In multiply-twisted superconducting cables exposed to an external a.c. transverse magnetic field, a component of the magnetic field parallel to the strand axis brings about an additional a.c. loss (longitudinal field loss) in the strands. We have experimentally evaluated the longitudinal field loss in two types of triply-twisted superconducting cables composed of insulated strands with different diameters, by eliminating the hysteresis loss and the transverse coupling-current loss from the total loss in the strands. The evaluated longitudinal field losses were quantitatively explained by a theoretical expression obtained, to date, from consideration of the effects of the longitudinal component of the applied field on the strand. The present results suggest that the longitudinal field loss can be dominant in an a.c. magnetic field with relatively large amplitude. To minimize the total loss of the strand in the multiply-twisted cables, an optimum condition for the twist pitch of the strand was discussed.
All Science Journal Classification (ASJC) codes
- General Materials Science
- General Physics and Astronomy