Apparent ac losses in helical BiPbSrCaCuO-2223/Ag multifilamentary tape measured by different potential taps at power frequencies

Transport ac losses in BiPbSrCaCuO-2223/Ag multifilamentary tape in form of a helix with a 3 mm gap between the turns were measured in frequency range 40-125 Hz. Different positions of potential taps on outer and inner surface of the tape were used. Potential wires were led along the tape axis as well as along the axis of the helix. At currents lower than the critical current a strong dependence of measured apparent ac losses on potential taps position and on the form of potential wires was found, Suitably wound contact-less pick-up coils to detect magnetic flux of different magnetic field components were also used. They allowed us to measure the 'magnetisation' part of apparent losses even when the sample was in resistive state, as well as the losses at the gap of the tape. Comparison of the losses at the gap of the tape with the existing theoretical model was made. (C) 1999 Published by Elsevier Science B.V. All rights reserved.