Coupled 2-D and 3-D Eddy Current Analyses for Evaluating Eddy Current Loss of a Permanent Magnet in Surface PM Motors

To evaluate the eddy current losses of permanent magnets (PMs) in interior PM (IPM) motors accurately within the practical CPU time, we have already proposed a scheme to carry out the 3-D eddy current analysis of only the PM using the temporally varying flux distribution obtained from the 2-D magnetostatic analysis of the motor. In the 3-D eddy current analysis, the compensation field H_c generated by the eddy currents in PM itself only is taken account of. Moreover, the reluctance of the motor except the PM obtained from the 2-D magnetostatic analysis is also taken into account by adding a uniform equivalent gap on the PM. The effectiveness of the coupled 2-D and 3-D analyses was shown using an actual IPM motor. In this paper, the coupled analyses are improved to apply to a surface PM (SPM) motor. Namely, the uniform equivalent gap is improved to a variable equivalent gap in space to take account of the space variation of the gap width between the PM and the stator core. Moreover, the 2-D magnetostatic analysis of the motor is replaced to the 2-D eddy current analysis to take account of not only the H_c by PM itself but also that by the neighboring PM. It is shown that the proposed coupled 2-D and 3-D eddy current analyses can improve the accuracies of the eddy current loss distribution in PMs of a SPM motor without increasing the CPU time.