Electronic starting circuit for an alternating current motor

摘要

A circuit is provided for controlling energization of the start winding of an alternating current motor whose shaft is divided into a number of angular segments equal to the number of poles of the motor. A shaft pulse is generated each time one of the angular segments rotates past a predetermined point. A line pulse is generated for each half cycle of line voltage. The shaft pulses are multiplied by the denominator of a selected trip-out ratio while the line pulses are multiplied by the numerator of the trip-out ratio. The multiplied shaft and line pulses are provided to an up/down counter which counts the shaft pulses down and the line pulses up. During the counter overflow condition, the circuit connects the start winding to the line voltage source. During the counter underflow condition, the circuit disconnects the start winding from the line voltage source.