Evaluation of mica segment insulation

Mica segments have been used for commutator insulation for about seventy years. The type produced at the turn of the century was very inferior to that being used today. It certainly would not survive the compressive force, temperature requirements, or spin test exerted or required of this more modern era. This presentation is intended to evaluate amid compare the numerous mica segment materials available with respect to the primary requisites: dielectric strength, compression---both hot and cold, and stability at high pressures and temperatures.