Thermal aging studies of encapsulated motorette insulation systems

There has been a continuing history of failures of insulation systems in shipboard electric motors due to high humidity, condensation and flooding. In earlier work on this problem the Navy let a contract to a commercial company for the development of an electric insulation system specifically intended for induction motors subjected to occasional submergence in sea water. The performance under submerged condition of the insulation so developed was reported by Hackney and Walker¹. In this paper they also outlined the various insulation systems that were studied along with those that were discarded during the development of the improved system. The performance of this new insulation system when subjected to other severe environmental conditions of long-term high humidity, steam, and salt spray was reported by Walker and Flaherty². It was demonstrated that an encapsulated insulation system was vastly superior to each of 15 different varnish-impregnated insulation systems in withstanding severe environmental conditions.