US781805A - System of electrical distribution. - Google Patents

Description

No. 781,805. PATENTED FEB. 7, 1905.

, T. BODDE.

SYSTEM OF ELECTRICAL DISTRIBUTION.

APPLICIATION FILED NOV.18, 1903.

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No 781,805. PATENTED FEB. '7, 1905. T. BODDE.

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APPLICATION FILED NOV.18, 1903.

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SYSTEM OF ELECTRICAL DISTRIBUTION.

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PATENT OFFICE.

THEODORE BODDE, OF SGHENEGTADY, NEW YORK.

SYSTEM OF ELECTRICAL DISTRIBUTION.

SFEGIFICATION forming part of Letters Patent No. 781,805, dated February '7, 1905.

Application filed November 18, 1903. Serial No. 181,707.

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Be it known that I, THEODORE BODDE, a subject of the Queen of the Netherlands, residing at Schenectady, county of Schenectady, State ofNew York, have invented certain new and useful Improvements in Systems of Electrical Distribution, of which the following is a specilication.

My present invention relates to methods and means for deriving a rectified current from a source of alternating current; and it consists of certain novel features pointed out in the claims concluding this specification.

The following 'is a description of the struc tures shown in the accompanying drawings, which illustrate mechanisnfembodying my invention in forms at present preferred by me; but it will be understood that various modifications and changes may be made without de parting from the spirit of my invention and without exceeding the scope of my claims.

Figure 1 represents a system embodying my invention. Figs. 2, 3, 10, 11, 12. 13, and 14 are diagrams showing suitable relations for different-phase commutations. Figs. l and 5 are illustrations of other modes of obtaining the currents in suitable phase relation for commutation. Figs. 6 and 7 illustrate the application of an electric-current valve for diminishing sparking at the commutator. Figs. 8, 9, and 16 illustrate other means for diminishing sparking at the commutator. Fig. 15 illustrates the application of an electric-current valve to an alternating-current switch.

One obstacle to the use of commutated alternating currents as heretofore produced has been the fluctuating or pulsating character of such currents. By employing multiphase currents the fluctuation is reduced greatly as compared to single-phase currents; but it is still too great for many uses, particularly the operation of motors. This difliculty I overcome by using two or more sets of currents, two being usually suflicient, supplied by any suitable induction apparatusas, for example, generators or transformersso arranged that the currents in the several sets divide the time between the successive commntated phases of the other. For an even number of phases the angle between sets is preferably equal to the angle between phases divided by the number of sets. For an odd number of phases in a symmetrical system it is preferably the angle between phases divided by twice the number of sets. Thus with so-called quarter-phase currents where two sets are employed they should be forty-live degrees apart, while with three sets they should be thirty degrees apart. I prefer to use threephase currents and two sets, the latter being thirty degrees apart. if three sets be employed,1 prefer they should be twenty degrees apart. If three-phase currents are commutated in ordinaryfashion, the resulting rectified current fluctuates about lifteen percent. which is too great for many purposes; but by combining two sets of three-phase currents, as above described, it is reduced to less than three and one-half per cent, which is practicable for all ordinary commercial pur poses.

Fig. 1 shows means for generating threephase alternating current, the current so produced being passed through constant-potential or constant-potential to constant-current transforming apparatus and then to rectifying-commutators, the whole arrangement being represented diagrammatically. The source of three-phase current is conventionally indicated at l, the exciting field-windings at 2, and the exciting source at 3. The generator-terminals l 5 6 supply current to corresponding transmission-lines, as indicated. These may represent any three-phase transmission-circuits for connection to any desired translating devices. To these transmissionlines 1 5 6 I connect a suitable three-phase transforming apparatus, which may be adapted to transform at constant potential or at constant current, both forms of apparatus being well known in the art. 1 show two sets of transforming apparatus '7 and 8, so connected that the three-phase currents delivered from each shall not correspond in phase, but shall differ from one another by thirty degrees, a suitable arrangement being the connection of three transformers delta fashion in one set and star fashion in the other set. Any other suitable arrangement for producing in each of the circuits of one apparatus a phase differsemi-1i ence intermediate between two of the phases of the other apparatus may be employed. Leads 9 and 10 and 11 from secondaries of apparatus 7 lead to commutator 15 through suitable collecting-rings and leads 12 13 14 lead to commutator 16 in similar manner. The commutators are driven in synchronism with the waves of the alternating currents by any suitable means-as, for example, a synchronous motor 17 supplied with alternating current through leads 18 from the transmissionlines t 5 6.

It will be understood that the foregoing illustration of generators and transforming apparatus typifies any suitable induction apparatus, it being immaterial whether the currents are obtained directly from one or more generators properly related or by means of transformation in any suitable manner.

Figs. 2 and 3 show diagrammatically the relations of the two sets for three-phase and quarter-phase currents, respectively. The eommutators 15 16 have their segments displaced, as shown, while the pairs of brushes Z) and 7/ are in the same vertical plane.

In Fig. 4L I show an arrangement for obtaining the two sets of threephase currents in suitable relation from the two circuits of a quarter-phase system, the resulting phase relations being indicated diagrammatically. In Fig. 5 I show an arrangement for obtaining two sets of quarter-phase currents from a set of quartenphase mains. In both these figures, t represents the primaries and If the secondaries of suitable transformers.

The rectifying-commutator may be of any ordinary type. The two cornmutators15an l 16, Fig. 1, are connected in series with each other, and to the leads extending therefrom are connected translating devicesas, for instance, arc-lamps. These are arranged in series in the circuit 19, but may be arranged either in series or in parallel, according as constant-potential or constant-current transforming apparatus is employed in accordance with ordinary practice in constant-current and constant-potential circuits. here series arrangement is employed, translating devices may be interposed in the portion of the circuit joining the two commutators in ordinary multicircuit fashion. The alternating-current terminals may be connected to the commutator-segments and the rectified current taken from the brushes in the usual manner; but I have devised forms which I prefer to use in some instances in which the alternating-current terminals may be connected to brushes and the rectified current be taken from the commutator-segments by suitable slip-ring connections. In Figs. 10 and 11 I illustrate this last arrangement diagrammatically for use when two sets of three-phase currents are employed, the brushes 6 and Z) of one set being angularly displaced from those of the other by the necessary angle in Fig. 10, while the commutator-s 15 16 are similarly displacedin Fig. 11, with the brushes in line. In Figs. 12 and 13 I show similar arrangements for quarter-phase currents. Fig. let shows a single commutator for use with two sets of currents displaced forty-live degrees. A similar arrangen'ient may be employed for three-phase currents, as will be understood. I prefer in any case to use a separate commutator and brushes for each group of current phases and connect them in series, as already described; but this is not necessary, a single commutator of suitable construction may be employed or as many single segment-rings as there are necessary segments may be used with insulating-rings between them, as will be understood. In all cases it is desirable to see that the circuit is never opened during any change of connection, this being of particular importance where constant-current transformers are employed.

I will now describe that part of my invention relating to the suppression or avoidance, to a greater or less extent, of sparking at the commutator of the rectifying apparatus.

Referring to Fig. 6, two connecting-brushes B B are employed at each terminal of each rectifying-commutator 15, the width of space between such brushes being so proportional that the current flowing through the brush on the leaving commutator segment shall always fall to Zero before contact with that segment is broken. If comn'lutation always takes place at the instant when this current is Zero, sparkless operation of the rectilier will result; but if it takes place prior or subsequent to the instant of zero current a spark will result, its size depending upon the potential existing or upon the energy to be discharged in the leaving-leg of the circuit; but the currents in the two cases would be in opposite directions. To insure the discharge of the circuit, the brushes in Fig. 6 are so spaced and angularly related that the current shall fall to zero for all conditions of operation before change in circuit connection is completed. This would normally cause the two brushes and their co1mecting-circuit to act as a short-circuit upon the. two portions of the circuit included between the commutator-segments. To prevent this connection from being effective as a short-circuit, I insert in the circuit between the two brushes an electric current-valve 30, such as a Pollack aluminium cell or a mercury or other vapor tube such, for instance, as that of Hewitt, which as at present developed is chiefly useful in high-potential circuits which permit of the discharge of a current in one direction only or a device opposing the liow of cur rent in one direction to a greater extent than in the other, such device being so connected as to permit the continuation of the currentflow while the current in the leading brush is falling to Zero, but to prevent flow of a current in the reverse direction during the interval between Zero current and the disconnection of the brush from the leaving commutator-segment. The effect of this arrangement is practically to prolong the condition of Zero current during an interval sufficient to complete the change in circuit connections, the prolongation being effectively equal to that angle of rotation which will establish a potential between the two segments Whose connections are being shifted equal to the effective opposing electromotive force of the electrolytic cell or vapor-tube. This interval can be increased, therefore, by. using two or more cells in series, according to the electromotive force likely to be encountered in practice. I prefer to give the commutator-segments as large separation as possible and to make the following brush of comparatively greater width, particularly in constant-potential commutation, the leading brush being of comparatively narrow width. By so doing increased separation of commutator-sections is possible, and hence decreased danger of short circuit. By the use of this arrangement I am able to insure that change of circuit connections shall take place at instants of practically no current. In cases Where the theoretical position of correct commutation varies through a large angle this device may be combined with means for automatically varying the occurrence of commutation with respect to, the alternating electromotive force and current-waves, as hereinafter described; but such combination is not always necessary, as the usual hand adjustment is in many cases sufficient.

Fig. 7 shows another arrangement in which three brushes B, B, and B are employed. This reduces the conduction necessary in the electrolytic cell or vapor-tube and is useful in cases where large currents are to be rectified. In this arrangement it is necessary that the apparatus be so proportioned and adjusted that the leaving segment pass from under the middle brush before the current in that leg of the circuit has fallen to zero. I do not limit myself to the use of this feature of my invention in connection with rectifiers, properly so called, since it may be employed to prevent sparking in the commutation of open-circuit dynamos and even in the use of high-tension switches for alternating current. Fig. 15 shows diagrammatically such a switch arranged to first open the main circuit by the middle set of. contacts 4:0 40, thereby throwing the vapor-tubes 41 4:2 into the circuit to be opened in opposite senses, so that each tube receives every other impulse. A further movement of the switch simultaneously opens the upper and lower contacts 4:3 43 through the tubes. The tubes are in circuit each with a suitable starting means, such as a battery M and coil 45.

In order to reduce to a minimum the amount of sparking or tendency to spark in the operation of the eommutators, it is desirable that the instants of change in circuit connections should take place at such points in the current-waves that the balance of electromotive forces across the rectifier-segments should be as perfect as possible. If the currents have a variable value, this requires that the relative positions of the commutator and brushes at the instant of commutation vary with respect to the current-wave, while variations of current phase with respect to electromotivc force without change of current require that the instant of commutation should occur in variable relation to the electromotive-force waves.

Moreover, in a constant-potential to constant I current transformation and rectification, since variations of secondary energy with constant current mean variations in primary current it is necessary that the instants of commutation vary with respect to the secondary-current waves for each change in secondary or unidirectional voltage. I have discovered that by automatically varying the instants of commutation with respect to each of these variations in work-circuit conditions, whether occurring simultaneously or separately, (thus making the instantaneous relations of commutation and brushes variable with respect to both electromotive force and current-waves and dependent only upon changes in the work circuit,) substantially sparkless commutation can be attained, and I show certain means of attaining such automatic variation with a high degree of perfection. Since, however, instantaneous adjustment is impossible with any device possessing inertia, I prefer to employ in connection with said apparatus some form of current-valve such, for example, as hereinbefore described.

To cause the transfer of circuit connections to take place automatically at varying points in electromotive-force or current waves, or both, as may be required for minimum sparking, I retard or accelerate the rotation of the driving-shaft momentarily without departing from ultimate synchronous rotation, such positive or negative acceleration resulting in changing the relative instants of coincidence of any given point on the commutator with the brushes. In Fig. 8 I show one means of effecting this result with any relatively flexible driving connection, such as a synchronous motor or flexible spring connection, a synchronous motorbeing shown. In Fig. 9 I show another method which is useful in certain cases and applicable only where a synchronous motor is the driving means. In Fig. 8,

17 is a synchronous motor driving the rectifier (not shown) and having upon its shaft a disk 50, preferably of a metal having a lowtemperature coefficient. Embracing this disk are magnet-poles 21 22 of magnet )0, surrounded by coils and (51 in series with and in shunt to the rectified circuit, respectively, suitable means of adjustment being preferably provided, such as a switch, for varying the number of turns in the series coil and a resistance in series with the shunteoil. I

In the case of constant-potential commutation the series coil is the chief energizing source for the magnet 20, while in the case of constant-current commutation the shuntcoil is the chief energizing source. In each case the other coil may be entirely omitted in some instances. The object in either case is to apply to the rectifier-shaft an additional load varying with the load upon the circuit and sufficient to cause a relative retardation of the rectifier shaft by the amount necessary to cause the instant of change of circuit connection to occur at such points in the waves of alternating current as will result in the smallest value of unbalanced electromotive force between the circuits to be separated. In case a synchronous motor is the driving means such variation in load, as is well known, will cause a change in the instantaneous relations of the stationary and rotating elements,

and by proper proportioning this angular adjustment of position will be of such an amount as to result at all leads in minimum sparking of the rectifier. For the purpose of adjustment a coil is provided whose effect varies only with change in the constant or normally fixed factor-that is, the shunt-coil in the case of the constant-potential commutation and the series coil where constant currents are employed. An adjustable magnetic circuit may also be employed as, for instance, an adjustable pole-piece 21, Fig. 8-the adjustment being effected by means of the adjustable screw 53.

means and the rectifier is of large size, the magnet may be rotated and the disk stationary. In this case the disk may be flexibly mounted and arranged to operate a resistance in the eXciter-circuit of the synchronous motor to effect the same result. This is shown in Fig. 16, in which 17 is a synchronous motor having exciting-coils 62 63 energized by a suitable source of current 64:, which may or may not be derived from the rectified circuit. 65 is a resistance in the exciting-circuit and controlled by the angular motion of the disk 50 through a gear 66 and rack 67, said rack being restrained as to longitudinal motion by the spring 68 68 on its opposite ends. Upon the motor-shaft is a magnet 20, rotating in proximity to the disk. In Fig. 9 .1. indicate diagrammatically a synchronous motor 17 as the driving source having exciting-coils 51 52 in series and in shunt, respectively, with rectifier-circuit, the two windings being so proportioned as to cause an angular advance or retardation of the rotating with respect to the fixed element with varying load in the rectil \Vhere a synchronous motor is the driving t tier-circuit, thus varying the instant of change of circuit connection.

In case of constai'it-current comn'iutation it is advantageous to connect the synchronous motor in series with one or more of the circuits whose currents are to be rectified, as by so doing a full adjustment for variation in the current phase in the circuits to be rectified may be attained. \Vhere a synchronous motor is the driving means, the arrangements of Figs. 8 and 9 may be combined in one apparatus.

IVhile I have described several means for prevention of sparking in rectifiers and all may be used together, I do not limit myself to such use, since either the electric-current valve commutation or the adjustment of time of connnutation to vz'rrying circuit conditions to preserve a minimum unbalanced potential across adjacent segn'ients whose connections are being shifted may be used separately. and either of these may be used with either single-phase current or with multiphase current of any number of phases or set of phases.

In the foregoing specifications l, have referred to various modifications which may be employed in the practice of my invention; but I have not attempted to describe all the modifications which might be en'iploycd, the ob- 'ect of these s )ecifications bein to instruct J h those skilled in the art how my invention may be practiced in forms at present preferred by me.

All the details above described are not necessary to the several features of my invention separately and broadly considered, and this will be indicated in the concluding claims, where the omission of an element or feature described will be understood to be a specific declaration that the omitted element or feature is not essential to the invention therein specified.

\Vhat I claim as new, and desire to secure by Letters Patent of the United States, is-- 1. In a system of electrical distribution the combination of means for generating a plurality of multiphase currents, the phases of one current being intermediate in time between the phases of another, and a rectifying apparatus to which said currents are conducted.

2. In a system of electrical distribution, the combination of a multiphase transmission-circuit, two or more sets of transforming apparatus differently related to the transmissioncircuit and a rectifying apparatus connected to all the sets.

In a system of electrical distrilnition the combination of a multiphase transmission-circuit two or more sets of transforming apparatus so related that the phases of the secondary currents in the subsequent groups occur at times dividing the interval between phases in the first group.

4. Ina system of electrical distribution, the

combination of a multiphase transmission-circuit, two or more sets'of transforming apparatus so related that the phases of the secondary currents in the subsequent groups occur at times dividing the interval between phases in the first group, and rectifying apparatus connected to all the groups.

5. In a system of electrical distribution, the combination of a multiphase transmission-eircuit, two or more sets of transforming apparatus so related that the phases of the secondary current in the subsequent groups occur at times dividing the interval between phases in the first group, rectifying apparatus connected to all the sets and transmitting-lines leading to translating devices and receiving in series the rectified currents of the several groups and phases.

6. In combination a circuit carrying alternating current, a device opposing the flow of current in one direction to a greater extent than in the other, and means for first inserting said device in circuituntil the current falls to Zero and then interrupting the circuit.

7. The combination with a commutator and brushes of a device opposing the flow of current in one direction to a greater extentthan in the other connected in the brush-circuit when it is breaking and making contact with successive commutator-segments.

8. In combination, a circuit, means for reversing a portion of said circuit, a device opposing the flow of current in one direction to a greater extent than in the other and means for momentarily inserting said device into the reversible portion prior to its reversal.

9. In a commutating device a commutator, two or more sets of brushes therefor each set having a leading brush and one or more following brushes combined with a device interposed between said leading brush and the remainder of the same set which offers but slight resistance to the normal flow of current through said brushes of the same set in parallel, but opposes a flow of current through them in series.

10. In a rectifying device for changing altel-nating into continuous currents, a commutator and brushes therefor constituting the terminals of a continuous-current circuit, an auxiliary brush for each terminal brush and located in advance thereof in the direction of rotation combined with a device connected between said auxiliary brush and its terminal brush opposing a flow of current through it in a direction reverse to that normal to the circuit.

11. The combination of conductors carrying alternating current, rectifying devices and means for varying the time of commutation with respect to both current and electrometive-force phase.

12. The combination of conductors carrying alternating currents, a rectifying-commutator, collecting-brushes therefor, means for imparting relative motion between commutator and brushes and means for causing such variation in theangular velocity of rotation as shall cause the coincidence of brushes with commutation-points to occur at non-corresponding points in successive alternating electromotive-force waves.

13. The combination of conductors carrying alternating currents, a rectifying-commutator, col ecting-brushes therefor, means forimparting relative motion between commutator and brushes, and means for causing such variation in the angular velocity of rotation as shall cause the coincidence of brush with commutation-points to occur at non-corresponding points in successive alternating electromotive-force waves, whereby variation of load and of current-phase lag are accompanied by corresponding changes in time of commutation.

14. In a rectifying apparatus for changing alternating into unidirectional currents, a rectifying-eommutator and brushes combined with means for imparting relative motion thereto and automatic electrically-controlled means for varying the angular velocity for causing a given relative position of commutator and brushes to occur at non-corresponding points in both current and electromotive-force waves.

15. In a rectifying apparatus for changing alternating into unidirectional currents, a rectifying-commutator and brushes combined with means for rotating one relative to the other, and automatic electrically-controlled means varying the motion, for causing the rectification to take place at noncorresponding points in current and electromotive-force waves.

16. In a rectifying apparatus for changing alternating into unidirectionalcurrents, a rectifyingcommutator and brushes combined with means for rotating one relative to the other synchronously with the alternations, and means for varying the time of commutation by causing instai'ltaneous retardation or acceleration of angular velocity corresponding to increase or decrease of load.

17. In a rectifying apparatus for changing alternating into unidirectional currents, a rectifying-commutator and brushes combined with means for rotating one relative to the other synchronously with the alternations, and means for varying the time of commutation by causing instantaneous retardation or acceleration of angular velocity corresponding to the later or earlier occurrence of a commutation eleetromotive force necessary to effect minimum sparking with varying circuit conditions.

18. In a rectifying apparatus for changing alternating into unidirectional currents, a rectifying-commutator and brushes combined with means for rotating one relative to the other synchronously with the alternations,

and means for varying the time of commutation by causing instantaneous retardation or acceleration of angular velocity to bring the instant of commutation at such points in the electromotive-force waves as will give minimum sparking with varying circuit conditions.

19. In a rectifying apparatus for changing alternating into unidirectional current the combination of a rectifying-commutator and brushes, means for rotating one relative to the other, and an electricallycontrolled means excited by the rectified currents for causing an instantaneous acceleration or retardation of angular velocity corresponding to the earlier or later occurrences of a commutation electromotive force necessary to effect minimum sparking with varying circuit conditions.

20. In a rectifying apparatus for changing alternating into unidirectional currents the combination of a rectifying-commutater and brushes, means for rotating one relative to the other and an electrically-controlled means excited both in series with and in shunt to the rectifying-hrushes, for causing a retardation corresponding to the delay in the occurrence of a commutating electromotive force necessary to effect minimum sparking with varying circuit conditions.

21. In combination a source of alternating current, a rectifying apparatus comprising commutator and brushes, means for rotating one relative to the other, a brake-disk and magnet and circuits excitingthe magnet and connected both in series and in shunt to the rectifier-brushes.

22. In combination a source of alternating current, a rectifying apparatus comprising commutator and brushes and a synchronous motor rotating one relative to the other, such motor being fed from the circuit from which the current to be rectified is drawn, and excited both in series with and in shunt to the rectifying-brushes.

rality of multiphase currents, the phases of one current being intermediate in time between the phases of another combined with a rectifying apparatus to which said cu rren ts are conducted, said apparatus comprising a rectifying-commutator and brushes, means for imparting relative motion thereto,automatic electrically-controlled means for varying the angular velocity for causing agiven relative position of commutator and brushes to occur at non-corresponding points in both current and electromotive-force waves and a device opposing the flow of current in one direction to a greater extent than in the other connected in the ln'ush-circuit when it is breaking and making contact with successive connnu tator-segments.

25. In combination, a circuit, means forsuccessively reversing portions of said circuit synchronously with the alternations of current therein, devices opposing the How of current in one direction to a greater extent than in the other and means for inserting said devices into the portions to be reversed prior to the fall of current therein to zero and disconnecting said portions after the current has fallen to Zero.

26. In a rectifying device a connnutator and brushes concatenated multiphase circuits connected therewith, an electrolytic valve device opposing the flow of current in one direction to a greater extent than in the other, and means for connecting said device across adjacent multiphase terminals prior to the decline of the electromotive force between said terminals to zero.

27. In a rectifying apparatus,a commutator, an alternating current circuit or circuits whose terminals are connected to the segments at said commutator, electric valve devices opposing the flow of current in one direction more than in the other and means for so inserting said devices into the rectified circuit and across adjacent commutater-segments as to permit the free passage of current through them in the direction of normal How in the rectified circuit but to oppose a [low of cur rent from one segment to the next in a direction reverse to that normal to the rectilied circuit.

In testimony whereof I have signed my name to this specification in the presence of two subscribing witnesses.

TIIEODORIC BUDDIC.

W itnesses:

I1. N. W A'IERMAN J. EDGAR BULL.

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