Non-Destructive Testing Methodology for Impregnation Quality Identification of Segmented Stators in a Traction Motor

Electrical machines’ stator impregnation quality plays a significant role in ensuring optimal system performance by providing electrical insulation, thermal conductivity, and mechanical rigidity. Prior research has established that the thermal DC test is a viable non-invasive technique for discerning the operational and health attributes of electrical machine components, but it is time-consuming. This research aims to investigate the utilization of electrical impedance analysis and derived control variables for the assessment of stator tooth impregnation quality. The research integrates two Type 1 Gauge Repeatability and Reproducibility campaigns to assess the thermal and electrical testing tolerance ranges. The thermal conductance and conductors-to-lamination capacitance measurements performed in an operator-controlled but uncontrolled environment result in a +/-66.7% and +/-4.4% tolerance range, respectively. The greater repeatability of capacitance measurement may lead to an improvement in impregnation quality identification in conditions closer to a production environment. A Finite Element model is leveraged to confirm the hypothesis. Simulation results underline both a strong correlation (ρ=0.99) between thermal conductance and conductor-to-lamination capacitance and their suitability as impregnation goodness diagnostics signals (ρ=0.95, 0.99 respectively). Impedance analysis could have various applications such as identifying defects during manufacturing, or optimizing the impregnation process, reducing part scraping.