Altitude Readiness of High Voltage IGBTs Subjected to the Partial Discharge at Harsh Environmental Conditions for Hybrid Electric Aircraft Propulsion

The reliability of the insulation of commercially used high voltage insulated gate bipolar transistor (IGBT) subjected to untimely initiation of partial discharge (PD) at low pressures and high temperatures is investigated and discussed in this letter. To date, no research has addressed the vulnerability of the high voltage IGBTs to the PDs at harsh environmental conditions for aerospace applications. This letter aims to fill this gap and illustrate the PD characteristics initiated between the electronic components inside the silicone gel. To this end, five commercial 3.3kV IGBT modules and four 4.5kV IGBT modules were tested at AC voltage under low pressures (20kPa, 15kPa, and 10kPa) and high temperatures up to 120C. An efficient PD test method and an anti-series connection configuration are suggested which emulate a realistic operational scenario for IGBTs together with the one suggested by the current standard. Experimental results reveal the occurrence of inconsistent PDs initiating from possible dynamic PD source inside the gel at low pressures, and more intense and consistent PDs when the temperature increases. It is expected the findings highlight the importance of PD tests on IGBTs at the abovementioned operation conditions and provide a selection and modification guidelines of PD-free IGBTs for manufacturers and engineers in the aerospace industry.