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Advanced ac loss measurement methods for superconducting tapes are described in detail and demonstrated on BSCCO/Ag (Bi2Sr2Ca2Cu3Ox with a Ag matrix) tapes in liquid nitrogen at 77 K. The aim of the measurements is to simulate the situation of a tape conductor in an electric power application like a transformer coil or a power cable. In this class of devices the conductor is fed with an alternating transport current and simultaneously exposed to an alternating magnetic field. In many devices the magnetic field vector points in a single direction but in some devices such as three-phase power cables and motors the magnetic field rotates around the conductor. In all cases described above an electromagnetic approach with pick-up coils and voltage taps is used to measure the ac loss. This method enables a separate study of magnetization loss and transport current loss when both the magnetic field and transport current are present simultaneously. The magnetization loss measurement setup for unidirectional and rotating magnetic field is described. The transport current loss measurement setup is described, focusing on the suppression of cross effects of ac transport current and ac magnetic field that disturb accurate measurements. Finally several relevant examples of the results obtained are shown.

The combination of current up to 50 kA and magnetic field of 13 T in the Cable-In-Conduit Conductors (CICC) for the coils in the International Thermonuclear Experimental Reactor (ITER), cause huge local transverse forces. This results in changes in the transport properties, friction and anomalous contact resistance versus force behavior. The latest design optimizations tend to go toward a lower void fraction (VF). This has an impact on the evolution of the coupling loss and on the possible degree of strand bending and deformation. Toroidal Field Model Coil (TFMC) type of conductors with VFs of 26%, 30% and 36% respectively, are tested in the Twente Cable Press, by which a variable (cyclic) transverse force of 650 kN/m is transferred directly to a cable section of 400 mm length at 4.2 K. The AC loss of the conductor, the inter-strand and strand-bundle resistance ( c ) in the cable and the associated bundle deformation are examined during mechanical cycling. The test results are discussed in view of the previous results on Nb 3 Sn ITER CICCs.

The reversible axial strain dependence of the critical current of MgB2 conductors is shown to vary with the temperature and magnetic field. The measured critical temperature and irreversibility field are also found to change reversibly with the axial strain. Combining these effects, we show empirically how the strain dependence of the whole critical surface can be scaled with just three parameters: the strain dependences of its three corner points.