Rotary spark gap switches for pulsed power applications

This paper presents the work undertaken to develop and test a family of rotary spark gap (RSG) switch designs, suitable for a wide range of pulsed power applications. These use a 12 V DC motor and a number of interchangeable electrodes to operate at different pulse repetition frequencies (PRFs). The first implementation (RSG Mk I) is a simple design developed for testing different rotary switch topologies, and will not concern this study. The second (RSG MkII) can be charged up to a voltage of 60 kV, whilst the operating range can be altered by changing the gas type or pressure of the switching medium. For this switch, inter-electrode electrical field simulations were performed followed by the measurement of the operation range characteristics for various rotating and stationary electrode combinations. The third (RSG MkIII) uses atmospheric pressure air for switching medium and is capable of operating at much higher discharge currents and charge transfer levels, but at a lower charging voltage of 35 kV. The operating range for this switch can be adjusted simply by altering the position of the stationary electrodes. For the RSG-MkIII design, apart from the determination of the charging voltage operation range, an electrode erosion and lifetime performance investigation was conducted with different electrode materials such as aluminum, brass and stainless steel. The results demonstrate that rotary spark gaps offer a simple and low-cost alternative compared to other switching devices for pulsed power applications.