Compact stranded superconducting conductors with both low ac loss and high stability. I. Proposal of a new design Original Research Article

A new method for designing compact stranded superconducting conductors is proposed as a solution to the dilemma that low loss and high stability cannot be simultaneously attained in the commonly used conductors. In our design, the twist directions of the conductor and those of the sub-cables in it are the same. In addition, the twist pitch of the sub-cables is relatively longer than that of the conductor. The sub-cables crossover each other in the conductor. Under the changing transverse magnetic fields oriented perpendicular to the broad face of the conductor, the induced voltages between the above-mentioned crossover sub-cables become small, so inter-sub-cable coupling losses are decreased. As a result, not only the total coupling loss in the conductor is decreased, but also high stability is maintained due to the low contact resistance between the sub-cables. Our method theoretically indicates such high performance as attaining both low ac loss and high stability. An example of our design is shown for a large-scale compact stranded superconducting conductor.