Corona resistant insulating systems characterization for low voltage rotating machine

The type I insulating system for low voltage electric machines is characterized by organic enamel as primary insulation material and impregnating resin as secondary insulating materials. It is known that these machines are supplied by a PWM inverter and if there is a relative long distance between the machine and the power electronics, the resonance and the reflection phenomena could cause overvoltage in the power supply voltage. This overvoltage could incept partial discharge (PD) activity in the insulating systems. This kind of insulating system can't resist under PD activity and the machines quickly reach total breakdown conditions.In an insulating system composed by enamel and resin, it takes great importance the chemical compatibility between them and the adopted impregnation techniques. In this study, two kind of impregnating resin applied on twisted pairs with a conventional enamel, have been analyzed to compare the different behavior. Ageing tests have been performed until the specimen total breakdown, and the PD activity has been monitored. Analyzing the derived quantities of the PD activity, a predictive lifetime model has been obtained.