Contactless Loop Method for Measurement of AC Losses in HTS Coils

Measurements of ac losses in high-temperature superconducting (HTS) coils are of utmost importance for power applications because these are one of the most limiting factors in superconducting devices. There are two possible ways to measure such losses: calorimetric and electromagnetic methods. An electromagnetic method using a contactless loop is reported in this paper. To verify the applicability of such method in medium- to large-sized coils, two different contactless loops were designed and built, and results are compared with those obtained from measurements made with different configurations of voltage taps. All tests were performed at 77 K, using a superconducting coil with a variable number of turns (up to a maximum of 128) wound from BSCCO tape. Currents ranging from zero to the critical value were applied, at frequencies from 72 to 1152 Hz.