An inverter providing simultaneous commutation of all thyristors

This paper describes a new inverter configuration in which all thyristors are simultaneously commutated by means of a single transformer coupled commutation stage. This results in improved compactness, simplicity, and reliability with respect to existing configurations. The proposed inverter configuration also offers the following features: a) Rate of rise of short circuit currents is inherently limited by transformer windings in the power stage. b) Failure of a main thyristor does not result in the destruction of any other components. c) The system can operate over a wide range of passive and regenerative load power factors. d) The main thyristors are soft commutated and thus do not suffer the derating associated with hard commutation. e) The main thyristors are not derated by commutation current pulses or voltage overshoots. The operation of this system is described and equivalent circuits for the various operating modes of a commutation cycle are analyzed. A design procedure is presented whereby commutation components can be selected.