ICCOS Counter-Current Thyristor High-Power Opening Switch for Currents up to 28 kA

Inductive energy storage systems require opening switches, being technically much more difficult to realize than closing switches. Most advanced state-of-the-art semiconductor devices, namely integrated gate-commutated thyristors (IGCTs), are capable of breaking currents in the order of 4 kA. However, the ISL has developed a high-power opening switch based on standard high-power thyristors and using our so-called ICCOS counter-current commutation principle. These ICCOS opening switches, being capable of interrupting pulse currents up to 28 kA, exploit the general property of thyristors that falling short of the holding current puts a thyristor into its blocking state. For this, a well-dimensioned counter-current pulse is injected, via an elaborate circuit, into the thyristor being in its conducting state. A 50 muF capacitor is used as counter-current pulse source, as well as a fast current rise thyristor and a fast recovery diode for the counter-current subcircuit. The counter-current energy stored in the dedicated capacitor is not lost in the switching process but fed into the load, in addition to the main circuit energy. The realized ICCOS switch-off time is about 30 mus.