Test results of 14 kVa superconducting transformer with Bi-2223/Ag windings

Single phase 14 kVA, 400 V/200 V superconducting transformer with Bi/2223/Ag winding immersed in liquid nitrogen and with laminated ferromagnetic core was designed and manufactured. The core of the transformer was at room temperature, both windings were placed in a nonmetallic toroidal cryostat. The aim of the work was to verify the calculated values of critical currents and AC losses in primary and secondary windings which were based on short sample measurements. Standard short circuit test, open circuit test and load test were performed and evaluated. To reduce AC losses of primary and secondary winding laminated ferromagnetic rings attached to both ends of the windings were designed. Their influence on the radial magnetic field component in the windings was computed. The resulting effect of the rings on AC losses was verified experimentally. The issue of AC losses is discussed in another contribution of these proceedings. The residual basic parameters are presented here.