Improved groundwall insulation for VPI´ed high voltage stator coils

Improved dielectric performance of VPI´ed high voltage stator coils has been developed through a mica paper tape improvement program. The objectives of the program were to develop a glass-backed mica tape with higher dielectric properties than commercially available mica tapes. Tapes with improved dielectric properties allow a reduction in coil groundwall thickness which improves the thermal performance which in turn allows stator winding design of higher power density. Both commercially available tapes and custom tape designs were evaluated. Custom tapes were developed with different tape, resin, and glass backing characteristics. These tape designs were supplied by major tape manufacturers and were subject to in house testing which included electrical, chemical and mechanical testing. Other objectives are to develop a groundwall insulation system that requires shorter manufacturing times, low cost manufacturing facilities and reduced test requirements. This paper reviews the results of this tape improvement effort which leads to an improved groundwall system