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

TL;DR

This paper presents a numerical model for analyzing magnetic flux penetration and AC loss in composite superconducting wires with ferromagnetic parts, validated by experiments showing reduced AC loss.

Contribution

The authors develop a new numerical approximation to the critical state model that accounts for non-linear magnetic materials and field-dependent critical current density.

Findings

Good agreement between model and experiments

Significant AC loss reduction observed

Model applicable to commercial finite element codes

Abstract

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