Design and loss calculations of a 100-kVA transformer employing multi-filamentary Bi-2223 Ag sheathed superconducting tapes

摘要

A dimensional analysis for the design of a 100 kVA, 3 phase, iron core, 6.6 kV/240 V, Wye-Wye connected transformer employing Ag sheathed Bi-2223 high-temperature superconducting (HTSC) multi-filament tapes has been carried out. The mass, volume and tape length requirements were calculated over a range of core cross-sectional areas. The objective of this exercise was to minimize the overall transformer volume. A range of suitable designs was then selected. Finite element methods software was used to map the magnetic fields throughout the winding volume of each design, and to estimate the hysteretic loss at full load. The analysis of mass and volume with core area variation showed the presence of distinct points, which would minimize these quantities. However, it was found that these designs were impractical in reality due to the significant length and cost of tape that they would entail. It was also shown that the coil electrical losses in these designs were too high due to the length of tape required and from the higher hysteretic loss. By considering the factors of mass, volume, hysteretic loss, and tape length and cost, a suitable design was found which was a compromise between all the factors involved. Assuming HTSC tape available with a modest J_e of 5000 A/cm~2, it was found that the mass and volume of the transformer could be reduced significantly compared to that of a conventional transformer. The volume decreased from 206 to 129 dm~3 and the dry mass decreased from 400 to 214 kg. The overall hysterises loss at full load was calculated to be 1290 W and the total length of tape required per phase is 1500 m. The minimum possible volume of the transformer for the given rating and engineering current density was found to be 83.8 dm~3 requiring 3508 m of HTSC tape.