Semiconductor Switches in a Counterpulse Capacitor Bank

The operation of counterpulse capacitor banks has specific features which stand in the way of ensuring reliable functioning of the semiconductor switches. These features are as follows. Its operation is in the surge current mode, in which the semiconductor switches may become overheated, with the ensuing thermal breakdown of the semiconductor. The discharge process ends with blocking of the switches and current interruption in the circuit containing inductance. The resulting high-voltage spike may bring about electric breakdown and failure of the semiconductor switch which had been overheated by the high surge current. This paper studies these features and examines the ways capable of providing reliable operation of pulsed-power thyristors and light-triggered thyristors as discharge switches. The ultimate current loads were derived by analyzing thermal generation peaks in the curves of direct-voltage drop across the thyristors. The methods and equipment employed to suppress switching overvoltages are discussed. Specific snubber circuits which provide suppression of overvoltages and protect the thyristor against pulses with an inadmissibly high current rise rate have been developed and tested. The possibility of reliable operation of semiconductor switches in a counterpulse capacitor bank has been demonstrated.