Method and apparatus for starting capacitive start, induction run and capacitive start, capacitive run electric motors

摘要

A solid state starting system for electric motors having main and auxiliary windings of the capacitor start induction run and capacitor start-capacitor run types uses a triac serially connected to the auxiliary winding. The system differentially measures the auxiliary winding voltage and provides a triac gate signal when in the START mode. When the auxiliary voltage reaches a calibratable cut-out voltage the triac is disabled until the auxiliary winding voltage decreases to a level below a calibratable cut-in voltage. The slope of the percent motor speed cut-out versus percent line voltage is calibratable to permit compensation for variations in line voltage. The triac can be directly driven or driven through an optically coupled interface having a triac output (OCI).