Патент USA US2117993код для вставки
May 17, 1938. D. G. PRINZ 2,1 17,993 ELECTRINC DISCHARGE DEVICE Filed June 29‘, 1937 IIVYENTWR. Patented May 17, 1938 , 2,111,993 ' UNITED ‘STATES PATENT OFFICE 2,117,993 ELECTRIC DISCHARGE DEVICE Dietrich Giinther Prinz, Wembley, Middlesex, England, assignor to The General Electric Company. Limited, London, England, a company of Great Britain ' Application June 29, 1937, Serial No. 150,897 In Great Britain July 3, 1936 8 Claims. (Cl. 175—354) This invention relates to‘means for operating electric discharge devices, such as mercury va by this voltage until the main discharge is es _ tablished. por devices, of the type having a cathode from which vapor is generated during operation, from Certain embodiments of the invention will now be describedL by way of example, ‘with ref-' an approximately sinusoidal A. C. supply, so that ' erence to the accompanying drawing. Of these, the‘ arc, which has to be started in each cycle, Figures 1, 2 and 3 show, by way of example, var can be started at a controlled point in the cycle. ious circuits for the production of the ignition It has been proposed to start an arc to the peak voltage and for the supply of voltage to mercury cathode of a mercury arc device by ap the auxiliary electrode. plication of high voltage to an inner auxiliary electrode. This involves, however, either incon veniently high voltages or frequencies or vapor by way of‘ example, some arrangements‘ and 10 shapes of the auxiliary electrode. In Figure 1, the discharge device consists of a glass envelope I, containing a mercury pool pressure, or special arrangements, such as aux iliary hot cathodes. Figures 4 and 5 show, ’ 2 with a cathode lead 3, an anode 4 and an inner It has been proposed also to start an are by means of an external ignition electrode, for in ‘auxiliary electrode 5. - This electrode 5 may con 15 sist of a simple wire. sealed throughthe glass stance, a metal foil, ?xed on the' glass wall near wall,‘ or of a ring (as shown), or it maybe of the mercury surface. In this case, a cathode spot _ any other suitable shape, of which examples are is very easily formed on the edge of the mercury given in the modi?cations later described. probably due to the abnormally high electrical 'The external electrode 6 may consist of a wire ?eld arising at this sharp edge. ' ' or other metal body, touching the glass near the This method of ignition, however, has some considerable disadvantages. Since the main anode circuit always contains a certain self inductance, theanode current will increase, not suddenly, but at a '?nite rate. On the other hand, a minimum current of about 1 ' ' or 2 amps. is required for maintaining the oath 0 mercury edge, but preferably of a metal foil ' ?xed on the glass and surrounding the whole mercury pool. ' _ Both the auxiliary electrode 5 and the exter 5 nal electrode 6 are connected with one terminal of the high voltage winding of a transformer l,. the other terminal of the said high voltage wind ing being connected with the cathode lead 3. ‘In the connection between the electrode 5 and the ode spot. Therefore, since the duration of the spot is very short, the spot may be extinguished before‘ a current sufiicient to maintain it de said winding, there may be inserted a resistance ' velops. I‘, if desired. ’ 7 > Another disadvantage of forming a cathode The primary winding of the transformer 1 is spot solely by means of an external electrode is connected with the A. C. source 8 through a re that, if the anode be placed far from the cathode sistance 9 and a gridglow tube In, the grid of (for‘instance, to protect it against evaporated or which is connected with its cathode, through sputtered mercury), the main discharge may not, the secondary winding of a transformer II be able to start from the cathode spot to the main (which is preferably a peak transformer of the anode, owing, for example to negative charges 40 formed on the glass walls or other'insulators be tween cathode and anode. , . The object of the present invention is to pro vide means for starting the discharge free from the disadvantages of either of these two methods. According to the invention, means for the pur pose speci?ed comprise as part of the said elec tric discharge device, both an external electrode near the cathode and an internal auxiliary elec trode, impulsive means for applying to the said external electrode an impulsive voltage, where by a cathode spot is formed, and maintaining means for applying to the said internal auxiliary electrode a voltage of such magnitude, sign and 56 duration that the cathode spot is maintained saturated iron core type) and a D. C. source It‘. The primary winding of the transformer ll , 40 is fed by an A. C. source ll of the same fre— quency as the A. C. source 8 and as the, supply to the main circuit. This main'circuit is shown in Figure 1 as an A. C. source _a connected through a transformer b with the electrodes 3 and l of the discharge devicel in series with a D. C. load c. The main circuit need not be as shown in Figure 1, but may be of any kind usual with vapour electric devices of the type speci?ed. The secondary voltage of the transformer II, in cooperation with the D. C. source l2, ren ders the grid glow tube It) conductive, in known manner, at a definite moment of each cycle, so that an impulsive current then flows through the primary of the transformer 1. This impul 65 2,117,998 2 sive current produces a high voltage on the sec ondary of the transformer ‘I, so‘ that the exter nal electrode 6 forms a cathode spot on the edge of the mercury pool. BI At the same moment, ‘a discharge is started between this cathode spot and the inner auxiliary electrode 5; this dis charge is maintained for a ?nite time by the‘ magnetic energy stored in the transformer ‘I. If the transformer be suitably designed, this en 10 ergy will be great enough to -maintain the dis charge to the electrode 5, until the main dis charge to the anode 4 is established. The A. C. sources 8 and I3, or the A. C. source I3 only, may be provided with phase shifting 15 devices of known kind, so that the moment of ignition in each cycle may be varied in a man ner well known in connection with all grid con trolled converters and thus the mean current tween the external electrode 6” andthe cathode 3"; its peak then must be made sharp enough and high enough to produce a cathode spot on the mercury. But preferably, as ‘shown 'in the ?gure, the voltage on the external electrode 6” is made to rise still more sharply by inserting a spark gap I8 between the secondary winding of the transformer ‘I" and the electrode 6"‘. The spark gap I8” may consist of a point separated from a plate by a distance such that only the‘ 10 positive voltage peaks can break down the gap and reach the electrode Ii". In this case, a re sistance I9" may be provided to remove the elec trical charges from the electrode 6" in the inter val between the peaks. 15 The means for applying a voltage to the auxil iary electrode 5’ which are shown in Figure 2 by the numerals I4'—I'I’ may be used in the are rangement shown in Figure 1 in substitution for varied. 20 Figure 2 shows another example of a circuit the connection of the electrode 5 through the re 20 according to the invention. Reference numerals ' sistance I4 with the secondary winding of trans I’—8’ have the same meaning as I-B, in Figure 1. former ‘I. The peak voltages of the A. C. source 8' ‘cause As mentioned above, it may be sufficient some- . sparks to pass across the spark gap 9’, thus charg 25 ing the condenser I0’ and causing a heavy current impulse to flow through the primary winding of the transformer ‘I’; a voltage peak therefore oc ours in the secondary winding of this transformer and a cathode spot is formed by the external times to form the auxiliary electrode as a simple wire sealed through the glass wall; in other cases, 25 it is preferable to give it a form that enables it to ' perform other functions as well. 30 electrode 6 as described above. tering from the cathode spot. In this ?gure, the glass envelope 2| contains an anode 22, sealed and supported at 23, and an auxiliary electrode 24, sealed into and‘ supported by a foot-tube and pinch 25. The annular depression formed by 35 sealing the foot-tube to the glass envelope is ?lled with mercury 28, for which a leading-in wire 21 is provided. The annular form of the mercury pool has the advantage of increasing the length It may be pointed out that two sparks occur in each cycle, thus producing one positive and one negative voltage peak on the external electrode 6'. Only the positive peak is used to form the 35 spot. By inserting a second transformer in the circuit ‘I’, 8’, 9’, III’, the second spark may be used for forming another positive voltage peak, so that another dischargedevice may be ignited alternately with the device I’. This arrangement 40 may be useful in known symmetrical recti?er cir In Figure 4, for example, the auxiliary elec trode is formed as a baf?e or screen protecting the anode from the vapour stream and the sput of the mercury edge for a given amount of mer 30 40 cury; a metal foil forming the external electrode cuits, fed by 2-phase, 6-phase or 12-phase sup can be applied not only on the outer side 28, but plies. If the A. C. source 8' be provided with a ' also on the inner side 29 of this-mercury pool. phase shifting device, ‘only one such device is Furthermore, its presence on this inner side required for each pair of recti?ers. makes it easy to cool the mercury (for example In Figure 2, a D. C. source I4’ is connected by a blast of air); cooling is known to promote through a resistance IS’ with a condenser I6’, formation of cathode spots. ' this condenser in turn being connected with the theThe diameter of the auxiliary electrode 24 is auxiliary electrode 5’ through an impedance I1’. As soon as the cathode spot is formed by the greater than that of the anode 22 and that of the mercury pool 26, so that the‘anode is protected 50 external electrode 6’, a discharge takes place be tween the mercury cathode 2’ and the auxiliary from the vapour stream produced by the cathode spot as well as from any sputtered mercury. electrode 5’, the duration of said discharge de In Figure 5, another shape of the auxiliary pending on the values of the condenser I6’, the electrode is shown. In this ?gure, the glass vessel ‘resistance I5’, the impedance I1’ and the voltage of the D. C. source I4’. If these values be chosen 30 contains in aside arm 3| an anode 32 sup ported by a rod 33 sealed in at 34, the said rod suitably, the auxiliary discharge will be main being protected by a quartz sheath 35 held in tained until the main discharge has been estab vposition by washers 36 and a spring 31. 38 is lished. mercury pool, and 39 is the cathode lead. In the succeeding non-conductive part of the the The auxiliary electrode 40,'supported on a lead 60 60 cycle, the condenser I6’ is recharged by the D. C. sealed in at 42, is formed as a grid surrounding source I4’ through the resistance I5’. This re the anode 32. This arrangement facilitates the sistance must be high enough to prevent a con tinuous arc discharge taking place between the starting of the discharge between the cathode and anode; and, if the discharge tube be used as a auxiliary electrode 5’ and the cathode. The impedance I'I’ need not be a pure ohmic recti?er, it also decreases the risk of back ?ring during the inverse half cycle. When using a cir resistance; it may be replaced by a self induct cuit according to Figure 1>or 2, the potential of ance; indeed it has been found that in this way a more uniform duration of the auxiliary dis charge can be obtained. In Figure 3, the reference numerals I"-8” and I4"-—I'I” have the same meaning as I'--8’ and I4’-I'I’ in Figure 2; but the transformer 'I" is a peak transformer of the saturated iron core type, producing an impulsive voltage. Its sec ondary winding may be connected directly be the auxiliary electrode never differs very greatly from that of the cathode during the inverse period; the electric ?eld tending to produce a 70 reverse discharge is con?ned to the space between the anode and auxiliary electrode. On the other hand, a back discharge between the anode-and the auxiliary electrode is improbable because these electrodes are near together and, in the cir 2,117,993 cult according to Figure 1, because of the resist 3 vided by a transformer the secondary of which is arranged to supply a unidirectional impulse ance of the transformer windings and the addi tional resistance ll inserted in the lead to the . current derived from an alternating‘current of auxiliary electrode 5. I claim: 1. In a mercury vapor discharge device, a tube having an anode and a cathode, the cathode com prising a pool of mercury from which vapor is ' generated during operation, a main circuit carry 10 ‘lng alternating current of known frequency con nected for discharge between the anode and cathode of said tube, said main circuit including a direct current load, an external electrode ar ranged to cooperate with the mercury pool of the cathode in the formation thereon of a oath. ode spot, a circuit between said external elec trode and the cathode carrying an impulse cur rent for establishing a positive potential on the external electrode during each cycle of the al ternating current in the main circuit for form ing the cathode spot on the mercury pool, an auxiliary electrode mounted within the tube be tween the anode and cathode for cooperation 5. The mercury vapor discharge device as in claim 1 wherein the impulse current for forming the cathode spot on the mercury pool is provided by the secondary of a saturated core transformer the primary-of which is supplied with impulse current of proper frequency from an alternating current source with a‘ condenser and‘ spark dis charge in circuit. 6. The mercury vapor discharge device as in claim 1 wherein the impulse current for forming the cathode spot on the mercury pool is pro vided by the secondary circuit of a saturated core transformer which circuit includes a undirec-' tional spark discharge, the primary of the trans former being supplied from an alternating cur rent of proper frequency. ‘ with the cathode spot, and circuit means ar ranged to provide an impulse current for dis 7. The mercury vapor discharge device as in claim 1 wherein the impulse current for the dis 25 charge between said auxiliary electrode and the cathode spot for maintaining, the cathode spot until the main circuit discharge is established. charge between the auxiliary electrode and the cathode spot is provided by a condenser arranged 2. The mercury vapor discharge device as in 30 claim 1 wherein the current for providing the im pulse discharge between the auxiliary electrode and the cathode spot is derived from the cir , cult which is arranged to form said cathode spot on the mercury pool. 3. The mercury vapor discharge device as in claim 1 wherein the impulse current for form ing the cathode spot on the mercury pool is pro vided by the secondary of a transformer the pri mary of which is supplied with unidirectional 40 proper frequency and the impulse current for the discharge between the auxiliary electrode and the cathode spot is provided by a branch circuit from the secondary of said transformer. impulse current produced by passing an alternat ing current of proper frequency through a glow tube recti?er. 4. The mercury vapor discharge device as in claim 1 wherein the impulse current for forming 45 the cathode spot on the mercury pool is pro to be charged from a direct current source and to be discharged between the auxiliary electrode and the cathode spot with the formation of the 30 cathode spot. - 8. The mercury vapor discharge device as in claim 1 wherein the impulse current for forming the cathode spot on the mercury pool is provided by a transformer the secondary of which is ar 35 ranged to supply a unidirectional impulse cur rent produced from an alternating current of proper frequency and the impulse current for the discharge between the auxiliary electrode and the cathode spot is provided by'a condenser arranged 40 to be charged from a direct current source and to be discharged between the auxiliary electrode and the cathode spot with the formation of the cathode spot. __ - DIETRICH GUNTHER PRINZ.