Modeling of the Resistance of a Coil Module with Ferrite and Shielding for Wireless Power Transfer in Electric Vehicles

For optimal design of a wireless power transfer system, knowing the electrical resistance of the coil modules is essential. For vehicle applications, a flux guidance and aluminum shielding are used in addition to the winding. Beyond considering the individual components, an understanding of the interactions between them is also necessary to determine the coil module resistance. This paper first provides the theoretical background of the relevant loss effects in litz wire and coil modules. Existing approaches are then analyzed for their applicability for the application considered in this work. Based on this analysis, a practical method is proposed that systematically combines established approaches from the literature to calculate the electrical resistance of a coil module while accounting for the effects of both flux guidance and shielding. In contrast to existing approaches, which primarily address individual components or effects, the proposed method enables the resistance of the entire coil module to be determined within a unified modeling framework. The method is verified by comparison with measured results, showing good agreement with a maximum deviation of 2%. The presented approach supports the efficient design of wireless power transfer systems and substantially reduces the need for repeated coil module prototyping and resistance measurements.