Soft Starting Comparison of Single-Phase Capacitor Start Capacitor Run Induction Machine Between Motoring and Generating Operation Using Asynchronous PWM AC Chopper

Abstract

This paper presents a soft starting comparison of a single-phase, 1 hp, 220 V, 4.8 A, four-pole capacitor-start capacitor-run induction machine between motoring and generating mode of operation when connected to a grid using single-phase PWM AC chopper. An asynchronous PWM strategy is used for controlling the machine voltage with the AC chopper during soft start with a reason of simplicity. The PWM AC chopper offers some advantages over a conventional ac voltage controller using phase control in terms of harmonic reduction and linear relationship between fundamental voltage and duty ratio. The comparison of waveforms of starting currents, voltages, instantaneous power under direct on line and soft connection conditions is given when the machine operates as a generator and a motor during startup. According to experimental results, it is found that when starting the connection, the generator offers lower starting current compared to the motor and the soft starter can reduce starting current to one fifth when compared to direct on line start.