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

This article presents numerical diffusion models which describe the electromagnetic properties and alternate current (ac) losses of a high-Tc 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, a, and the value of the critical current density, Jc , to accurately fit the current–voltage characteristic of a given high-Tc 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-Tc materials