Patent ID: 7148651
Filing Date: 2006-12-12
Classification: H02M,H02P

Abstract:
1. An apparatus for controlling an AC motor comprising: a three-phase PWM inverter which receives a DC current, outputs a three-phase AC current and drives the AC motor acting as a load; a current detection unit estimating a current of the AC motor from the DC current inputted to said three-phase PWM inverter; and PWM calculation unit inputting a three-phase voltage command value and a carrier frequency and outputting a drive signal to a switching element of said three-phase PWM inverter, said control apparatus further comprising a carrier frequency changing unit inputting the three-phase voltage command value and outputting the carrier frequency, wherein, when a difference between a pulse width of PWM pulse signals having an intermediate phase of the three-phase voltage command value and a pulse width of the PWM pulse signals having a maximum phase thereof, or a difference between the pulse width of the PWM pulse signals having the intermediate phase and a pulse width of the PWM pulse signals having a minimum phase thereof is shorter than a predetermined current detection minimum time, the carrier frequency is reduced by said carrier frequency changing unit.