Analysis of Radial Force, Vibration, and Noise in Low-Speed, High-Torque Density Spoke-Type PMSMs with Symmetric and Asymmetric Assisted Poles Designs

This article investigates the radial electromagnetic force, vibration, and noise phenomenon in a low-speed, high-torque density spoke-type permanent magnet synchronous machine (ST-PMSM) designed with assisted poles having symmetric and asymmetric topologies. Firstly, an analytical expression for the machine radial electromagnetic force (REMF) is derived to quickly estimate the REMF characteristics for the ST-PMSM with assisted poles having symmetric and asymmetric topologies. The 2D-Fourier decomposition method is applied to investigate the radial electromagnetic force harmonics (REMFHs). Secondly, Finite element (FE) models are designed for the machine structural analysis. Subsequently, the FE models and modal analysis are explored for different design cases of the analyzed machine. Lastly, vibration and noise behavior are investigated using an FE approach for the machine designs under symmetric and asymmetric assisted poles topologies. The findings indicate an increase in the richness of REMFHs, alongside a decrease in both the fundamental frequency and the lowest nonzero order of REMF, attributed to the presence of asymmetric assisted poles. Consequently, it is investigated that while considering the vibration and noise response in ST-PMSMs designed with asymmetric assisted poles topologies, it is essential to thoroughly account for induced nonzero low-order harmonics and their optimization for better vibration and noise performance.