Abstract: A multi-phase motor controller for controlling voltage and power expended by a multi-phase motor comprises a sensing stage for detecting power factor angle, a feedback amplifier stage for comparing the power factor angle with a desired power factor angle, and a control stage for controlling voltage and power expended by the multi-phase motor in accordance therewith. Other features of the motor controller include a current limiting circuit for limiting "in-rush" current during "start up" of the motor controller, a current trip circuit for implementing "instantaneous trip" and "timed trip" capabilities upon detection of corresponding "overload" conditions, and a phase-loss circuit for automatically disabling operation of the motor upon detection of "phase-loss". A further embodiment of the motor controller includes a lead network, connecting the feedback amplifier stage to the control stage, for enhancing the stability of operation of the motor controller.

Abstract: A three-phase shift network includes a single transistor which controls phase shift by introducing a variable resistance into the network as determined by a D.C. control signal supplied to the transistor. The three-phase signals generated from the phase shift network undergo pulse shaping and are subsequently introduced into an opto-coupled pulse amplifier. The amplifier drives large SCR devices, connected as a load.