US2910663A

US2910663A - Transformer core clamp connector

Info

Publication number: US2910663A
Application number: US478318A
Authority: US
Inventors: Stanley H Wilk; Edward D O'neil
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1954-12-29
Filing date: 1954-12-29
Publication date: 1959-10-27
Anticipated expiration: 1976-10-27

Description

Oct. 27, 1959 s. H. WILK ET AL TRANSFORMER coma CLAMP CONNECTOR 2 Sheets-Sheet 1 Filed Dec. 29, 1954 a m 5W am a 1 v WH U E IIIIIIIIIIII Ill... n I n z m 2m 4 161W I H F. O 0 Q J 0 ,MM m H 1. E, T W o mgfi fillr l 'l l ld-HI PI IH I I IH I0} 4 WM 0 0 0 Q J m M f l lvlhlllll lliw easwwaeooo W .71! it Oct. 27, 1959 s. H. WILK ET AL TRANSFORMER CORE CLAMP CONNECTOR 2 Sheets-Sheet 2 Filed Dec. 29, 1954 Edwarc/D. OYYeil,

flaw 9 72,4

United States Patent TRANSFORMER CORE CLAMP CONNECTOR Stanley H. Wilk and Edward D. ONeil, Pittsfield, Mass, assignors to General Electric Company, a corporation of New York Application December 29, 1954, Serial No. 478,318

4 Claims. (Cl. 336-410) This invention relates to stationary electrical induction apparatus and more in particular to an improved core clamp connector for power transformers.

Power transformer cores are generally comprised of a plurality of vertical leg sections formed of stacked laminations of magnetic material whose ends are joined by horizontal yoke sections also formed of stacked laminations of magnetic material. In the past these cores have been clamped together by various means. In one type of clamping means, channel shaped members are placed adjacent to each side of the yoke laminations, and bolts extending through the clamps and yoke hold the core laminations firmly together. In this type, vertical stresses are sometimes present in the leg laminations due to short circuit forces or lifting forces, since in this case the leg members act as a tie between the clamps. In a second form of clamp, tie rods are provided extending between the top and bottom clamps external to the windings to remove these vertical stresses from the laminations. These outside connections have proved to be undesirable, however, especially in high voltage and large transformers. In order to eliminate tie rods and stresses in leg laminations, a third type of clamp employs tie plates located inside of the windings and adjacent to each side of each core leg. The ends of the tie plates are connected to the bottom and top channel members by means of bolts extending through the core clamps and into the tie plates.

In the latter type of core clamp, the vertical stresses applied to the core are absorbed by the bolts holding the tie plates and channel members together. In order that each bolt carry its share of any existing stresses, the holes through the tie plates must be accurately positioned. It has been the practice in the fabrication of such cores, to first assemble the tie plates and drilled channel members on a flat surface to accurately locate the positions of the holes to be drilled in the tie plates. The clamp parts are then disassembled and the holes drilled and tapped in the tie plates. Then a bottom channel member and its associated tie plates are reassembled on a flat surface, and the leg and bottom yoke members stacked in place on top of the clamp members. The other bottom channel members and associated tie members are placed on top of the stacked laminations, and the entire assembly is accurately aligned to provide the proper distances between the legs and right angles between the leg members and the bottom yoke. This assembly is then bolted together and raised to an upright position. Since the final assembly of the cores generally occurs at another location in the shop, the cores are then transported by means of slings extending around the bottom yokes to a final assembly area. The final assembly consists of placing windings over the legs, assembling the top yoke in position, and clamping the top channel members in place. The assembly of the transformer core having external-tie rods is similar to the above described method, with the excep- 'tion that no preassembly is required.

2,916,563 Patented Oct. 27, 1959 Although it may be possible to use a jig or template to locate the holes in the tie plates and thereby eliminate the previously mentioned preassembly step, such a jig introduces additional complications into the assembly. Due to the thinness of the tie plate, a number of smaller bolts are usually required in order to carry the load, since one large bolt would not engage sutficient threads in the tie plate. The number of bolts varies in different transformers, and the position of the bolts may also vary in different transformers. Similarly the length of the tie plates also varies. With such a jig then, the holes would have to be accurately aligned with respect to each other, and the holes in the clamp members would have to correspond exactly with the holes in the tie plates. This would result in the necessity for a relatively complicated jig for each transformer type, and also a necessity for accurately aligning the jig so that the holes in the tie plates correspond to the holes in the clamp members. From a practical standpoint this method has not been found to be suitable.

It has been found that the previously described core clamps have several inherent disadvantages. As previously stated, it is undesirable to have tie rods located outside of the windings. ln the construction of these types of cores a considerable amount of time is required to accurately align the legs and yokes prior to clamping them in position. It has also been difiicult to transport the cores to a final assembly area. An excessive amount of space is required for the fabrication of the bolted tie plate type of core due to the initial assembly that must be made, and the preassembly for accurately locating the tie plate holes has been found to be time consuming and costly. The first type of clamp also has the disadvantage of requiring a bolt hole through the corners of the core laminations.

These difliculties have been overcome in the present invention by employing tie plates similar to those previously described, but having buttons welded on their ends instead of holes previously drilled and tapped therein. The buttons may be accurately positioned without preassembly by means of a simple jig. The buttons fit into corresponding holes in the channel members. Proper alignment of the core members is thereby assured, and it is merely necessary to establish a right angle between one leg and the yoke. As will be described later, the buttons also provide for a convenient method of transporting the cores to a final assembly area.

It is therefore an object of this invention to provide an improved core clamp connectorfor transformers.

It is also an object to provide an improved core clamp connector for transformers eliminating the necessity for tie rods external to the windings between the yoke clamps.

A further object of this invention is to provide a core clamp connector for transformers wherein tie plates internal to the windings are connected to end clamps on the transformer core to remove stresses from the core laminations and wherein a minimum amount of time and elfort is required to fabricate the cores, and a minimum number of holes are required through the core laminations.

A still further objectof this invention is to provide buttons on the'ends of tie plates in a transformer core clamp connector wherein the buttons engage holes in the end clamps of the core to prevent lifting and short circuit forces from being induced in the transformer core and to provide an improved method for fabrication of the cores.

This invention will be better understood from the following description taken in connection with the accompanying drawings and its scope will be pointed out in the appended claims.

In the drawings,

Fig. 1 is a partly broken away side view of a power transformer core illustrating one embodiment of the core clamp connector of this invention;

Fig. 2 is an end view, partly in section, of the transformer core of Fig. 1;

Fig. 3 is a partially exploded view of one end of the transformer core of Fig. 1;

Fig. 4 is a side View of one form of the core clamp connector of this invention, and

Fig. 5 is a perspective view of a top corner of a partially assembled transformer core illustrating a modification of the core clamp connector of this invention.

Referring now to the drawings, and more particularly to Figs. 1, 2, and 3, a power transformer core is therein illustrated having three

leg sections

10, 11 and 12 joined by a bottom yoke section 13 and a top yoke section 14. The core sections are formed from stacked laminations of a magnetic material. These core sections may have a cruciform cross section (as illustrated in Fig. 3), and they may also be provided with ducts 16 and 17 extending therethrough. The duct 16 completely separates the front half of the core from the back half of the core for the purpose of circulation of a cooling fluid, and the proper spacing between the core halves is provided by means of spacers 18. The duct 17 extends through the core at right angles to the duct 16, and provides improved magnetic characteristics for the core, as well as providing for coolant fluid circulation and simplifying the construction of the core. The core may also have mitre-joints as illustrated, although any other type of joint, such as a butt lap joint may be used without departing from the scope of this invention. Similarly any other core cross section configuration may also be employed with the core clamp connector of this invention.

For clarity, windings 19, 20, and 21 are shown in phantom in position on

legs

10, 11, and 12 respectively.

In order to hold the core laminations firmly together, tie plates 22 are placed on each side of the leg laminations, bottom clamp members 23 are placed on each side of the bottom yoke member 13, and top clamp members 24 are placed on each side of the top yoke member 14. The tie plates and top and bottom clamp members are clamped to the core by means of a plurality of bolts 25 extending through the yokes and legs. In the fully split type of core as illustrated, the bolts may pass through the ducts Additional clamping action may be provided by bolts 26 passing through the ends of the

clamp members

23 and 24. The top and bottom clamp members may be any shape giving the necessary strength, such as a channel shape as illustrated in the bottom clamp 23, or an angle shape as illustrated in the top clamp 24. The'clamp members may also have reinforcing members 27 Welded thereto for additional strength, and plates 28 may be positioned between the ends of the clamp members for the same purpose.

To facilitate lifting of the transformer, the upper yoke clamps are provided with a plurality of lifting lugs 29. When a transformer is lifted, unless mechanical linkages are provided between the bottom and top braces, the leg laminations will be subject to the lifting stresses. Similarly, short circuit forces acting on the windings may cause stresses in leg laminations'if they are notabsorbed by other means. These stresses are'remoVed-in the present invention by means of buttons 30 welded to the ends of the tie plates 22. Holes 31 corresponding to the buttons 353 are provided in the

clamp members

23 and 24. For additional mechanical strength of the clamp member holes 31, drilled plates 32 may be welded on the sides of the clamp members. 7

A plurality of spacing blocks 33-are positioned between the sides of the yoke laminations and the top and bottom clamp members in order to provide space for fl id Gib culation around the core. v

tions, tie plates, and clamp members.

the top clamp members.

When a winding is placed over the core leg, it is of course necessary that no part of the core leg-have a Width greater than that of the winding cylinder. This factor limits the maximum length of the top button. Referring now to Fig. 4, the top button 40 is shorter than the lower button 30 in order to provide clearance for the Winding cylinder. Due to the decreased length of the top button 40, however, it may be desirable to weld this button from the back of the tie plate, so that the full length of the button may be used as a bearing surface without interference from the weld.

Since the spacing blocks 33 (Figs. 1 and 3) are generally of a standard width, and may be of sufiicient width that the hole 31 in the top clamp member 24 does not fully engage the button, it may be necessary to weld the drilled reinforcing plates 32 on the inner sides of the top clamp members. v

In the modification of core clamp connector illustrated in Fig. 5, the top clamp member 24 and reinforcing plate 32 are held firmly against the tie plate 22 by means of a bolt extending into a tapped hole in the top button 40. The bolt 50 is provided with a washer 51 or block engaging theclamp member. The advantages of this modification will be described later, and it is to be noted that in Fig. 5 the yoke laminations are not in place.

In the assembly of a transformer core according to this invention, the buttons are Welded onto the tie plates by means of a spacing jig, and accurately located corresponding holes are drilled in the clamp members. The jig may be very simple, since it is only necessary to accurately establish the center line. distances between the buttons. The tie plates and clamp members of one side of the transformer are then assembled on a flat surface, and the leg and bottom laminations stacked on the top thereof. Then the tie plates and clamp members for the other side of the core are placed on top of the stacked laminations. Since the top clamp members are in place, the proper distance between the leg members is provided, and it is only necessary to establish a right angle relationship between the bottom yoke member and one leg.

Having been properly aligned, the core is then clamped together, by means of bolts extending through the lamina- If the core is of the split type, all of these bolts may go through the ducts extending through the core. Then the entire assembly is placed in an upright position. Although it is not necessary at this time that the top clamp member be bolted in place, it may be desirable, as illustrated in Fig. 5 to hold the top clamp member in position by means of bolts extending into tapped holes in the top buttons. Since the top clamp members are mounted in position, transporting the core assembly to a final assembly area may be accomplished by means of the lifting lugs 29 in The final assembly consists of removing the top clamp members, placing windings over the legs, assembling the top yoke members in place, replacing the top clamp members, and clamping thetop yoke in place by means of bolts extending through the laminations. Replacement of the top clamp members is simplified by drawing them into place by means ofthe bolts 50. V

The core clamp connector of this invention may be used on solid core transformers as well as split core transformers, and the core may have mit-re joints, butt lap joints, or any other types of joints. In the c'aseof the fully split transformer cores, no holes are required through the laminations for clamping purposes. In the case of solid transformer cores, no extra holes are required through the core for holding the tie plates and clamp members together.

While it is preferred that the buttons be welded on the tie plates, this invention also contemplates the weldcorresponding holes in the tie plates. In such a case reinforcing plates should be welded to the tie plates.

From the foregoing description, it is seen that this invention provides a transformer core requiring no holes through the laminations for absorbing short circuit and lifting forces. A minimum of space, effort, and time is required to construct the core, and improved means are provided for transporting thecore. The alignment of the core is simplified, and no tie rods are required outside of the windings. The core is readily adaptable to mass production techniques.

It will be understood, of course, that, while the forms of the invention herein shown and described constitute preferred embodiments of the invention, it is not intended herein to illustrate all of the possible equivalent forms or ramifications of the invention. It will also be understood that the words used are words of description rather than of limitation, and that various changes may be made without departing from the spirit and scope of the invention herein disclosed.

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

1. A transformer core comprising a plurality of leg sections formed of stacked laminations of a magnetic material, a plurality of yoke sections also formed of stacked laminations of a magnetic material and joining the ends of said leg sections, elongated end clamp members extending parallel to said yoke members clamping said yoke sections, elongated tie plate members extending parallel to said leg members clamping said leg sections, joints between said clamp members and tie plate members a plurality of cylindrical buttons, one of said buttons being rigidly afiixed to one of said members at each joint of said clamp members and tie plate members and extending perpendicular to said core, said buttons extending through corresponding holes in the other of said members at each of said joints.

2. A transformer core comprising a plurality of leg sections formed of stacked laminations of a magnetic material, a plurality of yoke sections also formed of stacked laminations of a magnetic material and joining the ends of said leg sections, an elongated clamp member extending in parallel relationship on each side of each yoke section and clamped thereto by means of bolts extending through said yoke sections, an elongated tie plate member extending in parallel relationship on each side of each leg section and clamped thereto by means of bolts extending through said leg sections, joints between said clamp members and tie plate members, a plurality of cylindrical buttons, one of said buttons being rigidly aflixed to one of said members at each joint of said clamp members and said tie plate members and extending perpendicular to said core, said buttons extending through corresponding holes in the other of said members at each of said joints.

3. A transformer core comprising a plurality of leg members formed of stacked laminations of a magnetic material, a plurality of yoke members formed of stacked laminations of a magnetic material and joining the ends of said leg members, elongated tie plates mounted adjacent the sides of said leg members in parallel relation thereto and being clamped thereto by means of bolts extending through said leg members, a cylindrical button rigidly afiixed to each end of each of said tie plates and extending outwardly from said leg members, clamping members extending parallel to said yoke members and being clamped rigidly in respect thereto by means of bolts passing through said yoke members, and holes in said clamping members into which said buttons extend.

4. A transformer core comprising a plurality of leg members formed of stacked laminations of a magnetic material, a plurality of yoke members formed of stacked laminations of a magnetic material and joining the ends of said leg members, elongated tie plates mounted adjacent the sides of said leg members in parallel relation thereto and being clamped thereto by means of bolts extending through said leg members, a first cylindrical button afiixed to the top end of each of said tie plates and extending outwardly from said leg members, a second cylindrical button affixed to the bottom end of each of said tie plates and extending outwardly from said leg members, said first buttons having lengths permitting a winding to be placed over them and onto the respective leg members, clamping members extending parallel to said yoke members and being clamped rigidly in respect thereto by means of bolts passing through said yoke members, and holes in said clamping members into which said first and second buttons extend.

References Cited in the file of this patent UNITED STATES PATENTS 2,083,354 Whittier June 8, 1937 2,328,228 Pearson Aug. 31, 1943 2,655,622 Besag et al. Oct. 13, 1953 2,702,375 Johnson Feb. 15, 1955 FOREIGN PATENTS 668,990 Great Britain Mar. 26, 1952 862,032 Germany Jan. 8, 1953