US1985004A - Generator voltage regulator - Google Patents

Description

1934- c. P. WEST 1,985,004

GENERATOR VOLTAGE REGULATOR Filed Oct. 22, 1930 2 Sheets$heet 1 48 4.9 [{nflrl Fig.5.

Current Ill 24 Voltage lnauced In Secondary Winding of Current Trans. 62 (C) 58 vozza eBerween 6/ and 66 m) INVENTOR C/zaries P Wes 2.

ATTORNEY Gamer-afar Voltage C. P. WEST Dec. 18, 1934.

GENERATOR VOLTAGE REGULATOR Filed Oct. 22, 1950 2 SheetSSheet 2 Fz'g. 5.

INVENTOR CharZes P West.

TTORNEY Patented Dec. 18, 1934 UNITED STATES PATET Y FFICE f Application (Ilotober 532, 19%, Serial No. 4%,38?

3 Claims.

My invention relates to voltage-regulating systems and, more particularly, to voltege regu lating systems for maintaining the terminal voltages of alternating-current generators sub stantially constant.

In the vibrating type of voltage regulator lli== ployed for maintaining the terminal voltage oi an alternating-current generator substantially constant, resistance is inserted into, or shunted from, the generator field-winding circuit or the field-winding circuit of an exciter by means of movable contact inerniiers. While a regulator or this type gives good voltage regulation, it as the limitation that the contact members wear and burn out, necessitating inspection and re newals.

\ no object of my invention is to ovicl' a voltage-=regulator system for maintain g terminal voltage of an alternating-current erator substantially constant.

Another object of my invention is to pro vicle a voltage regulator for governing an olte13- noting-current generator in which no moving elements or contact members are employed.

A further object of my invention is to provide an alternating=current-generator voltage regu= later that shall he quickly responsive to varia== tions in the generator voltage.

it still further object oi my invention is to provide an alternating-current-generstor v age regulator that characteristics.

My invention will be better understood. from the following description, when read in con junction with the accompanying drawings, in which:

Figure l is a schematic view of apparatus and circuits illustrating one embodiment of my in= vention,

Fig. 2 is a diagrammatic view of selected ele= ments and circuit shown in Fig. i,

Fig. 3 is a series of graphs illustrating the voltage-current characteristics of the tuloe-reo= tiller-control elements shown in Figs. 1 and 5,

Fig. 4 is a series of graphs illustrating the variations in voltage of the tube-rectifier con= trol elements plotted against generator voltage,

Fig. 5 is a schematic view of apparatus and cir cuits illustrating another embodiment of my in= vention.

Referring to Fig. 1, of the drawings, an alter= hating-current generator 2 is illustrated that isprovided with an armature winding 3 and a field winding 4, the armature winding 3 being connected to supply- circuit conductors 5, 6 and shall have anti-hunting (GHQ in ne l, The field winding 4 is energized with menses current derived from the conductors d and 21 through a rectifier 8 which may he of suitable character but which I have illustrated as or" the copper=oxide=disc type, such as is dis to produce flux in some direction in the netic circuit and is connected in series circuit ro e on to the rectifier i3 and the conductorsi5 it i; second win ing 3 is disposed on the ceto' or leg of the core ll and is energized ui-directional current from the generator con rrs and if by means grid-controlled onic tubes, or rec" rs, :ii and 22 in ac cordauce with variations the generator volt== age to vary the saturation of the core ll,

action orthe tubes :21 and 22 is controlled by a transformer 23 that is energized in accorcl= u once with a voltage that is dependent upon t e dllierent changes in the currents flowing t rough an iron core reactor 24 and a non inductive resistor 25 with equal changes in the voltages impressed upon iooth. The reactor end the resistor connected in parallel-circuit relotion and are impressed with voltages that are proportional to the generator voltage.

The variation in impedance of the reactor ii is obtained by application or" the principle that the superposition of a unidirectional flux upon an alternating flux in an. iron circuit saturates the iron and reduces efiective impedance of the winding producing the alternating flux.

The winding 12 of the reactor 9, when ener= gized from the conductors 6 and 7, produces an alternating rlux which confines itself to the outer legs of the reactor core, because of the fact that the flux is in the same direction in the magnetic circuit. By means of the winol ing 13, a uni-directional flux is superposed upon the alternating flux in the core 11, which reduces the efiective impedance of the winding 12. The reactor 9 is so designed that its impedance will be such that the generator voltage will-build up to slightly above its normal value, with the winding 13 unenergized, when there is no load on the generator.

The rectifier 21 is of the hot-cathode-glow type comprising an evacuated envelope 26, in

which are positioned a cathode 27, an anode 28 and a grid element 29. The rectifier 22 is similar to the rectifier 21, having a cathode 31, an anode 32 and a grid element 33 positioned in an evacuated envelope 34.

The cathodes 27 and 31 of the rectifiers 21 and 22, respectively, are heated to incandescence by means of current supplied from any convenien t source, such as a battery 35. The cathodeheating circuit may be traced from one side of the battery 35, through conductor 36, to the junction point 37, where it divides and extends, through the cathodes 2'1 and 31 of the rectifiers 21 and 22, respectively, to the junction point 38, and, by means of conductor 89, to the other side of -the battery 35. A resistor 40 is provided in the cathode circuit in order that the temperature of the cathodes 2'7 and 31 may be controlled.

An alternating voltage is impressed across the anode 28 and the cathode 2'7 of the rectifier 21, and the anode 32 and the cathode 31 of the rectifier 22 by a potential transformer 45, the primary winding 46 of which is energized from the conductors 6 and 7. The secondary winding 47 of the potential transformer 45 is divided into two sections 48 and 49 by a tap connection 51 that is connected in series-circuit relation to the winding 13 on the reactor 9, a winding 52 disposed on the center leg of a three leg iron core reactor 53 and the cathodes 27 and 31 of the rectifiers 21 and 22, respectively. The terminals of the secondary winding 4'7 are connected to the anodes 28 and 32 of the rectifiers 21 and 22, respectively. By these means, fullwave rectification of the alternating current is obtained, and the winding 13 is energized unidirectionally when the rectifiers 21 and 22 are conductive.

It is well known that, in a three-element thermionic tube of the character described, the voltage impressed upon the grid element controls the flow of current through the tube. The tubes 21 and 22 are of such design that, for a particular degree of incandescence of the cathode elements, and for a given voltage impressed across the anode and the cathode, current will not be transmitted through the tube when the voltage impressed upon the grid element is below a certain value with respect to the voltage impressed on the anode or the voltages that are impressed on the anode and the grid element are in different halves of their cycles. When the voltage impressed upon the grid element is in the positive half of its cycle and is of sufficient magnitude, the tubes are conductive.

The transformer 23 comprises a primary winding 56 and a secondary winding 57 that is divided into two equal portions 58 and 59 by means of a tap connection 60 that is connected to the mid-point of the secondarywinding 4'7 of the potential transformer 45. The primary winding 56 is connected between a selected point 61 on the resistor 25 and the secondary winding of a current transformer 62, the primary wind ing of which is connected in series-circuit relation to the reactor 24. The current transformer 62 produces a voltage in its secondary winding that is proportional to the current flowing through the reactor 24. The point 61 on the resistor 25 is so selected that the voltage measured from the point 61- to the conductor 66 is equal to the voltage induced in the secondary winding of the current transformer 62 when the generator voltage is at a predetermined value.

The potential impressed upon the grid member 29 of the rectifier 21 is secured from the half 58 of the winding 57, and the potential impressed upon the grid element 33 of the rectifier 22 is secured from the half 59 of the winding 57 when the primary winding 56 is energized.

The reactor 24 is of the iron-core type, and is connected across the half 49 of the secondary winding 47' of the potential transformer 45 in series-circuit relation to the current transformer 62, and a winding 63 disposed on the two outer legs of the three-leg reactor 53. The circuit for the reactor 24 extends from one terminal of the secondary winding 47 of the potential transformer 45, through conductor 65, conductor 66, the current transformer 62, conductor 67, reactor 24, conductor 68, winding 63 on the reactor 53 and conductor 69, to the mid-point of the winding 47 of the potential transformer 45.

As the voltage impressed upon the reactor 24 varies the current that flows therethrough will vary with the degree of saturation of the iron, as illustrated by the curve A of Fig. 3. A point of operation on the curve A is selected so for the reactor 24 that it is operated at a high degree of saturation in order that small changes in impressed voltage shall produce comparatively larger changes in the current flowing therethrough.

As the voltage induced in the secondary winding of the current transformer 62 is proportional to the current flowing through the reactor 24, the voltage of the secondary winding of, the transformer varies with the generator voltage, as illustrated by the curve C of Fig. 4.

As the voltage impressed upon the resistor 25 changes, the current flowing therethrough will be proportional to the impressed voltage, as shown by the straight line B in Fig. 3, and the voltage between the point 61 and the conductor 66 will vary, as shown by the straight line D in Fig. 4.

In order that the energization of the primary winding 56 of the transformer 23 may be responsive to the different changes in the currents flowing through the resistor 25 and the reactor 24 with equal changes in the voltages impressed on both, it is necessary that the voltages impressed upon the tapped portion of the resistor 25 and the reactor 24 shall be the same, and that the currents flowing through the reactor and the resistor shall have the same phase relation. If the resistor 25 were connected across the same half of the winding 4'7 of the potential transformer 45 as the reactor 24, there would be a phase displacement between the currents flowing through the resistor and the reactor, due to the characteristics of the two circuits. To the end that the currents flowing through the resistor 25 and the reactor 24 shall be in phase with each other, means are provided for shifting the phase position of the current flowing through the resistor.

In order to secure this phase shift, a second potential transformer 74 is provided having a primary winding 75 connected to conductors and 6 and a secondary winding '76. The primary and secondary windings of the potential transformers 45 and 74 are respectively connected together at their neutral points. A non-inductive resistor '77 is connected between the open end of the secondary winding 76 of the potential transsame potential, the transformer former 74 and the mid-point of the secondary winding 47 of the potential transformer 45.

One terminal of the resistor 25 is connected to the neutral point of the secondaries of the two potential transformers and 74, and, if the other terminal of the resistor is connected somewhere along the resistor 77, it is evident that the current flowing therethrough will have a different phase position from what it would have if the resistor were connected across the half 49 of the winding 47. A point of connection on the resistor 77 may be so selected that the current flowing through the resistor shall be displaced sufficiently in phase position to be in phase with the current flowing through the reactor.

The respective designs of the reactors 2c and 53, the resistor 25 and the current transformer 62 are such that the voltage induced in the secondary winding of the current transformer, by the current flowing through the conductor 66, will be equal to the voltage measured from the point 61 on the resistor 25 to the conductor 66, as indicated in Fig. i, when the predetermined voltage exists across the conductors 5, 6 and 7. It is, therefore, apparent that when the voltage across the conductors 5, 6 and 7 is at the predetermined value both ends of the primary winding 56, of the transformer 23, are at the 3 will be unenergized, and the tubes 21 and 22 will be nonconductive. I

The reactor 53 comprises a three-leg iron core 80 having the winding 63 disposed on the two outer legs in such relation that there is no flux in the center leg when the winding 63 is energized. The reactor 53 is designed to have low impedance, and its function is to prevent hunting of the regulator, as hereinafter described.

The operation of the embodiment of my invention illustrated in Fig. l is as follows:

When the generator is started, its field poles have such residual magnetism that some voltage will be generated and impressed across the conductors 5 and 6. A small alternating current will flow to the rectifier 8 through the reactor 9, and direct current will be supplied to the field winding 4:.

v The energizing circuit for the rectifier 3 may be traced from conductor 7, through conductor 85, winding 12 on the reactor 9, conductor 86, the rectifier 8 and conductor 87, to conductor 6. The circuit for energizing the field winding 4 may be traced from rectifier 8, through conductor 88, the field winding 4 and conductor 89, to the rectifier 8.

The energization of the field winding 4 causes a further increase in the generator terminal voltage, and more direct current is supplied to the field winding 4, and the generator voltage builds up to slightly above normal voltage.

When load is applied to the generator, the voltage of the generator will tend to fall below its predetermined value and there will be more current flowing through the resistor 25 than through the reactor 24, as may be observed from the curves shown in Fig. 3, and the voltage induced in the secondary winding of the current transformer 62 will be less than the voltage measured from the point 61 on the resistor 25 to the conductor 66. The winding 56 of the transformer 23 will thus be impressed with voltage which will send current from the point 61 on the resistor 25 through the winding 56 and the secondary winding of the current transformer 62. The current flowing through the winding 56 energizes the secondary winding 57, and voltage is impressed on the grid elements 29 and 33 of the tube rectifiers 21 and 22, respectively, thereby rendering them conductive.

When the tubes are conductive, a circuit is established for supplying direct current to the winding 13 of the reactor 9 to saturate the iron core 11. The saturation of the core 11 reduces the effective impedance of the reactor 9, resulting in an increased field current and a rise in the generator voltage.

The energizing circuit for the winding 13 may be traced from the mid-point of the secondary winding 47 of the potential transformer 45, through the half 48 of the winding 47, through conductor 91, the anode 28 and the cathode 27 of the rectifier 21, to the junction point 37, conductor 36, conductor 92, winding 52 on the reactor 53, conductor 93, winding 13 on the reactor 9, conductor 94 to the mid-point of the secondary winding 47 of the potential transformer 45.

When the alternating-current wave reverses, the circuit extends through the other half 49 of the winding 47 of the potential transformer I 45, through conductor 65, the anode 32 and the cathode 31 of the rectifier 22 and the circuit is completedthrough the winding 52 on the reactor 53, and the winding 13 on the reactor 9, as hereinbefore described.

When the voltage of the generator reaches its predetermined value, the both ends of the primary winding 56 of the transformer 23 are again at the same potential and there is no voltage impressed on the grid elements of the tubes 21 and 22, and they cease to be conductive. When the tubes become non-conductive, the energization of the winding 13 is reduced, thereby increasing the impedance of the winding 12 and decreasing the excitation of the field winding 4.

The generator voltage will again fall and cause the tubes to become conductive, again causing an increase in the field current. This cycle is repeated at a high rate of speed, thereby maintaining substantially constant voltage at the generator terminals.

The excitation of the field winding 4 is rapidly varied between predetermined minimum and maximum values, the average value of excitation being proportional to the ratio of the time the tubes 21 and 22 are conductive to the time that they are non-conductive.

Since the increase in the field excitation is dependent upon the length of time that the tubes are conductive, the regulation of the generator is independent of the characteristics of the tubes. Should the internal impedances of the tubes vary for any reason they will still remain effective to control the voltage, by remaining conductive for longer or shorter intervals as may be required to raise the generator voltage to the desired value.

When the iron core 11 of the reactor 9 is saturated, the voltage of the generator will lag behind the increase in voltage applied to the field winding 4 due to the inductance of the,

on the alternating flux produced by the winding 63, thereby saturating the core 80. The saturation of the core reduces the impedance of the winding 63, thereby so increasing the current flowing through the circuit of the reactor 24 that the voltage induced in the secondary winding of the current transformer 62 is equal to the voltage between the point 61 on the resistor 25 and the conductor 66 at a lower voltage on the conductors 5, 6 and 'i. The curve of voltage induced in the secondary winding of the current transformer 62 plotted against the generator voltage will then assume a different shape, as illustrated by curve E in Fig. 4, which will intercept the curve D at a lower point.

The both ends of the winding 56 of the transformer 23 are again at the same potential, thereby rendering the tubes 21 and 22 non-conductive somewhat before the generator voltage reaches its predetermined value. The characteristic time lags in the reactor 9 and the field winding 4 will, however, cause the current in the field winding 4 to continue to increase for a short time after the tubes 21 and 22 have become non-conductive thus causing the generator voltage to come to its predetermined value without over-shooting.

Referring to Fig. 5 of the drawings, the rectified current for energizing the generator field winding 4 and the winding 13 on the reactor 12 is derived from supply conductors 102 and 103 that are energized from a generator 104. The generator 104 comprises an armature winding 105, that is connected to the conductors 102 and 103, and a field winding 106. The generator 104 is mounted on the same shaft as the generator 2, in order that the voltage across the conductors 102 and 103 shall be in synchronism with the voltage across the conductors 6 and 7.

Alternating-current voltage is impressed across the anode and cathode of each tube 21 and 22, by a potential transformer 107, the primary winding 108 of which is energized from the conductors 102 and 103. The secondary winding is divided into two sections, 109 and 110, by a tap connection, and is connected to the anodes 28 and 32 of the tubes 21 and 22, respectively, similarly to the transformer 45 of Fig. 1 to give full-wave rectification and energize the winding 13 of the reactor 9 uni-directionally when the tubes are conductive.

Two potential transformers, 112 and 113, are provided for impressing voltage across the resistor 25 and the reactor 24 and are connected to the conductors 5, 6 and '1 and to the resistor and the reactor similarly to the transformers 45 and '74 of Fig. 1.

The operation of the embodiment of my invention, illustrated in Fig. 5, is similar to the operation described for the embodiment illustrated in Fig. 1.

It will be evident from the above description that I have provided a regulator system for maintaining the voltage of an alternating-current generator substantially constant, that has no moving elements, that is quickly responsive to changes in the generator voltage and that will not be subject to hunting.

Since many modifications may be made in the apparatus and circuits illustrated without de parting from the spirit of my invention, I do not 'wish to be limited otherwise than by the scope of the appended claims.

I claim as my invention: 1. In combination, a generator having a field winding, an alternating-current supply, rectifying means for exciting said field winding from the supply, means for controlling the value of said excitation comprising a variable reactor connected in circuit with the rectifying means. means including thermionic means for superposing a uni-directional flux on said reactor to vary the effective impedance thereof, and means responsive to variations in the generator voltage for rendering the thermionic means conductive when the generator voltage is below a predetermined value and non-conductive when the gem erator voltage is above the predetermined value, the value of the uni-directional flux being proportional to the length of time that the thermi onic means are conductive.

2. In combination, an alternating-current generator having a field winding, a regulator system for controlling the voltage of said generator com prising an alternating-current supply, a rectifier connected to energize the generator field winding from said supply, an iron-core reactor connected in series-circuit relation to the rectifier, means including thermionic tubes for varying the effective impedance of the reactor to vary the generator field current, means responsive to variations in generator voltage for rendering the tubes conductive when the generator voltage is below a predetermined value and non-conductive when the generator voltage is above said predetermined value comprising a resistor and an iron-corereactor connected in parallel-circuit relation and energized from the generator, a tube-control transformer that is energized in response to the changes in the currents flowing through the resistor and the second named reactor which are occasioned by changes in the voltage of the generator, said resistor and the second named reactor having such characteristies that the transformer is unenergized when the generator voltage is at the predetermined value.

3. In combination, an alternating-current generator having a field winding, a regulator system for controlling the voltage of said generator comprising an alternating-current supply, a rectifier connected to energize the generator field winding from said supply, an iron-core reactor connected in series-circuit relation with the rectifier, means including thermionic tubes for varying the effective impedance of the reactor to vary the generator field current, means responsive to variations in generator voltage for rendering the tubes conductive when the generator voltage is below a predetermined value and non-conductive when the generator voltage exceeds the predetermined value, said means comprising a resistor and an iron-core reactor energized from the generator output circuit and connected in parallel-circuit relation, means for bringing the current flowing through the resistance in phase with the current flowing through the second named reactor, a transformer energized in accordance with the changes in the currents flowing through the resistor and the second named reactor which are occasioned by changes in the generator voltage for controlling the operation of the tubes, the second named reactor and the resistor having such characteristics that the transformer is unenergized when the generator voltage is at the predetermined value.

4. In combination, an alternating-current generator having a field winding, a regulator system for controlling the voltage of said generator comprising an *altemating-current supp y, a rectifier for energizing the field winding from said supply, an iron-core reactor having a main winding and an auxiliary winding, the main winding being connected in series-circuit relation with the rectifier, a plin'ality oi thermionic tubes for energizing the auxiliary winding of the re= actor from said supply to vary the impedance of the reactor and thereby vary the generator excitation, each tube comprising an anode, a cathode and a grid, means responsive to variations in the generator voltage for impressing voltage upon the grids when the voltage of the generator is below a predetermined value to render the tubes conductive and to alter the grid voltage to render the tubes non-conductive when the generator voltage exceeds the predetermined value, the average value of generator excitation being determined by the ratio of the time the tubes are conductive to the time that they are non-conductive.

5. In combination, an alternating current generator having a field winding, a regulator eye tem for controlling the voltage of said generator comprising an alternating-current supply, a rectifier for energizing the field .winding from said supply, an iron-core reactor having a main winding and an auxiliary winding, the main winding being connected in series-circuit relation with the rectifier, a plurality of thermionic tubes for energizing the auxiliary winding of the reactor from said supply to vary the impedance of the reactor and thereby vary the generator excitation, each tube comprising an anode, a cathode and a grid, means responsive to variations in the generator voltage for impressing voltage upon the grids when the voltage of the generator is below a predetermined value to render the tubes conductive and to alter the grid voltage to render the tubes non-conductive when the generator voltage exceeds the predetermined value, the average value of generator excitation being determined by the ratio of the time the tubes are conductive to the time that they are non-conductive, and anti-hunting means associated therewith.

6. In combination, an altemating-current genorator having a field winding, a regulator system for controlling the voltage of said generator comprising an alternating-current supply, a rectifier connected to excite said field winding from said supply, an iron-core reactor having a main winding and an auxiliary winding, the main winding being connected in series-circuit relation with the rectifier, thermionic means for energizing the auxiliary winding by direct current to vary the impedance of the reactor and thereby vary the generator excitation, means responsive to variations in the generator voltage for rendering the thermionic devices conductive when the generator voltage is below a predetermined value and non-conductive when the gem orator voltage is above the predetermined value, said means comprising a resistor and anironcore reactor connected in parallel-circuit relation and energized from the generator output circuit, and anti=hunting means associated therewith comprising an iron-core reactor con nected in series-circuit relation with the second named reactor, saturating means associated with the last named reactor and means for energizing the saturating means when the thermionic means are conductive.

7. In combination, an alternating-current generator having a field winding, a regulator systern for controlling the voltage of said generator comprising an alternating-current supplyin syncinonism with the generator voltage, a rectifler connected to excite the field winding from said supply, an iron-core reactor having a main winding and an auxiliary winding, the main winding being connected in series-circuit relation with the rectifier, thermionic means for energizing the auxiliary winding from said synchronous supply to vary the impedance of the reactor and thereby vary the generator excitation, and means responsive to the variations in generator voltage for rendering the thermionic means conductive when the generator voltage is below a predetermined value and non-conductive when the generator voltage is above the predetermined value.

CHARLES P. WEST.

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