Investigation of shock pressures in high current spark gap electrodes



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Texas Tech University


Generally, the limiting component in a pulsed power system is the switch This is due to the fact at some point, the switch transfers all of the energy in the system High voltage and current create a rough environment for switch electrodes and insulators. In previous studies of switch reliability and lifetime, electrode erosion has received much attention. This investigation deals with the mechanisms behind electrode fracture, which presents an immediate problem, rather than erosion, which has long-term effects on switch performance.

The switches under study are spark gaps with graphite electrodes. The spark gap closes when an electric arc forms between the electrodes, and current conduction begins Strong mechanical forces are generated as the arc forms and impact the electrodes. The purpose of this research is to determine the dominant pressure mechanism of electrode fracture, and the propagation of the pressure wavefront through the electrode.

Energy is stored in a 5 kJ, 60 kV capacitor, and shorted through the spark gap. This is done to duplicate prior experimental work at Physics International Company. Operating parameters, such as gap spacing, air pressure, charging voltage, inductance, and magnetic pulse shaping, are varied, and mechanical pressure is measured using a strain gage mounted on a ceramic bar. Experimental data from the strain gage is compared to theoretical modeling done in Mathcad and PSPICE.



Electrodes, Electric spark gaps, Electric switchgear