Study on Stability of Superconducting Cables for AC Application

1. 基于三维有限元法和分布式电路开发了一套计算机程序，模拟了三股超导电缆的瞬态行为，包括钢绞线和钢绞线内部的温度演变以及钢绞线之间的电流分布。重点研究了铜基体对暂态稳定性的影响。根据本项目的研究结果，为交流用高稳定超导电缆的设计和研制提供了指导。本文设计并构建了具有超导初级绕组的圆柱型直线感应电动机模型，阐明了交流超导绕组在旋转电机实际运行环境中的行为（交流损耗、稳定性等）。研究了超导绕组的基本工作特性，如推力特性和电磁特性等。优化了一次绕组的电流分布，提高了电动机的推力特性，并提出了一种新的超导电机熄火保护电路。提出了采用GM制冷机传导冷却系统的高温超导体磁体技术。本文采用GM制冷机对高温超导带（Bi-2223/Ag、Bi2212/Ag带）的传导冷却特性进行了测量，并开发了基于有限元的计算机程序来研究高温超导带的热学和电磁行为。利用模拟程序，讨论了低温冷却器冷却的高温超导线圈的稳定性判据。根据GM制冷机冷却功率与高温超导盘管内发热量的关系，选择发生“热失控”的电流作为稳定性判据。我们还研究了高温超导线圈在淬火过程中的瞬态热和电磁行为，以确定实际操作中的热和电流裕度。少

1. Transient stability of multi-strand superconducting cablesWe developed a computer code based on 3D funite element method and a distributed circuit to simulate transient behaviors of three- strand superconducting cables such as temperature evolution in strand and cables, and current distribution among strands in quench process. Especially, we focused on the effect of cupper matrix on the transient stability. From these results obtained for the term of this project, the guideline for the design and development of highly stabilized superconducting cables for AC use.2. Development of superconducting cylindrical linear induction motorWe have designed and constructed a model cylindrical linear induction motor (SCLIM) with superconduting primary windings to clarify the behaviors (AC loss, stability and so on) of AC superconducting windings in a realistic operational environment of electrical rotating machines. The fundamental operational properties such as thrust characteristic and the ele … More ctro-magnetic and mechanical phenomena in the superconducting windings were investigated. And we optimized the current distribution in primary windings to enhance the thrust characteristic and proposed a newly quench protection circuit for a realistic operation of superconducting electrical machines.3. Stability Criterion for Cryocooler-cooled HTS CoilsMagnet technology of high-temperature superconductor (HTS) with conduction cooling system by GM cryocooler have been advanced. We have measured the quench characteristics of HTS tapes (Bi-2223/Ag, Bi2212/Ag tapes) with conduction cooling system by GM cryocooler and developed a computer program based on the finite element to investigate the thermal and electromagnetic behaviors within HTS tapes. Using the simulation code, we discussed a stability criterion for cryocooler-cooled HTS coils. The current at which "thermal runaway" occurs, depends on the relationship between the cooling power of GM cryocooler and heat generation within HTS coils, is chosen as a stability criterion. We also investigate the transient thermal and electromagnetic behaviors in HTS coils during a quench process to determine the thermal and current margin in a realistic operation. Less