MOTOR DRIVE PWM RECTIFIER HAVING MODULATION SCHEME SELECTOR

摘要

A motor drive PWM rectifier includes a control section which generates the PWM signal in accordance with either a three-phase modulation scheme or a two-phase modulation scheme in which a PWM voltage command for one phase selected from among three phases each constituting the PWM voltage command in the three-phase modulation scheme is set and held at a level equivalent to a maximum value or minimum value of the PWM carrier and in which a PWM voltage command for the other two phases created by also applying an offset, required to achieve the setting, to the other two phases, a detecting section which detects three-phase AC current and outputs a detected current value, and a selecting section which selects the two-phase modulation scheme when the detected current value is larger than a first threshold value but smaller than a second threshold value, and otherwise selects the three-phase modulation scheme.