This invention controls a three-phase AC induction motor (705) by a modified PWM approach. A digital signal processor (710) receives the analog signal (700) which instantaneously contains the ripple component not removed by capacitor 703. This signal is applied to a first analog-to-digital conversion input (ADC0). A reference voltage (701), used to input the control speed, is supplied to a second analog-to-digital conversion input (ADC1). A third analog-to-digital conversion input (ADC3) receives an instantaneous speed/position feedback signal (702) from speed/position feedback sensor (708). The digital signal processor 710 internally calculates the instantaneous duty ratios required from an analog-to-digital conversion of the input ripple signal and supplies the required inverter PWM drive at the event manager outputs (704). These event manager outputs (704) are applied to the gates of N-channel MOSFET transistors 100 to 102 and 110 to 112 to control the three-phase drive to motor 705. These inverter inputs thus driven become part of a closed loop from the speed/position feedback signal (702) cancels out the effects of the ripple component of the line voltage.
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