In recent years, transportation electrification represents the way forward for reducing CO2 emissions and cutting down toxic particles. Hence, efficient powertrains employing energy sources other than fossil fuels are becoming increasingly popular. In this scenario, compact and lightweight electrical machines are required, particularly in aerospace and automotive applications. While the trend is to increment electrical machines torque and power density, their reliability is also expected to be enhanced, due to the safety-critical nature of these applications. In low voltage electrical machines, the partial discharges occurrence might irreversibly compromise the electric drive functionality. Indeed, once partial discharges are incepted in organic insulating materials, they can cause an out-of-service within short time. This paper investigates the impact of a partial discharge-free insulation's design on the performance of a traction motor. The presented study combines finite element models and the Paschen's law for air at sea level pressure. The developed insulation models are experimentally validated via measurements on custom-built prototypes.