US1596505A - Electric regulator - Google Patents

Description

Aug. 17 1926. 1,596,505 -w. E. MOORE ELECTRI C REGULATOR Filed Sept. i, 1922 Patented Aug. 17, 1926.

UNITED STATES PATENT OFFICE.

WILLIAM E. MOORE, OE PITTSBURGH, PENNSYLVANIA, ASSIGNOR TO PITTSBURGH RESEARCH CORPORATION, A CORPORATION OF DELAWARE.

ELECTRIC REGULATOR.

Application filed September 1, 1922. Serial No. 585,652.

This invention relates to automatic electric regulators, and more particularly to such regulators as are employed to maintain the voltage, current or load substantially constant on' any given circuit.

Specifically, the present invention relates to regulators foralte-rnating current cirwits, and while it is illustrated and described in connection with an electric arc furnace, it is equally applicable to other uses.

Automatic electric regulators as heretofore constructed have always included relays or contact making devices of one kind or another, for opening and closing control circuits, cutting in and out resistances, etc. As is well known, such contact making devices are always a source of trouble, and it is the primar object of the present invention to provi e a regulator from which all contact making devices are eliminated. In other Words, I propose to produce th necessary movements of the shiftable element for effecting regulation, by means of control circuits which are permanently closed and in which the ohmic resistance is maintained substantially constant.

This I accomplish by means of a reversible electric motor. the flow of current to which is controlled indirectly by variations of the electrical conditions in the circuit to be regulated.

In order that the invention may be readily understood, reference is had to the accompanying drawin forming a part of this specification, and Which illustrates diagrammatically the apparatus and electrical connections embodying the invention, the same being shown, by way of illustration, as applied to an electric arc furnace.

eferring to the drawing in detail, I have illustrated a power transformer T for supplying current to the furnace and to the regulator, such transformer being of the usual or any desired construction, and comprising a primary winding 1 and a secondary winding 2. For simplicity of illustration, only a single phase transformer and furnace is shown, although it will be understood that the invention is equally-applicable to polyphase furnaces of the kind usually emplo ed in practice.

One side 0 the secondary winding 2 is connected by a conductor 3 to the bottom or shell of a furnace 4. The electrode 5 of the furnace is vertically movable as usual, and is electrically connected by means of conductors 6 and 8 with the other side of the secondary 2, a primary coil 7 of the re ulator hereinafter described being included in this circuit.

The regulator comprises a transformer consisting of a relatively fixed frame or member 9 havin two legs 10 and 11,and a relatively movab e member or leg 12 mounted between the ends of legs 10 and 11, and normally spaced therefrom to provide air gaps a and b. The movable member 12 is shown as pivotally mounted at 13, and as spaced from the fixed member as to provlde an air gap 0.

The primary coil 7 of the transformer is wound upon this movabl member 12 and is connected in series with the load or circult to be regulated. It Will be evident that the magnetic flux generated in the member 12 by the coil 7 can pass through to separate paths, one path being across theair gap a and leg 10, and the other being across air gap 6 and through the leg 11. In other words, the flux divides through these two paths, the member 12 being common to both paths.

By reference to the drawing, it will be seen that the leg'l0 is made much' smaller in cross section than the leg 11, and that the movable member 12 is of a cross section substantially equal to the sum of the cross sections of legs 10 and 11. Thus, as the current through coil 7 builds up, the flux through the member 12 will first divide equall between the two legs 10 and 11, but as t e current continues to increase, and the flux becomes greater, the leg 10 soon becomes saturated, and thereafter the leg 11 carries a greater portion of the flux.

The movable member 12 is yieldingly maintained in its central or intermediate position, as shown in the drawings, by means of sets of buttress springs 14 and 15, arranged one on each side thereof. As shown, each set contains three springs of progressively varying length, so that as the member 12 moves, it successively engages one after the other. Thus, as the member 12 approaches the end of either'leg 10 or 11, the springs offer a resistance which increases at a rate greater than that at which said member approaches the fixed leg, so that for each increase in the flux,

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the movable member 12 will move closer to the leg end and will remain stationary in such position, the magnetic attraction being balanced by the resistanceofi'ered by the sprin s. In other words since the magnetic pull between two mem rs varies inversely as the square of the distance, it is obvious that a simple spring would not prevent the movable member 12 from moving into contact with the end of the leg as soon as there was an unbalancing of the flux be tween the two legs, audit is nec'essa to provide a compound spring structure 0 the kind illustrated, in order to allow the movable member 12 to approach the leg end gradually, and by progressive stages, While I have shown a compound spring structure consisting of a series of springs, as illustrated, it is evident that a sin le s ecially constructed spring may be emp oye i'f desired, the requirement being that the resistance ofi'ered by such spring must increase at a greater rate than that at which the member 12 moves. I

A designates the armature or rotary element and F the field or stationar element of a small electric motor, the she of such motor being connected, inmthe present in; stance, to the usual windingadrum (not shown) and raising and lowerin "the electrode 5. This motor is prefera 1y of the commutation type, althou h other types of motor may be employed. e field F, which is in the nature of a shunt winding, is separately excited, being connected at one end directly to one side of the power transformer T by means of conductors 16 and 22, the other side of the field winding being' connected through a resistance R, to a conductor 21, connected with the furnace lead 3, extending from the other side of the transformer winding 2. Thus, the field F is continuously excited from the power transformer T, which may be regarded as a substantially constant source of alternating current. The purpose of the resistance R is to prevent too great a lag in the field current, which would occur if the entire impedance of the field circuit comprised only the reactance of the field coil. In other words, it is desirable to have the current in the circuit to be regulated, namely in coil 7 of the regulator transformer, substantiall in phase with that in the field coil F.

l ound upon the two legs 10 and 11 of the transformer member 9 are secondary coils 17 and 19, these coils each containing approximately thesame number of turns and being wound in opposition. Similar ends of the coils are connected by means of a conductor 18. The other end of coil 17 is connected through a resistance R and conductor 16 to one side of the power transformer winding 2 and the other end of the coil 19 is connected by a conductor 20 to one side of the armature A, the other side of said armature being connected with the conductor 21. Thus, it will be seen that the two coils 17 and 19 are in series with each other and with the armature A of the motor, all of these armatures being in a circuit connected across the winding 2 of the power transformer and in series with the resistance R The windings 17 and 19 are so arranged that the flux passing in the same direction through the two legs 10 and 11, will generate voltages in said coils in such a direction as to oppose each other when they are connected in series, as shown. Thus, if the flux through the two legs 1.0 and 11 is equal, theresul'tant voltage generated by the two coils 17 and 19 will ,be zero.

It will be observed that the power transformer T tends to constantly force a 'current through the'circuit 16 R, 17, 18, 19, 20 and the armature A of the motor, and that so long as the two voltages generated in the coils 17 and 19 balance each other, current will flow in the circuit just traced and, since this current is substantially in phase with that in the field F, owing to the resistance R, the motor armature A will be caused to revolve. The same result will, of course, be obtained if the circuit 6 is open and there is no voltage being generated in the coils 17 and 19.

We will assume that this latter is the case, and that the direction of rotation of the motor under these circumstances is such as to lower the electrode 5 into the furnace. 7

As soon as the electrode contacts with the charge, there is a certain rush of current through the circuit 6 and the coil 7, thus generating a heavy flux in the member 12. This flux divides through the two legs 10 and 11, but the leg 1.0 becomes immediately saturated, while the flux continues to build up in the leg 11. This generates a strong voltage in the coil 19 which not only overcomes that generated in 17, but also, since it is substantially 180 out of phase with that generated by the power transformer winding 2, it overcomes the voltage of the power transformer also, and causes a current to flow through the circuit 16 R, 17, 18, 19, 20 and the motor armature, in a direction the reverse of that which was formerly flowing in this circuit. By reverse, it is of course meant that this current is 180 out of phase with the first current, and therefore has the effect of reversing the direction of rotation of the motor armature A. This armature then revolves in such a direction as to lift the electrode 5 away from the charge and draw out the are. This sudden reversal of the motor is also assisted in the case mentioned, by reason of the fact that the contact of the electrode 5 with the charge momentarily short circuits the power transformer T and lowers its voltage, so that the voltage generatedin. coil 19 can more readily overcome it.

As the electrode is raised and the arc is drawn out, the current through the circuit 6 and coil 7 gradually decreases, and the tint through the member 12 becomes less and less until it reaches a point where the resultant voltages generated by the coils 17 and 19 just balance the voltage impressed upon the armature circuit by the power transformer T. When this occurs, the current flowing in this circuit will drop to zero and the armature will remain stationary. Should now the power input to the furnace fall below a predetermined point, the volta impressed on the armature circuit by t e power transformer will again overcome or overbalance that generated by the coils 17 and 19, and will again cause the motor to revolve in sucha direction as to lower the electrode, and this lowering will continue until the increasing flux through the member 12 again causes the resultant voltages generated in the coils 17 and 19 to just balance the voltage impressed by the power transformer.

Thus, it will be seen that the motor will run in one direction or the other, or remain stationary, according to the armature conditions in the circuit to be re lated, and that this effect is produced wit out any contact making or breaking device whatsoever.

The overbalancing effect of coil 19 is increased by virtue of the movement of the member 12 toward the leg 11, as the flux increases beyond a predetermined value, since such movement serves, of course, to decrease the air gap 12 and to increase the air gap a, thus producing a-greater differential between the fluxes passing through the two paths. In other words, means are thus provided for producing in the coil'19 a variation of voltage greater than the corresponding fluctuations of current in the coil 7, and in this way the fluctuations of current are magnified and the sensitiveness of the apparatus increased.

It will, of course, be understood that suitable means for adjusting the width of the air gaps a, b and 0 may be provided, and also means for adj ustin the resistance of the springs 14 and 15, so t at it will be possible to set the apparatus to maintain the motor armature stationary at any desired current value in the circuit 6.

In some cases, satisfactory operation can be obtained, with the use of the coils 7 and 19 only, the coil 17 and leg 10 being dispensed with. In such cases, the voltage of coil 19 will be balanced against the voltage impressed on the armature circuit by'the power transformer.

It will be apparent that the extent of the unbalancing of the voltage in the armature circuit is dependent upon the extentof variation of the oad above or below normal, and that the speed and tor ue of the motor are proportional to such un alancing. In other words, the force tending to restore the load to normal is eater or less, according as the variation rom normal is large or small. While I have illustrated my invention as applied to an electric furnace, it will be obvious that it is applicable to many other uses. Thus by su stituting a voltage coil for the primary coil 7, the apparatus may be em loyed to regulate voltage on any given eeder, or by connecting the motor to a water gate, the 'device'may be used to regulate the speed and voltage of hydro electric generators. Other uses of the in vention will readily suggest themselves to those skilled in the art.

\Vhile I have shown the armature of the motor as the reversible element, it is, of course, obvious that the direction of current through the armature might be main tained constant and the excitation of the field reversed by means of the regulator.

What I claim is: 1. An automatic electric regulator comprising a motor having a field winding and a rotary armature, a source of current, separate, permanently closed circuits for supply-- ing current to said field and armature from said source, and means for automatically controlling the flow of current in one of said circuits in accordance with the electrical conditions in the circuit to be regulated, so that said motor armature will be caused to run in one direction or the other, as required.

2. An; automatic electric regulator comprising an alternating current motor having a field winding and a rotary armature winding, means for maintaining a substantially constant current through one of said windings, a circuit including the other winding, and inductive means responsive to changes in the current to be regulated for automatically varying the current through said circuit while maintaining its ohmic resistance substantially constant 3. In an automatic electric regulator, the combination with a rotary motor comprising two current receiving elements, a closed circuit in which one of said elements is included, means for impressing a substantially constant alternating voltage on the terminals of said circuit, and means responsive to variations in the current to be regulated for inducing in said circuit a second alternating voltage approximately 180 electrical degrees out of phase with the first.

4. In an automatic electric regulator, the combination with a rotary motor comprising two current receiving elements, a closed circuit in which one of said elements is included, means for impressing a substantially constant alternating voltage on the terminals of said circuit, and a transformer having a primary energized by the current to be regulated, and having a secondary connected in said circuit.

5. In an automatic electric regulator, the combination with a rotary motor comprising two current receiving elements, a closed circuit in which one of said elements is included, means for impressing a substantially constant alternating voltage on the terminals of said circuit, and a transformer having a primary energized by the current to be regulated, and having two secondaries connected in series opposition, and included in said circuit. a

6. In an automatic electric regulator for alternating currents, the combination with a rotary motor having two windings, a source of alternating current, independent circuits for supplying said windings directly from said source, an element to be moved y said motor to effect regulation, and a transformer having primary and secondary windings, said primary winding being connected so as to be traversed by the current to be regulated, and said secondary windin being included in one of the circuits supplying the motor from said source.

7. In an automatic electric regulator for alternating currents, the combination with a rotary motor having two windings, a source of alternating current, independent circuits for supplying said windings directly from said source, an element to be moved by said motor to effect regulation, and a transformer having a primary and two secondary windings, said primary winding being connected so as to be traversed by the current to be regulated, and said secondary windings being both included in one of the circuits supplying the motor from said source, and connected in series with each other, but in opposition.

S. In an automatic electric regulator for alternating currents, the combination with a rotary motor having two windings, a source of alternating current, independent circuits for supplying said windings from said source, an element to be moved by said motor to effectregulation, and a transformer having primary and secondary windings, said primary winding being connected with said source and in series with the circuit to be regulated, and said secondary winding being connected in series between said source and one of the motor windings.

9. In an automatic electric regulator for alternating currents, the combination with a motor having field and armature windings, a source of alternating current, independent circuits for supplying said windings .from said source, an element to be moved by said motor to eifect regulation, and a transformer having primary and secondary windings, said primary winding being connected so as to be traversed by the current to be regulated, and said secondary windin being included in one of the circuits supp ying the motor, and means whereby the variations of voltage generated in said secondary windin are relatively greater than the cor-. responding fluctuations of current in the primary winding which produce them.

10. In an automatic electric regulator for alternating currents, the combination with a rotary motor having two windings, a source of alternating current, independent circuits for supplying said windings from said source, an element to be moved by said motor to effect regulation, and a transformer having a primary and two secondary windings, a core having branches providin two separate magnetic paths, the primary Icing wound on a portion of the core common to both paths, and the branch on which one secondary is Wound being smaller than the other, said primary winding being connected in circuit with the current to be regulated, and said secondary windings being connected in opposition and in series between the said source and one of'said motor windings.

11. In an automatic electric regulator for alternating currents, the combination with a rotary motor having two current receiving elements, a source of alternating current, independent circuits for supplying said elements from said source, a device to be moved by said motor to effect regulation, and a transformer having primary and secondary windings, said primary windings being connected so as to be traversed by the current to be regulated, and said secondary winding being included in one of the circuits supplying the motor, and means whereby the variations of voltage generated in said secondary winding are relatively greater than the corresponding fluctuations of current in the primary winding which produce them.

12. In an automatic electric regulator for alternating currents, the combination with a rotary motor having two current receiving elements, a source of alternating current, independent circuits for su plying said elements from said source, a. evice to be moved by said motor to effect regulation, and a transformer comprising a core having an air gap and also having primary and secondary windings, said primary winding being connected so as to be traversed by the current to be regulated, and said secondary winding being included in one of the circuits supplying the motor, and means whereby a variation in the current in said primary serves to vary said air gap.

13. In an automatic electric regulator for alternating currents, the combination with a rotary motor having two current receiving elements, a source of alternating current, independent circuits for supplying said elements from said source, a device to be moved by said motor to effect regulation and a transformer comprising a core having an air gap and also having primary and secondary windings. said primary winding being connected so as to be traversed by the current to be re ulated, and said secondary winding being included in one of the circuits supplying the motor, and means whereby an increase in current in said primary serves to decrease said air gap, and vice versa.

14. In an automatic electric regulator for alternating currents, the combination with a rotary motor having two current receiving elements, a source of alternating current, independent circuits for supplying said elements from said source, a device to be moved by said motor to effect regulation, and a transformer having a core consisting OI a relatively fixed member having two legs, and a relatively movable member mounted with its end positioned between the ends of said legs, and spaced therefrom, windlngs on said members, the windings on said fixed member being included in one of the circuits sup lying. the motor, and the windings on said movable member being connected so as to be traversed by the current to be regulated, and yielding means acting against each side of said movable member and tending to maintain it in its intermediate position, said means being normally balanced.

15. In an automatic electric regulator for alternating currents, the combination with a motor having field and armature windings,

a source of alternating current, independent circuits for supplying said windings from said source, an element to be moved by said motor to eflect regulation, and a transformer comprising a core having .an air gap and also having primary and secondary windings, said primary winding being connected so as to be traversed by the current to be regulated, and said secondary winding being included in one of the circuits supplying the motor, and means whereby an increase in current in said primary serves to decrease said air gap, and vice versa.

16. In an automatic electric regulator for alternating currents, the combination with a motor having field and armature windings, a source of alternating current, independent circuits for supplying said windings from said source, an element to be moved by said motor to effect regulation, and a transformer having a core consisting of a relatively fixed member having two legs, and a relatively movable member mounted with its end positioned between the ends of said legs, and spaced therefrom, windings on said members, the windings on said fixed member being included in one of the circuits supplying the motor, and the windings on said movable member being connected so as to be traversed by the current to be reguand a transformer, provided with a core having two relatively fixed legs of different cross-section, and a movable leg of a crosssection substantially ual to the sum of the other two, the movab e leg bein mounted with its end positioned between t e ends of the fixed legs, thus iormin two separate magnetic paths, each inclu mg one of the fixed legs, with the movable leg common to both, a primary winding on the movable leg connected'so as to be traversed by the current to be regulated and secondary windings on the two fixed le 5 included in one of the circuits supplying the said motor.

18. In an automatic electric regulator for alternating currents, the combination with arotary motor having two separate windings, a source of alternating current, independent circuits for supplying said windings directly from said source, an element to be moved by said motor to effect regulation, and a transformer, having a core provided with three legs, forming two separate magnetic circuits, one leg bein common to both, a primary winding on sai common leg connected so as to be traversed by the current to be regulated, and secondary windings on said other legs, said secondary windings being connected in series opposition and included in one of the circuits supplying the said motor from said source.

19. In an automatic electric regulator for alternating currents, the combination with a rotary motor having two separate windings, a source of alternating current, independent circuits for supplying said windings from said source, an element to be moved by said motor to effect regulation, and a transformer, having a core provided with three legs, forming two separate magnetic circuits, one leg being common to both, a primary winding on said common leg connected so as to be traversed by the current to be regulated, and secondary windings on said other legs, said secondary windings being connected in series opposition and included in one of the circuits between the motor and said source, the legs on which said secondary windings are wound being of unequal cross-section.

20. In an automatic regulator for electric arc furnaces, the combination with a rotary motor for raising and lowering the electrode, said motor having two current receiving elements, of means for constantly exciting one element of the motor, means connecting the other element of the motor in circuit with a constant voltage source of current, and means for inducing in said circuit an op osed voltage which increases as the power m ut to the furnace grows larger, whereb w en a given power input is reache said voltages are balance and whereby, upon a further increase in the power input, said induced voltage overcomes the constant volta e, and causes a current to flow through t e connected motor element in reverse direction, relative to the other element.

21. An automatic electric regulator comprising a rotary motor having two current receiving elements, a permanently closed C11- cuit including one of said elements, a transformer having a secondary winding connected in said circuit and havin a rimary winding connected with the circuit to be' regulated, said transformer comprising a core having two fixed legs on which the secondary winding is wound, and a movable 'leg on which the said primary winding is wound, said movable leg being pivotally mounted between the two fixed legs.

22. An automatic electric regulator including. in combination, a rotary motor, and a current reversing device, said device comprising a three legged magnetic core, one of said legs being pivotally mounted between the other two, a primary winding surrounding the pivoted leg, and secondary windings connected to give opposing electromotive forces surrounding the other legs one of which is normally saturated and the other unsaturated when the current flowing in the primary is less than a predetermined amount, said secondary windings being included in a series circuit with an element of said motor. 23. An automatic electric regulator including, in combination, a rotary motor, and a current reversing device, said device com; prising a magnetic core consisting of two pivotally connected sections, primary and secondary windings on said respective sections, said secondary windings being connected in a series circuit with an element of said motor, means for impressing a con stant alternating voltage on said circuit, and resilient means holding adjacent ends of said sections apart to form .an air gap, whereby when the magnetic flux increases, said air gap tends to close, and thus cause a still further increase of flux.

24. In an automatic electric regulator, the combination with a rotary electric motor comprising two current receiving elements, of two independent permanently closed circuits in which said two elements are respectively included, a common source of alternating current for impressing a substantially constant voltage on the terminals of both circuits, and means for inducing in one of said circuits, at a point thereof between said source and motor element, a variable alternating voltage in opposition to that impressed.

25. In an automatic electric regulator, the combination with a rotary electric motor comprising two current receiving elements, of two independent permanently closed circuits in which said two elements are respectively included, a common source of alternating current for impressing a substantiall constant voltage on the terminals of bot circuits, and means for inducing in one of said circuits, a variable alternating voltage in opposition to that impressed, whereby the speed of the motor may be reduced, and for increasing said induced opposed voltage to a point where it overcomes the impressed vo tage, whereby the direction of rotation of said motor may be reversed.

26. The method of controlling the rotation of the rotary element of a motor having independently excited field and armature elements, which comprises supplying alternating current at substantially constant volta e to one of said elements, impressing on tie terminals of the other element also an alternating electromotive force, and varying both the voltage and phase relation of such electromotive force, while maintaining the frequency constant.

27. The method of controlling the flow of current through a permanently closed circuit, which consists in impressing a substantially constant alternating voltage on the terminals of the circuit, inducing in said circuit an alternating voltage of opposite phase to that impressed, and increasing such induced voltage until it overcomes the impressed voltage and reverses the phase relation of the current flowing in the circuit.

In testimony whereof I afiix my signature.

WILLIAM E. MOORE,

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