The selection principle of contactor is as follows:
1. The voltage level of AC contactor should be the same as the load, and the type of contactor selected should be suitable for the load.
2. Check according to short-term dynamics and thermal stability. The three-phase short-circuit current of the line should not exceed the allowable dynamic and thermal stability of the contactor.
Flow, when using contactor to break short-circuit current, you should also check the breaking ability of contactor.
3. The rated voltage and current of the contactor attraction coil, the number of auxiliary contacts and the current capacity shall meet the wiring of the control loop.
Requirements. Considering the line length connected to the contactor control circuit, the contactor should be able to
85 ~ 1 10% rated voltage. If the line is too long, because the voltage drop is too large, the contactor coil may not reflect the closing instruction; Because the line capacitance is too large, it may not be able to execute the trip command.
4. Check the allowable operating frequency of the contactor according to the number of operations. If the operating frequency exceeds the specified value, the rated current
It should be doubled.