Magnetic flux penetration and AC loss in a composite superconducting wire withferromagnetic parts

Abstract

The current distribution and the AC loss in a composite superconducting tape containing alayer of magnetic material is calculated and compared with experiments, showing a verygood agreement. The situations of an alternating uniform applied field or a transportcurrent are studied. The newly developed numerical model is an approximation to thecritical state model, adapted for applicability to commercial finite element codes that solvethe vector potential. A substantial feature of this procedure is that it can be carried out inthe case when the critical current density in the superconductor depends on the magneticfield and the magnetic layer material is nonlinear. Additionally, the hysteresis loss inthe magnetic material is estimated, based on its measured magnetization loops.Measurements on Bi-2223 multifilamentary tapes covered on edges by nickel confirmed ourpredictions, showing a substantial ac loss reduction in both the investigated regimes.