DC Dielectric Strength Evaluation of Motor Winding Insulation for Aerospace Applications

Insulation in electric machines is vital in determining system reliability and lifespan, especially under extreme environmental conditions. With the rapid shift toward More Electric Aircraft (MEA), All Electric Aircraft (AEA), and advanced space missions, electric motor components must perform reliably under low pressures, wide temperature ranges, and exposure to radiation. Magnet wires are central to motor operation, and their insulation must withstand high voltage stress in these demanding conditions. While prior research has predominantly focused on insulation performance under AC or pulse width modulated (PWM) waveforms and partial discharge (PD) behavior, there is a limited understanding of dielectric strength under direct current (DC) stress, particularly at reduced atmospheric pressures. This paper presents an experimental investigation into the DC dielectric strength of three magnet wire types (15 AWG, 18 AWG, and 20 AWG) tested at three pressure levels: $101 \text{kPa}, 80 \text{kPa}$, and 40 kPa. Using a voltage to breakdown with a constant ramp method, the study evaluates the insulation's withstand capacity across wire sizes and environmental pressures.