Experimental, theoretical and numerical investigation of core losses in laminated magnetic materials

Measurements of a wide range of thicknesses and frequencies have been carried out to study core losses in magnetic materials. Core loss measurements show that losses increase with both thickness and frequency. Analysis of measurements shows that certain measured magnetic properties, e.g. core losses, the B -- H relationship, and the dynamic hysteresis effect, are fundamentally related to the skin effect. It is concluded that magnetic properties measured for the case when the skin effect is negligible is the fundamental magnetic property.;Based on the understanding of magnetic measurements, an analytical eddy current core loss model is established with an assumption of constant magnetic permeability. The model removes the uniform field assumption that allowed G. Bertotti to establish a core loss formula. As a result, the analytical core loss model can provide a more general core loss calculation formula. Specifically, it can use only two sets of experiment data to provide accurate core losses for different thicknesses and frequencies.;In addition to the analytical core loss model the analytical core loss formula, a numerical approach to a dynamic core loss model is also been developed, based on a better understanding of magnetic properties obtained from the measurements. The model solves Maxwell's Equations and Ohm's law in a magnetic lamination with a hysteresis property using a high order finite element method. Based on the simulation results, the magnetic characteristics, the dynamic hysteresis effect, the skin effect, the time delay and the magnetic field distribution are also discussed. It is suggested that excess current losses are due to the non-uniform magnetic field distribution resulting from the skin effect and non-linear diffusion of magnetic flux from the boundary to the interior of the lamination.;Core losses calculated with the dynamic core loss model are also compared with experimental measurements. The comparison shows that the model can provide accurate loss calculation for different thicknesses and frequencies based on only one set of experimental measurements of the B-H loop at a low frequency in a thin lamination. To our best knowledge, this is the first approach to a core loss model, which can be applied to a wide range of operating frequency and lamination thickness, using the measured data collected at only one single frequency.