AC loss calculation on a 6.5 MVA/25 kV HTS traction transformer with hybrid winding structure

HTS wire cost is a critical factor for successful commercialization of HTS traction transformer technology. Wire cost might be minimized without significantly increasing AC loss by introducing a hybrid winding structure: the end-part of the windings is wound with high-cost high-I c wires; the central-part of the windings is wound with low-cost low-I c wires. We report AC loss simulation results on HTS windings with both HV and LV windings wound with REBCO wires. The 2D axisymmetric FEM simulation was carried out using H-formulation. The HV windings are wound with 4 mm-wide wires and LV windings are wound with 8/5 (eight 5 mm - wide strands) Roebel cables. Both HV and LV windings have a hybrid structure in order to reduce the wire cost. Flux diverters are placed at the end of the windings to reduce AC loss. Significant HTS wire cost reduction could be achieved without compromising AC loss by using hybrid windings. This may help commercialize HTS traction transformer technology