Abstract: Accurate induction motor speed control is accomplished by controlling the duty cycle of operation of high voltage switches which in turn drive the motor windings. For two phase operation logic circuitry generates two bipolar variable duty cycle waveforms with the off-time of each waveform being adjustable to vary motor speed. For single phase operation a single control waveform is generated. An initialization circuit is also provided and forms a part of the circuitry for converting the input AC line voltage to a DC voltage level useable by the high voltage switches. This initialization circuit controls the charging of capacitors of the AC to DC converter and provides efficient power transfer.

Abstract: An electronic controller having a pair of sequential outputs for energizing a line voltage AC load or loads in the manner of a single pole double throw (SPDT) switch. The controller comprises a pair of mutually exclusively operated timers, each having an adjustable timing circuit associated therewith. The output from each timer operates a triac which couples power to the load. A termination circuit including a pair of flip-flops and an operating switch is associated with the timers for terminating at any time the present state of the controller and commencing the other state without introducing a timing error.