Development of solenoid and double pancake windings for a three-phase 26 kVA HTS transformer

We prepared 6 coils from the stainless steel-enforced multifilamentary Bi2223/Ag tapes and studied their electromagnetic behavior for a three-phase 26 kVA (400 V/16 V, 37.5 A/937.5 A) transformer. The primary windings were solenoid coils consisted of 4 helically wound layers, and the secondary windings were consisted of 24 double pancakes connected in parallel with 3 layers, the strand of 6 windings was consisted of two parallel transposed multifilamentary tapes. A numerical analysis has been developed to predict the DC and AC behavior of the coils based on measurements of short samples and tested coils at 77 K. A comparison is made between the experiment and model calculation.