Macromagnetic Approach to the Modeling in Time Domain of Magnetic Losses of Ring Cores of Soft Ferrites in Power Electronics

This article presents a new modeling approach capable of predicting Eddy current losses in soft ferrite cores as a function of the winding current. The proposed model is formulated in the time domain, which defines the magnetic core as a repeated regular structure of magnetic material grains and grain boundary in space. In this way, the homogenization process of the material is avoided, which is intended as the definition of a set of physical parameters of a continuous material equivalent to the real structure of the material. The distribution of the current density in the core and the core losses are computed utilizing the physical and geometric parameters of the grain of the magnetic material and of the grain boundary. To address the uncertainty in the definition of the physical and geometrical parameters of the magnetic grain and the grain boundary, a dedicated optimization procedure has been formulated, which takes into account the inaccuracy in the parameter measurement and the fact that the grain contour is an irregular surface and the boundary thickness is neither constant nor uniform. The performance assessment of the model is carried out over a broad frequency range using several experiments with a power amplifier and a dc–dc converter.