Electromagnetic Design of High-Temperature Superconducting Traction Transformer for High-Speed Railway Train

A 6.6 MVA traction transformer made of high-temperature superconducting (HTS) wire is proposed in this design. The magnetic field, losses, and impedance are evaluated by finite element analysis. The dimension parameters and the structure of the windings are optimized based on the calculated field distribution. Tentatively, the design with the lowest field perpendicular to the surface of the HTS wire is selected to lower the ac loss. Bi-2223 (BSCCO) wires produced by Innova Superconductor Technology Company Ltd. (Innova) are considered for the primary (HV) and traction (LV) windings. From the Ic results measured at variable temperature and magnetic fields in short samples, the operation temperature is set to 65 K to improve the working current density. AC losses of the windings are calculated and optimized to achieve high efficiency and compact size. To further improve the efficiency, a six-wire transposed cable is designed. By stacking four such cables in parallel connection, the rated working current of LV windings can be up to ~850 A. Besides, a transposed pancake coil made of stacked wires/cables is also developed and numerically evaluated. Utilizing this design, a more efficient and safer highspeed train will be introduced to the railway transport in the near future.