US1947281A - Transformer - Google Patents

Description

Feb. 13, 1934. u E J, TEMPLE 1,947,281

TRANSFORMER Filed July 6, 1952 3 Sheets Sheet 1 EIT-11erJflervwfzzle by H i s Attorn ey Feb. 13, 1934.

E. J. TEMPLE TRANsFoRMER Filed July 6, 1932 3 Sheetsl Sheet 2 Inventor: Elmer` J.Tem pleJ by @Keek H i S Attorney.

Feb. 13, 1934. E J. TEMPLE 1,947,281

TRAN SFORMER Filed July,r 6. 1932 3 Sheets- Sheet 5 ElmerJTemple, by MM@ His Attorney.

Patented Feb. 13, 1934 PATENT OFFICE TRANSFORMER Elmer J. Temple,

General Electric Company,

New York Pittsfield, Mass., assigner to a corporation of Application July 6, 1932. Serial No. 621,043

Claims.

My invention relates to transformers and more particularly to three phase auto transformers. If the primary and secondary windings of a three phase transformer are both star connected or if both are delta connected, then there is substantially no phase displacement between the prif mary and secondary voltages. If one winding is star connected and the other is delta connected, however, there will be a thirty degree phase displacement between the primary and secondary voltages. If a transformer is to be connected into a system with other transformers, the displacement between its primary and secondary voltages must be such that each voltage is in phase '1 with the voltage of the circuit to which its winding is connected. The general object of the present invention is to provide a three-phase auto transformer having an improved arrangement of windings and connections for operation with either a zero phase displacement or a thirty degree phase displacement between the primary and secondary voltages and with the same ratio Ybetween the two voltages so that the same transformer may be used under conditions requiring either phase displacement.

These and other objects and advantages of the invention will be explained more fully in the following description taken in connection with the accompanying drawings in which Fig. 1 is a view of a three phase transformer having its windings arranged and connected in accordance with the invention with zero phase displacement between the primary and secondary voltages; fFig. 2 is a diagrammatic detail view of the wind- ,ings connected as shown in Fig. 1; Fig. 3 isa vector diagram of the voltages of the windings of Figs. 1 and 2; Fig. 4 is a view similar to Fig. 1 but with the windings connected for thirty degree phase displacement between the primary and secondary voltages; Fig. 5 is a diagrammatic detail view of the windings connected as shown in Fig. 4; Fig. 6 is a vector diagram of the volt- `ages of the windings of Figs. 4 and 5; and Figs. I7 and 8 are further diagrammatic detail views of the windings and connections shown in Figs. 2

and 5 respectively.

Like reference characters indicate similar parts in the different figures of the drawings.

The transformer has a magnetic core 10 with three winding legs 11, 12 and 13. Each winding leg is surrounded by two windings, the leg 11 by the windings 14 and 15, the leg 12 by the windings 16 and 17 and the leg 13 by the windings 18 and 19. One end of each of the windings f14, 16 and 18 is connected to a common neutral 20 which may be grounded so that these windings are star connected. The other end of each of these windings 14, 16 and 18 is connected through one of the windings 15, 17 and 19 to one of the conductors 21, 22 and 23 of a three phase circuit. Each of the windings 14, 16 and 18 has an intermediate tap 24 spaced a few turns below its high voltage terminal. These taps 24 are connected to the conductors 25, 26 and 27 of a second three phase circuit. The parts which have been described thus form a three phase auto transformer connected between the two three-phase circuits.

When the transformer is to be operated with zero phase displacement between its primary and secondary voltages, the two windings on each core leg are connected in series with their voltages accumulative between the neutral 20 and one of the three phase conductors 21, 22 and 23 through connections 28 and 29, as indicated in Figs. 1, 2 and 7. The opening and closing of these 75 `connections may be controlled by switches 30 and 31 respectively as indicate in Fig. 7. The voltages lof the two windings on each core leg are equal and are in phase with each other so that the vector diagram of the voltages of the three pairs of windings is a simple three phase star `diagram as indicated inFig. 3. y

When the transformer is to be operated with a thirty degree phase displacement between its primary and secondary voltages, each of the windings 14, 16 and 18 and one of the windings 15, 17 and 19 which is on another core leg ,are connected in series through one of the connections 32 and each of these pairs of windings is connected between the neutral 20 and one of the conductors 21, 22 and 23 through one of the terminal connections 29, as indicated in Figs. 4, 5 and 8. These connections may be made by moving each of the switches 30 and 31 into its upper position, as indicated in Fig. 8. In order to obtain the proper vector relation between the voltages for both zero and thirty degree phase displacement between the primary and secondary voltages, the windings 14, 16 and 18 are connected to one end of the windings 15, 17 and 19 respectively for the zero phase displacement and to the opposite ends of those windings for the thirty degree phase displacement, the opposite ends of the windings 15, 17 and 19 being connected of course to the conductors 2l, 22 and 23.

When the two windings of each series lconnected pair are on dilerent legs of the core, as indicated in Figs. 4, 5 and 8, their voltages are displaced 60 degrees in phase and the vector sum of the two voltages of each pair of windings is smaller than their arithmetical sum as is apparent from the vector diagram of Fig. 6. When the two windings of each series connected pair are on the same leg of the core as indicated in Figs. 1, 2 and 7, the two voltages are in phase and their vector and arithmetical sums are equal as is apparent from the vector diagram of Fig. 3. The vector sum of the voltages of the two complete windings is therefore greater with the zero phase displacement arrangement than with the thirty degree phase displacement arrangement. In order that the ratio between the primary and secondary voltages may be the same with both arrangements, the windings 15, 17 and 19 are each provided with sections 33 which may be rendered ineffective by means of connections 34. These connections 34 may include switches if desired, as indicated in Figs. '7 and 8. With these switches in their upper positions, as indicated in Fig. 8, the winding sections 33 are connected in series with the remainder of the windings and with the same switches in their downward positions, as indicated in Fig. 7, the sections 33 are ineffective, the number of effective turns between the low voltage terminals 24 and the high voltage terminals being reduced. The cornbined voltage of the two sections 33 of each of the windings 15, 17 and 19 is equal to the difference between the arithmetical and vector voltages of each pair of complete windings when the two windings of each pair are on different legs of the core. Thus, the ratio between the primary and secondary voltages is the same for both the zero and the thirty degree phase displacement arrangement.

In the operation of a power transformer it is often desirable to be able to make small adjustments in the ratio between the primary and secondary voltages. For this purpose, each of the windings 15, 17 and 19 is provided with taps 35 to permit the number of effective turns between the high and low voltage terminals to be varied or adjusted. With the zero phase displacement arrangement indicated by the vector diagram of Fig. 3, the taps 35 alone would permit the adjustment of ratio between primary and secondary voltage without disturbing the phase displacement. However with the thirty degree phase displacement arrangement indicated by the vector diagram of Fig. 6, any adjustment of the connections between the taps 35 would change the phase displacement as well as the ratio between the primary and secondary voltages. Therefore, another set of taps 36 similar to the taps 35 and similarly spaced is provided in each of the windings 14, 16 and 18 between its low voltage terminal 24 and the high voltage end of the winding. Then, by making the same variation or adjustment in each set of taps 35 and 36, the voltage ratio may be varied without disturbing the phase displacement between the primary and secondary voltages. The Voltage ratio of each pair of windings will depend upon the position of the low voltage taps 24 which may be anywhere along their respective windings below the taps 36.

The invention provides a transformer which may be operated with either a zero or a thirty degree phase displacement between its primary and secondary voltages and with the same voltage ratio under either phase displacement condition. Small voltage ratio adjustments may also be made under either condition without changing the voltage phase displacement.

I'he invention has been explained by describing and illustrating a, particular embodiment of the invention but it will be apparent that changes may be made without departing from the spirit of the invention and the scope of the appended claims.

What I claim as new and desire to secure by Letters Patent of the United States is:

l. An auto transformer including three magnetic core winding legs, a winding on each of said legs, one end of each of said windings being connected to a common neutral, a low voltage terminal connected to an intermediate point of each of said windings, a second winding on each of said legs, and means for connecting each winding of said second set of windings in series with either of two windings of said first set, said means being arranged to connect one end of each winding of the second set to the winding of the first set on the same core leg with their voltages accumulative or to connect the other end of each winding of the second set to a winding of the first set on another core leg, each winding of one of said sets having taps for reducing the number of ef- F fective turns therein when connected in series with a winding of the other set on the same core leg.

2. An auto transformer including three magnetic core winding legs, a winding on each of said legs, one end of each of said windings being connected to a common neutral, a low voltage terminal connected to an intermediate point of each of said windings, a second winding on each of said legs, and means for connecting each winding of y.; said second set of windings in series with either of two windings of said rst set, said means being arranged to connect one end of each winding of the second set to the Winding of the first set on the same core leg with their voltages accumulative or to connect the other end of each winding of the second set to a winding of the rst set on another core leg, each winding of one of said sets having taps for reducing the vector voltage when connected in series with the winding of the otherV set on the same core leg to the value of the vector voltage when connected in series with a winding of the other set on a different core leg.

3. An auto transformer including three magnetic core winding legs, a winding on each of said,M legs, one end of each of said windings being con- 1`25 nected to a common neutral, a low voltage terminal connected to an intermediate point of each of said windings, a second winding on each of said legs, and means for connecting each winding.. of said first set of windings in series with a winding of said second set on a different core leg with their voltages displaced 60 degrees, each winding of each of said sets being provided with voltage regulating taps, and said taps for the windings, of said first set being provided between their respective low voltage terminals and their high voltage ends.

4. An auto transformer including three magnetic core winding legs, a winding on each of said legs, one end of each of said windings being connected to a common neutral, a low voltage terminal connected to an intermediate point of each of said windings, a second winding on each of said legs, and means for connecting each winding of said first set of windings in series with a windli ing of said second set on a different core leg with their voltages displaced 60 degrees, each winding of each of said sets being provided with voltage regulating taps, said taps for the windings of said first set being provided between their respective low voltage terminals and their high voltage ends, and the taps in the two windings of each series connected pair of windings being similarly spaced to permit equal voltage adjustments in both windings.

5. An auto transformer including three magnetic core winding legs, a winding on each of said legs, one end of each of said windings being connected to a common neutral, a low voltage terminal connected to an intermediate point of each of said windings, a second winding on each of said legs, and means for connecting each winding of said second set of windings in series with either of two windings of said first set, said means being arranged to connect one end of each winding of the second set to the winding of the rst set on the same core leg with their voltages accumulative or to connect the other end of each winding of the second set to a winding of the rst set on another core leg, each winding of said second set of windings having taps for reducing the vector voltage when connected in series with a winding of said rst set on the same core leg to the value of the vector voltage when connected in series with a winding of said first set on a diierent core leg, each winding of each of said sets being provided with voltage regulating taps, said taps for the windings of said first set being provided between their respective low voltage terminals and their high voltage ends, and the voltage regulating taps in the two windings of each series connected pair of windings being similarly spaced to permit equal voltage adjustments in both windings.

ELMER J. TEMPLE.

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