Core Loss Analysis and Modeling of a Magnetic Coupling System in WPT for EVs

The magnetic core is an important part of the magnetic coupling system in wireless power transmission (WPT) for EVs. It helps to increase the coupling coefficient and reduce magnetic field leakage. However, it also brings additional core loss. While the traditional core loss model cannot be used directly due to the uneven distribution of the magnetic flux density, this paper focuses on the flux density distribution in the disk core of a WPT system. Based on a finite element analysis (FEA) simulation and a theoretical magnetic flux density distribution analysis, a mathematical model of magnetic flux density distribution is built, which is regarded as a quadratic function. Through this model, the flux density distribution can be calculated by the electrical and mechanical specifications of the magnetic coupling system. Combining the model of flux density distribution, the disk core loss model of the WPT system is proposed—the idea of which is dividing the disk core into several circle sheets firstly, and then summing the core loss of all circle sheets. Finally, the FEA simulation results verify the proposed model as being correct and flexible.