1. Select the type of contactor from electrical ac contactor manufacturers

Alternating current contactor shall be used for AC load and DC contactor shall be used for DC load. If the control system is mainly AC motor, and DC motor or DC load capacity is relatively small, can also be used AC contactor control, but the contact current should be appropriate to choose a larger.

In three-phase AC circuit, the triple pole contactor is usually selected. In the single-phase and DC system, the poles or poles are used in parallel. When AC contactor is used in DC system, series connection can also be adopted to improve breaking capacity.

2. Select the rated voltage and rated current of contactor main contact

Generally, the rated voltage of contactor contacts shall be no less than the rated voltage of the load circuit. The rated current of the main contact shall not be lower than the rated current of the load circuit.

3. Determine the parameters of the control circuit and auxiliary circuit

The coil voltage of contactor shall be determined according to the voltage of the selected control circuit. Under normal circumstances, the use of alternating current control, when the operation is frequent, the choice of DC (220V, 110V) control.

The type and quantity of contactor auxiliary contactor can generally be determined within a certain range, according to the control requirements of the system, the number of normally open, normally closed and combined forms are determined, and the breaking and breaking capacity of auxiliary contact should be paid attention to. When the number of contacts and other rated parameters can not meet the system requirements, the contactor or relay can be added to enlarge the function.