Insulation reliability issues in high frequency/transient environments of next generation high power electronics

As the automobile industry develops zero-emission vehicles and bring them to market by the 1998 deadline in California Massachusetts and New York, a potential EV (electric vehicle) safety and reliability engineering issue exists. High-voltage, high-frequency transients and related waveforms that are part of powering EV traction motors may damage the insulating materials in wiring harnesses, interfaces and connectors. Polypropylene films, 9 μm thick, representative of typical wire and connector bulk insulation, were placed between a rod-plane electrode set and subjected to high-voltage pulses until breakdown occurred for voltages sufficiently elevated that significant corona activity was in evidence. The effect of voltage magnitude and pulse repetition rate (rep-rate) on the number of pulses the films were able to survive was recorded. Standard statistical techniques for life testing were employed along with several novel modifications developed for this work, in the data analysis. In this study, it was found that the voltage dependence followed nearly that seen for intense corona DC and AC voltage applications, while the higher rep-rate permitted a greater pulse life than did lower rep-rates. Conclusions regarding aging rates of insulation systems under intense corona activity are presented along with recommended engineering practices to obviate the observed very high aging rates of such systems.