Investigation of core-loss mechanisms in large-scale ferrite cores for high-frequency applications

In this paper, core-loss mechanisms in ferrite cores are investigated. It is demonstrated that ferrite materials showing almost identical core-losses in the datasheets exhibit a completely different loss-behavior when cores with large cross-sections are manufactured. Therefore, there is a high risk that the wrong ferrite material is selected in the design process of a magnetic component for power electronic applications when only the losses from the datasheets are considered. Consequently, a model is developed which leads to a better understanding of the origin losses in ferrite cores and can be used as powerful tool to design and optimize magnetic components for high-frequency applications. With this model, formulas are derived which allow the calculation of two additional loss contributions which are the electrical polarization losses and the volume eddy current losses. In a detailed experimental study of various ferrite core shapes and sizes the model is verified and clearly shows that for example at 100kHz with a magnetic cross-section of 500mm², the additional losses cannot be neglected. The dependencies and input parameters are discussed in detail. Finally, a FEM-based workflow is presented and verified by calorimetric measurements. In the future, this workflow can be used to precisely predict the losses of virtual prototypes in a development process i.e., for automotive applications.