a drive system for an automatic washer or dryer having a rotatable drum about a horizontal axis . an induction motor drives the drum and is connected to and disconnected from a source of alternating voltage by a microprocessor to control the speed of the motor . the microprocessor senses the zero crossing of the alternating voltage and the zero crossing of alternating current flowing in the motor to determine the time to connect the motor to the alternating voltage . the microprocessor analyzes successive readings of the motor &# 39 ; s back emf to detect undesirable load distributions and effect redistribution .