The difference of rotor magnetic circuit configuration will directly affect the magnetic field distribution, losses and temperature rises of motor . A few papers have been published on the performance comparison of different rotor configurations [1][2][3] . However, few papers compare losses and temperature rises in various regions of motor with different rotor configurations . In this paper, the performances of a surface-mounted permanent magnet (SPM) motor and a series-parallel hybrid magnetization interior permanent magnet (IPM) motor are researched, the airgap flux density, losses and temperature rise of two machines with the same stator size, airgap length, armature core length, winding construction, material, permanent magnet consumption, armature current, and speed are compared . The finite element analysis (FEA) models are shown in Fig .1 . Non-magnetic spacers are specially designed at the end of magnets of IPM motor for magnetism isolating . Analysis reveals that the amplitude of flux density of IPM motor is higher than that of SPM motor with the same permanent magnet consumption due to flux focusing effect . For high-power and high-speed PM motor, the proportion of copper loss in motor losses is smaller than that of iron loss . Therefore, the copper losses of two machines are kept the same, which means identical phase currents, to make it easier for comparing the more complex and dominant iron losses . Eddy current loss may be induced in permanent magnets and sleeve if fitted due to space mmf harmonics and time mmf harmonics, and it may cause significant temperature rise of magnets as the result of poor heat dissipation condition in the rotor, which in turn may cause irreversible demagnetization of the magnets . Consequently, it is essential to consider the effect of eddy current loss on temperature rise . Iron loss in each mesh element can be separated into the hysteresis loss, eddy current loss and excess loss [4] . The calculation precision of iron loss is highly depended on the flux density used . Consequently, numerical analyses are performed using the flux densities in each element in various parts of the motor obtained from FEA to calculate the iron loss accurately . Non-linear magnetostatic FEA is performed as the rotor rotating incrementally over 360 electrical degrees at the speed of 8200rpm . The result shows that the hysteresis loss in stator of SPM motor is higher than that of IPM motor while the eddy current loss in stator of SPM motor is less than that of IPM motor . The iron loss in rotor back iron of IPM motor is significantly higher than that of SPM motor due to the skin effect, while the eddy current loss in sleeve of SPM motor is the most significant among rotor losses . The comparison result reveals that the gross loss of IPM motor is higher than that of SPM motor . Thermal fields of two machines are analyzed using analytical lumped-circuit method based on the losses derived . Conduction, convection and radiation conditions along heat-transfer paths between components and with ambi...
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