Investigation of Contributions of Stator Slot PMs in Multi-Tooth Dual-PM Machines

This paper investigates the contributions of stator slot permanent magnets (PMs) in multi-tooth dual-PM machines with different stator/rotor pole number combinations. Different stator configurations with and without stator slot PMs are analyzed and compared considering different rotor pole numbers and split tooth numbers. It is found by analytical technique and finite element method that removing stator slot PMs and employing non-uniformly distributed split teeth can reduce the pole-pair number of fundamental components of PM MMF and modulator permeance, thereby effectively enriching working harmonics. Consequently, after removing stator slot PMs, the average torque is not sacrificed and may even be improved while the PM volume is reduced. The torque change due to removing stator slot PMs depends on the stator/rotor pole number combinations, and the stator/rotor pole number combinations which can achieve significant torque improvement are identified. A guideline for selecting appropriate stator configuration and stator/rotor pole number combination is proposed for improving average torque and PM utilization and reducing manufacturing difficulty. Four prototypes are built and experimented to validate the FEA results and analyses.