Impedance matched 20kV solid state switch for fast direct switching

A well-known pulsed power circuit providing pulses with short rise and fall times is based on switching a pulse forming line (PFL) to an impedance matched load [1]. When the load requires higher electric fields, the generator voltage and thus the voltages to be switched needs to be increased. For insulation reasons, increasing the system voltage leads to bulkier pulse generator components with presumably larger stray inductances, which in turn lead to longer current rise times. Furthermore, large components may increase the pulse traveling time which let mismatching effects even more come to the fore. One way of reducing the component’s inductive effect on the rise time and in parallel reducing reflections is to create a high voltage switch that fits to the system’s impedance. A first 20kV switch prototype has been designed to investigate the impedance mismatching caused by the switch. This prototype was tested in a specially designed pulse forming line test circuit, capable of operating on load impedances between 50 Ohms to 10 Ohms, respectively switching currents of 200 A to 1 kA. This paper will outline the results of this study and give details about the optimum design developed to achieve best performances.