Design, development, and testing of a 6.6 MVA HTS traction transformer for high-speed train applications

Abstract

High-temperature superconducting traction transformers (HTSTT) have the merits of small size and lightweight in comparison with their conventional counterparts. This article reports the development progress of a 6.6 MVA HTSTT operating at 65 K, including the design, testing, and system cooling. The introduction of flux diverters and an optimized winding design realized a short-circuit impedance higher than 43% and AC loss less than 3 kW. The insulation structure was designed to pass insulation tests specified in standard in China GB/T 25120-2010. An open cooling system with reduced pressure was developed, which realized the efficiency of the 6.6 MVA HTSTT above 99%. Before assembling the prototype transformer, we conducted tests for critical current and dielectric performance of the HTS double pancake coils (DPC) used in high-voltage (HV) and low- voltage (LV) windings to verify the current-carrying and insulation performances of each DPC. Finally, we measured the critical current and no-load loss of the HTSTT prototype at 77 K. Test results showed that the mass of the transformer is 33% less than conventional transformers. At 77 K, the critical current of the LV winding and HV winding is higher than 700 A and 50 A, respectively. Moreover, the HTSTT on a no-load test reached the test voltage of 25,000 V and loss of 6 kW. In the next step, we will continue to conduct experimental research, and verify the feasibility of the HTSTT on the train, and develop a circulating cooling system, all meeting the commercial requirements of the HTSTT. 

Experimental AC loss study on REBCO coil assemblies coupled with an iron cylinder

“…Using iron cores to achieve effective energy transfer and high magnetic field is common in high-temperature superconducting (HTS) power devices, particularly in transformers [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15], fault current limiters [16][17][18][19][20][21], and rapid-cycling synchrotrons [22,23]. For these superconducting applications, AC loss in superconductors caused by the motion of flux lines when carrying alternating currents or when exposed to magnetic fields remains a critical issue [21][22][23][24][25], as it poses challenges for cooling systems.…”