Performance Improvement of Superconducting Tapes Due to Ferromagnetic Cover on Edges

Improvement of critical current and reduction of AC loss is presented for a common multifilamentary Bi-2223/Ag tape with thin nickel layer electroplated at the edges. Numerical calculations using a commercial finite-element code have been carried out to find the distributions of electrical current and magnetic field when the whole section is filled with the critical current density. The dependence of critical current density on local magnetic field and its orientation was taken into consideration, allowing to understand the mechanism of I_c increase. Optimization of the cover thickness and width would be possible due to these calculations. AC loss was investigated experimentally in the condition of AC transport and simultaneous action of AC magnetic field in phase with transport current. Reduction of both the transport loss and the magnetization loss has been observed, as well as the loss at simultaneous action of transport AC and applied AC field.