Energy loss study for AC excited superconducting coils

点击翻译按钮获取中文摘要

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.