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

A theoretical model of twisted multifilamentary superconducting tapes was developed 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 property is represented as equivalent conductivity. The electric field-current density characteristic of superconductor is given by a power law, and a dynamic resistivity is also taken into account in the equivalent conductivity. The twisted structure is represented by a tensor equivalent conductivity. The model enables us to estimate ac losses under the condition that the superconducting tape carries ac in ac magnetic field, which is the most possible and general circumstance for the superconducting tapes in practical power apparatuses. This model was applied to finite element analysis to calculate the ac loss in a high T-c multifilamentary superconducting tape. (C) 1999 American Institute of Physics. [S0021-8979(99)04108-0].