Partial Discharge in Silicon Carbide Driven Random Wound Motor Windings for Aviation Applications

Abstract

Electrification in aircraft is expected to increase due to its potential benefits of reduced environmental impacts. One of the most challenging tasks for aircraft electrical system is to achieve size, weight and power loss (SWaP) reduction while maintaining partial discharge (PD) free at high altitude. Electric motor and its motor drive are among the most critical equipment in aircraft electrical system. The wide bandgap (WBG) semiconductor device based motor drive can contribute to SWaP reduction due to the high switching speed and high switching frequency. However, for the Type I random wound electric motor, partial discharge (PD) inception usually means the end-of-life of the motor. When WBG device based motor drive is applied to random wound electric motor for aviation applications, high voltage, high dv/dt at high altitude bring unprecedented challenges to the PD-free operation of the electric motor. In this paper, PD measurement, PD analysis and PD-free design methodology for the random wound motor windings driven by silicon carbide (SiC) devices under different air pressures are studied to address the challenges. This paper first presents the measured PD inception characteristics under the impacts of pulse voltage frequency, rise time and air pressure. Based on the measurement results, an empirical model is developed to estimate the PD inception voltage (PDIV) at different conditions. Then, the measured PDIV results are compared with traditional Paschen’s curve based design guideline to highlight the needs for a new design guideline. Finally, based on the developed PDIV estimation model, a PD-free design methodology for random wound motor windings under various air pressures and voltage pulse waveforms is proposed.