Novel Asymmetric Rotor Pole Interior Permanent Magnet Machines

This thesis focuses on novel asymmetric rotor pole interior permanent magnet (AIPM) machines, with particular emphasis on enhanced torque density by utilizing magnetic-field-shifting (MFS) techniques for electric vehicle (EV) and hybrid EV (HEV) applications. The torque enhancement principle of MFS techniques is introduced by reducing current angle difference between maximum PM and reluctance torque components, thereby increasing maximum combined torque without extra PM usage. A novel categorization method of AIPM machine topologies is firstly proposed in terms of asymmetries and symmetricities of PM configuration and rotor core geometry to ease discussions of various AIPM rotor structures. To utilize MFS effect, five novel AIPM machine topologies with simple structures, mainly using asymmetric PMs and asymmetric rotor core structures, are developed and investigated in this thesis. The influences of key rotor geometrical parameters are investigated with particular emphasis on average torque. The electromagnetic performance, including open-circuit characteristics, torque and torque components, constant power speed range, and efficiency and losses, as well as mechanical robustness of the proposed AIPM machines are analysed and compared with those of conventional IPM machines using the same stator and total PM volume. The comparison confirms the significant torque enhancement by utilizing MFS effect and improvement of characteristics in the proposed AIPM machines. All proposed AIPM machines have been experimentally validated. Various proposed and typical existing AIPM machine topologies are selected and designed based on the Toyota Prius 2010 machine benchmark for EV/HEVs. The electromagnetic performance of selected AIPM and conventional IPM machines are compared. It is revealed that three proposed AIPM machines with asymmetric PMs and asymmetric rotor cores can effectively enhance torque density and comprehensively improve the machine characteristics compared with other AIPM machines and the IPM machine benchmark, which are proved to be potential candidates for EV/HEV applications.