Analysis and optimization of key dimensions of co-axial dual-mechanical-port flux-switching permanent magnet machines for fuel-based extended range electric vehicles

In this paper, key dimensions of a co-axial dual-mechanical-port flux-switching permanent magnet (CADMP-FSPM) machine for fuel-based extended range electric vehicles (ER-EVs), including split ratio, stator/rotor pole arcs, rotor yoke thickness, etc., are analyzed and optimized. Firstly, the topologies and operation principles of an exampled 3-phase CADMP-FSPM are introduced briefly, in which an inner-rotor FSPM machine with 12-stator-slots/10-rotor-poles for high-speed generation and an outer-rotor FSPM machine with 12-stator-slots/22-rotor-poles for low-speed motoring are assembled co-axially. Then, the relationship between the key dimensions and electromagnetic performance, particularly for electromagnetic torque (power), of the CADMP-FSPM machine is studied by 2D-finite element analysis (FEA). Further, the reasonable matches of split ratio, rotor/stator pole arcs and rotor yoke are determined and the original CADMP-FSPM machine is optimized correspondingly. Finally, the static characteristics, including no-load PM flux-linkage, electro-motive-force (EMF), winding inductances, cogging torques and electromagnetic torques, of the original and optimized machines are compared by 2D-FEA. The results verify that the optimized CADMP-FSPM machine can exhibit improved torque characteristics than the original one, i.e., the torque ripples of the inner and outer machines can be reduced by 22.7% and 4.7%, respectively, and the average torque of the inner and outer machines can be increased by 0.43Nm and 2Nm, respectively.