Micaceous mainwall insulation for high-voltage rotating machines

The mineral mica has found application in the mainwall insulation of high-voltage electric rotating machines for over a century, and remains intrinsic to achieving high machine reliability and lifetimes. This paper retraces the historical development of micaceous mainwall insulation, and examines the materials and construction of modern mica tapes in detail. In this context, we provide examples of the multitude of available mica tapes, and review various properties of mica tapes relevant to their manufacture, application, and performance, concluding with some observed trends.