US1295887A - System of distribution. - Google Patents

Description

C. LE 6. FORIESCUE. SYSTEM OF DISTRiBUTION.

APPLlCATlON FILED NOV. 7. 1916.

1 Patented Mm: 4,1919,

\NVENTOR WITNESSES:

Char/e5 L96: FEW fem/e C. LE G.FOR1ESCUE. SYSTEM OF olsmsunow'. APPLICATION FILED HOV.7',19\6.

Patented Mar. 4, 1919.

WlTNESSESZ \NVENTQR Char/es L26, Forfescue a. BY

ATTORNEY I UNITED STATES PATENT OFFICE.

CHARLES LE G. FORTESCUE, OF PITTSBURGH, PENNSYLVANIA, ASSIGNOR T0 WESTING- HOUSE ELECTRIC AND MANUFACTURING COMPANY, A CORPORATION OF PENNSYL- VANIA.

SYSTEM or DISTRIBUTION.

Patented Mar.4, 19 19.

Application filed November 7, 1916. Serial no. 129,975.

To all whom it may concern Be it known that I, CHARLES LE G. Fon'rnscUE, a subject of the King of England, and a resident of Pittsburgh. in the county of Allegheny and State of Pennsylvania, have invented a new and useful Improvement in Systems of Distribution, of which the fol lowing is a specification.

y invention relates to electrical distributing systems and it has special relation to alternating-current distributing systems that are subjected to varying loads operatingat variable power-factors.

More particularly, my invention relates to alternating-current railway systems which embody means for automatically maintaining fixed relations between the voltages impressed across the trolley conductors and the rails and across the return feeder-conductors and the rails, under all load conditions. At the same time, railway systems embodying my invention substantially minimize the resultant inductive effects that arise from the flow of the load currents therein. These inductive effects, unless suppressed. may inipose disturbances upon circuits adjacent to the railway systems which will seriously interfere with the satisfactory operation of suc adjacent circuits.

Many systems have heretofore been proposed for minimizing the inductive dist-urbances impressed upon oneelectrical circuit by another adjacent circuit but complete neutralization of these inductive efi'ects has not been obtained in all cases. A particular system used in connection. with electric railways, which has given fairly good results, embodies the use of series transformers to inductively interlink the trolley conductor and the track circuit. In consequence thereof, the return How of the trolley currents is confined to the track rails or to portions of the earth closely adjacent tofthe tracl' rails. In this manner, the zones of distu bing inducing influences that arise from'f the return flow of the power currents are restricted. Moreover, the returning currents are confined to limited regions close to the trolleynconductor Where their induct' o effects on an adjacent intelligencetransmission circuit minimize or neutralize, to-solne extent, the disturbances occasioned by the i .66,733, in which transforn'lers which Another system in which the trolley concircuit are interlinked uctor and the track and which is proposed for n'iinimizing the inductive disturbances occasioned by the flow of power currents in an electric railway system, is disclosed in a eo-pending application of A.'VV..C0pley and Charles Le G. Fortescue, Serial No. 66,733, filed December- 14. 1915 and assigned to the Westinghouse Electric and anufacturing Company. This latter system comprises a feeder conductor, a trolley conductor and a track circuit. The first two conductors are so positioned with respect to an adjacent intelligence-transmission circuit, which is to be protected against inductive disturbances arising from the railway system, that the re sultant electromotive forces induced therein by reason of the current flowing in the trolley and feeder conductors shall be neutralized to such a decree as will not seriously interfere with the operation of. the intelligence-transmission circuit. Moreover, the trolley and feeder conductors are inductively interlinked, either with or without the track circuit, through transformers of a character similar to those employed in connection with the system disclosed in the above-mentioned patent.

An object of my present invention is to provide an improvement upon the aforementioned systems and-particularly upon the system covered by application Serial Yo.-

disturbances tending to arise from the flow of alternating currents in the-distributing system may be substantially neutralized. In the system of the present invention, the voltages consumed by the inductive reactive-drops obtaining in the are connected between the trolley conductor are compensated for by supplyin leading currents of proper values from an independent source to the system. In consequence thereof, the voltages obtaining between the trolley conductor and the track circuit and between the return feeder and the track circuit are maintained at afixed ratio, usually a one-to-one ratio, under all load conditions.

and the return feeder the feeder t by means ofthe character are induced in the telephone circuit will be substantially neutralized by inducing therein -equal and oppositelyalirected electrolnotive forces, under tribution on the railway system.

'lhe telephone circuit 20 is assumed to be unit'ormlv and equally spaced from the trollev condii tor land the. return t'eeder l. The track circuit-2. in this instance. is held at an electrical potential midway between the potent ial of the trolley conductor 1 and that of transformers ll, 12, 11 and 12". since the. track circuit 2 is connected to conductors. such as the conductor 1%. which represent the common midpoints between the inducing and induced windings of the trans'tr'nn'iers. wt-enough, the rat-io'between the electroniotive torces obtaining in the inducing and induced windings of each of these transformers is unity. The electromotivc force induced in the winding 13 is, however, equal to the electroniotivc force impressed upon the winding" 18 only ,under ideal conditions. The primary and secondary voltages of at equal only when the reactivedrops in tlein arecom ensated for. Since the inductive reactive-drop in a transformer 'aries with varying loads it is essential to supply means for automatically compensat ing for the varying reactive-drops 0ccasioned by different load conditions, in order that the electromotive forces obtaining in the windings 13 and 18 may bear a constant relation to each other which, in this particular case, is a oiie,to-one ratio.

In order to'con'ipensate for these inductive reactive-dropsin the transformers, a synchronous condenser 21 supplied. One terminal of this condenser co mected by means of a conductor toyr mid-tap 23 on the primary winding 9 of the series transformer 8*. chronous condenser is connected by means 01 ,a conductor 24 to the track section 3 by means of a bond The power-factor of the current delivered to the system by the condenser 21 is varied automatically by means of a regulator of the viln'ating-eontact type. This, in turn, controls the exciting current supplied to a field winding 26 of the condenser 21. The condenser 21. int-his instance, serves in tihe same manner as a power-factor-corrw-ting device the tune ions of which are well kiown.

The regulator is oi a form well knonln in the art and compris s an electrolnagnqt 97 excited by a voltagei transtormer 28 and a second eleetromagnet 29 having two coiIs 30 and 31. The electronuignet "27 and th coil 31 of the electromagnet Q are excite l by means of the transformer 28. the secondary winding 32 of which is connected in circuit therewith. The winding 32 is influenced by two diti't' rentially wound prin'iary windings all conditions of load' dis transformer of this tor reference The other terminal of the syn- 33 and 34:, the former being connected between the trolley conductor 1 and the track circuit 2 and the latter being connected between the return feeder 4? and the track cir cuit 2.

The coil 30 of the electromagnet 2!) is excited by means of a current transformer 35. the primary winding 36 of which is connc'cted in series with the trolley conductor 1.

The vibrat'ing-contact type regulator is, therefore, influenced by the currents obtaining on the'railway circuit and also by the difference in the voltages obtaining between the trolley conductor and the track circuit and the return feeder and the track circuit. The regulator serves to vary the efl'ective resistance of a resistor 37 connected in series circuit with a field winding 38 of an exciter 39. The exciter 39, in turn, supplies the exciting current to the synchronous condenser 1 By varying the effective resistance of the resistor 37, the current supplied to the field winding 26 of the condenser 21 is automatically controlled in order tocon'1pensate for the inductive reactive-drop obtaining in the transformers.

The form of regulator shown is well known in the art and further description of it is not deemednecessary. For a complete description however, of this type of reguhn may be had to U. S. Patent No. 1,117,576. I

To illustrate the electrical conditions obtaining in the railwaysystem of Fig. 2- at a certain instant, assume that a locomotive 4O occupies a mid-position on the track section 3.

The propulsion currents, which are represented by full-line arrows 41, flow through the winding 9 of the transformer 8 along the trolley conductor 1 and a trolley pole 42 to the locomotive 40. At this point, the propulsion currents divide into two equal p'0r-' tions,that flow along the track c'rcuit 2 inopposite directions. Since it is 1 resumed that the track circuit compris s'uniform conductors and the train 40 occu i s a mid position thereupon, as mentioned above, onehalf of the propulsion current flows through the impedance bond 16, a conductor 43, the primary winding 18 of the transformer 12, a conductor 44 and the secondary Winding 10 of the series transformer 8 to the return feeder The other half of the propulsion current flows along the track circuit :2, the impedance bond 16, the conductor 15 and the primary winding 18 of the transformer 11 to the return feeder 4.

It will be apparent, therefore, that the propulsion currents flowing in the trolley conductor 1, intermediate the generator 5 and the points A-A of the system, is equal in value to, and opposite in direction from, that of the propulsion current flowing in the corresponding portion bf the return feeder 41. Therefore, the inductive effects arising from the flow of the propulsion currents over this portion of the railway system are neutralized if the reactivealrop obtaining in the transformer 12 is compensated for. This inductive reactive-drop is compensated for because the condenser 21 furnishes sufficient leading current to the transformer system to overcome the inductivedrop. caused therein by the inductance of said transformer system. However, in order to efficiently obtain the desired compensation. itis necessary that the condenser 21 be connected to the transformers through the use of balance coils for the purpose of preventing susceptibility to short circuit conditions as will hereinafter he described in connection with Fi 3. I

it is necessary to neutralize the inductive effects arising from the flow of the currents in the portion of the railway system extending between the transformers 1'2 and 11.. As mentioned ahove. one-half of the propulsion current flows through the winding 18 of the transformer v12. An equally and oppositely directed current is. therefore. induced in the secondary winding 1?) of the tral'isformcr l2. The directioi'i of flow of this induced current is represented by the brokerrline arrow 46. locally closed circuit is. consequently. established in which flows an induced current that is equal to one-half of the propulsion current. This local circuit comprises the winding ll-r of the transformer 12. a section of the trolley conductor 1. the trolley pole ii. the train 40. a portion of the track circuit 2 and the impedance bond 16.

Similarly. one-half of the propulsion current flows through the winding 5 of the transformer 11. In consequence thereof. a current. the direction of How of which is represented by the dot-aml-dash arrows l7 and the value of which is equal to the second port-ion of the propulsion current. is induced in a local circuit which comprises the winding 13 of the transformer 11". a conductor l8. a portion of the trolley coi'iductor 1. the primary winding 36 of the series transformer 35, the trolley pole 42. the train 40. a section of the rail circuit 2. the inn 'iedan te bond 1 and the conductors ll and 15.

Since the indu ed urrent flowing through the winding 1 is equal and opposite to the induced current flowing in the winding 123".-

the saidv currents simultancmlsly traversing the trolley conductor 1 neutralize their inductive effects impressed upon the tcle phone comluctor 20. Again. the inductive. etl'ects arising from the propulsion current flowing along the trolley conductor 1 from the series transformer S to the trolley pole 42 are neutralized by the. inductive effects arising from the llow of the portion of the propulsion current: flowing along the section of the return feeder 4 that is intermediate the transformers 12 and 11.

Because, as previously assumed, the train 40 occupies a mid-position on the track section 3, the corresponding section of the trolley conductor l-over which the entire propulsion current flows subtends a length of the telephone circuit 20 that is equal to onehalf the length thereof subtended by the portion of the return feeder intermediate the transformers l2 and 11, over which flows one-half of the propulsion current.

If the inductive reactive-drops 'iu the transformers were not compensated for in accordance with the varying loads obtaining in the system. the inductive effects severally arising from the currents traversing the trolley conductor and the return feeder would not be cqualand opposite and. therefore. will not completely neutralize each other.

By automatically controlling the lcading currents supplied o the system by the condenser 21, the inductive reactive-drops in the transformer windi'n may be completely compensated for and. therefore. the ratio between the voltage impressed across the trolley conductor and the track circuit and the voltage impressed across the track circuit and the return feeder will be maintained constant. In this instance. the two aforesaid voltages are maintained equal and in exact phase opposition to each other.

While the synchronous condenser 21v assistsin completely neutralizing the inductive effects to which the telephone circuit 20 is subjected. it also serves to improve the power-factor of the system. thereby increasing its operating efficiency.

In Fi 3, the condenser 21 is connected to adjacent transformers 11 and 12 through balance coils 49 and 50. Since the balance coils are similar in construction. I will dc scribe only one of them in detail. The bal ance coil 49 comprises two windings 5'1. and 52 which are so disposed upon a magaetiz able core member as to simultaneously generate equal and oppositely directed ma {.1- netic fluxes. Corresponding terminals o the coils 51 and 52 are connected to a common conductor 54 that. in turn. is connected to one terminal of the synchronous condenser 21. The other terminals of the coils 51. and 52 are severally connected. respectively. to those windings of the transformers 11 and 12 that are inserted between the trolley eonductor 1 and the track circuit 2. In a si1nilar manner. the balance coil 50 connects the other terminal of the condenser 21. to the transformer windings inserted between the return feeder 4 and the track circuit 2. in this manner. the condenser 21 may furnish leading currents to the railway sections on both sides of the transformers 11 and 12.

The balance coils 49 and 50 are employed 26 is also controlled by means of a vibratingcontact-type regulator. The regulator and the attendant circuits are not shown in Fig. 3, since they may be identical with those shown in Fig. 2.

It will be observed that, by connecting the balance coils as shown in this figure, I have been able, not only to employ a low-potential synchronous condenser to compensate for the inductive drops in the high-potential transformer, but have also been able to so isolate the synchronous condenser that it is unaffected by short-circuit conditions existing in the aforementioned electric-railway system;

While I have shown and described, somewhat in detail, several embodiments of my invention, it will be understood by those skilled in the art that many modifications may be made therein without departing from the spirit and scope of the appended claims.

claim as my invention:

' V 1. An electrical railway circuit comprising a trolley conductor, a return feeder therefor, a track circuit, spaced transformers having their inducing and induced windings connected in series relationship between the trolley conductor and the feeder, whereby said railway circuit is sectionalized, means for connecting an intermediate point of said transformer windings to the track circuit, and means associated with said transformers for automatically compensating for the re active-drops obtaining in them under different load conditions, whereby the voltages impressed upon the system by said inducing and induced windings will be maintained at a constant ratio, said means being so connected to the transformer that they are substantially free from disturbance by short circuit conditions which occur in the system.

2. An electrical railway circuit comprising a trolley conductor, a return feeder therefor. a track circuit, spaced transformers having their inducing and induced windings connected in series relationship between the trolley conductor and the feeder whereby said railway circuit is ectionalized, means for interconnecting an intermediate point of said transformer windings to the track circuit, and means influencedby the load currents flowing in the system for automatically maintaining a constant ratio between the voltages impressed upon the system by the said inducing and induced windings, said means being connected to said transformers through balance coils.

3. An electrical railway circuit'comprising a trolley therefor, a track circuit, spaced transformers having their windings connected in series between the trolley conductor and the feeder whereby said railway circuit is sectionalized, the inducing and induced windings of said transformers bearing a mie-to-one voltage ratio to each other, and the inducing windings thereof being connected between the track circuit and the feeder and the induced windings being connected between the track circuit and the trolley conductor, and means for maintaining a fixed relation between the values of the voltages impressed upon the system by the said inducing and induced transformer windings, under all load conditions, said means being so connected to the transformer that they are substantially free from disturbance by short-circuit conditions which occur in the system.

4. An electrical railway circuit comprising a trolley conductor, a return feeder therefor, a track circuit, spaced transformers having their inducing and induced windings connected in series relationship between the trolley conductor and the feeder, means for interconnecting an intermediate point of said transformer windings to the track circuit, a synchronous condenser connected to the system, and balance coils connected between said condenser and the transformer system, the field excitation of said con denser being automatically controlled in accordance with the load conditions obtaining in the system whereby the inductive reactive-drops in said transformers may be compensated for.

5. An electric railway system comprising a trolley conductor, a return feeder therefor, a track circuit,a plurality of spaced series transformers for inductively interlinking the trolley conductor and the feeder, a transformer connected on each. side of said series transformers for intereoi'inecting said trolley conductor, said return feeder and said track 'circuit with one another, and means associated with some of said transformers that are connected in circuit on each side of said series transformers for automatically compensating for the reactive-drops obtaining in said transformers, in order that the values of the voltagesobtaining between the track circuit and the trolley conductor shall main tain a fixed relation to the values of the voltages obtaining between the track circuit and the return feeder, under all load conditions.

6. An electric railway system comprising a trolley conductor, a return feeder therefor, a track circuit. a plurality of spaced series transformers for inductively inter-linking the trolley conductor and the feeder. a transformer connected on each side of said series transformers for interconnecting said trolley conductor, said return feeder and said track circuit with one another, a synchronous conconductor, a return feeder denser, balance coils connected in circuit therewith for connecting the synchronous condenser to both the inducing and induced windings of the transformers connected. on both sides of said series transformers, and means for automatically varying; the field excitation of said synchronous condenser in order to compensate for the inductive reactive-drop obtaining in the transformer windings connected thereto, under all load. 10 conditions.

In testimony whereof, I have hereunto subscribed, my name this 28th day of Oct. 1916.

CHARLES LE 6-. FORTESCUE.

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