Motor control system

USRE29275E · kind E · reissue

Inventors

• Herbert L. Berman · Los Altos Hills, US
• Stanley N. Tenen · Brookline, US

Key dates

• Filing date: Jun 9, 1975
• Grant date: Jun 21, 1977
• Expiry date: Jun 9, 1995

Classification

• Technology area (CPC —): General

Abstract

A two-phase motor preferably of the induction or hysteresis type is driven from a variable frequency clock circuit by energizing the motor windings in phase quadrature over the frequency range. Speed control is provided by mechanically modulating a light emitting diode (LED) and photoresistor combination that couples to the clock circuit for determining its frequency of operation. The output of the clock circuit in turn couples to a two-phase generator that drives output bridges associated with the motor in phase quadrature. The photo resistor is characterized by a relatively .[.lone.]. .Iadd.low .Iaddend."off" (return to dark resistance) time constant that provides automatic braking when the speed control is set to zero. The system further includes a feedback circuit responsive to motor load fluctuations sensed by monitoring the DC current drawn by output bridge circuit means associated with the motor for controlling the frequency of operation of the clock circuit. This clock control permits the motor to come up to speed quite quickly with little or no synchronous slippage. If a load which would ordinarily stall the motor at the speed indicated by the mechanical control is .[.the …