Basic Research On Ac Loss Of High Temperature Superconducting Armature

High Temperature Superconductor (HTS) is an new electrical material which has been used in several fields. Although superconductor can transport dc current without any losses, dc current or alternating magnetic fields will cause energy dissipation (ac loss) in superconductors. So, it restricts the application of HTS in some way. In recent years, it has become a very hot research topic to introduce HTS technology to motors. Different from conventional HTS synchronous motors which use HTS as the field coils, the one mentioned in this paper has a new structure with the HTS armature winding. In this situation, the HTS transports ac current under the ac external field. It is important for us to calculate ac loss for designing our HTS motor.Firstly, we give an overview of ac loss mechanism and classify it. The computational methods under different conditions will be discussed, which include transport loss, magnetisation loss in a perpendicular ac magnetic field, ac loss of dc current in ac magnetic field and ac current in ac field. Besides, a common numerical caculation model also be explained.The producer of superconductor tape adopt a new technology which use a ferromagnetic substrate to reduce ac loss. Based on this idea, we introduce the similar structure in our HTS armature winding. Due to the analysis of finite element model, we compare the normal component field on the broad tape before and after using ferromagnetic material.We present a new method to predict the ac loss of HTS armature winding by combining analytic computation and analysis of magnetic field in the slot of motor with FEM software. The upper and lower limits of ac loss in armature winding will be obtained. For the measurement of ac loss, different methods have been discussed and compared. In this article, we adopt electromagnetic method to measure the ac loss of HTS tape. Then experiment principles will be explained. Finaly, we will measure ac loss.