Performance of calcined and uncalcined VPI mica tapes for high voltage AC stator winding insulation

This paper compares the dielectric, impregnation, and handling characteristics of calcined and uncalcined (integrated) mica tapes designed for a vacuum pressure impregnation (VPI) insulation system. The evaluation techniques used to rank the tapes are discussed, including diagnostic tests, accelerated ageing tests, compatibility tests, and manufacturability trials. The potential correlation between dielectric loss and accelerated ageing life of the VPI-treated mica tapes is also investigated. The qualification of the mica tape with the best overall performance for a VPI insulation system is explained, and the process for implementation of the tape in a manufacturing environment is described