Smart coil design for remote inductive WPT with ferromagnetic or conductive materials

Abstract

In this study, a smart coil design to improve the performance of the remote inductive wireless power transfer (WPT) system by analyzing the characteristics of the ferrite cores used in the magnetically coupled WPT coils. The ferrite cores have the advantage of increasing the magnetic flux due to the high relative permeability (~2000). However, they have two disadvantages. Firstly, magnetic flux density is concentrated only in the surrounding area where the ferrite cores are located. Secondly, ferrite core causes non-linear magnetic field distortion, which is still beyond physical theory. In chapter 2, a coreless transmitting (Tx) coil structure is newly proposed for wide-range WPT system. Based on the detail analysis of the magnetic shielding function of the ferrite core, the proposed Tx coil structure replaces the ferrite core to conductive plate to shield the undesired magnetic flux. In the proposed wide-range wireless charging zone, wireless charging can be conducted regardless of the number and direction of receiving (Rx) coils, and it has been proved through simulation and experiment that the magnetic field uniformity is improved 2.4 times compared to the conventional ferrite structure. In chapter 3, an optimal ferrite structure design of the magnetically coupled WPT coil by artificial neural network based machine learning algorithm is newly proposed. Since the non-linear magnetic field distortion caused by the ferrite core is still beyond physical theory, therefore, the artificial neural network is utilized to learn the contribution of the ferrite core to the coupling coefficient between the Tx and Rx coils through simulation data. By training only 2.3 % data out of total possible cases, it is experimentally verified that the core structure obtained by the proposed method has a coupling coefficient 7 % higher than that provided by the general knowledge design level.