US1376429A - Phase-converter exciting system - Google Patents

Description

R. E. HELLMUND.

PHASE CONVERTER EXCITING SYSTEM, APPLICATION FILED AUG-7,1916.

4 SHEETS-SHEET I.

WITNESSES INVENTOR Rudolf E f/el/mund "ATTORNEY Patented May 3, 1921.

R. E. HE'LLMUND.

PHASE CONVERTER EXCITING SYSTEM;

APPLICATION FILED AUGJ, 1916.

1,376,429. Patented May 3,1921..

4 SHEETSSHEET 2.

000"! I! II a WITNESSES: INVENTOR 22 4 23M; film/f 5 m/mwyd a! a AT/TORNEY R. E. HELLMUND.

PHASE CONVERTER EXCITING SYSTEM.

APPLICATION FILED AUG-7,1916.

1,376,429. nte May 3,1921.

, 4 SHEET$SHEET 3.

WITNESSES: INVENTOR K E M. Z M a /f [flu/W0 R. E. HELLMUND.

PHASECONVERTER EXCITING SYSTEM.

APPLICATION FILED AUG-7.1916.

Patented May 3, 1921.

4 SHEETSSHEET 4.

I INVENTOR fiz/aa/f [T Hal/mafia A TToRNEY unmunno uu m moun -QM-0900000oomoooaoaoo-oo-oo WITNESSES UNITED srATEsP TsnT Fries.

RUDOLF E. HELLMUND, 0F Sl/VISSVALE, PENNSYLVANIA, ASSIGNOR TO WESTING- HOUSE ELECTRIC AND I'IHTNUFAGTUBING CQMPANY, A CORPORATION OF PENN- SYLVANIA.

PHASE-CONVERTER EXCITING i SYSTEM.

To all to 7mm it may concern:

Be it known that I, RUnoLr E. HELLMUND, a subject of the Emperor of Germany, and a resident of Swissvale, in the county of Alle gheny and State of Pennsylvania, have iii-- of the T-connected, rotary type, together with auxiliary automatic compounding and phase-correcting apparatus; Figs. 2 to 6, inclusive, and Figs. 8 to 13, inclusive, are diagrammatic views of modifications of the system shown in 1; and Fig. 7 is a sequence chart setting forth the order 01": switch manipulation in the system of Fig. 6 for the operation thereof in accordance with my invention. 1

In the operation of phase-converters, such, for example, as those employed for deriving three-phase currents ;trom a single-phase source or for balancing unbalanced polyphase systems, it is well known fact that, with an increase of load, there is a tendency for the secondary induced voltage to fall off because of the drops in the stator and rotor circuits. This is an undesirable condition as promotes unbalancing in the polyphase distributing system, with resultant unsatisfactory operation of polyphase apparatus connected thereto. In my copending appliation, Serial No. 108,567, tiled July 11, 1916, I set forth means whereby an extraneous voltage is introduced into the rotor circuits for forcing the load current therethrough as by a suitable synchronous booster. By suitable adjustment or" sail a xiliary voltage, the drop across the rotary terminals may be suitably compensated for and I may, in fact, by a further increase in said auxiliary voltage, compensate for the voltage drops in the primary winding itself and in associated apparatus.

t has been found that the load currents in the rotor circuits of a phase-converter are Specification of Zetters Patent.

Patented May 3, 1921.

Serial No. 113,454.

of twice the frequency of the supply circuit and it is'therefore necessary that the abovementioned, auxiliary, compensating volta e be of double frequency in order to properly perform its function.

In the present invention, I provide means whereby direct-current, exciting apparatus is combined with said compounding exciting means so that automatic control of the power-factor of the phaseconverter and of associated apparatus may be obtained.

Referring to Fig. 1. of the drawin tor a more detailed understanding of my invention, I show a phase-converter of the rotary type at 1 1, said phase converter comprising a primary stator winding 15, a secondary stator winding 16 and a rotor 17 provided.

with a three-phase winding 18. The windings 15 and 16 are joined to form the ordi nary T-connection, as is well known in the art. The outer terminals of the rotor winding 18 are connected, through suitable slip rings 19 and through the field windings 20-20 of a polyphase commutator machine 21, to the brushes of said machine. The rotor of he machine 21 is mounted on the shaft of the phase-converter 14 or otherwise mechanically coupled thereto so as to be driven thereby. -The field windings 2020 are circumferentially displaced, with respect to their associated brushes, so that they combine the effects of exciting and inducing windings. There is generated in the rotor of the machine 21, therefore, double-frequency currents of such amount and phase as to properly compound the machine A, compensating not only for ohmic but also for reactive dr ps therein, all as explained in detail in my store-mentioned application. An additional machine Q2. of the commutater type is also mounted upon the shaft of the phase converter 17 and comprisesan armature23, an exciting field winding 24 and a short-'circuited neutralizing or compensating field winding 25. The exciting winding 24 may be energized from any suitable direct-current source, such, for example, as a battery 26, through an adjustable resistor 27. The armature of the machine 22 is connected in circuit between one ofthe phases ofthe winding 18 and the machine 21.

With the connections as described, direct current is produced in the machine 22 and flows through the appropriate phases of the winding 18, causing the rotor 17 of the phase converter 14 to lock into synchronism and to thereafter run synchronously. By suitable adjustment of the resistor 27, the corresponding unidirectional field in the rotor 17 may be adjusted in strength, with corresponding adjustment ofthe power factor of the phase converter 14, as is well known in connection with the ordinary synchronous condenser.

An important function of the neutralizing winding 25 in the operation of the machine 22 is the elimination of the alternating cross-field which is set up therein by the fiow of a portion of the load current of the rotor 17 therethrough.

. It isunnecessary to employ two distinct machines on the shaft of the phase-converter, as the functions of a direct-current exciter and ofv an alternating-current exciter may be combined in a single machine. A system of this character is shown in Fig. 2 wherein, so far as possible, like parts to those employed in the system of Fig. 1 are denoted by like. reference numerals. The composite exciting machine is shown at 28 and includes a rotor 29 of such length that its windings may be under the influence of 'two stators, one of which carries the alter nating-current field windings 20-20 and the other of which carries the unidirectional current field windings 24 and 25. The machine 29 is shown as driven by a direct-current motor 30, rather than being attached to the shaft of the phase-converter, but, ohviously, either ofthese methods of driving may be employed, as is found most convenient.

The machine 23 is shown greatly exaggerated in dimensions, with respect to the phase-converter 14, for the sake of clearness but it will be understood that, in practice, said two machines bear substantially the same ratio to each other in size that is borne by the ordinary generator and its exciter.

I may go still further in simplifying the exciting means for a phase-converter by placing all the field windings therefor on a single stator, as indicated in Fig. 3. The composite exciter machine is shown at 31 and need be provided with but a single pair of brushes, as it is necessary to bring out but one phase from the polyphase rotor winding 18 of the phase-converter 14. The double-frequency alternating excitation of the machine 31 is provided by a single set of field windings 20, and a unidirectional current component of the excitation is provided by a field winding 24, as before. The field windings 20 and 24 should be mounted on separate polar projections,'and each polar projection carrying a portion of the unidirectional current winding 24 should be provided with a short-circuited field winding 25 in order to prevent alternating flux from threading the 001124.

Another system embodying a composite exciter is shown in Fi 4. The composite exciter 31 is of the polyphase commutator type and is provided with three exciting field windings 2020, operating as in Fig. 1. A fourth field winding 32 is mounted substantially in line with one of the field wind ings 20 and is excited by direct-current from a generator 33 driven by a repulsion motor 34. The circuit joining the generator 33 and the field winding 32 includes the secondary winding 35 of a transformer 36, the primary winding 37 of which is in series with the field winding 20 that is coaxial with the field windin 32. With these connections, the alternating current of the winding 20'induces an alternating electromotive force in the field winding 32 but the secondary winding 35 is so connected that the electromotive force of the transformer 36 is equal thereto and opposite in its effects. By this means, the harmful effect of the alternating fiux threading the field winding 32 in inducing an alternatin -current voltage in the unidirectional exciting circuit and producing resultant disturbance by superimposing alternatingwaves upon the unidirectional exciting currentis removed.

The exciter machme 31 is driven by a commutator motor 38, said motor comprising a g short-circuited armature 39, an exciting field winding 40 and an inducing field winding 41. The exciting field. winding 40 is connected across the supply transformer, and the field 41 is energized, in accordance with the load current of the phase-converter 14, through a suitable current transformer 42. Thus, the speed of the motor 38 varies with the load, which provides additional means for in creasing both the direct-current and the alternating-current excitation with the converter load, with resultant possibility of increased compensating'and compounding effects. The motor 34, driving the generator 33, is energized in accordance with the voltage of the secondary winding 16 of the phase-converter 14.

A still further consolidation and simplification of my system may be effected, as shown in Fig. 5, by combining the windings 20 and 32 of Fig. 4 into single winding 43 traversed by both the alternating and the unidirectional exciting currents. The transformer 36 operates as in the system of Fig. 4, eliminating the effect of the alternating fiux upon the unidirectional exciting current.

7 A certain compounding effect may be obtained, in a system of the character described, by placing the neutralizing field winding in series with the armature, designing it for slight over-compensation and then by shifting the armature brushes slightly away from the axis thereof. A

system of. this character is shown in Fig' 6 wherein an exciting machine 31 is provided with a single pair of brushes for connection in a single phase of the rotor winding of the phase-converter 14, and further comprises an exciting winding 44, a neutralizing winding and an additional field winding 46 in alinement with the winding 44.

The various elements of the system may be interconnected by suitable switches 47 to 54, inclusive. The winding 44 is connected to be energized from a direct-current source 26 which, in addition, supplies a driving motor 30 for the exciting apparatus. For starting, the switches 49 and 51 are closed, as indicated in Fig. -7, whereby the armature of tlie machine 31, the exciting field winding 46 and the neutralizing field wind ing 45 are all connected to the source in series with the primary winding of the phase converter. After the phase-converter has been started and brought up to substantially synchronous speed, the armature of the exciter 31 and the neutralizing field winding 45 are connected in series with the rotor winding of the phase-converter by closing switches 47, 48, 50, 52 and 53 and opening the switches 49 and 51, all as indicated in the chart of Fig. 7. Under these conditions, the field winding 44 supplies unidirectional excitation, and the field winding 46 is short circuited by the closure of the switch 53 to act as a damping winding and restrain alternating flux from traversing the winding 44. The field winding 45 serves as a compensating Winding and, in addition, supplies a small alternating-current field by reason of the brush displacement, said field inducing the desired alternating electromotive force for compounding.

In the system of Fig. 8, the exciter machine 31 is provided with a unidirectionalcurrent exciting winding 44, with an alternatingcurrent exciting winding 46 in alinement therewith and with a short-circuited neutralizing winding 54 in line with the brushes. The winding 44 is energized from the source 26, and a transformer 36 interlinks the supply circuit thereof with the circuit of the phase-converter for the neutralization of the alternating electromotive force induced therein. At the outset,

the switches 58 and 59 are closed and, for

subsequent operation, said switches are opened and the remaining switches closed. Thus, the winding 44 supplies a unidirectional field during normal operation and the Winding 46' furnishes an alternating field both during starting and subsequent operation.

In my aforementioned application, a system is disclosed in which the armature of the exciting machine is short circuited through the brushes and the load currents of the phase-converter traverse only the field windings of the exciter machine. In this manner, commutation troubles are avoided. Fig. 9 shows a system of this character wherein means are provided, in addition, for supplying a unidirectional exciting current. The exciter machine 31 is shown as of the polyphase commutator type, the field windings 20-20 thereof being connected in star to the rotor winding 18 of the phase-converter 14 and the commutator including three, equally-spaced brushes 61 which are connected together. A unidirectional-current source 62 is inserted in one of the main leads to the rotor 17, as in the system of Fig. 1. The exciter machine 31 is shown arranged to be driven from the car axle 63, ifthe system in ques tion is to be applied to a railway vehicle,

thus illustrating another variation of my invention.

As pointed out in my aforementioned ap plication, it may, in certain instances, be undesirable to have the exciter machine derive its exciting current from the hase-converter because of the harmful e set on the phase-converter power-factor. It was accordingly proposed to render the exciter machine self-exciting, particular attention being directedto' the desirable characteristics of the lVinter-Eichberg generator when used inv this connection. A system of this character is shown in Fig. 10 wherein the exciter machine 31 is provided with a unidirectional-current field winding 24 and with a short-circuited neutralizing or compensating winding 25 in line therewith. The armature of the machine 31 is provided with two sets of brushes 64'64 and 6565 having a quadratureirelation' to each other. The brushes 64-64, in quadrature to the exciting field winding 24, are connected in a phase of the rotor winding 18 of the phase converter 14. The brushes 65-65, in line with the exciting field winding 24', are connected together through the primary winding 35 of a transformer 36, the secondary winding of which is inserted in series with the brushes 64-64. By this arrangement, both alternating and direct-current excitation are derived from the machine 31, as will appear from the following consideration. Double-frequency rotor current from the machine 14 flows through the brushes 64-64 and establishes an alternating-field having a horizontal axis through the armature of the machine 31. Said alternating field produces a rotational, alternating electromotive force between the brushes 65-65, and said electromotive force is introduced into the converter rotor circuit by the transformer 36. The field winding 24, which is excited by direct current from the battery 26, produces a vertical field through the armature of the machine 31, which,'in turn,

produces a rotational unidirectional electromotive force between the brushes (i l-64 to produce a flow of direct exciting current through the winding 18 The alternating field established in line with the brushes 65-65 by the fiow of alternating current therethrough may be damped out either by a superimposed electromotive' force in the direct-current exciting circuit or by the inducing winding 25. The rotor current of the converter now has a direct-current component which establishes a unidirectional field in line with the brushes 64- -64, in ducing, in turn, a rotational unidirectional voltage between the brushes 65--65. By proper design, said electromotive force may be used to assist the field winding 24 in producing the total unidirectional-excitation of the machine 31.

The system of Fig. 11 is, in general, similar to that of Fig. 10 but the exciter machine 31 is rendered self-exciting, with respect to its unidirectional component, by connecting the field winding 2 between the brushes (E k-64 through a regulating resistor 27. The exciting system may be started by first causing the machine 31 to pick up as a selfexcited direct-current shunt machine as, for example, by opening a switch 66. Said switch is then closed, connecting the exciter through the rotor circuit of the converter, whereupon it supplies both alternating and direct current thereto. The field winding 2% has such a high resistance, as it is a shunt winding, that substantially no alternating fiux threads therethrough. The armature of the machine 31, however, carries both alter nating and direct current between the brushes 6464:, and, therefore, has both types of fields along the horizontal axes. Both alternating and direct rotational electromotivc forces are therefore induced between the brushes 65-65. The alternating component is transferred into the rotor circuit through the transformer 36, whereas the unidirectional component serves merely to strengthen the unidirectional field in the vertical axis.

The system of Fig. is the same as Fig. 11 except that a neutralizing winding 25 has been added to the machine 31, said winding being closed upon itself through an adjustable resistor 67. By this means, the alternating excitation may be adjusted, both in magnitude and in phase, thus rendering it possible to provide an alternating component of the exciting current that shall be out of phase with the rotor current of the converter. 7

It may, in some cases, be undesirable to use an exciter machine of the commutator type and, under these conditions, I may employ an alternating-current generator for the production of the desired double-frequency exciting current, as indicated in Fig.

13. The phase converter 14 carries, upon its shaft, the rotor 68 of an alternating-current generator 69 having twice as many poles as the phase-converter l t.- The rotor field winding 18 of the rotor it is connected through the armature coils 70-70 of the machine 69, said coils being arranged in star. The rotor 68 carries the usual direct-current, field windings 71. 1' of an alternatingcurrent generator of the rotating field type, said field windings being energized from a source 72 through suitable slip rings 73. The source 72 constitutes a shunt-excited direct-current generator driven by a commutator motor 7%, the armature of which is connected across the secondary winding 16 of the machine 1%. The motor 7 1 further comprises an exciting field winding 7 5 which is energized in accordance with the load current by a suitable current transformer 76. The connections are such that an increase in load producesa decrease in the component of the field electromotive force which is in line with the armature electromotive force, thus causing an increase in the speed of the motor 75 with an increase in the load. The motor 75 may further be provided with 'a .short-circuited inducing winding 77. A directurrent component for chase correction may be inserted in the connection to one phase of the rotor circuit 18, as indicated at 78.

iVith the system arranged as above described, the fact tln t the exciter machine 69 has twice as many poles as the phase-converter le produces a double-frequency exciting current, as is desirable for compounding. By virtue of the supply connections shown, the speed of said exciting machine varies with the load, thus still further enlianciiigtlie compounding effect.

in all oft-he herein-described systems, it will be recognized that the direct and alterhating exciting currents combine, as actually supplied to the phase-converter, to form a single exciting current of pulsating'or unsymmetrical alternating form.

While I have shown my invention in a plurality of forms, it will be obvious to those skilled in the art that it is susceptible of'various minor changes and modifications without departing from the spirit thereof and I desire, therefore, that only such limitations shall beplaced thereupon as are imposed by the prior artfor as are set forth in the appended claims.

j I claim as my invention:

1. The combination with a phase-converter of the rotary type, of cooperating means for 'conductively supplying both direct and alternating currents to asecondary winding thereof.

2. The combination With a source of alternating current, of a phase-converter of the rotary type, and cooperating means for'conductively supplying both direct current and alternating current of twice the frequency of said source to a secondary winding of said converter.

8. The combination with a phase-converter of the rotary type provided with a wound secondary member, of a source of pulsating current, and connections from said source to a winding of said secondary memher.

4. The combination with a phase-converter of the rotary type provided with a wound secondary member, of an auxiliary dynamo-electric machine, driving means therefor, connections from the terminals thereof to a secondary Winding of said converter, and means for simultaneously producing unidirectional and alternating exciting fields in said auxiliary machine.

5. The combination with a source of alternating current, of a phase-converter provided with a wound secondary member connected thereto, and means for supplying pulsating current to a winding of said secondary member, the frequency of pulsations thereof being substantially twice the frequency of said source. 7

6. The combination with a source of alternating current, of a phase-converter of the rotary type connected thereto, an auxiliary dynamo-electric machine, driving means therefor, connections from the terminals of said auxiliary machine to a secondary winding of said converter, means for producing a unidirectional exciting flux in said auxiliary machine, and means for simultaneously producing an alternating exciting flux in said auxiliary machine of substantially twice the frequency of said source of alternating current. i

In testimony whereof, I have hereunto subscribed my name this 21st day of July,

RUDOLF E. HELLMUN D.

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