A Superconducting DC Traction Substation kW-scale Prototype

This work investigates the feasibility of a superconducting DC railway traction substation in which the conventional transformer, diode rectifier, and copper cables are replaced by a partially superconducting transformer, a cryogenic diode rectifier, and superconducting cables. A 3 kW prototype DC traction substation was designed, assembled and experimentally characterized. System performance, encompassing electrical efficiency (i.e., not including the cooling penalty), was evaluated, providing insights into the behavior of each superconducting component compared with its conventional counterpart. The transformer employs a copper primary winding at room temperature and a high temperature superconducting secondary winding operating at 77 K, eliminating the need for bulky terminations. The proposed design successfully operated and exhibited higher efficiency compared to its conventional equivalent. The cryogenic diode rectifier, based on selected commercial diodes, demonstrated higher efficiency than the room-temperature version on a large operating range. The high temperature superconducting cables operated without any measurable losses under rectified load current conditions. Overall, the results confirm that the superconducting system operated as intended, suggesting possible gains in compactness and electrical efficiency compared to conventional DC traction substations.