Induction motor stator voltage controller - matches applied voltage to torque demand on rotor using discriminator to check frequency of coupled HF generator

摘要

The applied stator voltage is adjusted in response to changing load demand so that, at low loads, motor iron and copper losses are reduced. A typical application is to lifting machines. Rotor speed is given by a coupled h.f. generator whose output frequency is checked by a discriminator. Falling frequency indicates rising slip, and hence torque, and a slip proportional d.c. voltage is fed to an oscillator. The latter controls the triggering of a triac in the motor supply, thus regulating the voltage applied to the motor winding to match the torque demand.