High Impregnability of Film Backed Mica Tape Made of Uncalcined Muscovite Mica Paper Containing Glass Chops

Mica papers are made from calcined and uncalcined muscovite, and uncalcined phlogopite mica. Some of them may contain chopped glass or aramid fibers as admixtures. The mica papers are laminated to poly films or glass cloths and are processed into mica tapes. The mica tapes used for vacuum pressure impregnated insulation of coils of high-voltage machines are required with high impregnation ability. This work is focused on the benefits of using uncalcined muscovite mica paper with glass chops in mica tape with poly film backing. At first, the general properties of mica papers with and without admixtures were evaluated. Comparison of the results confirmed that the glass chops in the mica paper improve the impregnability. In addition, the properties of epoxy resin treated mica papers were investigated. The treatment reinforced the mica papers mechanically but on the other hand lowered their impregnation abilities. However, the impregnability of the mica paper with glass chops was preserved superior. Film backed mica tapes were produced from the investigated mica papers. The impregnability of insulations made of these mica tapes with high viscosity impregnation resin was considered. At the insulations made of mica tapes with mica paper with glass chops, considerable shorter impregnation times were observed without impact on their insulation performance. Highly impregnable mica tapes enable to the mica tape users to optimize their impregnation processes, insulation systems or to consider about impregnating resins with increased viscosities.