Abstract
Wide bandgap (WBG) devices made from materials such as SiC, GaN, Ga2O3 and diamond, which can tolerate higher voltages and currents compared to silicon-based devices, are the most promising approach for reducing the size and weight of power management and conversion systems. Silicone gel, which is the existing commercial option for encapsulation of power modules, is susceptible to partial discharges (PDs). PDs often occur in air-filled cavities located in high electric field regions around the sharp edges of metallization in the gel. This study focuses on the modeling of PD phenomenon in an air filled-cavity in silicone gel for the combination of (1) a fast, high-frequency square wave voltage and (2) low-pressure conditions. The low-pressure condition is common in the aviation industry where pressure can go as low as 4 psi. To integrate the pressure impact into PD model, in the first place, the model parameters are adjusted with the experimental results reported in the literature and in the second place, the dependencies of various PD characteristics such as dielectric constant and inception electric field on pressure are examined. Finally, the reflections of these changes in PD intensity, duration and inception time are investigated. The results imply that the low pressure at high altitudes can considerably affect the PD inception and extinction criterion, also the transient state conditions during PD events. These changes result in the prolongation of PD events and more intense ones. As the PD model is strongly dependent upon the accurate estimation electric field estimation of the system, a finite-element analysis (FEA) model developed in COMSOL Multiphysics linked with MATLAB is employed that numerically calculates the electric field distribution.
Highlights
In the commercial aircraft segment, the annual growth in global air traffic passenger demand is expected at 4.7% until 2028 [1] with passenger numbers expected to double in the 20 years until around 2040 [2]
[28], estimated estimated the the parameters parameters associated associated tested with model such that it reproduces the same results as in and chose it as aa solid solid with partial discharges (PDs) model such that it reproduces the same results as in Reference [38] and chose it as groundwork for for further further investigations
Because the pressure at higher altitudes can be extremely low, this study examined the impact of high frequency, high slew rate unipolar square wave voltage under low-pressure conditions
Summary
In the commercial aircraft segment, the annual growth in global air traffic passenger demand is expected at 4.7% until 2028 [1] with passenger numbers expected to double in the 20 years until around 2040 [2]. In Reference [27], the detrimental impact of slew rate was studied and the results showed that high slew rate square voltages substantially increased the intensity of PDs within the insulating medium and changed the PD behavior over time, that is, the repetition rate and the times at which discharges occur. While the reported experimental results provided invaluable clues on the impact of fast-rise, high-frequency square wave voltages, no study has been performed on the modeling of PD phenomenon under this type of voltage. To address this gap, a FEA method was developed in Reference [28] for modeling PD characteristics under fast, repetitive voltage pulses.
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