Investigations on Different Joining Techniques Regarding Electrical Joints With Normal Conducting Material and YBCO Coated Conductors

Abstract

Due to the further development of metal-coated thin-film high-temperature superconductors (HTS) that operate at the temperature of boiling liquid nitrogen (LN 2 ,-195,8°C) a wide field of applications in superconducting fault-current limiters, generators, or motors arises. To apply HTS in these devices, stable electrical joints between normal and superconducting materials, as well as joints between HTS, are needed. To develop and evaluate these electrical joints, it is necessary to measure and investigate the electrical (e.g., contact resistance and power loss), thermal, and mechanical behaviors of the conductors themselves and their joints at the temperature of LN 2 . This paper presents and evaluates three different joining techniques to establish an electrical joint for low temperature applications. Therefore, a low temperature test rig was built up which provides the possibility to simulate network conditions from normal operation to fault conditions. This paper describes the design, mounting, and implementation of the test rig, including the arrangement and adaptation of the measurement system. After the presentation of the selected joining techniques, the electrical joints with normal and with YBCO-coated superconductors are established. The different joining techniques will be evaluated according their usability at low temperatures.