Introduction
Over time, various methods for producing stator insulation for large rotating machines have evolved. Within the industry there are basically two types of insulation production methods. One method is referred to as VPI (Vacuum Pressure Impregnation) technology. This method uses dry mica tapes, typically made of mica paper and reinforcing layers bonded with a relatively small amount of epoxy based adhesive [3],[5]. The stator bars and coils are wrapped with the dry mica tapes. After completing the wrapping the coils and bars undergo a vacuum cycle which removes volatiles and humidity, then resin is introduced and pressurized, driving the resin into the insulation. After undergoing the Vacuum Pressure Impregnation process, the resin penetrated, final product is cured afterwards in an oven.
