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 released instantaneously when the DC is disconnected, and a high-energy arc is generated at the breaking point. Therefore, the DC contactor is required to have a certain arc extinguishing function. Medium/large-capacity DC contactors often adopt a single-break point planar layout overall structure, which is characterized by a long arc distance during breaking and an arc extinguishing grid inside the arc extinguishing cover. The small-capacity DC contactor adopts a three-dimensional arrangement structure with double break points.
Pay attention to the following points when choosing 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. Rated coil voltage. When the circuit is simple and uses less electrical appliances, 220V or 380V can be selected; when the circuit is complicated, more electrical appliances are used, or where it is not 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 model with the rated current one level higher should be selected. Otherwise, the contacts will be severely heated, or even welded together, causing the motor and other loads to run without phase.