USRE16363E - Vacuum type invebteb convebteb - Google Patents

Description

June 15 1926.

1 w. cHuBB vAcUUu TYPE' INVERTED CONVERTER original Filed Nov. 29, 1915 4 sheets-Stien 1 v 7 AT'TORNEY June 15 1926.

L. W. CHUBB VACUUM TYPE INVERTED CONVERTER Qrginal Filed NOV. 29, 1915 4 Sheets-Sheet 2 2 fvlllllilldltlfitil!!! lllllllllllll 1 f 1 A a I l I I l l n.

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INVENTOR BYLew/'.5' W. Chubb.

ATrRNEY VACUUM TY PE INVERTED CONVERTER y Origal Filed Nov. 29,v 1915 4 Sheets-Sheet 4 1 A sneu o.onunu'o'o'auu'n 'l 1 58 6e y 6l 63 WITNEssEs; lNvENToRV /KJA M. Lewis wahl/bb.

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named .im 15, 1926. 16,363

UNITED sTArEsPAT-ENT oFFlclaz.v

LEWIS W. CHUBB, F SWISSVALE, PENNSYLVANIA, ASSIGNOR T0 WESTINGHOUSE ELECTRIC AND MANUFACTURING COMPANY, A ORPOBATION 0l' PENNSYLVANIA.

vacuum TYPE mvna'riin conv-narnia. y

.25 employing a plurality Original No. 1,347,894, dated July 27, 1920, Serial No. 64,154, med November 89 1915. Application lfor reissue filed June 11, 1921. Serial N0. 4?@,981 4 My invention relates to systems and apparatus for the conversion of direct currents into alternating. currents, and it has for its object to provlde devices of the character designated which shall be simple and inexf .nsive in manufacture and highly eEcctive 1n operation, being particularly adapted for the conversion of currents of high voltage.

' In the accompanying drawing, Fig. 1 is a l0 diagrammatic view of a system of the character described that is adapted to form alternating-current waves in the load circuit having a u are-top formation; Fig. 2 is a. diagram il ustrating the wave form produced in the system of Fig. 1; Fig. 3 is a diagram of .a system similar to that shown in ig. 1 wherein means are rovided for approximating a sine-wave orm in the load circuit and, furthermore, wherein means-are 90 provided vfor varying the degree of electrostatic control; Fig. 4 is a diagram illustrating the wave form produced in the system of Fig. 3; Fig. 5 is a diagrammatic view of a device similar to that shown in Fig. 3 but of cathodes of the incandescent type, with a thermal control of the electronic emission; Fig. 6 is a diagram, similar to Fig. 4, illustrating the wave form produced in the system of Fig. 5; Fig. 7 is a diagrammatic view' of a system cmbodyin a vacuum'converter of the ure electron- 1seharge type, together with a suppressor shield, for the electrostatic control .of the arc, having novel characteristics, and Fig. 8

isa view of the converter shown in Fig. 7 with the members thereof spaced apart to show the relative arrangement of the different component parts.

In the operation of systemsof' electrical o distribution, it is'frequently desirable to convert energy from the form of direct current into alternating current. In the past, this function vhas been performed either by inverted rotary converters or b the use of "5 vacuum apparatus which has n more or less unsatisfactory in operation. In the development of aV system of high-voltage, direct-current transmission, it is necessary tha apparatus be provided lfor the conversion of high-tension direct current into alternating current at the distributing end of the`line. inverted rotary converters are )unsuited for operation at high voltages on account of the. difficulties inherent to commutation and, so far 1s I know, no vacuum a paratus has as 1 yyet been developed which wi l operate at the voltages necessary for the economical operation of `a system of the character designated.

It is a Vwell known fact that'the arc`ows between the electrodes -in an evacuated contamer by virtue of a stream of electrons proeeding from 4'the cathode and impinging upon the anode or anodes. By placing a conducting shield in roximit to an arc path of the character esignate and by imparting a negative charge to said conducting member, I am enabled to. seriously retard or prevent the ow of an electron stream of the character specified. In like manner, by imparting a positive char to said conducting shield, the passage of e ectrons to an anode is facilitated.. It follows, therefore, that, by periodically imparting electrostatic charges of various characteristics to said conducting shields, I am enabled to control, in a large measure, the production of alternating current by a device of the character specified when supplied with direct current. It frequently becomesdesirable, or even' necessary, to aociate,with the alternating current consumption circuit, auxiliary apparatus having a definite frequency, suc 'or example, as an alternating-current generator or tuning apparatus, in order Vthat there may be a natural agency 'operating in the alternating-current circuit for determining the frequency thereof. By co-operation between this frequency-determining apparatus and the electrostatic control o sup ressor shields within the converter itself, am enabled -to produce an extremely efectivo control of the current ow.

I have found it convenient to apply, to ap aratus of the character designated, the tite of Vacuum type inverted converter, 05

vacuum converter or rectierin the same manner as has hitherto been employed in distinguishin between the ordinary rotary converter an the inverted rotary converter, although it will be understood that my apparatus produces as'direct a conversion of Energy as is produced in the ordinary rectier. l

I may employ vacuum apparatus of the mercury-vapor type, ,as commonly employed Y in the recti ation of alternatingcurrent or I may employ,l 4with even better results, a paratus of the incandescent cathode type disclosed, for-example, in U. S. Patent to. Fleming 803,684, or on page 193 of the 1906 edition of a work entitled Conduction of electricity through gases by J. J. Thomson. The type of apparatus disclosed in the last mentioned pu lcation produces exceptionally satisfactory results, as the pure electron emission employed readily subJects itself to electrostatic control and as the electrodes are not subject to deterioration because of positive ,ionic bombardment.

There is no :fundamental di'erence between the o ration 'of a device of the character descri d by Fleming and a pure electron dischar device of the character described by homson. In the Fleming vdevice, the action is analogous to that described on page 489 of the Thomson publication and may be termed a step-by-step action, in that an electron proceeding from the cathode collides with a gas particle and disru ts the same, forming a new positive ion an a new electron. The original electron may lose a large part of its energy and become inert but the newly formed electron proceeds toward the anode. This process may be repeated a reat number of times before an electron nally reaches the anode. The positive ions set free by the disruption of the gas particles are drawn to the cathode and b their bombardment thereof produce new e ectrons therefrom. There is thus established what may be termed a reciprocal action, electrons proceeding from the cathode continuously generating positive ions from the residual gas and said positive ions in turn mg new electrons from the cathode itself. As the vacuum is carried to a'higher and higher degree, the number of residual gas particles is reduced and the mean free ath of electrons proceeding from the catho e is increased. Av condition is soon reached wherein the voriginal electrons which started from the cathode impinge upon the anode itself, and the 'state-Lof pureV electron dis charge is ap roehed. By carrying the evacuations'til further, `the number of gas particles is so reduced that substantially no positive-ions arefgenerated .within the device, and current'fis carried 'entirely by electrous' proceedin directly from the-cathode to the anode. 's is the method ofoperaproduci -bular members tion which is resent in a deviceof the character describes on page 193 of the Thomson publication. One of the most striking advanta s of the latter form of ap aratus is e absence of positive ionic mbardment-of the cathode prevents the ,deterioraltion of the latter and, consequentl tends to produce` a device having long li e and extremely stable characteristics.

Referring to the accompanying drawing for a more detailed understanding of my invention, I show a container of the type commonly employed in metal-case mercury converters at 9\1'n Fig. 1. The container' 9 is provided with a pair of anodes 10 and 11 and with a cathode 12 of the va orizable reconstructing type. ,Any suitab e means may be employed for maintaining the cath'- ode 12in an active condition, such, for example, as a keep-alive circuit 13. The anodes 10 and 11 are each provided with sup ressor shields 14 of the character descri ed and lclaimed in a co ending application of S. W. Farnsworth, lerial No. 44,429, filed August 9, 1915, Patent #1,232,470 July 3, 1917', and assigned to the Westin ouse Electric & Manufacturing Company. rieliy described, the shields 14-14 comprise casings 'l5-15 surrounding the anodes and provided with transverse diaphragms 16-16 1n the lower portions thereof. The diaphra-gms 16-16 supportconducting tubular members 17-17 throu h which an arc from the cathode to the au'oe is forced to travel. The tubular members 17-17 are adapted to bev alternately connected and disconnected from their respective anodes by means of a contact Vmaking' device 18 which may be driven at any desired speed by a motor 19. The anodes 10 and 11 are connected respectively to the terminals of the primary winding 20 of a transformer 21, the secondar winding 22 of which is connected to an a ternating-current consumption circuit 23, preferably provided with tuning devices, such, for example, as a condenser 24 and a reactive coil 25. One terminal of a directcurrent supply circuit 26 is connected to the mid point of the primary winding 20, and the other terminal of said supply circuit is connected to the cathode 12 through the casing 9.

Having thus described the construction of a system embodying my invention, the operation is as' follows: assuming the directcurrent circuit 26 to be energized, with the contact-making device 18 in the ostion shown, a stream of electrons is at li rty to pass from the cathode 12 to the anode 11 the tubular members 17 ofthe associated shield 14 being maintained at positive polarit because of their connection to the an The formation of an are to said tuis prevented, however, by suitable' current-reducing means 27. Any

45, through rases attempt of an electron stream to pass to the f anode 10, however, results in the rapid acquisition of a negative tential by the tubular member 17 associated therewith, no I outlet being provided for removing such 'a charge. ,The negative charge immediately exerts a strong repulsivev action and prefvents the supply of electrons to the anode 10.

Under the conditions above set forth, di-

10 rect 'current Hows from the system 26 through theright-hand half of theprimary winding 20 and the anode 11vto the cathode 12, from whence it returns to the system 26. A current wave is thereby induced in the l! secondarywinding 22 to ow through the -sysm 2a. When the contact-making member of the device 18 is turned through 90, the above 4described conditions are reversed, the tubular membersl? associated with.the anode are connected thereto, thus permitting current flowtherefrom, and the tubular members 17, associated with the anode 11,

acquire a negative char e, preventing the flow of current from sai anode. There results a current wave in the left hand half of the primary winding and a resultant impulse in the circuit 23 in the reverse direction from the first mentioned impulse.v

When operating at a reasonably high voltage and with large amounts of mercury vapor within the apparatus, there is a strong tendency for an arc operating from an anode to persist after its shield is disconnected and a condition of short circuit is established atJ the immediately subsequent energization of the shield of the remaining an- It may, therefore, be necessary, under the conditions above set forth, to positively choke out the flow of current from an anode at the termination of the wave to be de-v rived therefrom-` and this may best be donc by producing an oscillating current flow said arc and causing said oscillating discharge to die down to a zero' value, as is disclosed and claimed in a copendin application of Chas. LeG. Fortescue, i erial o. 350,744, filed July 13, 1914, Patent #1,227,416, May 22, 1917, and assignedto the Westinghouse Electric & Manufacturing Company. v

Il ave found that, with an alternatingconsumption circuit having the orcharacteristics, it is diicult to operate a device of thecharacter specified inthe manner shown, especially at high operating voltages, but, by causing the consumption circuit 23 to `have natural periodic characteristics,such,for example, as are provided by the tuning operation of the devices 24 and 25 or by an auxiliary source-of alternating current connected thereto, I am enabled to Vobtain satisfactory operation. The action 06 of said auxiliary apparatus in providing current electrostatic control of 'periodic points of zero potential in they-circuit 23 is co-ordinated by driving the device 18 at the proper speed and phase relationso that the connections of the tubular member 17 are 'altered contemporaneously therewith. 'l0

The operation of my device may be likcned, therefore, somewhat to the operation of an ,asynchronous nerator in that it is necessary that the a ternatin'.current systemA supplied thereby should ave, in itself, means-v for maintaining a periodic electromotive force for the proper operation of thc apparatus supplying current thereto.

he operation of the system shown in Fig. 1 in the manner described. produces 80 square-top (potential waves in the clrcuit 23, as indicate by a line 28-28 in Fig. 2. The derivation of a plurality of disconnected and abruptly terminating impulses of f'ie character specified tends to set up surging and other undesirable phenomena 1n the circuit 26, especially when the latter is of con- -siderable length and of high voltage. This .harmful result may be prevented by providing polyphase, vacuum-type converter 90 apparatus, Iwherein the net derivation of energy from the direct-current supply circuit is uniform, or, if it be desired to employ singlehase apparatus, I may associate surgeamping apparatus with the system 26, such, for example, as the shuntin condensive devices 29 and the ser-ies in uctye devices 2929.

Referring now to the form of my invention shown in Fig. 3, I provide means whereby the current wave supplied to the consumption circuit 23 is caused to approxi'- kmate more closely to a sine Wave, thus'disturbing the direct-current supply circuit to a lesser degree andv providing alternating current which permits more efficient operation of electromagnetic alternating-current apparatus. A container 30 is provided with four anodes 31, 32, 33 and 34 associated, respectively, with tubular suppressing members 35k-35, 36-36, 37--37 and `3838. A contact-making device 18 is provided for riodically connecting the anodes 31 to 34, inclusive, with their suppressor shields and comprises four equally spaced main conducting segments 39-39,`each of which is associated with a pair of short conducting segments 40-40, one of which lieson each side thereof. The pairs of short conducting segments are connected together for thc/120 the anodes 31 and 34, whereas the main segments 39--39 arc employed for the electrostatic control of the suppressing devices associated with' the anodes 32 and 33.

Not only may I connect the anodes 31 to 34, inclusive, to their suppressor shields through the instrun'lentalt-y of the device 18, but I may connect all the suppressor shields to the cathode 12 through a. switch 41 in 130 order to more readily impart a ne tive charge thereto in the manner set fo and claimed in a -copending ap licatlon of'Chas. LeG. Fortescue, Serial o. 44,428 filed Au 9, l1915, Patent #1,231,587, .iuly s, 191 and assigned to the Westinghouse Electric da Manufacturing Company.

In order that the alternating-current wave induced in the consumption circuit 23 may have a low value, as desired in the incipient st in the production of a sine wave, it isaeesirable that the primary windin 20 include a large number of turns, so t at the ratio of transformation of the transformer 21 will be low in value and produce the desired low voltage from the circuit 26. If operating under ideal conditions, the number of active' turns in the primal member 20 should then be ra idly reduce until the maximum desired vo tage is obtained in the secondary circuit 23, whereupon the operation should be reversed and the number of turns in the prim vwindin 20 should be increased, app ing infinit as a limit. In actual apparatus 1t is di cult to obtain even an ap roxima-tion to the above described metho of operation because of the expense incident to providing the large amount ofnecessary ya.ppa,ratus,.`l may obtain a crude `ap roximation'with the paratus shown in ig. 3 by connecting 31 and- 34 to the terminals of a pri winding 20 having a large number of turns and by connecting the anodes 32 and 33 to intermediate symmetrically disposed points in said winding.

The operation, in a s stem of the character described, is as fo lows:I assuming the conducting arm in the device 18 to turn in a'clockwise direction, a pair of short-contact makingsegments 40-40 are first connected together, closing the circuit between the anode 31 and the associated suppressing tubular member 35, and rmitting current flow from said anode. K; impulse of direct current from the circuit 26 flows through the entire left-hand half of the primary windin 20 and-produces a relatively low volta 1n the circuit 23, shown, for example, y a step 42-42 in Fig. 4. Contact is next made between a pair of long contact-making segments 394-39, charging the tubular members 36 associated with the anode 32 permitting current flow therefrom and extinguishing the arc flowing from the anode 31, in the manner described and claimed in U. S. patent to Percy H. Thomas, No. 945,006. The current im ulse traverses only a small portion of the eft-hand half of the rimary winding 20 and the resultant hig effective ratio of transformation produces a high voltage in the secondar cuit 23, as shown by a line 43-43 in Fl, Contact is next made between another of segments 40-40, and the tubular cir- 'g. 4. pair suP' e anodes pressor members 35-35 an' again placed in connection with their associated anode 31, producing another low-voltage step in the wave of the circuit 23, shown by a line 45-45. The arc does no't readily transfer from the anode 32 to the anode 31, in accordance with the disclosure in the above patent preferring the better current path offered in the circuit of the anode 32, and it is therefore desirable to oscillate the current to a zero value by the use 'of an auxiliary condenser or monocyclic square, as disclosed in the above-mentioned application of Chas. LeG. Fortescue. Said current controlling apparatus forms no part ofthe present invention and is omitted from the drawings for the sake of clearne. In alike manner, the' arc must be forcibly extinguished at the anode 31 at the end of the active period.

The same cycle of o eration is now followed in connection wit the anodes 33 `and 34 and the right hand half of the primary windin 20, thus producing the negative half ofg an alternating-current cycle 1n the circuit 23 as shown at 45 in Fig. 4.

It is seen that, by increasing the number of a'nodes in the container 30 and so connecting said anodesas to increase the number of steps in the resultant current wave in the circuit 23, I may approximate a sine wave 46-46 as closely as is warranted by the economic factors associated with the design in question.

A`s above pointed out, the closure of the switch 41 permits a much more ra id and complete negative electrification of t e tubular suppressor members than would be possible were dependence placed solely upon their acquisition of a n tive charge from the impact of a stream o electrons. I may, if desired, o a step further and so delicately adjust te size and relation of the suppressor members as to permit current flow to an anode when its associated suppressor members are free and disconnected, and to choke or suppress current flow when said suppreor members are placed in connection with the cathode. Under such circumstances, the contact-making device 18 would be inserted between the respective suppressor members and the cathode. A device of the character specified would operate with less loss than would the system shown in Fig. 3, because there would be little or no energy loes such as is sEresent in current liow from the suppressor ield through a. resistance member to an anode, there bein solely an electrostatic charging and disc larging of the suppressormembers.

Referring now to the form of my invention shown in Fig. 5 wherein I avail myself of the phenomenon that an electrode, when highly heated, tends to emit an excess of electrons, IA provide a highly evacuated container-47 with four cathodes 48, 49, 50 and 51 ofthelamentary I and with an anode J 52. A' contact-making evice l18 is provided,

similar to that employed in Fig. 8, and is connected to send impulses of heating current from a direct-current source 53 to the cathodes 48 to 51, inclusive, inA succession.

The cathodes 48 to 51, inclusive, are con-U -nected to the primary` winding of the transformer 21 in the same manner as are the anodes 31-34 in Fig. 3. The entire device 47 is highly exhausted and 'thoroughly treated out as described in the Thompson publication above referred to, so that when one of the cathodes thereof is highly hea there results a pure electron emission anda resultant flow of current from the, anode to the cathode, u n the application of proper electromotive orce.

Assuming member of 'the contact makin the device 18 to rotate in a ockwise direction as indicated, a circuit is first closed through the cathode 51, heating the latter to incandescence and permitting current flow from a direct current supply circuit 26 to the anode 52, thence to the cathode 51 and, via theentire left hand half of the primary winding 2'0, to the source 26. There results an induced voltage in the circuit 23 indicated by a step 54-54 in Fig. 6. Heating cunentis next supplied to the cathode 50 and then reapplied to the cathode 51, roducing the steps 55--55 and 56-56 1 in ig. 6 in the same manner as explained ly large at length in connection with Figs. 3 and 4. In like manner, the energization of the cathodes 48 and 49 then produces the negative hal1f157-,57 ofthe alternating-current wave in ig. 6. Y r

`When employing apparatus of the character described, it is not necessary to oscillate the current to a zero value by the use of auxiliary apparatus when it is desired to ex Y tinIguish the arc to an electrode.

Y have found that, owing to the considerable mass of the cathodes 48 to 51, inclusive, it is diiiicult to heat and cool the same with suilicient rapidity to reduce alternating current of commercial ucncies in thecircuit 23. Ima however, resort to the use of suppressor 'elds in a pure electron-discharge device, as shown in Figs.7 and 8. An evacuated container 58 is provided with a relativefilmen cathode andwith four anodes60, 61,'62 and 63v arranged adjacent thereto. The cathode 59 is maintaned'in an electron-emitting condition by any suitable means, such, for example, as a source of heating current 64. Suppressor shields 65, 66, 67 and 68, formed preferably of closely interwoven or intermeshed masses of refractor wire, such, for example, as tungsten or mo ybdenum, are associated respectively with the anodes to 63, inclusive, and interposed between said anodes and the cathode 59. A contact making 'device 18 is employed to successively make contact between each anode.v 4

and its attendant suppressor shield in the same manner as set forth in connection with Fig. 3. The negative electron emission from the, cathode 59 is therefore directed to each 'of the anodes in succession 'in such uence as to produce the desired waveshape inthe circuit 23. p l a It will be understood that, in all cases, I maintain such 'inter-relation between the natural. frequenc of the circuit 23 and the` velocity of the evice 18 as to cause these two features to co-ordinate in the release and SuPPreion of ener iow from the direct-current supply circuit, so as to produce the desired operation.

Thron hout this description', I have explained t e action of my device in accordance with the theory which seemsmos't lausible in view of the present knowledge o the underlying phenomena. I desire it to be distinctly understood, however, that I do not conne myself to said theory` of operation but merely present the saine to aid in an understanding of the case.

While I have shown my invention in its preferred form, it will be obvious to those skilled in the art that it -is susceptible of various minor changes and modifications without departing from the s irit thereof, and I desire, therefore, that-on y such limitations shall be placed thereupon as are imposed by the -prior art or are the appended claims.

I claim as my invention: I

1. The combination with a direct-current supply circuit, of an alternating-current consumption circuit, a vacuum-type inverted converter interlinking said two circuits, and means'L associated with said converter for approximating a sine wave in the alternating current produced thereby.

2. The combination with a direct-current supply circuit, of an alternating-current consumption circuit, a vacuum-type inverted converter interlinkin .said two circuits, and means associated with said converter for producing a plurality of steps in the I.wave

orm of the alternating current' produced thereby, whereby a sine wave may be approximated. v v

3. The combination with-a direct-current supply circuit, of an alternating-current consumption circuit, a vacuum-'type invertved converter interlinking said two circuits, means for vtunin said alternating-current circuit to the desired frequency, and means associated with the converter for responding to said uency and for exerting'a resultant contro ing action on the operation of 'theconverter,

4. The combination with a direct-current supply circuit, of an alternating-current consumglilon circuit, an inverted converter interlin g Said two circuits, and voltagespecifically set forth in adjusti -and-switching mechanisms dy- 5. The combination with a direct-current mil supply circuit, of an alternating-current` consumption circuit, an inverted converter and ad ustable-ratio transformer interlinking two circuits, and .switchin mechanism for va ing the ratio of said transformer, wherlelay theV voltage supplied to said consumption circuit may be .periodically varied and an approximate sine wave of electromotive force impressed thereupon.

6. The combination with a direct-current supply stem, of an alternating-current consumption circuit, a transformer having its secondarywindin connected to said consumption circuit an having a plurality of voltage taps on its primary winding, aY vacuum-type inverted converter comprisa plurality of electrodes of one nominal puarity, at least one electrode of the opposite nominal polarit and electron-controlling means interpose between the respective electrodes for controlling current 'low therebetween, a connection from each of said first named electrodes to one of said primary-voltage taps, respectivelyz and' switching mechanism arrangled to periodically and alternately energize t e electron-controlhng means associated with relatively widely separated taps and relatively closely connected taps, whereby the electro-motive force supplied to said consumption circuit be caused to approximate a sine wave. The combination with a direct-current supply circuit, y of an alternating-current consumption circuit, a mercury-arc inverted converter interlinking said two circuits, said converter embod in means for, ra idly changing its con uctivity from a con ition of low impedance to a condition-of high impedance, and vice versa, wherebysaid periods of changin y rief part of a cyc e, and tuned reactance means associated with said consumption circuit. l

8. The combination with a direct-current supply circuit, of an alternating-current consumption circuit, a mercury-arc inverted converter interlinking said two circuits, saidi converter embodying means whereby the voltage of said converter suddenly rises to liigh values, remains at such valuesfor an interval of time, and suddenly dro to low values, and a tuned circuit coupl to said consumption circuit, whereb said tuned circuit carries substantially sinusoidal currents.

9. The combination with a direct-current conductivity occupy a c supply circuit, of an alternating-current consumption circuit, a vacuum-t inverted converter interlinking said two circuits-and embodying an evacuated container provided with a pair of electrodes and with a conducting shield ad'acent the intervening current p ath, means or developing an auxiliary periodic electromotive force in said alternatingcurrent circuit, connectin means associated with said consumption circuit for controlling the potential of said shield and means for varying the connections of said connecting means.

' 10. The combination .with a direct-current supply circuit, of an alternating-current consumption circuit, a vacuum-ty inverted converter interlinking said two circuits and embodying an evacuated `container rovided with a pair -of electrodes and wit ducting shield adjacent the intervening current path tuned reactance means associated with sai consum tion circuit, connecting means associated with said consum tion circuit for controlling the potentia of said shield and means for varying the connections of said eonnectin means w nating current owing through said converter. may be controlled.

11. The combination with a direct-current supply circuit, of an alternating-current consumption circuit, a vacuum-type inverted converter interlinking said two circuits and including two electron fpaths and an anode and a shield for each o said electron paths, said alternating-current consumption circuit including an inductance coil having its terminals connected to said anodes, one of the a conereby the alterterminals of lsaid direct-current circuit being connected to an intermediate point of said coil, the other terminal being connected to the cathode Iterminals of said electron paths, means for developing an auxiliary periodic electromotive force in said-alternating-current circuit, connecting means associated with said consumption circuit for controlling ,the potentials of said shields and means forvarying the connections of said connecting means.

12. The combination with a direct-current supply circuit, of an alternating-current consumption circuit a vacuum-type inverted converter interlinking said two circuits and including two electron paths andan anode and a shield for each of said electron paths,

lll

said alternating-current consumption circuit/1l including an inductance coil'having its terminals connected to said anodes, one of the terminals of said direct-current circuit being connected to an intermediate point of said coil, the other terminal being connected to the cathode terminals of said electron paths, a tuned circuit coupled to said coil, connecting means associated with said consumption circuit for controlling the potentials of said shields and means for varying v maas the connections of said connecting means whereby the alternating currents flowing through said converter may be controlled.

13. The combination with a direct-current supply circuit, of an alternating-current consumption circuit, a vacuum-type inverted converter interlinking said two clrcuits and including a plurality of electron paths and a shield for each of said electron paths, tunedreactance means associated with said consumption circuit, connecting means associated with said consumption circuit for controlllng the potentials of said shields and meansl for varying the connections of said connecting means whereby the alternating 15 currents flowing through said converter maIy be controlled.

n testimony whereof, I have hereunto subscribed my name this 8th day' of June, 1921.

LEWIS W. CHUBB.

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