I. Introduction
The winding of a superconducting transformer can be made as a set of pancake coils connected in series or as a helical coil. “Practical advantage of the first solution is that in the case of an accidental local damage of the tape one has to replace just the corresponding pancake coil. Composition of the coil from pancakes can be optimized comfortable and with emphasize on economy. On the contrary, in helical approach, a wrong piece of the conductor within the winding inevitable disables the winding as a whole. Good parts of the conductor are lost. Furthermore, the conductor in the helical coil is more deformed. At the coil ends the tape is also slightly bent in the tape plane. In helical windings there are no resistive contacts as it is the case in pancake coils. There is also a difference in the local distribution of magnetic field of the winding within individual turns. The behavior of radial component B, is crucial. This component is perpendicular to the tape plane and governs the local value of the critical current [1], [2]. [3]. In comparison with the helical winding the pancake configuration is expected to have different distribution of B, not only in the vicinity of winding flanges but also in gaps between pancakes.