Why can one motor run at two rated voltages?

By 本站 2023/3/14 10:10:40

   In many motor applications, motors are required to operate in dual voltage mode, i.e. the same motor can operate normally at different rated voltages, such as 380/660V, 6 /10kV.

    The direct factor that determines the rated voltage of the motor is the insulation level of the winding and the current density of the conductor; some netizens have asked: for dual voltage motors, will the different voltages cause problems with the motor winding? In response to the user's question, we communicate with the essence of the normal operation of dual-voltage motor.

    Dual voltage motor, refers to the three-phase motor under different connections corresponding to different rated line voltage, when the motor with star connection, the rated voltage of the motor is higher; when the motor with triangle connection, its rated voltage is lower; but the two connections corresponding to the rated voltage must meet a certain number of relationships, that is, the rated line voltage of the star connection is the root of the rated line voltage of the triangle connection 3 times, at the same time, the triangle connection rated line current is the root of the star connection rated line current 3 times (on the relationship between voltage and current analysis under different connection methods, we have a specific article).

   The number of rated currents and rated voltages differ significantly between the two connections, but without adverse effects on the motor windings, the substance of which lies in the relationship between phase and line values of three-phase motors.
   The reliability of the insulation performance of the motor winding and the conductor current density depend on the phase voltage and phase current of the winding. When the delta connection method is adopted for the motor, only the line voltage of the input motor is changed. According to the voltage relationship under the two connection methods, when the motor adopts the star connection method and applies three times of the root of the rated line voltage of the delta connection method, The phase voltage and phase current of each phase of the motor winding have not changed; In the same way, when the delta connection method is used for the motor originally connected according to the star connection method, the voltage must be reduced according to the voltage relationship under the two connection methods to ensure the safety of the motor operation.

    According to the application practice of motors, dual-voltage motors are more used in three-phase asynchronous motors, that is, higher voltage is used in the starting process of motors, and low voltage triangular connection method is used in the normal operation of motors;  dual-voltage motors can meet the normal operation of different input power supply voltages (the connection method must match the voltage correctly).