Current Transmission and Resistance Characteristics of Bridge Joints in Three-Phase Coaxial Superconducting Cables

In the design and manufacturing process of intermediate joints for three-phase coaxial superconducting cables, optimizing the joint structure and minimizing resistance loss are essential to improving transmission efficiency and long-term stability. However, the concentric connection of superconducting functional layers of all three phases at the intermediate joint creates a resistance-concentrated region, leading to higher thermal loads and increased quenching risk. Currently, most research on superconducting tape joints focuses on lap joints. However, for the connection of the superconducting layer in intermediate joints, bridge joints are more advantageous. Bridge joints can address the issue of reversed tape orientation that often occurs in lap joints, enabling a more symmetric current transmission path. Thanks to their symmetrical structure and flexible welding orientation, bridge joints are better suited to meet the integrated performance requirements of joints in complex systems. This design facilitates compact system layouts and is more appropriate for large-scale industrial deployment in complex installation environments. Through experimental and simulation analysis of the current transmission behavior and resistance-influencing factors of bridge joints in three-phase coaxial superconducting cables, this study reveals that the current transmission efficiency in the superconducting layer bridge joint region is directly related to the geometric configuration of the joint. Among the configurations, the face-to-face design demonstrates superior current-carrying capacity due to its more direct current transmission path. This research provides theoretical guidance for optimizing the design of superconducting joints and improving the stability and performance of superconducting cables in practical applications.