Basic Concept for Uniform Current Distribution in Parallel Conductors by Introducing a Small Number of Transpositions in REBCO Armature Coils

We propose the concept of uniform current between groups (CUCG) in superconducting armature coils composed of two or more strands of transposed parallel conductors. We validate the proposed concept by measuring the current distributions in several double pancake test coils comprising two and four parallel conductors using Rogowski coils by applying AC signals of varying frequencies and amplitudes. Accordingly, uniform transport currents across four strands were confirmed. The proposed concept produced uniform current distributions across four groups of parallel conductors with a small number of transpositions. This work paves the way for developing armature coils composed of more than eight strands in parallel conductors by introducing a small number of transpositions based on CUCG.