Current commutated two quadrant thyristor chopper

A thyristor chopper capable of operation in two quadrants (positive or negative output voltage, positive output current) from a fixed voltage d.c. input, is described in this paper. An optimum control strategy for controlling the average output voltage of the chopper is given. A commutation circuit for the turn-off of thyristor switches has been described. The circuit uses the principle of current commutation which requires small commutation components. The commutation circuit has been analysed in detail using simple equivalent circuits. A design procedure based on this analysis has been given. The results of the analysis have been verified on an experimental lOkw chopper system.