Advances in inductively coupled power transfer technology for rail transit

Abstract

Traditional power supply method for moving electric railway vehicles is based on contact type power collection technology. This sometimes cannot meet the requirements of modern rail transportation. A new wireless power transfer (WPT) technology can offer significant benefits in modern rail transportation particularly in some stringent environments. This paper reviews the status and the development of rail transit power supply technology, and introduces a new challenging technology--inductive power transfer (IPT) technology for rail transit. Tesla established the underpinning of IPT technology and creatively and significantly demonstrated power transfer by using highly resonant tuned coils long time ago. However, only in recent years the IPT technology has been significantly improved including the transfer air-gap length, transfer efficiency, coupling factor, power transfer capability and so on. This is mainly due to innovative semiconductor switches, higher control frequency, better coil designs and high performance material, new track and vehicle construction techniques. Recent advances in IPT for rail transit and major milestones of the developments are summarized in this paper. Some important technical issues such as coupling coil structures, power supply schemes, segmentation switching techniques for long-distance power supply, and bidirectional IPT systems for braking energy feedback are discussed.

Keywords

• bidirectional energy transfer
• inductive power transfer (ipt)
• magnetic coupling
• rail transit
• segmented power supply
• wireless power transfer (wpt).