Advanced Partial Discharge Testing of 540V Aeronautic Motors Fed by SiC Inverter under Altitude Conditions

The present paper reports non-electrically intrusive partial discharge investigations on an aeronautic motor fed by SiC inverter drive under variable environmental conditions. A representative test procedure and experimental set-up based on operating aeronautic conditions are essential to ensure the accuracy and reliability of partial discharge test on aircraft systems to make informed decisions on insulation system design choice. The aim of this paper is to demonstrate the feasibility of partial discharge test of the insulation system on a typical aeronautic motor under such conditions, both electrically and environmentally. To do so, the paper will start by detailing the innovative experimental set-up to be used in the study. It mainly consists in a high-voltage (1000V) inverter drive using SiC components to provide fast rise time surges and associated with phase-by-phase surge filtering. A vacuum chamber is used to simulate altitude while the association of non-intrusive sensors and wavelet based signal processing provided partial discharge detection. Optical detection is also used to reinforce partial discharge inception level accuracy. Then, an analysis is carried out on a 540V motor to find out which combination of switching frequency, harness length, rise time by phase and voltage magnitude is the worst case scenario. The study helps to realize the benefits of using an inverter based test method to find the limits of the insulation system under various pressure and electrical conditions. It is shown that a representative insulation system performance diagram could be built experimentally and used to enhance insulation design and manufacturing choices. This paper will also review the ability of the non-intrusive test method and the associated numerical signal processing to detect partial discharge in a motor fed by fast-rise time surge and under different pressures. The paper concludes with an analysis of results and thoughts about future work regarding advanced test procedure.