Design and Manufacturing of a Multistage Cooled Current Lead for Superconducting High Current DC Busbars in Industrial Applications

There is a high potential to use high-temperature superconductors instead of conventional busbars in high direct current industrial applications. Since current leads are typically the major source of losses in these applications, we investigate a multistage cooled current lead to operate at a current of 20 kA minimizing current lead losses. The design seeks to realize an efficient and at the same time economic current lead consisting of components which are market proven and reliable. The current lead operates from 300 to 77 K and is cooled with two intermediate cooling stages at 240 and 150 K. One key component is the joint between the resistive copper part and the YBCO high-temperature superconductor tapes, which is manufactured by a new soldering process. Moreover, electromagnetic finite element analyses of a high-temperature superconductor stack design have been done to optimize the current carrying capacity of the current lead. As a result, the multistage cooled current lead is designed to cryogenic losses of 22.4 W/kA at 77 K.