Properties of a YBCO Pancake Coil Operating With AC Current at Frequencies up to 1000 Hz.

A small pancake coil was wound using 1.2 m long, 10 mm wide YBCO coated superconductor tape with impregnation by epoxy resin. The coil was immersed in liquid nitrogen and tested in several regimes. In the DC regime, we measured the I–V curve, the hysteresis of the magnetic field-current curve at liquid nitrogen temperature and the radial component of the coil field at the coil edges. The critical currents of a short sample at 77 K were also measured and compared with those of the coil. The AC losses measured in the frequency range from 60 Hz to 1000 Hz are compared with those of a similar coil wound with copper tape. The coil heating due to AC losses was monitored. At 60 Hz, the losses of the YBCO coil were nearly two orders of magnitude lower than those in the Cu coil. With increasing frequency, this difference becomes smaller, but the YBCO coil still exhibited lower losses at 1000 Hz. [ABSTRACT FROM AUTHOR]