Characterisation of plasma closing switches filled with different gases

  • Caron McGarvey

Student thesis: Doctoral Thesis

Abstract

Sulphur Hexafluoride (SF6) is one of the most commonly used gases within switching applications for pulsed power applications due to a large number of desirable properties, however, it is a greenhouse gas and global concerns over the emission of this gas into the atmosphere have led to an increase in research into potential environmentally friendly alternatives.This study focused on an experimental investigation into the breakdown characteristics of two commonly used plasma closing switch topologies when filled with different gasses and gas mixtures not previously considered in as much depth for switching purposes (air, N2, 60%/40% N2/O2, 90%/10% Ar/O2, and CO2) as compared to the characteristics of the switches when filled with SF6.A self-breakdown switch and a field-distortion triggered switch topology with varying inter-electrode gap lengths up to 9mm, filled with gasses at pressures in the range 0.1MPa-0.5MPa were studied and some key operational characteristics and switching parameters such as the self-breakdown voltage of the gases, the spread in self-breakdown voltage, time to breakdown and jitter of the switches were investigated and compared.Temperature of the plasma that forms during breakdown and the conductivity of plasma was extracted for each gas and in addition to this, analysis of post-breakdown waveforms allowed for obtaining values of inductance and resistance of the switches.Experimental results have been used in the development of two computational models of Marx Generators which are used in the voltage erection stage of pulsed power systems. The models developed describe the switches as either having constant resistance or taking into account the transient plasma resistance which allows for a more accurate representation of the voltage and current behavior across the output load over the first quarter of the current oscillation after switch closure occurs.
Date of Award1 Apr 2016
LanguageEnglish
Awarding Institution
  • University Of Strathclyde
SponsorsUniversity of Strathclyde & AWE plc
SupervisorScott MacGregor (Supervisor) & Igor Timoshkin (Supervisor)

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