ZA805479B - A circuit arrangement for and method of suppressing firing pulses of thyristors connected in parallel - Google Patents

Abstract

1. Switching arrangement for suppressing ignition pulses for thyristors which are connected in parallel in bridge arms and which are fed via a rectifier bridge circuit connected to a rectifier transformer during a commutating operation that utilises a control unit for the thyristors, in which one component (1) is fed with a voltage supplied by a saw-tooth generator together with a synchronisation voltage to the unit so as to provide a comparison voltage in conjunction with a predetermined control voltage supplied by the current regulator for forming pulse blocks, whereby the component (1) controls a pulse generator (7) for the generation of ignition chain pulses, characterised in that - a logic connection in the form of an AND member (5) is connected in series with the pulse generator (7), - a first input of the logic connection (5) is connected with the negating output of an or else circuit (6), the one input of which is connected to the one output (12) of the component (1) for forming pulse blocks and the other input of which is connected with a first comparator (9) that is equipped with a switching hysterisis and is actuated by means of the secondary voltage of the rectifier transformer, - a second input of the logic connection (5) is directly connected to an output (11) of the component (1) for forming pulse blocks and - a third input of the logic connection (5) is connected with the output of a second comparator (4) which is coupled to the saw-tooth generator (2) by means of an inverter (3).