Variable frequency motor using vector inverter control has several advantages
Torque boost
This function increases the output voltage of the inverter (mainly at low frequencies) to compensate for the output torque loss caused by the voltage drop on the stator resistance, thereby improving the output torque of the motor. Technology to improve the low speed output torque of the motor
Using vector control, the output torque of the motor at a low speed, such as (without a speed sensor)1Hz (for a 4-pole motor, its speed is about 30r/min) can reach the output torque of the motor at 50Hz (at most about 150% of the rated torque).
For conventional V/F control, the voltage drop of the motor increases with the decrease of the motor speed, which causes the motor to not get enough rotating force due to insufficient excitation. In order to compensate for this deficiency, the inverter needs to compensate for the voltage drop caused by the motor speed reduction by increasing the voltage. This function of the inverter is called “torque boost” (*1).
The torque boost function is to increase the output voltage of the inverter. However, even if the output voltage is increased by a lot, the motor torque does not increase correspondingly with its current. Because the motor current contains the torque component generated by the motor and other components (such as the excitation component).
Vector control distributes the current value of the motor to determine the value of the current component of the motor that produces torque and other current components (such as the excitation component).
Vector control can be optimally compensated by responding to the voltage drop at the motor end, allowing the motor to produce large torques without increasing the current. This function is also effective for improving the temperature rise of the motor at low speed.