US1915050A - Regulating system - Google Patents

Description

June 20, 1933. F. T. COLDWELL 0 REGULATI-NG SYSTEM Filed Ju1y 25, 1951 lnv en tow": Frank T. Coldwel I,

I! is AttoT-n ey.

Patented June20, 1933 UNITED STATES FRANK T. GOLDWELL, OF ALPLAUS, NEW

PATENT OFFICE YORK, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK nneuna'rmo SYSTEM Application filed July 25,

particular application to voltage regulating. systems in which a contact-making voltmeter,

controls a pilot motor operated voltage regulator preferably through intermediate re lays. Such voltage regulating systems are in wide use for regulating the voltage of the alternating current feeder circuits which supply most house lighting circuits.

The ideal regulating system would operate without any delay to restore to exactly normal the value of the regulated condition, which has departed from this value because of some change in operating conditions. The

actual voltage regulating system of the type to which my invention is particularly applicable falls short of this ideal performance in a number of ways. Thus it tends to overrun. and therefore to hunt, because of several factors. One is that the effect of the usual holding coils, which are associated with the contact-making voltmeter, is to prevent separation of the meters contacts until there is a sufficiently great overregulated voltage to overcome this holding efli'ect. Other reasons are the overrunning, or lost motion, characteristics of the system which permit the regulator to operate for a. short time after the contact'makin g voltmeter has returned to new tral.

In accordance with my invention I provide an improved regulating system which, when embodied in a feedervoltage regulating system, has means for positively restoring the contact-makin voltmeter to neutral before complete regu ation has occurred and for holding it there a predetermined time. I also provide means for causing an initially strong holding effect which tapers off so as 1931. Serial No. 553,136.

to permit a quick break of the contact-making voltmeter contacts, while preventing rebounding of the contacts.

An object of my invention is to provide a new and improved regulating system.

Another object of my invention is to provide means for improving the operation, and

for preventing hunting, of regulating sys tems having contact-making devices which control pilot motors.

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. 1 is a diagrammatic illustration of a feeder voltage regulating system embodying certain features of my invention, Fig. 2 is a modification of the invention illustrated in Fig. 1, Fig. 3 is a diagrammatic illustration of a feeder voltage regulator system embodying additional. fea tures of my invention, while Fig.v 4 is a modification of the arrangement illustrated in Fig. 3.

Referrin now to Fig. 1, 1 is a contactmaking vo tmeter having a control coil 2,.

which is connected to respond to the voltage 'of a circuit 3, and a pivotally mounted contact arm, or beam, 4. This arm is shown in its normal position and it is adapted to be moved by coil 2 into circuit controlling position wherein it makes contact with relatively fixed contacts 5 and 6, respectively. A pair of relays 7 are under the control of contacts 5 and 6, respectively, and these relays are connected to control the operatingeircuit for a pilot motor 8 which is mechanically connected to operate an induction feeder voltage regulator 9 in the usual manner. Regulator 9 is connected to circuit 3 in such a manner that it is capable of inserting variable amounts of regulating voltage, boost or buck, in this circuit.

This regulator is a well known device and its operation is well understood by those skilled in the art. It is essentially an autotransformer having a primary winding connected a'cross circuit 3 and a secondary winding connected in circuit 3 and means, under the control of the operating motor, for varying the inductive relation of these windings.

The usual holding coils 10 and 11 are associated with movable contact arm 4 of meter 1. These coils are connected in parallel with the operating coils of relays 7 and are so arranged as to hold the contacts of the meter closed, as soon as these contacts touch, so as to prevent a trembling engagement-of these contacts with a consequent injurious arcing. As a convenient source of current supply for motor 8, the operating coils of relays 7, and holding coils 10 and 11, I provide a small transformer 12 connected to the main circuit 3.

In order to give holding coils 10 and 11 an inverse pull-time characteristic, I connect a resistance element having a non-linear voltampere characteristic, such for example as a ballast resistor 13, in series with them. At this point it should be stated that the broad idea of giving the holding coils of a contactmaking voltmeter an inverse pull-time characteristic is disclosed and claimed in a copending application of Fred H. Winter, Serial No. 553,134 and, filed July 25, 1931, (Docket 38,341) and assigned to the assignee of the presentapplication. My invention in this respect is limited to achieving this result by the use of impedance or resistance elements having non-linear volt-ampere characteristics associated with the holding coil circuit. Thus, for example, instead of connecting a positivetemperature resistance coeflicient element, such as a ballast resistance of iron wire, in series with the holding coils so as to weaken the current therein as the time of their energization increases, I may also achieve substantially the same result by connecting a negative temperature coefiicient of resistance element in parallel with these coils so as to by-pass more and more of the current required by these coils as their time of energization increases.

The means for positively restoring to its neutral position the contact arm 4 of contactmaking voltmeter 1 is illustrated in Fig. 1 as comprising a restoring coil 14, which is arranged to be energized whenever contacts 5 or 6 are engaged and which when energized acts to urge contact arm 4 to its normal or mid-position. In order that this coil should have the desired characteristic of a pullwhich increases with its time of energization and also a pull, or energization, which continues a predetermined time after the contact arm has been returned to its normal position, I provide special means for energizing this winding. The illustrated" embodiment of this means comprises a two electrode, hot cathode, arc discharge type rectifier 15 whose anode circuit is continuously energized through coil 14 and whose cathode heating circuit is energized in accordance with the operation of the pilot motor 8, that is to say,

in accordance with the engagement of one, or

the other, of contacts 5 or 6. In this way I and consequently the heating, of the cathode I and thereby increases the rectifier current and consequently the current through the restoring coil 14. As a convenient way of securing the proper operating voltage for the cathode of the rectifier, I energize it through an autotransformer 17 whose primary circuit is in the return conductor for the current passing through contacts 5 or 6.

In Fig. 2 is illustrated a modified arrangement in which the cathode heating current is controlled directly from the current in motor 8 by means of a suitable current transformer 18 connected in the return conductor of this motor circuit.

The operation of the arrangement illustrated in Fig. 1 is as follows. Considering first the ordinary operation and ignoring the efiect of ballast resistance 13, and restoring coil 14, contact-making voltmeter l is so adjusted that when normal voltage exists on main circuit 3 the contact arm 4 is in its normal position and contacts 5 and 6 are disengaged. When the voltage of circuit 3 falls the pull of main coil 2 is weakened and contact 6, which is usually referred to as the raise contact, is engaged, while when the voltage of circuit 3 exceeds its normal value, the pull of coil 2 is increased and contact 5, which is usually referred to as the lower contact, will be engaged. Engagement of raise contact 6 completes the energizing circuit for the right hand relay 7 and also completes an energizing circuit for holding coil 10. These circuits can be traced from the left hand side of the secondary winding of transformer 12 through holding coil 10 and the operating coil of the right hand relay 7, in parallel, through contact 6, to the pivot of arm 4 and then back to the other side of the primary winding of transformer 12. The operation of right hand relay 7 completes an energizing circuit for motor 8. This circuit is such as to cause motor 8 to operate regulator 9 in a manner to raise the voltage of main circuit 3. The effect of holding coil 10 is to cause a firm engagement of contact 6 so that the vibration of the meter, which is usually mounted on a panel board which is subject to vibration, does not cause an intermittent making and breaking of the contacts and consequent injurious arcing between them. The operation of regulator 9 continues until the voltage of circuit 3 rises sli htly above normal, when the increased pu l of coil 2 will overcome the pull of holdother reason why this range is provided is ing coil 10. When this happens, contact 6 will be disengaged and arm 4 will return approximately to its mid-position. It should be noted that the contacts 5 and 6 are so arranged that, in ordinary practice, it requires a difference of about two volts to move contact arm 4 from engagement with one ofthese contacts toengagement with the other of the contacts. This is necessary because on most commercial circuits there are continual small voltage fluctuations which it isnot necessary to regulate and which, if it were attempted to regulate them, would cause practically continuous operation of the regulator. An-

that if the contacts were set closer, so that the meter would be sensitive to smaller changes in voltage, the usually present vibration of the meter would cause continual disengagement of these contacts without actual voltage changes occurring.

In the same way, when the voltage ofcir cuit 3 rises above normal the meter 1 will cause engagement of the lower contact 5,

- thereby simultaneously energizing the left "hand relay 7 and holding coil 11. This will cause motor 8 tooperate regulator 9 in a manner to lower the voltage while holding I tacts. As time goes on and resistance 13 in creases, it cuts down the current in coil 10 or 11 and consequently decreases its holdingeffect. This weakening of the pull of the holding coil results in an improved regula tion in that the voltage of the main circuit does not have to depart, as much as heretofore, from normal before the pull of the holding coil will be overcome and the contact-making meter arm will return to substantially its normal position. Further more, the weakene'd pullpf the coil permits of a quicker break of the contacts thus minimizing contact sparking' In addition, the strong initial holding effect of the holding coil insures that the contacts of the meter will not be broken immediately after they are made, either due to vibration or because of voltage changes on the main circuit. This is of advantage in that thelcontacts of the meter do not have to break the relatively heavy initial inrush current to the coils of relays 7 and also these relays do not have to break the relatively heavy starting current for motor 8. a

The operation of the restoringcoil 14 is as follows. As soon as one, or the other, of contacts 5 or 6 are engaged current flows through auto-transformer 17 thereby sending current through the filament of valve 15 and ballast resistance 16, in parallel. As soon as the filament becomes hot enough to emit electrons, rectified current will'flow through magnet coil 14 and urgethe arm 4 of meter 1 to its normal mid-position. As resistance 15 becomes heated, and its value increases, more and more heating current will flow through the filament of the rectifier, and consequently more and more current will flow through the rectifier and the pull of magnet 14 will become stronger. At the same time the regulator 9 is changing the voltage of circuit 3 in such a-manner that the pull of coil 2 is also acting against whichever holding coil is energized, thereby to move the contact beam 4 to its normal position. At a predetermined time the combined pulls of coils 2 and 14 will overcome the pull of the holding coil and contact beam 4 will be moved to its normal mid- ,position. By proper adjustment this restoration of the contact beam 4 to its normal posi-- tion may be made to occur before the voltage of the circuit hasbeen restored to exactly normal, thereby permitting any lost motion or coasting effect in the operating means of the regulator to complete the regulation. As soon as contact beam 4 moves to its mid- .position auto-transformer 17 will be deenergized, but due to the thermal capacity of the filament of rectifier 15 current will continue to flow in restoring coil 14 for a predetermined time. This introduces what I'referred to as a hold-over, or hang-over, effect which ositively prevents operation of the regulatmg system for a predetermined time after it has operated so that, in effect, it waits a predetermined time to see whether the necessary regulation has been achieved. This givestime for. any lost motion or coasting effect in the regulating mechanism to make themselves felt in completing theregulation. While it is not usually very pronounced in regulators of the induction type as shown, it

is often a considerable factor in other regulating arrangements.

In the modified arrangement illustrated in Fig. 3, I employ an induction type relay 19 as a contact-making voltmeter. This relay may be any type of voltage responsive induction type relay. In the illustrated embodiment it is shown as a single phase wattmeter type relay having a pivotally mounted induction disc 20 which is acted on by a motor element comprising the usual wattmeter potential. winding 21 and current winding 22 connected, through a suitable current limiting resistor 23, to also respond to the same voltage as that to which potential winding 21 responds. Both these windings are connected to respond to the voltage of a main regulated circuit, in this case a three phase alternating current circuit 24. This motor element of the relay is in effect a phase split- .ting device for producing a moving magnetic field for operating disc 20. It will be assumed that the torque produced by this motor is counterclockwise and consequently a restraining spring, or other suitable element, 25 is connected to oppose the torque of the relay. Instead of providing the usual permanent magnet type of damping or anti-hunting means for relay 19, I provide an alternating current winding 26, on a preferably magnetically saturated core member 27. \Vhen energized, coil 26 and core 27 produce the equivalent of the permanent magnet damping means, but by making this damping means electromagnetic I can cause its deenergization at times when the relay contacts are closed, whereby it is possible to obtain a relatively quicker break of the contacts.

Arranged to be operated by disc 20 is a contact arm 28 having a normal neutral position and being arranged to bridge a pair of lower contacts 29 or a pair of raise contacts 30, depending respectively upon whether the voltage of circuit 2% is above or below normal. Lower contacts 29 are connected to complete energizing circu ts for a holding coil 31 and the operating coil of a relay 32 when they are bridged. As shown these 'coils are connected in parallel across one of the phases of main circuit 24. Likewise, raise contacts 30 are arranged to complete the energizing circuit of a holding coil 33 and the operating coil of a relay 34'. A positive temperature coefiicient resistance 35, such as an iron wire ballast resistance, is connected in series with holding coils 33 and 31. The function of this resistance is the same as the function of resistance 13 in Fig.1.

Relays 32 and 34 control reversing contacts for determining the direction of operation of a servo or pilot motor 36. As shown, this is a three phase motor and relays 32 and 34 control its direction of rotation'by reversing its phase connections' to the main circuit. Motor 36 is mechanically connected to operate a three phase regulator 37 which may be of any well known type and which is illustrated as of the induction type. Relays 32 and 34 are also provided with normally closed back contacts which are in the energizing circuit of the damping coil 26. In this manner whenever relay 19 is actuated to energize one or the other of these relays the damping means will be incapacitated thereby permitting a quicker break of the relay contacts than would be the case if the damping means were active at that time.

The restoring means for the relay 19 is similar in principle to the restoring means of Fig. 1; It comprises a restoring magnet 38 which cooperates with an armature 39 associated with the pivotally mounted element of the relay. This magnet is connected to be energized from one of the phases of the main circuit 24 through a rectifier 4.0, which is similar to rectifier 15 of Fig. 1. The flow of current to rectifier 40 is controlled by the heating of its cathode which in turn is controlled through a transformer 41 which is connected in parallel with one of the phase windings in the motor 36, so that itis only energized when this motor is energized. With this arrangement the restoring force of magnet 38 quickly attains its maximum value, so that there is no gradual increase in restoring effect as in Fig. 1. However, the hold-over, or hangover, effect is present, due to the thermal capacity of the cathode of the rectifier which continues to emit electrons a predetermined time after motor 36 has been deenergized.

The operation of the arrangement illustrated in Fig. 3, is as follows. With normal voltage on supply circuit 24 the. torque produced by the motor element on disc 20 just balances the counter-torque of spring 25 and arm 28 is in its normal mid-position. Damp ing means 2627 is energized and prevents vibration and oscillation of the rotatable elements of the relay. If now the voltage of circuit 21 increases above normal, an unbalanced counterclockwise torque is produced and lower contacts 29 will be bridged, thereby energizing relay 32 and causing motor 36 to operate regulator 37 in a manner to lower the voltage. At the same time holding coil 31 is energized to hold lower contacts 29 firmly in engagement with arm 28. Just as in Fig. 1, the heating of resistance 35 due to the flow of current through the holding coil gradually increases its resistance thereby decreasing the pull of. coil 31 so that a firm initial holding effect is obtained which tapers as' time goes on and permits a more rapid, easy break of the contacts. As soon as relay 32 closes, its back contacts break the circuit of the damping magnet 26, which of course performs no-useful function while contacts 29 are bridged by arm 28. As soon as relay 32 completes the energizing circuit for motor 36, transformer 41 is energized and rectifier 40 begins to pass current through restoring magnet 38. This magnet is arranged to overcome the pull of holding coil 31 in a predetermined time and thereby restore contact arm 28 to its normal position. Due to the hold-over, or hang-over, effect of the re storing means, this arm will be held in its mid-position for a predetermined time, thus giving the regulator and all its control means time to complete the regulation due to any overrunning characteristics which it may possess. If after the completion of the predetermined time the regulation is found to be incomplete the above operation will be repeated llf] so that for fairly large increases in voltage the regulation may take place in one or more steps.

The operation of the arrangement when the voltage of circuit 24 falls below normal is similar. Thus an unbalanced clockwise torque will be produced whereby arm 28 bridges raise contacts 30. This simultaneously energizes holding coil and relay The operation of relay 34 breaks the circuit of damping magnet 26 and at the same time completes the energizing circuit of motor 36 which now operates in the reverse direction because the regulator must act to raisethe voltage of circuit 24. The means for tapering the pull of holding magnet 33 operates the same as before, as also the means for energizing the restoring means 38.

The principal advantage of using an induction type relay is that it is not so susceptible to panel vibration as is the usual solenoid type operated contact-making voltmeter.

Fig. 4 illustrates av modification of the arrangement shown in Fig. 3. In this arrangement the rectifier 40 and transformer 41 are eliminated and restoring magnet 38 is connected directly in parallel with one of the phases of motor 36, with a ballast resistance 42 connected in parallel therewith. lVith this arrangement the hold-over, or hangover, effect, which sometimes may not be desired, is eliminated while the feature of having the pull of the restoring magnet 38 gradually increase with time provided. Thus as motor 36 is energized most of the current will be by-passed by resistance 42 at the start, but as this resistance increases due to its rise in temperature, as the current flows through it, more and more current will be shunted through the magnet 38.

While I have shown and described particular embodiments of my invention, it will I be obvious to those skilled in the art that changes and modifications may be made without departing from my Invention, and I therefore ann in the appended clalms to cover all such i'changes and modifications as fall within the true spirit and scope of my invention. I

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

1. A circuit controlling relayincluding, a movable circuit controlling element having a normal position. and a circuit controlling position, means operative when said element is moved-to its circuit controlling position for urging it to its normal position, and

" means for causing the force of said last mentioned means to increase with its time of action.

2. A circuit controlling relay including, a movable circuit controlling element having a normal position and a circuit controlling position, means operative when said element assumes its control position for urging it to its normal position, said means acting to maintain said element in its normal position a predetermined time after it returns to said normal position. i

ln combination, a relay having relatively movable cooperating contacts, a holding coil adapted to hold said contacts in firm engagement when it is energized, and a re sistance having a non linear volt-ampere characteristic connected to said holdingcoill l. A contact-making voltmeter having a pivotally mounted contact arm, a pair of contacts arranged for cooperation with said contact arm, holding coils associated with said arm, and a ballast resistance in series with each holding coil. V

5. A circuit controlling relayhaving, in

combination, a movable circuit controlling element with a normal position and a circuit controlling position, a holding coil arranged to urge said element to its circuit controlling position when said coil is energized, an energizing circuit for said coil which is completed when said element is moved to its circuit controlling position,

and a temperature variant resistance connected to said circuit in such a manner as to cause a tapering decrease in energization of said coil after said circuit is completed.

6. A contact-making relay having a movably mounted contact arm, damping means for preventing vibratory motion of said arm, and means operative when said arm makes contact for preventing the operation of said damping means whereby it is possible to obtain a relatively quicker break of the c011- tacts of said relay. y

7. In a regulating system, a fixed contact, a movably mounted contact arm arranged to he moved into contact-making engagement with said contact arm when the value of a condition to be regulated departs from a predetermined value, damping means for countel-acting vibratory motion of said arm, and means for incapacitatingsaiddampingmeans when said arm is in contact-making engage ment with said fixed contact whereby it is possible to obtain a relatively quicker disengagement of said contacts.

8. In combination, a movable element having a normal position and a control position, electrically operated restoring means for urging said element to its normal position when said element is moved to its control position, means for causing continued operation of said restoring means a predetermined time after said element has reached its normal position, said last mentioned means comprising an electric discharge type rectifier with a filamentary cathode which has an appreciable thermal capacity, and means for energizing said cathode when said element is in its contact position and for deenergizing means which is actuated when said controller attains its circuit controlling position, a magnet which is energized when said controller attains its circuit controlling position for holding said controller in its circuit controlling position, and means actuated when said circuit controller attains its circuit controlling position for applying a gradually increasing force to said controller which tends to move it to its normal position.

10. A regulating system including in combination, a circuit controller having a normal position and acircuit controlling position to which it is moved by deviations from normal of a condition to be regulated, regulating means which is actuated when said controller attains its circuit controlling position, a magnetwhich is energized when said controller attains its circuit controlling position for holding said controller in its circuit controlling position, means for giving said magnet atapering energization which is initially strong, and means actuated when said circuit controller attains its circuit controlling position for applying a force to said controller which tends to move it to its normal position.

11. A regulating system including in combination, a circuit controller having a normal position and a circuit controlling position to which it is moved by deviations from normal of a condition to be regulated, regulating means which is actuated when said controller attains its circuit controlling position, a magnet which is energized when said controllerattains its circuit controlling position' for holding said controller in its circuit controlling position, means for giving said magneta tapering energization which is initially strong, and means actuated when said circuit controller attains its circuit controldition varying means for at least anappreciable minimum time for each regulating operation, and means for causing said device to stop actuating said condition varying means before complete regulation has been accomplished.

13. A regulator having, in combination, a master circuit controller having a normal my hand.

FRANK T. COLDWELL.

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