A novel repetitive square wave voltage generator used for insulation evaluation of rotating machines driven by power electronics

To ensure insulation system reliability of rotating machines driven by power electronics, accelerated tests under repetitive impulsive voltages should be performed on turn-to-turn insulation according to technical specifications provided by the International Electrotechnical Commission. Due to the fact that the voltage parameters of repetitive impulsive voltage can influence the insulation lifetime significantly, the voltage parameters should be carefully controlled during the accelerated tests. In order to increase the endurance test efficiency when testing many insulation specimens in parallel, impulsive voltage rise time should be controlled at some constant values after one or more specimen breakdown to obtain objective endurance tests results. This paper provides a description of a novel square wave voltage generator used for insulation evaluation of rotating machines driven by power electronics. A single channel generator with variable rise time used for one specimen and multi-channels generator with constant rise time used to test five specimen in parallel are presented. In the multi-channel generator, resorting to controlling units and circuit structure, the RC parameter in high voltage circuit can be adjusted automatically when performing endurance on parallel specimens to keep the rise time of the impulsive voltage at constant values. The multi-channel generator can largely increase the endurance evaluation efficiency for insulation systems of rotating machines fed by power electronics.