US2233416A - Inverter - Google Patents

Description

March 4, 1941. H. KLEMPERER INVERTER 3 Sheets-Sheet 1 Filed Jan. 9, 1940 A. C. OUTPUT 0 3 M a i m .8 HH\ 2 l 5 l W w B .0 9 2 INVENTOR.

' HANS KLEMPERER BY My? ATTY.

FIG. 2.

TIME

March 4, 1941. KLEMPERER I 2,233,416

INVERTER Filed Jan. 9, 1940 3 Sheet's-Sheet 2 OUTPUT 12W 3 To Pemomc lawn-me IMPULSES 1 FIG. 4-. Co ND ENSE R EC OUTPUT I E VOLTAGE HOLDING AR E CONDENSER h VOLTAGE CURRENT Ta lNVENTOR.

' HANs KLEMPERER March 4; 1941. H, K RE 2,233,416

INVERTER Filed Jan. 9, 1940 3 Sheets-Sheet 3 7 76 13 OSCI LA'TOR INVENTOR HANS KLEMPERER AT T Y.

Patented Mar. 4, 1941 UNITED STATES PATENT OFFICE INVERTER Application January 9, 1940, Serial No. 313,078

16 Claims.

This invention relates to inverters of the type in which direct current or low frequency alternating current is converted into alternating current of a relatively higher frequency by means of controlled gas or vapor-filled electrical dis charge tubes.

An object of this invention is to increase the eiiiciency and reliability of operation of such inverters.

Another object is to increase the permissible output frequency to such an extent that said frequency is greater than the rate at which the tubes can deionize.

Another object is to increase the power output obtainable with a given number of such discharge tubes.

A further object is to increase the deionization time available wherein each of such tubes may become completely deionized before a voltage tending to make them conductive is again applied thereto.

A further object is to decrease the rate at which the voltage on each of the discharge tubes increases at the end of the deionization time, thus eliminating any tendency for the tubes to fire prematurely.

A still further object is to fix the output frequency of the system by the circuit constants rather than by the rate at which the tubes are fired.

The foregoing and other objects of my invention will be best understood from the following description of exemplifications thereof, reference being had to the accompanying drawings,

wherein:

Fig. l is a diagram of one embodiment of my invention;

Fig. 2 contains a set of curves illustrating the mode of operation of the system as shown in Fig. 1;

Fig. 3 is a diagram of another embodiment of my invention;

Fig. 4 contains a set of curves illustrating the mode of operation of Fig. 3;

Fig. 5 is a diagram of a still further embodiment of my invention in which a plurality of condenser and discharge tubes are utilized; and

Fig. 6 contains curves pertaining to the operation of the arrangement as shown in Fig. 5.

In Fig. 1 direct current or relatively low frequency alternating current is adapted to be connected to input terminals l and 2. The system illustrated converts the input current to relatively higher frequency alternating current which is supplied to an alternating current output device primary winding H.

3. Since such a circuit usually contains both inductance and resistance, it maybe represented as in Fig. 1 diagrammatically by an inductance and a resistance. A condenser 4 is charged with current from the input terminals 1 and 2 through an impedance 5 which is preferably an inductance. The value of this impedance is so chosen. as to maintain the proper charging rate of the condenser 8. During actual operation of the device, the impedance 5 tends to keep the current flowing therethrough at a substantially constant value. The charge on the condenser is adapted to be discharged into the output device 3 through a controlled ignition discharge tube 6. This tube is preferably of the pool cathode type with an igniter for initiating a cathode spot on the pool in order to cause the tube to conduct current. Although any suitable type of igniter may be used, it preferably is of the type described and claimed in the copending application of Percy L. Spencer, Serial No. 303,963, filed November 13, 1939, for an improvement in Are igniting devices, consisting of a conductor separated and insulated from the cathode by a thin glass layer. The tube 6 is provided with an anode I connected to the positive side of the condenser 4 in the case where the input to the condenser is direct current. The tube 6 is likewise provided with. a cathode, 8, preferably of mercury, connected to one side of the output device 3. The other side of said output device is connected to the negative side of the condenser 4. The tube 5 is provided with an igniter 9, preferably of the type as described above. This igniter is adapted to be supplied with igniting impulses from the secondary winding it of an ignition transformer H having a This primary winding is supplied with periodic peaked voltage impulses from any suitable source for igniting the tube 6. For example, the source may consist of a series type inverter, such'as is illustrated in Fig. i. This inverter comprises two controlled ignition discharge tubes ii and M, and a pair of con densers l5 and It. Direct current to be inverted is supplied to terminals ii and it. The positive side of condenser i5 is connected directly to the positive terminal l1 while the negative side of the condenser I6 is connected directly to the terminal iii. The negative side of the condenser i5 is connected to the positive side ofthe condenser IS. The tube i3 is provided with an anode 19 connected to the positive terminal I! while the tube It is provided with a cathode 20 connected to the negative terminal l8. The cathode 20 is preferably of the permanentlyenergized type, as for example a thermionic filament. The tube II also is provided with a cathode 2!, preferably 01 the permanently-energized type, such as a thermionic filament which is connected to one side of the primary winding l2. The other side 01' said primary winding is con nected to the point between the condensers II and II through an adjustable energy-consuming resistance 2|. The tube It is provided with an anode 22 connected to one side of a primary winding 23 of a transformer 24. The other side of the primary winding 23 is likewise connected through said resistance 26 to the point between the condenser II and II. The transformer 24 is provided with a short-circuited secondary windin'g 2I. Although the voltage impulses supplied to the transformer 2C are not utilized in Fig. 1, they are available for ignition of another tube it more than one tube, such as I, is provided. The tubes I 3 and H, which are preferably of the gas or vapor-filled type, are provided with control electrodes, such as grids 21 and 23, respectively. These grids are normally biased so as to prevent the tubes l3 and H from firing by means of biasing batteries 23 and 30, respectively. Firing impulses are superimposed on these biasing potentials between the anodes and cathodes of tubes l3 and H from secondary windings 3| and 32 of a transformer 33 which is fed with alternating current oi a suitable frequency from any suitable source of alternating current, such as a vacuum tube oscillator 34. This vacuum tube oscillator may be of adjustable frequency. One side of the secondary winding II is connected through the battery 29 to the grid 21, while the other side of said secondary winding Ii is connected directly to the cathode. One side of the secondary winding 32 is connected through the battery 30 to the grid 28. The other side of said secondary winding 32 is connected directly to the cathode 20. Due to the firing impulses supplied from the oscillator 34, the grids 21 and 23 alternately render the tubes l3 and I4 conductive. As this action occurs, periodic peaked voltages of opposite polarity appear across the secondary winding Ill and 25. As indicated above, the voltages appearing across the secondary winding 25 are not utilized. The voltage impulses appearing across the winding I0 are impressed upon the igniter 3, and thus cause the tube I to be fired upon each such igniting impulse being supplied thereto. 1

An auxiliary rectifier tube 35 is connected directly across the tube 6. This rectifier tube is preferably of the permanently-energized cathode type, and therefore is provided with a cathode 35 which may be, for example, a thermionic filament. This cathode 36 is connected to the anode I. The tube II also has an anode 31 connected directly to the cathode I.

The operation of the system illustrated in Fig. 1 maybe more clearly understood by referring to the curves of Fig. 2. Along axis a Eo represents the voltage appearing across condenser I while I represents the current supplied from said condenser to the output device 3. On axis b, Er represents the voltage across the tubes 6 and 35. These curves do not purport to show quantita tively what happens in the system illustrated in Fig. i, but they do represent the operation qualitatively. The charging current supplied to the condenser I gradually raises its voltage Ec until it rises to a predetermined value at the time T1. Thereupon an igniting impulse is supplied to the igniter 9, causing the tube 6 to be come conductive. The condenser 4 then discharges through said tube I into the output device 3, delivering a pulse of current I which rises to a maximum, at which time the voltage Ec falls to zero. Due to the inductance of the output device 3, the current I continues to flow in the same direction but decreases in magnitude until it reaches zero at the time T2. During this period, the condenser I charges up in the opposite direction. At T: the voltage Ec built up across the condenser 4 tends to cause the current I to reverse. This reverse current cannot flow through the tube 3 inasmuch as it is arectifier. However, tube 35 which is connected in opposite polarity to that of tube I, provides a path ior this reverse current, and therefore a pulse 0! reverse current flows during the time between T2 and T3. During this period, the voltage Es again passes through zero, and rises to a positive value at the time T3. When the current I tends to reverse at the time T3, the tube I which was extinguished at the time T1 is no longer conductive, and therefore cannot further conduct any current. Also the polarity of the tube II is such as to oppose such flow. The value to which the voltage Ec rises at the time T: depends upon the degree to which energy has been absorbed during the time Ti-T: in the output device 3. The greater the degree of energy absorption, the lower will be this final value of EC. Actually it may be very much smaller than the initial value to which the condenser 4 was charged, and ordinarily is so low that it cannot cause the tube 6 to become conductive in absence of a positive firing impulse supplied to the igniter 9. Thus substantially all the energy which was not absorbed in the output device 3 during the period Ti-T: is restored to the condenser I in the proper polarity so as to again be available to be dissipated into the output device I upon the next ignition of the tube 6. Due to the conservation of this energy, the system operates very efliciently with a minimum of energy loss. Alter Ta, current from the input terminals I and 2 flows to the condenser I to again charge said condenser to the desired voltage. Therefore, during the period Ta-T4, the voltage Ec rises gradually to the full value when the igniter I again fires the tube 8, and the operation described is repeated.

Between T2 and T3 the voltage across the tube 6 is only the relatively small voltage drop across the tube 35, and furthermore is in the non-conducting direction on said tube I. Therefore, during the period T2-Ta, the tube I has no tendency to pass current and has an opportunity to deionlze. At the time T3, Er across the tube I again reverses, and is impressed upon the tube I in the conducting direction. However, as pointed out above, the value Er at the time T: is ordinarily insuiiiclent to cause any tendency for the tube I to fire. If at this time the tube I has not become completely deionized and any tendency to fire exists, no harm is done because the operation, as indicated by the dotted lines in Fig. 2, occurs. If reignition of the tube I occurs at the point T3, a succeeding pulse of current 11, as represented by the dotted lines, will be supplied to the output device 3. The voltage will follow the dotted curve Eel, and at the end of this second current alternation will rise to a smaller positive value than at the time Ts. This latter positive value of the voltage across the tube I being still less than the value occurring at T: has still less tendency to cause the tube I to fire. The voltage E61 will then rise along the dotted curve to a certain value at T4 when the igniter 9 retires the tube 8. It will be seen that reignition oi the tube '6 at T3 simply results in an added pulse of current being supplied to the load and the voltage on the condenser 4 on the nextflrlng being somewhat reduced. Also additional reignitions of the tube 6 following the time T: could occur without disadvantageous results. As for the tube 35, no problem or deionization time exists therein inasmuch as that tube is intended to fire each time its anode becomes positive.

From the analysis as given in Fig. 2, it will be seen that the frequency of the current supplied to the output device 3 is controlled by the circuit constants, including the value of the capacity 4 and of the inductance and resistance of the output device 3, and not by the frequency at which the tube 8 is fired. The frequency of the output current can be made considerably. greater.

than that determined by the time during which ance with the present invention no longer is limited by deioniaation time of the tubes which heretofore has constituted a serious limitation of the frequency which such inverters have been able to furnish.

The effect o f varying the frequency at which the tube 6 is fired is to vary the number of high frequency current pulsations supplied per unit of time. The greater the rate at which these pulsations are supplied, the greater will be the power supplied to the output device, and conversely.

Thus by varying the frequency of the oscillator 34, the power which is supplied to the. output device 3 can be varied.

As pointed out in connection with Fig. 1, each ignition of the tube may supply a train of current alternations to the output device. In some instances it may be desirable to devise a system in which the production of a train of current alternations is insured for each ignition of the tube. Such an arrangement is shown in Fig. 3. In this figure the same reference numerals are applied Where the elements are identical with those shown in Fig. l. The tube 6 in this modification is provided with an auxiliary holding anode 38, which is connected through a resistance 39 and a condenser id to the cathode ii. The condenser do is adapted to be charged to a predetermined potential from a suitable source of direct current, such as a battery ll, and a current-limiting resistance 32 which determines the proper charging rate for the condenser Mi.

The operation of the system shown in Fig. 3 will he better understood by a reference to Fig. i. In this figure, on axis a, EC again represents the voltage on condenser d, while I represents the current supplied to the output device 3. On axis b, Eh represents the voltage across the condenser 40. As in the caseorf Fig. 1, the charging current to the condenser 4 raises its voltage to a predetermined value, and at the time T1 the lgniter 9 is supplied with an igniting impulse which fires the tube 6. The voltage on the condenser 4 then causes adischarge current to pass through the tube 6 into the output device 3. At the time T1 likewise the voltage En has risen to a predetermined value, due to the charging current flowing to the condenser 40 from the battery 4|. When sequence of operations is repeated.

the tube 5 is ignited, a discharge current flows from the condenser 40 through the resistance 89 and anode 38 to an are spot established on the cathode 8. The'resistance 39' is of a value to give a relatively long time constant to the discharge circuit of condenser 40, so that the voltage Eh falls off, as shown between T1 and T2 in Fig. 4. Throughout this time a holding arc is maintained between the cathode 8 and the anode 38, so that a discharge may p ss to the anode 1 each time it becomes positive throughout this period. Therefore the current pulsations from the discharge circuit of condenser 4 which tend to fiow in one direction pass through the tube 6 from the anode I. The current which tends to flow in the opposite direction passes through the tube 35 from the anode 31. As a result, a train of current a1- ternations I of decreasing amplitude is supplied to the output device 3, and the voltage Ec across the condenser 4 likewise is alternated with decreasing amplitude. At T2 the voltage and consequently the current'fiowing from the anode 38 falls to such a value that it is incapable of maintaining an arc to the cathode 8, whereupon said are is extinguished. If atthis time current is still flowing from the anode I, such current will containue to flow until it has fallen substantially to zero, whereupon the tube 35 will cause an additional pulse of current to flow in the opposite direction, and then cease, as explained in connection with Figs. 1 and 2. The voltage EC on the condenser 4 at the time of the extinction of the tube 35 again has a positive value which represents any energy which has not been absorbed in the output circuit. However, due to the fact that the output circuit has been supplied with a train of current alternations, the energy absorption is considerable, and therefore the final value of E0 is very low, entirely eliminating any further tendency for the tube 6 to fire. Here again an additional ignition of the tube 6 does no harm, merely resulting in an additional alternation of current supplied to the output circuit. Voltage Ecagain rises to its maximum value, due to the charging current flowing thereto, and at the time T; the igniter 9 again ignites the tube 5 and the During the time Tz-Ta, the condenser 40 likewise recharges from the battery 43, and the voltage En rises, as indicated in Fig. 4, to its maximum value so as to be available for establishing a holding are as explained above.

In the case of Figs. 3 and 4, the frequency again is determined by the circuit constants rather than by the frequency at which the tube '6 is ignited. Here again the output frequency can be much greater than the speed with which the tube 6 can be deionized, so that the system can supply high frequency current with extreme reliability.

As mentioned in connection with Fig. 1, additional ignition tubes may be utilized for supplying current pulsations to the output. As a matter 'of fact, any number of such tubes together with associated condensers may be combined in a single system whereby the power output obtainable is multiplied. Such an arrangement is shown, for example, in Fig. 5. In this figure direct current or relatively low frequency alternating current is adapted to be connected to the input terminals 43 and 44 and alternating current supplied to an output device 45 similar to the output device 3 of Fig. 1. A plurality of 'condensers, for example three in number, 46, 61

(iii

between the input terminal 44 said condensers.

One side of each 0! said condensers, which may be the positive side in the case of a direct current supply, are connected to the input terminal 48. The condensers 48, 41 and 48 are adapted to bedischarged into the output device through controlled ignition discharge tubes 52, 53 and 54. These tubes are preferably of the same type as tube 6 described in connection with the previous figures. These tubes are provided with pool cathodes 55, 56 and 51 connected respectively to the negative sides of the condensers 46, 41 and 48. These controlled ignition tubes likewise are provided with anodes 58, 58 and 60, respectively, which are connected together through the output device 45 to the terminal 43. The tubes 52, 53 and 54 are likewise provided with igniters 6|, 82 and 63, respectively. These igniters are adapted to be supplied with igniting impulses from secondary windings 84, and 55 of ignition transformers 81, 88 and 69, respectively, whose primary windings 10, H and I2 are adapted to be supplied in sequence with igniting impulses from any suitable source. As illustrated in Fig. 5, these igniting impulses are supplied to said primary windings from a supply transformer 16 having secondary windings I3, 14 and I5 connected in star. The outer ends of said secondary windings are connected in series with the primary windings 18, II and 12 whose outer ends are grounded. Said supply transformer secondary is likewise provided with a grounded neutral [9. The transformer I5 is provided with a primary winding ll connected for example in delta and supplied with a three-phase voltage from a suitable three-phase oscillator 18. This oscillatoris preferably of the type which supplies peaked voltage waves to each of the three phases of the transformer. In this way the secondary windings 64, B5 and 56 are supplied in sequence with peaked igniting bu pulses which cause the tubes 52, 53 and 54 to be ignited in sequence. These tubes are ordinarily constituted so that a tendency for an arc spot to form. on their associated cathodes occurs only when the ignlter is made positive with respect to its associated cathode, and therefore these tu will ordinarily fire only on the positive voltage peaks supplied by the transformer 16,

In order to provide a path for the negative pulses of current which cannot flow through the tubes 52, 53 and 54, as explained in connection with the previous embodiments, an auxiliary dls charge tube Bil is provided. This tube contains a cathode of the permanently-energized type which may be, for example, a pool of mercury to which a holding arc is maintained by means of auxiliary holding anodes. Thus tube con tains such a pool cathode 8i and a pair of ou iliary holding anodes lit. These anodes are c nected to opposite sides of the secondary wind ing 83 of a holding transformer 84 whose primary winding 85 is adapted to be supplied from a sult able source of alternating current. The secoi ary winding 83 is provided with a center tap i. connected through an inductance B1 to the ode 8!. An are spot is established on the cathode Bl by any suitable igniting means which may be,

for example, an igniter of the type as indicated in connection with tubes 52, 53 and 54. Thereupon current flows alternately from the two anodes 82 to the are spot on the cathode. These currents overlap, due to the inductance 81, so that the cathode spot is permanently maintained. The constants of the transformer 84 and the associated circuit are so chosen that a reasonable value of current flows from the anodes 82.

The cathode 8| is connected directly to the common lead extending to the anodes of the tubes 52, 58 and 54. The tube 80 ls'likewise provided with three anodes 88, 88 and 80 connected respectively to the cathodes 55, 56 and 51.

When the system described above is energized, the condensers 48, 41 and 48 each acquire a charge from the input terminals 43 and 44. One of the tubes, for example 52, is ignited by an ignition impulse being supplied to the igniter Bl. Thereupon the condenser 46 discharges through said tube 52 into the output device 45. When the discharge current flowing from the condenser 48 tends to reverse, as explained in connection with the previous embodiments, such reverse current can flow from the anode 88 to its associated cathode 8|. Thus the operation of the condenser 42, the tube 52, and the anode 88 of tube B0 opcrates exactly as explained in connection with the operation of the single pair of tubes of Figs. 1 and 3. Following the sequence of operations established by igniting the tube 52, the tubes 53 and 54 are ignited in sequence. Each such ignition produces a similar sequence of operations, each resulting in furnishing the output device 45 with one or more alternations of high frequency current. As indicated in Fig. 6, the output current supplied by igniting the tubes 52, 53 1 and 54 are combined in the output device 45. Thus, for example, Ia represents the current supplied irom condenser 46 and tube 52; I1), the current from condenser '31 and tube 53; and I0, the current from condenser 48 and tube 5t. Each of these currents follow one another in sequence in the output device t5, and therefore although each oi? the tubes 5?, 53 and M fired at a certain frequency, the number oi current pulsa- 'tions supplied to the output device t? is the sum oi the current pulsations supplied from these tubes.

.-ls explained in connection with the previous dhnents, the irequency oi the output cur is det by the rate at which the tubes are o the which upplied to the out it s determined by the n mber oi current uipplied unit or me. liiy uti y of such tubes, as indicated in l -'.s..ter number or" such cur c t oulsu is unit oi? time can be supplied to output and therefore this embodiment presents system. course is to be understooril that this in to the particular do ry equivalents will so Milled in the art. In the where alteruatins c1. nt impressed upon input terminals, be understood tl'lat system .i one] oh the positive half of r..:ot cycle. o systems may hi both halves oi su 'esscd alterna current Wave. Also other s or tubes d control devices could be no. red. Various other modifications and ideas as to the utilization of the principles enunciated herein will suggest themselves to those skilled in the art. pended claims be given a broad interpretation commensurate with the scope of the invention within this art.

What is claimed is z 1. An inverter comprising condenser means,

d. Ii

"lined by the circuit constants rather It is accordingly desired that the apaugemetot for increasing the power output ignition rectifying space discharge means for 2,283,416 means for charging said condenser means, an

- lations in said discharge to a predetermined number, and means for initiating the'discharge operation of said space discharge means at a predetermined frequency.

2. An inverter comprising condenser means, means for charging said condenser means, an alternating current output circuit, space discharge means for discharging said condenser means into said output circuit by an oscillating discharge whose frequency is determined by the condenser means and its associated discharge circuit and for limiting the number of current oscillations in said discharge to a predetermined numher, and means for. initiating the discharge operation of said space discharge means at a predetermined frequency which'is less than said oscil lating frequency.

- 3. An inverter comprising condenser means, means for charging said condenser means, an alternating current output circuit, ionizable gas or vapor-filled space discharge means for discharging said condenser means into said output circuit by an oscillating discharge whose frequency is determined by the condenser means and its associated discharge circuit and for limit-' ing the number of current oscillations in said discharge to a predetermined number, said oscillating frequency being greater than that determined by the deionization time of said space discharge means, and means for initiating the discharge operation oi said space discharge means at a predetermined irequency which is less than said oscillating frequency.

4. An inverter comprising condenser means, means for charging said condenser means, an alternating current output circuit, controlled ignition rectifying space discharge means for discharging said condenser means into said output circuit by an oscillating discharge, rectifying means of opposite polarity to said space discharge means connected to provide a path for the negative part of said oscillating discharge, and means for igniting said space discharge means at a predetermined frequency.

5. An inverter comprising condenser means, means for charging said condenser means, an alternating current output circuit, controlled discharging said condensermeans into said output circuit by an oscillating discharge, rectifying means of opposite polarity to said space discharge means connected across said space discharge means, and means for igniting said space discharge means at a predetermined frequency.

6. An inverter comprising condenser means,

means for charging said condenser means, an

alternating current output circuit, pool cathode type rectifying space discharge means for discharging said condenser means into said output circuit by an oscillating discharge, rectifying means of opposite polarity to said space discharge means connected across said space discharge means, and means for initiating arc spots on said cathode at a predetermined frequency.

7. An inverter comprising condenser means, means for charging said condenser means, an alternating current output circuit, a discharge tube having a pool type arcing cathode and an anode connected in series with said condenser means and said output circuit, a rectifying tube having a permanently-energized type of cathode connected to said anode, and an anode connected to said pool type cathode, and means for initiating arc spots on said pool type cathode at a predetermined frequency.

8. An inverter comprising condenser means, means for charging said condenser means, an alternating current output circuit, space discharge means for discharging said condenser means into said output circuit by an oscillating discharge, said discharge means comprising a discharge tube having a pool type arcing cathode and an anode connected in series with said condenser means and said output circuit, rectifying means of opposite polarity to said space discharge means connected across said space discharge means, means for establishing a holding arc to said pool type cathode for a plurality of the periods of said oscillating discharge, and means for initiating arc spots on said pool type cathode at a predetermined frequency.

9. An inverter comprising condenser means, I

means for. charging said condenser means, an alternating current output circuit, controlled ignition rectifying space discharge means for discharging said condenser means into said output circuit by an oscillating discharge, rectifying means of opposite polarity to said space discharge means connected across said space discharge means, and means for igniting said space discharge means at a predetermined frequency and for maintaining said space discharge means ignited for a plurality of the periods of said oscillating discharge.

10. An inverter comprising a plurality of condenser, means, means for charging said condenser means, an alternating current output circuit, a

plurality of space discharge means for discharg.

ing said condenser means in sequence into said output circuit by an oscillating discharge whose frequency is determined by each condenser means and its associated discharge circuit and for limiting the number of current oscillations in said discharge to a predetermined number, and means for initiating the discharge operation of each of said space discharge means in sequence at a predetermined frequency.

11. An inverter comprising a plurality of con denser means, means for charging said condenser means, an alternating current output circuit, a plurality oi space discharge means for discharging said condenser means in sequence into said output circuit by an oscillating discharge, and means for initiating the discharge operation of each of said space discharge means in sequence at a predetermined frequency whichis less than said oscillating frequency.

12. An inverter comprising a plurality of com denser means, means for charging said condenser means, an alternating current output circuit, a plurality of ionizable gas or vapor-filled space discharge means for discharging said condenser means into said output circuit by an oscillating discharge whose frequency is determined by the condenser means. and its associated discharge circuit and for limiting the number of current oscillations in said discharge to a predetermined number, said oscillating frequency being greater than that determined by the deionization time of said space discharge means, and means for initiating the discharge operation of each of said space discharge means in sequence at a predetermined frequency which is less than said oscillating frequency.

13. An inverter comprising a plurality of condenser means, means for charging said condenser means, an alternating current output circuit, a plurality of controlled ignition rectifying space discharge means for discharging said condenser means into said output circuit by an oscillating discharge, rectifying means 01 opposite polarity to said space discharge means connected across each of said space discharge means, and means for igniting each of said space discharge means in sequence at a predetermined frequency.

14. An inverter comprising a plurality of condenser means, means for charging said condenser means, an alternating current output circuit, a plurality of pool cathode type rectifying space discharge means for discharging said condenser means into said output circuit by an oscillating discharge, rectifying means of opposite polarity to said space discharge means connected across each of said space discharge means, and means for initiating arc spots on each oi said pool type cathodes at a predetermined frequency.

15. An inverter comprising condenser means, means for charging said condenser means, an alternating current output circuit, a dischargetube having a cathode and an anode connected in series with said condenser means and said output circuit, a rectifying tube having a permanentlyenergized type of cathode connected to said anode, and an anode connected to said iirstnamed cathode, and means for firing said discharge tube at a predetermined frequency.

16. An inverter comprising a plurality of condenser means, means ior charging said condenser means, an alternating current output circuit, a plurality of discharge tubes each having a cathode an an anode connected in series with each of said condenser means and said output circuit, a rectifying tube having a permanently-energized type of cathode connected to all of said anodes, and a plurality of anodes connected to each of said first-named cathodes, and means for firing said discharge tubes in sequence at a predetermined frequency.

HANS KLEMPERER.

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