US1184266A - Voltage regulation. - Google Patents

Description

E. O. SCHWEITZER. VOLTAGE REGULATION.

APPLICATION mm JULY 23.1914.

1,184,266. Patented May23,1916.

2 SHEETSSHEET l.

E. O. SCHWEITZER.

VOLTAGE REGULATION.

APPLICATION FILED JULY 23.1914.

1,184,266. Patented May23,1916.

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EDMUND O. SCHWEITZER, OF CHICAGO, ILLINOIS.

VOLTAGE REGULATION.

Specification of Letters Patent.

Patented May 23, 1916.

Application filed July 23. 1914. Serial No. 852,629.

To all whom it may concern Be it known that I, EDMUND O. Sonwnrn a citizen of the United States, residing at Chicago, in the county of Cook and State of Illinois, have invented certain new and useful Improvements in Voltage Regulation, of which the following is a full, clear, concise, and exact description, reference being had to the accompanying drawings, forming a part of this specification.

The subject matter of the present invention is a system of voltage regulation.

In. the consumption of electrical power it is often desirable to use the electric current for different classes of service, that is, loads having different characteristics. A common illustration of the above is the use of induction motors for furnishing power and lamps for lighting purposes on the same premises. Economy of construction and installation would demand that both of these loads be fed from a single transformer interposed between the power line and the consumption circuits, but it is well known that the characteristics of an induction motor, or other inductive apparatus, for furnishing power or for similar purposes, are of a type entirely unsuitable for conjoint use with a noninductive load or a load of unstable characteristics such as a lamp load. Heretofore, it has been found impracticable to supply both loads with current from the same mains, due to the fact that voltage regulation of the circuit'is impossible on account of the characteristics of the varying load drawn by the motor.

It is one of the objects of the present invention to provide means which will allow of conjoint operation of an induction motor, or similar type of apparatus, and a lamp load or other apparatus having a similar characteristic from a common supply circuit.

It is another object of the invention to provide a general method of voltage regulation in one branch of a split load circuit to prevent any considerable voltage fluctuation, even when relatively great variations of voltage occur in other branches.

It is a still further object of the invention to provide means for regulating automatically the voltage in one branch of a transformer circuit while a variable load is being drawn in another branch circuit.

The subject-matter of my invention iswidely applicable to various situations, and

may be embodied and practised in a great variety of forms.

I have illustrated in the accompanying drawings, in Figure 1, one embodiment in which my invention may appear; Fig. 2 is a modification of the same; Fig. 3 is a diagram of a modification employing the windings of the induction motor to secure regulation; Fig. 4 shows a modification of F ig. 3; Fig. 5 is a diagram of a modification for obtaining automatic regulation only upon the occurrence of excessively heavy current in the motor circuit.

In order to make clear the reason for employing my invention, I will briefiy describe the characteristics of an induction motor and of a lamp load.

The induction motor, as is well known, is, in fact, a tr: isformer, the secondary of which is subject to motion at a speed depending upon voltage as one factor. A decrease in voltage impressed upon the motor results in ardecrease of voltage in the secondary or rotor winding, a consequent diminution of the currenttherein accompanied by a decrease of torque, and a consequent lessening of speed.

In .most situations in which an induction motor is employed, a variation in speed of a few per cent. is not found objectionable, inasmuch as the induction motor is a variable speed device at best. A lamp load, on the contrary, is almost entirely a resistance load but of an unstable character. It is well known that the change of resistance, due to increase of temperature, of an incandescent lamp, as well'as of an arc lamp, tends to an inherent instability. Especially is this true of the incandescent light which is in common use in practically all situations. A variation of voltage upon an incandescent light affects the same very unfavorably and a few per cent. voltage variation causes a very great fluctuation in the value of the light given 05. Hence, when an induction motor is connected to lighting mains, the inductive effect of the motor causes a fluctuation in the voltage of the circuits with a consequent flickering of the lamps. The current drawn by the motor causes an inductive and ohmic voltage drop in the connected winding of the transformer and a decrease of voltage at the transformer terminals. As a consequence, the voltage impressed upon the lamps is considerably decreased and a very pronounced dimming occurs. This has been found so objectionable that in practice prior to my invention it has been impossible to secure satisfactory service from such an installation.

In Fig. 1, I have indicated-the high tension or primary mains 1, 2, connected to the primary 3 of the transformer 1, the secondary 5 of which is connected to the load by the leads (3, 7. The load illustrated in this connection consists of the induction motor 8 and a number of lamps 9 which may be of the are or incandescent or any other preferred type. The induction motor 8 is bridged across the mains 6, 7, in series with a motor controller 10 which may be of any preferred type. In order to secure regulation of the voltage across the lamps 9. I have inserteda current transformer 11 having a primary 12 connected in series with the lamp load and the secondary 13 connected in series with the induction motor 8. In order to regulate the value of the regulating eleetromotive force, which is induced in the primary 12, as will be explained further, I have connected an impedance 14in shunt of the primary winding 12. The impedance 1% is made practically pure resistance, for reasons which will be set forth later.

The operation of the system above described will. now be explained.

Assuming that only the lamps 9 are con nected to the secondary of the load transformer, practically the only drop in the voltage in the circuit 67 will be that caused by the current drawn by the lamps and may be designated as a pure IR drop. This neglects. of course, the very slight inductive effect in the impedance 14 and the winding 12 of the current transformer 11. It is to be noted that the turns in the winding 12 are of a low resistance, and comparatively few in number, consequently the IR drop caused in this part of the circuit will not be considerable. The current flowing in the winding 12 would induce an electromotive. force in the secondary 13 which is in series with the motor, but, as this circuit is now open, no effect will -be produced thereby. Assume, as a second condition of the system, that the load consists of the motor 8; in this case the load is of an inductive type due to the transformer and leakage effect in the motor 8, and a considerable drop of voltage at the terminals of the transformer 5 may be occasioned, both by the inductive character of the winding 13 and the load 8 and by the IR drop, due to the resistance. of the circuit including the winding and the load. The secondary 13 of the transfornua- 11 comprises a relatively large number of turns, and, consequently, includes more resistance than the winding 12, but, in view of the fact that the motor 8 is inherently a variable speed apparatus, a decrease in speed, due to this drop of voltage, will not be objectionable, and may, if desired, be compensated for by manipulating the motor controller 10. It is to be noted that a voltage is generated at. this time in the primary winding 12, but as the lamps are disconnected no current can flow therethrough. This voltage is of a low value, due to the relation of the number of turns. A current may circulate through the impedance 1 1 but this is a minor loss of power. However it is beneficial in effect tending to reduce the inductive action of the transformer 11, so that current can more readily flow theretln'ough. Assume as a third condition of operation, that the motor 8 and the lamps 9 are connected simultaneously to the load transformer 1. The tendencies above described for each circuit are now combined into a single effect. The greater the current drawn through the secondary 5 of the load transformer l, the greater will be the drop of voltage across the terminals thereof. As a consequence. the voltageimpressed upon both the motor 8 and the lamps 8) will be decreased. This is caused chiefly by the III drop. It will be noted that the current flowing through the secondary 13 of the transformer 11 induces an electromotive force in the winding 12 which is shunted by the impedance 14. It is to be understood that there is as little inductance as possible in the impedance. Nearly pure resistance is desirable in order to obtain the maximum effect. I have illustrated impedance rather than pure resistance to show the art that the eilect is not necessarily dependent upon pure resistance only, but may be gained even though there be appreciable inductance in the circuit. It is to be noted, however, that the en'lployment of an iron core in the impedance 1:1- is highly undesirable, because the magnetization curve of iron is not a straight line. As the permeability of iron varies at different stages of magnetization, an iron core introduces complications which cannot be compensated for. The electromotive force generated in the winding 12 is considered separate and distinct from the voltage drop caused by current flowing from the winding 5. This electromotive force may be considered as being impressed upon the shunt 14, tending to cause a local current to flow therein. Hence, the added voltage which is transferred from the motor circuit may be considered as the IR drop across the shunt 14, due to the circulating current that would flow because of the regulating voltage alone. If an inductance were shunted across the winding 12 the voltage added to the voltage of the winding 5 would be due to both the electromotive force of the winding .12 and the inductive kick of the shunt. As a furx core'of the transformer 11 for producing a somewhat similar effect. A number of taps 16 are led out from the winding 15 and an "adjustable contactor 17 is arranged to make connection with any one of these taps, so as to impress a variable voltage upon the circuit 18, which is connected on one side to the winding 15 and on the other to the contactor 17. A resistance is connected in series with thecircuit 18, and the value of this resistance 19 'may be controlled in any preferred manner, as by a rheostat arm 20 to vary the resistance of the circuit 18, and the consequent shortcircuiting effect of the winding 15. In accordance with the wellknown action of the transformer, this variable' short-circuit acts as a shunt of greater or less value upon both the primary and secondary windings of the transformer 11,

I and in this manner the regulating effect exerted upon the circuit of the lamps 9 may be varied to produce the most suitable effect.

The operation of the 'load circuits shown in Fig. 2 is similar to that described in connection with Fig. 1. The shunting means, which is shown in Fig. 1 as a direct shunt and in Fig. 2 as an inductive shunt, operates both' 'as an adjusting means for the voltage impressed upon the lamps and acts as well to .aidthe passage of current through the windings 'of the current transformer 11 when each load circuit operates alone.

In the diagram shown in Fig. 3, regulation is secured by placing an additional ,winding 21 in inductive relation to the stator winding 20 of the induction motor 8. This winding 21 is connected in series with the lamp load 9 and corresponds with the winding 12 of Figs. 1 and 2. In thismanner, it is possible to secure regulation without the use of an additional transformer, as the iron of the induction motor may serve both as the frame of the motor and as the core of a transformer for securing regulation. An inductance 22 and a resistance 23 are bridged in series across the ter minals of the coil 21 and by manipulating the contacts 24 it is possible to adjust the influence of the winding 21 upon the lamp load circuit 9. It can readily be seen that the electromotive force generated in the winding 21 is dependent upon the amount of current fiowing'in the stator winding 20.

In Fig. 4, instead of employing a direct shunt upon the winding 21, I have shown an additional winding 25 in inductive relation to the stator winding 20 and in series with an inductance 22 and resistance 23, to secure an adjustment of the electromotive force impressed upon the winding 21 by means of an inductive shunt, this action being similar to the inductive shunt 18 shown in Fig. 2.

In Fig. 5, I have shown a system in which the inductive effect of the regulating transformer 11 may be removed from the circuit, if so desired, during the normal operation of the system. I accomplish this by shortcircuiting the winding 13 of the regulating transformer at all times, except when a heavy current is flowing through the induction motor 8, as in starting. This may be accomplished by the use of a solenoid switch having a winding 27 in series with the motor 8 and controlling by means of the bridge 28 the contacts 29, which are included in a short-circuit of the winding 13. It is desirable that the resistance of the short-circuit about the winding 13 be made of very low value, but of considerable inductance. I have shown the inductance 26 as'being connected in series with the contacts 29. The operation of this system is as follows: When the motor 8 is started, an excessive current will be drawn thereby, this current being traced in parallel through the winding 13 of the transformer 11 and the short-circuit thereabout, through the windings 20 of the motor 8, solenoid 27, back to the secondary 5 of the load transformer 4c. The current is sufficient to operate the electromagnet c switch 28 and thereby open the short-circuit about the winding 13 of the regulating transformer 11. As a consequence, the regulating electromotive force is generated uuring the time of the excessive starting current. As. soon as the current in the motor 8 becomes normal, the electromagnetic switch 28 is again closed and the inductance of the transformer 11 is thereby largely removed. This action is practically instantaneous and regulation is not dependent entirely upon the opening of the electromagnetic swltch 28, inasmuch as a sudden rise of current,

due to starting, is opposed by the inductance 26 to such an extent that a great part of .the 'circuit where such sacrifice is permissible.

The structures shown in the figures embody broadly a new method of regulation. It can be seen that the voltage generated 1n the winding 12 by a current fiowlng 1n the winding 13 is in proportion to the current drawn in the branch containing the motor 8, and may be made to compensate to any degree for both the IR drop caused by such current through the winding 5 of the load t'ansformer and may compensate, as well, for the inductive effect caused by the fluctuations of the load which would affect the lamps 9. This method may be more briefly described as consisting of impressing an electromotive force upon one branch of a transformer load circuit in accordance or in proportion, or in any desired relation, to the amount of current drawn by another branch of the load circuit. The electromotive force so impressed has a component in phase with the electromotive force of the main load transformer winding and is varied to compensate both for the IR drop and for the inductive effect which the variations in current in the second branch may cause in the load transformer winding.

It will be apparent to those skilled in the art that the invention may be practised by the employment of different apparatus from what I have shown and described but I consider the same to come within the spirit and scope of my invention. It is also not necessary that a load in the one branch consist of an induction motor, as any other type of apparatus, which may be found suitable, and in which a low percentage decrease in voltage will not be found objectionable, may be employed. But it is also evident that the other branch of a circuit need not necessarily employ lamps or apparatus of a purely non-inductive character, as any form of apparatus, which it is desired to maintain at a constant voltage, may be employed in this circuit. A greater number of branches may be employed as desired. It will also be ap parent that I may employ an auto-transformer instead of a double winding transformer shown in the figures of the drawing. It is important only that the windings be arranged, as indicated, with a greater number of turns, which, in the drawings, I have designated as the primary winding of the current transformer in series with the motor load and the winding of fewer turns corresponding to the winding which I have designated as the secondary winding of the current transformer in the lamp load. All of the above variations I consider to be fairly within the scope and spirit of my invention.

I consider my invention to be broadly new and desire the claims to be read as broadly as is consistent with the state of the art.

I claim:

1. In combination, feeder mains, a motor load branch and a lamp load branch having a variable number of lamps individually connected in pa 'allel to said mains, an iron core, a winding on said core in series with said lamp branch, a winding on said core in series with said motor branch, and a substantially non-inductive shunt for reducing the impedance of said lamp branch winding when said motor load is disconnected.

2. In combination a service t'ansformcr having a substantially constant voltageimpressed thereupon, a motor load branch and a lamp load branch connected in parallel to said transformer, said lamp branch comprising a plurality of constant voltage lamps adapted to be individually connected in parallel, windings in series with each of said branches, a magnetic core interlinking said windings and a substantially non-inductive shunt connected across the terminals of said lamp branch winding.

3. In combination a service t'ansformer having a substantially constant voltage impressed thereupon, service mains, a motor load branch connected .to said mains, said branch havingan induction motor connected in series therewith, a lamp load branch connected in parallel in said motor branch, said lamp load branch comprising a plurality of lamps adapted to be individually connected in parallel, a magnetic core, windings on said core in series with each of said branches, and a substantially non-inductive shunt connected across the terminals of the lamp branch winding.

In witness whereof, I hereunto subscribe my name this 13th day of July, A. D. 1914.

EDMUND O. SCHVVEITZER. Witnesses:

LESLIE IV. FRICKE, ERNEST IV. RAIALEE.

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