Dr Sastry Pamidi (The Florida State University, Center for Advanced Power Systems)
AC losses in YBCO coated conductor tapes are one of the major heat load on the cryogenic systems in HTS cables, fault current limiters, and transformers. To reduce AC losses in tapes made using RABiTS process, a nonmagnetic substrate is being developed. Coated conductor tapes designed and manufactured using the new substrate have been characterized for critical current density and transport current losses at several temperatures between 63 and 77 K. Self-field critical current and transport current loss measurements were performed on several tape sections with the new nonmagnetic substrates and compared with regular RABiTS tapes. 4 mm wide tapes laminated by brass on both sides were measured. Temperatures below 77 K were achieved by pumping on liquid nitrogen and the temperature was controlled using a resistive heater and temperature controller. Loss measurements were performed at several frequencies in the 10 - 400 Hz interval. Critical current of the tape sections measured by standard four probe method was in 140 - 160 A range in the self-field at 77 K, and lowering of the temperature by 10 K the critical current increased by factor of two. Transport current losses were measured using a lock-in technique with compensation of inductive components. Measured transport current loss data were compared with Norris strip model. Results of the critical current and AC losses of the coated conductor samples with the new substrate will be discussed.
Jozef Kvitkovic (Florida State University, Center for Advanced Power Systems)