Development of a 1 MVA 3-Phase Superconducting Transformer Using YBCO Roebel Cable

We present design details for the planned construction of a 3-phase 1 MVA 11 kV/415 V transformer using YBCO Roebel cable (YBCO-Yttrium Barium Copper Oxide second generation high temperature superconducting coated conductor). The YBCO Roebel cable is a promising technology for carrying high currents. It simplifies manufacture of the winding while managing AC loss. We present the transformer winding design which follows a simple layout with the low-voltage windings utilizing a 15 strand × 5 mm (15/5) Roebel cable in a single-layer 20 turn solenoid. The target rated current capacity of the cable is 1500 A rms at 77 K. The high-voltage winding will be in the form of a stack of double pan cake coils arranged on a composite former outside the low-voltage windings. The coils will be immersed in sub-cooled liquid nitrogen with a target maximum operating temperature of 70 K. The development methodology is described along with the results of experiments and modeling to validate the performance characteristics of the windings.