Influence of PD characteristics within motor windings exposed to elevated temperatures

Voltage levels used in AC motor drives is ontinuously increasing and this paper compares the electrical stress appearing in two different motor winding insulation specimens. The aim is to explore the changes in Partial discharge characteristics to evaluate grade 2 motor insulation for different temperature levels and rise times of the applied voltage as well as influence of overshoots. Here it is discussed how much deviation in properties than can be expected for different insulation thicknesses. The paper shows for example that elevated temperature influences the time lag considerably as well as the inception voltage level, which both influence the PD exposure of the insulation system