US1504621A - Electrical system of distribution - Google Patents

Description

HELLMUND ELECTRICAL SYSTEM OF DISTRIBUTION f mmm@ Patented ug. 12, 1924.

UNITED `SVIHAUIIEIS PATENT OFFICE.

RUDOLF HELLMUND, GF SWISSVALE, FENSYLVANIA, ASSIGNOR TO WESTING- HOUSE ELECTRIC & I'ANUFAGTURING COliPANY, A CORPORATION OF PENNSYL- VANIA.

ELECTRICAL SYSTEM OF DISTRIBUTION.

Application filed a'arch 31, 1913.

To @ZZ/whom z'z may concern.'

' Be itknown that LRUDOLF E. HELLMUND, a citizen of Germany, and a resident of Swissvale, in the county of Allegheny and State of Pennsylvania, have invented a new and useful Improvement in Electrical Systems o'fDistribution, of which the following specification is a continuation in part kof application Serial No, 12,068, filed March 11, 1915, patented April 15, 1919, No. 1,300,388, and also a continuation in part of application Serial No. 178,548, filed July 5, 1917.

"My invention relates to electrical systems, andit has special relation to systems of control foralternating-current railway electrifications. i One of the objects of my invention is to provide a system of the above-indicated 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 that are in service during the period of incipient overload.

A further obgl ect of my invention is to provide a system in which, by varying the fre- `quency of the output of a generator in a sub-Station, the power input thereto may be satisfactory and may be efciently controlled, on the one hand, and a railway system that is fed from the station -may have its power demands desirably supplied at all times, on the other hand.

Another object of my invention is to provide apparatus of the class under consideration which shall efficiently, conveniently and reliably perform the intended functions at a comparatively small expense.

1t is somtimes desirable, or even necessary,

`particularly in a case where a railway system purchases its power vfrom an outside power company, that a predetermined maximum consumption of power shall never be exceeded, even under unusually severe operating conditions. It is especially toward means for preventing such an objectionable occurrence that my invention is directed; for, although, with an ideal distribution of trains, the power consumption may be kept within .the specified limit, it is evident that ySerial No. 286,434.

such an ideal condition cannot possibly be maintained for anyV length of time. Y

VIn a certain railway electriication, let it be assumed that the generallayout is as follows:

At various sub-stations along the railway line, three-phase (S0-cycle power, supplied by an outside company, is transformed, by means of suitableV frequency-changing sets, to single-phase 2li-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.

In orderto meet the .imposed condition of no excessive draft of power from the 60- cycle transmission mains, I have devised a relatively simple system `for performing the desired functions inexpensively, effectively and reliably. The following theoretical discussion will serve to render my invention more clearly understood.

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 Yshould drop from the assumed normal value of 25 cycles to 9.0 or 15 cycles, and if the volts should decrease in the same proportion, the locomotive would operate under practically the same tractive eifort as before and with the same current supplied to the motors, but the input to the locomotive would be reduced practically in proporation to the frequency and voltage. Consequently, in the event of an overload on the railway system, if the frequency delivered by the substation should be lowered, the railway load might be reduced also. In this way, the power consumption from a transmission circuit might be kept within a specified maximum, but the train operation would be sacrificed. In other words, whereas the specified power consumption from the transmission circuit would not be exceeded, the overload current demanded by the trains in order to maintain desirable operating` conditions would not be supplied and the railway service would suffer in consequence.

However, if the output of the frequency changer can be reduced in smaller proportion than the decrease in frequency and voltage or can be maintained substantially constant during such decrease, then the demanded overload current may be supplied to the railway system without exceeding the specified 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 decreased 30%, then the current delivered to the locomotives and their tractive effort can be increased approximately 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. Whereas, 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.

With regard to the broader features involved in the attainment of the above objects and in certain apparatus used, this application is a continuation in part of my copending application, Serial No. 12,068, which has matured intof Patent No. 1,300,388, hereinbefore mentioned.

Again it may, at times, be desirable to feed power to a singe-phase system from a main generator and to use a generator of the induction-type for such purpose. Under such conditions, I find that there are undesirable currents of higher frequency set up by reason of the tendency of the single-phase system to more or less disturb the true rotating field in the polyphase generator winding which carries the exciting currents. I find also that such undesirable currents may be present in the primary system from which the power for the single-phase system is drawn.

Another object of my invention, therefore, is to provide means in connection with a system as above described which shall be effective in eradicating the undesirable currents from the system, as a whole, and especially in preventing such undesirable currents from flowing into the machine, the frequency of which is varied in order to effect a frequency change in the currents furnished by the main generator to the single-phase supply system.

I`he specific form of eradicating means which I may employ in this application is shown in my co-pending application, Serial No. 266,749, tiled December 14, 1918, and Serial No.` 266,750, filed December 14, 1918, wherein are shown and claimed machines of the character described.

Inasmuch as the broader features of this application are included in the disclosure shown in my copending application which resuited in the above-mentioned Patent, No. 1,300,388, this present application is a continuation, in part thereof, as to said broader features, although different specific embodiments or improvements of the generic invention are separately claimed in the two applications.

In the accompanying drawing, the single figure is a diagrammatic view of a complete system of control embodying my invention.

Referring now to the drawing, the system shown comprises a 3-phase supply circuit 1; an induction machine 2, comprising a primary member 3 and a secondary member 4; a second induction machine 5 comprising generating winding 6, and an exciting winding 7. The secondary winding 4 is connected in cascade relationship with the winding 6 of the machine 5, and the singleephase consumption system 40 is connected intermediate the two windings 4 and 6. I find that such connection is, under some circumstances, instrumental in promoting the eliiciency of a system of the character described and permits the use of smaller units for the reason that energy is transferred partly as mechanical energy and partly as electrical energy, as pointed out in my (zo-pending application, Serial No. 178,548, filed July 5, 1917.

A machine 27 of the frequency-changer type comprises an armature member 28 pro vided with slip rings 29 at one end and a commutator cylinder 30 and brushes 31 at the other end. A field winding 32 is also provided on the machine 27 and is used for purposes of speed regulation, as will behereinafter described.

Energy for the operation of the machine 27 is derived from the source of supply 1, through the medium of transformer windings 33, the secondary turns of which may be varied by the movement of contacts 34 in accordance with certain predetermined conditions which will hereinafter be described. The contacts 34 are rigidly attached to an insulating member 35 which is actuated by a movable core member 36 surrounded by a coil 37. The stator field winding circuit 32 of the machine 27 is energized in shuntrelationship from the brushes 31-31, through the medium of transformer windings 46. Taps 3.9-39 are rigidly attached to the in sulating member 14 and are adapted to be noved along the transformer elements 46 by the actuation of the insulating member 14 by the movable core member 15 and the coil 16 surrounding the core member. Leads 22, 23 and 24 connect the brushes 31 to equidistant points in the exciting winding 7 of the main generator 5.

It will be observed in this connection,

however, that the generating winding 6 is supplying a single-phase system 40-40 and that, therefore, due vto the action of the single-phase currents and the polyphase conneotions in the generator 5, certain undesirable `currents will tend to pass from the exciting winding 7 of the main generator into and through the machine 27, and thus ultimately reach the polyphase source of supply 1.

In order to prevent these undesirable currents from iiowing into the machine 27, I provide an auxiliary eradicating machine 41 `functioning in the manner pointed out in the afore-mentioned co-pending applications. The machine 41 comprises a primary or stator member 42 and a secondary or rotor member 43, the rotor member being provided with a direct-currenteXcit'ed winding 44. The machine 41 is connected between the brushes 31 and the equi-distant tap points of the exciting winding 7 and, if operated at a speed corresponding to the synchronous speed of the frequency of the currents which are furnished by the machine 27 to the'exciter winding, will constitute a relative-ly high impedance for such currents and will provide a path of very low impedance for currents of any other Jfrequency which may flow along Vthe leads 22, 23 and 24.

rllhe insulating member 35 is actuated to Vary the voltage which is impressed upon Ythe frequency changer 27, it being necessary to maintain a certain well defined ratio between the frequency of the currents in the single-phase system 40-40 and the voltage which is impressed upon the machine 27. I have shown, therefore, the insulating member 35 which is actuated in accordance with the frequency of the currents flowing in the mains 40'-40, and a highly inductive device connected in series relationship in the control circuit by means of which energy is supplied to the coil 37.

lllie'n'ianner in which a relay device having a highly inductive coil in circuit functions to maintain a predetermined ratio of frequency to voltage is more specifically pointed out and claimed in my co-pending application, Serial No. 281,447, filed March 4, 1919, and will, therefore, be shown here in purely diagrammatic form and in no way specifically enlarged upon.

Again, assuming that the machines are operating in a normal manner and that the switching device 34 is in normal position, the operation of the system is as follows: If the energy input into the machine 2 increases beyond a predetermined value, the solenoid 15 and, consequently, the taps 39 are moved in such direction that the resist ance of the tieldwinding circuit 82 is adjusted in such direction that the frequency of the current derived from the brushes, 31

and, consequently, the frequency of the power fed to the single-phase system 40-40 is decreased. T he frequency of the currents in the system 4.0410 having decreased, the reiay which operates the solenoid 36 will function in such direction that the voltage appiied to the machine 27 wili be so aduiusted that the predetermined ratio of voltage to frequency will be maintained. Moreover, the machine 4i will further increase the efficiency of the system, by making it possible for the system to be used in connection with a single-phase consumption source without the probability of undesirabie harmonic currents creeping back into the polypliase source 1.

The system herein shown, with the exception of the eradicator machine 41 and the slip rings 29 of the commutator machine 27, is shown and described in my application, Serial No. 178,548, of which the present application is a continuation in part.

ifi-ln additional eradicating machine 51, of the same ty e as that shown at 41, for instance, may be inserted between the transformer windings 33 and the polyphase source of supply. The provision of such machine at this point may, under some circumstances, be instrumental in promoting the desired balanced conditions.

While i have illustrated and described a particular modification of a system constructed in accordance with my invention, it is apparent that those skilled in the art may make many modiiications therein, without departing from the spirit of my invention, and i desire, therefore, that it shall be limited only by the prior art or by the scope of the appended claims.

claim as my invention:

1. In an electrical system, the combination with a main generating machine, of an auXiliary dynamo-electric machine having a `field winding, means for varying the energia-ation of said field winding in accordance with the load conditions of said main machine, and means associated with said auxiliary dynamo-electric machine to deliver a current to the main generator to etlect a change in the frequency thereof.

2. In an electrical system, the combination with a main generating machine, of an auxiliary dynamo-electric machine having a. field winding, a switching device controlled in accordance with the load conditions of the main machine for varying the energization of the auxiliary dynamo-electric-machine field winding, and means associated with said auxiliary dynamo-electric machine to deliver a current to the main generator to effect a change in the frequency thereof.

3. In an electrical system, the combination with a main generating machine, of an auxiliary motor winding, a lield winding `associated therewith, means governed by the load litt) ccnditions on said main machine for varying the energization of the field winding, a mechanism associated with said motor winding for furnishing current to the main generator to vary the frequency thereof in accordance with said variation in the energization of the field winding.

a. In an electrical system, the combination with a main generator of a dynamo-electric frequency-changer, said frequency-changer being provided with a field winding, means for varying the current strength in said winding in accordance with the main generator load, and means for deriving a current from said frequency-changer and delivering it to the main generator to effect a change in the frequency thereof.

In an electrical system, the combination with a main generator of a dynamo-electric frequency-changer, said frequency-changer having a field-winding, means for varying the current strength in said winning in accordance with the main generator load, means associated with the frequency-changer to furnish a current to the main generator' to effect a change in the frequency thereof, and means for absorbing the undesirable currents which tend to pass into said frequency-changer from said main generator.

6. In an electrical system, the combination with a main generator of a dynamo-electric frequency-changer, said frequency-changer having a field-winding, means for varying the current strength in said winding in accordance with the main generator load, means associated with the freque1icyclianger for furnishing a current to the main generator to eifect a change in the frequency thereof, means for absorbing the undesirable currents which tend to pass into said frequency-changer from said main generator, and means for varying the voltage impressed upon said frequency-changer in accordance With an electrical quantit-y of the main gen` erator.

7. In an electrical system, the combination with a main polyphase machine, a second main polyphase machine, the armature of said second machine having current furnished thereto from the first-mentioned machine, and a single-phase system connected between said first-mentioned machine and said armature, of a dynamo-electric frequency-changer, said frequency changer having a field winding, means for varying the current strength in said winding in accordance with the load on one of said main machines, means associated with the frequency changer to furnish a current to the second main machine to effect a change in the frequency thereof, and means for absorbing the undesirable currents which tend to pass into said frequency changer from said second main machine.

v8, In an electrical system, a main induction motor, a main polyphase induction gen erator, the secondary winding of the motor being connected to the generating winding of the generator, a single-phase consumption system derived from between the two machines, and an eradicating machine for preventing the flow of undesirable currents from the generating machine to the motor.

9. In a combined phase converter and frequency converter, the combination with a pair of cascade-connected induction machines, one of said machines being adapted to be connected to an alternating-current system of one frequency, the other machine having a polyphase secondary winding, the cascade-connected windings being polyphase, of conductors connected to said cascade connections and adapted to be connected to an alternating-current system of a lower frequency, one of said systems being of a single-phase character, whereby energy may be transferred from one of said systems to the other, means connected in circuit with the secondary winding for varying the speed of said machines, and an eradicating ma chine for preventing the flow of undesirable currents between the cascade connected machines.

10. In a combined phase converter and frequency converter, the combination with a pair of cascade-connected induction machines, one of said machines being adapted Vto be connected with an alternating-current system of one frequency, the other machine having a polyphase secondary winding, the cascade-connected windings being polyphase, of a variable-frequency translating device connected to said secondary winding for varying` the speed of said machines, a trans lating device having a single-phase component connected to said cascade connections, whereby high and low-frequency curn rents tend to flow in said secondary winding, and means for substantially short-circuiting said high-frequency currents without short-circuiting said low-frequency currents.

l1. A dynamo-electric machine having a primary winding carrying currents having a single-phase component, a polyphase secondary winding, means connected to said secondary winding for varying the frequency of said primary currents, and an eradicating machine for providing a low-impedance path for undesirable currents in said sec ondary winding.

12. An induction generator having an armature winding and a polyphase field winding, a source of polyphase energy connected to said field winding, and means operative upon the occurrence of an abnormal power-demand on said generator for varying the frequency of said source in such manner as to reduce the armature frequency.

13. In combination with an alternating current supply system, an induction generator, a frequency converter of the type having a secondary Winding provided Wit-h a variable translating device for controlling the speed and a primary Winding provided with terminal connections and a comn'iutator member, means for utilizing said frequency@ converter as an exciter for said generator, and load-responsive means for varying said translating device.

14. In combination with an alternatingn current supply system, 'a generator, a frequency converter of the type having a secondary Winding provided With a. variable translating device for controlling the speed and a primary Winding provided With termina! connections and a commutator member, means for utilizing said frequency converter as an exciter for said generator, load-responsive means for varying said translating device, and frequency-responsive means for varying the exciting currentn In testimony whereof, I have hereunto subscribed my name this 27th day of March,

RUDOLF E. HELLMUND,

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