Loss Analysis of Interior Permanent Magnet Motors Considering Carrier Harmonics and Magnet Eddy Currents Using 3-D FEM

In this paper, we investigate losses of interior permanent magnet motors driven by PWM inverters using the 3-D finite element analysis, which can estimate the eddy current loss in the permanent magnet accurately. The calculated losses are compared with the measured results and the theoretical solution to verify the validity of the analysis. The method to decompose the electromagnetic field distribution into time-harmonic components is introduced in order to investigate the effects of the harmonic fields separately and to specify the main loss factors. The variation of the magnet eddy current loss due to the division of the magnet is also investigated. It is clarified that the eddy current loss in the permanent magnet is mainly produced by the carrier harmonics of the inverter and that the axial length of the divided magnet should be smaller than the skin depth of the eddy currents produced by the major harmonics for the loss reduction.