US1224255A - Transforming system. - Google Patents

Description

V. E. ALDEN.

TRANSFORMING SYSTEM.

APPLICATION FILED MAR. 30,1915- Patented May 1, 1917.

WITNESSES INVENTOR ATTORNEY UNITED STATES PATENT OFFICE.

VERN E. ALDEN, OF WILKINSBURG. PENNSYLVANIA, ASSIGNOR TO WESTINGHOUSE ELECTRIC AND MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA.

TRANSFORMING SYSTEM.

Application filed March 30, 1915.

To all whom it may concern:

Be it known that I, VERN E. ALDEN, a citizen of the United States, and a resident of WVilkinsburg, in the county of Allegheny and State of Pennsylvania, have invented a new and useful Improvement in Transforming Systems, of which the following is a specification.

My invention relates to distributing systems for alternating currents, and it has special reference to systems that employ alternating currents of different numbers of phases.

More particularly, my invention relates to transforming systems of the above-mentioned character in which a plurality of transformers that embody dissimilarly-connected windings are utilized.

My transforming system is applicable where a plurality of unlike transformers are arranged in multiple-circuit relationship in order to tie together two distributing systems that transmit alternating currents of different numbers of phases. For such purposes, it is frequently necessary to employ a transformer having delta-connected primary and secondary windings in combination with a transformer having one Y-connected winding and one. delta-connected winding. To this end, I have invented the present transforming system for inter-connecting transformers of the above mentioned character in order to transfer energy between two systems that transmit alternating currents of unlike numbers of phases.

For a betterunderstanding of the nature and scope of my invention, reference may be had to the following description and the accompanyingdrawing in which Figure 1 is a diagrammatic view of a distributing system comprising transformers the windings of which are connected in accordance with my invention; Figs. 2, 3, 4i, 5 and 6 are vectorial diagrams illustrating the relationship of the voltages obtaining in the group of transformers comprising the delta and Y-connected windings, and Figs. 7 8, 9, 10 and 11 are vectorial diagrams illustrating the relationship of the voltages obtaining in the group of transformers comprising the delta-connected windings.

Referring to Fig. 1, a transmission system for two-phase alternating currents com- Patented May 1, 1917.

Serial No. 18,005.

prises conductors 12, 13, 14 and 15 which are connected to a two-phase source of supply 10. It is desired to interconnect, for the transference of energy, the aforementioned two-phase distributing system with a threephase distributing system comprising conductors 17, 1S and 19 which are connected to a source of three-phase supply 20. Under certain conditions, it may be undesirable to interconnect the two systems by Scott-connected transformers solely. To this end, I propose the use of two transformers having dissimilarlyconnected windings, which transformers are to be used in conjunction with Scott-connected transformers.

For the purpose of illustration, assume that a transformer having one delta-connected and one Y -connected winding and a transformer having two delta-connected windings are available. The amount of energy to be interchanged between the twophase and three-phase systems is such that it is necessary to employ both of the abovementioned transformers in order to provide ample capacity for handling such large amounts of power. A two-phase transformer 21, having a winding 22 connected across the phase 1l15 and a winding 23 connected across the phase 12 and 13, is provided with secondary windings 24 and 25 which are connected in or Scott relationship. The secondary windings of the transformer 21 are connected, by means of conductors 262728, to a Y-connected three-phase winding 29 of a three-phase transformer 30. Inasmuch as three-phase voltages are available from the T-connected windings 2st and 25 which are equal in value and 120 degrees apart in phase relationship, the voltages which are impressed upon the Y-connected winding 29 are equal in value and 120 degrees apart in phase relationship. Similarly, the voltages induced in a delta-connected winding 31, which is in inductive relation to the Y-connected winding 29, are equal in value and 120 degrees apart in phase relationship.

In combination with the group of transformers comprising the delta-connected and the Y-connected windings for interconnecting the two-phase and three-phase systems, a second group of transformers comprising a transformer 32 is employed that is similar tothe above-mentioned transformer 21. In

this instance, however, the winding 22 is connected across the phase 1213, and the winding 23 is connected across the phase 1415. The three-phase voltages available from the T-connected windings 24: and 25 are impressed upon a delta-connected winding 33 of a transformer 34. A second deltaconnec'ted winding 35, which is in inductive relationship with the delta-connected winding 33, is connected to the three-phase transmission conductors 1718 and 19, as explained in connection with the delta-connected winding 31 of the transformer 30.

In interconnecting these two transforming systems, it is essential that corresponding voltages impressed upon the three-phase distributing system must be equal in value and coincident. To explain how this is accomplished, reference may now be had to the vector diagrams, the group of diagrams relating to the delta and Y-connected transformer windings being considered first. In all cases, the vectors representing the voltages are shown in their proper positions, in space, with respect to one another, but, since the values of the voltages in the various windings are unimportant and variable except to obtain proper service conditions, the lengths of the vectors are unimportant.

To facilitate in understanding the phase relationships of the voltages, we will first consider the voltages obtaining in the group" of transformers comprising the Y-connected. winding 29 and the delta-connected winding;

31 of the transformer 30. I? In Fig. 2, vectors 31 31 and 31 represent, in value and in phase relationship, the voltages induced in the correspondingly marked windings 31, 31 and 31 of the delta-connected winding 31. The voltages induced in the Y-connected winding 29 are represented as shown in Fig. 3, respectively, by vectors 29 29 and 29 which have the same position in space as the vectors 31, 31 and 31, respectively, of Fig. 2. Inasmuch as the winding 29 is a Y-connected winding, the voltages across the conductors 26, 27 and 28 are represented by vectors 2726, 2628 and 2827 of Fig. 3. It will be apparent that the voltages impressed across the three- phase conductors 26, 27 and 28 are displaced 30 degrees in phase relationship from the vectors 31 31 and 31, respectively, of Fig. 2. In order to under stand clearly the phase relationship of the voltages impressed upon the bcott or T- connected windings 24 and 25, Figs. t and 5 are taken in conjunction, the vectors of Fig. 4 being assembled to form an equilateral triangle, the sides thereof being properly disposed, however, to represent the positions, in space, of the vectors representing the above-mentioned voltages 27 26, 2628 and 28-27. It will be readily seen that the voltage impressed upon the winding 24. is equal in value to, and is in phase coincidence with, the voltage across the coi1- ductors 26-28, and, consequently, the vector 24 of Fig. 5 is equal in value to, and is in phase coincidence with, the vector 2628 of Fig. 4. The voltage impressed upon the winding 25 is represented by the vector 25 of Fig. 5 which corresponds, in phase and in value, to the altitude of the equilateral triangle of voltages of Fig. 4. Again, the voltage induced in the winding 22 is in phase coincidence with the voltage vector 24; and is represented by the vector 22 of Fig. 6, and, likewise, the voltage impressed upon the winding 23 is in phase coincidence with the voltage vector 25 of Fig. 5 and is represented by the vector 23 of Fig. 6. From the foregoing, it will be apparent that the vectors 22 and 23 of Fig. 6 are equal in value and spaced 90 degrees apart in phase relationship, thereby corresponding to the voltages of the two-phase distributing system.

Referring now to the vector relationship of the voltages obtaining in the group of transformers comprising the delta-connected windings 33 and 35 of the transformer 34, reference may be had to the vector diagram shown in Figs. 7, 8, 9, 10 and 11. Inasmuch as the winding 35 ,is similar, in all respects, to the wind- {ing 31, vectors 35 35 and 35 of Fig. .07, representing the voltages of the deltavu connected windings 35, are in phase co- ;incidence with the voltages 31 31 and1 B1, respectively, of Fig. 2. Inasmuch as {the winding 33 is delta-connected and inq'tluctively related to the winding 35, vectors [33% 33 and 33, representing the voltages linduced in the winding 33, are in phase co- ,incidence, in space, with the corresponding lvectors representing the voltages in the winding 35, as shown in Fig. 8. By regrouping the vectors of Fig. 8 to form an equilateral triangle, as shown in Fig. 9, it is apparent that the voltages across conductors 26*, 27 and 28 are represented as being equal to, and in phase coincidence with, the corresponding vectors of Fig. 8.

Since the voltage impressed upon the winding 24* is equal to, and in phase 00- incidcnce with, the voltage represented by the vector 33*, it may be represented by the vector 24 of Fig. 10. The voltage impressed upon the winding 25*, which, as before mentioned, is connected in T relationship with the winding 24, is represented, in value and phase relationship, by the altitude 25 of the equilateral triangle of Fig. 9 and is shown in Fig. 10 in its proper phase relationship, or 90 degrees out of phase with the vector 24;. As previously demonstrated, the vectors 22 and 23 of Fig. 11 are in phase coincidence, with vectors 24* and 25", respectively, of Fig. 10 and likewise in phase coincidence with vectors 23* and 22, respectively, of Fig. 6.

From the foregoing description, it will be apparent that the corresponding voltages impressedon both the three-phase distributing system and the two-phase distributing system by the two transformer groups are equal in value and in proper phase relationship with one another. As a result, power may be expeditiously transferred from one distributing system to the other distributing system by -means of employing the transformer connections as herein disclosed. While I have explained the phase relationships of the voltage vectors by commencing with the three-phase distributing system, the same conclusions will be reached by commencing with the two-phase distributing system and following the vector transformations of the voltages through the various stages until the voltages are in proper phase relationship to be impressed upon the three-phase distributing system.

From the foregoing description, it will be apparent that my transforming system is particularly adapted to interconnect two power systems which transmit currents of different phases and which are remotely removed from each other. In this instance, the energy transferred between the two systems may be transmitted at high voltages over the high-potential transmission lines comprising the conductors 26, 27 and 28 and the conductors 26, 27 and 28 As a result the transformer windings 29 and 33, and the T-connected windings of the transformers 21 and 32 are insulated for high potentials, inasmuch as these windings constitute the step-up and step-down windings for the high-potential currents flowing over the in terconnecting transmission lines.

The circuit connections of the system illustrated may be varied within the spirit and scope of my invention, and, conse quently, I desire that only such limitations shall be imposed as are indicated in the appended claims.

I claim as my invention:

1. A phase-transforming system having two-phase mains, three-phase mains and a plurality of interconnections therebetween for the interchange of energy, one of said interconnections comprising one pair of primary windings, the first winding being connected across one phase of said twophase system and the second winding being connected across the other phase of said two-phase system, one pair of secondary windings being connected in T relationship and in inductive relation with the aforementioned primary windings, Y-connected windings connected in parallel relationship with said T connection, and a group of delta-connected windings in inductive relationship with the said Y-connected windings and connected to said three-phase mains, and another of said interconnections comprising a second pair of primary windings which are connected to said two-phase system in reverse order of the correspond ing primary windings of said first interconnection, a second-pair of secondary windings connected in T relationship and in inductive relationship with the aforementioned primary windings, delta-connected windings connected in parallel relationship with said second pair of T-connected windings, and a second group of delta-connected windings in inductive relationship with the aforementioned deltaconnected windings and connected to said three-phase mains.

2. A phase-transforming system having two phase mains, three-phase mains and a plurality of interconnections therebetween for the interchange of energy, one of said interconnections comprising a pair of windings that are connected in T relationship, one of the T-connected windings being excited by one phase of said two-phase system, and the other one of the T-connected windings being excited by the other phase of said twophase system, Y-connected windings connected in parallel relationship with said T connection, and a group of delta-connected windings in inductive relation with said Y-connected windings and connected to said three-phase mains, and another of said interconnections comprising a second pair of windings that are connected in T relationship and excited from said two-phase system in reverse order of the corresponding T-connected windings of said first interconnection, delta-connected windings connected in parallel relationship with said second pair of T-connected windings, and a second group of delta-connected windings in inductive relation with the aforementioned delta-connected windings and connected to said three-phase mains.

3. A phase-t'ansforming system having two-phase mains, three-phase mains and a plurality of interconnections therebetween for the interchange of energy, one of said interconnections comprising a pair of windings that are connected in T relationship to generate three-phase voltages, one of the T-connected windings being excited by one phase of said two-phase system, and the other one of the T-connected windings being excited by the other phase of said two-phase system, Y-connected windings connected in parallel relationship with said T connection, and a group of delta-connected windings in inductive relation with said Y-connected windings and connected to said three-phase mains, and another of said interconnections comprising a second pair of windings that are connected in T relationship to generate threephase "oltages and excited from said two-phase system in reverse order of the corresponding T-connected windings of said first interconnection, delta-connected Windings connected in parallel relationship With said second pair of T-connected windings, and a second group of delta-connected Windings in inductive relation with the aforementioned delta-connected windings and connected to said three-phase mains. 10 In testimony whereof, I have hereunto subscribed my name this 26th day of March,

VERN E. ALDEN.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents. Washington, I). O.

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