Loss Minimization Design of Ferrite Core in a DD-Coil-Based High-Power Wireless Charging System for Electrical Vehicle Application

In this article, a core design and optimization method is proposed for the double-D (DD) coil-based inductive wireless charging system (WCS) to minimize the core loss. Core loss is the most significant loss in a medium to high power wireless charging pad. Conventional approaches assume a uniform distribution of the magnetic field in the core. However, the magnetic field in the core is highly nonuniform, which leads to a localized higher core loss. For investigating the loss behavior thoroughly, the core loss versus the flux density distribution has been studied analytically for varying core geometry. Based on this analysis, an optimal criterion has been derived for geometric design of the core to minimize the core loss. The proposed model is verified through finite element analysis (FEA) and tested through a laboratory prototype of DD coil-based 5.0-kW WCS. Experimental results showed a noticeable core loss reduction up to 25% compared to the conventional block and bar core.¹¹This article is prepared based on a closely related concept of the authors presented in the IEEE Applied Power Electronics Conference (APEC) in March 2018 [7].