The design and test of a 500-kJ, 325-kA energy discharge bank employing solid state switching

This paper describes a 500-kJ capacitor discharge bank for driving inductive loads. The bank uses high-power thyristors as series switching elements and avalanche diodes to crowbar the load inductor at peak current. Series blocking diodes are used to prevent reverse current from flowing through the thyristors. The crowbar circuit is equipped with high power resistors used to tailor the fall time of the current pulse. The bank operates over a wide voltage range, from 500 V to 12 kV. It is designed to drive inductances of order 240 /spl mu/H, but is capable of discharging into a short-circuit load at currents as high as 325 kA, with a maximum dl/dt of 1.4*10/sup 9/amps per second. A 66-/spl mu/H inductor is connected in series with each of eight parallel thyristor stacks, to limit the short-circuit current and to ensure that the curtent is equally shared. Three thyristors are placed in series to achieve the required 12-kV operating voltage. Breakover diodes protect individual thyristors from overvoltage conditions induced by unequal voltage division along the thyristor stack.