Effective transverse resistivity in superconducting tapes with various filament shapes and structures

When a multi-filamentary superconductor is exposed to an alternating extern al magnetic field, coupling-current loss is a significant part of the magne tization loss. The coupling-current loss at low magnetic-held frequencies i s determined by the effective transverse resistivity of the inner filamenta ry region. The effective resistivity is calculated for various shapes and s tructures of the inner filaments. Bi-2223/Ag tapes typically have filaments with a high aspect ratio, causing an anisotropic transverse resistivity. W hen there is no contact resistance between the filaments and the matrix mat erial, the presence of the filaments decreases the effective resistivity. T he decrease is greatest for overlapping filaments whose wide sides are orie nted parallel to the external magnetic held. Good insulating barriers resul t in a high contact resistance from the filaments to the matrix. Then the e ffective resistivity is greatly increased, especially for overlapping filam ents that are oriented perpendicularly to the magnetic held. The results ar e relevant for the calculation of the coupling-current loss in Bi-2223 tape s with twisted filaments.