Iron loss analysis and reduction techniques of magnetic geared permanent magnet motors

This paper presents the iron loss analysis of magnetic geared permanent magnet motors (MGPM), and suggests iron loss reduction techniques. In this paper, the hysteresis loss coefficient, the eddy current loss coefficient, and the excess loss coefficient for the modified Steinmetz equation are derived from the Epstein test data using a curve fitting method (CFM). Owing to a much greater iron loss occurring in the rotating field than in the alternating field [3], we separate the rotating and alternating fields and they can be distinguished using the axial ratio of loci. Finally, the iron loss at each electrical steel is calculated using a modified Steinmetz equation that considers the rotating field and flux path. Figure1. (a) shows the schematic of the MGPM, Fig.1. (b) shows the distribution of the flux density on the electrical steel, and Fig.1. (c) shows the analysis points for iron loss at each electrical steel section. We analyzed the magnetic flux density at each point in the rotor core, modulation layer, and stator core. We then, calculated the iron loss using the modified Steinmetz'sequation considering the rotating field and the alternating field. Figure 2. (a) shows a comparison of loci and axial ratio at each region, Fig.2. (b) shows fast Fourier transform (FFT) analysis results at each region, and Fig.2. (c) shows the iron loss analysis results for the original model and the proposed model. The total iron loss of the proposed model is about 15% less than that of the origin model. Furthermore, in this paper, a technique is proposed for reducing the iron loss in the modulation layer, which contributes the most to the total iron loss. More detailed discussions and analysis results will be presented in the final paper.