US2038505A - Rectifier control system - Google Patents

Description

H. RNOGRAD RECTIFIER CONTROL SYSTEM 3 Sheets-Sheet 1 Filed Aug. '7, 1935 IIIIVV nmmm 4/ H. WHNOGRAD RECTIFIER CONTROL SYSTEM Filed Aug. 7, 1955 3 Sheets-Sheet 2 April 21, 1936. H. wlNosRAD v2,038,505.")

RECTIFIER CONTROL SYSTEM Filed Aug. 7, 1933 3 Sheets-Sheet 3 Patented Apr. 21, 1936 UNETED STATES PATENT OFFKIE RECTIFIER CONTROL SYSTEM Application August 7,

22 Claims.

This invention relates in general to improvements in control systems and more particularly to means for maintaining a predetermined dis tribution of the flow of current in parallel circuits including electron discharge devices.

An electron discharge device may be employed in systems of different natures such as alternating current rectifying systems, direct current inverting systems, frequency changing systems, motor control systems, etc., presenting a plurality of parallel circuits for the flow of current. It is generally advantageous to obtain and maintain a simultaneous flow of current through the several parallel circuits of the system to improve the voltage characteristics and the efficiency thereof. Such simultaneous flow of currents may be inherently caused by the connections of the system and may result from the relative values of the impedances of the parallel circuits or from the use of current balancing means such as the so-called interphase transformers. The distribution of current in the parallel circuits may, however, occur in a manner diiTering from the desired manner either as a result of unbalanced impedances in the parallel circuits, or of unstable action of the control electrodes of the discharge devices, or as a result of the presence of harmonics in the voltage of alternating current circuits constituting part of the system. A variation of the distribution of current in the several circuits causes some of such circuits to be overloaded and is particularly objectionable when such circuits contain interphase transformers which become inoperative when such current unbalance causes the core of the interphase transformer to become saturated.

The desired current distribution may be maintained by supplementing the means designed to inherently produce such distribution with means responsive to the flow of current and operable to restore the desired current distribution when such distribution is disturbed. Such means should preferably cooperate with any means utilized for regulating the operation of the system and with any means utilized for causing the system to become inoperative upon the occurrence of serious disturbance therein.

It is therefore among the objects of the present invention to provide an improved control system for electron discharge devices whereby the desired current distribution is obtained and maintained in a plurality of electrically distinct circuits associated with the device.

Another object of the present invention is to provide an improved control system for electron 1933, Serial No. 683,940

discharge devices whereby the current distribution in the several circuits of the device is maintained invariable under all operating conditions.

Another object of the present invention is to provide an improved control system for electron discharge devices whereby the current distribution in the. circuits of the device is maintained invariable irrespective of the imperfections of the means inherently designed to produce such current distribution.

Another object of the present invention is to provide an improved control system for electron discharge devices whereby the total flow of cur rent through the devices is coordinately regulated with the flow of current through the several parallel circuits.

Another object of the present invention is to provide an improved control system for electron discharge devices whereby the flow of current through the device may be interrupted by means cooperating with the means controlling the distribution of current through the several circuits of the device.

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 1 diagrammatically illustrates one embodiment of the present invention applied to the control of a six-phase electron discharge device operable as an alternating current rectifier whereby the flow of current in two parallel circuits are maintained at the same values and whereby the total current flowing through the system is maintained at a constant value;

Figure 2 diagrammatically illustrates another embodiment of the present invention maintaining a predetermined current distribution between two six-phase rectifiers and maintaining the output voltage of such rectifiers at a constant value; and

Figure 3 diagrammatically illustrates another embodiment of the present invention maintaining equal flow of current through the four parallel circuits of a 12-phase rectifier and maintaining the output energy of such rectifier at a constant value.

Referring more particularly to the drawings by characters of reference, the reference numeral 6 designates an alternating current supply line herein represented as a 3-phase line. An output direct current line having a negative conductor l and a positive conductor 8 receives current from line 6 through a system comprising a transformer 9 having a primary winding I0 connected with line 6 and having two 3-phase secondary windings II and I2. Windings H and I2 each comprise a plurality of phase displaced portions constituting a 6-phase system connected to form two neutral points. The several portions of winding II are each connected with an anode such as |3 of an electron discharge device l6 having a cathode l1 connected with conductor 8. The several portions of winding |2 are similarly connected with anodes such as l4 of device l6. The potential of cathode I! will be taken herein as a datum and all potentials will be referred thereto unless otherwise stated. Any source of electromotive force having a terminal connected with the cathode will then have the other terminal thereof at a potential equal to such electromotive force, and the source therefore also functions as a source of potential for any circuits connected therewith. The neutral points of windings II and I2 are connected with conductor 1 through the windings of an interphase transformer l8 and through a shunt I9 having the midpoint thereof connected with conductor 1. The current flowing through conductor 1 is therefore offered two parallel circuits each comprising a portion of shunt l9 and of interphase transformer l6, one of the phases of the windings H and I2, and some of the anodes of device I6; both circuits terminating at cathode l1. Such circuits, designated by 2| and 22, are distinct in their electrical functions and may even be physically distinct if the anodes of each circuit are assembled in separate electron discharge devices having the cathodes thereof connected with conductor 8. Device l6 may also be replaced by a plurality of devices each containing a single anode and a cathode without, however, changing the nature of the operation thereof.

The flow of current through device I6 is controlled by a plurality of control electrodes such as 23, 24 severally associated with the anodes of the device. The control electrodes are energized at recurring potentials by means of a transformer 25 having a primary winding 26 energized from line 6 and having two secondary windings 21 and 28 each comprising a plurality of phase displaced portions connected to form a neutral point therefor. The voltage of windings 21 and 28 preferably have peak values smaller than the value of the voltage of line 8. The neutral points of windings 21 and 28 are connected, through the contacts of a time delay relay 29, with the taps of two rheostats 30 and 3| associated with further rheostats 32, 33 and 34 to form a pair of voltage dividers connected between conductors and 8. Rheostat 32 is constructed as a part of a regulator 36 operable to vary the point of connection of rheostat 32 with rheostat 33, such variation being effected in response to the appearance of current unbalance in circuits 2| and 22. To obtain this effect, regulator 36 is energized at the voltage between the terminals of shunt l9, either directly or through a reactor 31 which permits the passage therethrough of only the direct current component of the voltage. Rheostat 33 is constructed as a part of a second regulator 38 operating in response to the magnitude of the current flowing through a shunt 39 inserted in conductor 8, to vary the amount of rheostat 33 inserted in circuit with rheostats 30, 3|, 32 and 34. The operation of regulator 38 may be adjusted by means of a rheostat 4| inserted in the energizing circuit thereof. Windings 21 and 28 may be disconnected from rheostats 30 and 3| by relay 29 which connects such windings between a capacitor 42 connected with conductor 8 and a high resistance resistor 43 connected with conductor 1. The coil of relay 29 is energized in response to the magnitude of the current of winding ID by means of a current transformer 44.

As a result of the above connections, circuits 2| and 22, which each comprise one or more anodes and control electrodes constitute electrically distinct circuits which inherently tend to cause the flow therethrough of currents in a ratio of predetermined magnitude. Such circuits are operable to carry currents having maximum values in the same predetermined ratio and include distinct discharge controlling means including the control electrodes such as 23 and 24. Line "I, 6, transformer 25 and rheostats 30 to 34, constitute means including a source of potential energizing the control electrodes in such a manner that such control electrodes receive therefrom recurring p0- tentials. Relay 29, which operates in response to the occurrence of abnormal conditions, overcomes the action of regulators 36 and 38 and cooperates with transformer 25 in controlling the energization of the control electrodes to cause the flow of current through device l6 to be extinguished. Regulator 36, which is responsive to the flow of current through circuits 2| and 22 and to the ratio of the magnitudes of such currents, tends to maintain the ratio of such currents invariable under all operating conditions, i. e., also when such conditions tend to cause the value of such ratio to vary. The regulator 36 controls the discharge controlling means in such a manner as to vary the times of application, in the supply voltage cycle, of control potentials to the two groups of control electrodes in opposite manner.

In operation, line 6 being energized and the system being connected as shown, and assuming that transformer 25 is so adjusted as to cause the system to operate to rectify alternating current received thereby from line 6 and to supply such rectified current to line I, 8; the several portions of windings and I2 and the associated anodes of device I6 sequentially carry currents which combine at cathode IT to form direct cur rent flowing to conductor 1. Interphase transformer I8 tends to cause such direct current to divide into two equal direct currents flowing though circuits 2| and 22. The flow of current through the several anodes of device I6 is released by the action of the associated control electrodes and is regulated in dependence upon the energization of such control electrodes from transformer 25 and line 1, 8. If the current flowing through conductor 8 is greater than is desired, regulator 38 varies the point of contact of the movable tap thereof with rheostat 33 to reduce the portion of rheostat 33 short circuited thereby. The negative direct current voltage component impressed on the control electrodes by the rheostats thereby increases causing the times of energization of all control electrodes to be retarded, with the result that the flow of current through device I6 and shunt 39 decreases as is well known in the art. Such action con tinues until the current is brought to the desired value, at which time regulator 38 remains in the position reached to maintain the flow of current at such value. If the flow of current is smaller than desired, the spring of regulator 38 returns the movable tap thereof toward the position shown to increase the short circuited portion of rheostat 33 and thereby decrease the direct current voltage component impressed on the control electrodes and increases the flow of current through device |6 to the desired value.

If the currents in circuits 2| and 22 are equal, the voltage drops in the two portions of shunt I9 are equal and no voltage is impressed therefrom on regulator 36. Such consideration neglects the comparatively small alternating current component of the current in circuits 2| and 22 which tends to cause the flow of alternating current through regulator 36, but such component may be neglected as the flow of alternatingcurrent through regulator 36 is prevented by reactor 31. In addition, such component would produce no torque as the field winding of the regulator is energized with direct current only. Regulator 36 then re mains in the position shown and the direct current voltage components impressed on the neutral point of windings 21 and 28 are equal. If, for any reason, the current in circuit 2| becomes greater than the current in circuit 22, the voltage drops in the two halves of shunt I9 become unequal and a. direct current flows from shunt l9 through the armature winding of regulator 36. Regulator 36 varies the position of the tap on rheostat 32 to cause a larger portion of rheostat 32 to be inserted in series with rheostat 30 and a correspondingly smaller amount of rheostat 32 to be inserted in series with rheostat 3|. The direct current voltage component received by winding 21 is therefore greater than the com ponent received by winding 28 and the flow of current through circuit 2| is decreased while the flow of current through circuit 22 is increased. Such action continues until full equality of the two currents is reestablished and regulator 36 then stops in the position reached thereby. Upon re moval of the cause disturbing the distribution of flow of current through circuits 2| and 22, regulator 36 returns to the position shown. A similar but opposite operation of the regulator 36 occurs if the current through circuit 22 becomes greater than the current flowing through circuit 2|.

During normal operation, capacitor 42 becomes charged at the voltage of line I, 8 through resistor 43. Upon occurrence of a disturbance such as a short circuit in line I, B or a backfire in device i6, the voltage of line I, B collapses and capacitor 42 tends to discharge through the line, such action being, however, greatly retarded as the discharge current must flow through resistor 43. Upon occurrence of such disturbance, the resulting flow of excessive current through winding l0 causes the coil of relay 29 to receive an increased current from current transformer 44, and relay 29 immediately attracts the armature thereof, thereby substituting, for the negative direct current voltage component previously impressed on the control electrodes from the voltage divider connection above described, the full operating voltage of line 1, 8 obtained from capacitor 42. The control electrodes are thereby constantly energized at negative potentials as the voltage of capacitor 42 is greater than the peak value of the alternating voltages of windings 21 and 28. The further flow of current through device IB is thus prevented and the backfire or short circuit is interrupted. After a predetermined time delay, relay 29 returns to the position shown to restore the system to the normal operating condition thereof.

In the embodiment illustrated in Figure 2, device I6 is represented as being connected with line 6 through a transformer 46 having winding Ill as the primary winding thereof, and having a 6-phase secondary winding 41 with the neutral point thereof directly connected with conductor 1. The control electrodes of device i6 receive alternating voltage components from a control transformer 48 having winding 26 as primary winding and provided with a G-phase secondary winding 49. Winding I0 is connected with line 6 through a circuit breaker 5| having auxiliary contacts 52 controlling the connection of the closing coil of a circuit breaker 53 with a battery 54. Circuit breaker 53 connects winding 26 with line 6 and also connects the neutral point of Winding 49 with rheostat 36. A second electron discharge device 56 is connected in parallel with device Hi,

the anodes of device 56 being severally connected with the phase portions of the secondary winding 55 of a second transformer 51 connected with line 6. The control electrodes of device 56 are energized by means of a second control transformer 58. winding of transformer 58 is connected with rheostat 3| from which it receives a direct current voltage component for the energization of the control electrodes of device 56. Devices l6 and 56 are connected with conductor 8 through a shunt 55 having two portions of relatively adjustable resistance values. The voltage terminals of shunt 56 are connected with the coil of regulater 36 in a manner similar to that illustrated for the connection of shunt l9 in Figure l. Cathode ll may be connected with shunt 59 through the contacts of a circuit breaker 6|, auxiliary contacts 62 then preferably being provided on circuit breaker 6| to disconnect the coil of regulator 36 when circuit breaker 6| is opened.

In the present embodiment, the parallel circuits are constituted respectively by winding 41 with device I6 and by winding 55 with device 56. Such circuits may inherently tend to maintain the currents flowing therethrough at equal or at different values, and such values may be in a constant or in a variable ratio depending upon the no-load voltages of windings 41 and 55 and upon the impedances of the circuits and the methods of connection of the several elements thereof. Such circuits again include distinct discharge controlling means consisting of control electrodes such as 23 and 24 which are energized at recurring potentials from line I, 8 and transformers 48 and 58. Regulator 36 has no action on the energization of the control electrodes of device 56 and only controls the energization of the control electrodes of device l6. Regulator 38 is no longer responsive to the magnitude of the current flowing through the system but is re sponsive to the magnitude of the output voltage of the system. Circuit breaker 6| is provided for opening the circuit of device l6 if so desired and the contacts thereof render regulator 36 inoperative when only device 56 is being used. It will be understood that the connections of device 56 with conductor 8 and with line 6 may also be effected through suitable circuit breakers to permit interruption of such connections. If more than two devices are to be connected in parallel, each device will be provided with means for energizing the control electrodes thereof and with a regulator in a manner entirely similar to that provided for device 56.

In operation, line 6 being energized and circuit breakers 5| and 6| being closed, devices l6 and '56 carry currents of magnitudes having a ratio determined by the no-load voltages of windings 4'! and 55 and by the impedances of the circuits and the methods of connection of the The neutral point of the secondary several elements thereof. In the present embodiment, regulator 38, being energized in response to the magnitude of the voltage of line I, 8, controls the operation of devices I6 and 56 in such a manner as to maintain the voltage of line I, 8 at a predetermined value. Such operation is otherwise similar to that described with respect to the embodiment illustrated in Figure 1. If the distribution of current between devices I6 and 56 is obtained in the desired manner, regulator 36 remains in the position shown. If, for any reason, the current flowing through device I6 is greater than desired relative to the current flowing through device 56, regulator 36 receives, from shunt 59, a voltage which causes such regulator to move the variable tap of rheostat 32 to increase the amount of such rheostat inserted in the circuit thereof. Such action causes the direct current voltage component impressed on winding 49 to increase thereby reducing the flow of current through device I6. Such action continues until the desired proportion between the currents through devices I6 and 56 is reestablished, whereupon regulator 36 remains in the position reached thereby. In the present embodiment, the flow of current through device 56 is not directly controlled by regulator 36 but, when the flow of current through device I6 is regulated by regulator 36, the flow of current through device 56 automatically varies in an opposite direction because the total flow of current through the device is determined by the load connected with line I, 8. The action of regulator 36 will generally cause the average voltage of line I, 8 to depart from the desired value, and such voltage is then restored to the desired value by regulator 38.

If it is desired to utilize only device 56 for the conversion of current, circuit breaker BI is opened thereby interrupting the flow of current through device I6. Regulator 36 then becomes superfluous and is rendered inoperative by opening of auxiliary contacts 62 of circuit breaker 6I. Under such conditions, it will generally be desired to entirely disconnect device I6 from line 6 by means of circuit breaker and circuit breaker 53 then automatically disconnects transformer 48 from line 6 and from line I, 8.

In the embodiment illustrated in Figure 3, the current is converted by means of a single electron discharge device 63 provided with twelve anodes and receiving current from line 6 through a transformer 64. Transformer 64 is provided with winding I6 as a primary winding and with four star connected secondary windings 66, 61, 68 and 69 constituting a 12-phase system. The neutral points of windings 66, 61, 68 and 69 are connected with conductor I through interphase transformer I8 and through two more interphase transformers II and I2. The control electrodes of device 63 are represented as receiving only alternating voltages from a phase shifter I3 connected with line 6. Phase shifter I3 may be constructed similarly to a wound rotor induction motor, and the armature thereof is prevented from rotating by means of a spring I4. The relative position of the armature and of the stator of the phase shifter may be adjusted by a torque motor I6 having the armature thereof energized at the voltage of line I, 8 through rheostat 4I and having the field thereof energized in response to the magnitude of the current flowing through conductor I by means of a shunt TI.

The armature of phase shifter I3 supplies current to the primary windings of two control transformers I8 and I9 having the windings thereof so connected as to supply 12-phase currents to the control electrodes of device 63. For this purpose, the secondary windings of transformers IB and I9 are each constituted of two 3- phase windings severally energizing the control electrodes associated with the anodes receiving current from windings 66, 61, 68 and 69 respectively. The control electrodes associated with the anodes supplied from winding 66 are directly connected with one secondary winding of transformer I8. The remaining control electrodes are connected with transformers I6 and I9 through phase shifters BI, 82 and 83. The position of the armature of phase shifter 8| may be adjusted by means of a reversible motor 84 which may be energized from a battery 96 through a polarized relay 86 to cause rotation thereof in the one or in the other direction. The operating coil of relay 86 is connected through a reactor 81 across the terminals of inter-phase transformer II in a manner similar to the connection of the coil of regulator 36 with shunt I9 in Figure l. The operation of phase shifter 82 is similarly controlled by a motor 88 and a relay 89 connected across the terminals of interphase transformer I8 through a reactor 9|, and the operation of phase shifter 83 is controlled by means of a rotor 92 and of a relay 93 connected across the terminals of interphase transformer I2 through a reactor 94.

As a result of the above described connections, windings 66, 61, E8 and 69, together with the connections thereof with the interphase transformers and with the anodes of device 63, constitute electrically distinct circuits tending to maintain therethrough flow of current of equal values and having equal maximum values. Phase shifters BI, 82 and 83, which are operated in response to the ratios of the currents flowing through the above circuits, maintain the flow of such currents equal independently of any operating conditions tending to disturb such equality. The phase shifters are operated in response to the flow of current through the circuits taken in pairs and are one less in number than the number of such circuits. The control electrodes are energized by means comprising line 6 as a source of recurring potentials and of phase shifters I3, 8|, 82 and 83 and transformers I8 and I9. Phase shifter I3 and motor I6 operate in response to the flow of current through device 63, and in response to the output voltage of line I, 8 and therefore in response to the amount of energy flowing through the system to regulate the flow of current therethrough.

In operation, assuming the system to be connected as shown and line I6 to be energized, if the flow of current through windings 66, 67, 68 and 69 are equal, phase shifters BI, 82 and 63 remain in a position such that the control electrodes of device 63 are energized at voltages of uniform phase intervals. If the currents through windings 66 and 61 differ in value, a direct current voltage component appears across the terminals of interphase transformers II and is impressed on the coil of relay 86. Relay 86 closes the one or the other contact thereof and energizes motor 84 to cause rotation thereof in the one or in the other direction thus adjusts phase shift er 8| to advance or retard the voltages delivered thereby. The flow of current through winding 61 is thereby increased or reduced until such current is brought to the value of the current flowing through winding 66. When such equality of Ill) 2,038,505 the two currents is obtained, the direct current voltage component across interphase transformer 1| disappears, relay 86 returns to the position shown, and motor 84 and phase shifter 8| remain in the position reached thereby. In a similar manner, if the currents flowing in windings 68 and 69 diifer, a direct current voltage component appears across the terminals of interphase transformer l2 and phase shifter 83 controls the flow of current through winding 69 to bring such current to the value of the current through winding 68. If the total current flowing through windings 58 and 61 differs from the total current flowing through windings 68 and 69, a direct current voltage component appears across the terminals of interphase transformer l8 causing phase shifter 82 to operate to control the flow of current through winding 68 until the currents flowing through the two portions of interphase transformer l8 become equal. Such operation of phase shifter 32 may cause the currents flowing through winding 68 and 69 again to become unequal, and such action is then corrected by phase shifter 83 in the manner described above. If the energy output of the system is greater than the desired value, motor 16 shifts the position of the armature of phase shifter '53 in a manner such as to retard the phase of the voltages applied on all the control electrodes of device 63 to reduce the output of such device, such action continuing until such output is reduced to the desired value, whereupon phase shifter 13 remains in the position reached thereby. If the output of the system is below the desired value, spring M returns the armature of phase shifter l3 toward the original position thereof to increase the output of the systern to the desired value.

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 to secure by Letters Patent:

1. In a system for controlling the flow of electric current, electron discharge means comprising a plurality of electrically distinct circuits tending to cause flow therethrough of currents of magnitudes in ratios of predetermined values, and means responsive to the ratios of the magnitude of the currents taken in pairs for maintaining the ratios of the magnitudes of the currents of the respective pairs at the predetermined values.

2. In a system for controlling the flow of electric current, electron discharge means comprising a plurality of electrically distinct circuits each including distinct discharge controlling means, and means responsive to the ratios of the magnitude of the currents taken in pairs and control ling the second said means to maintain the ratios of the magnitudes of the currents of the respective pairs at predetermined Values.

3. In a system for controlling the flow of electric current, electron discharge means having a plurality of electrically distinct circuits each comprising an anode and an associated control electrode, means for energizing said control electrodes, and means responsive to the ratio of the magnitudes of the currents flowing through said circuits taken in pairs and controlling the operation of the second said means to maintain the ratios of the magnitude of the currents of the respective pairs at predetermined values.

4. In a system for controlling the flow of electric current, electron discharge means having a pair of electrically distinct circuits each comprising an anode and an associated control electrode, means including a source of potentials for impressing recurring potentials on each said control electrodes, and means responsive to the ratio of the magnitudes of the currents flowing through said circuits for controlling the times of application of said recurring potentials to each of said control electrodes in opposite manner to maintain the ratio of the magnitudes of the currents flowing through said circuits at a predetermined value.

5. in a system for controlling the flow of electric current, electron discharge means having a pair of electrically distinct circuits each comprising an anode and an associated control electrode, means including a source of potentials for impressing recurring potentials on each said control electrodes, and means responsive to the ratio of the magnitudes of the currents flowing through said circuits for controlling the times of application of said recurring potentials to one of said control electrodes to maintain the ratio of the magnitudes of the currents flowing through said circuits at a predetermined value.

6. In a system for controlling the flow of electric current, electron discharge means having a plurality of electrically distinct circuits each comprising an anode and an associated control electrode, means including a source of potentials for impressing recurring potentials on each said control electrodes, and means one less in number than the number of said circuits and severally responsive to the ratios of the magnitudes of the current flowing through said circuits taken in pairs for controlling the times of application of said recurring potentials to all but one of said control electrodes to maintain the ratio of the magnitudes of the currents flowing through said circuits at a predetermined value.

'7. In a system for controlling the flow of electric current, electron discharge means comprising a plurality of electrically distinct circuits, means responsive to the flow of current through said circuits for maintaining the ratios of the magnitude of the currents in said circuits at predetermined values under all operating conditions of said system, and means responsive to an operating condition of said discharge means and cooperating With the second said means to control the operation of said discharge means.

8. In a system for controlling the flow of electric current, electron discharge means comprising a plurality of electrically distinct circuits, means responsive to the flow of current through said circuits for maintaining the ratios of the magnitude of the currents in said circuits at predetermined values under all operating conditions of said system, and means responsive to the magnitude of the output voltage; of said discharge means and cooperating with the second said means to control the flow of current through said discharge means.

9. In a system for controlling the flow of elec tric current, electron discharge means comp-rising a plurality of electrically distinct circuits, means responsive to the flow of current through said circuits for maintaining the ratios of the magnitude of the currents in said circuits at predetermined values under all operating conditions of said system, and means responsive to the magnitude of the. current flowing through said discharge means and cooperating with the second said means to control the flow of current through said discharge means.

10. In a system for controlling the flow of electric current, electron discharge means comprising a plurality of electrically distinct circuits, means responsive to the flow of current through said circuits for maintaining the ratios of the magnitude of the currents in said circuits at predetermined values under all operating conditions of said system, and means responsive to the magnitude of the energy flow through said means cooperating with the second said means to control the flow of current through said discharge means.

11. In a system for controlling the flow of electric current, electron discharge means comprising a plurality of electrically distinct circuits, means responsive to the flow of current through said circuits for maintaining the ratios of the magnitude of the currents in said circuits at predetermined values under all operating conditions of said system, means for opening one of said circuits, and means controlled by the last said means to cause the second said means to cease to respond to the current conditions in said one of said circuits.

12. In a system for controlling the flow of electric current, electron discharge means comprising a plurality of electrically distinct circuits, discharge controlling means for said discharge means, means responsive to the flow of current through said circuits and controlling the second said means to maintain the ratios of the. magnitude of the currents in said circuits at predetermined values under all operating conditions of said system, means responsive to an operating condition of said discharge means and cooperating with the third said means to control the operation of said discharge means, and means responsive to the occurrence of abnormal conditions in said system for controlling the second said means and overcoming the action of the last said two means for causing interruption of the flow of current through said system.

13. In a system for controlling the flow of electric current, a source of alternating current, electron discharge means having a plurality of electrically distinct circuits each comprising a winding connected with said source and with an anode and a control electrode, a transformer having a winding thereof connected with said source and with the control electrodes to impress recurring potentials on each of the control electrodes,

a direct current line supplied by said discharge means, and means responsive to the ratio of the magnitudes of the currents flowing through the circuits to apply a potential from said direct current line to said transformer for controlling the action of the control electrodes to maintain the predetermined ratios of current flow.

14. In a system for controlling the flow of electric current, a source of alternating current, electron discharge means having a' plurality of electrically distinct circuits each comprising a winding connected with said source and with an anode and a control electrode, a transformer having a winding thereof connected with said source and N with the control electrodes to impress recurring potentials on each of the control electrodes, a direct current line supplied by said discharge means, means responsive to the ratio of the magnitudes of the currents flowing through the circuits to apply a potential from said direct ourrent line to said transformer for controlling the action of the control electrodes to maintain the predetermined ratios of current flow, and a relay responsive to abnormal conditions in said discharge device to disconnect said means from said transformer.

15. In a system for controlling the flow of electric current, a source of alternating current, electron discharge means having a plurality of elec* trically distinct circuits each comprising a winding connected With said source and with an anode and a control electrode, a transformer having a winding thereof connected with said source and With the control electrodes to impress recurring potentials on each of the control electrodes, a direct current line supplied by said discharge means, means responsive to the ratio of the magnitudes of the currents flowing through the circuits to apply a potential from said direct current line to said transformer for controlling the action of the control electrodes to maintain the predetermined ratios of current flow, a capacitor connected With said direct current line, and a relay responsive to abnormal conditions in said discharge device to disconnect said means and to connect said capacitor to said transformer to cause cessation of flow of current through the system.

16. In a system for controlling the flow of electric current, a source of alternating current, elec tron discharge means having a plurality of electrically distinct circuits each comprising a winding connected with said source and with an anode and a control electrode, a transformer having a winding thereof connected with said source and with the control electrodes to impress recurring potentials on each of the control electrodes, a direct current line supplied by said discharge means, a rheostat variable in response to the ratio of the magnitude of the currents flowing through the circuits to apply a potential from said direct current line to said transformer for controlling the action of the control electrodes to maintain the predetermined ratios of current flow, and a rheostat variable in response to variations in current magnitude in said direct current line and coopcrating with the first said rheostat to maintain a constant current flow through the circuits in the predetermined ratio.

17. In a system for controlling the flow of electric current, a source of alternating current, electron discharge means having a plurality of elec trically distinct circuits each comprising a winding connected with said source and with an anode and a control electrode, a transformer having a winding thereof connected with said source and with the control electrodes to impress recurring potentials on each of the control electrodes, a direct current line supplied by said discharge means, a rheostat variable in response to the ratio of the magnitude of the currents flowing through the circuits to apply a potential from said direct current line to said transformer for controlling the action of the control electrodes to maintain the predetermined ratios of current flow, and a rheostat variable in response to variations in voltage magnitude in said direct current line and cooperating with the first said rheostat to maintain a constant current flow through the circuits in the predetermined ratio.

18. In a system for controlling the flow of electric current, a source of alternating current, electron discharge means having a plurality of electrically distinct circuits each comprising a winding connected withsaid source and with an anode and a control electrode, a transformer havcharge means, and means responsive to the voltage of said direct current line for controlling the action of the control electrodes in one of the circuits upon interruption of the other of the circuits.

19. In a system for controlling the flow of electric current, a source of alternating current, electron discharge means having a plurality of electrically distinct circuits each comprising a winding connected with said source and with an anode and a control electrode, a transformer having a winding thereof connected with said source and with the control electrodes to impress recurring potentials on each of the control electrodes, a direct current line supplied by said discharge means, means for interrupting one of the circuits, and means responsive to the voltage of said direct current line for controlling the action of the control electrodes in one of the circuits upon interruption of the other of the circuits.

20. In a system for controlling the flow of electric current, a source of alternating current, electron discharge means having a plurality of electrically distinct circuits each comprising a winding connected with said source and with an anode and a control electrode, a transformer having a winding thereof connected with said source and with the control electrodes to impress recurring potentials on each of the control electrodes, a direct current line supplied by said discharge means, and means responsive to the magnitude of the total energy flow from all of said electrically distinct circuits through said direct current line to vary the phase of the potentials applied to the control electrodes by said transformer.

21. In a system for controlling the flow of electric current, a source of alternating current, electron discharge means having a plurality of electrically distinct circuits each comprising a winding connected with said source and with an anode and a control electrode, a transformer having a winding thereof connected with said source and with the control electrodes to impress recurring potentials on each of the control electrodes, a direct current line supplied by said discharge means, means responsive to the magnitude of the energy flow through said direct current line to vary the phase of the potentials applied to the control electrodes by said transformer, and means responsive to the ratios of the magnitude of the current iiow through said circuits to cooperate with the first said means in varying the phase of the potentials applied to the control electrodes by said transformer.

22. In a system for controlling the flow of electric current, a source of alternating current, electron discharge means having a plurality of electrically distinct circuits each comprising a winding connected with said source and with an anode and a control electrode, a transformer having a winding thereof connected with said source and with the control electrodes to impress recurring potentials on each of the control electrodes, a direct current line supplied by said discharge means, means for varying the phase of the potentials applied to the control electrodes by said transformer, and relays responsive to the ratios of the magnitudes of the currents flowing through the circuits for controlling the operation of said phase varying means.

HAROLD WINOGRAD.

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