Comparison of coil topologies for inductive power transfer under the influence of ferrite and aluminum

In recent years, there has been growing interest in inductive power transfer (IPT) systems for electric vehicles (EVs). Wireless power transfer systems consist of complex coil systems made up of current-carrying litz wires varying greatly in shape and in material for confining and guiding magnetic flux. A large number of geometric degrees of freedom and variables must be defined and optimized in designing a coil system. Against this background, this paper points out first the fundamental role of materials for shielding and flux guidance and their influence on the main quantities of an IPT system. Furthermore, variations in size of the materials show their significance for wireless power transfer systems. Based on these findings, various magnetic couplers are analyzed and evaluated. The specific strengths and weaknesses of the geometries are highlighted in terms of previously defined evaluation criteria, and the optimal field of application of the couplers is identified. It is shown, how ferrite and aluminum influence the characteristics of the various coupler topologies.