Detection of partial discharge activity in thermally aged SiC inverter fed stator winding samples and impact of partial discharges on their lifetime

The rise in popularity of SiC devices in power electronic converters for machine drives has been driven by the potential to enhance power density and efficiency through higher DC link voltages and faster switching rates. These enhancements are not without drawbacks, however, as they result in high voltage stress on machine insulation and higher electromagnetic interference(EMI). Due to this, there is an enhanced potential for machine winding insulation to be exposed to stresses which exceed the partial discharge inception voltage (PDIV), leading to a significant lifetime reduction of winding insulation. In this work, the effect of SiC inverter operation on lifetime reduction is investigated. The stator samples are aged in an accelerated manner at 230°C while being driven by a SiC inverter. PD activity is detected using a custom manufactured high-temperature coaxial cable-based antenna, the selection of which is discussed in this paper, alongside the post-processing requirements of the signal required for reliable PD detection. Comparison is made between cases in which PD occurred, and cases in which it did not, allowing the impact of PD on the sample lifetime to be assessed.