Homogeneous current distribution experiment in a multi-laminated HTS tape conductor for a double-pancake coil of SMES

A multi-laminated HTS tape conductor wound into double-pancake coils has recently been used for large SMES. If the HTS tapes are simply laminated to form the conductor, the current distribution in the laminated tape conductor of the coil is not homogeneous because of the differences among all the tape inductances. Transposition of these tapes at the innermost or outermost layer of the coil is effective for homogeneous current distribution. However, this method would requires the same number of single-pancake coils as that of the HTS tape conductor, and hence the number of HTS tape conductors is restricted. In this paper, we propose a new method to control the current distribution in the laminated conductor using transposition at the innermost layer of a double-pancake coil and adjusting the gaps between the laminated tapes. We analyze the current distributions for multi-laminated HTS tape conductors for a double-pancake coil, and show the homogeneous current distribution of the laminated tape conductor. In order to verify the theory, we designed homogeneous current distribution coil wound with the multi-laminated (four times) HTS tape conductors by transposing them at the innermost layer and by adjusting the additional thickness 0.075 mm between the parallel conductors. We obtained the homogeneous current distribution in the tape conductor. The experimental data were in good agreement with the theory. (C) 2011 Elsevier B.V. All rights reserved.