Alternating-current transport losses of Ag-sheathed (Bi, Pb)(2)Sr2Ca2Cu3Oxmonocore round wires and tapes

Ag-sheathed (Bi, Pb)(2)Sr2Ca2Cu3Ox monocore round wires and tapes with diff erent core geometry have been fabricated by a powder-in-tube method. The al ternating-current transport losses of these wires and tapes were measured a t 77 K as a parameter of frequency between 50 and 1000 Hz in a self-field. The round wires have lower transport losses than the tapes in the investiga ted frequency range, even in the cases of nearly the same critical currents . The hysteresis loss for the wires is derived from the experimental data a nd found to be well below the prediction for a thin-strip superconductor. T his is attributed to the inhomogeneous J(c) distribution in a radial direct ion in the core, which is expressed as a sharp rise of J(c) in going from t he core centre to the interface with the Ag sheath. An increase in frequenc y enhances the loss generation in the round wins because of significant edd y-current loss. In the tape samples, an increase in the aspect ratio accomp anied by significant core deformation raises the loss value, so that it app roaches the value predicted for an elliptic superconductor tape.