Critical points in the More Electric Aircraft (MEA) converter-machine chain

This research aims to analyze the critical points of the inverter-to-machine chain used in the actuation system of MEA. To analyze the critical points, it is necessary to investigate the Partial Discharge Inception Voltage (PDIV) of the printed circuit board (PCB, representative models of the high voltage part terminal part of the inverter) by considering the effects of aerospace conditions like pressure, temperature, and humidity. Also, the endurance tests of twisted pairs (TPs, representative models of the turn/turn insulation) at aerospace conditions is investigated. This is necessary to assess the life of the machine when it is stressed by repetitive square wave/sinusoidal AC voltages. These experiments help to find the proper way to design and qualify MEA actuators. In this research, the effect of AC voltages, space charges at DC, temperature, pressure, and converter waveforms have been analyzed on different PCB models. Results show that an increased temperature decreases the PDIV and a reduction of PDIV is observed also due to a reduction of pressure. It is also analyzed that space charges play an important role in the measurement of PDIV at DC. Finally, the effect of converter waveforms supplied by SiC is analyzed, where it is observed that there is an 8% increase of PDIV as compared to the PDIV in AC. After these entire tests, it is concluded that the HV terminal part is not critical in the sense of PD occurrence. After the inverter part, the behavior of turn/turn insulation when it is continuously stressed by repetitive square wave/ AC 50 kHz voltages above PDIV has been analyzed. The results obtained from both the supplies are compared with each other to understand the effect of supply type and frequency on the endurance, finally, the effect of humidity on the endurance of the twisted pairs has been analyzed. It is observed after all these endurance tests that the corona-resistant wire cannot endure PD for a long time in aerospace conditions.