Frequency dependence of ac transport loss in Bi-2223/Ag tapes

The AC loss of various silver-sheathed high Tc superconducting Bi-2223 tapes is measured by means of the transport method, as a function of frequency and current amplitude. The frequency dependence of the power loss (in W/m) is used to separate different loss components: the frequency independent part is attributed to the resistive loss, the linear part to the hysteresis loss (self-field loss in J/m per cycle), and the quadratic part, if it appears, may be assigned to other losses such as the eddy current loss. The separated loss components are evaluated with the existing models and the DC voltage-current characteristics of the sample. In general, the self-field loss is dominant when the transport current amplitude is smaller than the critical current of the tape. For larger currents the resistive loss is the most important component. At small transport current, the AC transport loss signal is very small and is sensitive to the phase correction and other disturbances from the surrounding metallic parts in the vicinity of the sample. The signal picked-up from these disturbances shows the quadratic frequency dependence.