AC loss data for YBCO double-pancake coils

Since the second generation of superconducting tapes, YBCO coated conductors, are commercially available, large scale AC applications seem to be very promising provided that AC loss of the 2G tapes can be reduced. In this work, critical current measurements as well as AC loss experiments of YBCO double-pancake coils and 2G tapes were performed. An analysis of the magnetic field distribution at the coil's exterior, especially in critical points, shows no self-field limitation of the critical current density. Magnetisation loss data were obtained for YBCO double-pancake coils by applying magnetic AC fields at 77 K. It is demonstrated that the AC loss can be reduced by means of magnetic shielding. Furthermore, AC transport losses have been measured at temperatures between 65 and 77 K for frequencies between 36 and 288 Hz. The AC loss data were found to be dominated by hysteresis losses. The obtained results are compared with AC loss data reported for YBCO pancake coils.