Selection mode of DC contactor:

1. Selection of coil rated voltage: the rated voltage of coil is necessarily equal to the rated voltage of main contact. When the circuit is simple there are few electrical appliances, 380V 220V voltage can be directly selected. If the circuit is complex the electrical appliances are used for more than 5h, the coil with voltage of 24 V, 48 V 110 V (36 V, 110 V, 127 V in 1964 international regulations) can be used.

2. Choose the type of DC contactor: the type of DC contactor should be selected according to the type of load current the light weight of load, that is, AC load DC load, light load, general load heavy load.

3. Rated voltage of main contact: the voltage marked on the name plate of the contactor refers to the rated voltage that the main contact can bear, the voltage of the attractive coil. When in use, the rated voltage of the main contact of the contactor shall be less than the rated voltage of the load.

4. Rated current of main contact of DC contactor: the rated current of main contact of DC contactor can be calculated according to empirical formula, in main contact ≥ PN motor / (1 ~ 1.4) UN motor. If the motor controlled by DC contactor starts, stops reverses frequently, the rated current of main contact of DC contactor is generally reduced to one level for use.

5. Selection of operating frequency: the operating frequency refers to the frequency of making breaking the contactor per hour. When the on-off current is large the on-off frequency is too high, the contact will be seriously overheated even fused. If the operating frequency exceeds the specified value, the DC contactor with a higher rated current shall be selected.