(1) Select the type of contactor:
Select according to the type of load current in the circuit. AC contactor should be used for AC load. DC contactor should be used for DC load. If the control system is mainly AC load, the capacity of DC motor or DC load is small, AC contactor can also be used for control, but the contact is rated. The current should be chosen to be larger.
(2) Select the rated voltage of the contactor main contact:
Should be equal to or greater than the rated voltage of the load.
(3) Select the rated current of the contactor main contact:
The rated current of the main contact of the selected contactor shall not be less than the rated current of the load circuit. It can also be selected according to the maximum power of the motor being controlled. If the contactor is used to control the frequent start, reverse or reverse braking of the motor, the rated current of the main contact of the contactor should be reduced, generally one level can be reduced.
(4) Determine the working voltage of the attracting coil and the auxiliary contact capacity according to the requirements of the control circuit:
If the control circuit is relatively simple and the number of contactors used is small, the rated voltage of the AC contactor coil is generally 380V or 220V. If the control circuit is more complicated, there are more electrical appliances used. For safety reasons, the rated voltage of the coil can be selected lower. In this case, a control transformer needs to be added. The rated voltage of the DC contactor coil shall be determined by the condition of the control loop. For a series of contactors of the same capacity class, the rated voltage of the coil is several, and the rated voltage of the coil can be selected to be the same as the voltage of the DC control circuit. The coil of the DC contactor is a DC voltage, and the coil of the AC contactor is generally an AC voltage. Sometimes in order to increase the maximum operating frequency of the contactor, the AC contactor also uses a DC coil. If the DC voltage coil is applied with an AC voltage, the resistance is too large and the current is too small, so the contactor often does not pick up. If the AC voltage is applied to the coil of the AC voltage, the resistance is too small and the current is too large, which will burn the coil.
Metal Clad Sockets,Timer Plug Socket,2 Gang Socket,Silver Plug Sockets
Guangdong Jinli Electrical Appliance Co., Ltd , https://www.sokelectric.com