Study of Winding Structure to Reduce Harmonic Currents in Dual Three-Phase Motor

Abstract

Dual three-phase motors have the problem of a large generation of harmonic currents while driving due to small inductance for certain harmonics. The purpose of this paper is to theoretically clarify the effect of the winding structure of dual three-phase motors on harmonic currents. Analytical calculations considering the spatial harmonics of the magnetomotive force are used to formulate the inductance that depends on the winding structure and the harmonic order. The validity of the formulated theoretical expression of the inductance is confirmed by finite element analysis. In addition, drive simulations of the coil pitch 5/6 dual 3-phase motor and the coil pitch 1 dual 3-phase motor are performed, and it is found that the magnitude of the generated harmonic currents can be explained using the formulated inductance values. In conclusion, it is found that dual three-phase motors with large winding factors for fifth and seventh order spatial harmonics can reduce the harmonic currents.