US2464567A - Regulator system - Google Patents

Description

March 15, 1949. A. FISHER 2,464,567

REGULATOR SYSTEM Filed Sept. 16, 1944 Fig.5.

CURRE/V 7' Invent or: Alec Fi sher,

by 29247 His Attorney.

Patented Mar. 15, 1949 uNmzo sTATEs\ PATENT omen 2.464.567 REGULATOR. SYSTEM Alec Fisher, Lynn, Mass, assignor to General Electric Company, a corporation of New York Application September 16, 1944, Serial No. 554,426

7 Claims. (Cl. 322-28) This invention relates to automatic regulator systems and more particularly to improvements in static automatic regulator control circuits.

The general problem in almost all kinds of automatic regulation is that of simultaneously reducing the cost and complexity of the, regulating means and at the same time improving its performance. In accordance with this invention there is provided a novel and simple automatic regulator circuit, the control elements of which are static devices, and which has very good regulating characteristics in that it is both fast and sensitive in operation.

An object of the invention is to provide a new and improved regulator circuit.

Another object of the invention is to provide an improved high-amplification fast-acting static automatic regulator control circuit.

The invention will be better understood from Q the following description taken in connection with the accompanying drawing and its scope will be pointed out in the appended claims.

In the drawing, Fig. 1 illustrates diagrammatically a preferred embodiment of the invention; Fig. 2 is a diagram for illustrating the operation of the invention; Fig. 3 is another diagram for illustrating the operation of the invention; Fig. 4 is a modification of Fig. 1, and Figs. 5 and 6 are modified ways of preventing exciter polarity reversal.

Referring now to the drawing and more particularly to Fig. 1, the invention is shown therein, by way of example, as applied to the regulation of the voltage of an alternating-current generator I which is provided with a direct-current field winding 2. This winding is energized by an exciter-armature 3. The exciter may either be a conventional construction or it may be an amplidyne-generator, as described in Patent 2,227,922, granted January 7, 1941, on an application of M. A. Edwards and E. F. W. Alexanderson and assigned to the same assignee as this application. The exciter is provided with a series field winding l for supplying a substantial amount of selfexcitation for said exciter so causing it to build up voltage rapidly and to a high ceiling value.

The voltage oi. the exciter-armature 3 is regulated in accordance with the voltage or the alternator I so as to maintain constant alternator voltage by means of a pair of opposed separatelyexcited field windings 5 and 8, winding 5 being a differential winding which acts in oppositon to the series sell-exciting winding 4 and winding 6, being a cumulative winding, acts in the same direction as the serieswinding 4. The energization 2 of the difierential winding I is made nonlinearly responsive to alternator voltage by means of a nonlinear element oi any suitable type. the preferred device being a saturating reactor I. A full-wave rectifier 8 has its input terminals connected across the output terminals of the alter- "nator I through the saturating reactor I and the output terminals of the rectifier are connected to energize the difierential field winding 5. The cumulative field winding 8 is linearly responsive to the voltage of the alternator I and is connected across the output terminals of the alternator through a full-wave rectifier 9.

In order to improve the operation of the system a capacitor III is connected in shunt circuit relation with the differential field winding 5. This capacitor reduces the effective impedance of the differential winding 5 because it offers a relatively low impedance to relatively high frequency harmonies or pulsations in the output current of the rectifier 0 which are the result of saturation of the core of the reactor I. In this manner substantially all of the alternator voltage appears across the reactor I and only a very small fraction of it appears across the input terminals of the rectifier so that current in the differential field winding 5 is made very responsive to variations in efiective reactance of the reactor I.

For manually controlling the voltage setting of the system and for minimizing the danger of polarity reversal of the exciter-armature 3 a rheostat II is connected in shunt circuit relation with the series field winding 4. This also reduces the tendency of the system to hunt.

Referring to Fig. 2, the operation of Fig. 1 is as follows: Curve I2 represents the relation between the voltage of the exciter-armature 3 and the ampere turns of its excitation and is known as its magnetization curve. Assuming no residual voltage, which in most ordinary cases is relatively small, the voltage is zero when the exciting am pere turns are zero and as the ampere turns increase. the voltage increases, the relation being fairly linear until the region near the point I3 is reached. This corresponds to the knee of the,

that the exciter-armature voltage is higher than the resistance voltage drop in its circuit between zero or origin of these lines and their intersection at point I! so that the series excitation characteristic of the exciter is such that it builds up voltage to point ll.

The effect of the cumulative field winding 6 is to add positive ampere turns to those of the series field winding i and if. these positive ampere turnsof the cumulative winding are represented by the arrow IS, the effect is to shift the resistance characteristic parallel to itself and to the right from to 0' so that the exciter voltage will now build up to the point it? corresponding to the intersection point of curve 92 and the displaced resistance characteristic l@', and, as will be seen, this will produce much higher exciter voltage and consequently a much higher value of excitation of the alternating-current generator. The differential ampere turns of the field winding of course act in the opposite direction to those of the cumulative winding and thus tend to displace the resistance characteristic toward the left. However, the differential ampere turns are very sensitive to slight variations in alternating-current generator voltage because of the saturating reactor ll whose characteristic is illustrated in Fig. 3. In this figure the curve 20 represents the relation between the voltage of the alternating-current generator and the current in the reactor and, as will be seen, it corresponds in shape to the saturation curve of iron which is the material of which the reactors core is made. The reactor is so designed that it saturates very early in each cycle of alternating= current generator voltage so that the rated HMS. value of alternating current generator voltage corresponds to a point considerably beyond the bend of the saturation curve and consequently very small variations in voltage across the reactor will produce very large variations in current through the reactor. Thus we can say that ii Vin. and VFL correspond respectively to no load and full load values of alternating-current generator voltage which are very close together, nevertheless the corresponding values of reactor current represented by the distance between the origin of the curve and points 28 and 22 will be relatively large. Therefore, the differential ampere turns of the exciter will vary in proportion to variations in reactor current whenever the main generator voltage varies and by making the differential ampere turns at no load onthe main generator equal to the length of the arrow 23 and the differential ampere turns at full load equal to the length of the arrow 24 the alternator voltage between full load and no load will not vary very much between the difference between Vm. and Vm. in the exciter-armature 3. Thus the differential ampere turns represented by the arrow 23 will shift the exciter resistance characteristic to the left from E6 to IE" which, as shown passes through the. point H on the exciter magnetization characteristic corresponding to the required excitation of the alternator at no load. Similarly, the differential ampere turns represented by the arrow 24 will shift the resistance characteristic from I 6 to l8' and this. as will be seen, can pass through the point II corresponding to the required exciter voltage for giving constant alternator voltage at full load. By'designing the exciterso that itsma'gnetization characteristic is substantially a straight line below saturation and substantially parallel to its resistance characteristic the accuracy of the regulator system may be made almost anything desired because the closer these two lines come to parallelism the smaller the change in voltage across the reactor than is necessary to maintain constant alternating-current generator voltage.

Fig. 2 shows that at the value of load intermediate no load and full load the differential ampere turns will equal cumulative ampere turns so that the exciter will operate almost entirely self-excited and at, say, the point ll corresponding to the intersection between its magnetization curve and its undisplaced self-excited resistance characteristic. Although it may seem at first glance that the cumulative and 'diiferential ampere turns substantially cancel each other and therefore all that would be necessary is to have separately excited control ampere turns equal to the difference between the cumulative and dihferential ampere turns, this is not entirely true for the following reasons. In the first place, the differential ampere turns need to change only a relatively small amount with respect to their average value in order te cover the entire range of regulation. In other words, the difference between arrows 23 and 25 is small compared to the length oi either. one of them so that in this manner the regulation is made very sensitive and in effect a further amplification is added to the regulator system over and above the amplifications resulting from the saturation of the reactor and from the exciter itself. In the second place a sudden dip in alternator voltage of only a slight amount will practically cause the difierential ampere turns to disappear without appreciably reducing the cumulative ampere turns so that almost instantaneously the full voltage restoring ability represented by the vertical difference between the curve i2 and the resistance characteristic [15' will be available for quickly restoring the excitation and voltage of the alternating-current generator.

Some transients and surges oi. the circuit of the main generator may tend to reverse the current in the series field winding 4 which of course would be undesirable as the series machine would then tend to build up with reverse polarity. However, the resistor ll will tend to prevent this because the inductance of the series field winding will tend to force most of such transient or surge currents through the resistor ll where they will do no harm in that they will not flow through the series field winding 4 and consequently will not tend to reverse its xcitation.

In the modification shown in Fig. 4 the two opposing field windings 5 and 6 are combined into a single field winding 25 which has impressed on it the difference between the voltages across resistors 26 and 21, which voltages correspond respectively to the cumulative and differential components of the required amount of separate excitation in that these resistors carry the output currents of the rectiflers 8 and 9. In this manner one field winding 25 replaces the two field windings I 8 andtoifig. 1. Inadditionaimidirectional conductor I may be connected across the exciterarmatureinsuchadirecticnastoblockthefiowoi current when the exciter has normal polarity and to short-circuit the exciter when it has reverse polarity. This is another way of preventing the exciter-armature from reversing its polarity. The operation of Fig. 4 is otherwise the same as that of Fig. 1.

In the modifications shown in Figs. 5 and 6 a small difi'erential series field winding 2! is provided on the exciter and is connected eflectively in parallel with the main series field winding i'or theexciter. Separate unidirectional conductors 80 and II are connected in series with both field windings so as to prevent normal current to fiow only through the main field winding and to per- 'mit reverse current to fiow only through the dif-' ierential series field winding. In this manner any surge or transient tending to reverse the exciter-armature current will result in no reversal oi' exciter-ampere turns because the reverse current flowing through the diilerential series field will produce ampere turns with the same polarity as normal current flowing through the normal series field. I g While there have been shownand described particular embodiments of this *invention, it

be obvious to those skilled in the that various changes and modifications can be'made therein without departing from the invention and thereiore it is aimed in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent oi the United Btateaisf? a 1 1. In combination, a main generator having a v Q a series field winding for preventing polarity reversal of said exciter.

3. In combination, a generator having a field winding, means for varying the current in said field winding in such a manner as to maintain an operating condition of said generator substantially constant comprising an exciter-armature connected to energize said field winding, a series field winding for said exciter for supplying a substantial amount of self-excitation for said exciter, a diiTerentially-acting separately-excited field winding for said exciter, means for energizing said 'diiIerentially-acting field winding ndnlinearly with variations in said operating condition in such a manner that the current in said difierentially acting field winding varies much more than in direct proportion to variations in said operating condition, and means for preventing polarity reversal of said exciter-armature,

- ponent of excitation for said exciter, a differfield winding, an exciter with series "self-excita-' tion connected to energize said field winding, the resistance characteristic of the armature circuit of said exciter having a greater slope than that of a straight line passing through the points on the magnetization characteristic of the exciter corresponding to the values of main generator excitation at full load and no load with normal main generator voltage, means for providing said exciter with separate excitation derived from the voltage of said main generator,--said. separate excitation having opposing cumulative and difierential components, means for causing said-difterential component to vary much more than in direct proportion to variations in said voltage, and means for preventing polarity reversal of said exciter. A

2. In combination, a main generator having a field winding; an exciter connected to energize said field winding, the magnetization characteristic of said 'exciter being suchth'at it is substantially a straight line between the values corresponding to full load and no load constant voltage operation of said main generator, said exciter having a series self-excited field'winding, the resistance characteristic of the armature circuit of said exciter being-substantially parallel to said substantially straight line portionof the magnetization characteristic of the exciter, means for providing said exciter with separate excitation derived from the terminal voltage of said main generator, said separate excitation having opposing, cumulative and differential components, means for causing said differential'component to vary much more than in direct proportion to variations in said main generator voltage, and means including a variable resistance shunted across said en-tially-acting separately-excited field winding for said exciter, means forenergizing said difi'erentially-acting field winding nonlinearly with variations in said generator voltage in such a manner that the current in said diiIerentially-acting field winding varies much more than in direct proportion to variations in said generator voltage, and means for preventing polarity reversal of said exciter-armature, said means including a variable resistance shunted across said series winding to oifer reverse current a path having relatively low resistance compared with the high impedance path through said series winding.

5. In combination, a generator having a'field winding, means for varying the current in said field winding in such a manner as tomaintain the voltage or said generator substantially constant comprising an exciter-armature connected to energize said field winding, a series self-exciting field winding for supplying the main component of excitation for said exciter,. a diflerentially-acting separately-excited field winding for said exciter, means for energizing said difierentially-acting field winding nonlinearly with variations in said generator voltage in such a manner that the current in said diflerentially-acting field winding varies much more than in direct proportion to variations in said generator voltage,

and a resistor connected in shunt circuit relation with said series field winding for offering reverse current a low resistance path compared to the high impedance path through said series winding thereby preventing polarity reversal of said exciter-armature. 6. In combination, an alternating-current generator, a field winding for said generator, a direct-current exciter connected to energize said field winding, said exciter having a series selfexciting field winding for providing a base component of exciting flux for said exciter, a separately-excited difierential field winding for said exciter, a full-wave rectifier having output ter- .entlal field winding, a saturating reactor, means (or connecting the input terminals of said recing for said exciter, a full-wave rectifier connected between the terminals of said alternating-current generator and said cumulative field winding for energizing said cumulative field winding with direct current which is directly linearly proportional to the voltage of said alternating-current generator, and means for preventing polarity reversal of said exciter including a variable resistance connected in shunt circuit relation with said series field winding to offer a low resistance path to reverse current thereby efiectively to short circuit the high impedance path through said series winding and prevent polarity reversal of said exciter.

7. In combination, an alternating-current generator, a field winding for said generator, a directcurrent exciter connected to energize said field winding, said exciter having a series self-exciting field winding for providing a base component of exciting flux for said exciter, a separately-excited diflerential field winding for said exciter, a fullwave rectifier having output terminals connected to the terminals of said differential field winding, a saturating reactor, means tor connecting the input terminals of said rectifier across the output tifier across the output terminals of said alternat- --ing-current generator through said saturating reactor, a cumulative separately-excited field windterminals of said alternating-current generator through said saturating reactor, a capacitor connected in shunt circuit relation to said differential field winding for by-passlng therefrom high irequency harmonics resulting from the saturation of said reactor, a cumulative separately-excited field winding for said exciter, a full-wave rectifier connected between the terminals of said alternating-current generatorand said cumulative field winding for energizing said cumulative field winding with direct current which is directly linearly proportional to the voltage of said alternating-current generator, and means for preventing polarity reversal of said exciter including a variable resistance connected in shunt circuit relation with said series field winding to offer a low resistance path to reverse current thereby eflectively to short circuit the high impedance path for reverse current through said series winding so preventing polarity reversal of. said exciter.

ALEC FISHER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,234,747 Crever Mar. 11, 1941 2,247,166 Edwards June 24, 1941 2,335,784 Montgomery et a1. Nov. 30, 1943

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