US2239289A

US2239289A - Discharge apparatus

Info

Publication number: US2239289A
Application number: US148616A
Authority: US
Inventors: William M Goodhue; Jr Roy B Power
Original assignee: Individual
Current assignee: Individual
Priority date: 1937-06-16
Filing date: 1937-06-16
Publication date: 1941-04-22
Anticipated expiration: 1958-04-22

Description

April "19.41- w. M. COODHUE ETAL DISCHARGE APPARATUS Filed June 16, 1937 5 Sheets-Sheet 1 M v 30 75 2 V 3/ 3/ v 35 A 36 Q 55 II as M M W] WITNESSES: INVENTORS g 0%. W/m'am M. Good/we A Roy 5.850 W61; Jr.

ATTORNEY April 2, 1941. w. M. eo'onnus EIAL 2,239,289

DI SCHARGE APPARATUS Filed June 16, 1937 5 Sheets-Sheet 2 WITNESSES: INVENTORS W 6? Mm W/l/fam M Good/we 6e fiay 15. Pom e1; Jr: 7% W BY ATTORNE Patented Apr. 22, 1941 DISCHARGE APPARATUS William M. Goodhue, Boston, Mass., and Roy B.-

Power, In, Manhattan, Kans.

Applicationjune 16, 1937, Serial No. 148,616

26 Claims.

Our invention relates to electric discharge apparatus and has particular relation to power supply apparatus. A de cription of our-invention, together with experimental data is published beginning on page 1200 of the November 1936, issue of Electrical Engineering.

It is an object of our invention to provide apparatus that shall operate as its own automatic regulator for supplying power from a source of electrical energy to a load.

Another object of our invention is to provide power supply apparatus that shall incorporate a regulator which functions to maintain the potential across the loadindependent 01' the potential of the source.

Still another object of our invention is to provide power supply apparatus that shall automatically regulate itself to maintain the load potential constant in spite of variations in the source potential.

A further object of our invention is to provide power supply apparatus that shall automatically regulate itself to maintain the load potential constant regardless of variations in-the load current.

A still further object of our invention is to provide power supply apparatus by the operation of which it shall be possible to adjust the compounding to any desired condition.

An additional object of our invention is to provide power supply apparatus that shall automatically regulate itself to maintain the load current constant in spite of variations in the source potential. 1

A further additional object of our invention is to provide power supply apparatus that shall automatically regulate itself to maintain the load potential substantially constant in spite o1 variations in the load current.

Another additional object of our invention is to provide a power supply apparatus incorporating grid controlled electric discharge paths wherein the discharge paths shall function to provide automatic regulation.

A more specific object of our invention is to provide a power rectifier that shall operate as its own automatic regulator. ,I

An additional specific object of our invention is to provide apparatus of the type that shall opcrate as its own automatic regulator for rectifying the power supplied by a polyphae source to a direct current load.

Another specific object of our invention is to provide a power supply system in which regulation shall be attained without the use of movable contacts.

An ancillary object of our invention is to provide a highly tractable system for supplying power to an electro-dynamic machine.

Another ancillary object of our invention is to provide for an electric motor a power supply system of such character that the operation of the electric motor shall be adjustable with facility.

, A further ancillary object of our invention is to provide for an electric motor a power supply system of such character that the speed of the motor shall be controlled by controlling a current of small magnitude. 7

A still further ancillary object of our invention is to provide a highly tractable power supply system for a direct current motor.

More generally stated, it is an object of our invention to provide a power supply system that shall be automatically regulable and adjustable, so that its operation may be made to conform to a wide variety of desired conditions. I

According to our invention, we interpose one or more discharge devices or discharge paths, each of which has a control electrode and a plurality of principal electrodes and a gaseous medium, between the source and the load. A constant potential of polarity such as to energize the discharge device is impressed between the control electrode and one of the principal electrodes. The magnitude of this potential is selected so large, compared to the critical control potential of the discharge device, that random variations which may arise in the magnitude of the critical control potential of any one discharge device or between the critical control potentials of the different discharge devices are substantially masked.

The critical control potential is defined as the potential between the control electrode and a principal electrode of a discharge device at which the discharge device passes from a deenergized to an energized condition for a given potential between the principal electrodes. For control potentials more negative than the critical control potential, the discharge device if initially deemergized remains deenergized, for more positive control potentials it is energized.

0n the constant potential another potential dependent upon and, in. specific cases, proportional to the load potential is superimposed. The latter potential is of polarity opposite to the former potential and of such magnitude that the critical control potential is only at times exceeded.

Specifically when the source of electrical energy whereby the load is to be supplied is of the polyphase type, a discharge device is inserted between each phase and the load and the aforementioned potentials are impressed between the control electrode and a principal electrode of each of the discharge devices. In this case the total control potential comprising the sum of the two potentials mentioned above rises above the critieal control potential periodically. We have found that when properly adjusted, a system of this type operates to maintain the load potential to the'former potential.

constant in spite of variations in the source poa tential.

Under certain conditions, it is desirable that the load potential should be maintained constant independently of variations in the load current. At times the more general problem of compounding is involved. These problems may be solved at the same time by superimposing on the two potentials above mentioned a potential proportional to the load current. This potential may be derived by inserting current transformers in the source and applying the rectified output or these transformers to the control circuits of the discharge devices.

The foregoing procedure may be designated'as current compounding. We have also found that potential compounding may be of considerable utility in maintaining the load current or load potential or both constant independentlyof variations in source potential and the load potential constant independently of variations in The electro-dynamic machine is supplied from a source through discharge devices of the gaseous type. In the control circuits of the discharge devices, a constant potential of magnitude large compared to the critical control potential and of vices is impressed. On this potential another p tential derived from current transformers in the power source and essentially proportional to the current through the machine is superimposed. The latter potential is of opposite polarity We have found that a machine supplied in this manner operates at a substantially constant current independently of variations in potential as long as the potential v of the source is sumcient to supply the potential of the machine, and ate. substantially constant potential independently of the variations in. current when the potential of the source is insuffi cient to supply the potential of the machine. During starting, therefore, an electro-dynamic machine supplied in this manner operates in the first region mentioned above, while during its normal functioning it operates in the other region mentioned above. The system discussed above may be applied with particular advantage where a direct-current motor having independent excitation is supplied from a polyphase alternating source. Such a motor may be controlled by controlling i'ts excitation and this object may be accomplished by varying the small current delivered by a photo-electric cell.

The novel features that we consider charactcristic of our invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and its method of operation, together with additional objects and advantages thereof, will best a polarity such as to energize the discharge deaaeaaee specific embodiments when read in connection with the accompanying drawings, in which:

system such as is disclosed in Fig. 3 under certain circumstances; I Fig. 5 is a diagrammatic view of a modification of our invention involving the application of the principles illustrated in Fig. 4 to an electrodynamic machine;

Fig. 6 is a diagrammatic view showing a modification of our invention as disclosed in Fig. 5;

Fig. 'l is a graph showing further features of the modification shown in Fig. 3;

d is a diagrammatic view of a modification of our invention involving both current and po tential compounding, and;

Fig. 9 is a diagrammatic view of a modification of our invention as it is applied to a double three-phase rectifier system.

The apparatus shown in Fig. 1 comprises a polyphase source ii, the output of which is connected to a suitable supply transformer l3. The secondary it: of the transformer 53 is connected in star and supplies a load ll through a plurality of discharge devices l9, 2! and 23, a discharge device being interposed between each of the windings 25, 2'! and 28 of the secondary and one terminal of the load. The other terminal of the load I! is connected to the neutral point 29 of the secondary l5 through a reactor 30. Each of the discharge devices l9, 2i and 23 comprises an anode 3!, a hot cathode 33, a control electrode 35 and a suitable ionizing medium. The ionizing medium may be provided by an inert gas such as argon or neon at a pressure of 2 or 3 millimeters of mercury or it may be the vapor of a mercury globule located within the container of the discharge device.

,Each of the discharge devices I9, 2| and 23 has a so-called arc-like characteristic. One aspoet of such a characteristic is abruptness of response. For a given anode-cathode potential,

, the device is substantially nonconductive as long as the control-electrode-cathode potential is more negative than a potential which we have above designated as the critical control potential. When the control-electrode-cathode potential becomes more positive than the critical control potential, the discharge device becomes conductive and passes current, the magnitude of which is independent of the extent to which the critical conbe understood from the following description of trol potential is exceeded. Another aspect of the arc-like characteristic is the so-called lock-in feature. A discharge device of the arc-like type when once rendered conductive continues to re main conductive regardless of the control electrode potential as long as the anode-cathode potential is sumcient to support the discharge.

As regards the foregoing comments, it is to be noted that they represent the. general situation. Discharge devices which are responsive to variations in the control potential have been developed andwhere a system including such a discharge device involves the practice of our invention, we intend that it shall 'be regarded as lying within the scope thereof. 'It is to be noted, moreover, that while in Fig. 1 and in the other views our invention is illustrated as applied to -hot cathode discharge devices l3, 2| and 23, it

may also be utilized with discharge devices in which cathodes of other types are utilized. For example, the hot cathode 33 may be replaced by a mercury pool or a deposit of lead or cadmium or any other metal which is either continuously maintained energized by a keep-alive electrode or is reenergized at suitable intervals by a makealive electrode operating somewhat as a control electrode." The make-alive electrode may be external to the container of the discharge device or it may be internal and in contact with the pool or deposit as in the Ignitron tubes. The hot cathode 33 may also be replaced by a so-called cold cathode as in the Westinghouse cold cathode Grid Glow tube designated as KU-618 in the art. Apparatus incorporating discharge devices of the type just mentioned in lieu of the devices l9, 2| and 23 and involving the general features of our invention are within the scope thereof.

The control electrodes 35 of the discharge devices |9, 2| and 23 are connected through

suitable resistors

31, 33 and 4| to a common point 43. The cathodes 33 of the discharge devices are also connected to a common point 45 which is the same electrically as the positive terminal ot the load l1. Between the common control-electrode point 43 and the common cathode point 45 a composite control potential is impressed. One component of this potential is applied by a directcurrent source such as a battery 41. The positive terminal of the source 41 is connected to the point 43 and its negative terminal is connected to the variable tap 49 of a potentiometer 5| connected across the load |I.' The source 41 is of a magnitude that is large compared to the critical control potential of the discharge devices l9, 2| and 23 and the relationship in the magnitude of the quantities is such that the random variations in critical control potential which arise in a single discharge device is, 2| or 23 or between the different discharge devices are substantially masked.

The other component of the control potential is provided between the movable tap 43 of the potentiometer 5| and the cathode common point 45. The latter potential is of such magnitude and polarity that the total potential exceeds the critical control potential periodically at intervals depending on the magnitude of the power which is to be supplied to the load H. I I

The system operates to automatically maintain the potential supplied to the load i1 independent of variations in the potential of the source The functioning of the apparatus is illustrated in Fig. 2. In curve A of this view, the potential difierence between the cathode 33 of an energized discharge device and the neutral point 23 is plotted as a function of time. It will be noted that inasmuch as the potential drop through the.

discharge devices it, 2| and 23, when they are energized, is comparatively small, this plot represents substantially the potentials supplied between the neutral point 29 and the terminals of the

secondary windings

25, 27 and 29 oi the tranw former i3.

Potential is plotted vertically and time hori zontally. The abscissa represents the potential of the neutral point 25.. The heavy line portions of the full line half waves in curve A represent a normal condition of operation. The heavy line portions 59 oil the broken line half waves hi represent a hypothetical condition which exists when an increase occurs in the potential of the source it corresponding to the difference between the heights of the'broken line curves 55 and the full line loops 59.

- an essential feature of our invention arises.

When the apparatus is in operation, the discharge device |9, 2l or 23, corresponding to each phase, is conductive until the discharge device corresponding to the subsequent phase is energized. The

loop portions

53 and 59 represent the conductive conditions of the successive discharge devices when the source potential corresponds respectivelyto loops 55-and'6i. During a short transition period the discharge device (say l9) which is being extinguished and the discharge device (say 2|) which is being energized are both conductive simultaneously. The transition interval is known as the commutation period and is represented in curve A by the two

vertical lines

63 and 65 which are separated by a substantially horizontal line 61 between each pair of portions 53 of loops 55 and by corresponding lines 69, H and 13 for loops 5|.

The successive discharge devices It, 2| and 23 are, of course, not energized at random. Each discharge device is in its turn rendered conductive at the instance when the total control potential exceeds the critical control potential. It is from the timing of the occurrence of this event that It happens that for the potentials represented by the broken line loops 6|, this instant occurs later than for the potentials represented by the full line loops 55 and the timing is such that the load potential remains constant. This aspect of our invention can be. seen from the other curves shown in Fig. 2.

In curve B the potential between the cathodes 33 and the conductor 15 from, the load I! to the reactor 30 is plotted as a function of time. Again potential is plotted vertically and time horizontally. The abscissa now, however, corresponds to the potential of conductor 15. The full line loops I1 correspondto the full line loops 53 of curve A and the broken line loops I9 correspond to the broken line loops Bl of curve A. The potential variations are not as irregular as those represented in curve A by reason of the smoothing effect of the reactor 3|), and the corresponding loops '1! and 19 are, therefore, not so jagged as the corresponding loop portions 53-53-t'|-65 and 53-99-l3-l|.

Since the cathodes 33 are connected to a common point 45, the waves TI and 19 in curve B correspond to the potential difference between the point 45 and the conductor 15 and, therefore, between the lower terminal and the upper terminal of the potentiometer 5|. The actual potential impressed between the control electrodes and the cathodes 33 ofthe discharge devices it, ill and 23 includes a potential derived from poten-= tiometer iii and may be derived from curve B. It is illustrated in curve 0. Here potential is again plotted vertically and time horizontally, but the abscissa corresponds to the potential oi the cathodes The horizontal line i'li above the abscissa corresponds to the potential supp' ed by the battery 62' in the control circuit. .Il' line loops and the broken line loops medium weight at considerable distance hell the abscissa correspond, to the potential. di between the movable oi the pate-mic 5t and the cathodes The horizontal i just below the cissa correwonds to the control potent-m o). the discharge devices. heavy full line and broken line loops an correspond to t e sum of the potential. d from the potentiometer and the intersectthe critical control potential line at

nodal points

93 and 95, respectively, which correspond to the transition from one energized discharge device l9, 2! or 123 to the subsequent one.

The curves of Fig. 2' represent the natural operation of the apparatus. Consider the full line heavy loop 89 on the extreme left of curve C, assuming at the same time that the potential applied to the discharge devices [19, 2|] and 23 corresponds to half wave 55a. In correspondence with the left-hand loop $39, the control potential impressed on the discharge devices rises from a value substantially below the critical potential to the value of the critical potential represented by the second nodal point 93 from the left. During all this time one of thedischarge devices (say iii) which corresponds to the first phase has been energized and the current transmitted therethrough has swelled and decreased in accordance with loop portion 5a. At the instant corresponding to the second nodal point from the left, the discharge device (say 25) corresponding to the second phase 2? is energized, since the anode cathode potential applied to it is greater than the anode-cathode potential applied to the first phase. The corresponding control potential now becomes more negative, as illustrated, by the central heavy full line wave 38 as the current 'fiow through the load increases, then it becomes more positive as the current decreases, until the 111 stant corresponding to the third nodal point 33. Here the discharge device (say 23) corresponding to phase 28, is energized and the above procedure again repeated, producing the condition represented by the right-hand loop 89. The energize.- tion of device 23 is followed by the energization of device I 9, and the above described steps are thus repeated until the current flow is for some reason interrupted or changed. If a condition corresponding to the broken line loops BI exists, the critical control potential line 81 will be out at a later instant as is illustrated by the broken line loops 9i and the nodal points 95 and the ignition of thedischarge devices will be correspondingly delayed. It is apparent that the load potential will now assume avalue smaller than would be expected from the increase in source potential and in actual practice we have found that the, load potential remains substantially constant.

While the fact thatthe load potential is constant in spite of variations-in the source potential has been demonstrated by us conclusively by experiment, it may also be demonstrated mathematically.

Let

E=the potential of the battery 4i, V=the load potential, e =the control potential,

a=8 fraction represented by the setting of the potentiometer 5|,

then at the nodal points: i

eg=EdV fl of the order of 12 volts. In one application of our invention we have utilized discharge devices of the type that have a critical control potential oi plus 12 volts, and we have used a battery potential of 90 volts. It is to be noted that for a critical control potential of plus 12 volts, the critical control potential line 931? of curve C would be above rather than below the time axis.

Where the load current is to he maintained independent of variations in the load poten tial or is to vary in a predetermined manner with the load potential, the simple arrangement shown in Fig. i does not sufiice and the arrangement shown in Fig. 3 should be utilized. In the modification shown in Fig. 3, the elements of Fig. l are incorporated and in addition a potential substantially proportional to the load current is superimposed on the battery potential and the potentiometer potential. The latter potential is derived from the source it through current transformers 97!, 951 and ifll coupled to the conductors M3, 565, and till, respectively, from the source to the primary I99 of the, supply transformer it. The transformers ill, 99 and till supply a variable resistor Hi through a plurality of rectifiers H3, H5 and Ill.

A variable capacitor M9 is connected between the movable tap 02!] of the resistor iii and one of its terminals. The capacitor H9 operates to smooth out the potential supplied by the transformers 91,

' 99 and I8! and may on occasions be omitted entirely.

The movable tap 62B of the resistor I II and its left-hand terminal are connected in the control circuit of the discharge devices I9, 2! and 23 through a suitable reversing switch I23, so that the potential derived from the resistor may have either a-positive or a negative polarity in the control circuit depending on the position of the switch. The potential impressed by reason of the current flow through the resistor III is to a fair approximation proportional to the load current, and thus operates to provide the necessary compensation for the variations in the current. For

'proper adjustment of the resistor l I I and the reversin switch I23, the load potential may be rendered substantially constant in spite of variations in the load current. This condition is designated in the art as net compounding. Difierential compounding or cumulative compounding may be attained by properly raising the magnitude of the potential supplied by the resistor HI and closing the reversing switch I23 so that the potential supplied is of the proper polarity. Thus it is seen that any desired characteristic for the supply'of power to the load I1 may be attained.

Using an arrangement such as is shown in Fig. 3, but with the movable tap 49 of the potentiometer SI connected to the common cathode point 45, we have made measurements of the directcurrent load potential as a. function of the directcurrent load current for various magnitudes o! the resistor III through which the compounding potential is supplied. Certain of the results of these measurements are shown in Fig. 4, in which the direct-current load potential is plotted as a function of the direct-current load current. Potenltial is plotted vertically and current horizon- Three curves I25, I21 and I29 are reproduced, the curve I25 on the extreme left representing a large value of resistance, the center curve I21 9.

' medium value of resistance, and the curve I29 on 1 Fig. 3 with the potentiometer potential zero as a rather interesting characteristic. Up to a ertain potential 01 the order of 280 volts, the curent is substantially constant as the potential is icreased and the condition is represented by subtantially vertical lines I31, I33 and I35. Above his potentialthe potential is substantially contant as the current decreases and the condition 5 represented by substantially horizontal lines 37, I38 and MI. The latter portion of the curves epresents the condition which exists in the sysem when at a given current the load potential ecomes so large that the source potential is inufdcient to maintain the current. The lines I3I, 33 and I35 represent the condition when for a :iven current the load potential is of such magniude that the source potential is sufficient to naintain the current.

The property of the apparatus that is illus- ;rated in Fig. 4 may with advantage be utilized .n a system such as is shown in Fig. 5. In the nodification shown in this view, the armature I43 of a direct-current motor I45 with independent excitation I41, is supplied from the out- I out of a system such as is shown in Fig. 3. The

force) increases. The potential continues to increase with the current constant until the motor I45 attains its operating speed.- .At this point the system operates along the lines I31, I39 or I, and the load potential becomes constant; that is to say, the back electromotive force of the motor and its speed become substantially constant.

Accordingly, an analysis of the curves I25, I27! and I29 as they applyto the system shown in Fig. 5 reveals that during the starting period the current drawn by the motor M5 is substantially constant, and, therefore, the torque is constant. During the operating period, the potential is substantially constant and although the current may vary, the speed remains substantially constant. In a system such as is shown in Fig. 5, starting equipment is eliminated and the torque may be high because normal direct-current motors such as I45 may be used at potentials for armature of the motor is connected between the reactor and the common junction point 45 of the cathodes 33. The exciting winding 8 of the motor is supplied independently from the main source through an auxiliary transformer I5I '(or a source of any other type) and through an auxiliary discharge device 553. The latter may be a gaseous or a high vacuum tube having an anode I55, 2. hot cathode I51 and a control electrode I530: any other discharge device of the various types mentioned hereinabove. The discharge device I53 is controlled through a photo-electric cell I5! connectedbetween its control electrode I59 and itsanode 555. By varying the radiation impinging on the photo-electric cell I5I,'the potential impressed between the anode I55 and the control electrode I59 is varied and thus the excitation of the motor, and, accordingly, its speed is controlled.

In lieu of the resistor III and the reversing switch I23 of the apparatus shown in Fig. 3, an

auxiliary potentiometer I53 with a center tap I and a variable tap I61, which may be displaced on both sides of the center tap is utilized. By sliding the movable tap I61 from one side of the center tap I65 to the other, the polarity of the potential impressed from the current transformers may be varied. However, as a general rule, we prefer to operate with the potential supplied by the potentiometer I53 oi the opposite polarity as the potential supplied by the battery I".

It is seen that the energy consumed by the motor I may be controlled by shifting the movable tap of the potentiometer I83.

Depending upon the resistance of the auxiliary potentiometer I33 that is in the control circuit of the discharge devices I9, 2i and 23, the motor I55 has a. characteristic corresponding to one or the other of the curves I25, I2'I or I29, reproduced in Fig. 4. When power is first applied to the system, the'mctor begins to rotate and its speed gradually increases for an interval of time that may be designated as the starting period. During the starting period the system is operat- Ing along the lines I3I I33 or I35 and the motor draws constant current of a predetermined value, depending on the resistance in the control circuit, while the potential manifested at the terminals of the armature I43 (the peak electromotive which they are best adapted; The speed may be controlled by controlling the field excitation and this object may be accomplished by utilizing an element of such small space and power requirements as a photo-electric cell ISI. I

In accordance with the foregoing principles, the maximum permissible transient load torque is equal to the starting torque. The latter may be set by the operator with the potentiometer I53 in the control circuit, and as is the usual case, may be of from 1 to 3 times the normal torque. The starting current may be reduced at any time below the maximum permissible value by inserting a. resistor I55 in series with the potentiometer I53 as is illustrated in Fig. 5 for example. The resistor its in the modification shown in Fig. 6 may be connected in the circuit after the ,motor has started by asuitable two pole switch Ill. The movable contactor IIfibf the switch III is connectedto the movable tap Ifil of the auxiliary potentiometer I53, one pole H5 is connected to the control electrode common point t3 and the other pole IT! is connected to one terminal of the resistor I59, its other terminal being connected to the point 43.

In Fig. 7, the load current for a system, such as is shown in Fig. 3, is plotted as a function of the potential of the battery d1 for the condition in which the potential supplied by the main potentiometer 5i is zero. Current is plotted ver-' tically and potential horizontally. The upper curve I13 represents the variation in direct-current as a function oi the battery potential for a short circuit across the load terminals andthe lower curve Itl represents the function for a finite load II--speciflcally 58 ohms. The short circuit curve I13 is of particular interest. The current output varies continuously without any critical points from zero to a considerable value. This property of the apparatus which may be important in such applications as welding, for example, cannot be obtained with any other arrangement known to us than the one disclosed here. An ordinary phase shift controlled rectiher is critical to the phase adjustment when the loadis a short circuit. In such a case, the output current of the rectifier is small for certain degrees phase angle and attains full value for a variation of 2 0r 3 degrees in phase from this value.

It may be that other conditions of operation are desired than the ones discussed heretofore. For example, it may be'desired that the load current should remain constant independent of variations in the source potential. Another characteristic which is sometimes desired in practice is a load potential which is constant independent of variations in the load current. Both of these conditions may be attained by utilizing so-called potential compounding alone or in combination with current compounding.

An arrangement incorporating this feature is shown in Fig. 8. In addition to the potential derived from the current transformers 97], 99 and WE, the battery potential and the potentiometer potential, a potential is impressed in .the control circuit of the discharge devices which is derived from an auxiliary potential transformer M33. The transformer 583 is oi the ordinary delta-star type and supplies a second auxiliary potentiometer 885 through rectifiers it'll, 689 and tea. The

potentiometer E85 is provided with a variable tap 9% which is connected .to the common point oi .the control electrodes 35, one of its terminal taps is connected to the neutral point we of the secondary it'll of the auxiliary transformer i333 and the other to the poles B98 and 2M of the reversible switch it?! through which the potential derived from the current transformers 917, Qt and Hill is impressed in the control circuit. The potential derived from the potential transformer 883 is thus superimposed on the other potentials in the control circuit. If, as is the case at times. it is desirable that only potential compounding be utilized, the resistor iii supplied from the current transformers S1, 99 and Hill may be short circuitedby moving the movable tap to the upper terminal. However, in general, both current compounding and potential compounding is desirable, so that potential is supplied by both the current transformers and the auxiliary potential transformer. I

Our invention may also'be applied to a system in which two sets 263 and 205 of three discharge devices 20?, 239 and 2M and 263, M and M77, each are interposed between the load El and the source. In such a case a transformer 2H8, with a double Y secondary M9 is utilized and the discharged

devices

201, 2%, 22M, 283, M5 and it? are connected to the

windings

222i, 223, 225, 227?,

229 and 23! of the secondary. The potentials are supplied in the control circuits of the discharge devices in the same manner as in the single Y arrangement shown in the other views through potentiometer 5! with the variable tap 49 and the Our invention has been disclosed herein as.

applied to various systems. A number of changes can be made in these systems without departing from the scope of our invention. It is to be noted, for example, that the combination of thevariable current-compounding resistors i H and the reversing switches I23 may be everywhere replaced by variable potentiometers 053, such as are utilized, for example, in the modifications shown in Figs 5 and 6. I

In the modification shown in Fig. 9, a. number of changes may be made and for that matter the changes may be added to the other modifications in cases where they areof advantage. One change which we regard as of some importance is accuses the insertion of an alternating current potential in the individual control conductors of the discharge devices till, 209, Hi, M3, M5 and 2H. For this purpose a so-called grid transformer may be utilized. It may consist of a star-connected arrangement with 6 windings. Each of the windings may be connected in the conductor leading from a control electrode resistor 2 35, 24?, 249, 25 I 253 and 255, respectively, and the neutral point may be connected to the conductor 25? which in 'Fig. 9 is connected to the variable tap 8533 of the potential compounding potentiometer N35. The remainder of the connections to the variable tap 69 of the main potentiometer 5i and thence to the load ill may be the same as shown in Fig. 9.

Finally it is to be noted that while the discharge devices it, it, 23, 2M, 209, 2M, M3, 2!!) and 2!]? are shown as discrete elements, they may at times be replaced by discharge paths, all or some of which may be disposed in a common container and one or more electrodes Si, 33 or 35 of which may be common to all or some of the paths.

Although we have shown and described certain specific embodiments of our invention, we are fully aware that many modifications thereof are possible. Our invention, therefore, is not to be restricted except insofar as is necessitated by the prior art and by the spirit of the appended claims.

We claim as our invention:

1. Apparatus for supplying power from a source of electrical energy to a load comprising a disv charge path having a plurality of principal electrodes and a control electrode and a gaseous Hiedium interposed between said source and said load, said. load being supplied through said discharge path, means for impressing a. potential of one polarity between said control electrode and one of said principal electrodes, said potential being of a magnitude that is sufliciently large to mask random fluctuations in the critical potential of said discharge path and means for superimposing a potential, dependent on the magtrodes and a control electrode and a gaseous medium interposed between said source and said load, said load being supplied through said discharge path, means for impressing a potential between said control electrode'and one of said principal electrodes of a polarity such as to tend to energize said discharge path, said potential being of a. magnitude that is sufficiently large to mask random fluctuations in the critical control potential of said discharge path and means for superimposing a potential, dependent on the magnitude of the output potential supplying said load and of opposite polarity to said first-named potential, on said first-named potential, said last-named potential being of such magnitude that the critical control potential of said discharge path is at times exceeded.

3. Apparatus for supplying power from a source of electrical energy'to a. load comprising a discharge path having a plurality of principal electrodes and a control electrode and a gaseous medium interposed between said source and said load, said load being supplied through said discharge path, means for impressing a potential.

on said first-named potential, said last-named potential being of such magnitude that the critical control potential of said discharge path is at times exceeded and means for superimposing on said first-named and second-named potentials a potential dependent on the current flow from said source.

4. Apparatus for supplying power from a source of electrical energy to a load comprising a discharge path havinga plurality of principal electrodes and a control electrode and a gaseous medium interposed between said source and said load, said load being supplied through said dis charge path, means for impressing a potential of one polarity between said control electrode and one of said principal electrodes, said potential being or amagnltude that is so large as to mask random fluctuations in the critical potential of said discharge path, means for superimposing a potential, dependent on the magnitude of the.

medium interposed between said source and said load, said load being supplied through said discharge path, means for impressing a potential of one polarity between said control electrode and one of said principal electrodes, said potential being of a magnitude that is so large as to trol potential of said discharge path, means ior A superimposing a potential, dependent on the magmask random fluctuations in the critical control of opposite polarity to said first-named potenan, on said first-named potential, said'last- V named potential being of suchmagnitude that the critical control potential of said discharge path is at times exceeded, means for superimposing on said first-named and second-named potentials a potential dependent on the current flow from said source, and means for superimposing on all said potentials a potential dependent on the potential of said source when power is being supplied to said lead.

Apparatus for supplying power from a source of electrical energy to a load of the type that requires a predetermined compounding comprising a discharge path having a plurality of principal electrodes and a control'electrocle and a gaseous medium interposed between said source and said load, said load being supplied through said discharge path, means for impressing a potential of one polarity between said control electrode and one of said principal electrodes, said potential being of a magnitude that is suiliciently large to mask random fluctuations in the critical connitude of the output. potential of said load and of opposite polarity to said first-named potential, on said first-named potential, said last-named potential being or such magnitude that the critical control potential of said discharge path is at times exceeded, means iorsuperimposing on said first-named and second-named potentialsa potential dependent on the current flow from said source, and means for adjusting the last said potential to select a particular compounding for said load.

source and said load, said load being supplied through said discharge path, means for impressing a potential oi one polarity between said control electrode and one of said principal electrodes, said potential being of a magnitude that is so large as to mask random fluctuations in the critical control potential of said discharge path and means for superimposing a potential, dependent on the magnitude of the output potential supplying said load and of opposite polarity to said first-named potential, on said first-named potential, said last-named potential being of such magnitude that the critical control potential of said discharge path is periodically exceeded.

8. Apparatus for supplying power from a periodic current source of electrical energy to a load comprising a discharge path having a plurality of principal electrodes and a control electrode and a gaseous medium interposed between said 'source and said load, said load being supplied through said discharge path, means for impress ing a potential of one polarity and oi substantially constant magnitude between said control electrodeand one of said principal electrodes, said potential being of a magnitude that is so large as to mask random fluctuations in the critical control potential or said discharge path and means for superimposing a potential, dependent on the magnitude of the output Dotential supplying said load and of opposite polarity to said first-named potential, on said first-named patch tial, said last-named potential being of such magnitude that the critical control potential of said discharge path is periodically exceeded.

9. Apparatus for supplying power from an alternating current source of electrical energy to a load comprising a discharge path having a plurality of principal electrodes and a control electrode and a gaseous medium interposed between said source and said load, said load being supplied through said discharge path, means for impressing a potential or one polarity between said control electrode and one of said principal electrodes, said potential being of a magnitude that is so large as to mask random fluctuations in plurality of principal electrodes and a control electrode and a gaseous medium interposed between each phase of said source and said load, said load being supplied through said discharge path, means for impressing a potential of one polarity between the control electrodes and one of the principal electrodes of all of said discharge paths, said potential being of a magm tude that is so large as to mask. random fluctuations in the critical control potential of said dis charge paths and means for superimposing a potential, dependent on the magnitude of the output potential supplying said load and of op posite polarity to said first-named potential, on said first-named potential,- said last-named potential being of such magnitude that the critical control potential or" said discharge paths is periodically exceeded by the total potential.

11. Apparatus for supplying power from a polyphase source of electrical energy to a direct current load comprising a discharge path having in efiect an anode, a cathode and a control electrode and a gaseous medium interposed between each phase of said source and said load, said load being supplied through said discharge paths, means for impressing a potential of positive po-= larity between the control electrodes and the cathodes of all said discharge paths, said potential being of a magnitude that is large compared to the critical control potential or said discharge paths and means for superimposing on said positive polarity potential a potential of negative polarity, that varies in dependence upon the variation of the output potential supplying said load, and that has a magnitude such that the control potential of said discharge paths is periodically exceeded by the total potential.

12. Apparatus according to claim 11 characterized by the fact that the positive polarity potential is of such magnitude that it masks the variations of the critical control potential arising in any one discharge path or between the discharge paths.

13. Apparatus for supplying power from a poiyphase source of electrical energy to a directcurrent load comprising a discharge path having in effect an anode, a cathode and a control electrode and a gaseous medium interposed between each phase of said source and said load, said load being supplied through said discharge paths, means for impressing a potential of positive polarity between the control electrodes and the cathodes of all said discharge paths, said potential being of a. magnitude that is so large as to mask random fluctuations in the critical control potential of said discharge paths, means for superlmposing on said positive polarity potential a potential of negative polarity, that varies in dependence upon the variation of the output potential supplying said load, and that has a mag= nitude such that the critical control potential oi said discharge paths. is periodically exceeded by the total potential and means for superimposing on said potentials of positive and negative polarlty a. potential dependent upon the magnitude aaaaaso charge paths, means for impressing a potential of the load current to compensate for load cur- 4 path having in effect an anode, a cathode and a control electrode and a gaseous medium interposed between each phase of said source and'said load, said lead being supplied through said dis- 'of positive polarity between the control electrodes and the cathodes of all said discharge paths, said potential being of a magnitude that is sufllciently large to mask random fluctuations in the critical control potential of said discharge paths, means for superimposing on said positive polarity potential 8. potential of negative polarity, that varies in dependence upon the variation of the output potential supplying. said load, and that has a magnitude such that the control potential or said discharge paths is periodically exceeded by the total potential and means for superimposing'on said potentials of positive and negative polarity is potential dependent upon the magnitude of the load current to adjust the compounding.

15. Apparatus for supplying power from a polyphase source of electrical energy to a directcurrent load comprising a discharge path having in effect an anode, a cathode and a control electrode and a gaseous medium interposed between each phase or: said source and said load, said load being supplied through said discharge paths, means for impressing a potential of positive polarity between thecontrol electrodes and the cathodes of all said discharge paths, said potential being of a magnitude that is so large as to mask random fluctuations in the critical control potential of said discharge paths, means for superimposing on said positive polarity potential a potential of negative polarity, that varies in proportion with the output potential supplying said load, and that has a magnitude such that the critical control potential oi said discharge paths is periodically exceeded by the total potential and means for superimposing on said potentials of positive and negative polarity a potential proportional to the magnitude of the load current to compensate for load current variatiohs,

16. Apparatus for supplying power from a source of electrical energy to an electrodynamic machine having an armature and independent excitation means comprising an electric discharge path having a control electrode and a plurality of principal electrodes and a gaseous medium, interposed between said armature and said source, said armature being supplied through said discharge path, means for impressing a potential of magnitude sufilciently large to mask random fluctuations in the critical control potential of said discharge path between said controlelectrode and one of said principal electrodes and means for superimposing on said first-named potential a potential dependent on the magnitude of the current flow through said armature.

1'7. Apparatus for supplying power from a source of electrical energy to an electro-dynamic machine having an armature and independent excitation means, comprising an electric discharge path, having a control electrode and a plurality of principal electrodes and a gaseous medium, interposed between said armature and said source, said armature being supplied through said discharge path, means for impressing a potential of magnitude sufliciently large to mask random fluctuations in the critical control potential of said discharge path between said control electrode and one of said principal electrodes and means for superimposing on said first-named potential 9. potential proportional to the magnitude of the current flow through said armature up to armature potentials of magnitudes for which the potential of the source is sumcien't. 1

18. Apparatus for supplying power from an alternating current source oi electrical energy to an electro-dynamic machine having an armature and independent excitation means, comprising an electric discharge path, having a control electrode, an anode and a cathode and a gaseous medium, interposed between said armature and said source, said armature being supplied through said discharge path, means for impressing a potential of magnitude suillciently large to mask random fluctuations in the critical control potential of said discharge path and of positive polarity between said control electrode and said cathode and means for superimposing on said first-named potential a potential of negative polarity dependent on the magnitude of the current flow through said armature.

19. Apparatus for supplying power from a polyphase source electrical energy to an electro-dynamic machine having an armature and independent excitation means, comprisingin eiiect an electric discharge path, having a control electrode, an anode and a cathode and a gaseous medium, interposed between said armature and each phase of said source, said armature being supplied through said discharge path, means for impressing a potential of magnitude so large as to mask the variations arising in the critical control potential of each said discharge path and between the critical control potentials of all said discharge paths and of positive polarity between the control electrode and the cathode of all said discharge paths and means for superimposing on said first-named potential a potential proportional to the magnitude of the current iiow through said armature up to armature potentials of magnitudes for which the potential of said source is sufllcient.

20. Apparatus according to claim 19 characterized by photo-sensitive means for controlling the excitation of the machine.

21. Apparatus for varying the supply at power from a source 01 alternating current to a load of the type that has the properties of a short circuit comprising an electric discharge path having a control electrode and a plurality of principal electrodes and a gaseous medium interposed between said source and said lead through which current flows to said load, means for impressing a -potential, proportional to the current flow irom from a source 01' alternating current to a load of the type that has the properties oi a short circuit comprising an electric discharge path having a control electrode and a plurality of principal electrodes and a gaseous medium interpoad between said source and said load through which current flows to said load, means for impresing a potential, proportional to the current iiow from said source when said load is being supplied, between said control electrode and a principal electrode 0! said path and means for impressing a direct current potential independent of the said current iiow but variable in magnitude in accordance with the load current desired between the said control electrode and the last said principal electrode. f

desired between the said control electrode and 23. Apparatus for varyingthe supply of power from a source of alternating current to a load of the type that has the properties of a short circuit comprising an electric discharge path having a control electrode and a plurality of principal electrodes and a gaseous medium interposed between said' source and said load through which current flows to said load, means for impressing a direct current potential, proportional to the current flow from said source when said lead is being supplied, between said control electrode and a principal electrode of said path and means for impressing a direct-current potentialindependent of the said current flow but variable in magnitude in accordance with the load current the last said principal electrode.

24. Apparatus for varying the supply of power from a source of alternating current to a load of the type that has the properties of a short circuit comprising an electric discharge path having a control electrode, an anode and a cathode and a gaseous medium interposed between said source and said load through which current flows to said load, means for impresing a direct current potential, proportional to the current ilow from saidsourcewhensaidloadisbeingsupp ebe-' cuit comprising an electric discharge path having a control electrode, an anode and a cathode and a gaseous medium interposed between said source and said load through which current flows to said load, means for impressing a direct current potential proportional to the current flow from said source, when said 108d is being supplied between said control electrode and said cathode of said path and means for impressing a direct-current potential independent of the said current flow but variable in magnitude in accordance with the load current desired between the said control electrode and said cathode, said variable potential being opposite in polarity to said proportional potential.

26. Apparatus for varyin the supply of power from a source of alternating current to a load of the type that has the properties of a short circuit comprising an electric discharge path having a control electrode, an anode and a cathode and a gaseous medium interposed between said source and said load through which current flows to said load, means for impressing a direct current potential proportional to the current flow from said source, when said load is being supplied, between said control electrode and said cathode oi said path and means for impressing a direct current potential independent of the said current flow but variable in magnitude in accordance with the load current desired between the said control electrode and said cathode, said variable potential being podtive in polarity and said proportional potential being negative in polarity.

WILLIAM M. GOODHUE. ROY B. POWER. Jn.