Citation:
W-Z Fei, J-X Shen, C-F Wang, PC-K Luk. Design and analysis of a new outer-rotor permanent-magnet flux-switching machine
for electric vehicle propulsion. COMPEL: The International Journal for Computation and Mathematics in Electrical
and Electronic Engineering, 2011, Volume 30, Issue 1, pp48-61
Abstract:
Purpose − The purpose of this paper is to propose a new outer-rotor permanent-
magnet flux-switching machine for in-wheel electric vehicle 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 outer-rotor permanent-magnet flux-switching machine are
introduced. Both the number and width of rotor poles are then optimized using
comprehensive two-dimensional FEA. The machine losses are particularly
investigated by transient FEA for the optimal design. Findings − A outer-rotor
permanent-magnet flux-switching machine, with 12 stator poles and 22 rotor
poles, is most suitable for the proposed application. The analytical sizing
equations are quite efficient with a suitable level of accuracy for preliminary
design. The optimal rotor pole width from the FEA results is nearly 1.3 times of
the original one. The efficiency of the proposed machine under rated load is
relatively low, nearly 85%, as a result of significant eddy current losses in
the permanent magnets, which can be effectively suppressed by implementing
segmentation. The predicted outstanding performance implies that by adopting
magnet segmentation the proposed machine is a leading contender for direct
electric vehicle drives. Research limitations/implications − The end effects,
which could be considerable in the machine with relatively short axial length,
are neglected during the study. In addition, due to the high current density and
deep slot, proximity losses in the winding which is not issued in this research
could be significant. All the limitations mentioned above could bring
corresponding errors to the results. Although the research is concentrated on
the application of electric vehicle drive, the techniques can be potentially
employed for other applications. Practical implications − The practical
implementation of such a machine is confronted with several mechanical hurdles,
especially the thermal issues which can be addressed by implementing innovative
cooling system. Originality/value − The outer-rotor permanent-magnet flux-
switching machines so far have not been addressed yet. This research provides
designers with the technical background and another alternative for electric
vehicle