Experimental Evaluation of Longitudinal AC Losses in Superconducting Multifilamentary Wires for 50/60Hz Use

AC Losses in a Spatially Periodic Magnetic Field Longitudinal to the Wire

Abstract

In multiply-twisted superconducting cables in a transverse external magnetic field, the strands of multifilamentary wires are exposed to a spatially periodic field component longitudinal to the strand axis. It is predicted theoretically in 50/60Hz region that the AC loss of the wires for the longitudinal component is not neglected or comparable with that for a pure transverse field in the multiply-twisted cables with cabling pitches of several cm and more. In the present paper, the AC loss in the spatially periodic longitudinal field was experimentally evaluated by means of measuring electromagnetically the AC loss of short multifilamentary wires in a 60Hz uniform longitudinal one. It results from a theoretical consideration that the above two types of losses are equivalent to each other within errors of 5%, where the sample length corresponds to a half of the wavelength of the field. The measured loss was quantitatively explained by the theoretical expression for spatially periodic longitudinal field above mentioned. These results suggest that the AC loss in the cables for AC use should be minimized under consideration of the longitudinal loss in addition to the usual transverse losses.