Optimal Design Of Magnetically Coupled Resonant Wireless Power Transfer System For Embedded Systems

Through magnetically coupled resonant wireless power transfer(WPT)technology,power can be transmitted efficiently over mid-range distances.Power supply to embedded systems on rotating spindle based on this technology has become a hot issue.However,in traditional WPT systems applied to this field,the power transfer becomes unstable and the average efficiency is low as the spindle rotates.This paper presents a novel double-ring coil to deliver power to embedded systems on rotating spindle based on magnetically coupled resonant WPT technology,which can solve the problems mentioned above.The main contents and conclusions of this paper are presented as follows:Firstly,the mathematical expression of maximum power transfer efficiency under resonant condition is derived through theoretical analysis.The effects of coil parameters including self-inductance,mutual inductance,resistance and Q-factor upon the efficiency are theoretically analyzed;besides,the performance of the system with coils of different structures as well as varied positions is analyzed in this paper,which provides guidance for the optimal design of coil.Secondly,the problems of traditional WPT system metioned above are analyzed through finite element method(FEM).To solve the problems,this paper presents a novel double-ring coil and analyzes the characteristics of the magnetic field generated by the coil.The coil structure is designed according to the practical demands.The distribution of magnetic field and the performance of the double-ring WPT system with coils of different radius,width and position are analyzed.The result proves that the proposed system can deliver power to embedded systems on rotating spindle stably and efficienctly.It also shows that to increase the power transfer efficiency,the axial deviation as well as the differences of radiuses and widths of the two coils should be reduced.Finally,the double-ring WPT system and the traditional system are built.The experiments on the effects of varied rotating angles and the metal spindle upon the performances of the two systems are conducted;besides,the experiments on the effects of the radiuses and widths of the coils upon the efficiency of the double-ring WPT system are conducted.The results show that the power delivery of the double-ring WPT system is more stable and efficient than that of the traditional system.It also shows that the power transfer efficiency is maximized when the transmitting coil has the same radius as the receiving coil,and the efficiency increases as the width difference of the two coils increases.