When aforementioned fundamental vector changes in null vector among

摘要

PROBLEM TO BE SOLVED: To easily reduce the number of switching times in a carrier period of switching elements of each phase, in PWM control by asymmetrical type spatial vector modulation.;SOLUTION: A controller controls through PWM a voltage three-phase inverter by the spatial vector modulation, wherein the switching elements formed as a pair in each phase are constituted as a bridge type, and the inverter converts a supply voltage of dc power supply into an alternating current by the switching elements of each phase. In the controller, a switching reducing circuit 30 is provided which does not forcedly turn on or off the switching element of the phase to be switched, when a fundamental vector in the spatial vector modulation changes into zero vector where its magnitude becomes zero, with regard to a PWM pulse which is modulated through a spatial vector according to switching patterns of the switching elements of each phase.;COPYRIGHT: (C)2008,JPO&INPIT