GB735261A - Improvements relating to mechanical rectifiers - Google Patents

Abstract

735,261. Rectifying. EMAG ELEKTRIZITATS-GES. June 25, 1953 [June 21, 1952], No. 17654/53. Class 38 (2). In a mechanical contact rectifying circuit which may comprise a three-phase transformer 1 supplying load 3 through a smoothing choke 4 and main contacts 2, each of which has in series with it a smoothing choke 7, an auxiliary arc rectifier 5 capable of withstanding high overloads in series with a source 6 of auxiliary voltage, is connected in parallel with each con. tact 2 and associated choke 7. The auxiliary rectifier 5 is made conducting towards the end of each half cycle of current through that phase, and the main current is carried by the auxiliary rectifier 5 for 5-10 electrical degrees, the auxiliary voltage source 6 supplying the voltage drop across rectifier 5 and a small additional voltage which is developed across the switching chokes by the main transformer windings in the absence of the parallel circuit, so that the choke 7 can be wound for a much lower voltage. The auxiliary voltages may be derived from tappings on transformer 1 and when the auxiliary rectifiers are ignitrons as shown, the igniting voltages may be taken from additional contacts on the main switches. With this arrangement, the duration of contact of switches 2 may remain constant whatever the setting of contact closure time for determining the output voltage.