US3199020A

US3199020A - Voltage control device

Info

Publication number: US3199020A
Application number: US122389A
Authority: US
Inventors: Hilker Annamary
Original assignee: Wagner Electric Corp
Current assignee: McGraw Edison Co
Priority date: 1961-07-05
Filing date: 1961-07-05
Publication date: 1965-08-03
Anticipated expiration: 1982-08-03

Description

Aug. 3, 1965 E. B. HILKER 3,199,020

VOLTAGE CONTROL DEvIOE Filed July 5, 1961 #fran/yin,

United States Patent O T his invention relates to electrical control devices and more particularly to voltage control devices employing variable impedances for control.

T he voltage of an electrical system is often controlled or regulated by a tap changing device associated with a tapped winding of a transformer; however, such equipment produces 'abrupt or stepped voltage changes. Variable impedances, such as saturable core reactors, have been used in control devices to vary or regulate voltage in a smooth or stepless manner, but the cost of the impedances, especially when used in hieher voltage systems, has been considerable. Also, some such saturable core reactor control arrangements produce undesirable phase shift etiects because of their reactance, and in many cases, the saturation of the reactor cores produce undesirabiy high harmonic voltages in the system.

lt is therefore a general object of the present invention to provide a voltage control device employing Variable impedances and which substantially avoids or overcomes to a large degree the abovementioned disadvantages.

Another object of the present invention is to provide a variable voltage producing control device employing variable impedances for control and which is especially economical.

Another object is to provide a volt-age control device employing saturable reactors wherein the number of reactors and the cost of each are substantially reduced.

Another object is to provide a voltage control device employing saturable reactors for controlling the voltage of `a power supply system in a stepless manner and wherein phase shift and harmonic effects are held to a minimum.

Still another obgect is to provide a voltage control system employing a minimum number of saturable reactors in controlling the voltage of the system within `a relatively large control range while the electrical design ratings, and therefore cost, of the reactors is relatively low.

in accordance with one form of the present invention, a voltage control device is provided which includes a tirst circuit having a variable impedance device, and a second circuit connected in parallel relation with the first circuit and which includes another variable impedance device in series with a shiftable phase or reversible polarity source of voltage. By selectively varying the impedances, and changing the phase or polarity of the voltage source, the voltage across the first named impedance can be varie-d over a substantial range.

These and other objects `and advantages of the present invention will become apparent from the following detailed description tal-:en in conjunction with the accompanying drawings.

in the drawings:

FlG. l is a schematic circuit diagram illustrating one embodiment of the present invention,

FlG. 2 is a graphical representation of the impedances of the controlled reactors of FG. 1 plotted as a function of supply voltage, and

Patented Aug. 3, i965 lCe FlG. 3 is a schematic circuit diagram illustrating another embodiment of the present invention.

The circuit of FlG l includes a pair of power input circuit terminals lil yand l?. connected across an alternating current supply source i4 for supplying power to a load le through a transformer 1S having a primary winding 2@ and a secondary winding 22 on a magnetic core 2.3. Connected in series circuit relation between the power input and output circuits is a voltage contr l device, indicated generally at Zd, for controlling the power output or load voltage within predetermined limits.

ln the illustrated embodiment shown in FIG. l, the voltage control device is connected between a pair of terminals 26 and Z3, and in series with primary winding 2li and the voltage supply source lli. rhe control device includes a variable impedance device shown as a saturable core reactor Sil having a reactance winding 32 and a control winding 34 on la magnetic core 35. The rcactance winding 32 is connected between the terminals 2d and 2S in series with the supply source 11:- and primary winding Ztl. Connected in parallel circuit relation with the reactor 3d between the terminals 25 and 23 is a series circuit including a variable impedance, shown as a saturable core reactor 36, and an auxiliary source of voltage with means for reversing the polarity or vectorially shitting the phase oi the voltage therefrom. The auxiliary source is shown in FlG. l as an auxiliary winding 3% on the core 23 connected with a reversing switch 39, Reactor 36 includes a reactance winding iti and control winding i2 on a magnetic core 443. The auxiliary winding 3S is connected through the reversing switch 3% and the series connected reactance winding d@ in a circuit across the reactance winding 32 of reactor 33. A pair of terminals de' and 4d, which are respectively connected to the opposite ends of winding 3S, are referred to herein as the input terminals of the control device, while terminals 26 and 2S are referred to as the output terminals of the control device.

The reversing switch 39 is shown for illustration as a two-position switch including a pair of movable contact arms 4S and which are movable in concert, as indicated by the dashed line connection 5l, and three stationary contacts S2, 5d, and 5d. ln the switch operating position shown in HG. l, the contact arms 43 and Sd are in engagement with contacts 52 and 5d, respectively. When the switch is actuated to its other operating position, the contact arms f3 and 5@ are in engagement with

contacts

54 and 56, respectively. The stationary contacts 52 and 5o are connected together and they are connected by a lead d2 to one side of the auxiliary winding 38. The center contact Sd is connected to the other side of winding 3S by a lead 45s, the reactance winding fait), and a lead 6o. With the switch 3% connected in this manner, the phase or polarity connections of auxiliary winding 38 can be reversed with respect to the terminals zo and 23.

The impedances ot the reactors and 3d are varied by passing control current through the reactor control windings 3d and 42 which varies the saturation of the reactor cores 35 and lf-l. Wl ile various control circuits may be employed to supply control current to each of the control windings and 42, simple, mechanically controllable, direct current sources, indicated generally at oil and 7?, are shown in the drawings for illustration. The control source 68 includes a battery 72 connected across a potentiometer which has a movable arm 76 connected to one side of the control winding 34, and one end of the potentiometer is connected through and adjustable resistance 77 to the other side of the control winding 3111. Similarly, the control source '70 includes a battery 7S connected across a potentiometer $0 having a movable arm 82 connected to one side of control winding 42, and one end of the potentiometer is connected to the other side of the winding 42 through an adjustable resistor S3. The movable potentiometer arms 76 and S2 are shown coupled together for concert movement, as indicated by a dashed line connection Si.. As will be apparent from the circuit of FIG. l, movement of the

potentiometer arms

76 and 32 to the left will decrease the direct current in control winding 34 and increase the direct current flowing in control winding 42. Movement of the potentiometer arms in the opposite direction or to the right will, of course, increase the current in winding 3d and decrease the current in winding 52. In this way, the control currents flowing in the reactor control windings can be varied inversely with respect to each other to thereby vary the reactances or

reactance windings

32 and 40 inversely with respect to each other.

In the following discussion of the operation of the circuit of FG. l, it will be assumed that the control device 24 is operated in a manner to maintain the power output or load voltage substantially constant even though the voltage of supply source 14 varies above and below its normal or predetermined value. In describing the operation of the system, the auxiliary winding 38 is-considered as functioning as another secondary winding to supply an input voltage Ei across the input terminals 45 and d6 of the control device 24 to thereby provide a variable phase adjustin y voltage e across the control device output terminals 26 and 2S. By controlling the reactance values and selectively operating the reversing switch 39, the voltage e can be varied so that it effectively aids or opposes the supply voltage Es, or is substantially ineffectual, to maintain the power output or load voltage E at or return it to its predetermined normal value. For purpose of illustration, the winding 38 will be assumed to have a number of turns equal to of the number of turns of primary winding 2 so that the voltage e between terminals 26 and Z3 is effectively variable Within the range of from minus 10% to plus 10% of the normal value of supply voltage Es, as will be more fully explained hereinafter. In FIG. 2, curves X1 and X2, respectively, represent the impedance values of the

reactance windings

32 and 40 of

saturable reactors

30 and 36 over the voltage range of lcontrol device 24. As indicated by curves X1 and X2, the 1mpedance of

reactance windings

32 and 40 are varied inversely with respect to each other. When the supply voltage is at 100% of its normal value, the impedance of winding 32 is at a low or minimum value and the impedance of winding 430 is at a high or maximum value. As the supply voltage decreases or increases from its normal value, the impedance of winding 32, curve X1, increases while the impedance of winding 40, curve X2, decreases. When the supply voltage is at 90% or 110% of its normal value, the impedance of winding 32 is at a high or maximum value and the impedance of winding t0 is at a low or minimum value. The effects of varying the impedances or

reactors

30 and 36 will be more apparent from the following example of operation.

In considering the operation of the circuit of FIG. 1, the supply oi voltage ES and the load voltage EO will be considered to be at their respective normal values when the switch 39 is in the position shown in FIG. 1 and the potentiometers 74 and 80 are adjusted to provide a high or maximum DC. current in control winding 34 and a low or minimum DC. current in control winding 42. Under these conditions, reactor 301B will be substantially saturated and the impedance of reactance winding 32 at a minimum value while the reactor 35 will be unsaturated and Cil the impedance of winding 40 at a maximum value. Substantially all the control device input voltage E1 will appear across the reactance winding 40, and since the reactance of winding 32 is at a minimum value the adjusting voltage e will be substantially zero. The load voltage will be at its predtermined value as determined by the supply voltage value and turns ratio between the primary 20 and secondary 22. lf the impedance of winding 32 could be reduced to zero when the supply and load voltages are at their normal values, there would be, in effect, a short circuit across the terminals 26 an 28 and the adjusting voltage e would be zero.

If the supply Voltage Es increases from its normal value to a value above normal, the potentiometer arms 76 and S2 are moved to the left, as viewed in FIG. l, to thereby decrease the DC. current flowing in control Winding 34 and increase the D C. current in control winding d2. Varying the control current in this manner increases the impedance of reactance winding 32 and decreases the impedance of reactance winding 40. An adjusting voltage e will now appear across reactance winding 32 and

terminals

26 and 28, and will be in phase opposition with the supply voltage Es so that the load voltage E0 is maintained at or brought back to its normal value. For example, if the supply voltage ES increased to 110% of its normal value, the impedance of winding 32 would be increased to a high or maximum value and the impedance of winding 40 decreaesd to a low or minimum value so that the auxiliary winding 3S would supply substantially the full voltage E, (10% of the normal supply voltage) across

terminals

26 and 28 in phase opposition or bucking relation with the supply voltage Es. If the supply voltage now returns to its normal value, the

potentiometer arms

76 and 82 are moved to the right to their original positions so that the adjusting voltage e is again at its minimum or substantially zero value.

On the other hand, if the supply voltage decreases from its normal value, the switch 39 is irst operated to reverse the polarity connections of auxiliary winding 3S to thereby vectorially shift the phase of the adjusting voltage e with respect to the supply voltage Es. By operating the switch from the position shown to its other position, input terminal 45 is connected through reactance winding 4t), contact 54, and switch arm 4S to terminal 26, while input terminal 46 is connected through Contact 56 and switch arm S0 to terminal 28. The switch is operated from one position to the other when the reactance winding 32 is at a relatively low or minimum impedance value, the voltage e being substantially at zero value and the supply and load voltages being substantially at their normal values. In this way, substantially all of the supply current is owing through reactance winding 32 and substantially none through the switch when the switch is operated.

After the switch 39 is operated as indicated above, the potentiometer arms are moved to the lett to increase the impedance of reactance winding 32 and decrease the reactance of winding 4t). This again produces an adjusting voltage e across terminals 26 and 2S but, under these conditions, the voltage e is in aiding relation with the supply voltage Es to thereby maintain the load voltage E0 at or raise it to its normal value. It the supply voltage, for example, should decrease to of its normal value, the impedance of reactance winding 32 is adjusted to a high or maximum value while the impedance of reactance winding 40 is decreased to a minimum value to thereby provide an adjusting voltage e which is substantially 10% of the normal value of supply voltage and which is in the aiding or boosting direction.

While the circuit of FIG. 1 has been explained from a standpoint of having the voltage e appearing across circuit terminals 25 and 28 superposed on or injected into the supply voltage circuit in series aiding or opposing relationship, it can `be described, of course, from the standpoint of varying the effective ampere turns ascenso on the primary side of transformer 13. From the latter point ot view, current from supply source l-/s is considered to iiow through the auxiliary winding in a direction relative to the direction of current in the primary Ztl to provide variable aiding ampere-turns or opposing ampere-turns dependinU upon the position of switch 39.

,l2-y utilizing the reversing Switch 3% to reverse the polarity or vcctorially shift the phase of the voltage impressed across the reactor Eil, the same auxiliary windd can be used to provide both bucking and boosting voltage etlects, and only two reactors are necessary for providing this control. Also, each of the reactors may be designed only for the voltage of winding 33. For example, when either of the reactors il@ and is saturated, the voltage across the other reactor is substantially egual to that of winding 33 or the voltage Ei. Since the reactors may be designed only for the voltage Ot auxiliary winding 33, the voltage rating and size, as well as cost ot each reactor, is relatively low.

ln addition, the total reactance in the power circuit of the system, i.e., the total series reactance presented by he

reactors

30 and 36 is relatively low. For example, en the supply voltage is at its normal value, in the stratcd example of operation, reactor Sil is at a very low value, and when the supply voltage is at 90% and 110% of its normal value the other reactor 3d presents a low reactance to load current flow. Because of the relatively low average reactance to load current7 the passo shift between supply and load voltages is relatively low. For the same reason, harmonic voltages, often generated by core saturation, are relatively low in the circuit hereinbefore described.

While the control device input voltage E! in the illustrated embodiment is obtained from the auxiliary winding disposed on the same core with the primary and secondary windings of transformer i3, other sources ot voltage may be used. For example, instead of auxiliary winding 3S, a separate transformer may be employed having a primary winding connected across the load or supply source ld and a secondary winding connected across input terminals 45 and fit-6.

ln the rnodied construction shown in FlG. 3, a separate transformer lut) is utilized to provide the input voltage Ei to a control device. Transformer lli@ has a primary winding lo?, connected across a load lliiand a secondary winding ldd connected to a pair of input terminals indicated at 103 and llt) of a voltage control vice M2. The control device ll? is connected in series n cuit relation between a power supply source lili and the load ldd.

The control device ll?. is sornes similar to the control device 2d in llG. l. As seen in FlG. 3, a saturand load ldd.

series with the secondary winding ldd, is connected between the terminals l2@ and i293 across th reactance winding i418. A reversing switch lZS is connected between the winding No and the reactors for ectorially shifting (180) the voltage from winding or input voltage Ei with respect to the supply source voltage ES. When the reversing switch l is operated, it reverses the polarity connections of winding ldd and shifts the phase of the variable adjusting voltage e developed across terminals 12d and M2.

Reactors lid and lZ/l are provided with control windings E36 and 32, respectively, which are connected to be supplied with DE. control current for varying the impedance of their associated reactance windings. As seen in FIG. 3, control windings i3@ and 132 are connected to DC. control sources 13d and 136, respectively. Each ot the control sources are shown as including potentionieters and batteries with the arms of the potentiomw eters interconnected for concert movement, as in the circuit of l.

The operation of the circuit ot FlG. 3 is similar to that described in connection with the circuit of FIG. l. By varying the currents in control windings 13@ and 132 inversely with respect to each other, the impedances of reactance windings ll and E25 vary inversely with respect to each other to thereby vary the adjusting voltage e across terminals l2@ and i221. The adjusting voltage e is combined with the supply voltage Es to control or regulate the load voltage E0. As previously mentioned herein with regard to the circuit of FIG. l, the variable adiusting voltage e can be controlled to provide a voltage boosting or a voltage bucking effect depending upon the position of trie reversing switch. The impedances ot reactance windings llo and d may be varied in the manner shown in FIG. 2. in such case, the curve X1 would represent the impedance values of winding il@ and curve X2 the impedance values of winding 126 over the voltage control range of the control device. The switch llt? is operated from one position to its other position when the reactance of winding MS is low or at a minimum value and is carrying substantially the full load current.

While the voltage control device in each of the illustrated einoodiin "s is conductively coupled into the power circuit by dn ect connection, a coupling transformer (not shown) may be used. ln such case, the primary of the coupling transformer may be connected across the reactor Si? in FIG. l, or the reactor M6 in FlG. 3, and the secondary connected in series in the power circuit.

it is to be understood that the foregoing description and the accompanying drawings have been given only by way of illustration and example, and that changes and alterations in the present disclosure, which will be readily a, arent to one si led in tlc art, are contemplated as within the scope of the present invention which is limited only by the claims which follow.

What is claimed is:

l. A voltage control device comprising a tirst circuit including a iirst variable impedance device, a second circuit coupled across said rst circuit and including a second variable impedance device, means for connecting a source of voltage in said second circuit to provide a voltage across said lirst circuit, means for selectively reversing the phase of said voltage, and means for varying the impedance values of said impedance devices to vary the magnitude of said voltage.

Z. A voltage control device comprising a first variable impedance device, a series circuit including a voltage source and a second variable impedance device coupled in parallel circuit relation with said first impedance device, means for inversely varying the impedance values of said impedance devices to provide a variable voltage across rst variable impedance device, and means operable to reverse the phase of said variable voltage.

3. in combination, a power output circuit, a power input circuit connected to a lirst source of supplyl voltage to supply power to the power output circuit, and a voltage control device for varying the voltage supplied to said power output circuit comprising a first variable impedance device coupled in series circuit relation with one of said power circuits, a series circuit including a second variable impedance device and a second source of voltage coupled in parallel circuit relation with said first impedance device, means for varying the impedance values of said impedance devices to provide a variable voltage across said iirst impedance device, and switch means in said series circuit for selectively connecting said second source ot voltage in either aiding or opposing relation with respect to the voltage of said first source `of voltage.

d. A voltage control device comprising a irst circuit including a first variable impedance device, a second Sill u circuit connected across said first circuit and including a second variable impedance device, means for connecting a source of voltage in said second circuit, means for varying the impedance values of said devices to provide a variable voltage across said first impedance device, and a mechanical reversing switch connected said second circuit for selectivity reversing the phase of said variable voltage.

5. A voltage control device comprising a first variable reactance device device, a series circuit including a transformer winding and a second variable reactance device coupled in parallel circuit relation with said iirst reactance device, means for energizing said winding to provide voltage of predetermined phase in series circuit, means for varying the reactance values of said reactance devices, and means for shitting the phase or said voltage lSO".

6. A voltage control device comprising a pair ot saturable reactors each having a reactance winding and a control winding, a series circuit includingT a source of voltage of predetermined phase and the reactance winding of one of said reactors, said series circt t being coupled in parallel circuit relation with the reactance winding of the other of said reactors, means for supplying variable control current to each of the control windinUs of said reactors to provide a variable voltage across the reactance winding of said other reactor, and additional means operable to shift the phase of said variable voltage.

7. An electrical system comprising a power input circuit connectable to a source of supply voltage for supplying power to a power output circuit, a iirst circuit including a iirst saturable reactor coupled in series circuit relation with one of said power circuits, a second circuit including a second saturable reactor coupled in parallel circuit relation with said first circuit, means for connecting an auxiliary source of voltage of predetermined phase in said second circuit, means for Varying the reactance values of said reactors inversely with respect to each other, and additional means for shifting the phase of the voltage from said auxiliary source with respect to said supply voltage.

8. An electrical control device comprising a iirst circuit including a iirst saturable reactor, a second circuit including a second saturable reactor and a transformer winding connected in series, said second circuit being coupled across said rst circuit, means for varying the reactances of said first and second reactors, and a mechanical reversing switch connected in said second circuit for selectively reversing the phase connections of said winding.

9. An electrical system comprising a power input circuit connectable to an alternating current source of supply voltage for supplying power to a power output circuit, a first saturable reactor coupled in series circuit relation between said power circuits, a series circuit including a transformer winding and a second saturable reactor coupled in parallel circuit relation with said iirst saturable reactor, means for energizing said winding to provide a voltage across said iirst saturable reactor, a mechanical reversing switch in said series circuit operable to reverse the phase conne tions of said winding in said series circuit, and means for varying the reactance values of said reactors.

it). An alternating current supply system comprising power input and output circuits, a transformer having a main winding coupled across one of said power circuits, and an auxiliary winding coupled to said main winding, and a control circuit comprising a irst circuit including a iirst reactor coupled in series with said main winding, a second circuit including a second reactor connected in series with said auxliary winding, and a reversing switch for selectively reversing the phase of the voltage from said auxiliary winding, said second circuit being coupled in parallel relation with said rirst circuit, and

Si means associated with said reactors for varying the reactance thereof.

it. An alternating current control system comprising a transformer having a main primary winding connected to an alternating current supply source, a main secondary winding connected to a load circuit, and an auxiliary winding, and a voltage control device comprising a iirst circuit including a irst saturable reactor coupled in series circuit relation with one of said main windings, a second circuit including a second saturable reactor and said auxiliary winding connected in series therewith, said second circuit being connected in parallel circuit relation with said first circuit, a reversing switch connected with said auxiliary winding for selectively reversing the phase relationship of said auxiliary winding with respect to said primary winding, and means for inversely varying the reactances of said reactors.

l2. An A.C. power supply system comprising power input and output circuits, means for connecting said power input circuit to an A.C. voltage supply source for supplying power to said power output circuit, and a voltage control circuit for controlling the voltage supplied to said power output circuit comprising a iirst saturable core reactor having a reactance winding and a control winding, a rst circuit having end terminals and including the reactance winding of said iirst reactor connected between said end terminals, means connecting said iirst circuit in series circuit relation with said power input and output circuits, a second circuit including a second saturable core reactor having a reactance winding and a control winding, an auxiliary A.C. voltage supply source, and means including a phase reversing switch having tirst and second switch positions connecting the reactance winding of said second reactor in series circuit relation with said auxiliary source across said iirst circuit between said end terminals, said switch when in said iirst switch position connecting one of said end terminals through the reactance winding of said second reactor to one side of said auxiliary source and the other of said end terminals to the other side of said auxiliary source, said switch when in said second switch position connecting said one end terminal to said other side of said auxiliary source and said other end terminal through the reactance winding of said second reactor to said one side of said auxiliary source, means for supplying control current to each of said control windings, and means for inversely varying the magnitudes of the control currents iiowing in said control windings for inversely varying the reactance values of said reactance windings to provide a variable A.C, voltage across said iirst circuit.

13. An A.C. power supply system comprising a power input and output circuits, means for connecting said power input circuit to an A.C. voltage supply source for supplying power to said power output circuit, and a voltage control circuit for controlling the voltage supplied to said power output circuit comprising a first saturable core reactor having a reactance winding and a control winding, a iirst circuit having first and second circuit terminals and including the reactance winding of said first reactor connected between said circuit terminals, means connecting said iirst circuit in series circuit relation with said power input and output circuits, a second circuit including a second saturable core reactor having a reactance winding and a control winding, a transformer having a transformer winding with end terminals, means for energizing said transformer winding to provide a voltage thereacross, and means including a phase reversing switch having iirst and second switch positions connecting the reactance winding of said second reactor in series circuit relation with said transformer winding across said iirst circuit between said circuit terminals, said switch when in said iirst switch position connecting said iirst and second circuit terminals to said first and second end terminals, respectively, with the reactance winding of said second reactor connected between one of said circuit terminals and one of said end terminals, said switch when in said second switch position connecting said rst and second circuit terminals to said second and rst end terminals, respectively, with the reactance winding of said second reactor connected between one ot said circuit terminals and one of said end terminals, means for supplying control current to each of said control windings, and means for inversely varying the magnitudes of the control currents owing in said control windings for inversely varying the reactance values of said reactance windings to provide a variable voltage across said tirst circuit to control the voltage supplied to said power output circuit.

No references cited.

LLOYD MCCOLLUM, Primary Examiner.

ROBERT C. SIMS, Examiner.

Claims

1. A VOLTAGE CONTROL DEVICE COMPRISING A FIRST CIRCUIT INCLUDING A FIRST VARIABLE IMPEDANCE DEVICE, A SECOND CIRCUIT COUPLED ACROSS SAID FIRST CIRCUIT AND INCLUDING A SECOND VARIABLE IMPEDANCE DEVICE, MEANS FOR CONNECTING A SOURCE OF VOLTAGE IN SAID SECOND CIRCUIT TO PROVIDE A VOLTAGE ACROSS SAID FIRST CIRCUIT, MEANS FOR SELECTIVELY REVERSING THE PHASE OF SAID VOLTAGE, AND MEANS FOR VARYING THE IMPEDANCE VALUES OF SAID IMPEDANCE DEVICES TO VARY THE MAGNITUDE OF SAID VOLTAGE.