Purpose − The purpose of this paper is to propose a new outer-rotor permanent-magnet flux-switching machine for in-wheel electric vehicle propulsion. Thepaper documents both the design procedure and performance investigation of thisnovel machine. Design/methodology/approach − The topology and preliminary sizingequations of the outer-rotor permanent-magnet flux-switching machine areintroduced. Both the number and width of rotor poles are then optimized usingcomprehensive two-dimensional FEA. The machine losses are particularlyinvestigated by transient FEA for the optimal design. Findings − A outer-rotorpermanent-magnet flux-switching machine, with 12 stator poles and 22 rotorpoles, is most suitable for the proposed application. The analytical sizingequations are quite efficient with a suitable level of accuracy for preliminarydesign. The optimal rotor pole width from the FEA results is nearly 1.3 times ofthe original one. The efficiency of the proposed machine under rated load isrelatively low, nearly 85%, as a result of significant eddy current losses inthe permanent magnets, which can be effectively suppressed by implementingsegmentation. The predicted outstanding performance implies that by adoptingmagnet segmentation the proposed machine is a leading contender for directelectric vehicle drives. Research limitations/implications − The end effects,which could be considerable in the machine with relatively short axial length,are neglected during the study. In addition, due to the high current density anddeep slot, proximity losses in the winding which is not issued in this researchcould be significant. All the limitations mentioned above could bringcorresponding errors to the results. Although the research is concentrated onthe application of electric vehicle drive, the techniques can be potentiallyemployed for other applications. Practical implications − The practicalimplementation of such a machine is confronted with several mechanical hurdles,especially the thermal issues which can be addressed by implementing innovativecooling system. Originality/value − The outer-rotor permanent-magnet flux-switching machines so far have not been addressed yet. This research providesdesigners with the technical background and another alternative for electricvehicle
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