Eddy Current Loss Model for Ferrite Ring Cores Based on a Meta-Material Model of the Core Properties

Abstract

A model for estimating the total eddy current losses in ring ferrite cores is proposed, which is based on a microstructure model of the electrical parameters of the material (conductivity and permittivity) and on the solution of the wave equations in the core. The presented model, combined with state of the art estimation of the hysteresis losses gives good agreement with the core loss measurements, over a wide range of frequency (10 kHz to 700 kHz).

Semi-Lumped Model for the Calculation of Frequency Dependent Complex Permeance for U- or E-Cores

“…Once the equivalent ring corner has been derived, its permeance can be calculated using the solution of the wave equations given in [3]. The actual value is obtained by integrating analytically the magnetic field over the cross section [2]. The two corner cross section formulas as well as the derivation of the permeance will be discussed in the final publication.…”

“…Because of a non negligible permittivity of the core, both resistive and capacitive eddy currents occur in the core. Between 100 and 1000 kHz, these make the frequency scaling of the core loss diverge from a power law and change the permeance, and hence the inductance [2].…”

“…To solve this issue, analytical models can be used. For instance, in [2], a model of frequency dependent permeance and core losses for ring cores is presented, which uses the analytical solution to wave equations in the core from [3] and a frequency dependent material model from [4]. To make this approach available to a broader range of applications, the method needs to be adapted to core shapes other than ring cores.…”

“…Moreover, the geometry of these rectangular cores is not axial symmetric, unlike ring cores. Consequently, it is not possible to analyse the device by simply considering its cross section as shown in [2], [3] for ring cores. In contrast, modelling the frequency behaviour of rectangular cores demands a new method to calculate the complex permeance of the core, provided its material parameters are given.…”

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

“…Several methods have been developed to calculate core losses, often derived from the Steinmetz Equation. Nevertheless, these methods have proved to be not reliable in terms of frequency scaling above approximately 100 kHz [2]. Therefore, reference [2] proposes an alternative core loss calculation method based on the physical modelling of the resonance of the electro-magnetic field in the core.…”