Development of WPT Systems for Railway Vehicles and Study for Low-Frequency Application

We designed the WPT system for railway vehicles that has a maximum transfer power capacity of approximately 1 MW per car. This system is of the magnetic field coupling type, in which a figure-eight-shaped coils are energized with a high frequency of approximately 10 kHz. Validation through bench tests using a scaled-down experimental device confirms the design's efficacy. Despite the advantages, high-frequency systems exhibit drawbacks such as large AC losses and high equipment costs. We explored frequency reduction possibilities, particularly aiming at commercial frequencies, anticipating significant cost reductions by omitting a high-frequency inverter on the ground. An example at 50 Hz shown the feasibility of 300 kW power transfer per car while maintaining coil spacing. Modifying the ground coil structure by adding an iron core improved magnetic coupling, suppressing onboard circuit capacity increase, and allowing for equipment dimensions suitable for onboard mounting.