Iron Loss Analysis of Permanent Magnet Motors by Considering Minor Hysteresis Loops Caused by Inverters

In this paper, we propose a loss calculation method considering minor hysteresis loops for permanent magnet (PM) motors driven by pulse width modulated (PWM) inverters. In the governing equation of the proposed method, both the effects of the major and minor hysteresis phenomena are expressed by a reaction magnetic field. This field is determined by iterative calculations of finite-element analysis (FEA) with a simple hysteresis modeling that considers the minor loops. The proposed method is applied to a PM motor, and the experimental verification is carried out. It is clarified that the minor hysteresis loops affect not only the hysteresis loss but also the eddy current loss because the skin depth varies with the differential permeability of the minor loops.