Control of stopping of single phase asynchronous capacitor motor, uses measurement of phase shift between voltage and current in motor to activate circuit interruption device

摘要

The stopping circuit measures (3) phase shift between voltage (U) and current (I1 or I2) traversing the principal motor windings (L1 or L2), and activates a circuit (4) that cuts supply to the motor when phase shift is below a set level. The phase shift detector uses current zero-crossing detection (6,7), using a comparator (CP1 or CP2) to transform voltage over a shunt into a square wave.