Eddy current self-field loss in Bi-2223 tapes with ac transport current
The a.c. self-field loss in Bi-2223 Ag and Ag-alloy sheathed tapes with different number of filaments has been measured in the range 59-2500 Hz by means of a dual lock-in amplifier technique. We have been able to dissociate quantitatively the different self-field loss contributions: hysteretic, eddy current and flux-creep resistive loss (near Ic) due to their different frequency dependence and the wide frequency range of the measurements. The relative weight of eddy current losses is found to be inversely proportional to the applied current ratio – the higher Ip/Ic, the less is their contribution. Shown are the frequency limits, beyond which eddy current loss has a significant and afterwards a governing contribution to the total a.c. loss in self-field. The distribution of power dissipation in the metal sheath is obtained by software simulation. A comparison has been made between the measured, simulated and theoretically calculated eddy current loss. Investigated is the effect of the sheath geometry and resistivity in reducing the eddy current loss in the measured and simulated tapes.