AC LOSS OF A MULTIFILAMENTARY SUPERCONDUCTING COMPOSITE IN A TRANSVERSE AC MAGNETIC-FIELD WITH LARGE-AMPLITUDE

A general study is made of ac losses of a multifilamentary superconducting composite carrying no transport current in a transverse ac magnetic field with large amplitude. In the case of applying a magnetic field below the current-saturation condition in an outermost layer, an eddy current loss as well as a hysteresis loss is calculated by taking account of the hysteresis effect of a superconducting filament on these losses with an apparent complex permeability of the filament. It is shown that the frequency characteristics of the eddy current loss are considerably different from those calculated from previous theories. In the case above the saturation condition, a loss calculation is made taking account of the phase difference between the applied magnetic field and the internal one. It is shown in this case that the hysteresis loss increases rapidly with frequency around the critical frequency. These calculated results are confirmed by experiments with Nb-Ti multifilamentary composites. General features of ac losses are also given for the composite design.