Steady state performance analysis of multi-phase induction motor with non-sinusoidal supply

Abstract

Electromagnetic performance analysis is the very foundation for electric machine design optimization. Thus, the research on performance evaluation methods for multi-phase induction machines with non-sinusoidal supply is of great theoretical value and practical importance, as such process is much more complicated than traditional methods developed for three-phase induction machines. The fundamental and third harmonic equivalent circuits are employed as design tools for induction machines supplied by non-sinusoidal voltages with third harmonic injection. Considering that the air-gap flux density is asymmetrical, extended distributed magnetic circuit approach(EDMCA) is used to calculate the fundamental and third harmonic EMFs. The performance of the induction machine is finally determined by calculating quantities such as the fundamental and third harmonic currents in steady state through 3 layers of iterations. Particularly, the inner-layer iteration that calculates the air-gap magnetic flux and the middle-layer iteration that determines the magnetizing current is quite different from the traditional performance analysis approach for three-phase induction machines. The proposed method is applied to a prototype fifteen-phase induction machine with non-sinusoidal supply. Close agreement between the calculated and experimental results at various working conditions indicates the high accuracy of the proposed method.