1. Select the DC contactor type should be based on the severity of the load current and load type to choose, that is, or DC load AC load is light load, general load or a heavy load.
2. DC contactor main contacts rated current DC contactor main contacts rated current of main contacts ≥PN computing IN /(1~1.4)UN motor if the DC motor contactor control motor starting, braking or formula based on experience reverse frequently, generally the main contact current rating drop one to use.
3. The main contact contactor nameplate rated voltage if the voltage means the main contacts to withstand rated voltage not attract voltage coil, when using the main contact of the rated voltage should be not less than the rated voltage of the load.
4. Operating frequency is selected operating frequency refers to the contact number of times per hour off. When a large current and off-off frequency is too high, it will cause serious overheating of the contacts, even welding operating frequency exceeds a predetermined value, should selection of large DC contactor rated current level.
5. Coil voltage Coil voltage selection is not necessarily equal to the rated voltage of the main contact, when the line is simple, use of electrical appliances is low, it can be directly used voltage 380V or 220V, such as circuit complexity, use of electrical appliances more than 5h, available 24V, 48V or 110V Voltage (1964 international regulations for the 36V, 110V, or 127V) coils.