Theoretical model of twisted high T-c superconducting tapes for numerical alternating-current loss calculations

A theoretical model of twisted multifilamentary superconducting tapes was d eveloped for numerical estimations of alternating-current (ac) losses. The model consists of anisotropic Ohm's law representing the twisted structure [Banno et al., Proc. MT-15, 1140 (1998)], where the superconducting propert y is represented as equivalent conductivity. The electric field-current den sity characteristic of superconductor is given by a power law, and a dynami c resistivity is also taken into account in the equivalent conductivity. Th e twisted structure is represented by a tensor equivalent conductivity. The model enables us to estimate ac losses under the condition that the superc onducting tape carries ac in ac magnetic field, which is the most possible and general circumstance for the superconducting tapes in practical power a pparatuses. This model was applied to finite element analysis to calculate the ac loss in a high T-c multifilamentary superconducting tape. (C) 1999 A merican Institute of Physics. [S0021-8979(99)04108-0].