US2037567A - Electron discharge device control system - Google Patents

Description

14,. 1935' c. EHRENSPERGER Er AL 2,037,567

LECTRON DISCHARGE DEVICE CONTROL SYSTEM Filed Jupe s, 1935 5 sheets-sheet 1A April 14, 1936. c. EHRENSPERGER ET AL 2,037,567

ELECTRON DISCHARGE DEVICE CONTROL SYSTEM Filed June 5, 1933 5 Sheets-Sheexl 2 pf 14,. 1936- c. EHRENSPERGER m AL 299379567 ELECTRON DISCHARGE DEVICE CONTROL SYSTEM Filed-June 5, '1953 5 sheets-sheet 3 Apri-l 14, 1936. c. EHRENsPl-:RGER Er AL, 2,037,567

ELECTRON DISCHARGE DEVICE CONTROL SYSTEM Filed June 5, 1935 5 Sheets-Sheet 4 VINI! A Hilllll llhlll April 14, 1936. c. EHRENsPERGi-:R Er A1.

ELECTRON DISCHARGE DEVICE CONTROL SYSTEM D Filed June 5, 1935 5 Sheets-Sheei' 5 Patented Apr.y 14, 1936 UNITED STATES PATENT oFFIcE Charles Ehrensperger,

Stefan Widmer, Arthur Gaudenzi, and Gustav Brunner, Baden, S

wit-

zerland, assignors to Aktiengesellschaft Brown Boveri & Cie, Baden,

Switzerland, a jointstock company of Switzerland application June 3, 193s, serial No. 674,168

. In Germany June 17, 1932 14 Claims. (Cl. 171-97) This invention relates to improvements in reversible electric current converting systems employing electron discharge devices and more particularly to means in connection with such Systems for controlling the sequential operation of two or more electrically distinct discharge devices forming portions of such systems.

In reversible electric current converting systems employing electron discharge devices, the

current is generally transmitted in one direction through one device and is transmitted in the reverse direction through another device. If one of vthe lines between which current is to be transmitted is a direct current line, the reversal of the flow of energy occurs infrequently at intervals determined by the variations of the voltages of the lines and by the action of any current regulating means provided therefor. If the two lines are alternating current lines, the ow of energy between the two lines occurs regularly during every cycle of the voltage of one of the lines if the current is transmitted at unity power factor,

= and reverses four times during every cycle if the current is transmitted at a leading or a lagging power factor. Such reversals make it necessary to control the two devices in such a manner that both devices be operable to carry current at every instant. In general, the voltage relations in the circuits of the two devices are not symmetrical ,at every instant with the result that circulating currents iiow in the circuits connecting the two devices, thereby producing losses in the circuit and lowering the power factor of the current drawn from the supply line. The iiow of such circulating currents may be avoided by controlling the devices in response to the ow of useful current therethrough in such a.'v manner that only the device carrying useful current is made operable by the action of the control means which is 40. such that any other devices are then inoperative to oder a conductive path to the flow of circulating currents. Such control is preferably obtained by means of auxiliary electron discharge devices controlled in response to the flow of use- 45 ful current.

It is therefore among the objects of the present invention to provide ymeans in a current converting system employing electron discharge devices'in distinct circuits by which only one of 50 such devices is operative at any instant.

Another object of the present invention is to provide means in a current converting system employing electron discharge devices in distinct circuits by which only the device which is to carry 55 useful current is operativeat any instant.

l Another object of the present invention is to provide means in a current converting system employing electron discharge devices in distinct circuits by which such devices are controlled in response to the ilow ofuseful current. 5 Another object of the present invention is to provide means in a current converting system employing electron discharge devices in distinct circuits by which the iiow of circulatingcurrent between the devices is prevented.

Another object of the present invention is to provide means in a current converting system employing electron discharge devices in distinct circuits permitting the passage of useful current alternately in each direction of now through the 15 system.

Another object of the present invention is to provide means in a current converting system employing electron discharge devices in distinct circuits permitting the flow of in-phase and of 20 reactive energy in either direction lof flow through the system.

Objects and advantages, other than those above set forth, will be apparent from the following description when read in connection with 25 the accompanying drawings, in which:

Figure l diagrammatically illustrates one embodiment of the present invention applied to the control of a reversible current rectifying-inverting system employing an electron discharge de- 30 vice for the rectifying operation and another such device for the inverting operation.

Figure 2 diagrammatically illustrates another embodiment of the present invention applied to the control of a reverse frequency converting 35 system employing two electron discharge devices in electrically distinct circuits in such manner that the devices are controlled in response to the flow of current through such circuits. 40

Figure 3 diagrammatically illustrates a modified embodiment of the present invention differving from the embodiment illustrated in Figure 2 in that the'cathodes `of the two devices are connected at a common point and in that the control 'electrodes of the two devices are energized by common means.

Figure 4 diagrammatically illustrates another modified embodiment. of the present invention differing from the embodiment illustrated in Figure 3 in that the control electrodes of the devices are energized with alternating current.

Figure 5 diagrammatically illustrates another modied embodiment ofthe present invention differing from the embodiment illustrated in invention diierlng from Figure 3 in that the discharge devices are trolled in response to the direction of the of energy current between the two lines.

Figure 6 diagrammatically illustrates a portion or another modified embodiment of the present the embodiment illustrated in Figure 5 in the means utilized for energizing the control electrodes of the discharge devices.

Referring more particularly to the drawings by characters oi reference, reference numeral il designates an alternating current line of any desired frequency and number of phases herein represented as a three-phase line only for the reason that such type of line is most frequently vutilized in practice. Line li is connected with lthe primary winding l2 of a transformer having two secondary windings i3 and d4 each comprising a plurality or phase portions connected to form neutral points for such windings. In the embodiment illustrated in Fig. l windings i3 and irl may deliver either identical or different voltages and the relative value oi such voltages may be adjusted by providing one of the windings such as winding i3 with suitable taps. The phase portions o2? winding i3 are severally connected with the plurality of anodes i6 of an electron discharge device ill having a cathode i8 connected with the positive conductor of a direct current line i9. Device l1 is provided with control electrodes 2i severally associated with each of the .anodes lli-and is also provided with the usual arc igniting and maintaining means known to the art and therefore not shown. The phase portions of winding M are similarly connected with the plurality of anodes 22 of an electron discharge device 23 having control electrodes 25 and having a cathode 24 connected with the negative conductor of line I 9. Cathode i3 is connected with the neutral point of winding I4 and cathode 2d is connected with the neutral point oi' winding i3. As a result of the above connections, device il may only be so controlled as to be operable as an alternating current rectier to 'transmit current from line II to line I9, whereas device 23 is operable as a direct current inverter to transmit energy from line I9 to line il.

The two circuits comprising devices I1 and 23 then present common connections'with line I9, but such circuits may be designated as being electricallydistinct for the reason that only one of such circuits carries current at any given instant.

Control electrodes 2| 'and 25 may be energized by any suitable well known means. In the present embodiment, control electrodes 2| are generally maintained at a negative potential with respect to cathode I8 by means of a battery 26 over resistances such as 21 and 30 and are sequentially charged at a positive potential with respect con- :dow

to cathode I8 by means of a battery 28 connected therewith over resistances such as 30 and the segments of a distributor 29 having a brush 3I. Brush 3| is driven at a speed such that all control electrodes 2| will be energized from the battery 28 once during every cycle of the voltage of line I l and is therefore preferably driven by'a synchronous motor 32 directly energized from line II.

In a similar manner to the control of e1ectrodes 2|, control electrodes 25 are generally maintained at a negative potential with respect to cathode 24 by means o f a battery 33 connected therewith over resistances such as 34 and 35 and are sequentially charged at a positive potential with respect to cathode 24 by means of a, battery 36 and of a distributor 31 having a brush 38 also driven by the motor 32. The times of energlzation of control electrodes 2| and 25 may be adjusted independently of each other by means of levers 39 and 4| which control the position of the several segments of distributors 29 and 31. Control electrodes 2| may alsov be continuously maintained at a negative potential with respect to cathode I8 by means or battery 42 over resistance such as 43 and an auxiliary electron discharge device 44 having an anode connected with the battery 42, a cathode connected with cathode I8 and a control electrode connected with the cathode of the device 44 overthe bias battery it and over a shunt lfill inserted in the connection between cathode I8 and the neutral point of winding i4. Device 44 is such and the voltage of battery 46 is so adjusted that, when no current flows through shunt lll, device 42 is not conductive whereas when a current of any appreciable magnitude flows through shunt 41, device 44 is made conductive by the action of the control electrode thereof and completes the circuit of battery 42. In a similar manner to that described immediately above, control electrodes 25 may be maintained at a negative potential with respect to cathode 24 by means or" a battery 48 and over resistances such as i9 and over another auxiliary discharge device iii having a control electrode connected with a bias battery 52 'and connected with a shunt 53 inserted in the conductor between cathode 24 and lthe neutral point of winding I3.

The operation of the system will be described assuming that the voltage of line EI is maintained at a constant value but will be understood that such operation will not be materially different if the voltage of line il is variable. Assuming the system to be connected as shown in Figure l and assuming that line Il is energized, control electrodes 2| and 25 are generally maintained at a negative potential with respect to the associated cathode by ,means of batteries 2S and 33 and are sequentially charged at a positive potential with respect to the associated cathode as a result of the movement of brushes 3| and form a direct current flowing from cathode I8 tol I9 is higher line I9. When the voltage of line than the predetermined value' considered above, it will be desired to convert direct current from line I9 to alternating current for line II over device 23 and lever 4I is accordingly adjusted in such a manner that each control electrode 25 is positively energized from battery 36 at a time when the associated anode 22 receives, from Winding I4, a negative .voltage smaller than the voltage ot line I9. As a result of such simultaneous adjustment of levers 39 and 4I, devices I1 and 23 permit windings I3 and I4 to impress a voltage on a circuit from the neutral point of winding I3, over winding I3, device I1, winding I4, device 23 back to the neutral point of winding I3, such voltage being the sum of the voltages of the portions o f windings I3 and I4 associated with anodes I 6 and 22 simultaneously operable to carry current.

, is therefore capable only of and when a half l and 5I. When device In general, the value of such voltage will cause the ow of a pulsating circulating current in the above described circuit in the absence of batteries 42 and 48 and of devices 44 I1 is carrying current, such currentflows over shunt 53, thereby bringing the potential impressed on the control electrode of device 5l to a value which makes such device conductive. The negative potential oi battery 48 is thereby applied 'to all control electrodes 25 thereby making all the associated anodes 22 in-= operative with the result that a circulating cur-1 rent cannot iiow over device 23. In a similar manner to that above described, when device 23 is carrying current, such current flowing over shunt 4l, device 4t is thereby made conductive and the negative voltage of battery lh is applied to all control electrodes 2i, thereby making de vice i'i inoperative to carry a circulating current. By means of the above connections each device carrying useful our rent and the device not carrying current ls made inoperative so that the circuit oiered to the flow of circulating currents is always interrupted and such current cannot be established.

In the embodiment illustrated in Figure 2, transformer i2, I3, I4 vand devices lli and 23 are operable to convert alternating current between line I I and a second alternating current line 5E. The connections between such lines are then the same as the connections between lines il and I@ in Figure 1, but the means for energizing the control electrodes of the devices must be modif: fied to permit the sequential new ci current through devices il and 23 during each cycle oi the voltage oi line 56. In the present embodi-= ment. control electrodes 2i are again generally maintained at a negative potential with to cathode I8 by means oi battery 26 and are sequentially and periodically brought to a positive potential with respect to cathode i8 by means of battery 28 connected over an auxiliary discharge device 45 and over a distributor itl hav=I ing two brushes 58 and 59. Device l5 is similar to devices 4B and 5l utilized in the embodiment of Figure l, but diiers therefrom in being con nected with shunt 4l over a transformer @Il hav= ing the secondary winding thereof connected in series with a bias battery All. Battery All is adjusted at such a value that when current is not flowing through shunt 4l, device 45 is conductive wave sinusoidal current ilows through shunt il the control electrode ci device 45 is brought to a potential such as to render such device non-conductive. Brush 53 ci dis= tributor 5l is driven by the armature El oi an electric motor having a neld winding B2, Armature BI is connected with line li and held 62 is connected with line 56 over a resistance 63 pro vided with a movable tap, such connection permitting an adjustment of the relative position oi the rotating ileld in winding 62 with respect to the voltage cycle of line 56. As a result of such connections, brush 58 is driven at a speed which may be expressed as a number oi revolutions per second which is equal to the frequency of the voltage of line II plus the frequency of the volt age ci line 54, such frequencies being expressed in cycles per second. Brush 59 is driven by the armature 64 o another electric motor having a ileld S6, armature 54 being connected with line iI and eld B6 being connected with line 5i over resistance 63 in such a manner that brush 58 is driven at a speed equal to the frequency of the voltage of line II minus the frequency of the brush 59 driven by motor armature respect voltage in line Il. Brushes I8 and Il may each engage with contacts of distributor 51 which are of such width as to give only a momentary energization ci each control electrode 2l upon engagement oi either of the tributor segment associated with such control electrodes. As a result of such connection, the output voltage o winding I3 over device I1 is a substantially sinusoidal voltage which is impressed online 54, and current may flow through device il over any portion of such voltage wave depending upon the direction of energy iiowbetween the two lines and upon the power factor oi the current transmitted.

Device 23 is controlled in a manner similar to the control of device il, control electrodes 25 belng generally maintained at a negative potential with respect to the potential of cathode 24 by means of battery 33 and being sequentially .and periodically made positive with respect to cathode it by means of battery 35 over discharge device 55 and distributor 6l. Device 55 is connected with shunt 53 by means of a transformer 55 and a bias battery' 50. Distributor 6l is provided with a brush 68 driven by motor armature BI and a 6L Winding Id thus delivers current over device-23 and the output voltage of device 23 is a substantially sinusoidal voltage similar to the voltage or winding i3 and device il, and is similarly impressed on line 5%. Due to the inverted connection of devices il and 23, such devices alternate in care rying current and thereby transmit positive and negative haii waves of current between lines il and Sii. en device Il is carrying current, such current iiows' over shunt 53, thereby bringing the control electrode of device 55 `to a voltage such that device 55 becomes non-conductive. with the result that control electrodes 25 cannot be ener gized from battery 36 and are tive with respect to cathode 2Q by battery 38. As in the embodiment illustrated in Figure l, the now of circulating current, which tends to estab-1 lish itself between the two devices' ill and 23, is thus prevented by the inoperativeness o' device 2S over the period considered. Durlngthe next haii cycle or" the voltage oi? line 5G, device 23 is carrying current, such current owing over shunt 4l with the result that device i5 is made nonconductive and control electrodes 2i are maintained negative with respect to. cathode i8 by battery During such period, device il is thus ino, rative and. prevents the liow oi a circulating current therethrough. The times at which devices il and 23 carry current are deu pendent upon the direction oi the flow oi energy between the two lines and upon the power factor ci" the current transmitted and, as devices l5 and 55 are controlled in response to the now of such current, such devices will always render either the device il or 23 inoperative dependent on which is not required to carry useful current; the now of circulating currents is thus prevented in the absence of current or in the presence of current at any power facto In the embodiment illustrated in Figure 3,

brushes with the dismaintained negacathodes I8 and 24 are connected at a common point and must therefore be connected with the a. positive potential with respect to the associated cathodes by means of battery 28 and distributor 51. Control electrodes 2| and 25 thus being energized by a common means, the positive energization thereof can no longer be controlled by means of devices 45 and 55 as in the embodiment illustrated in Figure 2. In the present embodiment, the control electrodes are maintained negative with respect to the associated cathodes by means of battery 56 and devices 44 and 5I in a. manner similar to that illustrated in the embodiment of Figure 1, devices 44 and 5I being however preferably connected with shunts 41 and 53 over transformers 10 and 1I When device I1 is carrying current, suchy current flows over shunt 53 with the result that device 5I is made conductiveand maintains control electrodes 25 negative with respect to cathode 24 with the result that device 23 is inoperative and cannot therefore carry any circulating current. During the next half cycle of the voltage of line 54, device 23 is carryinOr current, such current nowing through shunt dll with the result that device t4 is made conductive and control electrodes 2i are f mauitained negative with respect to the associated cathode l5 by means of battery 56 and device I 1 cannot carry any circulating current. The operation of the frequency converting system illustrated in the present embodiment is therefore 'entirely similar to that of the embodiment illustrated in Figure 2. It will be understood that, in the present and following embodiments, devices il and 23 may be replaced by a single device containing anodes i6 and 22, control electrodes 2l and 25, and having a cathode connected with winding 13 over shunts 41 and 53. Such device would however constitute. part of two electrically distinct circuits, as the two circuits including windings I 3 and I4 and having the cathode of the device in common do not carry current simultaneously at any instant.

In the embodiment illustrated in Figure 4:, the control electrodes of devices I1 and 23 receive the voltages, in series, of a battery 19 connected with cathodes IB and 24, of a transformer 18 energized from line 54, and of transformers 16 and 11 energized from line I I. As is well known, the output voltage of a system comprising such control electrode energizing means is again a substantially sinusoidal voltage, but the control electrode energizing means again controls the operation of the devices in such a manner as to prevent the iiow of circulating current therebetween. In the present embodiment, shunt 41 controls the operation of auxiliary devices 44 and 45 over a transformer 12, and shunt 43 similarly controls the operation of .auxiliary devices 5| and 55 over a transformer 15. Transformer 12 is the equivalent of transformers 60 and 1U in Figs. 2 and 3 and transformer 15 is the equivalent of transformers 65 and 'II in Figs. 2 and 3. Device 45 is conductive when no current flows through shunt 41 and completes the connection of control electrodes 2I to cause operation of device I1. Device 44 is then non-conductive and does not effect the operation of device I 1. When current is iiowing through shunt 41, device 45 becomes non-conductive and interrupts the connection of battery 19 with control electrodes 2| whereas device 44 becomes conductive and impresses on control electrodes 2I the negative voltage of a battery which is of suiiicien't magnitude to maintain` control electrodes 2| negative with respect to cathode I8 even when such control electrodes also receive voltages from transfarmers 16 and 18. In a similar manner, when no current is flowing through shunt 53, device 55 connects battery l19 with control electrodes 25 over transformers 18 and 11, and device 5I is non-conductive. When current is owing through shunt 53, device 55 becomes non-conductive and device 5I becomes conductive so that control electrodes 25 are energized at the voltage of battery 80 and of transformers 18 and 11, being thus maintained negative with respect to cathode 24. In the present embodiment as in the previously described embodiments, when device I1 is carrying current, device 23 is inopera tive; when device 23 is carrying current, device I1 is inoperative and circulating currents therefore cannot flow between the two devices.

In the embodiment illustrated in Fig. 5, the control of the control electrodes ZI and Z5 is common, such control electrodes being maintained negative with respect to cathodes it and i243 by means of battery 26 and being positively energized by means of battery EB over two distributors 81 and 88 having the brushes thereof driven at a suitable speed by means of a synchronous motor 89 connected with line EI. Distributors `81 and 88 are each provided with a numloer of segments depending upon the ratio of the frequencies of the voltages of lines Ii and 54, such segments being suitably connected with all of control electrodes 2| and 25. The control electrodes are energized by distributors 81 and 88 in such a manner as to permit the associated anodes to carry current in phase with the voltage of line 54, such current being carried alternately by devices I1 and 23 over successive half cycles I of the voltage of line 54, thus providing for the transmission of irl-phase energy from line II to line 54. Distributor 88 is provided with the same number of segments as distributor 81 but the connections between such segments and control electrodes 2! and 25 are such that the control electrodes permit devices l1 and 23 to carry current in phase opposition with the voltage of line 54 thus providing for the transmission of in-phase energy from line.54 towards line I I. The connection of battery 28 with the brush of distributor 81 is effected over auxiliary device 45 and the connection of such battery with the brush of distributor 88 is effected oyerdevice 55.

present embodiment, devices 45 and 55 are generally maintained conductive by the action of batteries SI and 92 connected between the cathode and the control electrode of each of said devices.

Wattmeter 8| is of the oscillating type and is provided with an oscillatory armature connected with shunts 41 and 53 over transformers 10 and 1I and provided with fixed field coils connected with winding 13 over a transformer 82.Y As a result of such connection the armature of wattmeter 8| oscillates in response to the ow of energy between lines I I and 54.

The direction of such flow of energy remains the same as long as the current transmitted between the two lines is in phase coincidence or in phase opposition with the voltagepf line 54 but the direction of such fiow reverses four times during every cycle of the voltage of line 54 when the current transmitted is leading or lagging because the ow of energy occurs in one direction during the intervals over which the current is in A phase with the voltage and occurs in the reverse nsl direction during the intervals over which the currentl is in phase opposition with respect to the voltage. During' the intervals over which the current is in phase with the voltage, wattrneter 8l reflects the beam of light received from source 83 on photo-electric tube 86, thereby making device 55 non-conductive and interrupting the connection between battery 28 and distributor 88. During such time battery 28 is connected with distributor 81 over device 45 which is conductive and the control electrodes o' devices i1 and 23 are controlled by means of distributor 8i. When the current is in phase opposition with the voltage Aof line 54 wattmeter 8i reiiects the beam of light from source 83 on photo-electric tube 84 thereby rendering device 45 non-conductive and interrupting the connection between device 8l and battery 28. During such interval, distributor 88 is connected with battery 28 over device and controls the control electrodes of devices il and 23. In the present embodiment, only one of the control electrodes oi devices l1 and 28 is energized at any instant over distributor 81 or distributor 88 so that only one of anodes i6 or 22 is operable to carry current at any instant. Such anode then carries the useful current transmitted between line Il and line 54, and as all the other anodes of devices l1 and 23 are then inoperative, no path is offeredto the flow oi circulating cure Arents between such devices.

In the embodiment partly illustrated in Fig. 6, devices 44 and 55 and Wattmeter 8i are replaced by discharge devices 94, 95, 98 and 8l each provided with an anode, a cathode and two control electrodes. One control electrode of each or" devices 94 to 91 is energized in response to the fioW of current between the two lines by means or shunts 41 and 53 and transformers l2 and le. The second control electrode or" each device is energized in response to the voltage of winding 13 by means of a transformer 9d. Devices @t to 91 are conductive when the control electrodes thereof are not energized from any oi transform- Aers 12, 15 and 88, and also when both control elecn trodes oi the device are positively energized from the associated transformers. When either control electrode oi any of'devices 84 to Sl is negatively energized from the associated transforin-E ers, the device is non-conductive. When the cur rent transmitted between the' two lines is in phase with the voltage of line 54 and the current and the voltage are both positive, both control elem trodes of device 94 are positive and such device connects battery 28 with the brush of distributor 81. At least one control electrode of each or" the other devices 95, 96 and B1 is then negative and such devices are then non-conductive. W hen the voltage and the current are both negative, both control electrodes of device 98 are positive and such device connects battery 28 with distributor 81. When the current and the voltage are in phase opposition, and the voltage is positive and the current is negative, battery 28 is connected with the brush of and during the intervals over which the current is positive and the voltage is negative, battery 28 is connected with distributor 88 over device 95. The connections between battery 28 and distributors 81, 88 are thereby effected at the same time as by the means illustrated in Fig. 5 and the operation of the system illustrated in Fig. 6 is thus identical with that of the system illustrated in Fig. 5.

` cathode,

distributor 88 over device 91,

Although but a few embodiments of the present invention have been illustrated and described, it will be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the spirit of the invention or from the scope of the appended claims.

It is claimed and desired Patent:

1. In a reversible electric current converting system, an electric current line, a second electric current line, a plurality of electrically distinct electron discharge devices eac having anodes with associated control electrodes and a means for connecting vsaid dischargev devices with each of said lines, a source of control potential, means for connecting said source with the control electrodes of one ci said devices, and means responsive to thejflow of current through another of said devices tointerrupt the connectionsmfoi the second said means with the said controii electrodes of the said one oi said devices. l

2. In a reversible electric current converting system, an electric current line, a second electric current line, a plurality of electrically distinct electron discharge devices each having anodes With associated control electrodes and a. cathode, means for connecting said discharge devices with each oi said lines, a source of control potential, means for connecting said source with the conr1 trol electrodes of one ci said devices, a source ci to secure by Letters i negative potential connected with the cathode ci said one of 'saiddevices and means responsive to the flow of current through another o said devices to connect said source oi negative potential in parallel with said'source oi controi pctential and with the second said means to pre-` vent flow or" current through said one oi said devices.

3. In a reversible electric current converting system, an electric current line, a second electric current line, a plurality oi electrically distinct electron discharge devices each having anodes with associated control electrodes and a cathode, means for connecting said discharge devices with each of said lines, a source of control potential, means for connecting said source with the con-1 trol electrodes of one oi said devices, a soince ci negative potential connected with the cathode oi the said one of said devices, and means responsive to the ilow of current through another oi said devices tc connect said source of negative potential in series with said source oi control potential and the second said means 'to'pe'v'eit flow of current through the said one oi said devices.

d. In a reversible electric current converting system, an electric current line, a second electric current line, a plurality of electrically distinct electron. discharge devices each having anodes with associated control electrodes and a cathode, means for connecting said discharge devices with each o said lines, a source of control potentials, means for connecting said source with the control electrodes of said devices, and means responsive to the momentary direction ci the new of energy between said lines for controlling the second said means.

5. In a reversible electric Ycurrent converting system, an electric current line, a second electric current line, a plurality of electrically distinct electron discharge devices each having anodes with associated control electrodes and a cathode, means for connecting said discharge devices with each of said lines, a source of control potentials,

y to prevent the iiow of I means for connecting said means for connecting said source with the control electrodes of said devices, and means responsive to the flow of current between said lines and responsive to the voltage of one of said lines for controlling the second said means.

6, In a reversible electric current converting system, an electric current line, a second electriccurrent line, electro discharge means comprising a plurality of electrically distinct circuits, discharge means with each of saidlines, means for controlling the operation of said dischargemeans, and means controlling the third said means to prevent the flow of circulating currents between said circuits.

7. In a reversible electric current converting system, an electric current line, a second electric current line, la plurality of electrically distinct electron discharge devices each having anodes with associated control electrodes and a cathode, means for connecting said discharge devices with each of said lines, means for energizing the control electrodes ci said devices, and means controlling the second said means to prevent the low ci circulating currents between said devices.

8. In a reversible electric current converting system, an electric current line, a second electric current line, a plurality of electrically distinct electron discharge devices each having anodes with associated control electrodes and a cathode,

means for connecting said discharge devices with.

each of said lines, means for energizing the control electrodes of said devices, and electron discharge means controlling the second saidimeans to prevent all but one of said devices from carrying current at any instant.

9. In areversible electric current converting system, an electric current line, a second electric current line, a plurality of electrically distinct electron discharge devices each having anodes with associated control electrodes and a cathode, means for connecting said discharge devices with each of said lines, means for energizing the control electrodes of saiddevices, and electron discharge means controlling the second said means circulating currents between said devices.

10. In a reversible electric current converting system, an electric current* supply circuit, an electric current load circuit, a plurality of electrically distinct electron discharge devices each comprising a. plurality of anodes with associated control electrodes and a cathode, means for connecting said devices with each of said circuits, a source of control potential, means for connecting said source withsaid control electrodes, and Wattmetric means responsive to the momentary direction ofthe flow of energy between said circuits for controlling the'second said means.

11. 'I'he combination with an electric current supply circuit, an electric current load circuit, and a pair of electrically distinct electron discharge devices each comprising a cathode and a plurality of anodes interconnecting said circuits and constituting spaced electrodes for the flow of energy therebetween, of means Vfor controlling said ow of energy comprising a plurality of control electrodes severally associated with Vsaid anodes, means comprising a source of current having connection with each of said control electrodes and continuously imparting thereto potential of such sign and magnitude as to prevent the initiation of said flow of energy by way of the associated anodes, means comprising a second source of current for imparting to said control electrodes potential of such sign and magnitude as to permit the initiation of said ilow of energy, means for sequentially connecting the said second source of current simultaneously with the control electrodes associated with the anodes o1' 5 each said device, and wattmetric means responsive to the flow of energy by way of an anode ol.' either one of said devices for preventing the flow of energy by way of the anodes of the other oi said devices.

12. In a system of the character described, electric current converting means comprising a plurality of anodes divided into groups, a plurality of control electrodes severally associated with said anodes, an alternating current input circuit connected with said means and supplying current thereto, an alternating current output circuit connected with said means and supplied with current therefrom by way of said anodes, means connected with each of said control electrodes and imparting thereto potential of such sign and magnitude as to prevent the initiation of said dow of current by way ol' said anodes, a source of control current, means comprising electron discharge means for sequentially connectingsaid source of 25 control current simultaneously with the control electrodes associated with each said group of anodes of such sign and magnitude and during such recurring moments as to permit the initiation oi' said ilow of current, and means operable responsive to the said ow of current by way of the anodes of any one of said groups thereof for controlling said electron discharge means in such sense as to prevent the connection of said source ci control potential with the control electrodes associated with any other group of said anodes.

13. The combination with an electric current supply circuit, an electric current load circuit, and means interconnecting said circuits comprising a pair of electron discharge devices each having a 40 cathode and a plurality of anodes constituting spaced electrodes for the flow of current between saidcircuits, of means forcontrolling the said flow of current comprising a plurality ci control electrodes severally associated wth said anodes, means 45 comprising a source of current connected with each o1' said control electrodes and continuously exciting the same in such sense as to prevent the initiation of said flow of current, means comprising a second source of current for sequentially 50 exciting the said control electrodes in such sense and during such recurring moments as to permit the initiation of said ilow of current, electric valve means controlling the operative connection of the said second source of current with said control 55 electrodes, and means operable responsive to the flow of current by way of the cathode and an anode of either one of said devices for controlling the said valve means in such sense as to prevent the connection of the said second source of cur- 60 rent with the control electrodes associated with the anodes of the other of said devices.

14. In combination, an electric current supply circuit, an electric current load circuit, electron discharge means interconnecting said circuits and \65 comprising a plurality of groups of anodes constituting electrodes for the flow of energy between said circuits, a plurality of control electrodes severally associated with saidanodes, means comprising a source of current connectediwith said 70 control electrodes and continuously exciting the same in such sense as to prevent the initiation of flow of current between said circuits kby way of said anodes, means comprising a second source of current for sequentially imparting potential 75 simultaneously to sa control electrodes associated with each said group of anodes of such sign and magnitude and during such recurring moments as to permit the initiation of said ow oi energy between said circuits by way o said. anodes, electric valve means controlling the third said means, and means operable responsive to said ow of energy by way of the anodes of either of said groups thereof for rendering neective the third said means with respect to the controi electrodes associated with any other of the said groups of anode CHARLES EHRENSPERGER. STEFAN WIDMER.

.ARTHUR GAUDENZL GUSTAV BRUNNER.

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