Power losses of 2 G HTS coils measured in external magnetic DC and ripple fields

Abstract

Power losses are an important phenomenon in 2nd type superconductors. Precise evaluation of power losses in superconducting coils is crucial for the design of novel machines such as superconducting motors or generators. Although AC losses are relatively easy to measure with electrical methods, it is more difficult to measure power losses in the DC mode, induced by varying external magnetic fields, such as occur in a real operating environment. Especially the problematic one could be the direct-drive wind generator, where several elements introduce nonsynchronous disturbances to the magnetic fields. Modelling had been carried out by numerous authors1-4 in order to estimate the power losses in 2G HTS coils under various external DC or ripple fields; however experimental work in the area is less common due to the difficulty of conducting experiments and special equipment requirements. In this paper, power losses are experimentally measured by the calorimetric method.