Material selection for the torque tubes of large superconducting rotating machinery

This report identifies properties to be considered when selecting materials used in construction of torque tubes for rotating superconducting field windings in electrical machinery. The main design requirements are stated and the groups of material properties that influence directly the mechanical and thermal performance of a torque tube are derived. Most desirable is a low thermal conductivity to modulus of elasticity ratio which governs the refrigeration expenses and the tube wall aspect ratio (thickness/length). Numerical examples point out that fibre-reinforced plastics are potential candidates for use in torque tubes.