Static current converter with bypass members

Claim 1

Current converter comprising a three-phase rectifier bridge (1-6) having a plurality of rectifiers in each phase and a member (11) arranged in parallel with the bridge to bypass the DC side thereof, means for transferring current from said by-pass member (11) to two series-connected rectifiers (2,5) in one phase of the bridge so that they may act as by-pass rectifiers for the current converter, said means comprising a control circuit (7) for said series-connected rectifiers (2,5) to ignite such rectifiers and means to facilitate ignition of the two bypass rectifiers when the bypass member is opened in connection with a reconnection of the converter, comprising a firing device for at least one additional rectifier (6) of the bridge to ignite such additional rectifier, said firing device having such a delay angle that the internal direct voltage of the rectifier bridge will be positive seen in the conducting direction of the rectifiers, said current transferring means operating before deblocking of the current converter to connect said control circuit (7) to said two seriesconnected rectifiers (2,5), then to actuate said firing device (9) to ignite said rectifier (6) thereby causing current to flow through said bypass member in a direction opposite to the current therein to reduce the current substantially to zero, and then to open said bypass member (11).