An IGBT-Based High-Voltage Crowbar for Minimizing the Fault Current Interruption Time and Injected Fault Energy During the Vacuum Arc Fault in Microwave Tubes

In conventional high-voltage power supplies used for driving the microwave tubes, the shunt crowbar, which generally consists of series-connected thyristors, protects the microwave tube against the vacuum arc fault. In the case of arc fault, the thyristor-based crowbar is closed as a parallel path and diverts the fault current through itself. It avoids serious damage to the microwave tube. However, thyristor switches usually have a limited rate of rise of ON-state current (di/dt), which necessitates placing a series inductor in the crowbar path. Thus, satisfying all protection limits of microwave tubes-including the injected fault energy and the fault current interruption time-is a challenging task for the thyristor-based crowbar. In this article, an insulated-gate bipolar transistor (IGBT)-based crowbar is employed to overcome this problem. Taking the advantages of IGBT switches, the proposed crowbar satisfies all the protection limits of the microwave tubes. Theoretical analysis, simulation studies, and experimental tests are utilized to compare the crowbar performance in the presence of the conventional crowbar and the IGBT-based crowbar.