Alternating field losses in superconducting wires carrying dc transport currents. Part 2: multifilamentary composite conductors

Abstract

Investigations of transient field losses in multifilamentary composite conductors carrying dc transport currents, I, are presented. As shown previously, the total loss is best characterized by a normalized transport current i = l/ l c and a dimensionless field-change rate β = τB e /B p , where τ is the relaxation time of the coupling current and B p is the full-penetration field of a solid conductor equivalent to the multifilamentary composite. For β ≳ 1, the composite conductor behaves like a solid conductor and a saturation effect occurs in both the magnetization and the ac losses. The characteristic feature of the composite appears for β ≲ 1, and the total losses for transport currents below i < 1 − β are almost independent of i. Beyond the limit given, losses rise sharply. Experimental results over a wide range of the field change rate and the transport-current level agree sufficiently with the calculations.