US2975385A - Non-liquid transformer - Google Patents

Description

W. J. NOVAK NON-LIQUID TRANSFORMER March 14, 1961 4 Sheets-Sheet 1 Filed Oct. 15, 1959 IN V EN TOR. W/LZ/AM J NOVA/f 4 Sheets-Sheet 2 Filed. Oct. 15, 1959 INVENTOR. W/ll/AM J. NOV/1A Arrow/2x March 14, 1961 w. J. NOVAK 2,975,385

NON-LIQUID TRANSFORMER Filed Oct. 15, 1959 4 Shee .s$heet 3 INVENTOR. W/[l/AM J NOVA/f A TIU/P/Yff March 14, 1961 w. J. NOVAK NON-LIQUID TRANSFORMER 4 Sheets-Sheet 4 Filed Oct. 15, 1959 INVENTOR- W/Zl/AM J. NOV/4K ,II!!!lilllillllfilflllilllilur IIIIIII\I b 0 I a \II. M

United States Patent Ofifice 2,975,385 Patented Mar. 14, 1961 NON-LIQUID TRANSFORMER William J. Novak, Oreland, Pa., assignor to H. K. Porter Company, Inc., Philadelphia, Pa., a corporation of Delaware Filed Oct. 15, 1959, Ser. No. 846,678

7 Claims. (Cl. 336-96) This invention relates to power distribution transformers, and more particularly relates to transformers wherein the usual construction including a steel tank filled with insulating oil has been dispensed with in favor of a completely encapsulated transformer in which the insulation function is provided by materials which in their final state are solid rather than liquid.

The advantages of a dry type of transformer construction are quite numerous and significant insofar as the user is concerned, and such dry type transformers can be manufactured at a cost which is substantially the same as that of an oil filled type. In general the advantages which may be realized from a dry type of transformer construction are, firstly, that such a transformer can be made to be substantially lighter in weight and smaller in size than an equivalent capacity oil filled type so that installation of the transformer on a mounting pole may be much more easily effected. For example, whereas oil filled transformers of a particular kva. rating may weigh about 450 pounds, the equivalently rated dry type of transformer according to my invention may Weigh about 300 pounds and occupy only about 25% of the volume of the oil filled type.

Secondly, the noise level can be made very low because the encapsulation of the transformer, subsequently to be described, almost completely eliminates vibration of the steel core laminations. Additionally, the absence of the insulating oil permits the transformer to be made in a much smaller physical size, and, of course, there is no insulating oil which may deteriorate because of contamination. Maintenance problems are, of course, reduced because there are no exposed metal parts requiring painting, and the encapsulation process prevents transformer outages caused by short circuits between the live terminals and the casework through the bodies of birds and small animals. Finally, when the encapsulation process is carried out by employing a nonhygroscopic outer plastic coating, the entire transformer is rendered much less susceptible to breakdown in wet or damp environments by preventing moisture from penetrating into the coil structures. Accordingly, it is a primary object of my invention to provide a power distribution transformer which does not rely upon an oil tank in which transformers of this type are usually housed, but is instead a dry type of transformer.

It is another object of my invention to provide a novel power distribution transformer which is relatively light in Weight and small in size by comparison with an equivalent capacity oil immersed transformer.

Still a further object of my invention is to provide a novel power distribution transformer which is characterized by a relatively low noise level due to the fact that the transformer core laminations are restrained from vibration by an encapsulating plastic composition.

Yet another object of my invention is to provide a novel power distribution transformer which is less subject to electrical breakdown than a comparable capacity transformer of conventional design by employing a dielectric insulating material not subiect to contamination in use. p

The foregoing and other objects of my invention will become apparent from a careful reading of the following specification taken in conjunction with an examination of the appended drawings, wherein:

Figure l is a front perspective view of a typical transformer according to the invention;

Figure 2 is a rear perspective view of the typical transformer according to the invention which is illustrated in Figure 1;

Figure 3 is a front perspective view of a typical transformer according to the invention similar to that seen in Figure l, but fragmented to enlarge the scale and having some portions of the exterior broken away to reveal certain constructional details;

Figure 4 is a fragmented cross-sectional view through the bottom of the transformer of Figure 3 as viewed along the lines 44 of that figure;

Figure 5 is a fragmented cross-sectional view taken through the transformer of Figure 3 along the lines 55 of that figure;

Figure 6 is a fragmentary perspective view of the upper part of the transformer of Figure l, with a portion thereof sectioned away to reveal certain of the constructional details thereof;

Figure 7 is a partial perspective view of the core and coil assembly of the transformer of Figure 1;

Figure 8 is an enlarged detail of the area within the phantom lines of Figure 7 and illustrates the construction of each of the transformer coils;

Figure 9 is a perspective view in section through the transformer core and coil assembly and is taken through such assembly along the lines 99 as indicated in Figure 7;

Figure it) is a sectional view taken through the transformer core and coil assembly as would be seen when viewed along lines 10-10 of Figure 9.

In the several figures like elements are denoted by like reference characters.-

A gross understanding of the transformer structure will best be had by referring first to Figures 1. 2 and 3, and particularly to Figure 3. As best seen in the sh owing of Figure 3, the basic transformer includes upper and lower core housings 3S and 34, the coil pressure pads 33 seated upon the flanges of the lower core housing 34 and upon which in turn rest a pair of side by side composite coil structures generally indicated as at 20-20 disposed about parallel legs of a laminated core structure 3! high voltage and low voltage bushing assemblies including the inverted L- shaped brackets 36 and 37, and the bushings 43 and 44, clamping stud assembly 40, lifting lugs 48, and support lugs 49. The coil assemblies 2il2il illustrated in Figure 3 are identical to one another and the make-up thereof will he described subsequently in connection with the showing of Figure 8. However, before proceeding to a detailed description of the coil structures 202i!, it will be more conducive to a complete understanding of the invention to first consider the method of. assembling the entire transformer by assuming that the coil structures 20-20 have already been pre-forrned and are ready for assembly with the other transformer components.

As best seen from the showings of Figures 3 and 4, the lower core housing 34 is U-shaped in cross-section having a bottom wall 50 and a pair of vertically extending front and rear walls 51 and 52 respectively. Turned outwardly from the front and rear walls 51 and 52 are a pair of flanges 53 to provide a base upon which are seated the front and rear coil pressure pads 33. It should be observed that the spacing between the front and rear Walls 51 and 52 of the lower core housing 34 is just sufficient to accommodate the depth of the laminated core 30, the core 30 being seated upon the bottom wall 50 of the lower core housing 34. As best seen in the showings of Figures 3 and 5, the front and rear walls 51 and 52 of the lower core housing 34 are of generally trapezoidal shape having the smaller trapezoidal base merging with the bottom wall 50 and the longer trapezoidal base being the one from which the pressure pads supporting flanges 53 are turned out. Welded or otherwise secured to the sloping trapezoidal sides of the lower core housing 34 at both ends thereof are a pair of angle members 54-54 which provide a pair of end flanges 55 upon which are seated the end coil pressure pads 33.

Seated upon the coil pressure pads 33 is the composlte core and coil structure including the laminated core 30, the pre-formed coils 20-20, the banding straps 31 and the banding seals 32. The composite core and coil structure is assembled in the manner which will be most readily understood by referring firstly to Figure 9 and then to Figure 3. Referring first to Figure 9 it is observed that the core 30 is composed of an upper C-shaped section 60 and a lower C-shaped section 61. The coil assemblies 20-20 may be first slipped downwardly over the upwardly extending legs of the core lower section 61, and the core upper section 60 may then be placed in the position illustrated by projecting the downwardly extending legs thereof into the central openings of the pro-formed coil structures to form a complete core having each of its side legs disposed within a coil. As best seen in Figure 3, the banding straps 31 are then placed around the two core sections and tightly secured by means of the banding seals 32. The composite core and coil structure so formed is now placed within the lower core housing 34 by seating the bottom of the core lower section 61 between the front and rear walls 51 and 52 of the lower core housing 34, with the coil structures 20-20 seated upon the coil pressure pads 33. Of course, the composite core and coil assembly could have been formed in other ways, as for example by winding a continuous strip core through the central window openings of the coil structures so that the resultant core would not be characterized by having an upper section 60 and a lower section 61.

With the composite core and coil structures seated within the lower core housing 34, the high voltage bushing assemblies including the bracket 36 and bushings 43, and the low voltage bushing assemblies including the bracket 37 and bushings 44 are placed in position as illustrated in Figure 3, the high voltage and low voltage leads 35 and 39 respectively extending from the coils are connected to the bushings, and the upper core housing 38 is placed in position. The entire transformer structure is now secured and clamped together by means of the clamping stud assemblies 40, one of which may be seen in Figure 3 extending substantially centrally vertically between the upper and lower core housings 38 and 34 proximate the front of the transformer. The clamping stud assembly 40 consists of a bolt 41 and nut 42 which draw the upper and lower core housings toward one another to thereby securely clamp the entire assembly together.

The upper core housing 38 is identically the same in configuration as the lower core housing 34, and Figures 4 and may be considered to equally well apply to the upper section of the transformer with the exception that, of course, the coil pressure pads 33 are replaced by the elements 36 and 37 of the bushing assemblies. Welded or otherwise secured to the ends of the upper core housing 38 are a pair of angle brackets 56 much the same as the angle brackets 54 associated with the lower core housing. The angle brackets 56 restrainingly engage an upwardly projecting shoulder 57 formed on the high voltage bushing element 36 to prevent the element 36 from tending to slip sideways out from under the vertical compressional clamping provided by the angle brackets 56. Similarly, a pair of projections 58 formed on the low voltage bushing assembly element 37 extend upwardly through complementally formed apertures in the front flange of the upper core housing 38.

Welded onto the front and rear faces of the upper core housing 38 are a plurality of lifting lugs 48 which are utilized during transformer installation to elevate the transformer upward and into position for mounting. Also welded or otherwise secured to the rear wall of both the upper core housing 38 and the lower core housing 34 are the support lugs 49, best seen in the showing of Figure 2, and it is these support lugs 49 which are em ployed to firmly secure the transformer in its installed position. The entire transformer assembly of Figure 3, secured together in the manner described, is then placed in a potting tank and completely encapsulated by a suitable plastic composition excepting for the lifting lugs 48, the support lugs 49 and the terminals of the high and low voltage bushings 43 and 44. The encapsulation of the transformer causes the plastic potting composition to pentrate into all of the openings of the assembly, as for ex ample into the upper and lower core housings 38 and 34, between the coil assemblies 20-20 and the core 30, resulting in a finished transformer which appears as illus trated in the showings of Figures 1 and 2.

Figure 6 illustrates a fragmentary sectional perspective view of the encapsulated transformer showing various of the parts described in connection with the showing of Figure 3 and their relative locations within the encapsulating plastic coating 28. The illustration of Figure 7 shows the two pre-formed coil assemblies on the core, and the detailed construction of an individual coil assembly 20 will now be described in connection with the showing of Figure 8 to which reference should be had.

The pre-formed coil structure of Figure 8 is built-up by first placing the high voltage winding 22 about the coil form 21 and then varnish dipping the high voltage winding 22 on its coil form 21 to provide the enclosing coating 23. Next, the low voltage coil form 24 is wrapped about the varnish dipped high voltage winding unit and the low voltage winding 25 is built-up. This entire build is now potted within the enclosing plastic coating 26. The insulating layer 27 is wrapped about the built coil structure which may then be assembled to the core in the manner already described. The final plastic coat 28 is that which results from the encapsulation of the entire transformer as also previously described. The coil form and insulating layers 21, 24 and 27 may typically be oneeighth inch thick silicone rubber made by the Dow Corning Company and identified as Silastic RTV, polyester glass laminate made by the Glastic Corporation and built-up to a thickness of one-eighth of an inch, or any other suitable material. The coil windings 22 and 25 may be made of copper or aluminum magnet wire or foil insulated with a class B or higher rated insulation. The varnish dip layer 23 could suitably be a ten mil maximum thickness layer of Westinghouse B-l varnish. The plastic potting layers 26 and 28 are preferably formed from a weather resistant insulating material of class B rating or higher, as for example the epoxy resin identified as Epon manufactured by the Shell Oil Company. The foregoing materials are, of course, listed merely by way of illustration, and other suitable materials may be just as readily employed depending upon personal preference or particular application.

The major transformer mechanical components illustrated in Figure 3, such as the upper and lower core housings 38 and 34, the angle members 55 and 56, clamping stud assembly 40, and lifting and supporting lugs 48 and 49 will generally be made of steel, whereas the high and low voltage bushing assembly elements with the exception of the terminals will generally be formed of porcelain, and the coil pressure pads 33 will be formed of a class B insulating material such as a polyester fiber glass.

Having now described my invention in connection with a particularly illustrated embodiment thereof, it will be apparent that variations and modifications will naturally occur from time to time to those persons normally skilled in the art without departing from the essential spirit or scope of my invention, and accordingly it is desired to claim the same broadly as well as specifically as indicated by the appended claims.

What is claimed as new and useful is:

1. An electrical power distribution transformer including a core having a pair of parallel extending legs, a pair of identical pre-formed coil structures each of which is disposed about a different one of said pair of parallel core legs, each pre-formed coil structure comprising a high voltage winding wound upon a first electrical insulator coil form and varnish dipped together to form a sealed unit, a second electrical insulator coil form wrapped closely about said sealed unit and a low voltage winding wound thereupon, said low voltage winding and second coil form and sealed unit being bonded together by a hardsetting plastic encapsulating composition to complete the said pre-formed coil structure, each of said pre-forrned coil structures being further wrapped with a barrier layer of electrical insulating material, said core and coil structure being oriented so that said coils extend in parallel side by side relationship to one another and the core extends both above and below said coils, the core portion extending below said coils being seatingly disposed within a core lower housing of U-shape in central crosssection having front and rear walls of substantially trapezoidal form with the shorter trapezoidal base located at the lower housing bottom and the coils being seated upon electrical insulator pressure pads supported by the lower housing, high and low voltage bushing mounting brackets of inverted L-shape seated upon the coils and held in position by a core upper housing identical in form with the core lower housing but of inverted position, and means clamping the upper and lower core housings to one another to thereby secure the aforesaid elements therebetween, said core housings both being open between the front and rear walls thereof, and the entire transformer being encapsulated within a weatherresistant plastic composition which fills all void spaces in the composite transformer structure.

2. The transformer according to claim 1 wherein said bushing mounting brackets of inverted L-shape include projections extending upwardly, and said core upper housing is formed with projection receiving openings within which said bracket projections are disposed, whereby said brackets are prevented from shifting laterally outward.

3. An electrical power distribution transformer comprising a transformer core, a pair of pre-formed coil structures disposed upon opposite side legs of said transformer core, the top and bottom portions of said core extending above and below said coils and said core and coils being banded together to form a composite core and coil assembly, an open frame clamping structure comprising an upper and a lower core housing disposed re spectively over those portions of the core extending above and below said coils, coil pressure pads disposed between said lower core housing and the bottom of said coils and upon which said coils are seated, terminal bushings mounting brackets seated upon the top of said coils and upon which said upper core housing is seated, means extending between said upper and lower core housings which draw the housings together and clamp the transformer securely into a single unit, and a weather-resistant plastic coating which fills all void spaces within the clamped transformer unit and surrounds it with an encapsulating protective coating.

4. The transformer according to claim 3 wherein said upper and lower core housings each have secured thereto a bracket for mounting the transformer in operating position.

5. The transformer according to claim 3 wherein said bushings mounting brackets are of inverted L-shape and include projections extending upward therefrom, and wherein said core upper housing is formed with projection receiving openings within which said bracket projections are disposed, whereby said. brackets are prevented from shifting laterally relative to said core upper housing.

6. The transformer according to claim 3 wherein said core lower housing is of U-shape in central cross-section having front and rear walls of substantially trapezoidal form with the shorter trapezoidal base being located at the lower housing bottom.

7. An electrical power distribution transformer comprising a transformer core, a pair of pre-formed coil structures disposed upon opposite side legs of said transformer core, the top and bottom portions of said core extending above and below said coils, the core portion extending below said coils being seatingly disposed within a core lower housing of U-shape in central cross-section having front and rear walls of substantially trapezoidal form with the shorter trapezoidal base located at the lower housing bottom and the coils being seated upon electrical insulator pressure pads supported by the lower housing, high and low voltage bushing mounting brackets of inverted L-shape seated upon the coils and held in position by a core upper housing identical in form with the core lower housing but of inverted position, and means clamping the upper and lower core housings to one another to thereby secure the aforesaid elements therebetween, said core housings both being open between the front and rear walls thereof, and the entire transformer being encapsulated within a weather-resistant plastic composition.

References Cited in the file of this patent UNITED STATES PATENTS 2,464,029 Ehrman Mar. 8, 1949 2,549,309 Hill Apr. 17, 1951 2,646,535 Coggeshall July 21, 1953 2,916,713 Johnston Dec. 8, 1959 2,930,011 Wigert Mar. 22, 1960

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