Patent ID: 7911177

Claim:
An AC motor drive controller, comprising: an AC motor; an inverter; and an overmodulation PWM controller which controls a pulse width modulation voltage which is output from the inverter and which is to be applied to the AC motor, based on a result of comparison between a phase voltage instruction in which an amplitude exceeds a peak value of a triangular wave carrier and the triangular wave carrier, wherein the overmodulation PWM controller includes: a voltage instruction calculation unit which calculates a d axis voltage instruction and a q axis voltage instruction such that a d axis current and a q axis current which are detected correspond to the d axis current instruction and the q axis current instruction; a voltage amplitude calculator which calculates a voltage instruction amplitude from the d axis voltage instruction and the q axis voltage instruction calculated by the voltage instruction calculation unit; a voltage instruction correction unit which corrects the d axis voltage instruction and the q axis voltage instruction calculated by the voltage instruction calculation unit, such that a pulse width modulation voltage has a fundamental wave amplitude corresponding to the voltage instruction amplitude calculated by the voltage amplitude calculator; a voltage instruction conversion unit which converts the d axis voltage instruction and the q axis voltage instruction which are corrected by the voltage instruction correction unit into a phase voltage instruction and outputs the phase voltage instruction; and a synchronization PWM controller which controls a phase of the phase voltage instruction from the voltage instruction conversion unit and the triangular wave carrier, and wherein the voltage instruction correction unit corrects the d axis voltage instruction and the q axis voltage instruction calculated by the voltage instruction calculation unit in accordance with a synchronization number which is a ratio fc/fm between a frequency of the triangular wave carrier fc and a frequency of the phase voltage instruction fm.