High Voltage Solid State Switched Vector Inversion Generator

Abstract

A Vector Inversion Generator, VIG, consists of two parallel plate transmission lines, sharing a common conductor that have been wound on a mandrel [1,2]. These units can be made highly efficient and are capable of developing high transient voltages in a time that is determined by the two way transit time for an electromagnetic wave to propagate up the "active" line. Heretofore, the active line in a VIG device was switched using a spark gap because of the extremely high dl/dt and large values of current, I. Spark gap switches have limited life due to electrode erosion, are difficult to trigger with precision and have limited pulse repetition rate. Further, spark switches are usually pressurized to increase operating voltage and to present an inert gas to the electrodes in the switch. By contrast, solid state switches have none of the undesirable characteristics of spark switches and gas plumbing but are limited in dl/dt, I and standoff voltage. In this paper, we will describe the results of our efforts to produce a solid state, precision switched, VIG for applications at high repetition rate and at modest energies. We will present VIG design methodology that determines the maximum value of both I and dl/dt that a switch will see as a function of line length and line impedance. In order to test our methodology, we purchased a solid state switch available from Applied Pulsed Power, Inc. This switch is capable of dl/dt on the order of 30 kA/ ts, peak operating voltage of 4.7 kV, and a peak repetitive current of 10 kA. Test data at voltages greater than 1 kV at a repetition rate up to 500 Hz will be presented. At these voltages, the VIG erected to greater than 60 kV. Due to controller and reverse diode issues, we conducted limited testing at higher voltages producing VIG erected voltages on the order of 100 kV. From these tests, we designed a switch for custom fabrication by Applied Pulsed Power. The switch is to be capable of peak repetitive currents greater than 30 kA, with dl/dt greater than 100 kA/ps. Performance and characterization of this switch will be presented and discussed in terms of VIG design constraints.