Superconductivity for railway applications

Practical superconductivity applications offer significant advantages in energy efficiency and have considerable strategic importance. Owing to their zero-resistance property, superconductors offer great potential for railway transportation power equipment, such as superconducting cables and traction transformers. By exploiting the nonlinear current-temperature characteristics of superconductors, superconducting fault current limiters can be developed. Compared with conventional equipment, superconducting power devices enable low-loss, high-capacity power transmission and compact system integration. Moreover, superconducting devices, such as superconducting motors, superconducting bearings, and superconducting magnetic energy storage systems, offer high power density and low losses. The ability of superconducting magnets to carry large currents and generate high magnetic fields also makes them attractive for maglev transportation. Superconducting maglevs can levitate above the guideway without friction, which is conducive to higher speeds. Superconducting maglev systems can be broadly classified into low-temperature superconducting electrodynamic suspension (LTS EDS), high-temperature superconducting EDS (HTS EDS), and HTS pinning (HTSP) maglev systems. LTS EDS in Japan has achieved speeds of up to 603 km h-1. HTSP maglevs also have the potential for high-speed operation and can be further combined with a vacuum tube to achieve higher speeds. The first high-speed HTSP maglev engineering prototype was developed and demonstrated in Chengdu, China, in 2021. However, the HTSP maglev systems face a series of challenges for engineering operation. On the other hand, insulation technology for superconducting power equipment and the instability of the rotor in superconducting electrical machines are challenges that also need to be overcome for their applications in railway systems. This paper also summarizes work conducted at Southwest Jiaotong University to address these challenges and develop practical implementations. It is believed that continued research and development will enable superconductors to play an important role in future railway systems. This development will help boost speed, reliability, and energy efficiency.