Development of new mica paper epoxy insulation systems for high voltage rotating machines

Better insulation performance is persistently required for high voltage rotating machines with the trend of increasing capacity and rated voltage. Resistance to thermal shock, mechanical reliability and dielectric strength of insulation are especially important. As for the impregnating varnish, asphaltic compound has been replaced by synthetic resins with progress in the chemical industry. Unsaturated polyester and epoxy resins are the most popular resins, the latter becoming more important because of their overall suitability. On the other hand, the main barrier insulating material tends to move toward reconstituted mica from mica splittings. In this paper, electrical and thermomechanical performances of newly developed epoxy insulation systems based on mica splittings and reconstituted mica are compared with asphaltic compound and unsaturated polyester insulation systems based on mica splittings by extensive thermal cycle tests. Superior characteristics of epoxy insulation systems are proved.