US1710755A

US1710755A - Generator-voltage regulator

Info

Publication number: US1710755A
Application number: US238812A
Authority: US
Inventors: Charles P West
Original assignee: Westinghouse Electric and Manufacturing Co
Current assignee: CBS Corp
Priority date: 1927-12-09
Filing date: 1927-12-09
Publication date: 1929-04-30
Anticipated expiration: 1946-04-30

Description

3 Sheets-Sheet C. P. WEST GENERATOR VOLTAGE REGULATOR Fly: 1.

Filed Dec. 9, 1927 LL 8 e W Y R. M m R W m vm T m? A a h C B llll f m W a fiqfi April 30, 1929.

Fay-.4

April 30, 1929.

c. P. WEST 1,710,755

GENERATOR VOLTAGE REGULATOR Filed Dec. 9, 1927 5 Sheets-Sheet 2 INVENTOR Charles P. West April 30, 1929. R WE T 1,710,755

I GENERATOR VOLTAGE REGULATOR Filed Dec. 9, 1927 3 Sheets-Sheet 3 I A'l'l'A l 2 INVENTOR Charles P, West A ORNEY Patented Apr. 30, 1929.

- UNITED STATES V 1,110,155 PATENT OFFICE.

CHARLES P. WEST, OF PI'J.".I.SIBURGH, PENNSYLVANIA, ASSIGNOB '10 WESTINGHOUSI ELECTRIC 8c MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA.

GENERATOR-VOLTAGE REGULATOR.

Application 'filed December 9, 1927. Serial No. 238,812.

This invention relates to a regulator for generators, the general object of which is to maintain the generator voltage substantially constant under all conditions of load.

Another objectof this invention is to provide a generator-voltage regulator which has no moving elements or contacts.

A further object of my invention is to provide a generator-voltage regulator by which any degree of overor under-compounding may be obtained.

A still further object of this invention is to provide a generator-voltage regulator which shall not be subject to hunting or over-shooting.

Another object of my invention is to provide a generator-voltage regulator which is characterized by a quick response to changes in the generator voltage.

Another object of my invention is to arrange for the direct control of the generator field current.

Another object of my invention is to provide a method of regulation in which the corrective eii'ect is a function of line voltage, line current, and load power-factor, co-ordinating the C01 rect act-ion of each to derive a net result which will compensate for each of the above variables under all conditions.

My invention may be more thoroughly understood by reference to the accompanying drawings, in the various figures of which I have illustrated several modifications of the invention.

Figure 1 is a diagram showing how my invention may be applied to a direct-current generator.

Fig. 2 is a diagram showing how the same system may be utilized in connection with an alternating-current generator.

- Fig. 3 is a diagram of a slightly difierent I modification of my invention shown in connection with an alternating-current genorator.

Fig. 4 is a graph illustrating the currentvoltage characteristics of some of the elements of the system shown in Fig. 3.

Fig. 5 is a diagram of a still further modification of my invention.

Fig. 6 is a graph similar to that shown in Fig. 4. I

Figs. 7 8 and 9 are vector diagrams illustrating graphically the operation of the means which provide in the system of Fig. 5, for compensating for variations in the power factor of the load supplied by the generator.

Figs. 10 and 11 are diagrams illustrating further modifications of the systems shown in Figs. 1 and 2.

In Fig. 1, is illustrated, at 1, a direct-current generator driven by a prime mover 2 which may be of any suitable type. The generator 1 supplies current to the busses 3 and 4. At 5 is shown a three-legged reactor hav- 65 ing a winding 6 equally distributed on the two halves of the core. The winding 6 is energized from a constant-potential alternatingcurrent source 7 through a regulatin impedance 8, and is connected to a rectifier 10 which may be of any suitable character, but which I have illustrated as of the copperoxide-disk type such as disclosed in United States Patent 1,640,335, issued August 23, 1927, to L. O. Grondahl. The output of the rectified is supplied to the field winding 11 of the generator 1 in series with which is connected a winding 12 on the center leg of reactor 5.

Additional windings

14 and 15 are placed on the center leg of the reactor core and are connected, respectively, across the busses 3 and 4, and to a shunt 16 in bus 4. The

windings

14 and 15 are thus energized in accordance with the voltage of, and the load on the generator 1.

The embodiment of my invention shown in Fig. 1, in common with the other modifications thereof shown in the remaining figures, depends, for its operation, upon the principle that the superposition of a uni-directional flux upon an alternating flux in a magnetic circuit, has the effect of reducing the effective reactance of the winding inducing the alternating flux. The winding 6 on the reactor 5 when energized by the alternating-current source 7, induces an alternating flux which confines itself to the outer legs of the reactor core because of the fact that the primary winding is equally distributed on the two halves of the core and, as a result, the net alternating flux in the center leg is zero. Norreally, the winding 6 has a high reactanee. By means of

thewindings

11, 14 and 15, however, I arrange to superpose upon the alternating flux in the core of reactor 5, a unidirectional flux which, as explained above, has the effect of reducing the effective reactance of the winding 6.

The manner in which the system shown in Fig. 1 operates to control the voltage of the generator 1 will now be described. Assuming that the generator 1 is stationary, because of the high impedance of reactor 5, only a small current will flow from the alternatingcurrent source 7 through the rectifier 10, resulting in a correspondingly small flow of direct current through the field winding 11 and the direct-currentreactor winding 12. Now if the generator 1 is started, voltage will appear across the busses 3 and 1. This causes the cnergization of the winding 11 which, as shown by the arrows, is so wound that its magnetomotive force opposes that of the winding 12. The windings 12 and 1-1, however, are so designed that, during the period in which the generator voltage is building up, the winding 12 is more effective in saturating the reactor core than the windingl i. The increase in the net, uni-directional flux in the center leg of the core, resulting from energization of the winding H, reduces the reactance of the winding (3 in accordance with the explanation given above. The reduction in the reactance of the winding 6 increases the current supplied to the rectifier 10 by the source 7, and it is for this reason that the field current builds up from its initial minimum to its normal value.

The winding 14, in cooperation with the winding 12, causes the generator field current to build up to the point at which normal excitation is provided for the generator. Now, if the line voltage increases, because of a sudden decrease in load, for example, there will result an increase in the current in the winding 14. This, in turn, causes the reactance of the winding 6 to be increased because of the decrease in the net, uni-directional saturating flux, and, as a consequence, the generator field current is reduced to cause a reduction in the voltage across busses 3 and 4.

If the line voltage decreases for any rea son, such as a sudden application of load, the first result will be a decrease in the current through the winding 14. The next effect will be an increase in the net, uni-directional, saturating flux, causing a decrease in the reactance of the winding 6 followed by an increase in the output of the rectifier 10 which increases the excitation of the generator to bring the generator voltage back to its normal value.

By utilizing an additional winding 15, it is possible to provide for overor under-compounding of the generator 1. This is accomplished by energizing the winding 15 in proportion to the current supplied to the load. If the winding 15 is so connected that its -magnetomotive force aids that of Winding 12, the result will be that, as the load current supplied by the generator increases, the reactance of the Windingffl is decreased, because of the increased uni-directional flux which saturates the transformer core, and the generator field current will be increased,

tending to increase the voltage generated, giving the generator the characteristic of a cumulative compound machine. If, however, the winding 15 is so connected that its magnetic ctt'cct is opposed to that of the winding 12, an increase in generator current will result in an increase in the rsactance of the winding (3, because of the reduction of the uni-directional flux in the transformer core. This, obviously, will result in a decrease in the generator field current and a decrease in the generator voltage, and the generator will have a characteristic similar to that of a differential compound machine. The degree of overor under-compounding may be controlled, of course, by suitably proportioning the winding 15 and the shunt 16.

Fig. 2 illustrates a modification of my invention in which the general scheme is the same as that shown in Fig. 1, the principal difference being that Fig. 2 illustrates an alternating-current generator 1, the armature of which is connected to

busses

17, 18 and 19. The reactor 5 and its associated windings are identical with those shown in Fig. 1, except that the winding 6 may be energized from one phase of the generator. A separate alternating-current source, however, may be employed, if desirable. The

windings

14 and 15 are energized by direct current from rectifiers 20 and 21, in accordance with phase voltage of the generator and the load current, respectively, the rectifier 21 being energized by the current transforn'ier 22, in proportion to the load current.

The operation of the system shown in Fig. 2 is substantially the same as that described in Fig. 1. The reactance of the winding (3 is varied in accordance with the cnergization of the direct-

currcnt windings

11, 14 and 15 which are energized in proportion to the generator field current, generator voltage and the load current. The energization of the field winding 11 is, of course, dependent upon the reactance of the winding 6, which controls the current supplied to the rectifier, and. in this way, the generator field current is varied in agreement with Variations in the generator voltage and generator current to compensate therefor, as desired.

In Fig. 3, is illustrated an improved system embodying my invention. As in the previous figures, the generator 1 is driven by the prime mover 2 and supplies current to a load connected to the

busses

17, 18 and 19. In the system of Fig. 3, a constant-current transformer 30 is employed as the source of alternating current for the device which I utilize to control the generator field cur-. rent. The transformer 30 may be connected to one of the phasesof the generator or may be supplied with alternating current from any suitable source. Connected in series with the secondary of the constant-current transformer 30 are

rectifiers

31 and 32. The rectiltlll fier 31 supplies direct current. to the field transformer will be energized from the winding of a reactor 36 having an iron core. The reactor 36 serves the same purpose as the reactors ot' the preceding figures. The current output of the transformer 3t) is substantially constant be fause of its design characteristics, and, by varying the eitective reactance of thereactor connected in parallel with the rectifier 31, the current through the reactor may be varied, resulting in corresponding variations in the current supplied to the rectifier 31 and to the field winding of the exciter 34. The ctlective reactance of the reactor is varied by energizing direct-current windings on the center leg of the reactor 36.

The rectifier 32 supplies direct current to a winding 41 on the reactor for the purpose ot'exciting the core witha uni-directional, biasing flux. The exciter 34 suppliesdirect current to the field winding of the generator 1 through the slip rings 37. In series with the generator field winding is connected the winding 39 on the reactor core. A winding 38 is energized by'current from a rectifier 42 which is supplied with alternating cur rent from a current transformer 43- in accordance-with the current supplied by the generator 1' to its load. The direetionsot the magnetoinotive forces of the various windings on the center leg of the reactor core.

are indicated by arrows.

A voltage-compensating winding is connected to a local circuit comprising rectifiers 44 and 45' in series and two

equal resistors

43 and 49, at points between the rectitiers and the resistors. The rectifiers 44 and 45 are connected to the secondaries of

transformers

46 and 47, the primary windings of which are connected in series with a reactor 50 and a resistor 51, respectively. The reactor and the resistor circuits are connected, in parallel. to one phase of the generator and have characteristics such that, when normal generator voltage exists across the conductors 13 and 19, equal currents will flow through the reactor. and the resistor. Under these conditions, the direct-current voltages of the rectifiers 44 and 45 will be'equal. and the voltage at a point between the r'ectifiers will be the same as that of a point between the

resistors

43 and 49. Consequently, there will be no current flowing through the winding 40. The characteristics of the reacto 5t) and the resistor 51 are shown inFig. 4 by the curve and the straight line, respectively.

The operation of the regulating system shown in Fig. 3 may be described as 't'ollows:

Consider that the generator 1' is being driven at normal speed by the prime mover 2 and is,v generating normal voltage. The

generator 1, and the rectifier 31 will supply current to the field of the exciter 34. The rectifier 32 supplies direct-current to the winding 41 to bias the core of reactor 36, so as to reducethe etl'ective value of the reactance of the winding 35, to control the current supplied to the exciter field by therectiticr 31. The winding 32) is in series with the field of the generator 1, and its magnetomotive force opposes that of the winding 41. The magnetolnotivc force of the winding 33 also opposes that of the biasing winding 41, and that of the winding 40 may be in either direction, depending upon the direction ot'current in the winding. 3

Under normal operating conditions, the constants of the circuit are designed so that normal current will flow through the field winding of the exciter 34. It the bus voltage should, for any reason, such as a sudden removal of load. be increased above its nornial value. the current through the resistor 51' will'be greater thanthat through the reactor 50. as may be observed from curves shown in Fig. 4. This will result in an unbalanced condition in the local circuit including the rectifiers 44 and 45 and the

resistors

43 and 49. Direct current will then flow in the winding 40 in such direction as to aid.

the winding 41 in saturating core 34. This r sults in adecrease in the effective value of the reactance ot the winding 35 and a decrease in the current supplied by the transformer 30 to the rectifier 31. The current supplied to the field 33 of the exciter 34 is.

in turn. decreased, and the current supplied to the field winding of generator 1 is correspondingly decreasedto reduce the gen erated voltage.

If, however, the bus voltage should decrease for any rcason,the direct-current voltages of the rectifiers 1-4 and 45 would be unequal, and the local circuit, including the l'octilicrs 44 and 45 and the resistors 48 and 45). would again be unbalanced but the current supplied to the winding 40 in this case would be in such direction as to oppose the saturating niagnetoniotive force of the winding 41, and to increase the reactance of the winding 35 which, of course, causes a greater portion of the output of transformer 30 to pass through the rectifier 31, resulting in an increase in the exciter field current which results in-an increase in the generator voltage. The winding38is soconncctcd that the directcurrent supplied to it from rectifier 42 sets up a magnctoulot'ivo force opposing that of the saturating winding 41. in proportion to the current supplied by'the generator 1 to its load. If the generator current increases, the inagnetomotive force of the winding 38 opposes that ofthe winding 41. decreases the saturation of the core 34 and increases the eftective'value of the reactance of the winding 33 so that more current is supplied by the rectifier 31 to the field 35 of the exciter 36. In this manner, an increase in generator load "current is followed by an increase in generain opposition to that of the winding 41. As a result of' this arrangement, any change in the system which tends to increase the generator field current, by means of the winding 39, tends to increase the reactance of the winding 33 and thereby to increase the exciter field current, to still further increase the generator field current. The same is true of any invfiuence tending to decrease the generator field current.

By suitably designing the elements of the system illustrated in Fig. 3, it may be possible to eliminate the exciter 34 and to utilize the rectifier 31 to supply direct currentdirectly to the field winding of the generator 1'. By the use of such a system, even quicker response to changes in the load circuit is obtained.

It is to be noticed, in connection with the system shown in Fig. 3, that no moving parts are employed and no contacts are required to be made or broken. There is no tendency for this regulating system to hunt or overshoot. This is because of the fact that the corrective effect or, in other words, the influence tending to bring the generator voltage back to normal, in case of variation therefrom. is proportional to the variation from normal voltage. As a result of these characteristics, when the generator voltage approaches its normal value, the tendency for it to be corrected to that value is'correspondingly decreased. In the case of a wide divergence of the generator voltage from its normal value, .a correspondingly strong tendency will be effective to bring the voltage back to normal. These characteristics represent marked advantages over voltage regulators known heretofore.

Fig. 5 illustrates the circuit diagram of a further modification of my invention which is an improvement over that described above. In this modification, I provide not only for compensating for load current and generator voltage, but also for load power factor.

The alternating-current generator is indicated at 1 and its associated prime mover at 2. Direct current for the generator field is controlled by a rheostat 52 and is obtained from rectifiers 75 which are illustrated as of the mercury-arc type and which are energized by the transformers 76, the primaries of which are connected to the basses 17 18 and 19. In series with the primary windings of the transformers 76, are the exciting windings 77 of the reactors 78, 79 and 80. The" by the transformer 87 in accordance with the load current supplied by the generator 1,

The winding 82 is energized by current from a local circuit including the

rectifiers

88, 89 and the

resistors

90 and 91, in exactly the same manner as described in connection with Fig. 3, the

rectifiers

88 and 89 being in series with imp'edan'ces 92 and 93 of different characteristics, as shown in Fig. 6, such that, at normal generator voltage, equal currents flow through the said impedances. The im-'

pedances

92 and 93 are supplied with current from the tertiary'wiudmg of a transformer 94 connected to one of the generator phases. The winding 83 is energized by the output of rectifier 95 which also is connected to the tertiary winding of transformer 94. The function of the winding 83 is to supply a constant, uni-directional, biasing flux in the core of the reactor.

The windings 84 and 85 are energized by direct current from rectifiers 96 and 97, respectively. Alternating current is supplied to'these rectifiers by means of

current transformers

100 and 101, respectively and also by the secondary winding of transformer 94 which supplies current to a condenser 98 and an inductance 99, in parallel, which are connected to the rectifiers 96 and 97, respectively.

It is well known that a synchronous alternating-current generator requires less excitation for the same output at a leading power factor than at a lagging power factor, and it is the function of the windings 84 and 85 to control generator field current in accordance with the power factor of the load current. The manner in which this is accomplished may be best understood by considering Figs. 7, 8 and 9, in connection with Fig. 5.

The

current transformers

100 and 101 supply the rectifiers 96 and 97 with an alternating current proportional to, and in phase with the current supplied by the generator to its load. The transformer 94, through the condenser 98 and the inductance 99, supplies to the rectilfiers 96 and 97, respectively, currents which are in leading and lagging quadrature, respectively, with the generator voltage. The energization of the windings 84 and 85 of the reactor 78 is a function of the resultants of the leading and lagging quadrature components of the current from the condenser iao E represents the generator voltage and I represents the enerator current. In leading quadrature with the generator voltage is the current 1 and, in lagging quadrature with the same voltage, is the current I These currents are obtained from the condenser 98 and the inductance 99. The resultant of I and I is indicated at 1,, while the resultant of I and I is shown at I The currents I and I respectively energize the rectifiers 97 and 96, and the windings 85 and 84 are energized by direct current from the rectifiers in the same proportion. The windings 84 and 85 are connected so that'their magnetoinotlve forces are opposing. When the power factor of the load is unity, therefore, the magnetic efiect of the two windings is equal and opposite, and the net effect is zero; v

In Fig. 8, the condition of lagging power factor of the load current is illustrated. In

this case, the leading quadrature component I combined with the load current I, results in the current I and, similarly, 1,, is the resultant of I andI. It is obvious that, at lagging power factor, I is larger than I and, as a result, the'winding 85 energ1zed thereby will exert a greater effect on the magnetic circuit of reactor 78 than the winding 84 energized by I The inagnctomotive force of the windin g 85 is insuch direction as to aid that of the saturating winding 83. As a result of lagging power factorof the load current, the winding 85 exerts a stronger effect on the magnetic circuit than the winding 84 and, aided by the effect of winding 83, saturates the core 78 to decrease the reactance of the Winding 77, permitting more current to flow through the associated primary of the transformef76 connected thereto, so that a greater field current is supplied to the generator field from the associated rectifier 75.

When the power factor of the load is leading, however, conditions are as illustrated in Fig. 9. In this case, the resultant I is greater than 1,, and, consequently, the wind- .ing 84 of the reactor 78 is more effective in saturating the core than the opposing wind- .ing 85. The efiect of'the winding 84 is to decrease the saturation of the core, as a whole, and to increase the reactance of the winding 77 which, in turn, decreases the current in the primary of the transformer 76 and also decreases the output of the rectifier 75, decreasing the generator field current to reduce the excitation. In this manner, the system of my invention operates so to vary the excitation as to compensate for any change in power factor of the load current.

Although, for the sake of clearness, I have shown the power-factor-compensating means only on the reactor 78, it is, of course, obvious that the'same compensation should be applied to the windings 84 and 85of the reactors 7 9 and 80. The saturating winding 83 is also employed on the reactors 78 and 79.

winding (5 connected in parallel.

The voltage-compensation means shown in connection with reactor 80 1s, of course, applied also to the wmdmg 82 of

reactors

78 and 7 9. Each phase of the generator is thereby provided with means for compensating for all variables, VIZ, voltage, current and power factor.

Fig. 10 illustrates a still further modification of my generator-voltage regulator which is similar to that shown in Fig. 1. In Fig. 10, however, the rectifier, supplying the direct current to the generator field, is connected in parallel with the reactor which controls the value of the generator field current. In Fig. 10, the generator is shown at 1, the prime mover at 2 and the reactor at 5. The winding 6 of the reactor 5 is energized by an alternating-current source 7 through an impedance 8, the value of which, in comparison to that of the reactor, is sufiicently high so that a substantially constant current is supplied by the source 7. Any other constant current source, however, may be substituted for generator 7 and impedance 8. In addition to the

windings

12, 14 and 15, shown in Fig. 1, I provide an additional winding 13 on the center leg of the reactor 5 which is supplied with direct current from rectifier 10, which is in series with the recti tier 10 and the The function of the winding 18 is to saturate the core of the reactor 5 with a substantially constant flux, to reduce the impedance thereof so that only a small current is supplied to the field 11 by the rectifier 10, when the generator is stationary.

\Vhcn the generator is started, however, the small current supplied to the field thereof causes a small voltage to be generated and this voltage energizes the winding 14 which is connected to the busses 3 and 4. The magnet- ()ll'lOtlVO force of the winding 14, as shown by the arrows, is in the same direction as that of winding 13. The winding 12 is in series with the generator field winding and the rectifier 10 and is so connected that its magnetic effect is opposed to that of winding 14. These windings are so designed that winding 12 is more eitective in saturating the core than winding 14, during the period in which the generator voltage is building up. As the voltage on the busses 3 and 4 increases, the saturating liux in the core of the reactor 5 is reduced because of the increased energization of

windings

12 and 14, and the impedance of the reactor is therefore increased. This results in a larger current through the rectifier 10 and, of course, a larger directcurrent output therefrom to the generator field. 11.

The winding 12, as in Fig. l, is energized by the current supplied to the generator field, and its action is to hasten any change in the generator field current resulting from a change in generator voltage. The function of the winding 15, which is energized in pro portion to the current supplied by the generator l to its load, is the same as that of the corresponding winding in Fig. 1.

If the bus volta e rises, because of a sudden removal of load, forinstance, the current in winding 14 is increased, and, therefore the net saturating flux is increased. 'The reactance of winding 6 is simultaneously reduced, and the current supplied to the generator field 11 is decreased. I

If the bus voltage decreases, however, when load is suddenly applied to the generator, the.

decrease in the current through winding 14 increases the impedance of reactor 5 by decreasing the saturating flux, and a greater current is thereupon supplied to the generator field winding 11by rectifier 10.

Fi 11 illustrates a system similar to that of Fig. 10 except that it is designedfor use Some of the obvious advantages of the sys terns described above are as follows:

No moving parts or contacts are utilized.

This method of regulating permits the controlling of the generator field itself whereas, in regulating devices heretofore known, the exciter field only, is subject to the control of the regulating evice. The regulator of my invention is, of course, very much quicker to res 0nd to voltage variations than those in which the exciter field current is altered to control the generator voltage.

There is no tendency toward huntingl, sincethe corrective force decreases as the voltage approaches its normal value.

No rotating exciter is required and the delay introduced thereby is avoided.

By my method, the generator field current is made a function of the generator voltage, generator current and load power factor, each co-ordinating to produce a net result Y which compensates for each of the variables under all conditions.

I claim as my invention:

1. A regulator for controlling the voltage of a generator comprising a reactor having a winding connected to an alternating-current source, a rectifier for supplying direct current to the field windings of said generator connected in series with said reactor winding, said reactor having also direct-current windings energized in accordance with the generator voltage and load current, respectively, tending to vary the energization r of said field windings in response to variatio'ns in the generator voltage and load current.

2. A regulator for. controlling the voltage of a generator comprising a reactor energized from an alternating-current source, direct-current windingson said reactor for controlling the effective reactance thereof, said direct-current windings being energized, respectively, in proportion to the generator voltage, load current and field current, and a rectifier connected in series with said reactor for supplying direct current to the field winding of said generator in accordance with the current-and voltage out-' put of the generator.

3. A regulator for controlling the voltage of a generator comprising means for energizing the field of the generator exciter from the generator, an impedance in parallel with said means and means for varying the effective value of said impedance in proportion to the generator output so as to vary the current supplied to the exciter field whereby the generator voltage is maintained substantially constant under all conditions. i

4. In a regulator system .for controlling the voltage of an alternating-current generator, an exciter for said generator, a constand-current transformer connected to the generator, a rectifier and an impedance in parallel, energized by said transformer, said rectifier being connected to supply direct current to the field winding of the generator exciter, and means for varying the effective value of said impedance in proportion to the generator output to vary the current supplied to said exciter field, whereby .the generator voltage is maintained substantially constant. a

5. A regulator'system for controlling the voltage of an alternating-current generator comprising an exciter for said generator, a constant-current transformer connected to the generator, a rectifier and an iron-core reactor in parallel, energized by said transformer, said rectifier being connected to supply direct current to the field winding of the generator exciter, direct-current saturating windings on said reactor for varying the effective value thereof in accordance with the generator output to vary the current supplied to the exciter field, whereby the generator voltage is maintained substantially constant under all conditions of load.

6. A regulator for controlling the volta e of an alternating-current generator compr1s ing an exciter for the generator, a constantcurrent transformer connected to the generator,'a rectifier and an iron-core reactor in parallel, energized by said transformer, said rectifier being connected to supply direct current to the field winding of the-generator exciter, direct-current windings on said reactor, energized through transformers and rectifiers in accordance with the generator from said sourcedsaid rectifier supplying direct current to the field of the generator exciter, whereby the excitation of said exciter may be controlled by varying the cfiective value of saidreactance.

8. In a regulating system for controlling the voltage of a generator, an exciter for the field winding of said generator, a constantcurrent transformer, a rectifier connected to said transformer for supplying direct current to the exciter field winding, and a variablc'reactor inparallel with said rectifier for controlling the current supplied to said exciter field in accordance with the output of said generator. l

9. A regulating system for maintaining the voltage of an a'lternating-current generator substantially constant comprising a constant-current transformer connected to the generator, a rectifier and an iron-core reactor connected in parallel to said transformer, said rectifier being a'dapted to supply direct current to the field winding of the generator exciter, means for varying the effective value of said reactor in accordance with changes in generator voltage, to vary the excitation ofsaid exciter correspondingly, said means including a direct eurrent winding on said reactor, the current in which is altered in accordance with the generator voltage, whereby the generator voltage is maintained substantially constant.

10. The method of varying the direct current supplied to the field winding of a generator exciter by a rectifier connected to a source 1 of constant alternating current in parallel with a reactor which consists in varying the effective value of said reactor.

11. The method of varying the direct current supplied to the field of a generator exciter bv a rectifier connected to a source of constant alternating current in parallel wlth 'proportion to the voltage of the generator.

12. The method of.controlling the excitation of a generator having an exciter, the

field of which is energized by a rectifier connected to a source of constant alternating current in parallel with an iron-core reactor which consists in superposing on the alternating flux in the core of said reactor a con 'stant unidirectional flux and an opposing unidirectional flux and varying the latter flux in proportion to the current and voltage supplied y the generator and to the generator field current.

13. The combination with a generator regulator comprising a source of constant alternating current, a rectifier, a reactor connected in parallel therewith to said source of constant alternating current, said reactor'having a direct-current winding on itscore to vary its effective value, of means for compensating for Variations in generator voltage comprising impedances having volt-ampere characteristics which intersect at normal generator voltage, connected in parallel to the generator, rectifiers for rectifying the current through said impedances, the direct-current terminals of said rectifiers being connected in series in a local circuit, said direct-current winding befor supplying direct current to thegenerator field from the. generator output, an impedance in series withsaid means and means for varyin g said impedance, to vary the field current, in accordance with the generator voltage; the generator current and the power factor of the load. 16. A system for controlling the voltage of an alternating-current generator comprising means for supplying direct current to the generator field from the generator output, an iron-core reactor in series with said means, and means for varying the effective value of said reactor, to vary the field current, in accordance with the generator voltage, the generator current and the power factor of the load.

17. A static regulator for .generators comprising an iron-core reactor for Controlling the generator field current, direct-current windings on said reactor for varying the efiec tive value thereof in accordance with the generator voltage, the generator current and the power factor of the load.

18. A static regulator for alternating-current generators comprising rectifiers for supplying direct current to the generator field from the generator output, the rectifiers being connected to the generator, an iron-core reactor in series witheach of said rectifiers, for controlling the generator field current, direct-current windings on the cores of said reactors for varying the effective value thereof, and additional transformers and reeti'fiers forenergizing said direct-current windings in accordance with the generator voltage, the generator current and the power factor of the load.

19. In a system for controlling the voltage of an alternating-current generator, an ironcore reactor for controlling the generator field current, a direct-current winding on one core of said reactor for varying the effective Value thereof, a rectifier and a current transformer having its primary connected in a generator lead and its secondary to said rectifier for energizing said direct-current winding in proportion to the generator current. I

20. In a system for controlling the voltage of an alternating-current generator, an ironcore reactor for controlling the generator field current, opposing direct-current windthe effective value of the latter and power factor compensating means for energizing one of said windings in proportion to the resultant of the generator current and a current in leading quadrature with the generator voltage, and the other winding in proportion to the resultant of the load current and a current in lagging quadrature with the generator voltage. x

21. In a voltage regulator for generators, the combination of an iron-core reactor for controlling the generator field current. having opposing direct-current windings for varying its effective value, with power factor compens. ting means comprising means for obtaming currents in leading and lagging quadrature with the generator voltage, means for vectorially combining these currents with the generator current, and means for energizing said opposing windings with direct current proportional to the resultants of the generator current and the leading and lagging quadrature currents, respectively.

22. In a voltage regulator for generators, the combination of an iron-core reactor for controlling the generator field current, having opposing direct-current windings for varying the efieetive valuethereof,with power factor compensating means comprising a condenser and an inductance connected in parallel to the generator, current transformers also connected to the generator, said coudens er and one of said transformers being connected to a rectifier sup-plying one of said direct-current windings, the inductance and the other transformer being connected to a ings on the core of said reactor for changing second rectifier supplying the other directcurrent winding, whereby the generator field current is increased when the power factor is lagging, and decreased when it is leadin In a. generator voltage regulator, the combination of an iron-core reactor for controlling the generator field current and having a direct-current winding for varying the effective value thereof, with voltage compensating means comprising impedances having diil'erent voltage current characteristics, which intersect at normal generator voltage,

connected in parallel to the generator, a local circuit, means for rectifying the currents through said impedances and supplying them to said local circuit, said direct-current winding being connected to said local circuit at points which are of equal potential when the currents through said impedances are equal.

24. In a voltage regulator comprising an iron-core reactor for controlling generator field current and having opposing direct-current windings thereon for varying the effective reacta-nce thereof, the method of compensating for variation in the power factor of the load which consists in energizing one of said windings in proportion to the resultant of the load current and a current in leading quadrature with the generator voltage, and energizing the other direct-current windmg in proportion to the resultant of the load current and a current in lagging quadrature with the voltage.

25. In a voltage regulator comprising an iron-core reactor for controlling generator field current and having a direct-current winding thereon for varying the effective value thereof, the method of compensating for var ations in generator voltage which consists 1n energizing said winding with current in one direction if the generator voltage is high and in the other direction if it is low.

26. In a voltage regulator comprising an iron-core reactor for controlling generator field current and having a direct-current winding thereon for varying the effective value thereof, the method of compensating for variations in generator voltage which comprises altering the direction of the direct current in said winding in accordance with the value of the generator voltage.

In testimony whereof, I have hereunto subscribed my name this 5th day of December,

CHARLES I. IVEST.