Class f rotor slot armor for medium size turbine-generators

Summary form only given. Many different materials have been used for slot liners in turbine-generator rotors. Until the early 1950´s, composites using flake mica were in widespread use. These were replaced by the introduction of glass reinforced plastics whose use continues to predominate today. More recently, however, high temperature organic materials have been developed which are suitable for slot armor construction. thus offering the insulation engineer a wide choice in designing materials and composites for slot insulation applications. At the General Electric Co., Medium Steam Turbine Department, Nomex^® type 410 aramid paper has been used for several years as slot armor on generator rotors up to about 100 MVA in rating. As a slot armor material, aramid paper has proven to be a substantial improvement over the micaceous composites that it replaced. It has also provided both advantages, that have been made use of, and disadvantages, that have had to be overcome, over glass reinforced plastics which it has replaced in certain applications. The acceptance of aramid paper as rotor slot ground insulation has involved many years of testing. This has involved analysis of the stresses that exist both during assembly of the generator rotor and during service. In addition, a great deal of manufacturing engineering has been required to develop the methods and equipment required to transform flat aramid paper into a high quality rotor slot liner configuration. Aramid paper has been assembled into G.E., MST generator rotors for over seven years and a great deal of service and shop assembly experience has been gathered during that period. Applications have ranged from high cycling generators to medium size base loaded ones. Designs have varied with respect to the thickness and number of turns per rotor coil as well as the coil size and degree of difficulty with which the coils could be assembled. This paper will deal with all of the experiences associated with the development of aramid paper for generator rotor slot armor application. Emphasis will be placed on explaining the types of design limits and assembly and service stresses that must be overcome by a slot armor material while detailing the test results which have shown that aramid paper can perform satisfactorily as a slot armor in certain medium size generator rotor applications.