Influences of Stator Teeth Number on PM Coupling Levels of Co-Axial Dual-Mechanical-Port Flux-Switching PM Machines

In this paper, the influence of stator teeth number on permanent magnet (PM) field couplings of co-axial dual-mechanical-port flux-switching permanent magnet (CADMP-FSPM) machines for fuel-based extended-range electric vehicles is investigated. First, the relationships between the inner and outer stator teeth numbers are analytically evaluated. Second, four typical structures, including 5/6-12/22, 10/12-12/22, 5/6-18/42, and 10/12-18/42, of CADMP-FSPM machines are analyzed, and three key stator teeth types, namely, series, parallel, and independent teeth, are defined. Third, the PM field coupling levels of four structures, featured by PM field distributions and air-gap flux densities, are compared with stator teeth matchings. The results indicate that the 10/12-12/22 structure exhibits the lowest PM field coupling and the prior open-circuit performance. Furthermore, the PM field coupling effects on the inner and outer air-gap flux densities are analyzed. Finally, a prototyped 10/12-12/22 CADMP-FSPM machine is designed, optimized, and manufactured, and the experimental results verify that the PM field coupling level of the prototype is negligible, which agrees well with the finite-element predictions and the proposed matching criteria for the selection of the inner and outer stator teeth numbers of CADMP-FSPM machines.