Abstract: An electronic starting circuit for a single-phase electric motor is disclosed in which the motor has a first, and possibly a second, main winding and has an auxiliary winding used for starting. The voltage across the auxiliary winding increases as the motor speed accelerates and is used as a sensing signal. This signal is applied through an amplifier to a peak detector which determines the peak DC output and compares it with a reference voltage. When the reference voltage is the larger, then an auxiliary switch connected in series with the motor auxiliary winding is closed for starting of the motor. When the peak DC output voltage from the peak detector exceeds the reference voltage, the auxiliary switch is opened. Instant reversing of the motor is possible by discharging a capacitor in the peak detector at the time of reversal so as to re-energize the auxiliary winding. The circuit also operates on a two-speed motor.

Abstract: A circuit is disclosed for controlling operation of a single phase electric motor to obtain maximum efficiency over a complete range of load conditions for the motor. Under conditions of less than full load, single phase motors waste electricity when full AC power is continuously supplied thereto. At less than full load, the torque requirements of a motor are reduced and therefore the flux can be reduced, thus increasing the efficiency. An electrical switch, in electrical series with the motor, is used to control the motor flux by reducing the "on time" of the switch and thereby decreasing the voltage applied to the motor. The ratio of auxiliary winding voltage to main winding voltage is the parameter used in the instant invention to provide a measure of the load condition of the motor and thus operate the electrical switch.