Simulation of ac loss in Roebel coated conductor cables

Abstract

Roebel cables are a promising concept for high-current coated conductor cables with low acloss. In order to optimize their design, simulations are necessary. In this paper wecompute the field and current distribution and the ac loss due to either a transportcurrent or an applied magnetic field. We distinguish between the coupled anduncoupled situations. These situations correspond to the limits of low and highresistance between strands in one transposition length, respectively. We perform thesimulations with two different methods. One method assumes the critical-state modelfor the superconductor and calculates the current distribution by minimizingthe magnetic energy variation; the other describes the superconductor with apower-law resistivity and uses the finite-element technique for solving the problem. Wefound that the results from both models agree with each other. Moreover, thecoupling strongly influences the current distribution for all cases, as well as themagnetization loss. However, the effect on the transport loss is small. In conclusion,simulations are necessary in order to predict the loss reduction caused by the strandtransposition in a Roebel cable. Our simulation methods are useful for these predictions.