Asymmetric Winding Structure for Concentrated Winding Permanent Magnet Motors to Achieve a Low Torque Ripple and High Slot Fill Factor

Abstract

In this paper, we propose asymmetric winding structure to achieve a low torque ripple and high slot fill factor. Existing methods developed for this purpose improve the winding factors of harmonics and the slot fill factor by ensuring that the winding arrangement and number of turns for each coil are asymmetric. In contrast, an asymmetric winding structure generally lowers the symmetry of the magnetomotive force of the stator and generates electromagnetic excitation forces with lower spacial order modes, resulting in increased vibration. Therefore, in this study, we aim to improve the winding factor and the slot fill factor by changing the winding arrangement and the number of turns while considering the symmetry of the electromagnetic field. First, the working principle of techniques for improving the characteristics of the proposed winding structure are discussed. Thereafter, the results of magnetic field analysis and the verification of the said improvements to the asymmetric prototype, along with the effects, are presented.