The operating principle of the DC contactor is similar to that of the AC contactor, but the magnetic field energy stored by the inductive load is instantaneously released when the DC is disconnected, and the high-energy arc generated at the breakpoint requires the DC contactor to have a certain arc-extinguishing function. The medium/large capacity DC contactor often adopts a single breakpoint plane to arrange the overall structure, which is characterized in that the arc distance is long when the break is broken, and the arc extinguishing shield contains the arc chute. The small-capacity DC contactor adopts a double-breakpoint three-dimensional arrangement structure.
Pay attention to the following points when selecting a contactor:
1. The rated voltage of the main contact ≥ the rated voltage of the load;
2. The rated current of the main contact is ≥ 1.3 times the rated current of the load;
3. Coil rated voltage. When the line is simple and the electric appliance is used less, 220V or 380V can be used; when the line is complicated, the electric appliance is used more or less safe, 36V, 110V or 127V can be selected;
4. The number and type of contacts of the contactor should meet the requirements of the control circuit;
5. Operating frequency (number of contacts on and off per hour). When the on-off current is large and the on-off frequency exceeds the specified value, the contactor type with a rated current of one level should be selected. Otherwise, the contacts will be severely heated, or even welded together, causing the load of the motor and other phases to run out of phase.