GB407589A - Improved arrangements for producing alternating currents using discharge devices - Google Patents

Abstract

407,589. Converting. ALLMANNA SVENSKA ELEKTRISKA AKTIEBOLAGET, Vasteras, Sweden. July 7, 1933, No. 19318. Convention date, July 8, 1932. [Class 38 (ii).] In an inverter or frequency changer using a discharge device, commutation is effected by means of an auxiliary anode to which a voltage is applied which causes the arc to be transferred to it from a conducting anode, the voltage then being reduced to cause the arc to transfer to another main anode. In an inverter arrangement Fig. 1 for interconnecting a D.C. circuit 1 and an A.C. circuit 2 a source 3 of periodic potential having a waveform as shown in Fig. 2 is connected between the centre point of the primary 15, 16 and an auxiliary anode 4 having a control grid. At the moment of commutation the anode 4 is given a higher potential with respect to the cathode 13 than (e.g.) the anode 5 and the arc transfers from the anode 5 to the auxiliary anode 4, retransference of the arc to the anode 5 being prevented by grid-control. The voltage of the anode 4 is then reduced and the arc transfers to the anode 6. The source 3 of periodic potential may be a condenser which is periodically charged from a battery. In a further modification the source 3 consists of a condenser bridged by a choke in series with a grid controlled valve. Fig. 5 shows further modification in which the periodic potential is obtained from an oscillatory condenser circuit 7, 10, 11 coupled to the auxiliary anode circuit through a transformer 19. The condenser 7 is discharged through a further auxiliary anode 12, the moment of discharge being determined by grid control. In a frequency changer as shown in Fig. 6 each pair of anodes 35 associated with one of the phase windings of the transformer 31 is provided with an auxiliary anode 34.