Using multi-stress aging test to evaluate and improve medium-voltage stator insulation for adjustable speed drive applications

In order to better understand insulation performance under real-life operation conditions, a new test set-up was installed to apply multiple stresses (electrical, mechanical, and thermal) simultaneously on test coils in the formette. This is a continued effort from our previous study that focused mainly on the differences in dielectric performance of insulation systems between 60 Hz and high-frequency only. By adding additional thermal and mechanical stresses, this new set-up proved to be a more effective tool to evaluate stator insulation systems in service, especially under adjustable speed drive conditions where voltage spikes of fast rise time and high magnitude generated by some of these drives have put much greater stress on the insulation. Tests were performed on multiple insulation systems under both 60 Hz and high frequency conditions. Information gathered by this project enables us to better understand the different impacts service conditions have had on the insulation system. It also helps us verify the insulation integrity and improve the overall insulation performance and their service lives.