Development of a vertical generator stator bar insulation system for operation at increased stress

The use of corona resistant fillers in epoxy resins or enamels can improve the long term survival of insulating materials subjected to partial discharge (PD) attack. Since 1989, motors produced by this manufacturer have benefited from the enhanced corona resistance used in the stator coil strand and turn insulation. Using corona resistant materials can extend the life of insulation systems when existing insulation builds are maintained. Alternatively they can allow the machine designer to reduce the size and/or cost of the rotating machine through build reduction while maintaining “winding life”. Regardless of which alternative is selected, the customer benefits from systems possessing improved corona resistance. The present insulation system used for hydro-generator stator bars was targeted as a good candidate for build reduction using the judicious application of corona resistant materials. Insulation build reduction is exciting to the electrical designer, since design engineers regard insulation as a necessary evil. Insulation is required to prevent machine failure, but the space taken by insulation is wasted for energy conversion components such as copper and steel. Through design analysis, it is evident that a small reduction in insulation can provide a major reduction in overall machine size