Design and Analysis of a Novel Magnetic Coupler of an In-Wheel Wireless Power Transfer System for Electric Vehicles

Young Jin Hwang,Jae Young Jang

doi:10.3390/en13020332

Abstract

Electric vehicle (EVs), which use an electric motor, are expected to replace internal combustion engine vehicles. However, to date EVs are not highly attractive to consumers due to their unsatisfactory battery charging characteristics and high cost. In particular, the existing conductive charging method makes it more difficult to spread EVs due to the inconvenience of charging and the risk of electric shock. The wireless power transfer (WPT) system can eliminate all of the charging troubles of EVs. However, the WPT systems in existing EVs have large air gaps between the transmitter coil and the receiver coil, posing a hurdle that prevents success. The large air gap cause issues such as a loose coupling, low efficiency, and troublesome electromagnetic compatibility (EMC). An in-wheel WPT system can serve as a solution to address the issues arising due to the large air gap. In this paper, we propose a magnetic coupler structure of an in-wheel WPT system for EV applications. A design of two coils is introduced, in which the transmitter coil and receiver coil are designed based on a design method. Moreover, the pad structure according to the ferromagnetic core geometry is designed and discussed. The aim of this research is to find a suitable configuration of the magnetic coupler for an in-wheel WPT system. The values of the coupling coefficients according the magnetic coupler structure are determined. This paper is expected to provide a good reference for further research, including work on the manufacturing of a prototype.

Highlights

Electric vehicles (EVs) are a clean and environmentally friendly alternative to conventional vehicles which utilize an internal combustion engine (ICE)
The power transfer efficiency decreased with the gap distance and alignment between two coils
In order to address the distance problem, in-wheel wireless power transfer (WPT) systems was studied in this paper

Summary

Introduction

Electric vehicles (EVs) are a clean and environmentally friendly alternative to conventional vehicles which utilize an internal combustion engine (ICE). They usually use electric batteries instead of fossil fuel on board to store electric energy for vehicle propulsion. Large-capacity and high-power battery packs are typically required to make EVs operate over satisfactory distances. Reliable and competitive batteries for EVs are not easy to realize due to the following requirements: (1) an affordable cost, (2) high safety levels, (3) high power density levels, (4) a long cycle lifetime, and (5) a low volume and weight, all of which should be satisfied simultaneously.

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