AQ: How is Vector Control improving motor output torque capability?
1: Torque boost: this function is the variable speed drive increases output voltage (mainly in low frequency) to compensate the torque loss due to voltage drop in the stator resistance, thereby improving the motor output torque.
2: Improve the motor insufficient output torque in low speed
“Vector control” can make the motor output torque at low speeds, such as (without speed sensor) 1Hz (for 4-pole motor, the speed is about 30r/min), same as the torque output at 50Hz power supply (maximum is approx 150% of rated torque).
For the V/F control variable speed drive, the motor voltage increases relatively as the motor speed decreases, which will result in lack of excitation, and make the motor can not get sufficient rotational force. To compensate this deficiency, the variable speed drive needs to raise voltage to compensate for the voltage drop in motor speed decreases. This feature called “torque boost”.
Torque boost function is to improve the variable speed drive output voltage. However, even if the drive increases voltage, the motor torque and current does not increase corresponding. Because the motor includes the torque and other components (such as the excitation) which generated by the motor.
“Vector Control” allocates the motor current value to determine the motor torque current component and other current component (such as the excitation component) values.
