Epoxy lead cones for free supported leads

Abstract

The support of lead wires at the lead exits of epoxy impregnated coils can be an important aspect of the coil design. This is especially true for coils fabricated of the brittle high field superconductors including both the metallic and the oxide superconductors. There is potential damage to a lead wire due to the local Lorentz force and also due to the relative motion of the coil and surrounding support structure, if that relative motion results in mechanical stress on the lead. An extension of the free floating coil concept for epoxy impregnated coils is the free supported lead concept. A free lead is connected to the coil itself and moves with the coil. A free lead is free of rigid connection to the coil supporting structure when that connection can result in stress on the lead. A critical part of the free supported lead is the lead exit from the windings. Support of the lead wire at the lead exit may be accomplished by extending the epoxy-fiber structure of the winding region into a bonded structure that encapsulates and supports the lead exit. The resulting bonded structure tends to be in the shape of a cone. The lead cone concept is introduced through design and processing. The results of a stress analysis are described. Available mechanical test data on model structures are presented.