Analysis and evaluation of novel rotor permanent magnet flux‐switching machine for EV and HEV applications

To relieve the serious saturation in stator teeth of stator‐permanent‐magnet flux‐switching (SPM‐FS) machines due to the co‐existence of magnets and armature windings in stator, this study proposes and analyses a novel rotor‐permanent magnet flux‐switching (RPM‐FS) brushless machine. Different from the conventional SPM‐FS machines, the magnets are removed from stator to rotor, and magnetised in a unique direction, resulting in a significant alleviation of stator tooth saturation level for the RPM‐FS machines. The concentrated armature windings are still wound around stator teeth with an even shorter end‐part winding length due to the absence of magnets. To evaluate the advantages and disadvantages of RPM‐FS machines, a comprehensive comparison between a RPM‐FS machine, a SPM‐FS machine, and an interior permanent magnet machine used in Toyota‐Prius 2004 hybrid electric vehicle, is conducted and the electromagnetic performances of three machines are investigated by finite element analysis. The predicted results indicate the proposed RPM‐FS machine exhibits the largest power density, greatest torque capability, highest efficiency under rated operation, and improved flux‐weakening ability. Therefore, the RPM‐FS machine is a promising candidate for EV and hybrid electric vehicles applications especially for direct driven systems where the superior overloaded performance is crucial.