Design of compostte supports for air gap stator windings for turbine generators

Mechanical, thermal and electrical design requirements of cylindrical support structures for large generators are demanding. High elastic modulus and matching linear coefficients of thermal expansions in the axial and circumferential directions are required to meet design criteria for successful performance of machines. In order to achieve design objectives, a filament winding process using high performance composites was evaluated. This paper discusses the use of various reinforcements such as E-glass and graphite fiber in an epoxy resin matrix. Effect of hybridization (combining two reinforcing fibers in various proportions) on mechanical and thermal properties has been evaluated analytically using laminate theory. The influence of fiber to matrix ratio on various properties has also been evaluated. Since graphite fibers are electrically conductive, it was essential to determine their effect on electrical properties and the influence of graphite fibers on creepage distance under high voltage is discussed. Thin graphite/epoxy laminates (12" × 12" × 1/16" thick) were interspersed in the laminate and their effect on insulating properties of the laminate were evaluated.