Line Synchronised Control Pulses for Three Phase Induction Motor AC-AC Drive Using Analog Phase Lock Loop Technique

Abstract

Technique used in this research is to obtain high operating efficiency of three phase induction motor (IM). To
achieve this emphasis is given on minimizing the core losses by controlling the magnetizing current of three
phase induction motor so that total power loss gets reduced and thereby efficiency of IM gets improved.
Improvement in power factor of IM causes reduction in magnetizing current. Novel topology used in this work
also aimed at controlling the speed and improvement of power factor separately. To improve the performance
and to obtain the expected results of induction motor at any change in operating frequency ,work is focused on
obtaining line synchronised extinction angle (β) and Pulse Width Modulation(PWM) control pulses. Both these
controls are line synchronized using analog phase lock loop(PLL) technique so that switching frequency of
PWM pulses remains synchronized with the supply frequency for any small change in input supply frequency,
so that separate smooth control over wide range of speed and improvement in power factor both are achieved.
Switching off supply at extinction angle β gives improvement in power factor and variation in duty ratio of
PWM pulses controls the speed of three phase induction motor. Hardware and simulation results are obtained by
using only four switches , which simplifies the circuit and makes it cost effective. The hardware model for line
synchronised control pulses using analog PLL technique is shown. PLL has many applications.