit.

5. Operating frequency (contact on / off times per hour). When the on-off current is large the on-off frequency exceeds the specified value, the contactor model with the rated current higher than one level should be selected. Otherwise, the contact will be heated seriously even fused together, resulting in the motor other loads running without phase.

DC contactor is widely used in the DC circuit of metallurgy, mining, subway, electric traction, chemical industry other departments. Because the DC current has no zero crossing point, the DC contactor will produce strong arc when breaking the circuit, especially the inductive circuit, which only affects the improvement of performance index, but also reduces the working reliability. As we all know, controllable power electronic devices have high operating frequency service life. The principle structure of Intelligent DC contactor formed by the combination of controllable power electronic devices DC contactor.