US2028706A - Electron discharge device control system - Google Patents

Description

Jan. 21, 1936. E E N 2,028,706

ELECTRON DISCHARGE DEVICE CONTROL SYSTEM Filed Dec. 14, 1935 2 Sheets-Sheet l Jan. 21, 1936. E. KERN ELECTRON DISCHARGE DEVICE CONTROL SYSTEM Filed Dec. 14, 1933 2 Sheets-Sheet 2 Patented Jan. 21, 1936 UNITED STATES ELECTRON DISCHARGE DEVICE CONTROL SYSTEM Erwin Kern, Ennetbaden, Switzerland, assignor to Aktiengesellschaft Brown Boveri & Cie., Baden, Switzerland, a joint-stock company of Switzerland Application December 14, 1933, Serial No. 702,324 In Germany December 24, 1932 22 Claims.

This invention relates in general to improvements in control systems and more particularly to means for controlling the power factor of the current in alternating current circuits including electron discharge devices.

In systems employing electron discharge devices such as alternating current rectifying systems, direct current inverting systems, motor control systems, etc., at least a part of the circuits of the system receive alternating current very low values when the flow of current through the discharge device is regulated by discharge l5 controlling means. It is generally desirable, to raise the power factor of the current to values 20 to cause flow of leading current through transmission circuits for improving the voltage regulation thereof. Such results are preferably obtained by means of electron discharge means provided with two groups of anodes through 25 which the flow of current is regulated by discharge controlling means in a manner such that the flow of current through the circuits associated with one group of anodes occurs at a lagging power factor and the flow of current occurring through the circuits associated with the other group of anodes occurs at a leading power factor. If the discharge device is of the vacuum type, the flow of current may be controlled by the usual type or" control electrode or grid. If the device is however of the vapor type, the flow of current can only be controlled by particular types or" control electrodes operable to interrupt the flow of current through the associated main electrodes. The control means should preferably cooperate with any means utilized for regulating the operation of the system and with any means utilized for protecting the system upon occurrence of disturbances therein.

It is therefore among the objects of the present invention to provide an improved control system for an electron discharge device whereby the power factor of the current flowing through the alternating current circuits of the system may be controlled at any desired value.

Another object of the present invention is to provide an improved control system for an electron discharge device whereby the current flow in the alternating current circuit of the system may be maintained unity power factor.

Another object of the present invention is to provide an improved control system for an electron discharge device whereby currents flowing in the alternating current circuits of the systern include currents at both leading and lagging power factors.

Another object of the present invention is to provide an improved control system for an electron discharge device whereby the device may 5 operate as an alternating current rectifier or a direct current inverter having an output voltage regulated independently of the power factor of the current in the alternating current circuit thereof. 10

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

Figure l diagrammatically illustrates one embodiment of the present invention applied to the control of an electron discharge device operable as an alternating current rectifier or a direct current inverter and whereby the alternating current flowing between an alternating current line and the device is maintained at substantially unity power factor; and

Figure 2 diagrammatically illustrates a modified embodiment of the present invention operable for regulating, at will, the power factor of the current flowing between an alternating current line and two electron discharge devices operating in parallel as alternating current rectifiers or direct current inverters.

Referring more particularly to the drawings by characters of reference, reference numeral 6 designates an alternating current line of any desired number of phases and operating at a suitable voltage of any desired frequency, and which is to supply current to or receive current from a direct current line I, B. The relative potentials of conductors l and 8 will then depend on the direction of the flow of energy between the two lines as is well known in the art. Line 6 is connected with the primary Winding 9 of a trans former designated generally by I l and having a plurality of secondary windings l2, 13, i4 and I 6, each comprising a plurality of phase displaced sections connected in star to form a neutral point. The several sections of windings i2 and I3 constitute a six-phase system of which the neutral points may be connected directly or, preferably, through an interphase transformer 17 to cause simultaneous flow of current at every instant through both windings l2 and I3 as is well known in the art. Windings l4 and i6 likewise constitute a six-phase system having two neutral points connected either directly or through an interphase transformer 58. some of the windings may be provided with taps and may be difierent from the remainder of such windings but in the present embodiment itwill be assumed that the four windings are of similar construction to deliver terminal voltages of equal magnitudes.

Interphase transformers H and [8 are provided with mid-taps which are connected with conductor 7 either directly or, preferably, through an interphase transformer L9 to cause simultaneous flow of current at every instant through windings i2 and I3 and through windings Hi and it. The winding of interphase transformer is is constituted of two portions which may have different numbers of turns and of which one portion may be provided with taps, but such portions will be constructed with equal numbers of turns if the electrical characteristics of windings i2 and i3 and of windings l4 and I6 are identical. The phase portions of windings l2 and I3 are severally connected with anodes 2! of an electron discharge device 22 having a cathode 23 connected with conductor 8. In considering the operation of the system herein described it will be assumed that the electron discharge device 22, which will be referred to as rectifier 22 for the sake of brevity, is utilized for supplying line i, 8 with rectified current obtained from line 6. Such current is supplied to suitable current consuming devices (not shown) which will generally be connected between conductors 'i and 8. If the current consuming device is an electric motor, some of the windings thereof may also be connected between transformer H and anodes 2i as is well known in the art.

The flow of current through each anode 2| is controlled by means of a control electrode 24 of a type operable to interrupt the fiow of current through the anode at will upon energization of the control electrodes at a suitable potential from a suitable source. If rectifier 22 is of the vacuum type, the usual type of control electrode may be utilized. If rectifier 22 is however of the vapor type, the control electrode must be capable of removing the positive ionic charges present in the space between the anode and the control electrode at a rate greater than the rate of appearance of ions within such space. Such appearance of ions may be the result of collisions between electrons and vapor atoms or of wandering of ions from the space outside the control electrode through the openings thereof. In addition to the above mentioned removal of ionic charges, the control electrode should cause repulsion of the electrons produced at the cathode or in the space outside the control electrodes so as to prevent any further transport of charges to the anode.

To obtain such result without resorting to the energization of the control electrode at such high potential as to introduce disturbances in the operation of the rectifier the dimensions of the control electrode cannot be chosen arbitrarily but must be within predetermined limits. It has been found, for instance, that the desired result can be obtained by means of a control electrode having the openings thereof, which are available for the passage of the discharge, so dimensioned that the ion sheaths formed about the several portions of the control electrode structure entirely fill such openings when the control electrode is unenergized and is not traversed by the are. In addition to the above mentioned overlapping of the ion sheaths, it is preferable to provide the openings in such numbers that their total area is approximately equal to forty percent of the area of the anode in contact with the discharge, to make the distance between the control electrode and the anode substantially equal to the mean free path of the electrons, and to provide the area of the control electrodes in contact with the space contained between such electrode and the associated anode, plus the total area of the surfaces of such control electrode forming the openings thereof, equal to at least two and one-half times the total cross sectional area of such openings. It will be understood, however, that some control electrodes of dimensions other than the above are also suitable for obtaining the desired result.

The discharge occurring at such anode M is preferably also caused to come in contact with another electrode 28 connected with the anode through a resistor 2'3, the purpose of such electrode being to carry an uncontrolled current ionizing the discharge path of the anode and also to dissipate the surges appearing at the anode upon interruption of the flow of current therethrough by means of the control electrodes. The different phase portions of windings it and it are severally connected with further anodes 2.8 of rectifier 22 similar to anodesZl and similarly provided with control electrodes 2. 5 and with auxiliary electrodes 3% connected with the anodes through resistors 32.

Control electrodes 2% and 28 are connected through two groups of resistors 33 and 3 and two further groups of resistors 36 and 3'5 with the negative terminal of a source of direct current such as a battery 33. The two terminals of battery E38 are connected with a voltage divider 39 having an intermediate tap connected with cathode 23, thereby causing the potentials of the terminals of battery 33 to be in definite relation with the potential of cathode 23. The positive terminal of battery 38 is connected through contacts 4| of a relay $2 with the brushes es and id of two distributors 46 and ll. Brush E3 is driven at a speed in fixed relation with the voltage cycle of line 6 by suitable means such as a synchronous motor 33 having an armature winding connected with line 5 and a field structure 5! provided with a plurality of circumferentially spaced windings. Brush M is likewise driven by an armature winding 53 energized from line 5 and a field similar to field 5i.

The windings of fields 5i and i i are preferably energized from battery 38, the distribution of current through the several portions of each winding being regulated by means of a regulator 56. Such regulator comprises a torque producing element 5? energized in a manner depending upon the method of regulation desired. In the present embodiment element 5? is connected across line i, 8 through a rheostat E58 to thereby become responsive to the magnitude of the voltage of line I, 3. Element 5'5 may also be further energized in function of the magnitude of the current in conductor 8 by connection thereof with a shunt 59 and an adjusting rheostat 6!. The torque of element 5? is opposed to the torque of suitable restraining means such as a wring iii! to cause the regulator to take different positions in dependence upon the values of the voltage of line i, 8 and of the current in conductor 8.

The regulator is provided with one or more movable contact sectors such as 552 and 53 rocking in operative contact with one or more resistors such as 5-1 and se. In the present embodiment, sectors 52 and 63 are severally connected with the terminals of batter 38 while resistors t3 and 58 are connected with the terminals, not connected with the battery, of fields 5i and 5% respectively. Due to this arrangement,

a synchronous motor 52 having fields 5| and 54 are similarly energized when regulator 56 is in the position shown and, upon movement of the regulator, the energization of fields 5| and 54 is so modified as to cause field 55 to lag and field 54 to lead with respect to the rotating magnetic fields which are produced in windings 59 and 5-3 as a result of the energization thereof from line 6. Relay 42 is energized from a current transformer 68 inserted in the connection between line 6 and winding 9 and operates upon occurrence of excessive flow of current through current transformer 53 to open contacts 4i and to connect the positive terminal of battery 38 with cathode 23 through a second pair of contacts 69.

In operation, assuming line B to be energized, winding 9 receives current therefrom and induces identical six-phase voltages in windings l2 and I3 and in windings I4 and Hi. In the absence of control electrodes in rectifier 22, windings l2 and I3 would carry current, at a comparatively high lagging power factor, to be rectified through anodes 2| and delivered to line I, 8. In a similar manner, windings i4 and 16 would carry current at also a comparatively high lagging power factor and to be rectified through anodes 28 operating in parallel with the corresponding anodes 2|. The output voltages of windings l2 and I 3 and windings l4 and I6 would then be identical and simultaneous flow of current therethrough would be obtained at every instant even in the absence of interphase transformer l9.

Such operation is variably modified by the action of control electrodes 24 and 29, which are! generally maintained at a negative potential with respect to the potential of the cathode 23 by means of battery 38. Upon energization of line 6, motor armatures 49 and 53 are energized therefrom and motors 48 and 52 may be started by any well known means and brought to ap proximately synchronous speed. Energization of field 5i and 54 with direct current then causes such motor to operate in synchronism with the voltage cycle of line 6. It will be assumed that, when regulator 55 is in the position shown, motors 18 and 52 drive brushes 43 and 44 in a manner such that a positive electromotive force is impressed thereby on each control electrode at the instant at which the associated anode becomes positive with respect to the anode or anodes previously carrying the discharge, and is removed when the associated anode becomes negative with respect to the anode or anodes to which such discharge is to be transferred. The control electrodes are then without effect on the flow of current through rectifier 22 and do not cause any regulation of the output voltage thereof.

Flow of such current may therefore occur through rectifier 22 and causes line I, 8 to become energized at the maximum voltage thereof and energize the windings of element 5! of the regulator 55. Element 5! then produces atorque overcoming the torque of spring 68, thereby causing sectors 62 and 63 to rock and change the points of contact thereof with resistors 64 and 85. The flow of current through fields 55 and 54 is thereby varied in such manner that field 5i lags and field 55 leads with respect to the rotating field of the associated armatures. The times of energization of control electrodes 25 are thereby retarded and the times of energization of control electrodes 25 are advanced.

Control electrodes 24 therefore sequentially release and interrupt the flow of current through the several anodes 2! at times of the voltage cycle later than the times of initiation and termination of such flow of current in the absence of control electrodes, thereby causing the flow of current from windings i2 and i3 through anodes 2 to occur at a r duced effective voltage; the reduction of such voltage is affected to an extent depending upon the extent of the movement of regulator 56 and the extent of the resulting lag of brush 43. As is well known, the flow of current through windings l2 and !3 then occurs at a reduced lagging power factor commensurate with the extent of reduction of the voltage of line 1, 8. Interphase transformer l8 continues to operate in the normal manner thereof, only the voltages appearing across the terminals thereof are of larger magnitudes than the voltages present in the absence of regulation by means of control electrodes.

Control electrodes 28, on the quentially release and interrupt the flow of current through the associated anodes 28 prior 501 the times of initiation and termination of the flow of current therethrough in the absence of control electrodes to supply current to line 1,3 at the same efiective rectified voltage as anodes 2i. Windings M and then carry current substantially equal in magnitude to the current in windings l2 and i3 and flowing at a reduced leading power factor substantially equal in magnitude to the lagging power factor of the current in windings l2 and i3. Interphase transformer ll operates in the normal manner thereof sinnlarly to interphase transformer it. With proper selection of the transformation ratio of transformer ii, the current flowing through winding 9 and received by such winding from line 6 is equal to the sum of the currents flowing through all the secondary windings and is th refore substantially in phase coincidence with the voltage or, in other words, the current flow occurs at substantially unity power factor.

Windings l2 and i3 and windings M and I6 supply current to line i, 8 at average voltages of equal magnitudes but differing at every instant as a result of the presence or different alternating components therein resulting from the action of the control electrodes. Such components appear across the terminals of interphase transformer is, and flow of current occur simultaneously at every instant through all the secondary windings and is delivered to line 7, 3 at the average effective voltage of all the windings. Regulator 5t continues its movement until the voltage of line 7, S is reduced to an extent such that the torque of element 5! becomes equal to the torque of spring 66. Regulator 55 then stops and maintains the voltage of line 2-, 8 at a value depending upon the adjustment of rheostats 58 and 5!.

In the above explanation it was assumed that the secondary windings of transformer I! had equal reactances so that equal flows of current would occur therethrough if the lag of control electrodes l was exactly equal to the lead of control electrodes 29. It may he found, however, that the elfective output voltages of windings i2 and and of windings i and i5 actually are not exactl equal. equality of the voltages may be restored by making the lag of control electrodes 24 slightly diifere t in magnitude from the lead of control electrodes 2!, for instance by suitably modifying resistor $4 or resistor 66.

other hand, se-

As a result of the above method of operation, control electrodes 2 and 29 with battery 33 and distributors Q5 and 52 constitute means for controlling the fiow of current through anodes 2i and 28, through which the control electrodes are operable to release and also to interrupt the flow of current. Transformer H, which connects rectifier 22 with line 6 and with line '1, 8 has distinct duplicate windings l2, l3 and M, It to which the groups of anodes 2i and 28 are connected. Distributors 56 and 52 sequentially impress recurring electromotive forces from battery 53 on the several control electrodes 2d and 29, such electrcmotive forces being operable to cause a regulated flow of current to occur through rectifier 22. Such flow of current is controlled by regulator til, which operates automatically in response to an electrical condition of the system to maintain the voltage line i, S at predetermined values. The flow of current through the system between line 6 and rectifier 22 occurs at substantially unity power factor, the flow of current through anodes 2! being retarded and the flow of current through anodes 28 being advanced. Such result is obtained'by simultaneously advancing the impression of the electromotive forces on one group of control electrodes and retarding the impression of electrornotive forces on the other group of control electrodes. The flow of leading current in wind- Hi and i6 and of lagging current in windings i2 and it are of substantially equal magnitudes and result in flow of substantially equal amounts of energy therethrough between the two lines.

' In the embodiment illustrated in Figure 2 it is assumed that windings 9, l2 and i3 are arranged on a first magnetic structure to constitute a first transformer ii While windings M and iii are arranged on a second magnetic structure with another primary winding '52 energized from line 6 to constitute a second transformer it. In order to generalize the scope of the invention it is also assumed that, in the present embodiment, windings l2 and i3 and windings l4 and it are of different voltages and have different current ratings. Anodes 2i and 28 may again be arranged in a single rectifier 22 or may be arranged in two separate rectifiers l6 and ll having two cathodes it and it connected with conductor 8. In this manner it is therefore possible to construct a unit system by means of two independent rectifying systems of different construction.

Control electrodes 2d and 29 may be energized in a manner similar to that illustrated in Figure l or in any other suitable manner. For instance, control electrodes 2 may be energized from the star connected secondary Winding of a transformer '59 energized from line 6 and control electrodes 29 may be energized in a similar manner from a second transformer 8|. The neutral point of the secondary winding of transformer is is preferably maintained at a variable negative potential with respect to the potential of cathode it such as by means of a voltage divider connected between conductors l and 8 and comprising resistor 6d and adjusting rheostats and 3%. The negative electromotive force impressed between conductor 8 and the neutral point of the secondary winding is then the voltage drop in the rheostats and in the resistor between such neutral point and conductor 8. The regulation of such electromotive force results from the action of regulator 55, in which sector 63 is operatively connected to short circuit a variable amount of resistor 6 The flow of current may be maintained uniform in the voltage divider by means of a reactor 82. Transformer 3! is similarly associated with a voltage divider comprising rheostats 87 and 89, a reactor 8% and the resistor 88 of a second regulator 9i arranged similarly to regulator but with the restraining means of very reduced effect or even entirely omitted.

The torque element of regulator 95 may be connected as element 5'3, but is more advantageously energized in response to electrical conditions of interphase transformer IS such as the signs and magnitudes of the direct current voltage components which appear across the terminals of such interphase transformer. The connection between the regulator ti and interphase transformer 19 may be variably effected through taps of the interphase transformer winding or of a voltage divider 9t and preferably comprises a reactor 92 for preventing the flow of alternating current through the coil of regulator 95.

The operation of anodes 2% is controlled in the same manner in the present embodiment and in the embodiment illustrated in Figure 1. In the present embodiment both the positive and negative electromotive forces impressed on control electrodes 2 result from the combination of the voltages of transformer T9 and of the associated voltage divider. The output voltage of rectifier it is therefore maintained at values depending on the adjustment of regulator 56, and the flow of current between line 6 and winding 9 occurs at a lagging power factor having a magnitude depending upon the degree of regulation produced by regulator 56.

Control electrodes 29 are not controlled directly in dependence upon the voltage of line i, 8 but are controlled in a manner such as to cause the average output voltage of rectifier ll to be equal to the average output voltage of rectifier Hi. If such average voltages are not equal, the difference therebetwe-en appears accross the term'mals of interphase transformer is and causes a flow of current through the coil of regulator Ql. Regulator 9! then operates to vary the negative direct current voltage current component impressed on control electrodes 29 to thereby adjust the times of energization of control electrodes 29 at positive and at negative potentials with respect to the potential of cathode '58. Such action continues until the output voltages of rectifiers i l and il are equal and a direct current voltage component is no longer present in interphase transformer 59, regulator 9! then remaining in the position reached thereby. Regulator 9! is so connected that the regulating action thereof causes an advance in the times of energization of control electrodes 29 to thereby cause rectifiers H to receive current at a leading power factor from line 6. It will be understood that operation of regulator 9i to regulate the flow of current through rectifier ll will also cause the magnitude of the current through rectifier i l to change, and regulator 56 must then operate further to compensate for the action of regulator 9!.

In the present embodiment also the total current drawn from line B may therefore be maintained substantially in phase with the voltage. If the phase voltages of windings l2 and i3 and windings It and it are equal, the lead given to control electrodes 26 will be substantially equal to the lag given to control electrodes 29 to obtain equal output voltages for rectifiers 14 and 11. If the phase voltages of windings l4 and I6, for instance, are greater than the phase voltages of windings l2 and I3, the lead of control electrodes 29 will have to be increased as compared to the lag of control electrodes 24 to reestablish the equality of the output voltages. lhe result of such control will then be that all windings will again carry currents of equal magnitudes, but the leading power factor of the current in transformer it will be smaller than the lagging power factor of the current in transformer ll and the total current drawn from line 6 will be leading. A flow of lagging total current would be obtained by adjusting windings l2 and i3 to deliver phase voltages greater than the phase voltages of windings l4 and It.

If the two transformers are of different current carrying capacities it is preferable to adjust the winding portions of interphase transformer 19 with numbers of turns in inverse ratio to the amounts of current to be carried thereby. The connection of interphase transformer l9 with regulator ill should then be so adjusted that the winding of regulator 9! receives no current when the flows of current through the two portions of the interphase transformer are in the desired proportion. Regulator fl then will control the cnergization of control electrodes 29 to cause rectifiers l4 and 7'! to deliver average voltages of substantially equal magnitudes while maintaining the output currents thereof in the desired proportion, whereby current operation of interphase transformer I9 is again obtained. Windings l2 and i3 and windings l4 and "5 then carry currents of different magnitudes at relative values of power factor depending upon the relative values of the phase voltages of such windings. By varying the adjustment of the magnitudes of phase voltages and the adjustment of interphase transformer 19, windings 9 and 12 may be made to receive from line 6 currents of magnitudes and power factors in any desired relation, and therefore the total flow of current between line 6 and rectifiers l4 and ll may be adjusted to occur at any desired leading or lagging power factor.

In the present embodiment therefore windings i2, i3 and M, iii are of different voltages, but although such windings are shown as forming parts of separate transformers they could equally as well be arranged in a single transformer structure. Similarly rectifiers l4 and ll could be replaced by a single rectifier such as rectifier 22. Regulators 56 and 9! cooperate to perform the functions performed by regulator 56 alone in the embodiment illustrated in Figure 1. Such regulators permit obtaining flow of electrical energy at different leading and lagging power factors in the windings of the transformers, thereby causing the flow of current at any desired power factor between line 5 and rectifiers l4 and l. Such lagging and leading currents always flow at substantially the same effective or average terminal voltage. Although regulators 56 and all act cooperatively, they operate independently for severally adjusting the impression of electromotive forces on the one and on the other group of control electrodes.

Although but two 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 Patent:

1. In a system for controlling the flow of electric current, an electric current circuit, a second electric current circuit, electron discharge means having a plurality of anodes and a cathode, means for connecting said discharge means with each of said circuits, a plurality of control electrodes severally operable to release and to interrupt the flow of current through said anodes, a source of electromotive force connected with said cathode, means for continually impressing electromotive forces from said source control electrodes, and means controlling the last said means and operable to simultaneously advance the impression of said electromotive forces on some of said control electrodes and retard the impression of said electromotive forces on others of said control electrodes.

2. In a system for controlling the flow of electric current, an alternating current circuit, an electron discharge device connected with said circuit and having a plurality of anodes and a cathode, a direct current circuit connected with said circuit and with said discharge device, a plurality of control electrodes severally operable to release and to interrupt the flow of current through said anodes, a source of electromotive force connected with said cathode, means for continually impressing electromotive forces from said source on desired to secure by Letters electromotive electrodes.

3. In a system for controlling the flow of electric current, an alternating current circuit, a transformer connected with said circuit and having a plurality of windings, an electron discharge device having two groups of anodes connected with distinct windings of said transcontinually impressing electromotive forces from said source sequentially on the several control electrodes of each group to cause a regulated flow of current to be established through said discharge device, and means controlling the last said means and operable to simultaneously advance the moments of impression of said electromotive forces on the control electrodes of one group and retard the moments of impression of said electromotive forces on the control electrodes of the other group.

4. In a system for tric current, an transformer controlling the flow of elecalternating current circuit, a

on said tromotive force connected with said cathode, means for continually impressing electromotive forces from said source sequentially on the several control electrodes of each group of such sign and magnitude and during such recurring moments as to cause flow of leading current in one of said distinct windings and of lagging current in another of said distinct windings.

5. In a system for controlling the flow of electric current, an alternating current circuit, a transformer connected with said circuit and having a plurality of windings, an electron discharge device having two groups of anodes connected with distinct windings of said transformer and having a cathode, a direct current circuit connected with said transformer and with said discharge device, control electrodes in two groups severally operable to release and to interrupt the flow of current through said groups of anodes, a source of electromotive force connected with said cathode, means for continually impressing electromotive forces from said source sequentially on the several control electrodes of each group of such sign and magnitude as to cause each control electrode to control the establishment of said arcs by way of the associated anode and to effect the interruption thereof at such moments as to cause flow of current at substantially unity power factor between said alternating current circuit and said transformer.

6. In a system for controlling the flow of electric current, an alternating current circuit, a

transformer connected with said circuit and having a plurality of windings, an electron discharge device having two groups of anodes connected with duplicate windings of said transformer and having a cathode, a direct current circuit connected with said transformer and with said discharge device, control electrodes arranged in two groups and severally operable to release and to interrupt the flow of current through said groups of anodes, a source of electromotive force connected with said cathode, means for continually impressing electromotive forces from said source sequentially on the several control electrodes of each group of such sign and magnitude and during such moments as to cause flow of leading current in one of said duplicate windings and of lagging current of equal magnitude in the other of said duplicate windings.

7. In a system for controlling the flow of electric current, an alternating current circuit, a transformer connected with said circuit and having a plurality of windings of different voltages, an electron discharge device having two groups of anodes connected with windings of different voltages of said transformer and having a cathode, a direct current circuit connected with said transformer and with said discharge device, control electrodes arranged in two groups and severally operable to release and to interrupt the flow of current through said groups of anodes, a source of electromotive force connected with said cathode, means for continually impressing electromotive forces from said source sequentially on the several control electrodes of each group of such sign and magnitude and during such moments as to cause flow of electrical energy at leading and lagging power factors respectively of diiferent values through said windings of different voltages.

8. In a system for controlling the flow of electric current, an alternating current circuit, a

transformer connected with said circuit and having a plurality of windings of different voltages, an electron discharge device having two groups of anodes connected with windings of diiferent voltages of said transformer and having a cathode, a direct current circuit connected with said transformer and with said discharge device, control electrodes in two groups and severally operable to release and to interrupt the flow of current through said groups of anodes, a source of electromotive force connected with said cathode, means for continually impressing electromotive forces from said source sequentially on the several control electrodes of each group of such sign and magnitude and during such moments as to cause flow of leading current in one of said windings of different voltages and lagging current at the same effective voltage in the other of said windings of different voltages.

9. In a system for controlling the flow of electric current, an alternating current circuit, an electron discharge device connected with said circuit and having a plurality of anodes and a cathode, a direct current circuit connected with said circuit and with said discharge device, a plurality of control electrodes severally operable to release and to interrupt the flow of current through said anodes, a source of electromotive force connected with said cathode, means for continually impressing electromotive forces from said source on said controlelectrodes of such sign and magnitude as to cause each control electrode to control the establishment of said arcs by way of the associated anode and to effect the interruption thereof at such moments as to cause flow of current at any desired power factor between said alternating current circuit and said discharge device.

10. In a system for controlling the flow of electric current, an alternating current circuit, a transformer connected with said circuit and having a plurality of windings, an electron discharge device having two groups of anodes connected with distinct windings of said transformer and having a cathode, a direct current circuit connected with said transformer and with said discharge device, control electrodes arranged in two groups and severally operable to release and to interrupt the flow of current through said groups of anodes, a source of electromotive force connected with said cathode, means for continually impressing electromotive forces from said source sequentially on the several control electrodes of each group of such sign and magnitude and during such moments as to cause flow of leading current in one of said distinct windings and lagging current in the other of said distinct windings, and means controlling the last said means and operable to simultaneously advance the impression of said electromotive forces on the control electrodes of one group and retard the impression of said electromotive forces on the control electrodes of the other group.

11. In a system for controlling the flow of having a plurality of release and to interrupt the flow of current through said groups of anodes, a source of electromotive force connected with said cathode, means for continually impressing electromotive forces from said source sequentially on the several control electrodes of each group of such sign and magnitude and during such moments as to cause flow of leading current in one of said distinct windings and lagging current in the other of said distinct windings, and means controlling the last said means and operable coextensively to simultaneously advance the impression of said electromotive forces on the control electrodes of one group and retard the impression of said electromotive forces on the control electrodes of the other group.

12. In a system for controlling the flow of electric current, an alternating cu rent circuit, a transformer connected with said circuit and windings, an electron discharge device having two groups of anodes connected with distinct windings of said transformer and having a cathode, a direct current circuit connected with said transformer and with said discharge device, control electrodes arranged in two groups and severally operable to release and to interrupt the flow of current through said groups of anodes, a source of electromotive force connected with said cathode, means for continually impressing electromotive forces from said source sequentially on the several control electrodes of each group of such sign and magnitude and during such moments as to cause flow of leading current in one of said distinct windings and lagging current in another of said distinct windings, and independent means for severally adjusting the impression of said electromotive forces simultaneously on the one and on the other groups of said control electrodes.

13. In a system for controlling the flow of electric current, an alternating current circuit, a transformer connected with said circuit and having a plurality of windings, an electron discharge device having two groups of anodes connected with distinct windings of said transformer and having a cathode, a direct current circuit connected with said transformer and with said discharge device, control electrodes arranged in two groups and severally operable to release and to interrupt the flow of current through said groups of anodes, a source of electromotive force connected with said cathode, means for continually impressing electromotive forces from said source sequentially on the several control electrodes of each group of such sign and magnitude and during such moments as to cause flow of leading current in one of said distinct windings and of lagging current in another of said distinct windings, and means for causing flow of current simultaneously through the one and the another of said windings at every instant.

14. In a system for controlling the flow of electric current, an alternating current circuit, a transformer connected with said circuit and having a plurality of windings, an electron discharge device having two grcups of anodes connected with distinct windings of said transformer and having a cathode, a direct current circuit connected with said transformer and with said discharge device, control electrodes arranged in two groups and severally operable to release and to interrupt the flow of current through said groups of anodes, a source of electromotive force connected with said cathode, means for continually impressing electromotive forces from said source sequentially on the several control electrodes of each group of such sign and magnitude and during such moments as to flow of leading current in one of said 6 l ct windings and lagging current in another of said distinct windings, and an ,interphase transformer connecting said transformer with said direct current line.

15. In a system for controlling the how of electric current, an alternating current circuit, a transformer connected with said circuit and having a plurality of windings, an electron discharge device having two groups of anodes connected with distinct windings of said transformer and having a cathode, a direct current circuit connected with said transformer and with said discharge device, control electrodes arranged in two groups and severally operable to release and to interrupt the flow of current through said groups of anodes, a source of electromotive force connected with said cathode, means for continually impressing electroinot-ive forces from said source sequentially on the several control electrodes of each group of such sign and magnitude and during such moments as to cause flow of leading current in one of said distinct windings and lagging current in another of said distinct windings, and means responsive to an electrical condition of said system controlling the last said means and operable to iultanecusly advance the impression of electrornotive forces on the control electrodes of one group and retard the impression of said elcc tromotive forces on the control electrodes of the other group.

16. In a system for controlling the flow of electric current, an alternating current circuit, a transformer connected with said circuit and having a plurality of windings, an electron discharge device having two groups of anodes connected with distinct windings of said transformer and having a cathode, a direct current circuit connected with said transformer and with said discharge device, control electrodes arranged in two groups and severally operable to release and to interrupt the flow of current through said groups of anodes, a source of electromotive force connected with said cathode, means for continually impressing electrometive forces from said source sequentially on the several control electrodes of each group of such sign and magnitude and during such moments as to cause flow of leading current in one of said distinct windings and lagging current in another of said distinct windings, and automatic means controlling the last said op-- erahle to simultaneously advance the impression of said electromotive forces on the control electrodes of one group and retard the impression of said electromotive forces on the control electrodes of the other group.

17. In a system for controlling the flow of electric current, an alternating current circuit, an electron discharge device connected with said circuit and having a plurality of anodes a cathode, a direct current circuit connected with said circuit and with said dischar e device, a plurality of control electrodes severally operable to release and to interrupt the flow of cur through said anodes, a source of electro active force connected with said cathode, m .s for continually impressing electromotive forces from said source on each said control electrode to cause the release of said flow of current by way S aoassoc of the associated anode and to eifect the interruption thereof, and regulating means cooperating with the last said means to vary the :moments of said impression of said electromotive forces to cause flow of current at substantially unity power factor between said alternating current circuit and said discharge device.

13. In a system for controlling the flow of electric current, an alternating current circuit, a transformer connected with said circuit and having a plurality of secondary windings, an interphase transformer joining the secondary windings of said transformer, said interphase transformer having a plurality of portions with unequal numbers of turns, an electron discharge device with separate groups of anodes connected with the secondary windings of said transformer and a cathode, a direct current circuit connected with said interphase transformer and with the cathode, control electrodes severally associated with the anodes, means for energizing said control electrodes, and means controlling the last said means and operable to simultaneously advance the flow of current through one group of the anodes and retard the flow of current through the other group of the anodes to obtain unity power factor between said alternating current line and said device.

19. The combination with an alternating current supply circuit, a load circuit, and means interconnecting said circuits comprising an electron discharge device having a cathode and a plurality of anodes divided into groups and constituting spaced electrodes for the flow of current between said circuits by way of arcs when established between said anodes and cathode, of means comprising control electrodes severally associated with said anodes and so dimensioned and disposed relative to the associated anodes as to be operable to control the establishment of said arcs and to effect the interruptions thereof, means comprising sources of current having connections with said cathode and continually impressing electromotive forces sequentially on the several control electrodes associated with the said anodes of each group thereof of such signs and magnitudes as to cause each control electrode to control the establishment of said arcs by way of the associated anode and to effect the interruption thereof at such moments as to thereby cause the said flow of current from said supply circuit at any desired power factor.

20. The combination with an electric current supply circuit, a load circuit, one of said circuits being an alternating current circuit, and means interconnecting said circuits comprising an elecron discharge device having a cathode and a plurality anodes divided into groups and constituting spaced electrodes for the flow of current between said circuits by way of arcs when established between said anodes and cathode, of means comprising control electrodes severally associated with said anodes and so dimensioned and disposed relative to the associated anodes as to be operable to control the moments of establishment of said arcs and the moments of interruption thereof, means comprising a source of current having connection with said cahtode and continually impressing electromotive forces sequentially on the control electrodes associated with the said anodes of each group thereof of such signs and magnitudes and during such moments as to control the moments of establishment of said arcs and the moments of interruption thereof, and means operable to simul taneously-advance the moments of impression of said electromotive forces. on the control electrodes associated with the anodes of one of said groups thereof and retard the moments of impression of said electromotive forces on the control electrodes associated with the anodes of another of said groups thereof, whereby leading current is caused to flow through the anodes of the said'one group thereof and lagging current through the anodes of the said another group thereof.

21. The combination with an alternating current supply circuit a load circuit, and means interconnecting said circuits comprising an electron discharge device having a cathode and a plurality of anodes divided into groups and constituting spaced electrodes for the flow of current between said circuits by way of arcs when established between said anodes and cathode,

of means comprising control electrodes severally associated with said anodes and so dimensioned and disposed relative to the associated anodes as to be operable to control the moments of establishment of said arcs and the moments of interruption thereof, means comprising a source of current having connection with said cathode and continually impressing electromotive forces sequentially on the control electrodes associated with the anodes of each group thereof of such sign and magnitude and during such moments relative to the voltage frequency of the said supply circuit as to control the moments of establishment of said arcs and the moments of interruption thereof, means operable to simultaneously advance the moments of impression of said electromotive forces on the control electrodes associated with the anodes of one of said groups thereof and retard the moments of impression of said electromotive forces on the control electrodes associated with the anodes of another group thereof, and means operable responsive to and independence on the flow of energy in one of said circuits for controlling the operation of the fourth said means, whereby current at any desired power factor is caused to flow from one to another of said circuits.

22. The combination with an alternating current supply circuit, a load circuit, and electron discharge means interconnecting said circuits comprising a cathode and a plurality of anodes constituting spaced electrodes for the flow of current by way of arcs when established therebetween, of means comprising control electrodes severally associated with said anodes and so dimensioned and disposed relative thereto as to be operable to control the establishment of said arcs and to effect the interruption thereof, means comprising a source of current having connection with said cathode and continually impressing electromotive forces sequentially on said control electrodes of such signs and magnitude as to cause each control electrode to control the establishment of said arcs by way of the associated anode and to effect the interruption thereof, and means operable responsive to and in dependence on changes in an operating condition of said system and cooperating with the fourth said means to vary the moments of the impressions of said electromotive forces on said control electrodes, to thereby cause said I flow of current to occur at a predetermined power factor.

ERWIN KERN.

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