Iron Loss and Efficiency Analysis of Interior PM Machines for Electric Vehicle Applications

An interior permanent magnet (IPM) machine with ∇+U shape rotor topology is proposed for electric vehicle applications whose iron loss and efficiency are compared to that of typical V shape and ∇ shape machines. The air-gap flux density, flux-density waveform, and its harmonics on stator core and rotor core are analyzed. It can be obtained that ∇+U shape rotor topology has the lowest total harmonic distortion. The torque ripple, core loss, core loss density, PM eddy-current loss, d- and q-axis inductances, saliency ratio, characteristic current, and efficiency of three IPM machines are analyzed and compared. It is demonstrated that the efficiency of ∇+U shape IPM machine is higher than V shape and ∇ shape machines, particularly under high-speed operation, because the iron loss of the ∇+U shape machine is the lowest. With the increase of PM layer, the PM eddy-current loss is increased, PM segmentation can effectively reduce the PM eddy-current loss. Finally, the ∇+U shape IPM machine is prototyped to verify the results of the finite element analysis.