Development of an Insulation Lifetime Model under Varied Pressure and Voltage Conditions for More Electric Aircraft Applications

The high electric stress experienced by insulation systems today continues to pose significant challenges to the reliability of inverter-fed electrical machines (EMs) used in transportation applications. Electrical aging caused by partial discharge is one of the primary factors threatening the reliability of EMs. Moreover, compared to EMs meant for industrial applications, the insulation systems of EMs designed for more-electric aircraft may also be affected by pressure conditions. For instance, EMs used in primary flight control surface actuators may operate during the cruise phase at altitudes of approximately 12 km and pressures as low as 200 mbar. Several studies have highlighted that low-pressure environments can accelerate the electrical aging process. However, a comprehensive lifetime model accounting for both pressure and electrical stress remains unavailable. Such a model would enable machine designers to assess the suitability of insulation systems for various applications across different operating altitudes (i.e., pressure levels). In this paper, accelerated insulation aging tests are conducted under twelve distinct combinations of pressure and voltage conditions, and a multi-stress (i.e., electrical and pressure stress) lifetime model applicable in the range 200÷1000 mbar is developed, accounting for the impact of pressure on inverse power law’s parameters.