A New Insulation Experience in Large Rotating Machinery in Japan

New synthetic resin insulation systems have been established in Japan, as in Europe and the United States [2], and have a history of almost fifteen years. The research work of authors, initiated in 1949, led to the completion of the unsaturated polyester insulation system called SLS insulation. Outstanding performance was obtained as of 1957 when this new insulation system was applied to large rotary-type machinery. In the meantime, a trial manufacture study was conducted on epoxy-resin insulation in view of its excellent electrical and mechanical properties. As a result, an epoxy insulating system of quality distinctly superior to the former system was successfully put on a mass-production basis. This paper describes the fundamental insulation procedure, the dielectric properties, and the service experience of this system.