Modelling of the influence of magnetic screening on minimisation of transport AC losses in multifilamentary superconductors

Numerical modelling was used to investigate the effect on transport ac losses of decoupling the filaments in superconducting tapes by magnetic screening. Both multifilamentary Bi-2223 tapes and multifilamentary YBCO coated conductors were modelled. Different configurations of multifilament geometry with filaments covered with ferromagnetic materials of different thickness and different magnetic permeability were considered. Calculations of ac loss reduction and critical current increase in the presence of a magnetic material with nonlinear magnetisation characteristic were conducted for selected configurations. A comparison with the previous results of a perfect screening was made. Some experimental results on influence of the presence of magnetic material on critical currents and ac losses are also discussed.