Power Transmission Characteristics in Commercial Frequency of Wireless Power Transfer System for Railway Vehicles Using High Temperature Superconducting Coil

Abstract

This study investigated experimentally and analytically the power transmission characteristics of High Temperature Superconducting (HTS) coils at commercial power supply frequency (50 Hz) to realize highly efficient power transmission in wireless power transfer systems for railway vehicles. We proposed a solenoidal coil with a thin magnetic core as an HTS coil structure suitable for lower frequencies and investigated its effectiveness by finite element analysis. The analysis results showed that the proposed coil can significantly suppress the current increase due to the low frequency of the wireless power transfer system. We also investigated the core shape to reduce the losses of the proposed coil and found that the loss in the coil can be reduced by increasing the length and thickness of the magnetic core. Furthermore, we compared the power transmission characteristics between the proposed coil and the conventional spiral coil and showed that the proposed coil could improve the overall efficiency by about 10 %. The power transmission characteristics at 50 Hz were also measured using the scaled-down model coil. As a result, we demonstrated that highly efficient power transmission could be achieved at 50 Hz by using the proposed solenoidal coil with a magnetic core.