Document OEO7woXB2JgqDV6wRkpZ957KK

FILE NAME: McGraw-Edison (ME) DATE: 1952 Aug 6 DOC#: ME024 DOCUMENT DESCRIPTION: Patent - High temp transformer construction or the like [Approved - 1958 Mar 18] March 18, 1958 m. l. m a n n in g 2,827,616 HIGH TEMPERATURE TRANSFORMER CONSTRUCTION OR THE LIKE F ile d Aug. 6, 1952 2 Sheets-Sheet. 1 March 18, 1958 m. l. m a n n in g 2,827,616 HIGH TEMPERATURE TRANSFORMER CONSTRUCTION OR THE LIKE F ile d Aug. 6, 1952 2 Sheets-Sheet 2 / '/ < / . 7. 22 t '/*/. <1 . / if/ , <7. United States Patent Office Patented Ma2r.,81287, ,1691568 1 2,827,616 HIGH TEMPERATURE TRANSFORMER CONSTRUCTION OR THE LIKE Melvin L. Manning, Upper St. Clair Township, Allegheny County, Pa., assignor to McGraw-Edison Company (Pennsylvania Transformer Division), a corporation of Delaware Application August 6, 1952, Serial No. 302,887 13 Claims. (Cl. 336--196) This invention relates to a new high temperature trans former construction or the like. More particularly, it pertains to a new kind of transformer or the like in which silicone and fiber insulating materials are combined. High temperature transformers and other high tempera ture electrical induction constructions have been an objective of various manufacturers for some time. The work in that direction received added impetus upon the widespread introduction of silicone materials a few years ago. Despite the recognition of the electrical qualities of such materials, a number of drawbacks attended use of them. One manufacturer despite the availability of such silicone materials provided heat-resistant glass cyl inders for insulating barriers. I have discovered a new construction which enables the remarkable properties of. silicone materials to be fully employed for insulation and support.purposes to provide a transformer or the like with a class-H rating. At the same time, I am enabled to shield the leads and windings by means of my new construction in a manner which pre serves the advantages thereof without risk of creepage or breakdown in that area. Other advantages of my new construction are that it provides protection against .local dielectric and thermal weakness points and permits effi cient construction practices to!he employed. Other objects and advantages of this Invention will be apparent from the following description and from the drawings, which are illustrative only, in which Figure 1 is a plan view, partly schematic, of low and high voltage windings, barriers and spacers of a high .tem perature dry transformer embodying my invention; Figure 2 is a view in elevation of the structure ..shown in Figure 1 taken along line II--II of Figure 1; Figure 3 is a somewhat detailed view of the portion of the. structure shown in. Figure 1;adjace.nt the low voltage winding, leads and shielding, taken along the .line III--III of Figure 1; Figure 4 is an illustrative dissected view of a .formable silicone resin laminate employed in my new construction; .Figure 5 is an-illustrative dissected view of a flexible silicone rubber and fiber ply material employed in my new construction; .Figure 6 is a section through a core to low voltage wind ing, barrier in my new construction.showing the silicone materials of Figures ,4 and dim an interleaved combina tion; and Figure 7 is a.diagrammatic, showing.of one end of a transformer embodying my ..invention in the course of being constructed. Referring to the drawings, a power transformer 10 is shown in Figures 1-and 12 in sufficient, detail to illustrate the new construction features, in one embodiment of my invention. In that embodiment, a .cruciform laminated core leg 11 of a conventional magnetic core may be illus trated as shown-in Figure 1 by dot-and-dash lines. A core-to low voltage winding. (CL) barrier envelope 12 sur rounds .core leg 11 in close,proximity thereto. Axial spacers 13 may be positioned around the outside of CL 2 barrier 12 in spaced arrangement where they are held in the course of the winding of the concentric layers 14 and 15 of a helically wound low voltage winding. Spacers 13 may be held against barrier 12 by a suitable silicone adhe5 sive or other means. The conductors employed in winding the low voltage winding layers 14 and 15 may be wire which is served with a glass silicone resin bonded tape insu lation prior to winding. In other cases, such conductors may be served with other materials such as flexible asbes10 tos or glass cloth silicone tape or "Teflon" tape. Insula tion in the form of a cylindrical envelope 16 may be inter posed between the layers 14 and 15 by using, for example, silicone rubber ply material similar to that employed In the construction of CL barrier 12. 15 A further series of axial spacers 17 may be held against and spaced around the exterior of the low voltage wind ing coil comprising layers 14 and 15. A further insulat ing (HL) barrier envelope 18 between the low voltage coil 14-- 15 and a high voltage coil 19 may be provided under 20 my new construction entirely of silicone and fiber matrix materials. HL barrier 18 may comprise a combination of more of the interleaved plies than the number-used for the CL barrier as shown in Figure 6. Barrier 18 insulates _ the lw voltage windings from the high voltage windings 25 and must withstand the relatively high voltage potentials and thermal increases to which it is subjected. A further series of axial spacers 20 of solid or molded U shapes may be fastened at uniform intervals around and to the exterior of HL barrier 18. Alternate spacers 21 in the series-of 30 spacers 20 may be of keytone shape, if desired, to permit keying engagement with and movement during assembly for lateral spacers 22. The high voltage coil 19 may comprise a plurality of double layer horizontal pancake windings 23 in vertically 3o stacked arrangement as shown in Figure 2, respective, ones of said such windings being interconnected electrically by crossover.conductors 2.4. The radial spacers 22 may be made of a mechanically and electrically strong material like porcelain. Axial spacers 13,17 and 20 may be made 40 of class-H insulating .material in the form of solid ,or channel-shaped spacers. As an example, I have discov ered that glass cloth or asbestos cloth bonded with silicone resin materials may be molded or otherwise shaped and ..cured to provide axial spacers of markedly superior,me0 chanical and dielectric strengths. The annular pressure plates and tie rods which respectively bear endwise, on the respective windings and lateral.spacers 22 have.not been illustrated as such.features will be well understood by those skilled in the art. .The vertical, ducts 25 between the axial spacers .13,.the vertical ducts .26 between the axial spacers 17, the vertical ducts 27 between the axial.spacers .21 and the lateral ducts..28.between the.lateral spacers 22 afford access to the turns of the respective windings for 65 whatever cooling or ambient fluid may be employed. in the case of a sealed dry-type transformer embodiment, a gas like nitrogen may be used to fill the, gas space within a transformer tank in which my new construction is. placed. In construction the embodiment shown ,in Figures ,1 qq and 2, one mode, of making the new barrier envelope is illustrated in connection with making a barrier. 18.and other barrier 12 may be similarly made. In the, trans former or the like being constructed, any entire or other partial barriers, whether cylindrical or arcuate, may be gg constructed in accordance with my invention. In that invention, one or more sheets 29 of a formable.silicone resin and fiber laminate is combined in interleaved man ner with one or more plies 30 of flexible silicone rubber and fiber material. Generally, in preparing a cylindrical 70 envelope barrier in accordance with this invention, each kind of . material is formed into the desired cylindrical shape beginning with the innermost layer. Thus, a cylin der of the laminate may be provided and the ends over lapped' and fastened by a silicone adhesive, for example, ply 30 are provided and inserted in place as shov/n in or by class-H tapes of sufficient strength, enough turns Figures 1 and 3 generally in the course of the construc being made in the laminate layer to provide a due share tion winding as on lathe 31. The surface of the insula of the total insulation of the new combination. Then tion exposed to the lead or leads is preferably faced with ; one or more layers of the silicone rubber and fiber ma 5 a silicone rubber coated glass cloth or asbestos cloth. terial may be. formed in cylindrical shape around the In such construction, as an example, the innermost laminate and the outermost end of said material fastened plate 34 may be pinched between and held between the again by silicone adhesive or other means. In some top turns of layer 14 and the adjacent axial spacers 13 cases, the laminate material may have a silicone rubber on the other side of that plate 34. On the other hand, -layer affixed to one or both surfaces of the laminate be 10 if keep-back insulation of a class-K category is inter fore the laminate is formed. Around the silicone rubber posed between the plates 34 above the topmost turn of and fiber material, another one or more layers of lami the layers 14 and 15, and, on each side of leads 33 in a ' nate material may be wound against the exterior of the circumferential direction, as shown in Figure 3, then the silicone rubber and fiber material layer or layers to com plates 34 may respectively be held between such keep plete the interleaving. As shov/n in Figure 6, barrier 12, 15 back insulation 35 and the axial spacers 13 and 20 re for example, may be made in the form of a right cylin spectively. The height of the plates 34 above the bar der, the innermost layer of which as shown is a layer of riers 12 and 18 guards against creepage and any possi formable laminate surrounded by two layers of silicone bility of short-circuiting at the outlet shown of the taps rubber and fiber in turn surrounded by a single layer of 33 relative to parts of the transformer at different voltage laminate again, the entire construction comprising a 20 potentials. single barrier envelope with markedly superior features, Laminate sheets such as sheets 29 may now be ob both dielectrically and mechanically, to any insulation tained as a commercial article having a fiber cloth matrix heretofore provided. of an inorganic material like heat-cleaned glass or as The construction of a new barrier envelope may be bestos. Such fibrous matrix in the case of glass, for performed in a winding lathe such as those used in the 25 example, may be in part a staple cloth 35 woven of short transformer industry. For example, as illustrated in lengths of glass filaments in the manner of a staple vege Figure 7, a barrier such as HL barrier 18 is shown being table fiber cloth. Laminate 29 also preferably employs formed in place. The CL barrier has already been a fiber matrix cloth 37 woven of continuous glass fila formed and is molded in a lathe 31 which rotates in the ments placed in juxtaposition to the cloth 36. These direction of the arrow. If desired, a steel cylinder may 30 cloths 36 and 37 are impregnated v/ith a silicone resin be used as the innermost mold to initiate the construc which enters the interstices of the cloth and wholly tion of barrier 12 thereagainst in which event a mold covers them to form, when solidified, the laminate sheets release compound, for example, may be used between 29. In place of such fiber matrix, it may also be possible the exterior of the mold cylinder and the interior cylin to use such inorganic fibers in the form of a felted cloth drical" surface of the CL barrier 12. In the partially 35 or matte highly resistant to electrical, mechanical and completed construction shown in Figure 7, the axial thermal deterioration. The silicone resins may be of a series of spacers 18 has been positioned, the low voltage kind such as those sold by Dow Corning Corporation winding 14--15 has been wound on the lathe around the under the trade identification "DC 2104." A silicone ma spacers 13, the spacers 17 have been positioned.and the terial laminate of suitable character for employment in lathe is in the midst of winding the HL barrier 18 as 40 my invention is one such as that made by Mica Insulator aforesaid with a strip 29 of laminate. Enough layers of Company of Schenectady, New York, having the trade silicone laminate and silicone rubber material will be designation "E-724 Lamacoid." In preparing laminate utilized in the new interleaved relation to provide the 29, usually from 40 to 60 percent of the weight thereof necessary mechanical and dielectric strength required for will be the partially or wholly cured and solidified sili the high-low voltage barrier envelope service in the par 45 cone resin. In applying the laminate 29, it is preferable ticular transformer or the like under construction. When to place the staple cloth 36 on the inside of the bend and such winding of barrier 18 is completed, that barrier, the continuous fiber cloth 37 on the outside, generally as is the case of bander 12, will have sheets 29 and 30 with the warp of both cloths parallel to the longitudinal interleaved throughout. Preferably, the sheets 29 and axis of the insulation envelope or cylinder being con 30 are of a width equal to the entire height of the trans 50 structed. former windings plus the additional height equal to the Suitable silicone rubber plies such as the sheet 30 are keep-back insulation length desired at the respective axial also now commercially available on the market for ends of the transformer or the like. employment, in my invention. Such a silicone rubber The new construction of this invention also effects a material may comprise a cloth of inorganic fiber like marked improvement in taking care of lead outlets par 55 glass or asbestos, thoroughly heat-cleaned to remove ticularly in the case of the more interior windings such organic binders, which cloth forms a matrix for a silicone as the low voltage coil 14--15 shown in the illustrated rubber coating. One suitable silicone elastomer for such embodiment. Leads 32 from the high voltage coil 19 do coating purpose is "Silastic," a trade name of Dow not generally present any particular problem in the case Corning Corporation, which corporation also makes a of an embodiment such as that shown because of their 60 suitable silicone rubber and fiber matrix material suitable presence in the vicinity of the exterior of the transformer for the sheets 30. The fiber glass which may be utilized in where they can, for example, be readily conducted up the construction of the new insulation components of this wardly through an insulating tube, which, again, may be invention should have characteristics suitable for satis made of tubular silicone material now available on the factory electrical, mechanical and thermal service in a market. 65 class-H transformer. Certain of the glass products On the other hand, conductor leads 33 are generally termed "Fiberglas" by Owens Corning Fiberglas Corpora connected not only to the ends of the low voltage coil tion are suitable in making up the matrices for silicone --15 but also to intermediate points therein and all sheet materials like sheets 29 and 30. of the leads or taps have to have an outlet from the in 70 In my employment of such new insulation in a trans former or the like, I have also found it useful to have the terior of the embodiment of the new transformer which dielectric constants of the interleaved sheet materials like is shown. In my invention, cylindrical insulation plates sheets 29 and 30 of about the same dielectric constant, 34 which are arcuate and may be preformed of inter which may be in the neighborhood of 3.5. Thereby, the leaved layers of laminate like laminate 29 alternating gradient through the materials in series because of their with interleaved layers of silicone rubber material like 75 interleaved relation appears to be relatively uniform and 2, 827,818 6 .................... the voltage strength throughout the new insulation struc former than those described herein will be of suitable ture will also be generally uniform and foci of weakness electrical and mechanical characteristics for the intended for breakdown in the course of use are avoided. The use purpose. The invention is applicable not only to dry of various filler materials such as titanium dioxide or but also to wet transformers or the like and to ventilated zinc oxide may be employed in the manufacture of the 5 and sealed transformers and the like. silicone rubber material, as will be well understood by Various changes may be made in the practice of the those in the art to whom this invention is disclosed, to present invention without departing from the spirit there achieve relative equality of the dielectric constants of of or the scope of the appended claims. the component laminate and silicone rubber materials in I claim: the composite insulation. Other ways may be employed 10 1. In an electrical transformer, in combination, an at to harmonize the respective constants of the two sheet least partially cured silicone resin impregnated insulating materials. sheet having a heat-cleaned inorganic fiber base material In constructing the new transformer the laminate may and an at least partially cured silicone rubber insulating be formed cold for bent diameters exceeding about 10 sheet having a heat-cleaned inorganic fiber base material, inches whereas formerly it was believed that such kind 15 said sheets being contiguous and positioned between and of material had to be heat formed. I find, however, that insulating portions of said transformer having a potential not only may such material be cold formed but that such difference therebetween, said fibers being selected from a cold forming for laminates not in excess of about yS2 of group consisting of glass and asbestos. an inch in thickness does not produce any tendency to 2. In a transformer, in combination, at least one form- craze it, particularly when used in cooperation with a 20 able silicone resin impregnated sheet having a heat- silicone rubber material like the sheets 30 having a thick cleaned, continuous filament, inorganic fiber cloth, and ness between about %4 of an inch and %2 of an inch. In at least one silicone rubber sheet having a heat-cleaned some cases the laminate, particularly for smaller diameter inorganic fiber cloth, said fibers being of a material se uses or thicker sheets, may be heated to about 165 C. lected from a group consisting of glass and asbestos, said for a relatively few minutes generally not in excess of 25 sheets being contiguous and disposed between and insulat four. ing portions of said transformer having a potential dif It appears that the new composite insulation forms ference therebetween. a unitary mass which functions ideally as the supporting 3. In a transformer, in combination, a relatively thin, framework for the windings of the new transformer and bendable, at least partially cured silicone resin impreg provides dielectric characteristics and strength between 30 nated sheet having heat-cleaned inorganic continuous the various parts of the transformer, at different potentials filament and staple fiber cloths in superposed relation, and to enable a new transformer to function in the class-H a relatively thin, at least partially cured silicone rubber category without the disabilities of prior transformers in such category. The sheet materials 29 and .30 so em sheet, said sheets being contiguous and positioned between and insulating portions of said transformer having a po ployed may in'the case of the laminate be partly Or fully 35 tential difference therebetween. cured whereas in the case of the silicone rubber and fiber matrix material it will generally be in a partly cured 4. In a transformer, in combination, an insulation barrier comprising silicone resin impregnated sheets inter state. Curing of the insulation after completion of the winding assemblies may be performed at a temperature leaved with silicone rubber sheets, said barrier being positioned between and insulating portions of said trans at about 250 C. Prior to such curing, the winding 40 former having a potential difference therebetween, said assembly may be dipped into a silicone type of varnish, sheets having approximately the same dielectric constant. as one example, to complete the mechanical binding of 5. In a transformer, in combination, a bendable silicone the new transformer windings and assembly. One ad resin impregnated sheet having an inorganic heat resistant vantage of such a varnish is that its high gloss reduces any opportunity for the settlement of dust or other con 45 and electrically insulating heat-cleaned fibrous cloth, and taminant which might constitute a leakage path and a flexible, at least paritally cured silicone rubber coated another is its high craze resistance. Thereafter, if not sheet having an inorganic heat resistant and electrically earlier, any mold cylinder which has been employed will insulating heat-cleaned fibrous cloth, said sheets being be removed before the completion and performance test contiguous and positioned between and insulating portions ing of the entire transformer or the like. 50 of said transformer having a potential difference there _ A study of the advantages of my new composite between, said sheets further having approximately the same dielectric constant. insulation and cooperation in a transformer or the like leads to the belief that the interleaved substances com 6. In an electrical transformer, the combination with a plement one another in the course of use to a marked and closed magnetic core having a winding leg and an elec unusual extent. For example, the silicone rubber and 55 trical coil surrounding said winding leg of a tubular in fiber matrix material appears to at least hinder the aging sulating barrier disposed between and insulating said leg of the silicone resin and fiber matrix laminate and also to and said coil comprising interleaved at least partially cooperate in dissipating any tendency to craze or crack cured silicone resin impregnated sheets having a heat- which the laminate might otherwise have. Further, the cleaned, inorganic fiber, base material and at least par heat conductive properties of the silicone rubber material 60 tially cured silicone rubber sheets having a heat-cleaned, appear to be superior to those of a silicone laminate such inorganic fiber, base material, said fibers being selected as that described with the consequence that the thermal from a group consisting of glass and asbestos, said leg, lag of the one material like sheet 29 is materially aided if said barrier, and said coil being bound together by a not overcome by the thermal conductivity of sheet mate silicone varnish. rial like sheets 30. Thereby the new transformers or the 65 7. In an electrical transformer, the combination with like can be consistently worked and operated at higher concentric high and low voltage windings of a tubular in levels and/or for longer times as in the case of varying sulating barrier interposed between and insulating said load cycles or load demands on transformers, without windings comprising interleaved silicone resin impreg detriment. nated sheets having a heat-cleaned, continuous filament, The hot spot temperature standard of 180 C. set some 70 inorganic fiber cloth and silicone rubber sheets having a years ago for class-H insulation can be materially ex heat-cleaned inorganic fiber cloth, said fibers being of a ceeded by means of the present invention without any material selected from a group consisting of glass and observable deterioration. In constructing the new trans asbestos, said barrier and windings being bound together former or the like, it will be understood that other insulat by a silicone varnish. ing materials that may be used for other parts of the trans- 75 8. In an electrical transformer, the combination with 2,827,016 7 concentric windings of a tubular insulating barrier inter s staple fiber cloth, said continuous filament cloth being posed between-and insulating said windings comprising disposed radially outward from said staple fiber cloth and formable silicone resin impregnated sheets interleaved having the warp thereof parallel to the axis of said tubular with silicone rubber sheets, each of said sheets having a barrier, each of said silicone rubber sheets having at least heat-cleaned inorganic fiber base material, said sheets 5 one inorganic fiber cloth, said cloths being of a material further having approximately the same dielectric constant. selected from a group consisting of glass fiber and asbestos 9. In an electrical transformer, an insulation barrier fiber. comprising at least one formable silicone resin impreg 12. In stationary induction apparatus, in combination, nated sheet having a glass fiber base material and at least at least one formable silicone resin impregnated sheet one silicone rubber sheet having a glass fiber base ma 10 having a heat-cleaned inorganic filler and at least one terial, said sheets having approximately the same di silicone rubber sheet having a heat-cleaned inorganic electric constant and being disposed between portions of filler, said sheets being contiguous and disposed between said transformer having a potential difference there and insulating portions of said stationary induction ap between. paratus having a potential difference therebetween. 10. In an electrical transformer, the combination of a 13 13. In an electrical transformer, the combination of a cylindrical winding and an arcuate insulating barrier, cylindrical winding and an arcuate insulating barrier, said said barrier comprising silicone resin impregnated sheets barrier comprising silicone resin impregnated sheets inter interleaved wtih silicone rubber sheets, each of said sili- leaved with silicone rubber sheets, each of said sheets hav .cone resin sheets having at least one heat-cleaned con ing a heat-cleaned inorganic filler, said barrier being ad- tinuous filament cloth and at least one heat-cleaned staple 20 jacent said cylindrical winding and insulating said wind fiber cloth, said continuous filament cloth being disposed ing from portions of said transformer at potentials differ radially outward from said staple fiber cloth and having ing from that of said winding. its warp parallel to the axis of said cylindrical winding, each of said silicone rubber sheets having at least one References Cited in the file of this patent heat-cleaned cloth, said cloths being of fibers selected 25 .from a group consisting of glass and asbestos, said barrier being adjacent said cylindrical winding and insulating said winding from portions of said transformer at poten tial1s1.diIfnferainngeflreocmtrictahlattraonfssfaoirdmwerin, dtihneg.combination with 30 concentric windings of a tubular insulating barrier inter posed between said windings, said barrier comprising sili cone resin impregnated sheets interleaved with silicone rautblbeearstshoenetes,ceoancthinoufosuasidfirleasminenimt pcrleogthnaatenddshaeteltesahsatvoinnge 35 1,452,158 1,639,145 1,664,541 2,348,239 2,454,218 2,460,795 2,527,236 2,571,418 2,601,337 UNITED STATES PATENTS Horelick------------------------ Apr. 17, 1923 Niemann----------------------- Aug. 16,1927 C ooper------------------------- Apr. 3, 1928 B eldi__________________ May 9, 1944 Schulman---------------------- Nov. 16, 1948 W arrick_______________ Feb. 1, 1949 W hitman_______________ Oct. 24, 1950 Castenschiold------------------ Oct. 16, 1951 Smith-Johannsen------------- June 24, 1952