US2484576A

US2484576A - Interphase winding and ratio adjuster switching arrangement for polyphase transformers

Info

Publication number: US2484576A
Application number: US657694A
Authority: US
Inventors: Minneci Salvatore
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1946-03-28
Filing date: 1946-03-28
Publication date: 1949-10-11
Anticipated expiration: 1966-10-11

Description

INTERPHASE WINDING AND RATIO ADJUSTER SWITCHING ARRANGEMENT FOR POLYPHASE TRANSFORMERS Filed March 28, 1946 OctQll, 1949. I I s. MlNNECl 2,484,576

Inventor: Sa\vat owe Minnec His Abtorx ey.

patented Oct. 11, 1949 IN TERPHASE WINDING AND RATIO AD- JUSTER SWITCHING ARRANGEMENT FOR POLYPHASE TRANSFORMERS Salvatore Minneci, Pittsfield, Mass., assignor to General Electric Company, a corporation of New York Application March 28, 1946, Serial No. 657,694

7 Claims. 1

My invention relates to improvements in rotatable interphase winding and ratio adjuster switching mechanism for polyphase transformers and more particularly to an improved rotatable delta-Wye and ratio adjuster switching arrangement for three-phase transformers.

In order to facilitate the changing of transformer connections during the heating cycle of an electric furnace, it has been customary to provide two rotatable ratio adjusters per phase. In the usual arrangement, one ratio adjuster is used to change the transformer winding and reactor connections and the other adjuster to change the phase connections from delta to wye and vice versa. positions, a total of six eight-point ratio adjusters is required. Up to certain voltages, this is feasible although the space required is large. In view of the demand for more tap changing positions and. the practice of mounting the switches under oil in the transformer casing, the space requirements become excessive and the old arrangement expanded to meet these needs is not practical. Thus, in the old arrangement, four of the eight stationary contact rods of each adjuster had to be connected together to form a common electrical point. Now, if more than four operating positions are required, the use of the necessary additional contact rods just to form the common point increases the over-all size and cost of the adjusters, and it becomes impractical to mount the adjusters under oil in the transformer casing. Also, with higher voltages, the old arrangement becomes impractical. Furthermore, in the old arrangement, it was necessary to move all the adjusters simultaneously for each change, that is, whenever a tap change, a phase connection change or both were required. This simultaneous movement of so many switches, especially when motor driven, increases wear and also control power requirements.

An object of my invention is to provide, for polyphase transformers, an improved rotatable interphase winding and ratio adjuster switching mechanism which is not only compact, economical and applicable up to relatively high voltages but also provides a uniform continuity of successive steps between adjacent switching positions in a predetermined recurrent sequence upon successive revolutions of the switching mechanism. Another object of my invention is to provide such a switching mechanism which has maximum flexibility in the choice of ratio adjusting positions relatively to the different interphase connections. A further object of my invention is to Thus, for four tap changing provide an improved form of alternate deltawye switching mechanism which, for minimum space requirements, can coordinate effectively with a ratio adjuster having a maximum of ratio adjusting positions. A still further object of my invention is to provide such a switching mechanism wherein the control power requirements are minimized. These and other objects of my invention will appear in more detail hereinafter.

In accordance with my invention, I provide, for polyphase transformers, a combination interphase winding and ratio adjusted switching mechanism comprising a ratio adjuster switch for each phase winding of the transformer hav ing a series of adjacent equiangular switching positions in each revolution thereof and an improved interphase winding switch which has a double series of equiangular and alternate switching positions in each revolution thereof and includes a Geneva gear and a driver therefor arranged to actuate the gear intermittently. Also, I provide means for simultaneously rotating at the same angular speed the ratio adjuster switches and the driver. Further in accordance with my invention, the interphase winding switch comprises n (n being an integer greater than 1 and usually equal to 3), equally spaced bridging contact members movable with the Geneva gear and Zn pairs of equally spaced stationary contacts. For effecting engagement of the n movable contacts first with n alternate pairs of stationary contacts and then with the other n alternate pairs of stationary contacts, I provide, on the driver, suitable driving means, the number and spacing of which determine the continuity of engagement of the movabie contacts with the two sets of n pairs of alternate stationary contacts. Also, in order to obtain the greatest flexibility in the various combinations of interphase operating positions, the effective diameter of the driver is relatively larger in comparison with the effective diameter of the Geneva gear.

My invention will be better understood from the following description when considered in connection with the accompanying drawing, and its scope will be pointed out in the appended claims.

In the accompanying drawing, Fig. 1 illustrates a switching arrangement embodying my invention and Fig. 2 is a part detail of a modification of my invention.

In Fig. 1 I have schematically and diagrammatically illustrated a combination interphase winding and ratio adjuster switching arrangement which embodies my invention as applied to a three-phase transformer comprising twopart high voltage windings ii, 22' and 33 with intermediate current limiting reactors 4, and 6, respectively, all as frequently used in electric furnace operation. For simplicity, I have not shown the low voltage windings, which are connected to the furnace, since these output windings are not essential to an understanding of my invention. As shown, each of the transformer winding parts i, 2 and 3 "and their respectively associated reactors 4, 5 and 6 is provided with the necessary number of taps, six taps a, b, c, d, e and f being shown for the purpose of illustrating my invention. Also, corresponding taps on the transformer windings and their respectively associated reactors are designated by the same letter. The phase conductors of a power line, to which the transformer windings i, 2 and 3 are connected, are represented by the short lines I, 8 and S.

For ratio adjusting purposes, I provide three ratio adjustin or tap changing switches l0, fl and i2, examples of which are well known to the art. As far as my invention is concerned the particular type of ratio adjusting switch is immaterial except that the switch have a series of adjacent equiangular switching positions in each revolution thereof. Thus, if no reactor is involved, the switch may be of the so-cailed star type having a common movable contact which is arranged to engage equally spaced circularly arranged stationary contacts. However, as shown, each of these switches comprises a rotatably mounted contact controlling element i3 and six equally spaced switching points such as six pairs of stationary contacts a, b, c, d and f corresponding to the taps a, b, c, d, e and f on the respectively associated transformer windings and their reactors and suitably connected thereto as shown. The six pairs of points on each ratio adjuster are arranged to be connected by a suitably insulated contact l4 mounted on and movable with the element I3. Thus, in the :t position shown in the drawing, the movable contact i4 through the stationary contacts a connects the a taps of the transformer wi; ling and its respectively associated reactor and for six consecutive 60 of clockwise rotation, indicated by the curved arrow E5, the tap connections are carried through the a, b, c, d, e, 1 cycle. For simultaneous rotation, the contact controlling elements 53 are suitably secured to a shaft, indicated by the dash-dot line l6.

For controlling the interphase connections of the transformer windings 2 and 3 and their respectively associated reactors 4, 5 and 6 so as to provide different predetermined ranges or numbers of tap connections for a given interphase connection or connections. I provide an interphase winding switch :1. As shown, this switch comprises a Geneva gear it having six teeth corresponding to the total number of positions of the interphase winding switch 11 and a Geneva driver l9 therefor. The driver is is rigidly associated with a shaft 20 indicated in part by a dash-dot line. The gear [8 is mounted on a parallel shaft, indicated by the dash-dot line 26'. For actuating the gear l8 intermittently and in accordance with a desired continuity, the driver I9 is provided with suitable riving means such as one or more pins 2| and 22 which are engageable with the teeth of the Geneva gear 18 to efiect rotation thereof intermittently in accordance with the number of pins and the spacing thereof. In the illustrated embodiment of my invention, the pins 2| are apart. Preferably the effective diameter of the driver i9 is relatively large in comparison with the effective diameter of the gear it since this increases the flexibility in the various combinations of operating positions, especially for different numbers of tap ratio positions.

For controlling the interphase or delta and wye connections of the transformer windings l'|, 2-2', 3'3 and the reactors 4, 5 and 6 by the movement of the driver l9 and the gear it, I provide, in accordance with my invention, it equiangularly spaced contact members 23, 24 and 25 which are carried on the rotor 32 and are thus movable by and with the gear l8 to control in the arrangement shown 2n equiangularly spaced pairs of

stationary contacts

26, 27, 28, 29, 3D and 39. The spacing and arrangement of the movable and stationary contacts is such that the movable contacts 23, 24 and 25 first engage 11 alternate pairs of

stationary contacts

26, 28 and 30 and then the other 11 alternate pairs of stationary contacts 2?, 29 and 3!. For actuating the movable contacts, they are mounted on a rotor 32 which is of suitable insulating material and which is rotatable with the gear [8. For this purpose, the rotor 32 is indicated as mounted on the shaft 20'. The order in which the n movable contacts engage n alternate equiangularly spaced pairs of stationary contacts of course differs with the angular position of the rotor 32, but this is immaterial since the movable contacts 23, 24 and 25 are of the equiangularly spaced bridging type.

For the Wye-connection, the inside contacts of the three alternate pairs of

stationary contacts

26, 28 and 30 are interconnected by a conductor 33 and the outside contacts of these pairs provide Wye-connection terminals that are respectively connected to the transformer part winding 3', 2 and i by

conductors

34, 35 and 36. For the deltaconnection, the inside contacts of the three alternate pairs of stationary contacts 21, 29 and 3| provide delta connection terminals that are respectively connected to the transformer part windings 3, 2 and i by conductors 37, 32 and 39. Also, the outside contacts of the three alternate pairs of contacts 23 and 3E are respectively connected to the transformer part windings 2', I and 3 by the conductors 35, 33 and 34 and consequently are interconnected with the outside contacts of the alternate pairs of stationary contacts 23, 2B, 35). Thus with the three equiangularly spaced bridging contacts 23, 24, 25 carried radially on the rotor 32 into bridging engagement with the six equiangnlarly spaced pairs of

sta tionary contacts

21, 28, 29, and 38 there are obtained three alternate delta and Wye switching positions in each revolution of the rotor 32 since the six equiangulerly spaced pairs of stationary contacts are alternately bridged in triad by the bridging contacts in each of three positions.

For simultaneously actuating the contact controlling members !3 of the ratio adjusters l0, 1! and I2 and also the Geneva driver IS! in equal angular successive steps, I have shown a motive means such as an electric motor 49 which is arranged to drive a shaft 4| through a suitable speed reducer'42. As shown, the drive shaft 4| is coupled to each of the shafts 1-6 and 20 by a 5. bevel pinion 43 and a bevel gear 44, the drive ratio being the same in each case. The arrangement is such that each time the motor 40 is energized each of the shafts I6 and is turned through a step of 60. Thus, each time the motor 40 operates, the circuit controlling members I3 of the ratio adjusting switches IO, N and I2 are moved clockwise from one tap position to another and the driver I9 is turned 60, but the continuity of the existing deltaor wye-connection established by the interphase winding switch I! will depend on the position, number and spacing of the driving pins 2i and 22 on the driver l9.

Assuming now the parts positioned as shown in the drawing, then the transformer windings and their associated reactors are wye-connected on the aa' tap position. If now the motor 40 is energized long enough to turn the shaft 4| in the direction indicated by the arrow 45, so that the shafts I6 and 20 are turned 60 in the direction indicated by the arrows 55, then the circuit controlling members I3 of the ratio adjusters l0, II and 12 will be moved simultaneously to the b-b tap position. The wye-connection remains unchanged, however, since the driving pin 22 on the driver H] has turned clockwise only 60 which is not enough to turn the gear [8. When the motor 40 is energized the second time, the circuit controlling members |3 are moved to the tap position cc. This time the driving pin 22 engages the gear l8 and turns it and the rotor 32 60 in the direction indicated by the arrow 46, thus moving the contacts 23, 24 and 25 into engagement with the alternate stationary pairs of contacts 21, 29 and 3!, respectively, to effect a change from the wye-connection to the deltaconnection. When the motor 40 is energized the third and fourth times, the circuit controlling members l3 are moved to the tap positions (1-11 and e--e, but the rotor 32 is not moved since neither of the driving pins 2| and 22 has moved far enough to engage the gear |8. When the motor 40 is energized for the fifth time, the circuit controlling members l3 are moved to the jtap position. Also, the driving pin 2| engages the gear l8 and thus turns the rotor 32 in the direction indicated by the arrow 46 to bring the movable contacts 23, 24 and 25 into engagement with the alternate pairs of stationary contacts 28, and 26, respectively, thereby return- Interphase Tap Position Connection From an analysis of the foregoing, it' will at once be apparent to those skilled in the art that, if the driving pins 2| and 22 are spaced 120 (smaller angle) and the driver |9 is moved 60 each time, then ther will be four consecutive 6 delta-connected tap positions" and two consecu tive wye-connected tap posiitons depending on the initial setting of the driving pins 2| and 22 relatively to the movable contacts 23, 24 and 25 and the alternate pairs of stationary contacts 26-3|. Also, if the two driving pins 2| and 22 are spaced 60 (smaller angle) and are moved. 60 each time, then there will be five consecutive delta-connected tap positions and one wye-connected tap position or vice versa.

It will also be aparent to those skilled in the art that, if only one driving pin is used, the range of tap positions may be accomplished first with. a deltaor wye-connection for all positions and. second with a wyeor delta-connection for all positions.

If eight tap positions are desired instead of six, then an eight position ratio adjuster is used and instead of turning each of the shafts I6 and 20, 60 for each change in tap position, they are turned 45. Also, as shown in Fig. 2, the pins 2| and 22 on the driver It! are spaced 180 apart and, as shown, a line joining these pins is at an angle of 22 to the horizontal. The Geneva gear I8 is assumed to be in the wye position shown in Fig. 1 although it could just as well be in the delta position. Obviously the driver l9 can be rotated in the direction indicated by the arrow into three different positions before the pin 22' enters the notch in the gear I8. This makes a total of four wye-connected tap positions. When the driver I9 is turned another 45, in the direction indicated by the arrow, however, the gear It is engaged by the pin 22' and turned counterclockwise 60 into the delta-connected position. Also for three more tap positions the delta-connected position will be maintained. On the next 45 clockwise movement of the driver l9,

the pin 2| engages the gear I8 and turns it into' the wye-connected position.

From the foregoing it will be apparent to those skilled in the art that if the pins 2| and 22 are spaced 135, five wye and three delta positions or vice versa can he obtained. Also, if the pins 2| and 22' are spaced 90 then ix wye and two delta positions or vice versa can be obtained.

From the foregoing and particularly Fig. 2, it will be apparent that if only four tap positions are required a four position ratio adjuster is used and two pins 2| and 22 spaced as in Fig. 2

but turned 90 each time will provide two delta and two Wye positions. Also, if pins 2| and 22' are spaced 90 and turned 90 each time, then three deltaand one wye positions or vice versa can be obtained.

In all of the foregoing, it is assumed that the cycles of wye and delta connected positions and tap positions are completed in one revolution of the shafts 20 and i6 respectively.

It is to be noted that with interphase winding and ratio adjuster switching mechanisms embodying my invention, there is no need for reversing the motor 40 or any reversing controls since all switching operations are on a basis of continuous rotation in the same direction.

While I have shown and described my inven' tion in considerable detail, I do not desire to be limited to the exact arrangements shown, but seek to cover in the appended claims all those modifications that fall within the true spirit and scope of my invention.

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

1. An interphase and ratio adjusted sequential switch mechanism having in combination, a plurality of rotating ratio adjuster switches, each having a predetermined even number of successive equiangular switching positions in each revolution thereof, a rotating interphase switch having a succession of equiangular and alternate switching positions in each revolution thereof, a symmetrical Geneva gear having a number of teeth equal to the total number of positions of said interphase switch and a driver therefor, said gear having connections, with the interphase switch to rotate said switch between the adjacent alternate switching positions thereof during a part of the angular movement of said driver equal to the angular movement of said ratio adjuster switche between adjacent switching positions, and means for simultaneously rotating said ratio adjuster switches and said driver in equal annular successive steps to provide a recurrentswitching sequence upon successive revolutions thereof.

2. A delta-wye and ratio adjuster sequential switch mechanism having in combination, three rotating ratio adjuster switches, each having an even number of successive equiangular switching positions in each revolution thereof, a rotating delta-wye switch having three equiangular and alternate delta and Wye switching positions in each revolution thereof, a symmetrical Geneva gear having six teeth and a driver therefor, said gear having connections with the delta-wye switch to rotate said switch between said alternate delta-wye switching positions thereof during a part of the angular movement of said driver equal to the angular movement of said ratio adjuster switch between adjacent switching posi tions, and means for simultaneously rotating said ratio adjuster switches and said driver in equal angular successive steps to provide a recurrent switching sequence upon successive revolutions thereof.

3. A delta-wye sequence switch comprising a rotor having three equiangularly spaced bridging contacts carried thereby, six equiangularly spaced pairs of stationary contacts alternately bridged in triad by said bridging contacts, alternate pairs of said stationary contacts each having one .con tact thereof providing a wye connection terminal and the other contacts thereof electrically connected together to establish the wye neutral and the other pairs of said stationary contacts providing delta interconnection terminals, and means for rotating said rotor including a Geneva gear having six teeth.

4. A delta-wye sequence switch having in combination a rotor having three equiangularly spaced radial bridging contacts carried thereby, six pairs of equiangularly spaced stationary contacts with each pair in radial alignment for bridging engagement with each of said bridging contacts, alternate pairs of said stationary contacts having one contact thereof electrically interconnected together to establish a wye neutral and the other contact thereof electrically'connected wit-h one contact of an adjacent pair of stationary contacts.

5. A delta-wye sequence switch comprising a rotor having three equiangularl spaced radially extending bridging contacts carried thereby, six equiangularly spaced pairs of stationary contacts in radial alignment for alternate bridging engagement in triad with said bridging contacts, alternate pairs of said stationary contacts providing delta interconnection terminals and theother pairs of said stationary contacts each having one contact thereof providing a wye connection terminal and the other contacts thereof interconnected together to establish the wye neutral, and means for rotating said rotor including a symmetrical Geneva gear having six teeth, a driver for actuating said gear intermittently, and having an effective diameter materially larger than the effective diameter of said ear.

6. A delta-wye sequence switch comprising a rotor having three radial bridging contacts spaced apart on said rotor, six pairs of stationary contacts spaced 60 apart with the contacts of each pair in radial alignment for engagement with each of said bridging contacts, alternate pairs of said stationary contacts providing delta interconnection terminals and the other pairs of i said stationary contacts each having one contact together to establish the wye neutral, means for intermittently rotating said rotor including 8. Geneva gear having six teeth, a driver for said gear having a diameter materially larger than the effective diameter of said gear, two driving pins spaced 186 apart on said driver for engagement with said gear to efiect and maintain simultaneous engagement of said bridging contacts in triad with alternate pairs of said stationary contacts while said driver is turned. and to effect and maintain simultaneous engagement of said bridging contacts in triad with the other alternate pairs of said stationary contacts while said driver is turned through another 180.

7. In an interphase winding and ratio adjuster sequential switch mechanism for an n phase transformer, a rotatable ratio adjuster switch for connection with each phase winding of the transformer and having a series of switching positions in each revolution thereof to provide a corresponding number of transformation ratios, an interpha-se winding switch comprising a rotor having it equiangularly spaced bridging contacts carried by said rotor, two n pairs of equiangularly spaced stationar cooperating contacts having one of each alternate pair of contacts electrically connected together and the other contacts eachv lutions of said driver, and means for rotatin said ratioadjuster switches and said driver at equiangular speeds in steps corresponding to the number of said transformation ratios and thereby provide a recurrent ratio adjuster and interphase winding switching sequence.

SALVATORE MINNECI.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,640,325 Janson Aug. 23, 1927 2,020,941 Guhl Nov. 12, 1935