A modified partitioned-stator flux-switching permanent magnet machine for enhancing torque-density in electric vehicle powertrains

This study proposes a modified partitioned-stator flux-switching permanent magnet (PS-FSPM) machine and reduces the permanent magnet usage in conventional PS-FSPM machines. To achieve this goal, the stators of the conventional PS-FSPM with outer-armature/inner-PM (OA/IPM PS-FSPM) structure are swapped to realise a PS-FSPM with outer-PM/inner-armature (OPM/IA PS-FSPM) design. The machine topology along with the operating principles are described in detail, and an analytical airgap permeance model is introduced for the proposed machine. The number of rotor modules, the widths of the magnets and rotor modules, as well as the split ratio (SR), are optimised through sensitivity analysis to achieve higher torque density and reduced torque ripple, compared with the conventional structure. Moreover, a flux barrier in the exterior surface of the outer stator is adopted to improve the proposed structure to reach a higher flux concentration in the airgap and reduce iron volume consumption. The thermal analysis results using the computational fluid dynamics modelling indicate that the temperatures of both insulation and permanent magnets remain within specified operating limits. Finally, apart from the finite element analysis (FEA), an experimental study is performed to evaluate the feasibility of fabricating a machine equipped with a high number of rotor modular teeth.