千匝量级高温超导YBCO磁体交流损耗的仿真分析

Simulation analysis of AC loss of HTS YBCO magnet with thousands of turns

高温超导YBCO带材严重的各向异性,使得YBCO磁体的交流损耗特性比BSCCO磁体更加复杂。利用有限元方法研究了匝数多达1000匝的YBCO磁体的交流损耗特性。该方法基于H方程,考虑了YBCO带材与磁场强度和方向相关的临界电流密度以及高温超导体高度非线性的E-J关系。由于磁体匝数众多,采用均质化bulk近似方法简化了磁体建模,加快了计算速度,并以200匝带材组成的双饼为例,对比均质化Bulk模型和考虑超导层实际尺寸的参考模型,验证了该方法的可靠性。此外,还详细分析了不同传输电流上升率、幅值以及带材的n值和临界电流等参数对YBCO磁体交流损耗的影响。

The AC characteristics of YBCO magnets are more complicated than that of BSCC0 magnets owing to serious ani- sotropy of YBCO tapes. In this paper, the AC loss characteristics of an YBCO magnet with 1000 turns were studied based on FEM method. This method was based on H formulation, in which the field - dependent critical current density and high nonlinear E - J characteristics were considered. For the reason of that the total number of turns was up to 1000, a homogenized bulk approxima- tion was used to simplify the modeling and speed up the computing. We validated the anisotropic bulk model by comparing the AC loss of a double pancake coil consisted of 200 turns between bulk model and reference model which considered the actual thick- ness of the superconducting layer. In addition, the AC loss dependence on current ramping rate, amplitude and n - value and crit- ical current of YBCO tapes were analyzed in detail.