1. Select the type of DC relay
The type of DC relay should be selected according to the type of load current and the weight of the load, that is, AC load or DC load, light load, general load or heavy load.

2. Rated current of DC relay main contacts
The rated current of the main contact of the DC contactor can be calculated according to the empirical formula. The main contact of IN ≥ PN motor/(1~1.4) UN motor If the motor controlled by the DC contactor starts, brakes or reverses frequently, the main contact of the relay is generally used. The rated current of the head is reduced by one stage.
3. Rated voltage of main contacts
The voltage marked on the nameplate of the relay refers to the rated voltage that the main contact can withstand, not the voltage of the attracting coil. The rated voltage of the main contact of the contactor should not be less than the rated voltage of the load during use.
4. Choice of operating frequency
The operating frequency refers to the number of times the contactor is turned on and off per hour. When the on-off current is large and the on-off frequency is too high, the contacts will be seriously overheated and even welded. If the operating frequency exceeds the specified value, the rated current should be selected. Class 1 DC contactor.