Strain Distribution of Complex-Bending YBCO Tape in Force-Balanced Coil Applied to SMES

High-temperature superconductor power applications are still expected to be the main players in reducing carbon footprints. In superconducting magnetic energy storage, increasing the stored energy also increases the electromagnetic force, which generally requires heavier support structure. In terms of the force applied to conductors, it causes the extra bending and/or torsional strain of the REBCO tapes. To minimize the applied stress and to reduce the amount of electromagnetic force support structures, a force-balanced coil (FBC) that has a helical-like structure has been proposed. In this type of magnets, the superconducting thin tape experiences complex strains that come from flatwise and edgewise bending and tensile stress before coil operation. It is necessary to assess the applied strain distribution on the YBCO layer to fabricate an FBC. A newly developed experimental device to apply various strains to the tape and evaluate the strain distributions is presented. The results show that localized large strain will degrade the overall superconducting property.