Energy loss study for AC excited superconducting coils

该项目是为了研究交流励磁超导线圈的能量损失。使用超导胶带缠绕成线圈是高温超导最有效应用的一个共同特点。然而，这些磁带对由垂直于磁带横截面宽度的时变磁场产生的交流损耗高度敏感。这给交流线圈的设计带来了一些限制，特别是电机中的定子绕组。在实际应用中，我们有一个交流电和直流电磁场的组合作用在线圈上，而线圈又有直流或交流传输电流。此外，磁场不是均匀的，甚至不是正弦的，电流也是如此。在大本底磁场或电流的作用下，磁场和输运电流的小波纹效应是高温超导电机和发电机非常关注的问题，但还没有得到详细的研究。我们强调了研究特定系统磁场和电流的真实配置中线圈的重要性。在这种情况下，实验测量可能比建模更可靠。我们将使用液氮汽化和电学技术对高温超导线圈进行实验研究，这些结果将用于验证描述线圈的数值模型。我们相信，这种方法的组合将为实际用户系统提供一个可靠的线圈性能表征系统。作为这项工作的输出，我们将拥有：(I)磁带相关参数与整体线圈性能之间相互联系的实用知识；(Ii)用于确定线圈能量损失的可靠实验技术；(Iii)作为大型电机设计和建造的数据源的经验证的线圈模型。

The project is for energy loss study for AC excited superconducting coils.The use of superconducting tape wound into coils is a common feature of the most effective applications of HTS. However, these tapes are highly sensitive to AC losses produced by time-varying magnetic field perpendicular to the cross-sectional width of the tape. This imposes some constraints upon the design of ac coils particularly for stator windings in electrical machines. In real applications, we have a combination of AC and DC magnetic fields acting on a coil that, in turn, has DC or AC transport current. Moreover, magnetic fields are not uniform and not even sinusoidal and the same is true for currents. This effect of small superimposed ripples of magnetic field and transport current in the presence of large background field or current is a great concern for HTS motors and generators and it has not been studied in detail. We stress the importance of studying coils in real configurations of magnetic fields and currents for particular systems. In this case, experimental measurements are likely to be more reliable than modelling.We will study HTS coils experimentally using both liquid nitrogen boil-off and electrical techniques and these results will be used to validate numerical models describing coils. We believe this combination of methods will deliver a reliable system for characterising the performance of coils for practical user systems.As the output of this work, we will have: (i) a working knowledge of the interconnection between relevant parameters of the tape and the overall coil properties; (ii) a reliable experimental technique for determining the energy loss in coils; (iii) validated coil models as a data source for the design and construction of large-scale electrical machines.