AC LOSSES IN SUPERCONDUCTING CABLES AND THEIR EXPECTED VALUES IN MAGNETIC SYSTEMS

After summarizing the different loss contributions in superconducting composites, some possible sources for differences in AC losses and tim e constants in measuring arrangements and their expected values in rea l magnetic systems are summarized: induced currents in end portions, f ield variations in time and space, mixed contributions from substructu res and normal parts, longitudinal field effects and inductive couplin g of current loops. Along with uncertainties in determining the effect ive resistivities and effective volumes for the current loops, all eff ects are important for evaluating the expected losses, time constants and discharging process in superconducting cables. The size effects ca n be calculated in most cases and incorporated into theoretical models . The spatially changing fields and coupling of current loops on the c able seem to be the most important effects causing differences in cabl e measurements with respect to the situation in different magnetic sys tems. These could be decisive for the design of large superconducting magnets with required stability and quench behaviour.