The selection of AC contactor shall be based on the actual working conditions and meet the requirements of controlled equipment. The main selection basis is: rated working voltage and current of main contact, rated voltage of suction coil, total number and type of auxiliary contact, load power, use category, control mode, operating frequency working life, installation mode and safety of controlled equipment Installation dimension and its rationality. The manufacturer of AC contactor has concluded that the selection principle of AC contactor is as follows:

    1) selection of rated voltage of main contact: the voltage of AC contactor shall be more than or equal to the voltage of controlled line.

    2) selection of rated current of main contact: the rated current of main contact of AC contactor shall exceed or equal to the rated current of load. That is to say, the calculated current of the load is not greater than the rated working current of the AC contactor. The making current of the AC contactor exceeds the starting current of the load.

    3) selection of breaking current: the breaking current shall exceed that required during the load operation period. For the load with long starting time, the breaking current shall exceed that required during the load operation period.

    4) selection of calculation current of load: considering the actual working environment and load, for the load with long starting time, the calculation current of load shall consider the actual working environment and load.

    5) selection of rated voltage of AC contactor suction coil: when the control circuit is simple and the use of electrical appliances is young, so as to save transformer, 380 or 220 voltage can be selected immediately; when the control circuit is complex, 36V or 110V voltage coil can be selected to ensure safety.

    6) selection of total number and type of contacts of AC contactor: it shall also meet the requirements of control circuit.

    7) selection of operation frequency: check the allowable operation frequency of AC contactor according to the operation frequency. If the operating frequency exceeds the standard value, the rated current selection shall be increased.

    8) selection of main parameters of overcurrent protection components: main parameters of AC contactor shall be selected in coordination with each other. For example: the making and breaking current of AC contactor shall be lower than the overcurrent protection current of the circuit breaker, so that the circuit breaker can maintain the AC contactor; the rated current of the fuse shall exceed the rated current of the line.

    9) selection of breaking capacity: breaking capacity refers to the expected current that AC contactor can make and break under the given voltage under the required condition. The breaking capacity of different types of AC contactors is different. According to the fact that when the AC contactors break the short-circuit current, there can be no fusion welding, flashover, excessive wear, etc.