AC losses in prototype multistrand conductors for warm dielectric cable designs

We report on multiphase ac losses in four-layer prototype multi-strand conductors (PMCs) wound from EITS tape provided by American Superconductor Corporation. These conductors are prototypes warm dielectric cable designs, such as for the US Dept. of Energy's Superconductivity Partnership Initiative Project at Detroit Edison, We report on single phase 'two phaset'(no current in Ihe PMC but with an external ac magnetic field generated by the two normal Conductors arranged at the remaining corners of an equilateral triangle forming a three-phase configuration) ,and balanced three phase losses. Losses were also measured using a set of saddle coils to apply an ac magnetic field to the PMC. The losses were measured as a function of temperature, frequency, and current. We compare the losses for three PMCs, one (4LA) wound conventionally with equal pitch angles for all layers and the two others (4LB and 4LC) wound to achieve equal current distribution (UCD) among the layers, and thus lower singlephase losses in the operating region. In addition, 4LC was wound with a newer gcneration tape having a higher critical current. The PMC 4LC was found to have the lowest single, twophase, and three-phase losses.