High Coulomb Single Stage Opening Switches
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Homopolar generators (HPGs) are modern day energy stores capable of producing large currents (megamps). The generators are typically low voltage, high-capacitance devices with correspondingly slow rise times, and so are unable to directly drive loads requiring fast rise times. A switch must be provided to first transfer energy from the HPG to an inductive energy store and then open to commutate the current to the load. Charging an inductive energy store with large currents for long times requires a massive switch to provide low charging resistance, yet the switch must open and commutate the current to the load in tens of microseconds, typically a feature of a light, fast-acting device. The use of explosives allows the integration of both features in single-stage switch. The Center for Electromechanics at The University of Texas at Austin (CEM-UT) has developed two high coulomb, single stage opening switches for rai lgun applications. The first switch is a monolithic aluminum element with machined stress concentrations actuated by 100 gr/ft detonating cord; the second uses reloadable cartridges mechanically clamped and explosively actuated with 15 gr/ft detonating cord. Both switches develop in excess of 1 kV/gap with comparable long term holdoff. This paper reviews the development and excellent performance of these switches.