APPARATUS AND METHOD FOR CONTROLLING INDUCTION MOTOR

摘要

A controller of an induction motor which has an inverter which converts a DC voltage into a variable-frequency variable-voltage AC by pulse width modulation control and the controller which controls the output voltage of the inverter with a percentage modulation which is obtained from the voltage component instructions corresponding to an excitation current component and a torque component and calculated in accordance with an excitation current component instruction and a torque current component instruction, in the primary current of an induction motor which is driven by the inverter. In the controller, a means which detects the torque current component from the induction motor primary current, a means which corrects the torque current component instruction in accordance with the deviation between the detected torque current component and the instructed value, a means which corrects the output frequency of the inverter in accordance with the corrected torque current component instruction and a means which limits the percentage modulation to be not less than a required value or under optional condition. With this construction, good vector control of the induction motor can be performed continuously from a low rotational speed region to a high rotational speed region in which the voltage instruction value exceeds the maximum output voltage of the inverter which is determined by the DC voltage (a PWM pulse mode is in a one-pulse region).