US2328464A - Regulating circuit - Google Patents

Description

Aug. 31, 1943. o. Km@ 2,328,464

REGULATING CIRCUIT Filed NOV. 30, 1959 Inventur: OT- deem Ki Ibi e H is Abtornefg.

Patented Aug. 3l, 1943 REGULATING CIRCUIT Ordean Kiltie, Fort Wayne, Ind., asslgnor to General Electric Company, a corporation of New York Application November 30, 1939, Serial No. 306,918

18 Claims.

This invention relates to regulating circuits and more particularly to a new and improved constant voltage transformer.

By a constant voltage transformer I mean an electric circuit arrangement which automatically maintains substantially constant output voltage, with or without variations in output current, when it is energized by a variable voltage supply circuit. It may transform the supply Voltage to either a higher or a lower output voltage or the output voltage may be made equal to the nominal supply circuit voltage.

My invention is particularly Well adapted for use with nominally constant voltage alternating current supply circuits, such for example as ordinary house lighting circuits which have a nominal voltage rating of 115 volts or thereabouts and Whose voltage in many cases fluctuates plus or minus 8 or 10 per cent for a number of wellknown reasons. There are many load devices which for best operation require a substantially constant voltage, by which is meant a voltage which does not vary as much as plus or minus 1 per cent when the load varies all the Way from no load to full load. Examples of such devices are many pieces of laboratory apparatus, certain vacuum tube grid circuits, comparison type photometers, and light and sound recording apparatus.

In accordance with my invention I combine means for converting the variable supply voltage to a constant current with means for converting the constant current to a constant voltage which is independent of current variations.

An object of my invention is to provide a new and improved constant voltage transformer.

Another object of my invention is to provide a new and improved automatic electrical regulatv ing circuit.

My invention will be better understood from 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. l illustrates diagrammatically a simplified or equivalent circuit of a preferred form of my invention which uses no moving parts, Fig. 2 illustrates the operating characteristic of the variable voltage to constant current converting portion of Fig. l, Fig. 3 illustrates the operating characteristic of the constant current to constant potential converting portion of Fig. l, Fig. 4 illustrates a particular magnetic core punching which is suitable for use with both the variable voltage to constant current and the constant current to constant voltage converting portions of the circuit shown in Fig. 1, Fig. 5 illustrates the magnetizing characteristic of a core made up of the punching shown in Fig. 4, Fig. 6 illustrates a modification of Fig. 1, Fig. 7 illustrates another modification of the variable voltage to constant current converter, Fig. 8 illustrates the operating characteristic of the modification shown in Fig. 7, and Fig. 9 is a modification employing a `.so-called constant current regulating transformer as the variable voltage to constant current converter and employing a monocyclic network as the constant current to constant voltage converter.

Referring now to the drawing and more particularly to Fig. 1, there is shown therein a supply circuit l and a load circuit 2 which are interconnected by two elements A and B. The supply circuit is one whose voltage is variable and the load circuit is one whose load is variable and Whose Voltage is to be maintained constant regardless of variations of supply voltage and variations of load current. Element A consists of a reactor 3 connected in parallel with a capacitor 4 and, as will be explained hereafter by reference to Fig. 2, this arrangement automatically maintains constant current in the element B.

The element B comprises a reactor 5 which, as

will be explained hereafter by reference to Fig. 3, automatically maintains substantially constant output voltage on circuit 2. Both reactors 3 and 5 are provided with magnetic cores, at least portions of which are magnetically saturated during normal operation of the circuit. These cores may be made of any suitable material, either ordinary transformer core iron or special magnetic materials, such as Permalloy or Mu-metal which have unusually sharp bends in their magnetization curves.

The operation of Fig. 1 can best be understood by reference to Figs. 2 and 3. Referring first to Fig. 2, the volt-ampere characteristic of the reactor 3 is illustrated by the curve 3 and the voltampere characteristic of the capacitor 4 is illustrated by the straight line 4. Curve 3' is relatively steep at low values of current and voltage but at an intermediate value of current and Voltage it bends, becoming a relatively straight line which is flatter than the first part of the characertistic. This bend is caused by magnetic saturation in the core. The capacitor 4 is so proportioned that its volt-ampere characteristic 4 is parallel to the'volt-ampere characteristic of the reactor over its substantially straight line portion beyond the knee of its curve. This portion extends over the range of voltage varia.-

tions of the supply circuit and is indicated on Fig. 2 as the range between V1 and V2. Over this voltage range the difference between the capacitor current I: and the reactor current I1 is constant by reason of the parallelism of the two vclt-ampere characteristics. As the capacitor and reactor currents are substantially in phase opposition with each other the total or resultant current flowing through these two elements will be the diierence between their individual currents and consequently this resultant will be constant over the range of supply voltage variations. It is to be noted that throughout the constant current range of element A the capacitor current is greater than the reactor current so that the current drawn by element A. from the supply circuit is a leading current. This leading current is desirable as it neutralizes the lagging current taken by inductive devices such as motors or transformers which may also be connected to the suppiy circuit.

In Fig. 3 the volt-ampere characteristic of the reactor is shown by the line 5. This characteristic is similar in general shape to that of curve 3' but it is made much flatter or more nearly parallel to the current axis after the knee of the curve has been passed. This extreme flatness may be secured by the use of suitable core material or by suitable core construction, one example oi which will be described hereafter in connection with Figs. 4 and 5. As the constant output current of element A divides between the reactor 5 and the load circuit 2, the reactor current will be the difference between the load current and the constant output current of device A. The element B is so designed that at full load on the output circuit the current in the reactor willbe sufiicient to operate the .reactor at the point on its characteristic correby the diierence between the voltages V2 andv V3 corresponding to full load and no load respectively.

The above description of Fig. 3 has assumed that the load current and current in reactor 5 are in phase with each otherbecause this is the worst condition from the standpoint of voltage variation. If the load current is out of phase with the reactor current these currents will combine vectorially to equal the constant current output of device A and consequently load changes of the same magnitude will produce smaller changes in the current in the reactor 5 and consequently smaller voltage variations across the load circuit. For example, if a given load change whose current is in phase with the reactor current varies the reactor current 50 per cent the same load change whose power factor is in quadrature with the reactor current will only change the reactor current about 14 per cent.

In Fig. 4 there is illustrated a magnetic core composed of alternately reversed E-shaped laminations 6 which is suitable for use with both reactors 3 and 5 although, of course, the number of laminations used in the cores of reactors 3 and 5 will not necessarily be the same. Laminations 6 are provided with a bridged air gap 6', that is to say, the central leg has a window cut in it providing in effect a restricted section of the core i which saturates prematurely, thereby causing some of the ilux to traverse the air gap so that in eiect the arrangement is that of a bridged air gap.

Fig. 5 shows the volt-ampere characteristic of a reactor having a core composed of lamlnations 6. This characteristic has two bends, one of Vi and the second of V2. The first bend occurs when the restricted section saturates and the second bend occurs when the main body of the core saturates. In between these two bends the reactor has substantially the straight line characteristic of an air core reactor because the additions to the iiux in the device are passing through an air gap in parallel with the saturated restricted section. The straight line part of the characteristic, however, is diierent from that of an air core reactor in that it is off-set and does not pass through the origin of coordinates. This oi-set is caused by the flux required to saturate the restricted section. When the second bend occurs the curve of course becomes still flatter and by suitable design may be made sub` stantially parallel to the current or magnetizing axis. Thus, by operating the core of reactor 3 over the straight line portion between the two bends the constant current characteristic as explained in connection with Fig. 2 is obtainable,vwhile by operating the reactor 5 beyond the second bend the substantially constant output voltage characteristic explained by Fig. 3 may be obtained.

It will be noted that the current in the reactor 3 will often exceed the constant current output of arrangement A and consequently will usually exceed the current in the reactor 5. However, by making the number of turns of reactor 5 greater than the number of turns of reactor 3 the ampere-turns or magnetizing effect in reactor 5 may be made much greater than that in reactor 3 so that the core of reactor 5 will be operated beyond the second bend of its characteristic. Another way of obtaining the same result is to use fewer laminations in the core of reactor 5 than are used in the core of reactor 3.

In Fig. 1 the reactors 3 and 5 may be considered as autotransformers having a 1 to 1 ratio. However, it is often desirable to have the reactor 3 operate at a higher voltage than the reactor 5 so as to use a smaller and less expensive capacitor. Similarly, the output voltage should sometimes be diierent from the voltage across the reactor 5. To this end the modification shown in Fig. 6 utilizes a voltage step-up autotransformer 'l for the reactor 3 and a step-down autotransformer 8 for the reactor 5. This arrangement, however, is basically the same as the arrangement shown in Fig. 1 and the secondary currents of the autotransformers when referred to their primary circuits bear the same relation to the magnetizing currents of the transformers as are shown in Figs. 2 and 3 between the reactor currents and the capacitor and load currents.

Furthermore, it is not essential to my invention that the capacitor 4 and load circuit 2 be conductively connected to their associated reactors or autotransfomer primary windings and they can be inductively coupled thereto as by the use of conventional insulating transformers if desired. However, in each such case the relation between the magnetizing current of the primary winding o1' the inductive elements of A and B will bear the same relation respectively to the effective capacitor and load currents when referred to the primary sides of the transformers as are shown in Figs. 2 and 3 for the reactor magnetizing currents, capacitor current and load current.

A way of controlling the shape of the volt-ampere characteristic of the reactor 3 beyond its ilrst bend is shown in Fig. 7.' This consists of splitting up the reactor into an iron core reactor 8 and an air core reactor I0. The iron core reactor may, for example, have an iron core with very low leakage flux and a sharp saturation knee, As shown in Fig. 8. the characteristic of the reactor 9 is shown by curve 9' while the volt-ampere characteristic of the air core reactor ID is shown by the straight line I. These two devices being in series, they carry the same current and the voltage across the two is the sum of their individual voltages which is represented by the solid curve II. This curve is steeper than the curve 9' by reason of the addition of the voltage of the air core reactor I0 so that a given variation in supply voltage will not produce as great a current change in the combination of reactors 9 and IU as it would in reactor 9 alone so that the danger of overloading the reactor on high'voltage surges of the supply voltage is minimized. At the same time a smaller capacitor, that is to say, one having a lower value of capacitance and therefore a higher value of capacitive reactance will be used to obtain a capacitor volt-ampere characteristic paralleling the straight portion of curve II than would be necessary in order to parallel the straight portion of the characteristic 9'.

In the modification shown in Fig. 9 the variable input voltage is converted to constant curn rent by means of a conventional constant current regulating transformer I2. This device depends for its operation on the repulsion between the primary and secondary windings of the transformer, the secondary winding being movable and being partially counterbalanced by a weight W. The secondary winding ofy the transformer is connected to the input terminals of a monocyclic network I3 whose output terminals are connected to the load circuit 2. The monocyclic network shown is usually referred to in the art as a monocyclic square, it consisting of two reactors and two capacitors connected to form a Wheatstone bridge circuit arrangement. Such circuits have the wellknown property of converting a constant current input to a constant potential output.

From the above description it will be seen that my invention solves the problem of obtaining constant voltage output with varying output current from a variable voltage input or supply circuit by performing this regulation in two interdependent but separate and distinct steps, namely, converting from variable input potential to constant current and then converting from the constant current to constant potential with varying current.

While there have been. shown and described particular embodiments of this invention, it will be obvious to those skilled in the art that various changes and modifications can be made therein without departing from the invention and, therefore, 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. Y

What I claim as new and desire to secure by Letters Patent of the United States is:

1. Apparatus for converting a variable supply voltage to a constant output voltage which is substantially independent of output current comprising, in combination, a pair of transformers having their primary windings serially connected in a circuit across which said supply voltage is to be applied, one of said transformers having a capacitor connected across its secondary winding and the other transformer having a secondary winding for supplying said output voltage, both of said transformers having cores built up of identical laminations which are provided with restricted sections whereby their magnetizing characteristics have a first bend where the restricted sections saturate and a second bend where vthe main cores saturate, said characteristics being substantially a ,straight line between said bends and a substantially straight line beyond said second bend, the turns of the primary winding of the transformer across whose secondary winding said capacitor is connected being of such a number that over the range of supply vvoltage variations itsv arnpere turns magnetize its core in the straight line range between said two bends, said capacitor having a volt-ampere characteristic which is parallel to the portion of the magnetization characteristic of the core of the transformer across Whose secondary winding it is connected which is between the two bends of said magnetization characteristic when the coordinates of said magnetization characteristic are the voltage across and the current through the primary winding of saidtransformer, the turns of the other primary winding being of such number that over the range of the output current of the secondary winding associated therewith the core magnetized thereby is operated beyond the second bend of'its magnetization curve.

2. Apparatus for converting a Variable supply voltage to a constant output voltage which is substantially independent of output current comprising, in combination, a pair of saturable core reactors across one of which said output voltage is to be obtained serially connected in a circuit across which. said supply voltage is to be applied, a Capacitor connected across the `other reactor, said other reactor having the portion of its voltampere characteristic which corresponds to the range of said supply voltage variations a substantially straight line which is parallel to the voltarnpere characteristic of said capacitor whereby the difference between the currents in said other reactor and capacitor is constant over the range of said supply voltage variations, the reactor across which said output voltage is obtained having a volt-ampere characteristic which is substantially parallel to its current axis over the range of output current variations.

3. In combination, a normally relatively variable voitage alternating current supply circuit7 a normally relatively constant voltage variable alternating current load circuit, and a voltage regulator directly interconnecting said circuits, said regulator comprising a 'variable alternating voltage to constant alternating current converter connected directly through conducting means having negligible impedance and negligible losses to supply constant alternating current to a constant alternating current to constant alternating voltage converter across which said load circuit is connected. f

4. In Combination, a relatively Variable voltage alternating current supply circuit, a relatively constant voltage variable alternating current load circuit, and a voltage regulator interconnecting said circuits, said regulator comprising a static variable alternating voltage to constant alternating current converter connected through conducting means having negligible impedance and negligible losses to supply constant alternating current to a constant alternating ,current to constant alternating voltage converter across` rent to constant voltage converter including an iron core reactor having an operating characteristie which is substantially a straight line over its normal operating range by virtue of magnetic saturation in its core.

6. In combination, a normally relatively variable voltage alternating current supply circuit, a

normally relatively constant voltage variable alternating current load circuit, and a voltage regulator directly interconnecting said circuits, said regulator comprising a variable alternating voltage to constant alternating current converter connected directly to supply constant alternating current to a constant alternating current to constant alternating voltage converter across which said load circuit is connected, said variable voltage to constant current converter including a capacitor and a parallel connected iron core reactor having an operating characteristic which is substantially a straight line over its normal operating range by virtue of magnetic saturation in its core, said capacitor having a characteristic which is parallel to said straight line.

7. In combination, a normally relatively variable voltage alternating current supply circuit, a normally relatively constant voltage variable alternating current load circuit, and a voltage regulator directly interconnecting said circuits, said regulator comprising a variable alternating voltage to constant alternating current converter connected directly to supply constant alterna-ting current to a constant alternating current to constant alternating voltage converter across which said load circuitI is connected, said constant current to constant voltage converter including an iron core reactor having an operating characteristie which is substantially a straight line over its normal operating range by virtue of magnetic saturation in its core, said variable voltage to constant current converter including a capacitor and a parallel connected iron core reactor having an operating characteristic Which is substantially a straight line over its normal operating range by virtue of magnetic saturation in its core, said capacitor having a characteristic which is parallel to said straight line.

8. Voltage regulating power supply apparatus comprising an inductance member having a large exciting current and undergoinglarge changes in exciting current with small changes in voltage within the operating range, means for connecting a utilizing circuit across said inductance member, and a reactance connected in series with said inductance member and a source of alternating current, said reactance consisting of capacity and inductance members connected in parallel with each other, said parallel connected capacity and inductance members individually having voltagecurrent curves which are approximately parallel to each other throughout the operating range.

9. The apparatus of claim 8 in which the inductance member oi' the reactance is an auwtransformer.

10. The apparatus oi claim 8 in which the inductance member of the reactance is a transformer, the primary winding of said transformer being connected in series with the first inductance member and thev source of alternating current, and the secondary winding of said transformer being connected in parallel with the capacity member.

11. Voltage regulating power supply apparatus, comprising a load transformer having a large exciting current and undergoing large changes in exciting current with small changes in voltage Within the operating range, and a reactance connected in series with the primary winding of said transformer, said reactance consisting of capacity and inductance members connected in parallel with each other, said capacity and inductance members individually having voltage-current curves which are approximately parallel to each other throughout the operating range.

12. The apparatus of claim 10 'in which thel inductance member is an autotransformer.

13. 'I'he apparatus of claim 10 in which the inductance member is a. second transformer, the primary Winding of said second transformer being connected in series with the primary winding of the load transformer, and the secondary of said second transformer being connected in parallel with the capacity member.

14. Voltage regulating power supply apparatus, comprising a load transformer having a large exciting current and undergoing large changes in exciting current with small changes in voltage within the operating range, and a reactance connected in series with the primary winding of said transformer, said reactance consisting of capacity and inductance members connected in parallel with each other, said capacity and inductance members individually having voltage-current curves which are approximately parallel to each other throughout the operating range, the values of current in the capacity member exceeding those in the inductance member for the same values of voltage.

15. Voltage regulating power supply apparatus for obtaining substantially constant output voltage with varying conditions of both input voltage and load, comprising a load transformer having a. large exciting current and undergoing large changes in exciting current with small changes in voltage within the operating range, and a reactance connected in series with the primary winding of said load transformer, said reactance consisting of capacity and inductance members connected in parallel with each other, said inductance member comprising a substantially closed core of metal laminations, said core having an air gap therein and at least one leg of said core operating at higher flux density than the other legs, said capacity and inductance members individually having voltage-current curves which are approximately parallel to each other throughout the operating range.

16. A voltage regulator comprising, in combination, a supply circuit, a load circuit connected thereto, constant current impedance means having a resultant variable capacitance characteristic serially connected in said supply circuit, and

constant voltage variable impedance means having a resultant variable inductance characteristic connected across said load circuit.

17. A voltage regulator comprising, in combination, a. supply circuit, a load circuit connected thereto, constant current impedance means having a resultant impedance characteristic of predetermined vectoriai sign serially connected in said supply circuit, and constant voltage variable impedance means having a resultant impedance characteristic of opposite vectorial sign connected across said load circuit.

18. A unitary voltage regulator system comprising, in combination, a substantially variable voltage alternating-current supply circuit, a monocyclic circuit having input and output terminals, a variable Voltage to constant current converter, means having relatively negligible impedance and losses for connecting said converter in series circuit relation with said input terminals across said supply circuit, and a constant voltage variable load circuit connected across said output terminals.

ORDEAN KILTIE.

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