Energy Efficiency Analysis of U-coil Wireless Power Transfer System

Abstract

In order to improve the power transfer efficiency and ensure the space cleanliness of power transfer direction in inductive coupled wireless power transfer (WPT) system, a new U-coil WPT system is proposed. Based on the mutual inductance coupling theory, a new methodology for ensuring that a U-coil system is more energy efficient than a two-coil counterpart is presented in this paper. The theoretical proof and the conditions for meeting the objective are derived and practically verified in a practical prototype. The experimental results show: 1) comparing with two-coil system, power transfer efficiency can be improved more than ten times by using U-coil system; and 2) with the same power transfer efficiency principle, the dimension of primary and load coils in U-coil system shrinks at least 66% comparing with that of two-coil system. The U-coil system not only improves power transfer efficiency but also ensures the cleanliness of the space along the energy transfer direction.