GB429060A - Improvements in or relating to electric arc converters - Google Patents

Abstract

429,060. Converting; arc converters. MARX, E., 3, Rankestrasse, Brunswick, Germany. March 21, 1934, Nos. 8866 and 8867. Convention dates, March 21, 1933 and Nov. 11, 1933. [Class 38 (ii)] [See also Group XL] An arc converter in which arcs are produced between elec. trodes in a gaseous fluid comprises at least one auxiliary electrode and is provided with auxiliary means foi producing arcing be. tween the auxiliary electrode and one or both main electrodes so that periodically the auxiliary arc bridges or substantially bridges the main electrode gap causing breakdown thereof. In one arrangement, Fig. 1, the auxiliary electrode 4 is supplied periodi. cally with starting voltage from a condenser 10 through the rotary spark-gap 12 which rotates in synchronism with the frequency of the main circuit 13. Auxiliary arcs are formed between 4 and the main electrodes 2, 3 which are connected in the main circuit 13 in series with chokes 5, 6 breakdown of the main gap being then produced and the auxiliary arc being driven from the electrode 4 by an air stream or magnetic field. The rotary spark-gap may be replaced by a fixed gap or dispensed with and higher resistances may be arranged in parallel wth the condensers 7 and 8. The starting votage may be provided by a Tesla transformer or by a magneto or coil ignition apparatus as used in internal - combustion engines. The electrode 4 may be connected to electrodes 2, 3 through equal sized high resistances to prevent breakdown of the main gap in the reverse direction and may be cooled and suitably shaped for the same purpose. In an alternative arrangement, Fig. 5, the auxiliary electrode 38 is adjacent the main electrode 36 which with main electrode 37 is in circuit with the load 35. An auxiliary A.C. source 41 is connected across the auxiliary gap and breakdown of this gap is effected periodically by high frequency voltages produced in the arrangement 42 and fed to the electrode 38 through a spark gap 39, the electrodes 38 and 37 being anodes with respect to the electrode 36. The auxiliary arc when produced is extended to bridge the main arc gap to cause breakdown thereof and is then quickly extinguished. In a converter having the electrodes in a closed chamber the ring shaped auxiliary electrode 22, Fig. 3, is arranged coaxially with one main electrode 20, and is supported through insulation 24 from a metal ring 23 which may be of iron and carry the flux of a radial magnetic field for moving the auxiliary arc and/or the main arc. Electrode members 28, 30, arranged as shown are connected respectively to the main electrodes 20, 21. The main gas stream 26 flows radially inwards while the gas stream for displacing the auxiliary arc flows in through the channel 25, both streams leaving through the two nozzles 27 and the channels 29. In an arrangement in which the main and auxiliary gas streams are combined, the auxiliary electrode may be arranged as a cylinder surrounding one main electrode the gas flowing in, between these two electrodes, towards the other main electrode, which may be of the form shown in the lower half of Fig. 3, and flowing out through the channel 29 to extinguish or prevent reignition of the arc at the end of the arcing period. In an alternative arrangement two electrode arrangements as shown in the lower half of Fig. 3, are arranged opposite one another, one of the ring shaped electrodes 2, which then acts as an auxiliary electrode being disconnected from the associated member 30 which then acts as a main electrode. Two modifications of the method of disposing the electrode 22, Fig. 3, in relation to the electrode 20, are also described. Ohmic or inductive impedances may be inserted in the circuit supplying the auxiliary arc which may be fed from the main transformer directly or through transformers or from a separate source. In polyphase converters the auxiliary arcs of the various phases may be supplied from a common source of suitable frequency or from the D.C. side of the converter. When a distributer is employed in the auxiliary A.C. circuit the instant of ignition may be varied by altering the phase of the distributer and of the auxiliary voltage.