Modeling of Transport AC Losses in Superconducting Arrays Carrying Anti-Parallel Currents

Transport ac losses of parallel arrays of superconducting tapes with an elliptical cross-section carrying mutually anti-parallel currents were modeled numerically by finite element method. Two different configurations—tapes positioned edge to edge (x-array) and tapes positioned face to face (y-array) were considered. It was found that an x-array increases the losses while a y-array decreases them—relative to infinitely distant tapes. The highest ac loss decrease is observed when the tapes are close to each other in y-array. The AC loss of a y-array made of various numbers of tapes was compared with the loss of an array made of round wires. It was found that y-arrays of tapes have lower loss than arrays of round wires. Bringing y-arrays of tapes close to each other in the x direction causes a significant increase in ac loss. The present analysis may be useful if considering fault current limiters made of straight conductors in a meandering configuration. The results are qualitatively valid also for a fault current limiter made of non-inductive (bifilar) windings in the form of several pancake coils, each coil wound non-inductively (i.e. with anti-parallel currents).