High Frequency Breakdown in Partial Pressure

High frequency breakdown in a partial vacuum: Most electric power systems are designed for earth-bound operation, but they do not behave the same way in aerospace and space environments. The most important effects are related to insulation failures at kHz-range frequencies. Due to the vast advances in semiconductor devices, power systems today use high power semiconductor devices that can operate in kHz switching mode with higher power levels and efficiency. The most common high voltage signals observed in high-frequency (kHz range) in power systems are due to switching circuits in commercial applications like inverters and power converters.

Power systems operating in space and aerospace environment conditions are subject to different stresses than the ones under “normal” atmospheric conditions [1]. When these power systems are operated in space and aerospace environments, electrical breakdown becomes a major concern mainly due to the high electric field stress levels and low operating pressure. These, coupled with high density packaging and limited ability to use heavier dielectric materials, cause electrical breakdown to be a major limiting factor in power systems operating under high switching frequencies [2]. Therefore, most systems designed for earth-bound operation are not suitable for operation under partial atmospheric pressure.

Dr. Kirkici’s research focuses on specific topics that are important for the development of advanced space-power or aerospace-power systems. Her group has provided data on the breakdown characteristics of helium and nitrogen under unipolar-nonuniform pulsed voltage at varying frequencies in partial vacuum [3]. It is shown that high frequency breakdown voltage is lower than the dc breakdown voltage under the same conditions. Breakdown voltages of helium and nitrogen as a function of signal frequency exhibit a “Paschen” curve-like behavior and show the limits of and deviation from the classical “Paschen” law for practical systems with divergent and/or ac and pulsed fields [4]. This data must be considered in the design of reliable space power systems, as well as the design of microelectronic devices, e.g. transistors and sensors, exposed to low earth orbit vacuum conditions.

• [1] H. Kirkici, (Invited talk)“High Voltage Insulation in Space Environment and Design Guideline,” Proceedings 2006-IEEE-PMC, Page(s):33 – 37, 14-18 May 2006.
• [2] Hulya Kirkici, (invited talk), “High Frequency Breakdown and Electrical Insulation in Space Environment,” 8th International Conference on Optimization of Electrical and Electronic Equipment 2002, Brasov, Romania, May 16-17 2002.
• [3] K. Koppisetty, H. Kirkici, D. L. Schweickart, “Partial Vacuum Breakdown Characteristics of Helium at 20 kHz for Inhomogeneous Field Gap” IEEE Trans. on DEI, Volume 14, Page(s):553 – 559, June 2007.
• [4] K. Koppisetty and H. Kirkici, “Breakdown Characteristics of Helium and Nitrogen at kHz Frequency Range in Partial Vacuum for Point-to-Point Electrode Configuration, IEEE Trans. on DEI, Volume 15, Page(s):749 – 755, 2008