Electrical breakdown of power rectifiers for electric gun applications

Experiments have been performed with a 100 kJ pulse-forming network (PFN) to characterize the transient behavior of semiconductor diodes serving as capacitor-protecting devices. In addition to the experiments, computer techniques are used to illustrate and predict the dynamic behavior of PFN diodes. From analyses of the data collected, it was determined that in a PFN under specific loading conditions, the diodes are subject to elevated transient high frequency voltage waveforms. In some experiments, the magnitude of the rate of change in voltage (dV/dt) across the devices was such that catastrophic failure was observed due to this phenomenon alone. This paper focuses on the determination of boundary conditions necessary for reliable device performance and the solutions that will circumvent diode operational failures. The authors´ solutions include semiconductor device layout, choice of diode reverse recovery time, PFN switch timing and selection of capacitive and inductive circuit parameters, all of which are presented in detail in this study. Information describing fundamental physics of semiconductor diodes under transient conditions and their role in electric gun propulsion technology is provided first to clarify the applicability of these areas of concern to the general field of very high power electronics.