Patent ID: 8502493

Claim:
A control device for an alternating-current motor to which a voltage controlled by an inverter is applied, the control device comprising: a pulse width modulation control unit for generating a control command for said inverter by means of pulse width modulation control performed based on a comparison between a voltage command signal of a sinusoidal wave and a carrier signal, said voltage command signal being for operating said alternating-current motor in accordance with an operating command; and a mode-switching determining unit for instructing which control mode of an overmodulation mode and a sinusoidal wave modulation mode is to be employed for said pulse width modulation control performed by said pulse width modulation control unit, in said overmodulation mode, said voltage command signal having an amplitude larger than that of said carrier signal, in said sinusoidal wave modulation mode, said voltage command signal having an amplitude equal to or smaller than that of said carrier signal, said inverter including a power semiconductor switching element to be turned on/off in accordance with said control command from said pulse width modulation control unit, wherein when said mode-switching determining unit instructs to switch the control modes between said overmodulation mode and said sinusoidal wave modulation mode, said pulse width modulation control unit corrects the amplitude of said voltage command signal based on a state of a power conversion operation performed by said inverter, so as to suppress a change in an influence of dead time over the voltage applied to said alternating-current motor upon switching the control modes.