Power Quality Indices of Six–Phase Asynchronous Motor Drive Prototype

Abstract

The multiphase electric drives are of interest in fields where reliability and higher torque are guiding criteria, especially important in electric traction. In this paper a six–phased asynchronous machine electric drive for traction systems is analyzed for power quality indices. The driving factors for analysis of viability of such systems are dynamic properties and efficiency. Efficiency is a complex measure for electric systems, such as the asynchronous motor is designed to work with perfectly sinusoidal waveforms of voltages and currents, an impossible fact for variable speed and torque mechanical loads, where power converters are necessary to drive the motor. The part of drive efficiency that will be the center of this study is the power quality indices of the designed prototype multiphase electric drive. Specifically, how much distortion is to be expected in a variable speed drive comprised of six–phased asynchronous motor with scalar control, and how will it affect the active power that drives the load. The tools to determining the harmonic distortion and impact on the power quality, and subsequently on energy transfer efficiency, are also calculated numerically. The current standards that reflect this analysis are the IEEE Standards 1459–2010 and 519–2014, and the European equivalent IEC 61000–3–6, which all rely on the Fast Fourier Transform to decompose the waveform. The main limitation of this method is the applicability to steady signals. The real active power will then be deduced from the current and voltage harmonic distortions to determine the efficiency of power transfer to the electric drive.