Coil assembly of an integrated motor pump or turbine having reduced thermal stress at cryogenic temperatures

Abstract

A coil assembly of a seal-less pump or turbine comprises materials having differing coefficients of thermal expansion that are layered but not bonded together, thereby reducing thermal stresses at cryogenic temperatures. Differences in shrinkage upon cooling provides compressive structural support. Coils are wound on hollow, non-magnetic spools, and a resin is applied for mechanical support, for example by vacuum impregnation. A release agent prevents bonding of the resin to the coils. The hollow spools are then placed over winding cores, such as laminated iron cores, without bonding. During cooling, the non-metallic spools shrink more than the cores, thereby providing compression fits. At ambient temperature, the spools can be held in place by interferences fits, and/or by key-stock pieces. Wired interconnections between the coils can be located within a wire harness cavity, which can be filled with a resin to provide mechanical support, while a release agent prevents bonding.