US3691495A

US3691495A - Non-shorting winding connection for tap changer on series-multiple transformer

Info

Publication number: US3691495A
Application number: US206726A
Authority: US
Inventors: Gerard V Conway
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1971-12-10
Filing date: 1971-12-10
Publication date: 1972-09-12
Anticipated expiration: 1989-09-12

Abstract

A tap changer winding connection for a series-multiple transformer. One of the windings is provided with a plurality of continuous turns equal to the multiple or parallel voltage of the transformer. The winding is also provided with a plurality of tap connections. A second winding portion, discontinuous from the first winding is also provided having a plurality of tap connections. One or more other windings are provided also having sufficient continuous turns equal to the multiple or parallel voltage of the transformer. A series-multiple switch is provided for connecting the windings in series or in parallel. When connected in parallel, the winding having the tap connections is connected in parallel with all of the continuous turns equal to the parallel voltage connected, thus effectively disconnecting the tap changer from the parallel connected windings.

Description

United States Patent Conway [541 NON-SHORTING WINDING CONNECTION FOR TAP CHANGER ON SERIES-MULTIPLE TRANSFORMER [72] Inventor: Gerard V. Conway, Pittsfield, Mass.

[73] Assignee: General Electric Company [22] Filed: Dec. 10, 1971 [21] Appl. No.: 206,726

[ 51 Sept. 12, 1972 Primary Examiner-Thomas J. Kozma Attorney-Francis X. Doyle et a1.

[5 7] ABSTRACT A tap changer winding connection for a series-multiple transformer. One of the windings is provided with a plurality of continuous turns equal to the multiple or parallel voltage of the transformer. The winding is also provided with a plurality of tap connections. A second winding portion, discontinuous from the first winding is also provided having a plurality of tap connections. One or more other windings are provided also having sufficient continuous turns equal to the multiple or parallel voltage of the transformer. A seriesmultip1e switch is provided for connecting the windings in series or in parallel. When connected in parallel, the winding having the tap connections is connected in parallel with all of the continuous turns equal to the parallel voltage connected, thus effectively disconnecting the tap changer from the parallel connected windings.

4 Claims, 8 Drawing Figures PATENTEDSEP 12 m2 SHEET 1 OF 2 fmfwfir, 56mm V ['om/ NON-SHORTING WINDING CONNECTION FOR TAP CHANGER ON SERIES-MULTIPLE TRANSFORMER BACKGROUND OF THE INVENTION This invention relates to series-multiple transformers and more particularly to a non-shorting winding connection for use with tap changers in series-multiple transformers.

As is well known to those skilled in the transformer art, it is common practice to provide transformers which have a dual voltage rating. In general, the term dual voltage rating is applied to transformers which are provided with a low voltage setting and a high voltage setting for the high voltage winding. It may be that more than two different voltage ratings are provided such as, for example, a plurality of high voltage ratings and a single low voltage rating. However, the transformers are designated as dual voltage rating transformers and it will be understood that the term dual voltage rated transformer or similar phrases used throughout the specification and claims will relate to transformers which are provided with a high voltage rating and a low voltage rating although there may be more than one high voltage rating for such transformers. In general, the dual voltage of the dual voltage rated transformer is provided by means of a multiple primary winding which may be connected in either series or in parallel to provide the desiredvoltage ratings for the transformer. For example, a transformer may be provided with a plurality of 2,400 volt windings. When these windings are connected in parallel, the voltage rating of the transformer will be 2,400 volts. However, when the windings are connected in series, the transformer will have a voltage rating according to the number of 2,400 volt windings which are provided in the transformer. For example, when three windings are provided, the voltage rating would be 7,200 volts. As

- will be apparent by use of a series-parallel switch,

which is generally referred to in the art as a series-multiple switch and will be so designated throughout the specification and claims, the rating of the transformer can be changed from either the low voltage or the high voltage rating, as desired.

In many instances, utilities have required that their dual voltage transformers be provided with a variable series high voltage rating. in other words, many utilities require that their dual voltage rated transformers be provided with a high voltage series rating which may vary over a specified range. For example, one such transformer may have a low voltage multiple rating of 2,400 volts and be provided with a high voltage series rating of, for example, 8,000 volts, 7,810 volts or some other similar rating. Utilities require the plurality of high voltage series ratings because in many instances utilities have different areas where different high voltage rating requirements are found. In order to minimize the various types of transformers which utilities are required to stock, they generally require that a single transformer be available which will be useful for any of their high voltage rating requirements.

In order to provide the desired dual voltage rating transformers with a plurality of high voltage series ratings, it is necessary that either a series-multiple switch having more than two positions be provided, that is, one that has two separate high voltage series positions, or else that a tap changer be provided for use with the high voltage series rating. As will be readily understood, a special series-multiple switch provided with a plurality of high voltage series settings is a necessarily expensive switch. Therefore, in order to limit the cost of dual voltage rating transformers, it is preferred to utilize a tap changer to vary the high voltage rating. However, with the use of a tap changer, a special problem arises that the tap changer may be used when the series-multiple switch is in the multiple voltage position. When this occurs in transformers of the prior art, one of the parallel windings will be at an incorrect voltage rating; this would induce a short circuit condition in a transformer causing damage and possible destruction of the transformer. Thus, it is desirable to provide a dual voltage transformer of low cost having a variable high voltage series rating without danger of incorrectly connecting the winding of the transformer when in the low voltage multiple setting.

This has been done in the prior art by providing an interlocking means between the series-multiple switch and the tap changer such that the tap changer is placed in the correct position and locked when the series-multiple switch is placed in the parallel or multiple operating position. As will be understood, an interlocking device adds extra expense to the series-multiple transformer and also adds another mechanical device which must be maintained during the life of the transformer. It has long been considered desirable to provide a series-multiple transformer having a tap changer for the series connection wherein the tap changer is automatically removed from the multiple connection without using mechanical interlocks or the like.

It is, therefore, one object of this invention to provide a relatively low cost, dual voltage transformer having a variable high voltage series rating.

Another object of this invention isto provide a dual voltage transformer in which the variable high voltage series rating is provided by means of a tap changer.

Yet another object of this invention is to provide a dual voltage transformer using a tap changer to vary the high voltage series setting of the transformer and in which the tap changer is only operative when the series-multiple switch is in its high voltage series operating position.

A still further object of this invention is to provide a dual voltage transformer in which a tap changer is used to vary the high voltage series rating of the transformer and in which the tap connections are provided such that in the multiple or parallel operation of the transformer, the tap changer is out of operative circuit relation with the tapped winding.

SUMMARY OF THE INVENTION In carrying out this invention in one form, a transformer is provided having a dual voltage rating and having a series-multiple switch for placing the transformer in either a low voltage multiple or a high voltage series mode of operation. A tap changer is provided such that the high voltage series rating of the transformer may be varied by varying the position of the tap changer to vary the number of turns in the series connected winding of the transformer. The tap positions of the windings are so connected that when placed in the multiple or parallel operation the tap changer is removed from the circuit.

The features of the invention which are believed to be patentable are set forth with particularity in the appended claims. However, it is believed that this invention and the manner in which its objects and advantages are obtained as well as other objects and advantages thereof will be better understood by reference to the following detailed description of a preferred embodiment thereof, especially when considered in connection with the accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a schematic diagram of one form of the primary windings of a series-multiple transformer according to this invention;

FIG. 2 is a schematic diagram of the windings of FIG. 1 connected for multiple or parallel operation;

FIG. 2a is a diagrammatic showing of one form of series-multiple switch showing the switch in the multiple position;

FIG. 3 is a schematic diagram of the winding of FIG. 1 connected for series operation;

FIG. 3a is a diagrammatic showing of a series-multiple switch in the series position;

FIG. 4 is a schematic diagram of a slightly different form of series-multiple winding using this invention; and

FIGS. 4a and 4b are diagrammatic showing of a series-multiple switch for use with a winding of FIG. 4 showing the multiple position and the series position, respectively.

DESCRIPTION OF PREFERRED EMBODIMENT As above noted, this invention relates to a seriesmultiple transformer winding provided with taps wherein the taps are provided on one winding such that when the windings are placed in multiple or parallel operation, the tap changer is effectively out of the circuit. Reference will now be made to the drawings for a detailed description of a preferred embodiment of this invention. When referring to the drawings, like numerals will be used to indicate like parts throughout the various figures.

Referring first to FIG. 1, there is shown schematically a multiple winding 10 for use in a series-multiple transformer, not otherwise shown. As shown, the multiple winding 10 includes a first winding 12 having

terminals

1 and 2, a second winding 14 having

terminals

3, 4, 5 and 6 and a third winding 16 having

terminals

7 and 8.

For purposes of this description, the series-multiple windings 10 will be considered as a 2,400 volt by 8,000 volt winding and the windings as having 10 volts per turn. Winding 12 is indicated as having 240 turns between

terminals

1 and 2 and thus being a 2,400 volt winding between the terminals. Winding 14 is indicated as having 42 turns between

terminals

5 and 3; 240 turns between

terminals

3 and 4; and 38 turns between

terminals

6 and 6b. As will be understood, this will provide 2,400 volts between

terminals

3 and 4. In like manner, winding 16 is indicated as having 240 turns and thus 2,400 volts between

terminals

7 and 8. When windings l2, l4 and 16 are connected in multiple or parallel as is shown in FIG. 2, there will be three 2,400 volt windings connected in parallel.

As shown, winding 14 is provided with a tap changer 20 with contact arm 22 connectible to

taps

4, 4a and 4b, while contact arm 24 is connectible to

taps

6, 6a and 6b. As can be seen, tap 4 on winding 14 is also terminal 4 of the winding 14. Therefore, when a connection is made to terminal 4 by the series-multiple switch 30, as shown in FIG. 2a, tap changer 20 is effectively removed from the circuit regardless of its position. As can be seen from FIG. 2, with

terminals

1, 3 and 7 connected together and

terminals

2, 4, and 8 connected together, the

windings

12 and 16 of 2,400 volts each are connected in parallel with each other and with the portion of winding 14 between

terminals

3 and 4 which also provides 2,400 volts. As can be seen from FIG. 2, no matter how tap changer 20 is positioned it will not affect the volts between the

terminals

3 and 4. Thus the windings may be placed in parallel operation without regard to the position of tap changer 20.

FIG. 3 shows the windings l2, l4 and 16 connected in series for high voltage operation with the tap changer 20 in circuit. FIG. 3a shows the position of a series-multiple switch 30 to provide the high voltage operation. As shown, terminal 1 is connected to the high voltage bushing, terminal 2 is connected to terminal 5, terminal 6 is connected to terminal 7, the tap changer 20 is connected between the tap contacts 4 and tap contacts 6, and terminal 8, the other side of winding 10, is connected to ground. As will be apparent, if all of the turns of

windings

12, 14 and 16 are in series and there are 10 volts per turn throughout the winding, the total voltage across the winding 10 will be 8,000 volts. However, as shown in FIG. 3, tap changer 20 has contact arm 22 on tap 4b and contact arm 24 on tap 6. As can be seen, this eliminates four sections of winding 14, each section being indicated as having 19 turns. Thus, 760 volts have been dropped leaving a total voltage across winding 10 of 7,240 volts. Obviously, as tap changer 20 is moved to include in each of the sections of winding 14 the voltage will increase first to 7,430 volts, then 7,620 volts, then 7,810 volts and, finally, when all sections are in, 8,000 volts across the winding 10. From the above, it will be apparent that by means of placing the taps for the high voltage series setting on portions of the main winding and on additional portions of a second winding wherein one of the taps is actually one of the terminals, then the connecting of the windings in parallel in the manner shown particularly in FIG. 2, will effectively remove the tap changer from the circuit without any need for an interlock or any need for placing the tap changer on a given set of contacts.

FIG. 4 shows a similar winding 10' having three sections, section 32 between

terminals

1 and 2, section 34 including

terminals

3, 5, 4 and 6 and section 36 between

terminals

7 and 8, wherein the winding 10 may be connected in either series or multiple. Again considering the winding as being one in which there are ten volts per turn then, as can be seen, winding 32 with 240 turns will have a voltage of 2,400 volts between

terminals

1 and 2. Winding 34 having 240 turns between

terminals

3 and 4 will also provide 2,400 volts between these terminals and, in a similar manner, winding 36 having 240 turns will provide 2,400 volts between

terminals

7 and 8. Thus, when the windings are connected in parallel in the manner shown by the switch 30 in FIG. 4a with

terminals

1, 3 and 7 connected together and

terminals

2, 4 and 8 connected together, the three windings are connected in parallel,

each winding having 2,400 volts thereacross. As can be seen in FIG. 4, winding 34 is provided with a tap changer 20 having the arm 22 engageable with

contacts

4, 4a and 4b while arm 24 is engageable with the

taps

6, 6a and 6b. As is indicated in FIG. 4, between

terminals

3 and 5 there are 36 turns or, therefore, 360 volts, while between the

taps

4 and 4a, 4a and 4b, 6b and 6a, and 6a and 6, it is indicated as being 18 turns and therefore 180 volts between taps. As will be understood, since between

terminals

3 and 4, there are 240 turns and thus 2,400 volts, then when the windings are connected in parallel in the manner above discussed, the tap changer 20 is out of circuit. Therefore, there is no need, either to provide an interlock, or to place tap changer 20 in a special position before connecting the series-multiple switch 30 in multiple, as shown in FIG. 4a.

Winding shown in FIG. 4 is connected in series in the manner shown by switch 30 in FIG. 4b, that is, terminals 2 to 3 and terminal 6 to 7. Then as will be understood, the total number of turns between terminals 1 and terminal 8 of winding 10' is 756 turns. Therefore, the total voltage for the series connection may be 7,560 volts between terminals 1 and terminal 8. However, in the manner shown in FIG. 4, with contact arm 22 on tap 4a and contact arm 24 on tap 6a the sections 4 to 4a and 6a to 6b of winding 34 are out of circuit. Therefore, 36 turns have been dropped and thus the voltage across the

terminals

1 and 8 will be 7,200 volts. Of course, as will be apparent from FIG. 4, by moving the tap changer the voltage for the series connection may be varied from 6,840 volts in steps of 180 volts to 7,020 volts to 7,200 volts to 7,380 volts and finally to 7,560 volts. Thus the tap changer may be effective, for example, considering the winding 10 shown in FIG. 4 of a 2,400 volt by 7,200 volt transformer, then the connection may be effective to have plus or minus taps to either increase or decrease the nominal high voltage of the transformer.

Of course, it will be apparent from FIG. 4, that the series connection may be made from terminal 2 to terminal 5 and terminal 6 to 7, providing a different series high voltage. With that series connection, the 36 turns between

terminals

3 and 5 are necessarily eliminated making the maximum high voltage 7,200 volts. As the tap changer 20 is used to eliminate the various sections of the winding 34, the high voltage will drop in 180 volt steps from 7,200 volts, to 7,020 volts, 6,840 volts, 6,660 volts, and finally to 6,480 volts. Thus, by using different terminals to connect winding 10 in series, the high voltage may be varied from the top and the bottom of the range, although the value of each step of tap changer 20 remains the same.

Thus, as will be understood, the invention may be utilized in any series-multiple transformer of any desired rating and by means of placing the taps such that one of the taps is one of the terminals of a winding wherein the winding between the terminals is of the desired multiple ratio, then a transformer may be provided having any desired high voltage ratio wherein the multiple ratio will be determined by the voltage across the windings in parallel.

While there has been shown and described the present preferred embodiment of the invention, it will of cou e be u ders ood that vario u chan es ma be made without eparting from the spirit and s%:ope o the invention. The invention which is sought to be protected is set forth in the appended claims.

What is claimed as new and which it is desired to secure by Letters Patent of the United States is:

l. A series-multiple voltage transformer having a series-multiple switch and a tap changer, a plurality of windings connectible in series or multiple according to the position of said series-multiple switch, one of said windings including two portions, each of said portions having a plurality of taps, said tap changer being connectible between said plurality of taps on each of said portions, one of said portions having at least two terminals, the winding portion between said two terminals having a voltage equal to the multiplevoltage of the transformer, whereby when said plurality of windings are connected in multiple, said tap changer is inoperative.

2. A series-multiple transformer having a series-multiple switch and a tap changer, a plurality of windings connectible in series or multiple according to the position of said series-multiple switch, one of said windings including two portions, each of said portions having a plurality of taps, said tap changer connected between said plurality of taps on each of said portions, one of said portions having at least two terminals, one of said terminals being one of said plurality of taps on said portion, the winding portion between said two terminals having a voltage equal to the multiple voltage rating of the transformer, placing said series-multiple switch in multiple position connecting said winding portion between said two terminals in multiple connection with the other of said plurality of windings thereby making said tap changer inoperative.

3. A series-multiple voltage transformer having a series-multiple switch and a tap changer, a plurality of windings connectible in series or multiple according to the position of said series-multiple switch, one of said windings including two portions, each of said portions having a plurality of taps, said tap changer being connectible between said plurality of taps on each of said portions, one of said portions having at least two terminals, the winding portion between said two terminals having a voltage equal to the multiple voltage of the transformer, one of said two terminals being one of said plurality of taps on said one portion, said other plurality of windings having end terminals with the winding between said end terminals being equal to the multiple voltage of the transformer, said series-multiple switch in multiple position connecting each of said two terminals with one of said end terminals of each of said other plurality of windings to place said plurality of windings in multiple and remove said tap changer from operation.

4. A series-multiple transformer as set forth in claim 3 in which said other portion of said one winding has a terminal and in which said series-multiple switch in series connects one of said end terminals of one of said other plurality of windings to one of said two terminals of said one portion and connects one of said end terminals of another of said other plurality of windings to said terminal on said other portion of said one winding, thereby placing said tap changer in operation.

Claims

1. A series-multiple voltage transformer having a seriesmultiple switch and a tap changer, a plurality of windings connectible in series or multiple according to the position of said series-multiple switch, one of said windings including two portions, each of said portions having a plurality of taps, said tap changer being connectible between said plurality of taps on each of said portions, one of said portions having at least two terminals, the winding portion between said two terminals having a voltage equal to the multiple voltage of the transformer, whereby when said plurality of windings are connected in multiple, said tap changer is inoperative.