3S–Superconducting DC-Busbar for High Current Applications

Within a German government funded project a superconducting (HTS) high current DC-busbar is under development. The aim is the fabrication of a demonstrator with a length of 25 m and a nominal current of 20 kA for installation and test in an industrial real-life application. The concept is a modular system with rigid superconducting elements of arbitrary length, straight or with defined bends, each equipped with own cryostat and premanufactured in the factory. These elements can easily be transported, but have to be joined on the installation site. To manufacture such elements several issues had to be addressed: The arrangement of the superconducting tapes was optimized with respect to the minimization of the magnetic self-field effects. The thermal contraction of the busbar had to be balanced and in particular low-resistance joints between the superconducting elements had to be developed. These are based on innovative comb-shaped structures with face-to-face soldered tape ends. A first prototype of such an element including two joints was built and tested at T = 77 K up to an effective current of I = 20 kA. With a resistance of less than R = 0.5 nΩ, the losses from the contacts are small compared to the cryostat losses.