ABSTRACT The remaining service life and reliability of DC‐link capacitors in traction converters are critical to the safe and stable operation of railway systems. However, accurate lifetime assessment under electrothermal coupled stress remains a significant challenge. This study proposes a systematic method for assessing the remaining service life and reliability of metallised polypropylene film capacitors widely used in traction applications. Capacitors removed from traction converters at the fifth‐level overhaul stage, corresponding to approximately 4.8 million kilometres of service, are investigated and compared with new capacitors. Accelerated ageing tests are conducted under combined high‐temperature and overvoltage conditions, with multiple stress levels considered. Based on operating mileage and ageing duration, a parameter degradation model is established to characterise the evolution of key electrical properties and their driving factors. Furthermore, an electrothermal‐coupled life and reliability evaluation model is developed. The results provide a solid theoretical basis for capacitor selection and preventive maintenance planning and offer practical guidance for improving the reliability of electric train traction systems.
Chunxing et al. (2026) studied this question.