US1318946A - Electrical system - Google Patents

Description

F. E. WYNNE.

' ELECTRICAL svsnm. APPLICATION FILED H.213, l9l5- RENEWED FEB. 25. I919.

1,318,946. v Patented Oct. 14,1919.

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" 7AfionNEY UNITED STATES PATENT oEEIoE.

FRANCIS E. WYNNE, 0F EDGEWQOD PARK, PENNSYLVANIA, ASSIGNOR TO WEST- INGHOUSE ELECTRICAND MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA.

Specification of Letters Patent.

ELECTRICAL SYSTEM.

Patented Oct. 14, 1919.

Application filed January 23, 1915, Serial No. 3,929. Renewed February 25, 1919, Serial No. 279,182.

To all whom it may concern:

Be it known that I, FRANCIS E. WYNN a citizen of the United States, and a resident of Edgewood Park, in the county of Allegheny and State of Pennsylvanla, haye invented a new and useful Improvement in Electrical Systems, of which the following is a specification. Q

My invention relates to electrical systems,

and it has special reference .toflsystems of control, for alternatingcurrent railway electrifications of a certain type.

'One of the objects of my invention is to provide an improved system of the aboveindicated character which shall be adapted to prevent, automatically or otherwise, as desired, the total power absorbed by an alternating-current railway system from exceeding a certain specified maximum at any time, without, however, interfering undesirably with the operation of the several trains during the period of incipientoverload. I

A further object of my invention is to provide a system in which, by varying the frequency/and voltage of the output of a generator in a sub-station, the'power input thereto may be satisfactory and be efficiently controlled, on the one hand, and a railway system that is fed from the station and may have its power-demands desirably supplied at all times, on the other hand.

Another object of my invention is toprovide apparatus of the class under considera tion which shall efiiciently, conveniently and reliably perform the intended functions at a comparatively small expense.

It is sometimes desirable, or even necessary, particularly in a case where a railway system purchases its power from an outside power company, that a predetermined maximum consumption of power shallnever beexceeded, even under unusaally severe operating conditions. It is especially toward means for preventing such an objectionable occurrence that myinvenvention is directed; for, although, with an ideal distribution of trains, the power consmnption may be kept within the specified limit, it evident that suchan ideal condition cannot possibly be maintained for any length of time. a

In a certain railway electrification, let it lloe assumed that the general layout is as folows:

At various sub-stations along the railway line, three-phase cyclepower, supplied by an outside company is transformed, by means of suitable frequency-changing sets, to single-phase 25-cycle energy which, as is well known, is better. adapted for the propulsion of railway vehicles. Any suitable arrangement of power circuits and locomotives may be employed. 1 V

In a copending application of Benjamin G. Lamme and Francis H. Shepard, Serial No. 808,716, filed December 26, 1913, and assigned to the Westinghouse Electric &

Mannfacturing Company is shown a system of the type under consideration. The following theoretical discussion will serve to render my invention more clearly under stood.

The above-mentioned locomotives may operate on any frequency, within a given range, provided the voltage varies in proportion to the frequency. For example, if the frequency dropped from the assumed normal value of 25' cycles to 20 or 15 cycles, and if the voltage decreased in the same proportion, the locomotives would operate under practically the same tractive effort as before and with the same-current supplied to the motors, but the input tothe locomotive would be reduced practically in proportion to V the frequency and voltage. Consequently, in the event of an overload on the railroad system, if the frequency and voltage delivered by the sub-station are lowered, the railway load may be reduced also. In this way, the power consumption from a transmission circuit may be kept within a specified maximum, but the train operation is sacrificed. In other words, whereas the specified power consumption from the transmission circuit is not exceeded, the

overload current demanded by the trains in order to maintain desirable operatingcondltions is not suppl ed and the railway servie'esufiers in consequence.

However, if the output of the frequency changer can be reduced in smaller proportion than the decreases in frequency and voltage or can be maintained substantially constant during such decrease, the demanded overload current may be supplied to the railway system without exceeding the speci fied power consumption from the transmission line and with good train operation. For instance, if the output of the frequency changer can be held substantially constant, while the frequency and voltage are de creased 30%, then the current delivered to the locomotives may be increased approximately 30% and their tractive effort increased in proportion. Thus, with such a system, by varying the frequency but not varying the output in the same proportion, it becomes possible to haul heavier trains, or more of them, under overload conditions without exceeding the predetermined power input and, in addition, without sacrificing good train operation. \Vhereas a system of this type is especially adapted for use with locomotives embodying induction driving motors, it will be understood that the current regulation itself does not depend upon the use of such motors and other systems employing such locomotives, in part or not at all, may also secure a certain degree of benefit from the system.

One system shown and described in the above-identified co-pending application comprises a directcurrent motor that is mounted on the shaft of the frequencychanging set and a rotary converter connected between the secondary winding of the driving induction motor of the set and the direct-current motor. By varying the field strength of the D. C. motor, its armature voltage, as well as both the direct-current voltage and the dependent alternating-current voltage of the rotary converter may be varied, and thus the electro-motive force of the secondary winding of the induction motor may be changed. Moreover, if desired, automatic apparatus may be employed in combination with the above-mentioned system, whereby, when the input to the power station reaches a predetermined maximum value, the field of the directcurrent motor is regulated to decrease the induction motor speed and thus suitably reduce the frequency and voltage delivered by the generator, while keeping its output very nearly constant.

More specifically stated, it is an object of my invention to increase the efficiency of the system just recited, by providing preferably automatic means for short-circuiting the secondary winding of the driving induction motor and, consequently, the rotary converter, during such periods as the load current of the induction motor remains below a predetermined value. The losses that would otherwise occur in these periods in the converter are obviated, with a resulting increase in efficiency of operation of the regulating system. Consequently, the heating of the converter is reduced, or the size of the converter may be decreased without danger of overheating.

The single figure of the accompanying drawing is a diagrammatic view of an electrical system arranged and connected in accordance with my invention.

Referring to the drawing, thesystem here shown comprises a suitable three-phase transmission line of relatively high frequency having hase-conductors 1, 2 and 8; a railway or other circuit f to be supplied with converted energy; and a frequencyconverting set including a three-phase induction motor 7 that is suitably connected to the transmission line, either directly or through transformers, (not shown) and an alternating, current single-phase generator 8 for supplying the railway circuit 4., either directly or through transformers (not shown), with voltage of a suitably low frequency. A suitable direct-current motor 9, preferably having a shunt field-magnet winding 10, is mounted on the shaft of the set and is adapted for variable excitation, the field winding 10 having a variable resistor 11 in circuit therewith.

A rotary converter 12, of any suitable type, has its alternating-current end connected to the secondary winding of the induction motor 7 and its direct-current end connected across the armature of the motor 9.

In connection with the field resistor 11, an electromagnetic device 13 is preferably employed to automatically regulate the field current, as hereinafter described. The device shown is intended to be merely illustrative of an idea, and it will be understood that other automatic apparatus for accomplishing the purpose may be employed, if desired. The device 13 may comprise a. solenoid 14- that is connected in a main line conductor and the core 15 of which has one end operatively attached to the movable member of the resistor 11; and a dash pot 16 or other suitable member may or may not be secured to the other end for retarding the removal of resistance from the field circuit.

The field winding 10 of the auxiliary motor 9 is adapted to be separately excited through the resistor 11 by a suitable exciter machine 17, which may be driven from the shaft of the frequency-converting set by a belt connection 17 or in any other suitable manner. A switching device 18 has its ac tuating coil 19 connected in circuit with the motor-field winding 10 and is disposed, when occupying its lower or biased position. to short-circuit the secondary winding of the induction motor 7 and, consequently, the alternating-current sidev of the rotary converter 12, through the medium of a plurality of conductors 20. A power or wattage relay or switching device 21 is normally adapted to open the circuit of the motor-field winding 10 and is adapted to close at some convenient main input value, say 10% below the actuating current value of the electromagnetic device 13. The core 22 of the relay is adapted to be actuated upon by a current coil 23 that is connected in one of the transmission line conductors, and to besimultaneously influenced by avoltage coil 24 that is connected across one phase of the line. The relay 21 is thus adapted to be actuatedin ac cordance with the energy input to the induction motor; but, inasmuch as the impressed line voltage will remain substantially constant, the relay will be actuated substantially in accordance with the current input to the induction motor.

As hereinafter more fully described, the

secondary. winding of the inducton m0tor7 and, consequently, the alternating-current side of the rotary converter 12 are adapted to be short-circuited, under predetermined con-.

ditions. The corresponding operation. of the converter may be set forth as follows: The converter is supplied with a relatively lowvoltage, low-frequency current from the secondary winding referred to, andv thus runs at a relatively. low speed" and with small energy consumption. Assuming that the converter is at rest with the short-circuiting switch 18 occupying the closed position shown in the drawing, when the sub-station energy input increases with relative rapidity,

by reason of several trains starting at once,

for example, the wattage relay 21 is actuated prior to the electromagnetic device 13 reason of the above-mentioned lower setting of the relay, to close the circuit of the auxiliary motor field winding 10, whereupon the actuating coil 19 of the switch 18 is energized and the short-circuit hereinbefore re ferred to is removed. The converter 12 is thus started into operation and, if .the increase of energy input continues, the hereinafter described actuation of the device 13 then takes place. Vhen thefenersrv input again decreases below the setting of relay 21, the short-circuit again obtains, and the converter comes to a standstill. It will be un derstood that the design of partsis such that the rotary converter will always be operating when necessary, but will run just as little as possible, in order to. obtain the greatest efficiency of the system as a whole.

Assuming'the apparatus tobe connected, as shown, the operation of the entire system be described as follows: 'During the prevalence of normal operating conditions on the railway or other system, the driving,

mal Speed, and the direct-current motor 9 and the rotary converter 12 will be inoperative, since the switch 18 occupies its shortcircuiting position. However, upon the occurrence of an incipient overload, that is, as

consequently, the movable member of the resistor 11 is operated against the action of the dash-pot 16, if one is employed, to exclude resistance from the field circuit of the direct-current motor 9, the said movable member tending to take the position shown in dotted lines. a The field flux is thus strengthened and the armature voltage'increased, whereby the direct-current voltage and depending alternating-current voltage of thejrotary converter. are increased proportionately to efi'ect acceleration of the con verter and the voltage of the secondary winding of the induction motor 7 is, consequently, raised. As a result, the speed of the induction motor and the associated alternating.- current generator is reduced, thus also reducing the frequency and voltage produced by thegenerator. The final result is that the power outputof the frequency-changing set 3 is maintained substantially constant, but a much increased current may 'be delivered by the generator, as already explained. In this way, the abnormal current load is supplied without exceeding the specified maximum power consumption.

I do'not wish to be restricted to the specific arrangement of parts or circuit connections herein set forth, but desire that only such limitations shall be imposed as are indicated in the appended claims.

I claim as my invention:

1. In an electrical system, the combination with adriving dynamo-electric machine and a second machine driven thereby, of means for,obtainingyariations of the current output of said driven machine that are 3. In an electrical syscenrtlm combination. with adriving ,dyna no electric machine tau and a second machine driven thereby, of means for automatically obtaining a rela-' tively large variation of the current output of said driven machine with a relatively small variation of current input to said driving machine, and means for automatically rendering said first means inoperative under predetermined load conditions.

4. In an electrical system, the combination with a driving dynamo-electric machine and a second machine driven thereby, of

tor influenced in accordance with load conditions of said induction motor, a rotary converter having alternating-current connections to the secondary winding of said induction motor and direct-current connections to said auxiliary motor, and switching means governed substantially in accordance with said load conditions for effecting a short-circuit of said secondary winding under predetermined relatively low-load conditions.

6. In an electrical system, the combination with an induction motor, and an alternating-current generator driven thereby, of an auxiliary direct-current motor having its armature rotatable with said machine, and having a speed-controlling field winding, a variable resistor connected in circuit with said armature, means controlled by the current input to said induction motor for automatically varying said resistor to correspondingly vary the speed of said induction motor, a rotary converter having alternating-current connections to the secondary winding of said induction motor and directcurrent connections to the armature of said auxiliary motor, switching means having an actuating coil in the circuit of said field winding for shortcircuiting said secondary winding, and other switching means controlled by the energy input to said induction motor for closing 01' opening the circuit of said auxiliary motor field winding according as said energy input is respectively above or below a predetermined value.

7. In an electrical system, the combina tion with a driving dynamo-electric machine and a second machine driven thereby, of

means responsive to load conditions for o'btaining a disporportional variation of the current input to the dynamo-electric ma-' chine'to the current output of said second machine, and means comprising a power relay for rendering said first named means inoperative under predetermined load conditions.

8. In an electrical system, the combination with a driving dynamo-electric machine and a second machine driven thereby, of means responsive to load conditions for obtaining a disproportional variation of the current input to the dynamo-electric machine to the current output of said second machine, and relay means for automatically rendering said first means inoperative under predetermined load conditions.

9. In an electrical system, the combination with a driving dynamo-electric machine and a second machine driven thereby, of means for obtaining a disproportional ratio of the current input to the dynamo-electric machine to the current output of said second machine, and an electrically controlled means for automatically rendering said first means inoperative under predetermined load conditions.

10. In an electrical system, the combination with a supply circuit, a dynamo-electric machine, and a second alternating-current dynamo-electric machine driven thereby, of electro-responsive means dependent upon the supply circuit conditions for varying the frequency of said second machine to permit of variation in the output thereof, and means for rendering said electro-responsive means inoperative under predetermined load conditions.

11. In an electrical system, the combination with a supply circuit, a driving induction motor fed therefrom, and an alternating-current generator driven thereby, of electro-responsive means connected to said machines and dependent on predetermined supply-circuit conditions for varying the frequency of said machine to permit a variation in the output thereof, and means for automatically rendering said electro-responsive means inoperative under predetermined load conditions.

12. In an electrical system, the combination with a supply circuit, a receiving circuit, a driving induction motor, a plurality of conductors for connecting said motor to said supply circuit and a driven alternating-current generator connected to said receiving circuit, of electro-responsive means embodying an actuating coil series-connected in one of said conductors, said means being adapted, under predetermined current conditions, to automatically permit an increased current in said receiving circuit While maintaining said current conditions substantially constant, and means for automatically reir dering said electro-responsive means inoperative under predetermined load conditions.

'13. In-an electrical system, the combination with a supply circuit and a receiving circuit, of a motor-generator set for c0nnecting said circuits, electrical means connected to said machines and dependent upon the attainment of a predetermined power consumption in said supply circuit for varying the current of the driven machine and simultaneously maintaining said power consumption substantially constant,

10 and means for rendering said first named FRANCIS E. WYNNE.

Witnesses:

L. W. LINK, B. B. HINES.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents. Wuhington, D. 0.

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