抄録
When an a.c. transport current and/or an a.c. magnetic field are applied to multiply-twisted superconducting cables, magnetic field along strands composed of homogeneous and spatially periodic ones is induced in addition to the field perpendicular to the strands. The time variation of this longitudinal field along the strands also brings about the hysteresis and coupling-current losses. Theoretical expressions for the additional losses are derived both in the self-field configuration of the cable and in the external-transverse-field one. In the self-field configuration, the hysteresis loss due to the homogeneous component is dominant, which can be sufficiently decreased by the cabling procedure and the optimization of twist pitch in the strand. In the external transverse field, on the other hand, the development of high-current-density superconductors may be necessary for decreasing the losses in the a.c. cables in addition to optimization of the cable structure.
