Design and construction of a 41 kVA Bi/Y transformer

High Temperature Superconducting (HTS) materials bring to transformers benefits such as weight reduction and improvements in efficiency as well as the electrical behavior in the network. In the context of a European project (READY) we designed and built a 41 kVA single phase transformer that will use the first lengths of YBCO coated conductors for the secondary winding. Project partners are developing this conductor. The primary winding uses a PIT-Bi2223 tape and we designed the transformer as a complete device with integrated cooling. The refrigerator is a large cooling capacity (100 W at 80 K) single stage coaxial pulse tube cooler developed by Air Liquide. We chose a cold magnetic circuit with low iron loss laminations. The cryostat is then very simple with metallic vessels and only one interface with the refrigerator. The cooling fluid is helium in order to investigate a large temperature range (40-80 K). Thermal simulations were made to minimize heat transfers to the HTS conductors and experiments provided some necessary data. The transformer design and optimization is presented as well as its construction.