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Air has always been an insulation medium that mainly interfaces with solid dielectrics within power electronics building blocks (PEBBs). Equipped with wide-bandgap (WBG) and ultrawide-bandgap (UWBG) devices, air around sharp edges is stressed by high frequency, high slew rate square wave voltage pulses within PEBBs. Having a lower insulation strength than solid dielectrics, decreased dielectric strength of air due to high frequencies and high slew rates of applied voltage can lead to enhanced surface discharges at interfaces, leading to degradation of solid dielectrics and eventually their breakdown. This shows the importance of studying the rise time and frequency effect on air breakdown subjected to the square wave voltage pulses at normal pressure, which is the main objective of our research. This study focuses on understanding the air breakdown voltage behavior under a frequency range of 2.5 kHz to 75 kHz and a rise time between 50 ns and 150 ns. This study reveals that a higher breakdown voltage (BDV) occurs at longer rise times, consistent with previous research, except for 150 ns, in which the expected effect was not observed. Results showed that BDV decreases with frequency increases beyond 20 kHz. For 75 kHz and a rise time of 125 ns, BDV reduces by 30 % to that of 10 kHz.
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This content will become publicly available on September 14, 2026
Influence of Square Wave Frequency on Breakdown Voltage of Silicone Gel in Comparison with DC and AC Conditions and the Associated Mechanism
The escalating adoption of wide-bandgap (WBG) semiconductor devices in power electronics has led to the generation of high-frequency, high-slew-rate voltage waveforms, which exert significant stress on encapsulating materials such as silicone gel (SG). This study systematically investigates the breakdown performance of SG under DC,60 HzAC, and highfrequency square wave excitations. Breakdown voltage assessments were performed across a frequency range of 10 to 50 kHz for square pulses with 100 ns rise time, revealing a pronounced decline in dielectric strength as frequency increased. Specifically, the breakdown voltage measured under DC conditions, which was 20.6 kV, diminished by 84.9 % when subjected to a square wave excitation at 50 kHz. Furthermore, electric field simulations elucidated the phenomenon of localized field intensification occurring near the needle tip, which corresponded with the identified breakdown locations. The key revelations from this research underscore the limitations inherent in conventional testing methodologies, which fail to adequately characterize the degradation behavior of SG under realistic high-frequency fast-rise square voltage stress conditions.
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- Award ID(s):
- 2306093
- PAR ID:
- 10652893
- Publisher / Repository:
- IEEE
- Date Published:
- Page Range / eLocation ID:
- 201 to 204
- Format(s):
- Medium: X
- Location:
- Manchester, United Kingdom
- Sponsoring Org:
- National Science Foundation
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