Texas Instruments Corporation

Ronald A Mancini

Kevin J Dropps

Herbert A Thompson

Paul Ray Tomlinson

A solid state starting system for electric motors having main and start windings of the capacitor start, capacitor start-capacitor run and split phase types uses a triac serially connected to the start winding. The system turns on the triac upon energization of the motor from an at rest condition and measures the locked rotor value of either the main winding current for any of the above motor types or start winding voltage for the capacitor start, capacitor start-capacitor run motor types. The system stores that valve as a calibration value and then measures subsequent values and turns off the triac when the subsequent values reach a selected proportion of the calibration value. The system re-energizes the triac upon further subsequent measured values reaching a selected cut in value relative to the calibration value which is indicative of an overload or stall condition. The calibration value is retained for a given period of time following a loss of power to provide desired starting characteristics.

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Leo, IN, United States of America

Ronald A Mancini