Design of a 1 MVA high TC superconducting transformer

A 1 MVA transformer using BSCCO-2223 high Tc superconducting (HTS) tapes was designed. The rated voltages of each sides of the transformer for primary and secondary are 22.9 kV and 6.6 kV respectively. Double pancake HTS windings, which have advantages of insulations and distribution of high voltage, were adopted. Four HTS tapes were wound in parallel for the windings of low voltage side. Each winding was composed of several double pancake windings and four parallel conductors of secondary winding were transposed in order to distribute the currents equally in each conductor. The core of the transformer was designed as a shell type core made of laminated silicon steel plate and the core is separated from the windings by a cryostat with a room temperature bore. Configuration of the cryostat made of nonmagnetic and nonconducting material and a liquid nitrogen sub-cooling system were used in order to maintain the coolant's temperature of 65 K.