US3467931A - Continuous disk winding and integral radial coil connector for electric transformer and the like - Google Patents

Description

Sept. 16, 1969 J. c. DUTTON 3,467,931

CONTINUOUS DISK WINDING AND INTEGRAL RADIAL COIL CONNECTOR FOR ELECTRIC TRANSFORMER AND THE LIKE Filed Sept. 23, 1966 2 Sheets-Sheet 1 FROM STE/P SUPPL RL Sept. 16, 1969 J. c. DUTTON 3,467,931

CONTINUOUS DISK WINDING AND INTEGRAL RADIAL COIL CONNECTOR FOR ELECTRIC TRANSFORMER AND THE LIKE Filed Sept. 23, 1966 2 Sheets-Sheet 2 l //v VE/V TOR. I

JoH/v C. urro/v In /p0 144M ATTORNEY United States Patent 3,467,931 CONTINUOUS DISK WINDING AND INTEGRAL RADIAL COIL CONNECTOR FOR ELECTRIC TRANSFORMER AND THE LIKE John C. Dutton, Rome, Ga., assignor to General Electric Company, a corporation of New York Filed Sept. 23, 1966, Ser. No. 581,525 Int. Cl. H01f 27/30 US. Cl. 336-180 6 Claims ABSTRACT OF THE DISCLOSURE A transformer winding comprising a plurality of axially adjacent disk coils wound from one continuous band or strip of wide, thin electric conductor. Each coil is spirally upwound and radial cross connectors between radially offset winding turns are formed integrally with the coils by forming in the strip material a series of flat angularly disposed folds and intermediate perpendicular bends.

The present invention relates to inductive windings for electric transformers and the like, and more particularly to windings formed of one or more spirally wound disktype coils wherein radially offset turns of the same or of adjacent coils are electrically connected in contiguous series circuit relation.

In inductors carrying heavy currents, special conductors must be employed to prevent excess heating due to the passage of current through the conductors in the inductor windings. One type of high current conductor commonly employed is of rectangular cross-section approaching a square, i.e., having a low width-to-thickness ratio of the order of unity. This type of relatively thick conductor is used to form concentrically Wound disk type coils, a number of which are usually found on a common core or mandrel in axially spaced relation. Each disk coil is formed from one or more strands of conductor material, and is spirally wound upon itself beginning at the surface of a suitable reel or mandrel, usually formed as a cylinder of insulating material. The process of winding a 'disk coil from the reel radially outward is known in the art as upwinding.

In prior art inductors, axially adjacent upwound coils have been connected in series by cutting the coil conductor at the inner and outer ends of each coil and connecting a special crossover conductor from the outermost turn of one coil to the innermost turn of an adjacent coil. Such special crossover conductors have previously been formed separately of relatively wide thin material, because the usual coil conductor of low width-to-thickness ratio is too thick to use in the small space between axially adjacent coils. These axial spaces between coils act as ducts to conduct cooling fluid radially, so they must not be unduly obstructed. Also, if spacing between the coils and crossover is too small, insulation problems arise. Such separate crossover connections, however, must be brazed at each end, so that manufacture is costly and the additional connections increase coil resistance and the possibility of failure. 1

i It is one object of the present invention to obviate the need for separate crossover conductors between radially offset turns of disk type coils.

It is a more particular object of the present invention to provide an inductive winding having axially adjacent upwound coils with integral crossover connectors extending between the outermost turn of one coil and the innermost turn of the next adjacent coil.

It is a still further object of the present invention to provide an inductor having integral coil crossover connectors which may be fabricated during a continuous winding process.

It is still another object of the present invention to provide an inductive winding of the upwound disk type having integral coil crossover connectors which occupy a minimum axial distance in the space between adjacent coils.

In carrying out my invention in one preferred embodiment, I upwind a plurality of disk-type coils from a flat strip conductor having a relatively large width-tothickness ratio. This wide, thin coil conductor is itself utilized to form integral crossover connectors. By forming a combination of flat angular folds and intermediate perpendicular bends, a connecting section of the coil conductor is radially offset to provide an integral cross connector between electrically contiguous turns of the same or axially adjacent upwound coils.

By forming disk-type coils of strip material which is wide relative to its thickness, there is provided a large conductor cross section for any predetermined conductor thickness. The resulting high current capacity of the coils requires an axial spacing (for cooling) which is large relative to conductor thickness, so that the integral radially disposed cross connection does not unduly obstruct the inter-coil duct.

While this specification concludes with claims particularly pointing out and distinctly claiming my invention in its essential aspects, the objects and advantages of the invention will be more fully understood by referring now to the following detailed description taken in conjunction with the accompanying drawings in which:

FIGURE 1 is a perspective view of an inductive winding constructed in accordance with the teachings of the present invention;

, FIGURE 2 is a plan view of a segment of a conductive strip having fold lines which allow the fabrication of an integral coil crossover connector in accordance with the teachings of the present invention;

FIGURE 3 is an enlarged perspective view of a coil connector fabricated in accordance with the teachings of the present invention;

FIGURE 4 is a perspective view of one coil of an inductor showing means for holding the coil strands in position;

FIGURE 5 is a schematic diagram showing the use of the present invention for transposing the strands in a multistrand disk-type winding;

FIGURE 6 is an enlarged perspective view of a coil connector used for transposing strands;

FIGURES 7 and 8 are diagrammatic illustrations of partially interlaced coils using my invention, and

FIGURE 9 is a fragmentary perspective view of a re-entrant cross connector for the interlaced coil of FIG. URE 8.

Referring now to FIGURE 1, there is shown an inductive winding disposed upon a tubular support or core member 10 of insulating material and comprising a plurality of axially spaced coils 11-16 of the upwound disktype. The winding is fabricated by winding the coils from relatively wide flat strip material, starting with coil 11 and finishing with coil 16. The winding of coil 11 is begun at the radially inner end adjacent the core member 10 after bringing out a terminal end or lead 17 shown extending parallel to the insulating core member. It will be evident to those skilled in the art that the tubular core member 10 may in final assembly be disposed on a rectilinear core of magnetizable material (not shown).

The coil conductor is a relatively wide, thin band of strip material having a large width-to-thickness ratio as compared with rectangular conductorsnow commonly used to wind disk-type coils. Preferably the thin conductor strip or band is formed of extruded aluminum or copper having a width of several inches and a thickness the order of 30 to 300 mils. For example, I have Wound a satisfactory experimental multicoil winding of conductor 75 mils thick and two inches wide. Such a band of strip material must be suitably insulated, such as by a coating of insulating enamel or paper.

After the terminal end 17 is secured to the insulating core member 10, the core member is rotated so that the strip conductor is continuously wound on itself to radially build up, or upwind, the multi-turn coil 11. When the desired number of turns has been wound, a crossover connector 18 is formed at the end of the outermost turn of coil 11. The coil crossover connector 18, which is described in greater detail in the following paragraphs, is shaped to bring the band of strip of material to a new radially inset position on the surface of core member where it is parallel to and spaced axially from the turns of the coil 11. The conductor band or strip at the new position forms the beginning of coil 12. The winding process is then repeated until the desired number of turns has been wound for coil 12. A coil crossover connector 19, identical to the connector 18, is formed at the end of coil 12 so as to bring the strip back to the core member surface. The above-described winding process is repeated for coils 13-16 with the crossover sections 20, 21 and 22 being formed to provide electrical connections be tween coils 13, 14, and 16. Upon completing the coil 16, the conductor strip may be again folded as shown and brought out along the surface of core member 10 to form a terminal lead 23.

An inductive winding such as that shown in FIGURE 1 may serve as the high or low voltage winding in a transformer. It is especially useful as a low voltage winding because of the high current-carrying capacity which can be provided in the wide, fiat conductor. To provide symmetry and balance in the winding, the cross connectors 18-22 are preferably staggered around the periphery of the winding. Although FIGURE 1 shows the coil connectors 18-22 offset about only part of the coil periphery, this is for purposes of illustration only. In a preferred embodiment of the invention, the coil connectors 18-22 would be distributed about the full periphery of the winding.

FIGURE 2 shows a portion 24 of my coil conductor strip upon which is illustrated, by dotted lines, lines along which the material may be folded in order to form the coil crossover connector of the present invention. Starting at the left end of the coil strip 24, a first end 25 would be at the end of the outermost turn of a completed coil. The end 25 terminates at a fold line 26 which lies at an angle of 45 degrees to the side edges 27 and 28 of the strip. A pair of parallel bending lines 29 and 30, perpendicular to the edges 27 and 28, define an intermediate portion 31 which constitutes the radially offset part of the finished connector. At the right of the strip there is another 45 degree fold line 32 extending parallel to the fold line 26. The perpendicular bend line and the 45 degree fold line 32 define two of the edges of a trapezoidal portion 33 just as the perpendicular bend line 29 and the 45 degree fold line 26 define a trapezoidal portion 34. The area of the strip to the right of the fold line 32 is a second end 35 of the strip portion 24. When the segment 24 is folded, the end 35 constitutes the beginning of the innermost turn of a new coil which is parallel to but axially spaced from the completed coil. The axial spacing or offset of the coils is determined by the sum of the distance A (measured along the strip from the perpendicular fold line 29 to the nearest end of the degree fold line 26) and the distance B (measured along the strip from the perpendicular fold line 30 to the nearest end of the 45 degree fold line 32).

The blank shown in FIGURE 2 is shaped into the desired coil connector shown in FIGURE 3 in the following manner. Once the outermost turn of the completed coil with the end 25 is secured to the subjacent turn of the coil, the strip is folded upon itself along the 45 degree line 26 until the trapezoidal portion 34 overlies part of the end 25. A hydraulic or hand press may be used to flatten the trapezoidal portion 34 against the end 25. The bending continues in the same direction at the perpendicular fold line 29 until the intermediate radial offset portion 31 is at right angles to the end 25 that extends radially inwardly. This bend causes the intermediate portion 31 to extend along the side edges of the completed coil turns. Thestrip is then bent degrees in the opposite directions at the perpendicular fold line 30, so that the trapezoidal portion 33 rests on the reel surfaces with its side edges at right angles to the side edges of the strips in the completed coil. To complete the coil connector, the strip is folded upon itself along the 45 degree fold line 32 so that the end 35 extends in the same direction as the end 25 of the completed coil. The axial distance, or the distance along the reel surface, between the adjacent coils is determined by the sum of the distances A and B as is shown in FIGURE 3. When the new coil has been completely wound, this bending process is repeated, bringing the strip from the outer layer of the newly completed coil back to the reel surface.

The end 25 of the outermost coil turn may be secured to the subjacent turn by taping or cementing it. Alterriatively, the arrangement shown in FIGURE 4 may be utilized. A coil 36 shown there is wound on a reel 42 between the arms of U-shaped spacers 37 having their bight portions resting against the reel surface. The U- shaped spacers serve as guides during the winding process of lining up the side edges of the coil turns.. To secure the outermost turn of the coil, there are provided additional U-shaped spacers 38 which are inverted relative to the spacers 37. That is, the bight portion of each of the inverted spacers 38 rests on the outermost turn of the coil and its arms extend inwardly along the sides of the coil to the reel surface. The inverted spacers 38 may be secured to the reel surface by any suitable means.

The above-described coil connector may also be used to transpose strands in a multi-strand conductor strip. Such multi-strand strips are used in windings which are to carry extremely heavy currents. By using relatively thin strands to make up each strip, the desired crosssectional area of the conductor may be obtained without incurring the eddy current losses which would occur in a single strand strip having the same cross-sectional area. The relative positions of the strands in each strip should be altered so that each strand links the same amount of flux. This equal flux linkage produces the same voltage in each strand so that there are no circulating currents between strands.

FIGURE 5 shows diagrammatically a transposition arrangement for a Winding made from a three-strand strip. For purposes of simplicity, each coil is shown as having only three multistrand turns, each of which is made up of bands or strips A, B, and C. In the left-hand group 39 of the coils, the strands are in the same position relative to one another, i.e., strand A is at the top of each turn, whereas strand C is at the bottom so that the strip has an ABC configuration. In the adjacent or middle group 40, however, strand A is moved from the top to the bottom of each coil turn, whereas strand B occupies the top position and strand C the intermediate position to form a turn having an BCA configuration. This transposition is brought about by altering the connection pattern between the right-hand coil in group 39 and the left-hand coil in group 40.

FIGURE 6 is a perspective view of a strand-transposing cross connection of the type illustrated at FIGURE 5 between the coil groups 39 and 40. The cross connector for the strand A is formed first to bring strand A from the outside of the top turn of the completed coil down against the reel surface. Then the connector for the innermost strand C is formed. Strand B, the intermediate strand in the completed coil, is extended past the connector for the strand C before its own connector is formed. In the new coil, strand B is at the outside whereas strand A is at the inside of each coil turn. Each of the coils in group 40 of FIGURE 5 is wound with this arrangement of strands. The strands ABC may .-,be similarly transposed between the right-hand coil in the group 40 and the lefthand coil in group 41 of FIGURE 5.

Although FIGURE 5 shows three coil groups 39, 40 and 41 having three identical coils each, it is not necessary to group the coils in any particular way so long as each strand occupies the same position the same number of tirn'esas each of the other strands. For example, the first coil in a group of three coils c ould be provided with an ABC strand configuration, the second coil with a BCA configuration, and the third with a CAB configuration.

It will now be evident to those skilled in the art that my improved coil conductor and integral flat crossover connector may be utilized not only to interconnect entire coils, but may be used also to provide the internal cross connections characteristic of so-called interlaced coils. Coil interlacing of one type is described, for example, in Patent 2,453,552-Stearns, and is illustrated diagrammatically at FIGURE 7 forming, part of my present specification. At FIGURE 7, I have shown three upwound coils with the first two coils at the left side interlaced and the third coil directly stacked, the coil turns being connected electrically in series in the order indicated by the numbers on the turns. ,It will be evident that the coil cross connectors shown may all be formed in the manner previously described.

In addition, it is known to interlace disk coils in a manner such that at least some of the internal cross connectors are re-entrant into the same coil, as illustrated in the single interlaced coil shown diagrammatically at FIGURE 8. In that figure the intercoil cross connector 50 may be formed as previously described, while the reentrant cross connector 51 is formed without axial offset, such as illustrated in perspective at FIGURE 9. The reentrant strip of FIGURE 9 is formed by folding along 45 degree and 90 degree lines in somewhat the manner shown at FIGURE 2, but with the 45 degree end folds made along mutually perpendicular, rather than parallel, 45 degree lines.

While there has been described what I now consider to be a preferred embodiment of the persent invention, it is apparent that modifications and variations may occur to those skilled in the .art. Therefore, it is intended that the appended claims shall cover all such modifications and variations as fall within the true spirit and scope of the invention.

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

1. In an inductive winding for electric transformers or the like, a linear core member, at least two spirally wound disk coils concentrically mounted on said core in axial spaced relation, each said coil comprising a plurality of radially superposed turns formed of a thin band of wide electrically conductive strip material, and an integral crossover connector extending substantially radially along the edges of said turns between said coils to connect in continuous series circuit relation a pair of radially offset turns of said winding, said connector being formed by folding said band of strip material upon itself at two spaced-apart points along fold lines acutely angularly disposed with respect to the axis of said band and bending the band substantially at right angles at two intermediate points along lines substantially perpendicular to said axis.

2. A Winding according to claim 1 wherein said radially offset turns are in a single disk coil and said acutely angularly disposed fold lines are mutually perpendicular and said band of strip material is bent in the same direction at said intermediate points, whereby said crossover connector is re-entrant in respect to said single coil.

3. A winding according to claim 1 wherein said radially offset turns are in adjacent axially offset coils and said acutely angularly displaced fold lines are mutually parallel so that said crossover connector extends axially between said coils and radially between said turns.

4. A Winding according to claim 1 including at least two axially adjacent upwound coils and wherein said crossover connector extends from the outermost turn of one coil to the innermost turn of the other.

5. A winding according to claim 1 including at least two axially adjacent upwound coils and wherein said angularly disposed fold lines are mutually parallel and at substantially 45 degrees to the axis of said band of strip material, said band being bent in opposite directions at said intermediate points, whereby said crossover connector extends axially of said winding between said coils and radially between said turns.

6. An inductive winding according to claim 1 wherein said radially olfset turns are in adjacent axially offset coils and each is formed of a plurality of superposed bands of strip material, each said band being folded and bent to form a separate crossover connector and said connectors being positioned to transpose the relative positions of said bands in passing between said coils.

References Cited UNITED STATES PATENTS 3,008,107 11/1961 Stearn 336 3,188,591 6/1965 Dortort et al. 336 3,371,300 2/1968 Stein 336187 X FOREIGN PATENTS 22,313 8/1930 Netherlands. 256,158 12/ 1927 Italy.

WARREN E. RAY, Primary Examiner US. Cl. X.R. 336-187, 232

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