Evaluation of epoxy V.P.I. insulation for high voltage stator windings

Epoxy bonded high voltage mica based stator insulation systems have been produced for many years. One such system employing an epoxide/anhydride impregnating resin, Neccobond “E” was introduced by National Electric Coil to satisfy customer requests for an epoxy bonded insulation system. The original base materials had been successfully applied in Europe since the 1960´s. However before this product was accepted by American Electric Power for use in large high voltage rotating machines a series of electrical, mechanical and thermal tests were applied to determine specific characteristics of this particular insulation system. Numerous production stator coils and Roebel bars were evaluated. This paper presents results of dissipation factor, iso-thermal weight loss, water submersion, voltage endurance, dielectric breakdown, and bond strength evaluations of this epoxy bonded high voltage insulation system