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This paper presents a new rotor shape design with optimum reverse 3rd harmonic for wound field synchronous machines to effectively enhance the saliency ratio and reduce the torque ripple in a micro electric vehicle traction system. Due to the enhanced saliency ratio, the reluctance torque is expected to be improved. The air gap flux density distribution is reshaped by the new rotor shape method, which benefits the low torque ripple. By contrast, the reverse 3rd harmonic injection is much more suitable than the general 3rd harmonic injection for increasing the effective air gap length along the q-axis for a high saliency ratio. Subsequently, three amplitudes of the reverse 3rd harmonic are studied and it is found that the optimum reverse 3rd harmonic is 1/6 of the fundamental one. To verify the effectivity of the proposed design, the original model and the ICS model are compared. Finally, all the motor characteristics, such as back electromotive force, cogging torque, and electromagnetic torque, are predicted using a 2-D finite-element method with the aid of JMAG-Designer. [ABSTRACT FROM AUTHOR]

The paper proposes a hybrid-excited wound field synchronous machine (HE-WFSM), which can achieve high reluctance torque utilization. The key of the proposed HE-WFSM is that two permanent magnets (PMs) assist each rotor pole in forming an additional magnetic flux circle. It is opposite to the magnetic flux circle along the q-axis in the WFSM. The reduction of the q-axis flux can help to improve the saliency ratio and reluctance torque. Additionally, the asymmetrical flux linkage achieves a closest current phase angle between the maximum field torque and the maximum reluctance torque. To highlight the advantages of the proposed HE-WRSM, a general WFSM was adopted as the basic machine and analyzed under the same operating conditions. All performances of the basic machine and proposed HE-WFSM were predicted using finite element analysis (FEA) in Jmag-Designer. Finally, it was confirmed that the proposed HE-WRSM can achieve high reluctance torque utilization. [ABSTRACT FROM AUTHOR]