Evaluation of Offline Partial Discharge in Vacuum Environments

Abstract— An evaluation of several insulation types at various degrees of vacuum using repetitive discharge inception and extinction voltage offline testing will be presented. Insulation systems were evaluated in atmosphere and compared to values to 1mmHg using a commercial partial discharge surge tester. The insulation systems evaluated include unvarnished windings, dip and bake epoxy, epoxy trickle impregnation and vacuum encapsulated. The results provide the potential impact of partial discharge with repetitive surges for applications of electric machines in low atmosphere conditions with inverters.