Non-Linear Material Model of Ferrite to Calculate Core Losses With Full Frequency and Excitation Scaling

Abstract

A material model for ferrite is presented, enabling an accurate calculation of the core losses from 100 kHz to 1000 kHz with a single set of scalar parameters over a decade of excitation current. It is based on the modelling of different material effects such as quantum tunnelling conduction between ferrite grains and atomic level magnetisation. The implications of the satisfying results of this approach on core loss modelling techniques at high frequencies are discussed.

Semi-Analytical Non-Linear Physical Model of Core Losses in Ferrite Ring Cores

“…This wave equation includes the permittivity, the conductivity, and the complex permeability of the material. Considering a complex permeability enables the calculation of hysteresis and eddycurrent losses in a single model, including the interaction between these two loss phenomena [6]. The three electromagnetic material properties (permeability, permittivity, and conductivity) depend on the frequency and on the amplitude of the excitation because of several physical effects which are included in the material model given in [6].…”

“…2c. The bias voltage over the boundary is considered as V b = E • l g with E being the electric field magnitude in the ferrite and l g being the typical length of a grain [6].…”

“…The presented model successfully predicts the frequency scaling of the losses but its base material parameters are dependent on the excitation amplitude, requiring parameter lookup tables and consequently increasing the amount of data, which is necessary to run the model. To increase the applicability of the model given in [3], the material model has been improved in [6] by including non-linear effects such as quantum tunnelling conduction as described in [7] and frequency dependency of the permeability as described in [8].…”

“…So far, the material model given in [6] has only been used with Finite Element Method (FEM) to solve the wave equation. Unlike analytical derivations, which usually require homogeneous material properties, FEM enables to solve equations considering materials with heterogeneous properties.…”

“…To accelerate the calculation, this paper proposes a new semi-analytical method to calculate core losses accurately in a computationally efficient approach. It combines the analytical solution of the wave equation in the core given in [5], with the non-linear material model given in [6] using a new iterative procedure using a newly defined effective electric field.…”