Design and analysis of a new outer-rotor permanent-magnet flux-switching machine for electric vehicle propulsion

摘要

Purpose - The purpose of this paper is to propose a new outer-rotor permanent-magnet flux-switching machine (ORPMFSM) for electric vehicle (EV) in-wheel propulsion. The paper documents both the design procedure and performance investigation of this novel machine. Design/methodology/approach - The topology and preliminary sizing equations of the ORPMFSM are introduced. The rotor poles are optimized, whilst the machine losses are particularly investigated, using 2-D finite element analysis (FEA). Findings - An ORPMFSM, with 12 stator poles and 22 rotor poles, is most suitable for the proposed EV application. The analytical sizing equations are quite efficient with a sufficient accuracy for the preliminary design. The optimal rotor pole width from the FEA results is nearly 1.3 times the original value which was proposed in early literatures. The efficiency of the proposed machine under rated load is slightly low, as a result of significant eddy current losses in the permanent magnets. The losses can be effectively suppressed with the technique of magnet segmenting. The predicted outstanding performance implies that by adopting magnet segmentation the proposed machine is a leading contender for EV direct drives. Originality/value - The outer-rotor structure of PMFSM was not addressed in early literatures. This paper provides designers with the technical background and an alternative candidate for the EV propulsion.