US1960033A - Transformer construction and method of making the same - Google Patents

Description

May 22, 1934., F s SMH-'H 1,960,033

TRANSFORMER CONSTRUCTION AND METHOD OF' MAKING THE SAME BY ATTQRNEYS 04W# MVM lMay 22, 1%34. v s SMH-H 1960,033

TRANSFORMER CONSTRUCTION AND METHOD 0F MAKING THE SAME Fild Dec. 5, 1931 2 Sheets-Sheet 2 b 2f l 4 0 /3 22a, /8 2/3 sNvENToR :ff 'M BY ATTORNEY5 @far-44m Patented May 22, l934 hill D STATESv rarest' orries ETRANSFRBER C N S T E U C T E O N AND ll/ETHGD 0F MAKING THE SAME 11 Claims.

This invention relates to transformer construction, and more particularly to a nigh volt age transformer construction.

One of the objects of this invention to provide a transformer which is compact in form, rugged in construction, and efficient in operau tion. Another object is to provide a transformer construction which is economical to produce and simple and rapid to manufacture. Another object of this inventlon is to provide a transformer of the. above-mentioned character which is well adapted to function at high potentials and in which the possibility of internal breakdown is greatly reduced without saorice of other important advantages. Another object is to provide a transformer construction in which high insulation is achieved with the use of a minimum amount of insulating material and more particularly to provide a winding construction in which effective insulation and particularly graded in sulation may be achieved in inexpensive, and thoroughly dependable Way, Another object is to provide a transformer winding construction adapted to function high voltages in which highly efficient use is made of the availm able winding space in order thus to minimize thr` length oi the magnetic circuit and thus to achieve better linkage, better regulation, and higher eiicienc-y. Other objects will be in part obvious or in part pointed out hereinafter.

The invention accordingly consists the features of construction, comi inations of elements, arrangements of parts and in several steps and relation and order of each of the saine to one or more of the others, all will be illustratively described herein, and the scope of the application of which will indicated in vthe following claims.

ln the accom drawings, in which is shown one of the various possible embodiments of my invention,

Figure i is a vertical central sectional View cfa completely nbledtransforrner;

Figure 2 is an enlarged fragmentary sectional view of the windings shown in Figure l;

Figure 3 an isometric view, partly in section, of one of the coil spacers of Figures l and 2, and

Figure l is a horizontal central sectional View of the transformer but on a reduced scale, certain parts boing omitted, showing how the core is tted with the casing.

Similar reference characters refer to similar parts throughout the several views in the drawings.

Referring to the drawings and more particularly to Figure 1, first provide a container 10, preferably in the form of a cylindrical steel tank capable of withstanding appreciable pressures. One end il of the tank is preferably made integral with the main body portion thereof while the other open end is closed by a closure or shell 12 after the apparatus has been inserted therein; the manner of securing the closure 12 in place will be more clearly described hereinafter.

Within the cylindrical tank 1i) is the transe former construction which includes a suitable iron core; the latter illustratively is of the shell type, as isrbetter seen from Figure fi in which the core is generally indicated at 13. The core has a central leg l about which the windings extend and it has side legs 13a and 13b joined by crossmeinbers 13C and 13d. The laminations of which the core 13 is built up are held together by suitable structural steel members preferably of angie cross-section and may include pairs of angle members 16 and 1'7 extending crosswise or" the leg 13d and clamped together as by bolts 18; and pairs of angle members 19 and 20 which with, the aid of bolts 2i clamp the right-hand end of the core l13 together (see Figures l and 4).

Extending `lengthwise of the outer core legs i3a and 13b are angle members 22 and 23 in pairs, the pair of which, by the aid of ` bolts 18 and 24 clamp the laminations of the side core legs 13a and. 13b securely together. 85

These angle members 22 and 23 extend to the right beyond the core '13 (see Figure 4) where they engage the bottom 11 of the container 10. After the core structure with the windingthereon has been assembled and clamped together and inserted into the tank 10, as shown in Figure 4, the closure 12 is inserted into the left-hand open end of the container to rest against the lefthand end of the core 13; thereupon, the peripheral portions of the casing 10 are bent over as at 10iL onto the closure 12 and Welded thereto as at 25, thus form-ing a seal.

About the middle leg of the transformer core i3 (see Figures l and 2) is a tube-like member 26 of solid dielectric material, such as phenolic condensation product, and upon the member 26 and lengthwise thereof is wound the low potential winding 27, illustratively shown in the drawings as comprising relatively heavy wire wound in two layers. The terminal ends of the winding 23 (see now Figure l) are led by suitable conductors 28 and 29 to the connecting terminals 30 and 31 thatare led to the exterior of the casing 10 through a suitable insulating bushing 32 of any desired construction and in sealed or gas-tight connection with the wall of the container. Conveniently the low voltage terminals may be led through the bottom wall 11 of the tank. Thus, low voltage energy may be led to or from the low voltage winding of the transformer.

Fitted onto the middle leg 15 of the core (see Figure 1) and adjacent the ends thereof are two spiders 33 and 34 which support a tube-like inember of solid dielectric material such as phenolic condensation product, member 35 being of materially larger diameter than the outside diameter of the low voltage winding 27 so that, together with the spaces between the spokes of the spiders 33 and 34, a suitable dielectric and cooling medium, a preferred form of which is hereinafter described, may freely circulate therethrough.

Considering now the construction of the high voltage winding, it may iirst be noted that the sleeve 35, with certain solid dielectric parts .hereinafter described mounted thereon, may be mounted in any suitable way in a lathe or winding machine for rotation so that the windings may be wound thereon. A plurality of spacers of solid dielectric material is rst placed upon the sleeve 35 and in Figure 1 I have shown, by way of illustration, five such spacers; they are indicated at 36, 37, 38, 39 and 60 in Figure 1, and inasmuch as their construction is similar it will suflice to describe one of them in detail. Accordingly, reference may now be made to Figure 3 of the drawings.

In Figure 3 one of these spacers, for example spacer 37, is shown in perspective and in crosssection. It includes a hub 40 whose inside diameter is equivalent to the outside diameter of the sleeve 35 which carries the spacers and projecting peripherally from the hub 40 are two flanges 41 and 42 whose outer faces 41a and 42n extend preferably at right angles to the axis of the spacer while the inner faces 4lb and 42b may be inclined so as substantially to taper the flanges in cross-section, thus to give them greater mechanical strength and rigidity (see also Figure 2).

Flange 41 terminates flush with the left-hand end of the hub 40, as viewed in Figure 3, while the hub 40 projects beyond or to the right, as viewed in Figure 3, of the other flange 42 to form an extension or shoulder 40a.

Extending in agiven plane lengthwise of the axis of the spacer 37 and inclined as is better shown in Figure 3 are two alined holes 45 and 46 in the anges 42 and 41 respectively.

The various spacers 36, 37, 38, 39 and 60 are slipped onto the sleeve 35 substantially in the relation shown in Figure 1 with the extended portions 40a of the hubs 40 directed in the same direction; the spacers are preferably equally spaced from one another and may be held in place by any suitable means, s uch as by pins or pegs of solid dielectric material indicated at 44 (Figure 1) that extend preferably through that part of the hub 40 that is between the flanges 41 and 42 and into the solid dielectric sleeve 35.

This assemblage, suitably mounted to be rotated, is now ready for the reception of the windings. I may employ any suitable insulated wire for building up the high tension winding and 'this is first threaded through the holes 45-46 in the flanges 41-42 of the endmost spacer 36 (see .Figure l) and the space between spacer 36 and spacci' 37 filled up with wire to form a coil 47, the winding proceeding as is hereinafter more clearly described; the end of the coil 47 is then threaded through the hole 45 in the flange 42 of spacer 37 and, after leaving a short length, is cut off.

rPhe end of the supply of wii'e is then threaded through the hole 45 in the flange 41 of spacer 37 and the space between the latter and spacer 38 filled up with wire to form the coil 48. These steps are then repeated to form coils 49 and 50.

Considering now how these individual coils are wound, reference should first be made to Figure 2 in which coil 50, between spacers 39 and 60, is shown in enlarged cross-section and in completed form the conductor or wire is wound into a bottoni layer 5l directly onto the sleeve 35 and between the :dange 41 of spacer 39 and the extension 4()a of the hub 40.

Then there is wrapped around the layer 50 suitable solid dielectric material, such as paper, but this solid dielectric material is graded; for example, it may include a single layer 52 that extends entirely across the wire layer 51 and an additional layer of solid dielectric indicated at 53 that extends only part way, for example half way. The layers 52 and 53 may be of a suitable paper, for example. Winding layer 5l. was wound in a direction from the right to the left, as viewed in Figure 2, and now a second layer of wire indicated at 54 is wound on top of the insulation 52-53 but it is wound in a direction from the left to the right. With respect to the two layers of wire 51 and 54, the relative voltage iierence increases in a direction from the left to the right, as will be clear from the direction in which the layers are built up, but the graded insulation, preferably and conveniently in the form of layers of sheet material of different widths, achieves commensurately and substantially proportionately graded insulation between the two layers of wire.

The above process is repeated until the wind- .has progressed to a thickness equal to the thickness of the hub extension 40a, whence these steps of winding of the layers of wire with interposed graded insulation proceeds further but now the winding layers and the layers of interposed insulation extend between the face 42@ of the flange 42 of spacer 60 and the face 41n of the spacer 39, the winding and insulation thus T extending also above and around the hub extension 40e. In each instance adjacent layers of the winding are separated by graded insulation. When the winding 50 has been completed, its free end is passed through the hole 45 in the flange 42 and into the space between the flanges 41 and 42 of the spacer 6U.

The coils 47, 48, 49 and 50 having thus been completed, the coil ends of adjacent coils, projecting through the holes in the flanges of the spacers, may be connected together as at 55 by soldering or otherwise, the connections being accommodated in the space between the flanges of the individual spacers,

Certain coactions of this construction with e other features of my invention are pointed out in detail hereinafter.

The ends of the high voltage winding Ythus achieved by the serially connected coil sections may be connected in any suitable manner to suitable terminals or the like so that high voltage energy may be led to or down from the high voltage winding. Illustratively, the terminal end of coil 47 may be led by conductor 56 and grounded to the tank or casing 10 at any suitable point, for examplaas is diagrammatically indicated at 57, But there may be instances where it is desirable to employ buffer coils and as illustrative of how, by way of certain features of my invention, I meet even this requirement 15G in a simple and thoroughly practical manner. I have shown the left-hand terminus of coil (Figures 1 and 2) connected as at 58, in the space between the flanges 41 and 42 of the spacer 60 to the end 59 of a buffer winding 61, preferably of a heavier insulated wire or conductor of any suitable character, that is wound into the spacing between the flanges 42 and 41 of an additional spacer member 62 which is mounted on the insulating sleeve 35 but reversed end for end so that its flange 41 abuts face to face against the flange 41 of the spacer 60, whereby the passages 46 through these fianges become positioned adjacent cne another to form a V-shaped channel or passage (see Figure 2) through which the end 59 of the buifer winding 61 may be passed for connection as at 58 to the end of the winding 50.

The buffer winding 61 may be wound at the completion of the winding of the other coils as above described and the turns or layers thereof may be insulated from each other in any desired or suitable way. The end terminal 63 of the buffer winding 61 is led by a conductor 64 through the wall of the casing 10 by means of any suitable insulated bushing or high voltage erminal construction generally indicated at 65 in Figure 1.

The casing 10 is lled with a gaseous dielectric under pressure on the order of fifteen atmospheres; this gas may comprise nitrogen or, by way of further example, a mixture of nitrogen and helium where better heat dissipation is required. This gaseous dielectric under pressure brings about certain unique and advantageous coactions with the features above described.

For example, it fills the space between the low voltage winding 27 and the insulating sleeve 35 which supports the high voltage coils and is in series with the solid dielectric of the tube 35 and thus makes possible, by reason of the distribution of the dielectric stress between the solid dielectric (whose permittivity may be as high as 5) and the gaseous dielectric under pressure (whose permittivity is unity) inversely as the permittivities of the two media, a much closer spacing between the high tension winding and the low tension winding than wouldbe otherwise possible.

But by reason of the features of construction embodied in the solid dielectric spacers which may be made of phenolic condensation product and thus easily molded, I am enabled to accommodate, for a given over-all length of high voltage winding, many more turns than would otherwise be possible. This feature is important in that it makes possible the use of a shorter magnetic circuit, achieves closer linkage between the magnetic circuit and the windings, achieves better regulation of the transformer, and makes for higher efficiency, less cost of construction, and greatly reduced weight of the resultant construction.

To better understand this feature, it might rst be pointed out that the individual coils have to be solidly supported mechanically because they are sometimes subjected to substantial mechanical forces resulting from the electrical reactions that might take place, and it is therefore an important advantage if the coils themselves together with solid dielectric material, such as the hubs 40 with the extensions 40a, are arranged so that they solidly back one another up and support each other against axial movement. The axial length of the hub portions 40-40a (see Figure 1) must therefore be sufficient to provide adequate solid dielectric material between the inner layers of one winding and the inner layers of the adjacent winding in order to insulate these satisfactorily from one another,

But the outer layers of adjacent coils are insulated from each other, in an axial direction, not by solid dielectric alone but by a composite dielectric which includes serially related solid dielectric material (anges 41 or 42) of relatively high permittivity and the serially related gaseous dielectric under pressure, of unity permittivity, that intervenes the anges of the individual spacers.

Because of the inverse distribution of the di electric stress between these serially related dielectrics of such vastly diiferent permittivities, the spacing between the outer layers of adjacent coils can be made much less than the spacing between the inner layers which are mechanically separated by solid dielectric material alone, and thus I am enabled to gain considerably in space, for the windingthat would otherwise-be occupied by solid dielectric material. In the aggregate and in the illustrative embodiment abovedescribed, and shown in the drawings, a high percentage of gain in winding space is thus achieved.

Furthermore, the outside conguration of the spacers insures that the surface leakage path between adjacent coils is relatively long but in this connection it is to be pointed out that the gaseous dielectric under pressure in exceedingly great measure minimizes surface leakage by its coaction with the solid dielectric along the surface of which leakage might otherwise take place.

This coaction of the gaseous dielectric under pressure in so greatly minimizing surface leakage furthermore makes it possible for me to provide hub portions on the spacers of an axial length that takes linto account mainly only the direct dielectric stress toewhich the hub portion is subjected by the parts which it directly insulates, inasmuch as the gaseous dielectric under pressure, coacting with and permeating to all of the surfaces of the solid dielectric vmaterial employed so greatly cuts down the possibility of surface leakage that increase in length on account of the latter factor is hardly necessary. Thus, I am enabled to achieve still further compactness of construction and minimization of solid dielectric material employed, the space occupied by solid dielectric material that would otherwise be necessary being thus utilized by the winding. l

The gaseous dielectric under pressure, having a very high dielectric strength, moreover coacts in a unique way with the paper insulation 52-53 (see Figure 2) that is interposed between thev layers of the coils, where paper is thus employed. It is sorbed by the paper dielectric and occupies the spaces that exist between the fibers of the paper insulation and between the latter and the adjacent layers of wire. Such spaces, if filled with air orother gaseous dielectric at atmospheric pressure, would be over-stressed, due to dielectric flux refraction and due to the unequal voltage distribution across dielectrics of unlike permittivities (air and paper) in series multiple. For example, the permittivity of the paper is on the order Yof 3 or 4 and the permittivity of the air is about unity. The air at atmospheric pressure, a weak dielectric, would thus be made to assume three or four times the stress assumed by the paper and would rapidly break down and cause puncture. However, such possible air spaces in accordance with certain features of my invention, are lled with the gas under pressure on the order of fifteen atmospheres and hence one whose dielectric strength is many times that of air at atmospheric pressure. The same abovementioned stress is similarly divided between the paper and the gas under pressure inversely as their permittivities, the permittivity of the gas under pressure being about unity but the very high dielectric strength of the gas under pres sure can safely assume three or four or more times the stress assumed by the paper without breakdown, and puncture is thus effectively prevented.

Should, therefore, there be any relatively thin or weakened portions in the paper, such portions are greatly reinforced by the coaction therewith of the gaseous dielectric under pressure, the latter acting to cause the weaker or thinner portions of the paper to assume a much smaller fraction of the total stress than would otherwise be the case, and thus breakdown and puncture is further prevented.

. To illustrate certain of the unusual results flowing from such coaction, it might be pointed out that the dielectric strength of, for example, dry uncalendered linen paper even of poor stock is increased about 350% when made to coact with nitrogen under fifteen atmospheres of pressure.

Due to this coaction, it is possible to make use of less heavy paper and even of thinner paper or lesser layers and thus I am enabled further to lessen the space occupied by solid dielectric material and make such space available for the reception of the winding.

Furthermore, I achieve other important and new results due to this coaction; it is well known that, in a transformer, the capacity between turns and between layers and the like should be reduced as much as possible. A function of the capacity is the character of the dielectric medium and the higher the permittivity of this me dium the higher is the capacity. For example, where paper insulation is used with oil, the permittivity of the resultant dielectric medium is on the order of 4.5; compared to that value, I am enabled, with the combination of paper and gaseous dielectric under pressure, to achieve not only a better insulation as such and to lessen the quantity of paper that would otherwise be employed, but also to achieve a permittivity on the order of 2,5 or so. For example, the permittivity of dry uncalendered kraft paper and nitrogen at fifteen atmospheres pressure is about 2.3. Thus the condenser or capacity effect is greatly reduced.

It will thus be seen that there has been provided in this invention a transformer construc tion and method of making the same in which the various objects hereinabove noted, together with many thoroughly practical advantages, are successfully achieved.

As many possible embodiments may be made of the mechanical features of the above invention and as the art herein described might be varied in various parts, all without departing from the scope of the invention, it is to be understood that all matter hereinabove set forth or shown in the accompanying drawings, is to be interpreted as illustrative and not in a limiting sense.

I claim:

1. In transformer construction,l in combination a core having a sleeve of solid dielectric material thereabout and spaced therefrom, a plurality of coil spacers spaced along said sleeve, each spacer having a hub portion and two spaced flanges, the` hub portion extending beyond the outer face of at least one of said flanges, coils wound between spaced spacers and onto said sleeve and the pro jecting portions of said hubs, and a gaseous dielectric under pressure filling the space between said sleeve and the core and the space between the flanges of each spacer.

2. In transformer construction, in combination, a core having a sleeve of solid dielectric materia] thereabout and spaced therefrom, a plurality of coil spacers spaced along said sleeve, each spacer having a hub portion and two spaced flanges, the hub portion extending beyond the outer face of at least one of said flanges, coils wound between spaced spacers and onto said `eeve and the projecting portions of said hubs, and a gaseous dielectric under pressure filling the space between said sleeve and the core and the space between the flanges of each spacer, said coils being wound in layers so that the potential of the innermost layer is different from the potential of the outermost layer, each spacer having a channel through which the end of the innermost layer of the adjacent coil is passed into the space between the ilanges of the spacci', means connecting adjacent coils and positioned in the space between the flanges of the spacer separating adjacent coils, and a gaseous dielectric under pressure filling the space between said sleeve and the core and the space between the flanges of the spacers.

3. A high voltage winding comprising, in con bination, a solid dielectric support, a plurality of winding sections spaced therealong, means cornprising solid dielectric material for insulating from each other those portions of adjacent coils that are nearest said support, and means comprising solid dielectric material and a gaseous dielectric under pressure serially related therewith for insulating from each other the remaining portions of adjacent coils, the dimension in the direction of dielectric stress of said lastmentioned insulating means being less than that of said first-mentioned insulating means.

4. A high voltage winding comprising, in combination, a plurality of coils arranged in axial alinement along a solid dielectric support, each coil having a lesser dimension in an axial direction where its radius is smallest than where it is of largest radius, solid dielectric material interposed between those portions of adjacent coils that are of lesser axial dimension, and solid dielectric material and a gaseous dielectric under pressure in series therewith interposed between those portions of adjacent coils that are of greater axial dimension.

5. A high voltage winding comprising, in combination, a solid dielectric support, a plurality of winding sections spaced therealong, means comprising solid dielectric material for insulating from each other those portions of adjacent coils that are nearest said support, and means cornprising two dielectrics in series of different permittilities for insulating from each other' the remaining portions of adjacent coils and having a lesser dimension in the direction of the dielectric stress than has said rst-mentioned insulating means.

6. A high voltage winding comprising, in combination, a plurality of coils arranged in axial alinement along a solid dielectric support, each coil having a lesser dimension in an axial direction where its radius is smallest than where it is of largest radius, solid dielectric material in terposed between those portions of adjacent coils that are of lesser axial dimension, and means comprising a plurality of dielectrics serially related and having different permittivities for in.- sulating the portions of adjacent coils that are of greater' axial dimension.

7. A high voltage winding comprising, in combination, a plurality of coil sections insulated from each other by a plurality of insulating means functioning in parallel, one of said insulating means comprising solid dielectric material and the other comprising a plurality of dielectrics of diilerent permittivities arranged in series, said last-mentioned insulating means occupying less space than said solid dielectric insulating means.

8. A high voltage winding comprising, in combination, a plurality of coil sections insulated from each other by a plurality of insulating means functioning in parallel, one of said insulating means comprising solid dielectric material and the other comprising a plurality of solid dielectric members separated by a dielectric of lower permittivity than that of the material of which said members are made.

9. A high Voltage winding comprising, in combination, a plurality of coil sections insulated from each other by a plurality of insulating means functioning in parallel, one of said insulating means comprising solid dielectric material and the other comprising a pair of spaced solid dielectric members wlth the intervening space lled with a gaseous dielectric .under pressure.

l0. In transformer construction, in combination, a plurality of spaced separators 0f solid dielectric material, each separator having a hub portion and spaced flanges, coils in the space between separators, and a buier coil wound in the space between the ilanges of at least one of said separators.

1l. In transformer construction, in combination, a plurality of spaced separators of solid dielectric material, each separator having a hub portion and spaced flanges, coils in the space between separators, successive coils being connected together and the connections being located in the space between flanges of the spacers.

FRANKLIN S. SMITH.

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