Voltage Stress Analysis in Hairpin Windings of Inverter-Fed Motors for Electric Aircraft Under Repetitive Impulsive Voltages Motors

With the increasingly urgent demand for high-power-density motor systems in electric aircraft, hairpin winding motors powered by inverters have received extensive attention due to their compact wiring and exceptional power to weight ratio. However, under high-frequency pulse width modulation driving conditions, the hairpin winding structure exhibits a significant voltage stress concentration effect on repetitive impulse voltages. This effect may lead to premature breakdown of weak insulation areas, seriously threatening the system's reliability. This paper focuses on hairpin winding motors in aviation electric propulsion systems and conducts an in-depth analysis of the voltage stress distribution characteristics under the action of high repetition rate impulse voltages. The research first constructs an equivalent winding modeling method to simulate the voltage transient distribution of stator coils under different pulse widths and rise times. The results show that the shorter the impulse rise time, the more uneven the voltage distribution at the front end of the winding, making it extremely easy to form concentrated voltage stress. By building an experimental platform and conducting impulse signal injection tests, the research measures the influence of different pulse parameters on the partial discharge inception voltage (PDIV), effectively verifying the rationality of the modeling predictions. In addition, this paper conducts comparative experiments on the partial discharge behavior under impulse excitation combined with typical insulation defect types. The experimental results show that insulation defects are more likely to break down prematurely under impulse voltages, exhibiting impulse response characteristics that are distinctly different from the traditional power-frequency aging mechanism. The research findings have crucial reference value for the insulation design of aviation motors driven by high-frequency inverters.