Optimization of Three- and Single-Phase AC HTS Cables Design by Numerical Simulation

This paper presents the results of calculation of ac HTS cables designs optimized by the values of hysteresis and eddy current losses. The superconducting elements of the cables are 2G HTS tapes. The program we developed and used allowed the variation of both the cable shape and its internal structure. There have been considered nonsectioned and sectioned cables having two variants of geometry-the axially symmetrical coaxial and extended rectangular cross-sectional shape. It has been shown that the internal structure optimization allows decreasing of ac losses in several times for both cross-sectional shapes. Due to the compensation of the perpendicular magnetic field component, the characteristics of flat three-phase cables turn out to be close of those with the axially symmetrical cross-sectional shape. In this case, the rectangular cross-sectional shape allows obtaining better mass, dimensional, and mechanical parameters and better cooling conditions of phases. The cables sectioning allows an essential reduction of ac losses. But, the latter is possible only when there is a uniform current distribution over the sections, i.e., at a very exact design calculation.