Modeling of magnetic properties and alternate current losses in high-Tc superconductors using a power law voltage-current characteristic

This article presents numerical diffusion models which describe the electromagnetic properties and alternate current (ac) losses of a high-T-c superconducting tape carrying transport current. The models simulate the tape as a highly nonlinear conductor with equivalent resistivity being a function of J, the local current density, as deduced from a power law E-J characteristic of the material. The power law E-J expression can be adjusted by varying both the power, alpha, and the value of the critical current density, J(c), to accurately fit the current-voltage characteristic of a given high-T-c superconducting tape, as obtained from direct current measurements. Results of various field quantities, in the interior of the tape, and losses for a range of ac currents and frequencies are presented and discussed in conjunction with the critical state, flux creep, and flux flow theories of high-T-c materials. (C) 1999 American Institute of Physics. [S0021-8979(99)25008-6].