[1]0:? ST. LOUIS, !FLISSOU--,@7, A COP,1?07.AT102T OF Specific5-ition ofretters 7-latent, 5, i@, 2 0. .t,-Dplicatio@n filed July !), 1917. SeTial 1,1'o. 173,06S. To aZZ wi@o7pit qnay co,,i.cern: Be i-t icno-,vn thci' VAI;@z-T-ZE FYLNX@ a Ing 'ding s-t-ibject oi the K-' @nDglai-i-d, res-f -'VT -)t 'fliae city of St. Lou,.s, State o' i i-ssouri, 6 7@Tni-te6@ States of Americi, have invey).' -tLe(@ q certlf,@n new use-i--Ill Dynamo-Elect@-i-c Tt@@ Ta el'ilne, of N@@ @ icli the folio-Nving is such a I cle,,ir a--qd exact @iescri-ption as -will eiiable ,iiiv one skillecl i@,,i art to 7viiieh it to make ar@c,. use the s,-@me, re-tere-@ice o,ing had to @',he Pccorq-o,iiiyi-,ig clrawirigs, iofmidg pai,@', oT' this specificitioii. i)/Iy i,-ivention re'-a-tes.@o alternate current. ge-tierators or moto3@s a-,i-d has for its objec-t to aliv @arv @.Iie current SUPDlied Le o t-4c-- mer_rlber i-.q P-ccorda-.ice -,v-,tn 7,.T @,l C@'CiOn iD. the di7,ect@o,-- and magnittide o-@' componen'L o-@L the armature rei-,c',,ion waich is coqxial wi@ilh the excitiiig fi,-Icl., or @o vary salcl@ c@,irren'@, iii the -riianner st,,ite(i ,iii0i also in accore,@qr@c-e with varie@,ioin- in @'iirection ar-,d mauni'cu-.te of compodent O'L the arr-qatlire reactio@,i - @N-hich is d-i-spl,-@eed y 90 ele@etrie,,ii clerrp-es --'crom the txis of the -5 @axeiti--@ig field. In this manner I can neil.11 irl 'ralize -th-- armature reae'lion si-icn machines for any phps-I relation bet-weer. the .1o,,.d current and 'Lhe termidal voltage. -"Then ap@lied to ge--q,?raors 4ub-is invention serves to re(iiice the of -the termi,-ip@l voli',ELre -v@,,ith vaivinly loacl substantially )Lo thal-u due @Lo 'the - ii-,q-oed,,tnce drop i-n the Tliis drop can be elimiriat-d by SLI.Lably compoundiny the a 35 m,,chine. 71%en ppi-ed to mozors it @ffects I 'Lhe poive,@ fae'Lor Of 4-h- machine. lp- ofie embodiment of my invention is .,app@lieci t,@) -, synelirodous generator I provide the -Tnachine -with a ivindin(,y on its ex40 citivi(,r mer-,iber cap@ble of alon(l, or.e ,ixis per pole. suppiy an excitinp- current to -@@his - win(:Iing siifficienf, -co prodiiee the necess,q-ry no-loacl magnetization and cause saicl ci-irrey-it -to v-,ry -with the rnc,,o-riitLide 4.5 ancl of compon-Int of th-arma@-i:@re reaction which is co,,ixiol wich the -winC@4ir.g o-.q. ".Iiexcitirg merD-bp-r. -,mbo,- Iini Ti, Of Lyi-,,, inventiod as al)-fliec'i t]@e sarie tvpe of machi-,ie I 5.0 provide exciting j-De-mber -Nvith ,in exciting ,ind vyitli a ne-Litr-:,Iizing -%vinding disp-l@eed by electric,,,,,l deurees fi@om t@be exeitiiig suppl-,7 to the exc;@.in(r vi-ndifig ,iii exciting current s-Lifficient -ar @o pro,@,u,@ce 11 ,v T-io-loacl. magnetization@ C',IUSE SI-lici Current 4-0 var Lh _7 Tv-i@th -' e mag-Tiic-ude and diree"uiop of that componeT,.'c. of the ariv-ature re,,iction 'Which is coaxial -with 'L-he exciting -vincl'jig aDd siil)piy to "i-ie I u neutraliziti(,y ivinding a curreilt v-,iryiiig -with 60 L @'n u 'he and direction o-,'-' ' a@- component o' 't'llie armature reiet-lioii which is L a-L angles to the excitinu @v-indiiig. !--a eitlier case i aenerate ,in ,tltern@t-in(y E. -i@/1. F. proportio@,,il to the load current an-d h--ving a fixed p'nise relition -io said curreia@L. 'L impress '-Ulllis E. F. on the al@Lernating curren'@ side oi a rotary converter which i-s Ciriven at ,t synchronolis spee d indep-,ndently of the c-Lir- 70 Pn-,l I so POrent E. iVI. F. impressed oi-L i sitio n briishes to co6l)erate with @'he. Clivect curr ent end of the machine as to ob'Llain dire ct current E. ill. F. ivhich varies -wit-h the sine of the pli,,ise an(,-le between the load- 15 curr etit a-iid the te@-minal E. @vi. F. of the - .ynchro-aous generator, or so as 'Lo obtain one direct current E. JV-. F. -wliich varies as s'@ited and another -@,vhich varies with tlie'cosi-iie of the pha-se angle between the 80 load current and the teri-ninal E. 11. F. This arran(I-ement is believed 'Llo be broadly nov el an-d is c,-,pable of applications othe'r th,,tn those specifically described in Vnis spec ification. 05 ILf v i--,ivention will be be'Lter understoocl bv reference to the accomptnying drawings, i @-v,liieh Fig-Lire I shows the inn,ention as apiT plied to a singxle-phase dynamo electric machin e the exciting member of ivhich carries 90 an excitini@F ivinding oiil y. Fig. 3 illustratec inoth er embodiment as applied to .i dynamo elect ric maebine -bh@ excitin- member of - which carries an exciting and a neiitralizing wind ing. Fi(r. 2 is an explanatory cil 95 aorarn. Re ferriii,,Lr'@o Fi(,. 1, tbe, nc,-Ioa(l excifation of the siii-le-I)base tv,-o-I)ole synchronous gen ei-@,Ltor there shown, is pro%-ided bv means of ,iii ordin,,Lry direct7current excifer, and this excitatio-ii is modifie(I in accord,,tnee ioo -witli the, magnit-Lide and the pha-,e of an E. M. F. varving in magnitii(le -with the load etirret-it incl retaitiing throu,-hoiit a fixecl phase relition with respect to said current. The synchronous altertiator carries a ivind- 105 iii- 9 dis-oosed on the, stator and connected tot@th'e inains 58, 59. The field structure 4 of this machine is keyect to the shaft 2 and is providecl with an exciting ivi@dino@ 5 cojino-et--d to the slip rinus 6, 7, usually' car-. iio
[2]1 354,901 ried by the shafi 2. Thes6 slips rinos are connected by means of stationar'v b@ushes with the brushe-s 24, 25 of the dir@ct current exciter, the a.rm,ature 8 of which is carried 6 by the shaft 2.: The field structure 9 of this exciter car-ries the windings 38, 39 and 40, tlle last of which is connected to the brushes 241 25 by way of the adjustable resistance 41. Keyed to -the same shaft 2 is the armaio ture of a two-pole'rotary converter. This armature is provided with a commuted winding 17 -",ith which co6perate two sets of brushes displaced by 90 electrical degrees. Th,e brushes 22, 23, forming one set, are 1.5 connected to the tinidirectional exciting winding 18 dis laced by 90 electrical degrees from the brush axis, and also to'the winidino, 38 on the field structure 9 of the iter. An adjustable resistance 62 is i exe n20 eluded in circuit with the winding 38. The briishes 34, 35, which form the other set, are connected in series with the windings 36 and 37 on the, converter an(I the winding 3,9 on the field structure 9 of tho exciter. 25 The windin- 36 is coaxial with the brush axis 34, 35. zn The windin(y 3@4' is displaced deg@ees -therefrom. . The by 90 electrical stator of the, converter also carries two displaced damping windings, 19 and 20. The 30 commuted winding 17 is connected at two di,,tnietrical points to the slip rings 15, 16. The armature 11 of a small auxiliary genera-tor is keyed to the s@aft 2 and cobpera'tes with the field structure 12, which carrie-s an 35 exciting winding 13 connected between one terminal of the synchronous a-Iterna-tor and the main 59. The-armature 11 is provi(led with a cominuted winding with which coopera,te the stationary brushes 26, 27 dis40 placed by 90 electiical degrees from the axis of theexciting'- windino, 13 and connected to the slip rings 15, 16 through the neutralizing winding 14 the axis of which coincides with the brush axis 26, 27 and which is de45 si,@iied to oppose the'an-nature reaction of the auxiliary generator. The operation of the embodirnent of the invedtion shown in Fig. 1, is somewhat as follows: As-sumin(r the cii-eiiit of, the wind50 in, 621 then upon th ing brought tip to e can be adjii means of the l@s stance 41. As Ion,, as the load current 55 ?, is zero, the excitation of the crenerator will onlv depend on the current i@ the exciting Wiliding 40 of the exciter.' As soon as the alternator is loaded, an E. M. F. e' will appe,ir at the terminals of the atixiliary gen60 erator 11 7 12. This E. M. F. will, tinder all eircumst,inces, be in phase with the load curreht. lvhen-thi-t load current is in phase with the terminal voltage e then e' will be in phase with e. When the phase of i dif65 fers from e, then the pbase e' will differ from e b the same amount. The conneey tions are such that this E. M. F. e' is impressed on the alt-ernate current side of the positively driven converter arniature 17. Under these conditions the magnitude of 70 the direct current voltage appearing at the briishes 22, 23, Gr at the brushes 34, 35 will entirely depend on the phase of e'. If the phase of this "load current E. M. F." is such that it reaches its maximum when the.points 75 at which the slip rings 15, 16 connected to the winding 17 coincide with t-he brushes 22, 23, then the direct current i,oltage at these brushes will be a maximun@ and the direct current voltage at the brtishes 34, 35 will be 80 zero. For a phase displacement of e' amountino, to 90 degrees, the condition will be relters@d, no direct current voltaoe appetring at the brushes 22, 23, and the maximiim direct current voltage, corresl)ondinz 85 to the value of e' appearing at the brush@s 34) 35. Now according to this invention I so connect the slip rings 15, 16 to the commuted winding 17, or when-the slip i-ings are already conneeted to 17,'I so mone the 90 bi-tish gear as a whole, preferably together with the st: ator as to reduce the direct current volta-ke -at the brushes 34, 35 to zero when the phase of e' coincides with the phase of e, in other words, when the genera- 95 tor operates on a unity power factor load. For a unity power factor load the ftill direct-current i7oltaoe cortesponding to the value of c' will then appear at the brush@s 22, 23. These brushes being conneeted to'100 th'e tinidirectional excitino, windino, 18 5 the latter will provide the unlpdirectionWI excitation necessary to reduce the altemating current taken by the converter at no-load to a small value. The direct current voltage ap- 105 p4aring at the brushes 22, 23 will, linder these eircumstaiiees, be strictly proportional to the "loa-d current E. M. F." and therefore also to the load current. This voltage may therefore be made use of to compound the 110 alternator. This is for instance, achieved by closing the circuit of the excitin-a winding 38 and suitably adjusting the rwistance 62. As soon as the, phase of the load current, and therefore the phase of e', changes, then 115 i direct ciirrent voltage -appears at the brushes 34, 35, and a, direct current is sent tlirough the windings 36, 37 of the convei-ter and the wii-iding 39 of, the exciter. The voltage at the briishes 34, 35 is al-w,,,tys 120 pro ortional to the sine of the phase anole p t,3 between the load current and the terminal @,oltage of the synchronous alternator. 117lien the current be@,pins to lag behind the terminal voltage, then the direction of the 125 E. Af. F. appe@trinor at the bru,-,hes 34, 35 is such as to cause the windin(r 39 to add to the ma-netization of the exciter. As soon is the load etirrent begins to lead the terminil E. M. F., the direction of the E. M. F. at 130
[3]tl-ie brushes 24, 35 chunges and produdes 9, dema.gnetizin(r effect on 'the.exciter. This action corresponds e--actly to the actual requireme--qts of the machine. Referriiig 'CIO Fig. 2 if OF represents-the direction of fhe unidirectional magnetization in the synchronous generator, then OA shows'the direc-' tion of the armature reaction for unity power factor load. It is seen that this re10 action caiinot have @any direct effect on the ma.o,nitude of OF. It can only distort said field and reduce@ its ma,(,,nitude by inereasing the reluctance of the ma(,,netic path. Should the power factor of the loid chan-ae, 15 caiising the current to lag behind the terminal voltage by on angle o', then the direction of the armature reaction will assume that of thp_ vecior OA'. The componeiit Oa' of this ,irmature reaction will now act 20 to direc:illy oppose the magnetization OF while the distorting influence of the artna,ture reaction -@vill be reduded from OA to a'A'. Simila.rly if the curr6nt ecmes to lead the terminal E. M. F.@ by an angle c", 25 then the armature reaction will assume the position indic,,tted by the ve@tor OA." and this armattfrd re,,iction w ill liave a component Oa' which will add to the maunetization OF. Both Oa' and Oa" are propor3o tional to the sine of the angle c by which the phase of the load etirrent di@ffers from tho phase of the terminal E. M. F., which shows that the ma,-nit-@de of the t. M. F., appearin,r a-t the brushes 34, 35 is dire@ctly 35 proportion@Ll to the vectors Oa' or Oa" of Fig. 2, and ch,,tn(,es its direction to,(rether with these vectors thus causing the'excita,tio@ of tl-ie, synchronous generator to vary strictly in accordance with the magnitude 40 "Inc,t the phase. of the load current. As Icng as the E. M. F. at the bruslies 34, 35 is zero, ihe windings @6, 37 of the converter are idle and the total unidirectional excitition of this machine is stipplied by the winding 45 18. When the phase, of e' is caused to differ f rom t-hat of e, then tlle magnitude of the direct current E. M. . F. at the brushes 22, 23 diminishes, and that at the brushes 34, 35 increases. In coiisequence, the unidiree50. tional magnetization produced by the v@,indin(, 18 decreases and that produced by the wi@diilg@ 36 ,tnd 37 increases. In this w!ay i-t i.-, possible to keep the total unidirectional ma(rnetization of the converter near-ly con55 staiit. This is particularly true in case the - winding 36 is omitted. The main object of this winding 36 is to influence the compounding of the synchronous alternator. It bas already been pointed out 60 that the voltage at the brushes 22, 23 diminishes as soon as the phase e' differs from that of e. This means that the comlyounding effect of 38, wl-iich depends on the voltage at these brushes, also diminishes. ob By so connectino, the winding 36 a-s to cause same to map@netize in the ,ame direction as the winding 18 when i lays behind e, the full compounding effect can be, upheld 'lor any laggin(y load, even though the m,aunetic densities ii@the field structure 9 o'L the ex- 70 citer are under these &,ime, coiidifions increased be@eause of the added magnetization of the windinu 39. In case the current letds the terrninal . M. F., the - winding 36 -will oppose @uhe ' m,ao-.-iiptization of the - windin(" 18 75 and reduce the magnetization produced@' by the wind 38 beyond the value to ivhich ln it would begreduced if the windiiig 36 were omitted. But, -with a leading current, the, densities in the iield structure 9 are much 80 reduced, so tli!a,t a sma-Iler current in the winding 38 will be sufreient to produce the same compounding as for unity power factor or for lagging loads. The essential features of the embodiment 85 of the invention shown in Fi(r. 1, ari@, first, the production and utilizati@n of a "load C'Urrent E. M. F." the phase of which bears a constant relation 'Lo the phase of the load current, and second, the use of a mechani- 90 cally-driven converter provided with a set of direct-current brushes and so connected to the load current E. M. F. that the difference oi potential! at the direct current brushes of the converter is zero irresl;wtiv'e 95 of the value of @the load current E. . F., as long as the load current is in phase -",itli the terminal E. M. F. This mechanical converter may also be provided il'ith two sets of direct-current brushes displaced by 100 90 electrical degrees, the connection between this converter and the load current E. M. F. being so made th,,it 'the direct-current volta-e appearing at one set of brushes v,,Lries wi:L,h the cosine of the phase an@,le c betiveen 105 the load current and the termin@al E. M. F., while the direct-current E. M. F. at the other set of brushes varies with the sine of said angle and is zero when the load current is in phase with the terminal E. M. F. 110 The arrangement shown in Fi(y. 1 so varies the exciting current of the synchronous 'machine there shoiin a to increase or decrease said current in accordance ivitli the miffnitude and direction of the coaxial ieaction 115 ma-lietization. Bu'L it does not take care of that component of the -,Irmature reaction which maanetizes along an Lxis displaced by 90 electrical degrees 'with respect to the exciting magnetization, with the result that 120 the total mac),netization of the machine varies -with the load. The arrangement shown in Fi(T. 3 is designed to neutralize the ivhole of the armature reaction and also indicates means for 125 compounding such a machine. The stator of the two-pole sin(yie-phase alternate current generator or motor carr@es a ivin(lin(y 3 the terminals of which are connected to the mains 58, 59. The field structure 4 is keyed 130
[4]to the shaft 2 and carries two wi-ndings 5 and 64 displaced by 90 electrical degrees and e,,ich connected to a pair of slip rings 6, 7 and 65, 66, usually carried by the shaft 2. The winding 5 is an excitinrffn, the winding 64 a neutrali.zin(y windin-. This same Ln zn shaft carries the armature 8 of a directcurrent exciter the field structure 9 of which is provided Nvith the windings 38, 39 and 40, zo the last of which is connected through the adjustable resistance 41 to the-brushes 24, 25 co6perating with the armature 8. Thle arinature of a rotary converter provided with the commuted winding 17 is keyed to 15 the shaft 2 and co6perates with the two sets of brushes 22, 23 and 34, 35 displaced by 90 electrical degrees from each other and each connected to an exciting winding located on the stationary member of the converter. 2o The brushes 22, 23 are connected to the winding 18, the brushes 34, 35 to the -winding 37. This stationary member also carries two displaced and short eircuited windings 19, 20. The brushes 34 35 are co . n25 nected to the winding 39 on the field strueture 9 of the exciter through the adjustable resistance 67. The brushes 22, 23 are connected to the neutralizin(y winding 64 on the revolving member of the synchronous Bo machine by way of the slip rings 65, 66 and tbrough the winding 38 located on the field structure of the exciter the ampere turns of which winding can be regulated by means of the adjustable resistance 68. Two dia35 metrically located points of the commuted. winding 17 of ihe converter are connected to the slip rings 15, 16, carried by the shaft 2. This shaft further carr.ies the armature of a Qmall generator whic.h is provided with 40 the commuted winding, 11 with which cooperate the stationary brushes 26, 27. The stator of this machine carries an exciting winding 13 connected betweeri one terminal of the synchronous machine and the main 45 59, and a lieutralizing winding 14 displaced from the exciting winding and coaxial with the brtish axis. The brushes 26, 27 are connected to,the slip rings 15, 16, in series with the neutralizing winding 14. The slip 50 rings 15i 16 ,tre so connected to the commuted winding 17 of the converter that, when -the latter is revolved in syrichronism witb the field member 4 of th'e synchronous machine and the F,. M. F. e' generated in 55 irmature 11 is of the same phase as the ter-minal E. -iq. F. e of the synchronous mtcliine, the direct c:urrent voltage d' appearing at the brushes 34, 35 of said converter, is zero while the. direct current voltage d" 60 appearin(y at the brushes 22, 23 is a maximum. ,nee the phase of the E. M. F. e' v-,tries with the phase of the load current i and coincides with that of e when i is in phase with e, then the direct-current F,.,. M. 65 F. d' will always be proportional to e' sine c and the direct-current P,. iVi. P. d'.' will always be proportional to e' cosine 0, where a is the phase anple. between e and the load current i or between e' and e. The mode of operation of the arrallge- 70 ment showu in Fig. 3, as a generator, is. somewhat as follows: The synchronous generator being brought @iti) to speed, the direct current exciter 8, 9 will excite itself and send @n exciting cur- 75 ren' into the winding 5 of the field member of the synchronous generator suffidient ko produce the no-load terminal E' M. F. As long as no load is taken from the generator, no E. M. F. -will be generated 'n the 80 armature 11 of the auxilia.ry machine and no E. M. F. will be impressed on the alternate current side of the converter. But, as soon as a load current i is taken from the synchronous generator, then e' will assume 85 -,t certain magnitude proportional to.i. , Assumino, that 4he windiiag 38 on the field structure 9 of the exciter is short eircuited and that the current take-ii fro,-n-the generator is in phasd with its @Lermirial voltaoe go e, then the direct current voltage d' of the converter. will be zero and its direct cur.rent voltage d" will be a maxinium and proportional to e', -wliich means that a certain,current proportional to e' will flow through the 95 neutralizing -winding 64 of the synchronous generator. This Nvi'nding is so proportioned that, -ander the conditions nam6d, the magnetization it produces I equals that of the armature reaction, which, for unity 100 power factor, will- appear along an axis displaced by 90 electrical degrees from the axis of the exciting winding 5 and therefore coinciding with the fixis of the neutralizing winding 64. Should 105 the phase of the load current now change and, for instance. come to lag bellind the terminal E. ill. F., then the axis of the armature reaction will imrnediately change its position with respect to the, axis of the 110 exciting winding 5. One cornpo'nent of this armature reaction pro-porti-onal to the sine of the phase anale between i and e will appear along t;he @xis of 5, and another component of this reaction proportional to the 115 cosine of t@is phase angle Nvill appetr along - the @xis of the neutralizing windino- 64. An exact@v corresponding chanae will tike plice in the converter. The n@---gnitude of e' always corresponds to the magnitude Of 120 the load current and therefore of the total armature reaction; but the magnitudes of d' and d" change with the phase angle between i and e. When that phase angle is zero and all of the armature reaction ap- 125 pe,,trs along the axis of the winding 64, then d" is at rk maximum ,tnd.d' is zero. When the phase aiagle between i and e changes and part of the armature reaction appears alono, the axis of the winding 6 while the re- 130
[5]the .tnvinde-r still acts alon, tl-ie o -,i-incl;lnu @34 thed- @th,-,- mao--qi@tude oi- (7,' inei,eases by an amoun'u ex,@)c-tly pro-o-ortional Lo ihe reaction appepring al.onu tWe axis of 5, aD-d d" deer,-,ases by ,i@n nip-ou.-It e,- iactly -")TOpor'L,ioiial to ',,he (lecreasp. of the 9 reaction i-ii @bhat axis. The -wi-nding 39 is so @onnecte(@ to -L'he b-Lushes 3J,, 35 9 and there-. iore to the direct-curreynl E. iYj,. F. d' as @"o ;@D-crease tne --xcitation o'L the exciter S' D icir lagFpg-@ii-iire clirrent and to decreoc-- it 'to.-o .eadi-ng curren-t, thus causing tiie eLl-iTeii-t 'n 6 to chapge inaccordaiice Nvi-th the mp(yp-i@lude a--,id direct--,on of -@'he reaction coi-n-poappearing in the,, axis. Shol-ild it be desii-ed to compound 'Lhe alternator, 'bhen ,@i@e 38 on the field structure of -tiie exci-@ler may b-- included iii eircuit w-ith the neutializi-!Ig v-,,indinw- 6,1 of the sy-vicb-roiious 2 f) P.--rid -the resistance 68 adjusted to Droduce the desired compounding -)t, sa-,,7, unil@y i)ower factor. As soon P-s @.he pqwer factor ch@,inges, this compounding wil.1 dimiiiish, and 'bhis diminuti-o-Li can be couii@terS5 balaiieed, Lt least for lagging loads, by pron,idi,ig the winding 38 with more turns than -would be needed in order to talie cara of.the armature rea-etion component which appears along the axis of the exciting wind'o 0 ing 5 of the synchrono-as aeneratuf. In.ste,ad oT- connecting tITe converter volta,ge d' -n excitina winding on the exciter 3, 9, ',,his volta@e @an be coiinected to an additional -winding located on the field structure 4 oi -@.@he synchronous openerator and co,,ixially disposed with the exciti--aol @n ,,iTindin(-, 5. Similarly, the cdnverter vo itoage --" 7- ieed noi@, be connected directly to the neutr,,Llizing ivinding 64, but may be '10 conne@ted -@@o the excitino,- -windino, o-c a ZD second e@@citer the armature of which should -Lhe-,i be connected to the neutralizing windin(-r 64:. '@f 'he con,,erter is connected dizectly to '-@e windings located on 'che field 45 strue-'ure 4, then its output must necessarily be much lo,-fger than i'L it is connected to the excitina v@ indinus located on the field s,cructures @f e.Kcite@s- 7,vhich supply current to the flel,,l structure 4. The mode of Op,5 0 eration is exactly the sa-ine in either'case. In one instance the converter acts on the field striieture of the synchronou8 gcnerator directly, in the other it does so indirectly through -L'he meclium Gf- one or more direct55 current aenerators. Havin@ iully describecl my invention, what I claim as new and desire to secure by
