Quench transient current and quench propagation limit in pancake wound REBCO coils as a function of contact resistance, critical current, and coil size
Quench transient current and quench propagation limit in pancake wound REBCO coils as a function of contact resistance, critical current, and coil size
复制标题
扁平绕制 REBCO 线圈中的失超瞬态电流和失超传播极限与接触电阻、临界电流和线圈尺寸的函数关系
DOI：
10.1088/1361-6668/ab3081
复制
发表时间：
2019
影响因子：
3.6
通讯作者：
M. Bird
中科院分区：
文献类型：
--
作者：
W Denis Markiewicz;T. Painter;I. Dixon;M. Bird
人们普遍认为，无绝缘(NI)线圈技术是通向超高场超导线圈的一条途径。最近的经验表明，NI线圈设计的某些方面，如果不加以解决，可能会导致线圈故障。一个潜在的问题领域是与NI线圈中的失超传播相关的大暂态电流。为了了解并尽可能找到最小化失超瞬变造成损害的可能性的方法，进行了一项参数研究，以考察在NI线圈失超期间影响瞬变电流大小的因素。首先研究了暂态电流的特性。然后对一组测试线圈进行了研究，观察了失超传播和暂态电流大小作为接触电阻、临界电流和重要的线圈大小的函数。对于每个线圈尺寸，发现随着接触电阻的增加，失超暂态电流的大小减小，直到有效失超传播停止的条件，称为失超传播极限(QPL)。当接近QPL时，暂态电流的幅度减小，并且可以提供一种在线圈设计中可以有效地抑制失超引起的应力的区域。随着线圈尺寸的增大，与失超传播极限相关的接触电阻的值也会增加。在高场REBCO磁体所特有的大线圈尺寸下，QPL延伸到与裸导体之间观察到的值相比真正大的接触电阻值。为了增加接触电阻，需要在导线和同向风钢上使用电阻薄膜等方法。认识到这一发展，以这种方式实现的高接触电阻的使用被恰当地称为阻性绝缘线圈技术。
It is a general belief that no insulation (NI) coil technology is a path to very high field superconducting coils. Recent experience has shown that there are aspects of NI coil design that, if not addressed, can possibly lead to coil failures. One potential problem area is the large transient currents that are associated with quench propagation in NI coils. In an attempt to understand and possibly find ways to minimize the potential for damage from quench transients, a parameter study was undertaken to examine the factors that influence the magnitude of transient currents during quench in NI coils. The characteristics of the transient currents are first examined. A study is then made of a set of test coils, looking at quench propagation and the transient current magnitude as a function of contact resistance, critical current, and importantly coil size. For each coil size, it is found that as the contact resistance increases, the magnitude of quench transient currents is reduced until a condition where effective quench propagation ceases, called the quench propagation limit (QPL). As the QPL is approached, the amplitude of the transient current is decreased and may provide a regime where quench induced stress can be effectively contained in coil designs. As coil size increases, the value of contact resistance associated with the limit of quench propagation increases as well. At large coil sizes that will be characteristic of high field REBCO magnets, the QPL extends to truly large values of contact resistance compared to values observed between bare conductors. The use of methods such as resistive films on conductors and co-wind steel will be required to increase contact resistance. In recognition of this development, the use of high contact resistance achieved in this manner is appropriately called resistive insulation coil technology.