Ac loss in YBCO coated conductors exposed to external magnetic fields at 50-200 Hz

Ac loss measurements have been made on YBCO coated conductors in externally applied sinusoidal ac magnetic fields using the pick-up coil method. Various arrangements of YBCO coated conductor have been measured at frequencies of 50 Hz, 75 Hz, 100 Hz, 150 Hz, and 200 Hz, with amplitudes ranging from 0 to 140 mT. Three different sets of IBAD-based YBCO coated conductor were measured: (i) unfilamented conductors with Cu added either on one side only, or on both sides (as well as the edges), (ii) conductors with various numbers of filaments, (iii) 4 mm wide conductors. All samples were 4 cm long and untwisted. The total ac loss per cycle, per unit length of conductor, Q(t), displayed in the format Q(t)/B-m (in J/T m) vs. B-m where B-m is the field sweep amplitude enabled separation of the eddy current (or coupling current) and hysteretic components of Q(t), after which the results were analyzed and discussed. The intercept values were compared to the product of critical current and sample width. Similarly, calculated and measured values of the penetration field were compared. Additionally, the eddy current component of the loss was extracted and compared to that expected from the stabilizer and possible interfilament connections. The power loss in W/m was then compared for conductors of various width, stabilizer, and filamentation level and put in the context of applications. (c) 2007 Elsevier B.V. All rights reserved.