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

Insulation materials based on flexible mica tapes for post impregnation, consist of mica papers and base materials such as poly film or glass cloths. Generally referred to as a standard mica paper tape. Mica papers are made from calcined and uncalcined muscovite, and uncalcined phlogopite. Some of them contain chopped glass and/or aramid as an admixture. Mica paper is laminated to a base material and is processed into mica insulation as a multi-layer system. Mica insulation systems utilizing vacuum pressure impregnation of high voltage coils for rotating machines require high degrees of resin impregnability. This work focuses on the advantages of using mica tape made from a blended paper of uncalcined muscovite with glass chops and laminated onto a glass cloth backing. The impregnability of tapes made from a typical muscovite paper and non-typical blended mica papers with glass chop admixtures was evaluated. The results confirmed that the glass chops within the mica paper improve the impregnability of the mica tape. The experiment was performed utilizing test coils and bar models under specific impregnation conditions. It was found that the mica paper with glass chops admixture did impregnate faster than the typical mica paper tapes without any admixture. The coils insulated with blended mica papers were subjected to voltage endurance tests. The results showed that the insulation using blended mica paper with glass chops has sufficient insulation performance in accordance with relevant international standards. Highly impregnable mica tapes made of mica paper with glass chops allow users to optimize their impregnation processes, insulation systems, and to consider impregnating resins with increased viscosities.