On the Use of High-Power Diodes as Crowbar Switch for Capacitive High-Current Generators

A technically easy way to reproduce lightning current pulses is to use a capacitive high-current impulse generator with a crowbar switch. For the crowbar switch, commonly spark-gaps are used which can withstand the mechanical and thermal stress due to the high current pulses. The spark-gap is triggered by an external high voltage trigger-device when the oscillating current attains the maximum. For extremely high currents, it is a common method to combine two of such generators to a tandem generator. In this case, it is necessary that the crowbar switches of both generators are triggered time-synchronized and decoupled by the use of an inductance. In order to avoid the triggering and the decoupling of the crowbar switches, we replaced the spark-gaps of both crowbar switches of our tandem generator by two diode-stacks, each consisting of 25 high-power diodes. After this modification, the tandem generator is able to reproduce even extremely high lightning currents as the 10/350 μs current pulse up to a level of more than 300 kA. The use of the diode-stacks also allows to combine the high-current generator with other current generators as a long duration current generator used for the experimental simulation of the continuing currents. Because no decoupling inductance is needed and the arc of the spark gap is avoided, the tandem generator is now able to test equipment with higher inductance and resistance compared to the generator with spark-gap based crowbar switch.