1. Select the type of DC contactor The type of DC contactor should be selected according to the type of load current and the light weight of the load, whether it is AC load or DC load, light load, general load or heavy load.
2. DC contactor main contact rated current DC contactor main contact rated current can be calculated according to the empirical formula IN main contact ≥ PN motor / (1 ~ 1.4) UN motor if DC contactor controlled motor start, brake or Frequent reversal, generally reduce the rated current of the contactor main contact to one level.
3. Rated voltage of the main contact The voltage marked on the nameplate of the contactor refers to the rated voltage that the main contact can withstand. It is 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 when in use.
4. The operating frequency of the operating frequency refers to the number of times the contactor is turned on and off every hour. When the on-off current is large and the switching frequency is too high, the contact will be seriously overheated or even welded. If the operating frequency exceeds the specified value, Use a DC contactor with a rated current of one level.
5. The rated voltage of the coil rated voltage is not necessarily equal to the rated voltage of the main contact. When the line is simple and the electric appliance is used less, the voltage of 380V or 220V can be directly selected. If the line is complicated, the electric appliance is more than 5h, and 24V, 48V or 110V can be used. Voltage (36V, 110V, or 127V internationally specified in 1964).
The working principle of the DC contactor is as follows
When the contactor coil is energized, the coil current generates a magnetic field, so that the static iron core generates electromagnetic attraction to attract the moving iron core, and drives the contact action: the normally closed contact is opened, and the normally open contact is closed, and the two are interlocked. When the coil is de-energized, the electromagnetic attraction disappears and the armature is released by the release spring, which restores the contact: the normally open contact opens and the normally closed contact closes.