Single shot and burst repetitive operation of involute gate 125 mm symmetric thyristors up to 221 kA with a di/dt of 2.0 kA//spl mu/s

Abstract

Previously (1998), the authors reported on the operation and limitations of a six-point star gate design 125 mm thyristor pulsed power switch. An involute gate design has been developed that provides a significant increase in its ability to handle higher peak currents and di/dts. For this study, they selected a 2.5 kV symmetric version of the device. The test facility uses a 10 m/spl Omega/ PFN with a rectangular pulse width (FWHM) of 465 /spl mu/s. All tests were performed with an essentially shorted load in order to achieve 200 kA operation and to instantaneously apply a full voltage reversal in less than 3 /spl mu/S at the end of the current pulse. Reliable operation was demonstrated at 2.6 kV forward voltage with a reverse voltage of 2.3 kV. The peak current was 203 kA with a di/dt of 1.8 kA//spl mu/s. The charge was 82 C and the action was 13.8 MA/sup 2/s. The reverse charge was 0.19 C. The PFN was modified to reduce the impedance and simulate a sinusoidal pulse in excess of 1 kHz. Reliable operation was obtained at 221 kA with a di/dt at 2.0 kA//spl mu/s. The pulse width (FWHM) was 301 /spl mu/s. With a base width of 455 /spl mu/s. Forward voltage was 2.4 kV with a reverse voltage of 2.3 kV. The forward charge, reverse charge and action were 63 C, 0.51 C and 10.9 MA/sup 2/s respectively. Reliable repetitive operation was performed at 151 kA with a burst of 10 pulses and a 20 second interval between pulses. No temperature effects were observed.