Patent ID: 7068526

Claim:
A PWM inverter having PWM pulse output means for outputting a PWM pulse signal upon magnitude comparison of phase voltage commands with a carrier wave of a triangular or a saw-tooth waveform, wherein: a maximum phase whose absolute value is a maximum among the absolute value of the phase voltage commands is selected; in a first case where the phase voltage command of said maximum phase is larger than a maximum value of said carrier wave, a difference obtained from a first subtraction of said maximum value of said carrier wave from phase voltage command of said maximum phase is set as a first differential; said first differential is subtracted from said phase voltage commands of said respective phases in a second subtraction; and the first and second subtraction results are set as phase output voltage commands of said respective phases; in a second case where said the phase voltage commands of said maximum phase is smaller than a minimum value of said carrier wave, a difference obtained from a third subtraction of said minimum value of said carrier wave from phase voltage command of said maximum phase is set as a second differential; said second differential is subtracted from said phase voltage commands of said respective phases in a fourth subtraction; and the third and fourth subtraction results are set as phase output voltage commands of said respective phases; and in a case other than said first and second cases, phase voltage commands are set as phase output voltage commands; the PWM inverter characterized by comprising voltage command processing means for outputting said phase output voltage commands to said PWM pulse output means upon input of phase voltage commands.