New developments in resin rich insulating systems for high voltage rotating machines

Combining the up-to-date knowledge in polymer science with the well known electro-mechanical requirements of a high voltage rotating machine and the prescriptions of an economical manufacturing process, GEC ALSTHOM has designed a brand new resin rich-based insulating system which has been industrially produced for 5 years now. The system uses a unique fast curing F class solventless epoxy formulation, impregnated in a combination of glass fabric and specific mica paper. The tape, supplied in rolls without an inter layer, is mechanically applied on stator bars or coils and cured in less than a 2 hours cycle, either in a heating and cooling press specifically designed by GEC ALSTHOM, or in an oven with specific tooling. In spite of a fast curing process, the shelf life of the tape is approximately 6 months at room temperature. The system originally designed for machines up to 15 kV is now tested and qualified for 18 kV machines. The system fulfils the HD 345 requirements and is industrially used in mass production with a minimum capital investment. The paper describes the methodology used, starting from the defined technical goals, to design and optimize the system. The resin formulation was studied with physico chemical methods (viscosimetry, FTIR, differential scanning calorimetry, gel permeation chromotography). The mica paper was chosen after a micro structural evaluation. The curing process was optimized with classical thermal aging methods followed by electrical and mechanical characterizations, applied either on test lab samples or on production bars.