Stress Analysis for Toroid-Type HTS SMES Coil and Bobbin Structure Considering Large Parallel Magnetic Field

A 2.5 MJ HTS superconducting magnetic energy storage (SMES) system is under development to compensate the sag or instantaneous black out for a utility side. The toroidal-type structure is adapted to reduce the perpendicular magnetic field and the stray field at outside of SMES. A toroidal-type magnet shows a small perpendicular magnetic field. However, parallel magnetic field is much larger than perpendicular one. Therefore, Lorentz force of HTS tape can be so strong and the stress analysis should be carried out to verify that the maximum hoop stress and normal stress are in appropriate range. In addition, overall inward force of an HTS pancake winding in toroidal-type magnet is very strong and stress analysis for the bobbin and its supporting parts is important for a design a mechanically stable structure. This paper describes an analysis and design result for a toroidal-type HTS SMES magnet considering orthotropic material properties, large magnetic field and the resulting Lorentz force.