1、When selecting a contactor, it is essential to consider the following factors based on the working environment:

① For controlling AC loads, choose AC contactors, and for DC loads, choose DC contactors.

② The rated operating current of the main contact should be greater than or equal to the current of the load circuit. It's important to note that the rated operating current of the contactor's main contact is the current value at which it can work normally under specified conditions (rated operating voltage, utilization category, operating frequency, etc.). This current value will change under different actual operating conditions.

③ The rated operating voltage of the main contact should be greater than or equal to the voltage of the load circuit.

④ The rated voltage of the coil should match the control circuit voltage.

2、Specific steps for selecting a contactor:

① Choose the type of contactor based on the type of load.

② Select the rated parameters of the contactor.Considering the controlled object and working parameters such as voltage, current, power, frequency, etc., determine the rated parameters of the contactor.

（1）For the coil voltage of the contactor, it's generally better to choose a slightly lower voltage to reduce the insulation requirements and enhance safety. When the control circuit is simple and uses a small number of electrical devices, you can directly choose a voltage of 380V or 220V. If the circuit is complex and uses more electrical devices (more than 5), you can choose a coil voltage of 36V or 110V to ensure safety. However, for convenience and reduced equipment, it's common to choose the voltage according to the actual grid voltage.

（2）For low-frequency operation of motors, such as compressors, pumps, fans, air conditioners, etc., the rated current of the contactor should be greater than the rated current of the load.

（3）For heavy-duty motors like machine tool main motors and lifting equipment, the rated current of the contactor should be greater than the rated current of the motor.

（4）For special-purpose motors that frequently operate in start-reverse states, choose the contactor based on the electrical life and starting current. Series like MSC, DILM are suitable.

（5）When controlling transformers with contactors, consider the size of the surge current. For example, for welding machines, you can select a contactor with a current rating of 2 times the rated current of the transformer, such as DILA, DILER, DILEEM, DILEM, etc.

（6）The rated current of the contactor refers to the maximum allowable current under long-term operation, with a duration ≤8 hours, and installed on an open control panel. If cooling conditions are poor, choose a contactor with a rated current 1.1-1.2 times the rated current of the load.

（7）Select the quantity and type of contactors. The number and type of contacts should meet the requirements of the control circuit.

（8）For applications in solar energy, rail transportation, maritime and offshore, energy storage vehicles, infrastructure, DC grids, etc., you can choose DILDC series 1000VDC contactors with a maximum current of up to 600A.