Magnetisation loss in stacks of high-T-c superconducting tapes in a perpendicular magnetic field

Magnetisation loss is an important factor in the design of superconducting transformers and motors. In these devices the tapes are usually placed face -to-face. Then the magnetisation loss is influenced by the mutual magnetic shielding between adjacent tapes. The shielding is investigated by measurin g the magnetisation loss in stacks with various numbers of Bi-2223 tapes, e xposed to a 48-Hz perpendicular magnetic field at 77 K. In a stack the pene tration field is increased and the magnetisation loss below penetration is greatly decreased, compared to the behaviour of a single tape. The loss at high magnetic-field amplitudes is unaffected. The measured loss is compared to the loss calculated with two different models. The effect of shielding is qualitatively well described with an analytical model. However, predicti ons made with a numerical model display a better quantitative agreement wit h the measurement results. (C) 2001 Elsevier Science B.V. All rights reserv ed.