Failure mechanisms of the thyristor switch in pulsed arc electrohydraulic discharges

In order to study the failure mechanism of the thyristor switch in the application of electric pulse fracturing, an underwater pulse power discharge experimental platform was built, the impedance characteristics of the plasma channel were analyzed and the circuit equivalence was carried out for each discharge stage. Then, based on the Silvaco simulation software, a theoretical thyristor model was established. By observing the distribution of the internal carriers and current density, the turnon and turn-off processes of the thyristor switch under high voltage were analyzed. The formation factors of peak voltage in the turn-off process were studied, the easy breakdown position was pointed out, and a method to suppress the reverse peak voltage by creating critical damping oscillations in the discharge circuit was proposed. Finally, a pulsed power discharge experiment was carried out to verify the theoretical analysis. The experimental results show that the discharge waveform conforms to the theoretical analysis, and the high voltage breakdown damage of the thyristor is also consistent with the theoretical simulation model. Furthermore, the proposed thyristor protection method can greatly suppress the reverse voltage spike, reduce the peak voltage by 52%, and effectively avoid the damage caused by withstand voltage breakdown in the application of pulse power discharge.