Impact of Frequency and Rise Time on Breakdown Voltage of Air in Needle-to-Plane Geometry Under Square Wave Voltage Pulses

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.