Effect of the stack in HTS tapes exposed to external magnetic field

For large power applications, such as, HTS transformer, HTS motor and HTS power cable, stacked HTS tapes should be used because single HTS tape is limited in flowing of demanded current. Besides, insulation between layers is need for safe operation because high voltages are applied in those applications. The stacked HTS tapes have different characteristics compared with the single HTS tape because of screening effect. In this paper, we measured the magnetization losses in stacked HTS tapes of several samples having the various insulation thickness and various packing numbers of tape at 77 K. Properties of three different types of the stacks which consisted of 2, 3, and 4 tapes were measured and compared with that of single HTS tape. Also, numerical calculation by finite element method was done to compare with experimented data. Perpendicular magnetic fields were applied to the HTS stacks as external magnetic field. Results of measurement and calculation showed that magnetization loss of a stacked tape divided by stacking number of tape was smaller than the single tape's loss. This tendency was distinct as the distance between the tapes became closer and stacking number of tapes increased.