USRE20548E

USRE20548E - Apparatus fob controlling load

Info

Publication number: USRE20548E
Authority: US
Publication date: 1937-11-09

Description

Nov. 9, 1937.

E. D. DOYLE APPARATUS FOR CONTROLLING LOAD DISTRIBUTION Original Filed Sept; 19, 1929 9 Sheets-Sheet 1 w INVENTOR.

i4 ATTORNEY.

1937. E. D. DOYLE Re. 20548 APPARATUS FOR CONTROLLING LOAD DISTRIBUTION Original Filed Sept. 19, 1929 9 Sheets-Sheet 2 fil g i 1 JWUT 0:5) I I INVENTOR. W

ATTORNEY.

Nov. 9, 1937. E. D. DOYLE I 20548 APPARATUS FOR CONTROLLING LOAD DISTRIBUTION Original Filed Sept. 19, 1929 9 SheetsSheet 3 1 N VEN TOR.

BY W -W MXQZQM/ f x ATTORNEY.

Nov. 9, 1937.

E. D. DOYLE APPARATUS FOR CONTROLLING LOAD DISTRIBUTION Original Filed Sept. 19, 1929 9 Sheets-Sheet 4 l Ll 3 Nov. 9, 1937.

Re. 20,548 E. D. DOYLE APPARATUS FOR CONTROLLiNG LOAD DISTRIBUTION Original Filed Sept. 19, 1929 9 Sheets-Sheet 5 moi/$4 JNVENTOR. Y @4 4 225. 22 I BY d ATTORNEY.

' Re. 20 548 Nov. 9, 1937. E. D. DOYLE APPARATUS FOR CONTROLLING LOAD DISTRIBUTION Original Filed Sept. 19;1929 9 Sheets-Sheet 6 INVENTOR.

A; ATTORNE".

- Nov. 9, 1937. a DOYLE Re. 20,548

APPARATUS FOR CONTROLLING LOAD DISTRIBUTION Original Filed Sept. 19, 1929 9 Shets-Sheet 'r Nov. 9, 1937. E DOYLE 54 I APPARATUS FOR CONTROLLING LOAD DISTRIBUTION Original Filed Sept. 19, 1929 9.Sheets-Sheet B R3 \\\IL Indenw g I $97617 iii;

E. D. DOYLE APPARATUS FOR CONTROLLING LOAD DISTRIBUTION Original Filed Sept. 19, 1929 9 Sheets-Sheet 9 Lvvzwrm (Si /k 9 :4 ELM Azrozwrx v Reissued Nov. 9, 1 937 APPARATUS FOR CONTROLLING L DISTRIBUTION Edgar 1). Doyle, Philadelphia, Pa., assignor to Leeds & Northrup Company, Philadelphia, Pa", a. corporation of Pennsylvania,

Original No. 1,918,021, dated July 11, 1933, Serial No. 393,650, September 19, 1929. Application for reissue July 9, 1935, Serial No. 30,5Q7

38 Claims. (Cl. 171-119) In accordance with my invention, electrical forces, as voltages, each substantially proportional to the individual loads of a group of genera 10 tors supplying current to a common system, are balanced against an electrical force, as a voltage, proportional to the group load, and the unbalanced forces, or voltages, utilized to control the individual alternators to effect or maintain a de- 10 sired ratio between the individual loads of the alternators.

More specifically, the inputs of the several generators, specifically alternator-s, are each va rled in accordance with the unbalance between 20 the potential drop through animpedance or reslstance in an electrical network, as a potentiometer system, which voltage varies the alternator load, and a potential drop between other points 7 in the network, which isproportional to the 25 group load.

Further in accordance with some modifications of my invention, the unbalanced voltages are each introduced into a frequency-responive net work, as an alternating-current Wheatstone bridge, so that each generating unit is controlled in accordance with the system frequency and the load distribution between the units.

Also in accordance with myinvention, the control of an alternator by a'frequenoy responsive 35 network may be modified by the introduction of a voltage into the network which varies with the alternator load, and more specifically this voltage is effectively in series opposition with a voltage proportional to the total load of several alterna- 40 tors.

My invention also resides in systems, and features of arrangement hereinafter described and claimed.

For an illustration of some of the applications 45 of my invention, reference is to be had to the ac-- ccmpanying drawings, in which Fig. 1- represents diagrammatically a group of electrical generating units or systems controlled in .accordance with my invention.

50 Fig. 2 discloses in diagrammatic form, generat ing systems supplying current to a multiphase system.

Figs. 2a and 2b are fragmentary sketches depicting modes of energizing the field winding of 5 a galvanometer utilized in the preceding systems.

Figs. 3 and 3a illustrate modifications of the system shown in Fig. l utilizing other types of control.

Figs. 4 an'd5 diagrammatically show automatic control systems for maintaining substantially 5 constantly the load upon generating units.

Figs. 6 and. 7 are perspective views of control apparatuses capable of being utilized in the aforesaid systems.

Figs. 8, 8a,, 9, and 9a illustrate other applica- 10 tions of my invention.

Referring to Fig. 1, the generators Al, A2 and A3, specifically alternato'rs, supply current to a common system represented by conductors Ll, L2. The alternators are driven by prime movers, TI, T2 and T3, for example turbines, connected to the same ordifferent steam generators, not shown, through pipes Pl, P2 andP3; valves VI, V2 and V3 controlling the flow of steam to the turbines as hereinafter described.

To the feeder conductors Cl, Cl from alternator Al are connected points of an alternating current .Wheatstone bridge N, conjugate points of which are connected to a galvanometer GI. Movement of the movable element of the galvanometer GI in response to unbalance of the bridge, is utilized as hereinafter described, and originally claimed in co-pending Wunsch application Serial No. 18,794, filed March 27, 1925, patented March 25, 1930, No. 1,751,538, to control the position of a movable contact I adapted to engage selectively

contacts

2 or 3, which constitute therewith a reversing switch controlling energization of a motor Ml A governor mecha nism Rl' driven by turbine Tl controls position of the throttle valve VI to maintain the frequency of the alternator Al within a narrow range of frequencies. Departure of the frequency of the alternator Al from a fixed or predetermined magnitude, usually within the above mentioned 40 band of frequencies, effects unbalance of the bridge N or equivalent network. The movable element of the galvanometer GI moves in a sense, and preferably also to an extent, determined by the sense and extent of the unbalance of the bridge to effect engagement between contact I and either of

contacts

2 or 3 to effect rotation of the rotor of the motor MI in a direction, and preferably also-to an extent, suitably to change the bias upon or setting of the governor mechanismRl.

The mechanism for transmitting movement ofthe rotor of the motor-Ml may, for example, comprise a belt 4, chain or the like for connecting the rotor pulley 5 and a pulley '6 mounted on 5 a shaft 1 which threadably engages one end of a rod 8 whose other end bears against a biasing spring 3 interposed therebetween and the flyball structure of the governor mechanism RI. Alternatively, the motor MI may control the. position of the throttle valve VI, or a supplemental flow-control means which expedients per se are known in the art. The system thus far described maintains substantially constant the frequency of the alternator Al, for changes in load upon the system LI, L2, etc. and is per se claimed in the aforesaid Wunsch application.

I located in the same station as any one or more of the controlled units to be described, or may be remote therefrom. The generating unit 2 between broken lines 3:, 1 may be of the same capacity as unit #I, or smaller or larger, as may be desired. In one of the feeder conductors C2 connecting the alternator A2 to the line wires LI and L2, is included primary ll of a current transformer across whose secondary I8 is con-- nected a potentiometer resistance I9 whose lower terminal is connected as shown to the conductor ll of the control circuit. The terminals of resistance l3 and I! connected by conductor I4 are of the same polarity and substantially of the same potential. A galvanometer' G2 is connected to conductor I5 of the control circuit, and to a contact 20 manually adjustable along resistance I9, the field winding F2 thereof being energized by a transformer t2 whose primary is connected across feeder conductors C2, C2 and whose secondary is connected in; series with the field winding F2 and a compensating circuit c, r, the capacity and resistance of which are of such magnitude and so proportionedas to eifect proper phase relation of the current through field,

winding F2, with respect to the current through the movable coil of galvanometer G2.

Assuming that the loads upon the alternators AI and A2 beara desired or predetermined relation, with respect to each other, the adjustable contacts I6 and 20 are in such position that they are of the same potential and there is therefore no flow of current through galvanometer G2.

'Upon change inload upon the alternator Al the current through the primary III of the transformer II is varied, changing the magnitude of current through resistance l3 'to produce differ-.

ence in the IR. drop of potential across resistance J IS. The resulting deflection of the galvanometer G2 is utilized, preferably by mechanism hereinafter described, to change the, position of movable contact I with respect to the

contacts

2 and 3 which constitute therewith a reversing switch controlling energization of the motor M2 which by mechanism similar or equivalent to that described in conne tion with unit I, controls the setting of the governor,R2. livered to the turbine T2 is varied, changing the load upon the alternator A2, the change in cur- 'rent through the primary I 1 of the current transformer producing change in voltage in the resistance ll between contact 20 and conductor II.

The steam deconductor I4 and between contact 20 and conductor I4 is attained, the movable element of galvanometer G2 returns to zero position for a new setting of governor R2, or other flow controlling mechanism.

Generating unit 3 to the right'of broken line 1 is similar to unit 2, the corresponding elements being indicated by the same reference characters having a sub-index of correspondingly higher order. As many of the units as it may be desired to use, may be similarly controlled, the control conductors I4, I5 being extended as shown for that purpose.

Briefiytherefore, the voltage across resistance I3 is proportional to the load of the group of alternators A2, A3, etc., and the settings of contacts 20 determine the ratio .between the individual loads of altemators A2, A3, etc., which ratio is maintained constant by the control action I described, for different voltages across I3 or the portion thereof selected by adjustment of contact I6. For a different setting of contact I6, or for a diflerent load upon alternator Al, the total load carried by alternator-s A2, A3 assumes a new value but the ratios of the individual loads remain the same for any given setting of contacts Ill.

The controlled units may be the same capacity and character or of widely different capacities and characters, the only criterion being that they supply energy to the same system or load In some instances,

event the load between units is distributed in accordance with the settings of their potentiometer resistances. I

In the system shown in Fig. 1, the line or load system frequency is determined by the alternator AI controlled by the frequency responsive network N, and the load ratio between all of the units is maintained at a desired value by the cone trol circuit l4, IS. The ratio may be varied as desired, by adjustment of the slidable contacts I6, 20 and 20, of the potentiometer resistances I3, I9 and I9. Preferably when an alternator,

as A2, is disconnected from the system, as by opening of switch S2, the circuit of its controlling galvanometer G2 is broken, as by switch 32. If desired, mechanical connection between the switches may be utilized to insure simultaneous operation of the switches as generically indicated by broken line 1:. Cutting in or out of circuit one or more of the controlled units results in automatic re-apportionment of load among the active units in accordance with the ratio determined by their potentiometer settings.

In Fig. 2 there is disclosed a system generally similar to that above described, in which the al ductors, for example LI L2. Of unit 2, the primary II of the current transformer is includedin a conductor C2 connected to line L3, and the 7g field winding F2 of the galvanometer supplied by. resume normal frequency and balance of bridge transformer t2 the terminals of whose primary are connected respectively to the same conductor C2 and to a neutral point 0. Proper phase relation of the current in the field F2 is obtained by the compensating circuit c, r as above described. It will be understood that the number of controlled units may be whatever desired, and that the operation of the system is the same as that of Fig. 1, previously described.

The terminals of the primary oftransformer t2, as shown in Fig. 2a, may be connected respectively, to a conductod C2 and to a selected point of an impedance, as an inductance 23, connected between the other supply conductors, or in phase LIL2. In systems substantially free of harmonics, the compensating circuit 1', c and also additionally transformer t2, may be dispensed with, one terminal of the field winding being connected to the feeder conductor connected to line LI, for example, and the other terminal to a point of inductance 23, or equivalent, connected between the remaining feeders as shown in Fig. 2b.

In the modification of my invention shown in Fig. 3 in lieu of the current transformers in the output circuits of the alternators, there are utilized watt meters WI, W2 and W3, or equivalent, the movable elements, of which are mechanically connected, as indicated by dotted lines, to the adjustable contacts I6, 29 and 20, of the potentiometer resistances I3, I9 and I9, preferably across each of which is connected a source of constant potential, as a battery B, like poles of the batteries being connected to conductor I4. Potential transformers may obviously be utilized in lieu of batteries. Changes in load upon the several units produce corresponding changes in the positions of the movable elements of the watt meters and therefore of potentiometer contacts I6, 20 etc. As in the previous modifications, the potentials, changes of which are produced by variations of load upon the several units, are balanced by the controlling operation of the respective units in accordance with the deflections of a galvanometer connected between the control circuit conductors in series with an impedance or resistance, the effective drop of potential across which is determined by the load upon that unit. By design or selection of the potentiometer resistances, and/or the mechanical connections between the sliding contacts co-operating therewith and the movable elements of the watt meters, the load ratio of the several units may be automatically maintained constant for a range of total load, or may vary in any desired manner throughout a range of total load, or allunits may be controlled to operate on points of their input-output curves having the same slope as described and claimed in my copending application Serial #305,597, filed September 12, 1928 upon which has isused Patent No. 2,054,121.

In the absence of control such as efiected by the frequency-responsive bridge N or galvano'neters G2, G3, etc., the load-speed characteristic of each unit is drooping, i. e., for increase in load the speed decreases. As above explained, the effect of bridge N is to maintain the frequency of the alternator AI, and hence the speed of AI and its prime mover constant. Increase of the system demand momentarily causes a drop in frequency to which the bridge-N responds, acting through galvanometer GI, governor RI, etc, to increase the steam delivered to prime mover TI. As the speed of the alternator is increased to N, the alternator tends to pick up load,- The load-speed characteristic of the master unit I is modified in that the normal speed is maintained constant for substantial variations in load and. does not except momentarily, decrease for increase of load, and vice versa. When'circumstances or conditions are such that objectionable overloading of the frequency-controlled unit may occur, the arrangement shown in each of Figs. 1, 2, 3, 3a, in which the load-speed characteristic of one or more other units supplying energy to the same system, is or are suitably modified by change in load of the master-unit, can be utilized to advantage. As above mentioned in connection with Fig. 3, the load upon the controlled units may be apportioned as desired, the ratio varying with each change of total load to maintain high operating eificiency', for example, of a group of units of dissimilar characteristics, or the ratio of unit loads remaining fixed for varying system demand.

The arrangement shown in Fig. 3a is similar to that of Fig. 3. However, in lieu of batteries B, there are utilized transformers 60 whose primary windings are connected to line LI, L2, and whose secondaries are shunted by the potentiometer resistances I3, II, I9.

In the modification of my invention shown in Fig. 4, the position of the contact I6 is manually adjustable, by an operator, to determine the total load upon units 4 and 5 .and'others if used which will remain constant for variations of the system demand. As in Fig; l, the voltage across the selected portion of resistance I6 is proportional to the group load of the load-controlled alternators, which in Fig. 4 are alternators A4, A5, etc. The distribution or apportionment between units. is predetermined, as aforesaid, by design and construction of the resistances I9, and/or the rela-. tion between the extents of movement of the contacts 20 with respect to their actuating means,

that is, the movable elements of the watt meters W4, W5. As in the systems previously described, the line frequency is maintained substantially constant by unit I, if and when used. Additionally, the master unit I may be associated with and control other units as

units

2, 3, etc. of the preceding figures. It will be understood that the system of Fig. 4 may be modified to effect the same result by using potential transformers in place of the batteries to supply the local circuits of potentiometer resistances I 3, I9. For brevity, the alternators, prime movers, etc. of the units have the same reference letters as the prior modifications described, the subindex however is of different numerical value.

The voltageload-current ratio of a generator output, or the load, if the voltage is maintained constant, of the generator is maintained of desired or predeterminedmagnitude by the system shown in Fig. 5, in which the galvanometer G5 is con nected to the contact 20 adjustable along resistance I9, the drop of potential across which varies with change in output current of the alternator A6, and to contact 23 adjustable along resistance.

24, the drop of potential across which Varies with changes in magnitude of potential in proper phase relation with the current in transformer l1, [8. As shown, the terminals ofthe resistance 24 are connected to the secondary terminals of a transformer the terminals of whose primary 26 are connected respectively to a conductor CI in which the primary II of the transformer IT, I8 is in--. cluded and to a neutral point. 0. If desired the nitude of input energy delivered to the prime mover T6. Any number of units corresponding to unit 6 may be used; each, however, is controlled without substantial effect upon or by the other or others. As in the previous arrangements, the line frequency may'be maintained constant by a frequency controlled unit, as the master unit I. It is understood that to the same system, there may be connected units such as 2, 3 of Fig. 1 and/or units 4, 5 of Fig. 4.

In systems or units utilizing synchronous or rotary converters, dynamotors, etc., the bridge N or equivalent, and current transformers are connected to the alternating current side of the associated electrical system. Watt meters, if used as in Figs. 3 or 4 are or may be connected in either the alternating or direct current circuit, preferably the output circuit.

In Fig. 6 there is disclosed one form of suitable mechanism adapted for use in the systems above described to effect control of motors Ml, etc. in response to deflection of galvanometers GI, etc. An electric motor 21, or other suitable source of power, rotates at substantially constant speed a shaft 28 having thereon, or to which is attached, a cam. 29 which periodically engages the depending arm 36 of a U-shaped member 3| pivoted at

points

32,, 32. A lever 33 is pivoted at its upper end on a horizontal axis and has pivoted thereto on a horizontal axis at its lower end, the arm34, on each end of which is a shoe 35, of metal, or other electrical conducting material, frictionally engaging a fixed disc 36 of conductive material. Secured upon shaft 28 is a cam 31, which periodically engages the lever 33 and moves it outwardly,

in oppposition to a spring not shown, lifting the shoes 35 from disc or plate 36, the spring returning the shoes after predetermined rotation of cam 28. Upon the member 3| is secured element 38, whose upper edge is inclined outwardly from the center. Disposed immediately above the upper, inclined edge of member 38, is the galva-' nometer needle or pointer 39. pointer 38 and beneath which it normally freely swings are the

members

48, 48 pivoted at 4|, 4| and extending toward each other, leaving a gap' of sumcient width between their inner ends for free entry of the pointer 89 when in balanced or zero position. I g

The pointer 39 normally swings freely between the upper edge of member 38 and the members 40, 48, which latter have the downwardly extending arms 42, 42 biased toward each other by spring 43; Attached to the lower side of the arm or lever 34 is a triangular plate 44 carrying the

pins

45, 45, cooperating with the lower ends of the arms 42, 42. .At opposite ends of the arm 34 are lugs 46, adapted to be engaged by cams 41,

41, similar in shape and similarly positioned and secured upon shaft '28. The earns 41, 41 are of.

suitable conducting material, as metal, and are insulated from the shaft 28. Suitable contact brushes 48, 48 are in constant engagement with cams 41, 41, and a conductor 45 is connected to disc 36, and therethrough with arm 34, which corresponds to the movable switch member I of Departure therefrom eflects de- Directly above Figs. 1 to 5, the cams 41, 41 corresponding to the

contacts

2 and 3 in the same figures. When the galvonometer pointer 39 is in its central position neither of the cams" engages lugs 46 and the motor M remains unenergized. As the galvanometer pointer 39 deflects in one direction or the other, the arm 34 is rotated in one direction or the other bringing a lug 46, corresponding to either

contact

2 or 3 of Figs. 1 to 5, into the path of movement of a cam 41, by which it is engaged and moved to its original position, the duration of mechanical and electrical engagement be-' tween the members 41 and 46 being determined 1 by the extent of deflection of the pointer 39.

Particularly when it. is desired to record frequency, or speed, the ,mechanism of Fig. 6 is slightly modified as shown in Fig. '1. The disc 36 instead of being fixed {is supported by or upon a shaft 50 which also carries the slide wire discs '5l, one. of which is shown, and disc 52 carrying the

contacts

2 and 3 of the motor reversing switch. A cord 53 passes around the circumference of a pulley 54 secured to shaft 56, and over idler pulleys 55 to effect? movement of a pen 56, or equivalent, transversely of arecorder sheet 51 fed thereunder by suitable mechanism,

riven. as indicated by motor 21. Preferably to effect rotation f shaft El in accordance with deflections-of the movable pointer 39, the shoes 28a connected to the arm 34, are of cork or other suitable material, and frictionally engage a flange portion of disc 36. The slide wire contacts 58 of the bridge N are stationary and en.- gage slide wires 59 of the Wheatstonebridge carried by slide .Wire disc as aforesaid.

With some power equipment, and with control installations similar to Figs. 1, 2, 3,,etc.,- utilizing a frequency controlled master unit, there is appreciable or substantial lag between th'euchalnge in load, and redistribution of the load among the units, and further the controlled machine must be of sufllciently large capacity to carry during the interval the increase in load. These difllculties are avoided by the methods disclosed in Figs. 8, 8a, 9 and 9a, and now described.

Referring to Figs. 8 and 8a, the generating unit which may be one of a group is subject to load-biased frequency control. The galvan'om eter Gl for example, is included in circuit be tween the manuallyadjustable slide wire contacts 58 in series with a potential varying with load upon the unit.

The potential varying with load may be produced for example, by a current transformer 65 whose primary 65' is included in a feeder CI and whose secondary, shunted by a resistance, is connected to a slide wire contact 58 and to a terminal of the galvanometer GI.

The difference of potential developed across the

contacts

58, 58 is in quadrature with the potential difference impressed on the frequency bridge at thepoints (a) (b), and as this difference must be in phase with' the difference of potential derived from the transformers 65, it is necessary to impress on the bridge, and similarly on the field cireuit of the galvanometer, a

voltage in quadrature with the in-phase component of current in transformer 65. This may be done by any suitable means such as the use of a phase shifting transformer S, or equivalent,

' Fig. 8a, or in a three phase system Fig. 8 by conwith respect to the unbalanced voltage between slide wire contacts 58 is such that as the current through 65' increases the frequency at which galvanometer GI is balanced decreases, and vice versa. The rate at which the frequency varies the frequency at which the galvanometer is balanced for a given load. Any number of loadbiased frequency controlled generators may be connected in parallel tothe same line, the generators may be of like or different capacities, and may be biased to'equal or varying extents.

In Fig. 9 each of the generating units is subject to load-frequency control, the control circuits of the units, however, being so associated that any ratio between the loads of the machines may be selected and maintained irrespective of variations of total load. To that end, the secondaries of the current transformers 62 suitably shunted by resistance, are connected in series with a resistance 66, the current flowing through it being therefore a function of the total load upon the machines.

In series in the galvanometer arm of each of the frequency bridges NEE, N2, N3, etc. is included the secondary of a current transformer 65' shunted by a resistance, and a portion of resistance 66. For example, in series between the

slide wire contacts

58, 58 of bridge NI there is included in series the galvanometer GI, the portion of the resistance shunting the secondary of transformer 65' between the manually adjustable contact H8 and the terminal p of resistance 66, and the portion of resistance 66 between terminal p and manually adjustable contact 64, generally similar to the arrangement of Fig. 8. The portion of resistance 65 between contacts 64 and 64' is included in circuit with galvanometer G2 and a portionof the shunting resistance of current transformer associated with second generating unit connected to feeder C2, C2. Similarly, the portion of resistance 66 between contact 64' and terminal 17 is included in circuit with galvanometer G3 and a portion of the shunting resistance of the current transformer in conductor C3.

'Assuming the contacts H8 are so set that the drop of potential across the shunting resistance of each transformer 65' is equal to the drop of potential across the shunting resistance of a corresponding transformer 62, and further that the ratio between the potential drops across the secondaries of the groups of transformers 62, 65' in conductors CI, C2, G3, etc. are proportional to the loads of the generating units connected there to, the resistances between P and 64, 54 and 64' responds at once to change in load and/or fre-. quency. The difference in potential between the control conductors I4, I5, is a function of the load upon the group of machines and may be produced, for example, by connecting the secondaries of current transformers I00, I M and I02 in series across the conductors. The primaries of the transformers are included in the output circuits of the respective alternators Al, A2 and A3. The total drop of potential between control circuit conductors I4, I5 and across the potentiometer resistances I03, I04 and I05 is therefore proportional to the-total load of the group.

The galvanometer GI controlling unit I, is connected in circuit between the

slide wire contacts

58, 58 of the frequency responsive bridge NI in series with a selected portion of a potentiometer resistance I03 of magnitude determined by setting of the manually adjustable contact I06, and with the resistance shunting the secondary I07 of a current transformer I08 whose primary is included in the output circuit of alternator AI. When the frequency is normal, and unit I is taking its desired share of the total load, the drops across these resistances balance and the galvanometer GI is in neutral position. Similarly galvanometer G2 is at rest or in neutral position, when the frequency is normal, and the potential across the effective portion of potentiometer resistance I04 is balanced by that across the resistance shunting the. secondary I 09 of current trans former I I0 in the output circuit of alternator A2. The same is true of galvanometer G3, and of as many other controlled units as are included in the system.

Upon increase in total load, there is a decrease in frequency, effecting unbalance of the bridges NI, N2 and N3 which causes a flow of current through galvanometers GI, G2 and G3. Deflection of the galvanometers G8, G2 and G3 in turn effects changes in governor settings,- for example, and specifically increases of flow of steam to the turbines TI, T2 and T3.

As the units pick up the load, the potentials across the secondaries I01, I09, eta-increase, and the potentials across the potentiometer resistances I03, I04 also increase. Each unit under the influence of its control effected by its respec-- tive galvanometer tends to operate under a condition at which the potentials tending to cause flow of current through the galvanometer coil are at a balance.

When the load distribution varies without change of frequency, the control effected is solely in accordance with load.

When the settings of contacts adjustable along resistances I03, I04, I05 are such that the sum of the potentials between the contacts and conductor I4 is not equal to the sum of the potential across the secondaries of the individual current transformers I08, IIO, etc., load-biased frequency control is effected.

Figs. 9 and 9a are practically identical in operation but vary in arrangement'in that in Fig. 9a

corresponding terminals of the individual current transformers 65' vary with load and the positions of contacts and 64'. J

The systems of Figs. 9 and 9a comprise a plurality of combined frequency and load control systems of Fig. 8 with provision for load distributors, a totalizing circuit including impedance traversed by current of magnitude representative of total output of said alternators, impedances traversed by currents of magnitude determined by the loads upon the respective alternators, and means individually to control said alternators comprising a frequency-responsive bridge in whose galvanometer arm there is included one of said individual loadimpedances and a selected part of said impedance of said totalizing circuit. 2. In a systemcomprising two or more alternators, a plurality of potentiometer impedances, connections between points of said impedances each including a control instrument, means manualiy to adjust the potential of one of said points, means to vary the potential of each of the other points in accordance with the load of an alternator, and mechanisms controlled by said instruments to vary the input energy of said alternators. I

3. In a system comprising two or more alternators, a like number of potentiometer impedances included in a control circuit, one or more instruments each connected between a control circuit conductor and a point of a corresponding impedance, means to vary the potential of said points, each in accordance .with the load upon an associated alternator, and mechanisms controlled by said instruments to vary the input energy of the alternators.

4. In a system comprising two or more alternators, current transformers in feeder conductors therefrom, resistances in shunt to the secondaries of said transformers, a control circuit including a conductor connecting like terminals of the secondaries of said transformers, instruments connected between a second conductor of said circuit and respective resistances, and mechanism controlled by said instruments to vary the input energy of the altemators.

5. A load distribution system for a group of generators comprising means for producing an electrical force of magnitude substantially proportional to group load, a plurality of means, each producing an electrical force substantially proportional to the individual load of a generator, and a plurality of means for controlling said generators, each responsive to unbalance between said first electrical force and the electrical force proportional to the load of the generator controlled thereby.

6. A load distribution system for a group of generators comprising an electrical network, means for producing in said network a voltage substantially proporti onal to group load, a plurality of means, each producing in said network a voltage substantially proportional to the individual load of a generator, and a plurality of means for controlling the inputs to said generators; each responsive to unbalance between the voltage proportional to the load of the generator controlled thereby and said other voltages, whereby the load ratios of the generators are maintained substantially constant.

'1. A load distribution system for a group of electrical translating units comprising means for producing an electrical force of magnitude substantially proportional to group load, a plurality of means, each producing an electrical force sub: stantially proportional to the individual load of a unit, and a plurality of means for controlling the inputs to said units, each responsive to unbalance between said first electrical force and the electrical force proportional to the load of the unit controlled thereby.

8. A load distribution system for a group of generators comprising means for producing an electrical force of magnitude substantially proportional to group load, a plurality of means, each I producing an electrical force substantially proportional to the individual load of a generator, a

plurality of means for controlling said generators,

each responsive to unbalance between said first electrical force and the electrical force propor tional to the load of the generator controlled thereby, and means for varying said first voltage in accordance with changes of the total load of the group. I

9. A load distribution system for a group of alternators comprising a; plurality of frequencyresponsive networks for'individually controlling the altemators, means for producing a voltage substantially proportional to total load of the group, a plurality of means, each producing a voltage substantially proportional to the individual load of an alternator, and connections for introducing into the frequency-responsive net work of each alternator the diflerence between the voltage proportional to the individual load of the alternator and the voltage proportional to group load.

10. A load distribution system for a group of 11. A control system for an alternator comstantially proportional to 'the load of the 'altemator controlled therebyand a preselected portion of the total voltage across said impedance.

13. A load distribution system for a group of alternators comprising a totalizing circuit including a tapped impedance traversed by current of magnitude substantially proportional to the group load, and a plurality of means for individually controlling the alternators, each comprising a frequency-responsive bridge in whose galvanometer arm is included a portion of said impedance between adjacent taps.

14. A load distribution system for a group of alternators comprising a totalizing circuit including impedance traversed by current whose magnitude is substantially proportional to the group load, means for deriving therefrom a plurality of voltages whose sum may differ from the voltage across said impedance, a plurality of means for individually controlling'the alternators, each comprising a frequency-responsive network, and connections for introducing into each of said networks. one of said derived voltages.

15. The combination in an alternating current system having a plurality of generating units, each unit having means for varying its input, means responsive to both frequency and load variations from predetermined values, and means controlled thereby for effecting actuation of said power input means to control both load and frequency.

16. The combination in an alternating current system having a plurality of generating units, each unit having means responsive to frequency variations from normal whereby a plurality of units are adapted to control frequency simultaneously, and means for varying the sensitivity of at least one of said frequency responsive means automatically in accordance with,

variations in the unit load from a predetermined value.

17. The combination in an alternating current system having a plurality of generating units, each of said units having a frequency controller whereby a plurality of said units are adapted to be simultaneously operative to control frequency, and means whereby each unit in controlling frequency is maintained within a definite load zone. 18. The combination in an alternating current system having a plurality of generating units, each of said units having a frequency controller whereby a plurality of said units are adapted to be simultaneously operative to control system frequency, and means for preventing the load on one unit drifting to another of said units during frequency control.

19. The combination in an alternating current system having a plurality of generating units, means whereby 'a plurality of said units are adapted to control frequency simultaneously auto-' matically in accordance with variations from normal, and means for preventing drift of load from one unit to another. during frequency control in the event of one unit'or its control equipment functioning sluggishly in comparison to the functioning of another frequency controlling unit or its equipment. a

20. The combination in an alternating current system having a plurality of generating units, a frequency controller associated with each of a plurality of said units whereby they are adapted to simultaneously control frequency automatically in accordance with variations thereof from a predetermined value, and means adapted to be selfcontained with each frequency controller to maintain an output of their respective units within a predetermined maximum limit whereby the frequency controlling units may be located at widely spaced points along the system line without permitting drift of load between these units.

21. The combination in an alternating current system having a plurality of generating units, each of said plurality of units having a galvanometer frequency controller whereby the system frequency may be controlled simultaneously by'a. plurality of units, and means cooperating with said frequency controllers for determining the base load setting of the units.

22. The combination in an alternating current system having agenerating unit, a frequency controller adapted during high frequency to lower the output of a unit, and means whereby when the unit load is above a predetermined value the frequency controller additionally tends to lower the unit output whereby an accumulative corrective action of the load output is efiected.

23. The combination. in an alternating current system having a generating unit, a frequency controller therefor adapted to lower the output of Ya unit upon occurrence of frequency above normal, and means whereby during occurrence of frequency above normal and of a unit output above apredetermined value the controller is rendered more sensitive than upon occurrence of either condition alone.

24. The combination in an alternating current system having a generating unit, a frequency controller adapted to increase the unit load automatically upon occurrence of frequency below normal, and means whereby upon a unit load above a predetermined value the frequency corrective action of the controller is opposed and thus rendered less sensitive.

25. The combination in an alternating current system having a plurality of generating units, a

frequency controller adapted to lower the unit 1 output upon occurrence of frequency above nor mal, and means whereby when the unit output is below a predetermined value simultaneously with the existence of frequency above normal the frequency correction of the controller is opposed.

26. The combination in an alternating current system having a plurality of generating units, a

7 frequency controller adapted to raise the unit output upon occurrence of frequency below normal, and means whereby upon occurrence of a unit output below a predetermined value simultaneously with the low frequency the frequency controller is additionally actuated, thereby ren-' .mal frequency, and means whereby upon occur-.

rence of a unit output below a predetermined base load said frequency controller is actuated automatically in response to this load variation to raise the unit load to normal.

' 29. The combination in an alternating current system having a generating unit, and means for controlling the frequency and load including a combined frequency and load controller having a galvanometer Wheatstone bridge.

30. The combination in an alternating current system having a generating unit, means for controlling the frequency and load including a combined frequency and load controller having a galvanometer Wheatstone bridge, and means associated with said bridge circuit for effecting a. predetermined base load setting for the unit to be controlled.

31. A combined load and frequency controller including a Wheatstone bridge circuit, and means whereby current flow therethrough is controlled both by frequency and load conditions.

32. The combination in an alternating current system having a generating unit, a frequency controller tending to remain in neutral position during normal frequency, electrical means associated with said frequency controller and responsive to load variations from normal, and means whereby during variation of frequency is adapted to correct the unit output in accordance with the extent of both the frequency and load variations from their normal values.

33. The combination in an alternating current system having a plurality of generating units, each of said units having a frequency controller whereby a plurality of said units are adapted to be simultaneously operative to control frequency,

system having a plurality of generating units;

each unit having means adjustable to vary its input, means responsive to both frequency and load variations from predeterminedlvalues, and means controlled by said responsive means for eifecting adjustment of said input varying means in a sense and at a rate determined by the sense and magnitude of concurrent variations of load and frequency from said predetermined values. 7

35. The combination in an alternating current system having a plurality of generating units, each of said units having means adjustable to vary its input and a frequency controller therefor whereby a plurality of said units are adapted to be simultaneously operative to control frequency, and means responsive to the unit load to vary the sense and rate of adjustment of said input-varying'means whereby each unit in controlling frequency is maintained within a definite load zone.

36. The combination in an alternating current CERTIFICATE Reissue No. 2o,5i 8.

EDGAR D. DOYLE. 1 It is hereby certified that error appears in the printed specification 2 system having a generating unit, means for vary- OF i CORRECQION,

from normal said load responsive electrical means system having a plurality of generating units, each of said plurality of units having a deflection instrument frequency controller andinput-var'ying means actuated in a sense and at a rate de-.

termined by the sense and extent of deflection of said instrument whereby the system frequency may be controlled simultaneously by a plurality of units, and means responsive to the unit load for affecting the senseand extent of deflection of said instrument in accordance with departure of unit load from a base-load setting.

37. The combination in an alternating current system having a generating unit, means for varying the input to said unit, a frequency controller 'adaptedto efiect automatic adjustment of said means in sense to increase the unit load upon occurrence of'frequencybelow normal and at a rate dependent upon the magnitude of the frequency departure from normal, and means whereby upon a unit load above a predetermined value the frequency corrective action is opposed to decrease the rate of adjustment of said inputvarying means.

38." The combination in an alternating current ing the input to sad unit, a frequency controller adapted to eflfect automatic adjustment of said means in sense to decrease the unit output upon occurrence of frequency above normal and at a rate dependent upon the magnitude of the frequency departure from normal, and means whereby upon a unit output below a. predetermined value the frequency corrective action is opposed to decrease the rate of adjustment of 'said inputvarylng means.

. EDGARD; DOYLE.

November 9, 1957;, i

of the above numbered patent requiring correction as followsi Page 1-, second. column, line 6, for the word "constantly" reed constant; page 5, firstcolmm, line '15, for "conducted" read conductor; line. 29-, after "elements" strike out the comma; page 1+, first 001mm, line 25, after "14."- inaert a H comma; line b5, .for "oppposition" read opposition; and that the said Let.- ters Patent should be read with. these corrections therein that the same may conform to the record of" the case in thePatentfOffice.

Signed and sealed this 8th day oi Harem-A. D. 1958.

(Seal i Henry Van Arsdale, Acting Commissioner of Patents.

is adapted to correct the unit output in accordance with the extent of both the frequency and load variations from their normal values.

system having a plurality of generating units;

36. The combination in an alternating current CERTIFICATE Reissue No. 2o,5i 8.

. EDGARD; DOYLE.

November 9, 1957;, i

Signed and sealed this 8th day oi Harem-A. D. 1958.

(Seal i Henry Van Arsdale, Acting Commissioner of Patents.