New corona resistant insulations of aromatic polyamide

Inorganic insulations, typified by asbestos and mica, exhibit good resistance to corona-induced degradation, and are considered significantly superior to wholly organic insulations. These inorganic insulations, however, suffer from inherently poor mechanical properties, and must be supported by backings which generally by themselves contribute no electrical insulation value. The purpose of this paper is to describe a new material — an intimate blend of polyamide paper and mica — which provides good electrical, thermal, and mechanical properties, in addition to corona resistance. There is no binder or other ingredient in this structure. This new insulation, originally designed for use in high voltage rotating equipment, is expected to find applications in other areas such as high voltage transformers, V-rings and non-electrical applications.