Improving Efficiency of a Wireless Power Transfer (WPT) System by Increasing Coil-Width

Abstract

Efficiency of a wireless power transfer (WPT) system depends on the resonance components and mutual inductance between primary and secondary coils of the transformer. Therefore, design of coils of a transformer is very crucial in WPT system as primary and secondary coils of the WPT transformer are separated by a large air gap. Due to large air gap between primary and secondary coils, coupling coefficient in a WPT system is very low compared to conventional transformer. Therefore, efficiency of the system is very low. In this paper, it is discussed that efficiency of a wireless power transfer (WPT) system can be enhanced by increasing its coil-width.

Introduction

I. INTRODUCTION

Wireless power transfer (WPT) system is a two-coil system, namely primary and secondary windings demonstrated by a century ago by several famous scientists like Tesla, Hutin and Leblanc [1, 2]. Electromagnetic induction principle utilizes the magnetic coupling between transmitting and receiving coils for power transmission and in a WPT system power is transferred between the two coils through an air gap (without core). The magnetic coupling in WPT systems is very weak due to large air gap. This is one of the major drawbacks of a WPT system. To improve the magnetic coupling for delivering the required power to the load, WPT systems are always operated at high frequency. However, at high frequency, switching losses are incurred, which affect the efficiency of the system. Therefore, WPT systems are usually operated at resonant frequency. Resonant circuits are normally employed in the primary and/or secondary circuits to boost the power transfer capability, while minimizing reactive power requirement from the source.

However, in WPT system, power is transferred from source to the load over a large air gap. Therefore, the coupling coefficient of WPT transformer is very low thereby reducing the overall power transfer efficiency of the system. The efficiency of a conventional WPT system depends on the air gap between the transmitting and receiving windings. Efficiency drops rapidly as air gap distance increases. In order to achieve a reasonable level of efficiency and transfer distance, the use of the relay resonators based on the maximum efficiency principle have been considered in [3].

Conclusion

In this study, a WPT system with large air gap has been proposed for improving its efficiency using increased coil-width. It has been shown that with the increased coil-width, mutual inductance and coupling coefficient improve considerably thereby improving the overall performance of the system. However, there is a limit for extending the coil-width, beyond which mutual inductance or coupling coefficient does not improve significantly. The present concept of design for a WPT system can be applied to low as well as high power applications.

References

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Copyright

Copyright © 2024 Prabhat Chandra Ghosh. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.