Comparison of permanent magnet synchronous machine and permanent magnet flux-modulated machine in direct drive considering number of rotor poles

Direct drive permanent magnet (PM) motors have become a very attractive choice for electric vehicles. Generally, PM motors are divided into PM synchronous motors (PMSMs) and PM flux-modulated motors (PMFMMs). High torque density is the main requirement of direct drive motors, therefore, the structure of conventional PM motors is modified to boost the torque. Increasing the number of poles is a structural modification to achieve high torque density in PMSMs; however, a large number of poles affects motor characteristics such as power factor, flux weakening, losses, and efficiency. The other way to have high torque is to use PMFMMs, which have a high intrinsic torque density. This paper first compares the performance of PMSMs with different number of poles. Then the performance of PMFMMs and PMSMs are compared to show their differences. The performance of PMFMMs with different teeth modulators and magnetic gear ratios are predicted to show their effects upon its performance. The simulation results using finite elements method|finite element method (FEM) are presented, and finally, a PMFMM with 36 slots and 40 poles as case study is subjected to an experimental test and its results are compared with FEM.

The cover image is based on the article Comparison of permanent magnet synchronous machine and permanent magnet flux-modulated machine in direct drive considering number of rotor poles by Saeed Abareshi et al., https://doi.org/10.1049/elp2.12500.