US1303281A - Non-inductive interference system - Google Patents

Description

C. LE G. FOBTESCUE.

NON-INDUCTIVE INTERFERENCE SYSTEM. APPLICATION min SEPT. 28. 1911.

Patented May13, 1919..

WITNESSES:

4 INVENTOR liar/wlefi/fcva/c ATTORNEY UNITED STATES PATENT OFFICE.

CHARLES LE G. FORTESCUE, 0F PITTSBURGH, PENNSYLVANIA, ASSIGNOR TO WEST- INGHOUSE ELECTRIC AND MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA.

NON-INDUCTIVE INTERFERENCE SYSTEM.

Specification of Letters Patent.

Patented May 13, 1919.

To all whom it may concern:

Be it known that I, CHARLES LE G. Fox- 'rnsoon, a subject of the King of Great Britain, and a resident of Pittsburgh, in the county of Allegheny and State of Pennsylvania, have invented a new and useful Improvement in Non-Inductive Interference Systems, of which the following is a specification.

My invention relates to electrical distributing systems and it has special relation to alternating-current systems in which novel means are employed for controlling the power-factors of the load currents obtainin therein.

ore particularly, my invention relates to distributing systems that are supplied with electrical energy from a plurality of spaced sub-stations and upon which variable loads obtain at points intermediate the sub-stations. The currents occasioned by these variable loads may possibly change in value,

as well as possess varying power factors.

My invention, in the present instance, is shown applied to an alternatingcurrent railway system that is paralleled for longer or shorter distances by an intelligencetransmission circuit, such as a telephone or telegraph circuit. As a consequence of constructing a railway system in accordance with my invention, inductive disturbances that are usually prevalent in circuits adjacent to an alternating-current railway system fed from a plurality of spaced sub-sta tions that severally deliverpower currents in both directions, may be suificiently minimized to insure against the railway system interfering, to any appreciable degree, with the normal operation of the adjacent cir-- cuits.

Another advantage accruing from the use of my invention is that the power-factor of a power circuit fed from a power-transmission system may be controlled independently of the power-transmission system and maintained at any predetermined value, irrespective of the character of the load obtaining in the power circuit.

In alternating-current railway systems comprising two or more spaced sub-stations that furnish electrical energy to a plurality of loads fed from a common trolley co'n ductor, it is difiicult to protect an adjacent telephone circuit against inductive disturbances because the currents supplied to the loads are continually varying in amount, as well as in power-factor. It has been pro posed to maintain the voltages impressed upon the railway circuit by the several sub stations substantially equal to one another in value. Under ordinary circumstances, this would insure the production of slight disturbing influences only, but, by reason of the different power-factors of the currents simultaneously delivered from the power stations, the maintaining constant of the impressed voltages is not a sufficient precaution to minimize the inductive disturbances to a satisfactory degree. In addition, it is necessary to adjust thephases of the currents flowing in the railway circuit in opposite directions to an intermediate load point in order that the resulting inductive disturbances impressed upon the adjacent circuit may be substantially minimized. If the oppositely directed currents are not maintained substantially in phase opposition to each other, the resultant inductive effects may be sufficient to seriously interfere with the satisfactory operation of any circuit subject to the inductive disturbances that arise from the flow of power currents in the railway system. It will be noted, therefore, that the value of the voltages impressed upon the power circuit should be controlled, as well as the bases of the power currents, in order to su ciently minimize the inductive disturbances that otherwise would be impressed upon an adjacent circuit. T0 the accomplishment of this result and other objects to be hereinafter disclosed, the present invention is directed.

For a better understanding of the nature and scope of my invention, reference may be had to the following description and the accompanying drawing,- in which Figurel is adiagrammatic representation of a railway system embodying a form of my invention, and Fig. 2 is a vectorial diagram illustrating the mode of operation of the system shown in Fig. 1.

Referring to 1, a railway circuit, constituting a trolley conductor 1 and a track 2,15 furnished with power from a plurality of spaced sub-stations, such as. are indicated at 3 and 4. The substations 3 and 4 are shown as supplying load currentsto an intermediate load vehicle 5. It is to be understood, of course, that eachfsubstation may furnish power-currents to loads intermediate the immediately adjacent substations, as Well as loads of other characteristics at more remote points on the railway system. 'It is evident, also, that each substation may deliver power currents of different values and characteristics in both directions.

1 Air intelligence-transmission conductor 6 is disposed adjacent to'the trolley conductor 1 and the'track 2, and is, therefore, under the inductive influences arising from the currents flowing in the railway circuit. For

the purpose of illustration only, the telephone conductor 6 may be considered as being uniformly spaced from the trolley conductor 1 throughout its entire length.

It will'be understood,'however, that my in- "ing connected through conductors 29:5111d 30,

vention isefifective in minimizing inductive 1 disturbances whether or not the telephone conductor 6 is spaced uniformly frointhe trolley-conductor 1 throughout its entire length.

The substations 3 and 4 are supplied with power delivered over phase 7 of a polyphase transmission circuit 8. transmission circuit 8 as a two-phase circuit but my invention is not limited to a transmission circuit of this character, since any polyphase circuit may be transformed into a'two-phase circuit wherein two electromotive forces displaced 90 in phase-from "of :the other substations. *describe my invention asapplied to the subeach otherimay be obtained by many wellknown methods, such, for instance, as a T-transformer connection.

It is to be presumed that the sub-stations 3 and 4 are spaced considerable distances from! each other, such distance depending I have shown the respectively, to phase 7 of the transmission circuit 8. A rotatable contact-making ele- -ment comprises two insulated conducting :arms'32 and. 33 that are-adapted to bridge, respectively, the'conducting segments 23 and 24rand accessible'taps 8% and 35 of the resistor 26. The adjustable contact-making arm is rotated by means of a shaft 36 of a motor 38. Themotor 38 is connected through a reversin switch 89 of a well-known t )e :andconductors Ortoithe phase 7.

v I-tzwill beobserved that the field winding 22 of the booster generator 14: is excited by an:ialternatingrcurrent. delivered from the same phase 7 of the supply circuit as the powen currents furnished to the railway sys :tem. As isrwell known, anv alternatingcurrent commutator-type generator generates an ielectromotiveforce that is in phase with the-current flowing in its exciting winding.

There-forge the voltage generated by the -:booster generator 14- may be in phase with the voltage of phase 7 An exciting winding 41 of the booster generator '15 is likewise connected incircuit ';-W1tl1 an achustablerheostat 25 Diametri- .cally opposite points'27 and 28 of this upon the particular features embodied in,

and the character of, the railway system. Again the substations 3 and 4 are representative only ofthe many substations that may furnish power to: the system, each sub- 1 station being substantially a duplicate, so

faras the electrical; equipment is concerned, Therefore, I- will stations 3 and 4 only, it being understood thatsthe operation of the electricalequip- 'ment of-the remaining, substations is similar.

The substation 3 comprises a power transformer 9,1 the primary-winding l0 ofwhich is connected to thephase 7. A'secondary winding 11 has its-terminals 12 connected directly to thertrolleyaconductor 1. and its terminal 13 v connected, through the armature circuits of booster generators' lei and 15,

a=-primary' winding 16 of a currenttransformer-Hand a conductor 18, tethe railway. track 2. ,.Tliezboostergenerators 14;.and

'I'hBOStELlZ' are, however, connected through leads 29 and80, respectively, to the phase 31. A-i'eversing switch 39 controls the direction of rotation of amotor 38 which op- .erates the contact-making arms of the adjustable rheostat 25*.

Since the booster generator 15 is excited by an alternating-current delivered from the phase 81 of thetwo-phasesupply circuit 8, and the booster generator 14 is supplied with an exciting current from the phase 7 of the two-gphase supplycircuit 8, the electromotive forces generated in the respective armature .nindings of the said two booster generators will be displaced 90 in phase from each -.other.

junction, serve to adjust the resultant elec- These electromotive. forces, in contromotive force impressed upon the railway circuit at the substation 3.

,The direction of rotation of the motor 88 is; controlled by means of a contact-making voltmeter 44: which comprises an electromag- ..-net4 5..-having zit-movable core 46 that is other.

linked, at its upperend, to a pivoted arm 47. A spring 18 is so designed as to aid in balancing the weight of the core member i6 when a voltage of predetermined value is impressed. upon a secondary winding 49 of a voltage transformer 50, the primary winding 51 of which is connected across the trolley conductor 1 and the track 2. The pivoted arm 4:? is provided with a contact member which may engage the one or the other of stationary contact members 53 and 54. When an abnormally high current is demanded of the substation 3, the voltage impressed. upon the electromagnetwifi momentarily decreases, thereby-permitting the pivoted arm 17 to effect engagement between the contact members 53 and 52. Likewise, when the voltage impressed upon the railway circuit exceeds the predetermined value, engagement is effected between contact members 52 and 54:. The circuits established through the contact points 53 and 54 control the excitation of electromagnets 53 and 54*, respectively, of the reversing switch 39. In this manner, the direction of rotation, as well as the excitation of the motor 38, is controlled in accordance with the value of the voltage impressed upon the railway circuit by the substation 3.

A modified form of a power-factor relay, shown at 55, controls the excitation and direction of rotation of the motor 38 in accordance with the phase displacement between the current furnished to the moving load 5 from the substation 3 and that furnished thereto from the substation e. The power-factor relay 55 comprises a winding which is supplied with current from a secondary winding 57 of the series transformer 17, the primary winding 16 of which, as hereinbefore stated, is connected in series circuit with the secondary winding 11 of the power transformer 9. The coil 56 is disposed upon a core 57 of magnetizable material. Fine-wire coils 58 and 59, mounted upon a common rotatable axis in the field created by the winding 56 and the core' member 57, are subject to the restraining influence offered by a tensional element or coiled spring 60. The two coils 58 and 59 are connected in different branches of a circuit connected to a secondary winding 61 of a current transformer 62 which is 10- rated in the substation 4. A primary winding 61 of the transformer 62 is connected in series circuit with one terminal 63 of a power-transformer 64 that is placed in the substation 4, The secondary winding 61 is connected to the coils 58 and 59 of the relay 55, placed in the substation 3, by means of pilot conductors 65 that serve to interconnect the spaced substations with each A. non-inductive element 66 and an inductive element 67 are connected, respectively, in circuit with the coils 59 and 58 in order to obtain an operative quadraturephase relationship between the currents flowing in the said two coils. A contactmaking pointer 68, mounted upon the common axis of the coils 58 and 59, operates to connect a conducting segment 69 to either a conducting segment 70 or a conducting segment 71, depending upon the nature of the interaction between the coil 56 and the conjoint action of the coils 58 and 59. \Vhen the contact member 68 engages the one or the other of the contact segments 70 and 71, the reversing switch 39 will be actuated, as hereinbefore explained in connection with the reversing switch 39, to properly excite the motor 38 Referring to the operation of the powerfactor relay 55, the coil 56 is traversed by a current, the phase of which always bears a definite relation to that of the power current supplied by the substation 3 to the railway circuit. The coils 58' and 59 are travcrsed by currents having displaced phases, but which also hear a definite phase relation to the power current furnished by the substation 4 to the railway circuit. As a result, the movable system comprising the coils 58 and 59 will take a position depending upon the phase displacement between the oppositely directed currents supplied to the intermediate load 5 from the substations 3 and i. The power-factor relay 55 is so adjusted that only when the power currents supplied from the substations 3 and 1 are in substantial phase opposition, the pointer 68 will occupy a zero position intermediate the conducting segments 70 and 71. When the phase relationship between said power currents depart from a substantial phase opposition, the contact-making pointer 68 will engage the one or the other of the conducting segments 70 and 71 and, in this manner, control the direction of rotation of the motor 38*.

It will be appreciated that the inductive disturbances impressed upon the adjacent telephone circuit 6 must be substantially neutralized in order to permit satisfactory operation of the telephone circuit and, to this end, the elect-romotive forces induced in the telephone conductor 6, by reason of the load currents flowing in opposite directions from the substations 3 and i to the intermediate load 5, must be substantially neutralized. Since .the electromotive forces induced in the telephone conductor 6 are proportional to the ampere-miles on each side of the moving vehicle 5, it is necessary that the oppositely directed load currents traversing the trolley conductor 1 shall be inversely proportional to the length of the circuits intervening between the said substations and the load 5. To accomplish this, it is necessary that the voltages impressed upon the railway circuit by the substations be maintained substantially constant and equal in ,value, irrespective of the positlon ofzthe moving vehicle and the power requirements thereof. Each substation, therefore, is supplied with the contact-making voltmeter 4-4 which, as will be hereinafter fullyexplained, is instrumental in maintaining'the voltages constant that are impressed by the substations upon the trolley conductor.

In addition to maintaining the voltages constant, irrespective of the position of the moving vehicle 5 or other power demands from the substations 3 and 4, the oppositely directed currents flowing to the moving vehicle 5 must be substantially opposed in -phase relationship in order to effectively neutrahze the inductive electromotive forces inthe conductor 6. To this end, the substations are supplied with the contact-making power-factor relays 55 which insure that the currents flowing from the immediately ad- ...j acent substations that are connected through the pilot conductors 65 shall be maintained in substantial phase opposition to each other, under all load conditions.

Referring again to the function of the booster generators 14 and 15, in conjunction with their auxiliary control apparatus, it is apparent that the booster generator 14 .may generate an electromotive force that is either substantially in phase-with, or in direct phase opposition to, the electromotive force generated in the secondary winding 11 of the power transformer 9, This is apparent since the associated excited wind- -ing 22 of the booster generator 14 is impressed with the same voltage that excites the primary winding 10 of the power trans- =former 9.

By means of the adjustable rheostat 25, the direction of flow, as well as the value of, current through the exciting winding 22, is controlled. The booster generator 15, by reason of its exciting winding 41 being supplied with current from the phase 31 of the two-phase supply circuit, may generate electromotive forces that are substantially at right angles to those generated by the booster alternator 14. In a similar fashion, the adjustable rheostat 25 controls the direction of flow, as well as the value of the current traversing the exciting winding 41.

It is, therefore, obvious that the booster alternators 14 and 15 are capable of supplying component electromotive forces that are displaced 90 from each other and that, by-

adjusting the values of these generated electromotive forces,'the value of the resultant electromotive force, that may be combined with the electromotive force generated in :the

secondary winding 11 of the power transformer 9, may be controlled. As a conse.

'quence thereof, the voltage impressed upon therailway'circuit may be the resultant of three component voltages, namely, that of the secondary winding 11 of the power transformer 9, that of the booster generator 14 and that of the booster generator 15.

Reference may now be had to Fig. 2, in

which a vector OA may represent, in length and position, the value and phase of the voltage, as well as the current that it is desired for one of the substations to-respectively impress upon, and to supply to, the trolley conductor 1. Assume, for instance, that a vector OB represents, in value and phase, the voltage which may be momentarilyimpressed by this substation by vreason of the load distribution upon the railway circuit. In order that the voltage vector OB may coincide with the voltage vector OA, a voltage vector BA is vectorially subtracted from theformer. The vector BA, in turn, comprises two components BC and CA, the vector BO being dependent upon the power factor or phase position of the vector OB. The component vector CA,

which is proportional to theexcess, value of the vector OB, may be considered as being generated by the booster generator 14, and the voltage componentvector BC, which is proportional to the phase displacement of the vector OB relative to the vector OA, may be considered as being generated by the booster alternator 15. Since the booster alternators 14 and 15 are mounted upon a common shaft and develop electromotive forces of the same frequency, the vector OB is'so modified as to coincide, in phase and value, with the vector OA.

The same reasoning may be applied to a vector OD which is substantially smaller in length than the vector OA, as well as being displaced in phase therefrom. lVhen this circumstance obtains, however, the booster alternators 14 and 15 will respectively generate voltages, the directions of which are reversed with reference to the voltages generated by them in the case mentioned above.

While the phase 7 of the two-phase supply circuit 8 is shown as furnishing allthe power currents to the railway system, it will be understood that it is usually preferable that the several phases of the polyphase distributing circuit be maintained in Teal- 1130 anced condition. This may be obtained by properly distributing the load circuits in order to equalize the loads impressed upon the separate phases or by supplying the polyphase circuit with a phase balancer of any usual type, by means of which the loads of the several phases may be equalized.

While I have shown one embodiment of my invention, it will be understood that many modifications may be made therein without departing from the spirit and scope of the appended claims.

I claim as my invention:

1. In an alternating-current distributing system, the combination with a single-phase alternating-current power circuit, of a plurality of spaced power units for furnishing energy to said power circuit translating devices adapted to draw energy from variable points in said power circuit between said power-unit connections thereto, single-phase commutator-type generators connected in series with said power circuit and severally generating electromotive forces that are displaced 90 in phase from each other, and means for independently varying the electromotive forces of said commutator-type generators in order that the voltage impressed upon said power circuit may be maintained at a predetermined value irrespective of the position of said translating devices between said power-supply units.

2. In an alternating-current distributing system, the combination with a single-phase alternating-current power circuit, of a plurality of spaced power units for furnishing energy to said power circuit, translating devices adapted to draw energy from variable points in said power circuit between said power-unit connections thereto, single-phase commutator-type generators connected in series with said power circuit and severally generating electromotive forces that are displaced 90 in phase from each other, means comprising an adjustable rheostat for independently controlling the direction and amount of current flow through the exciting windings of said generators, and relay mechanism so adjusted that said rheostat is operative only when the power currents supplied by adjacent power stations depart from substantial phase opposition, whereby the voltage impressed upon said power circuit may be maintained at a predetermined value irrespective of the position of said translating device between said power-supply units.

3. In an alternating-current distributing system, the combination with a single-phase alternating-current power circuit,'of a plurality of spaced power units for furnishing energy to said power circuit, translating devices adapted to draw energy from variable points in said power circuit between said power-unit connections thereto, singlephase commutator-type generators connected in series with said power circuit and severally generating electromotive forces that are displaced 90 in phase from each other, means comprising an adjustable rheostat for independently controlling the direction and amount of current flow through the exciting windings of said generators, and relay mechanism associating said power circuit and said rheostat whereby said rheostat is adjusted in one direction or the other as dictated by the departure of the currents furnished by adjacent power stations from substantial phase opposition, in one direct-ion or the other, whereby the voltage impressed upon said power circuit may be maintained at a predetermined value irrespective of the position of said translating devices between said power-supply units.

In testimony whereof I have hereunto sub szcribed my name this 10th day of Sept. 191

CHARLES LE G. FORTESCUE.

Copies 01 this patent may be'obtsined for flve cents each, by addressing the Commissioner of Patents,

Washington, D. 0.

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