Superconducting DC busbar with low resistive joints for all-electric aircraft propulsion system

Abstract

High-temperature superconductors (HTS) can carry high currents with almost zero loss when transmitting direct current (DC). Their compact size and lower weight make them suitable for the application of all-electric aircraft. However, the current carrying capability of a single HTS tape is limited to a few hundred amps; therefore, for high-current applications, multiple HTS tapes need to be connected in parallel. The flat geometry of HTS tape and its critical current (IC) dependence on strain complicate grouping them in parallel. Furthermore, the length of HTS tape is limited by its crystal structure, necessitating low-resistance joints for extended applications. A superconducting busbar design for high-current applications is developed and tested to address these challenges. The superconducting busbar is designed in a way that it helps to reduce the effect of the self-field on critical current and also ride through the fault events. Yttrium barium copper oxide (YBCO) tapes are used to develop the busbar prototype, tested against DC currents in a liquid nitrogen environment. Joint optimization is carried out to determine the required length for efficiently joining HTS tapes. Two busbar prototypes are developed with 180° and 90° joints to join 5 HTS tapes and tested in self-field. A joint resistance of 100 nΩ is measured at self-field for the 180° joint busbar, and 800 nΩ is measured for the 90° joint busbar. Both busbar prototypes are subjected to power cycling and thermal cycling to assess joint performance in self-field and any degradation of the joint electrical parameters during testing.