AC LOSSES IN HIGH T-C SUPERCONDUCTORS

The losses in high T-c conductors do not differ in principle from those in low T-c materials, and the same calculations can be used. However it is necessary to allow for the granularity of the materials and the high aspect ratio of the conductors. This paper derives simple, if approximate, expressions for calculating the losses in the most important cases for practical purposes. These are the use of BSCCO tapes in magnets and cables at power frequencies. The predictions of elliptical and thin strip models are compared and it is found that an elliptical geometry agrees best with the experimental results. It is also found that the the voltage measured in a transport measurement depends on the position of the contacts and that if an unambiguous loss measurement is required it is,necessary to include the flux outside the sample in the voltage measurement loop.