Magnetic-circuit-based iron loss estimation under square wave excitation with various duty ratios

In recent years, development of high-efficiency electric machines is strongly required from the viewpoint of energy saving and environmental protection. It is essential, therefore, that establishment of a simple and practical method for calculating iron loss with high accuracy. This paper presents a novel magnetic circuit model which is obtained from an empirical expression for the iron loss of soft ferromagnetic materials. The proposed magnetic circuit model consists of three elements as follows: a dependent source which expresses dc hysteresis, an inductance element which denotes eddy current loss, and a dependent source which represents anomalous eddy current loss. These elements can be simply obtained from dc hysteresis loops and core loss curves of core material. The validity and usefulness of the proposed method is proved by comparing with experimental results under square wave excitation.