Single shot and burst repetitive operation of thyristors for electric launch applications

Electric gun applications require switches with simultaneous high peak currents, di/dt, and action capability. The development by Silicon Power Corporation (SPCO) of a 125 mm diameter symmetric thyristor which utilizes a unique compact package with decreased thermal resistance from junction to sink has addressed the thermal resistance problem and conduction area limitations. The development of the reversely switched dynistor (RSD), an asymmetric thyristor, by the Ioffe Institute in Russia, has addressed the commutation power dissipation problem by using a unique and highly interdigitated gate structure in the anode and a high current driver. Tests were conducted on both types of devices by discharging a low impedance pulse forming network (21 mF or 17 mF total capacitance) via the device under test into either a matched load or a short. Test peak current varied from 151 kA to 221 kA. Testing was performed, in the same test circuit as the 125 mm thyristor, on an 80 mm diameter RSD. The paper places in perspective the overall performance of these devices and the implications for future designs and applications. The implication of this work is that combining the design principles of both types of devices to the solution of the thermal limitations of thyristors could increase the peak current capability of a 2.5 kV 125 mm symmetric thyristor by a factor greater than 2 and the di/dt by an order of magnitude. Specifically, the thyristor should reliably switch, into a shorted load under repetitive conditions, a 0.5 ms duration pulse with a peak current of 400 kA and a di/dt of 25 kA/μs