A Methodology for Accelerated Thermal Aging of an Automotive Hairpin Stator

This study presents a comprehensive exploration of the thermal aging of hairpin stators from a newly commissioned assembly line, tailored for automotive applications. The novelties in this article include a methodological approach that preserves material and process representativeness by testing stators directly from production. To increase sample size and stress the turn-to-turn failure mode, the star point connection is removed. Accelerated thermal aging is achieved by selecting the most aggressive set of temperatures, and expediting thermal index (TI) calculations without compromising accuracy. A detailed examination of the control parameters in the diagnostic sub-cycle is undertaken, including visual inspection, withstand voltage, capacitance, and step-by-step (SBS) impulse test with partial discharge inception voltage detection. Winding capacitance emerges as a crucial variable for tracking sample degradation, with its aging trend influenced by the measurement voltage. The introduction of the Physics of Failure (PoF) prompts an investigation into the impregnation resin as a potential factor contributing to the relatively low attained TI. The fault isolation process is generalized in a flowchart applicable to various motor types, extending its utility beyond the automotive domain.