Comparative Study of Four-Phase Flux Modulated Doubly-Salient Reluctance Motors With Different Winding Polarity Configurations

To reduce the torque ripple and radial vibration, the flux modulated doubly-salient reluctance motor (FMDRM) drives are investigated, where the conventional quasi square current excitation scheme is replaced by the novel dc-biased sinusoidal current excitation scheme with the guidance of the flux modulation principle. However, the existing investigations mainly focus on the three-phase FMDRM. To evaluate the performance of the four-phase FMDRM, this paper proposes a comparative study of the four-phase FMDRMs with different winding polarity configurations. The electromagnetic characteristics of the four-phase 8/6 FMDRMs with commonly utilized 4N4S and NSNS winding polarity configurations are investigated in detail. The magnetomotive force (MMF), winding inductance, phase back electromotive force (back-EMF), torque output capability, and torque ripple are analyzed and compared. In addition, the corresponding finite element analysis (FEA) results are carried out for motor performance comparison. The results show that, compared to the NSNS winding polarity, the 4N4S polarity can achieve a better overall torque performance in the steady-state. However, the NSNS polarity can achieve better overload capacity.