US3496502A - Means for enclosing transformers - Google Patents

Description

B. MocRE MEANS FOR ENCLOS ING TRANSFORMERS Feb. 17, 1970 4 Sheets-Sheet 1 Filed June 14, 1967 .Eue// Moor e INVENTOR. M 16 A14 1 A Feb. 17, 1970 B. MOORE 3, 0

MEANS FOR ENCLOSING TRANSFORMERS Filed June 14, 1967 4 Sheets-Sheet 2 /I 6 J .5ae// Moore 22 INVENTOR.

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Feb. 17, 1970 a. MOORE MEAN; FOR ENCLOSING TRANSFORMERS 4 Sheets-Sheet 3 Filed June 3.4. 1967 0 2 W a w 2 a 6e m m L K MV m a 9 u /0 #5 w 8 k.

BY flwa, 4m,

United States Patent O 3,496,502 MEANS FOR ENCLOSING TRANSFORMERS Buell Moore, Houston, Tex., assignor to Esquire, Inc., a corporation of Delaware Filed June 14, 1967, Ser. No. 645,994 Int. Cl. Htllf 27/02 US. Cl. 336-59 6 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND A transformer, generally speaking, is an electrical device which is used to interlink a couple of independent electrical circuits with mangetic flux to affect a change from one voltage to another voltage. Various types of transformers are in common used and have been for a great many years. Most conventional power transformers comprise coils which are wound around a comparatively straight core portion. However, so-called toroid transformers, or those having a coil with a core in the shape of a toroid, are known and are generally accepted as being more efiiecient than the more conventional transformers.

All transformers generate heat, and the dissipation of the heat losses is of extreme importance in all transformer design. The amount of heat generated, of course, is dependent on the size and configuration of a transformer. But the heat dissipation is important in every case.

As a matter of fact, the rating of a transformer is determined by the rise in temperature of a transformer when delivering a given load. Consequently, more rapid dissipation of heat losses will result in a higher rating for a transformer of any given size. By the same token, more rapid dissipation of heat will allow reduction in size of a transformer having a certain kilovolt-arnpere rating.

In brief, it is will established tht the efiiciency of a transformer rapidly decreases as the temperature rises.

Those skilled in the art have long recognized that proper cooling is perhaps the single most important factor in transformer design. Therefore, it is not surprising that many attempts have been made to solve the transformer cooling problemwith varying degrees of success. For example, in many prior art structures, the transformer is merely deposited in an enclosure which is generally open to air flo-w, the air completely surrounding the transformer. This arrangement depends on air flow through the device for cooling and may provide sufficient cooling for a relatively short period of time. But it has been found that as air flows through such structures, dust and lint accumulate on the transformer and such dust and lint reduce the efliciency of the transformer operation. Such enclosures are supposed to be periodically cleaned, 'but because of their construction cleaning is difiicult and as a matter of practice is seldom done.

Thus, the solving of one problem creates another.

The prior art has not provided an apparatus suitable in all contexts for adequately and efficiently cooling toroid transformers.

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SUMMARY OF THE INVENTION This invention relates to transformer enclosures suitable for effecting rapid dissipation of heat from the transformers enclosed therein. More particularly, it relates to such enclosures which are effective for enclosing toroid transformers, and which include air channels open to the atmosphere at each end, which air channels extend through the core of the transformer. Such air channels promote a through fiow of air thus assuring rapid cooling of the transformer.

Further, the invention provides transformer enclosures wherein the transformers are encased in an encapsulating mateial that aids in the dissipation of heat by transferring heat from the transformer to the exterior surfaces of the transformer enclosure apparatus. Dust does not collect on the transformer because no part of the transformer is exposed to the atmosphere-rather the transformer is entiely surrounded by the encapsulating material.

The invention also relates to a transformer enclosure apparatus which is air tight and suitable for use in environments which are subject to flooding.

Further, the invention provides a transformer enclosure which incorporates the advantageous features listed above in combination.

BRIEF DESCRIPTION OF THE DRAWINGS In order that the invention might be understood in greater detail, certain specific embodiments are illustrated in the accompanying drawings which form a part of this specification and where in:

FIGURE 1 is a top perspective view of a transformer enclosure constructed in accordance with one embodiment of the invention;

FIGURE 2 is a view taken along the line 2-2 of FIG- URE 1;

FIGURE 3 is a partial elevational sectional view illustrating one embodiment for connection of the top plate of FIGURE 1;

FIGURE 4 is a view taken URE 2;

FIGURE 5 is a view taken along the line 55 of FIG- URE 2;

FIGURE 6 is an exploded pictorial view illustrating the various parts of the apparatus shown in FIGURE 1, and a transformer suitable for being enclosed in the apparatus;

FIGURE 7 is a top perspective view of a transformer enclosure constructed in accordance with another embodiment of this invention;

FIGURE 8 is a view taken along the line 8-8 of FIG- URE 7; and

FIGURE 9 is a graph illustrating core loss by use of a prior art enclosure;

FIGURE 10 is a graph illustrating core loss by use Of another prior art enclosure; and,

FIGURE 11 is a graph illustrating core loss using an enclosure of this invention.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS The embodiments of FIGURE 1-6 Referring now in greater detail to FIGURES 1-6:

The transformer enclosure apparatus 10 is seen to comprise a shell whi h is suitable for encasing a transformer such as a toroid transformer constructed in accordance with my copending application Ser. No. 466,406, now abandoned. The shell is conveniently formed in two parts, a casing 14 of a configuration suitable for surrounding the transformer, and a frame member 12 adapted to matingalong the line 4-4 of FIG- ly fit against the top of the casing 14. The composite enclosure structure is so constructed, as =will be more fully explained below, so that while the transformer is not exposed to the atmosphere, air channels are provided which extend all the way through the enclosure so that efficient and economical cooling may be provided.

As previously stated, enclosures constructed in accordance with this invention will conveniently enclose transformers such as those described in my copending application Ser. No. 466,406. Such transformers are known as toroid transformers because of the shape of the transformer core, and an example of such a transformer is seen pictorially in FIGURE 6. Here the transformer 80 is seen to comprise generally a toroid core 82, and four similar coils 84, 85, 86 and 87 which are equidistantly spaced around the circumference of the core 82. Thus the center of each coil is one-quarter revolution, or disposed at an angle of 90, from the center of the two adjacent coils, and one-half revolution, or 180', from the center of the diametrically opposite coil.

The casing 14 comprises a hollow generally cylindrical body 16 formed about an imaginary central longitudinal axis AA (FIGURE 2), and a stepped bottom portion formed by transverse annular plate 36, longitudinal annular plate 37, and transverse annular plate 24. The outer circumferential edge of the annular plate 36 is joined around its entire periphery to the body 16. The longitudinal annular plate is joined at the top thereof to the inner circumferential edge of plate 36, and at the bottom thereof to the outer circumferential edge of the plate 24, thereby forming a down step in the bottom of the casing 14. Each of said plates are joined around the entire periphery thereof.

The inner edge of the annular plate 24 (which may be of any suitable configuration such as circular or rectangular, but is square in this embodiment) defines an opening 26 about the central longitudinal axis AA. Joined to the inner edge of the plate 24 around the entire periphery of the opening 26, is an upstanding duct 28 of a transverse cross-sectional configuration similar to that of the opening 26. This duct desirably extends only a short distance upward from the bottom plate 24.

As is readily seen in FIGURE 6, the top of the casing 14 is open.

Equidistantly spaced around the circumference of the body portion 16 of the casing 14 (i.e., at one-quarter revolutions around the body) are four legs 18, 19, 20, and 21, which are generally parallel to the longitudinal axis AA and project radially outwardly from the body 16. The legs 18, 19, 20, 21 are generally three-sided members opening toward the axis AA, of a size suitable for retaining the coils 84, 85, 86, 87 of the transformer 80. Like the remainder of the casing 14, the legsare open at the top but are closed at the bottom by a transverse bottom plate 25 which is flush with the bottom plate 24.

Attached to the bottom plate 25 beneath the legs 18 and 21 is a support rail 22 of [-shape cross section, and attached to the bottom plate beneath the legs 19 and 20 is a support rail 23 which is in this embodiment generally parallel to the rail 22. These rails allow the apparatus to be placed in a level position sufliciently removed from a floor or base 27 to allow air passage underneath the apparatus.

Referring again to FIGURES 2 and 6, the frame member 12 is seen to be symmetrical about a central longitudinal axis AA, and may be seen to comprise a generally box-shaped portion having side wall 48, an open top, and a generally open bottom. Although the side wall 48 might be of any suitable configuration such as circular or rectangular, the present embodiment provides a side wall of generally square configuration. It is necessary, of course, that the overall frame member 12 be of such a size and configuration so that it will mate with the casing 14.

Afiixed to the generally open bottom of the frame 12 are a plurality of radially extending ducts 38, 39, 40

and 41, which converge at a point on the central axis AA of the frame 12. These ducts are each closed along the top, bottom and sides thereof but are open at each end to form radial channels 42, 43, 44 and 45 through which air may flow from the atmosphere surrounding the apparatus. Any suitable number of such ducts may be provided.

At an opening in the bottom portion of the ducts 38, 39, 40 and 41 at their convergence at central axis AA is a longitudinal duct 34 which in this illustrated embodiment is of square cross-sectional configuration corresponding to the upstanding duct 28 on the bottom of the casing 14. ,The top of the duct 34 thus opens into each of the channels 42, 43, 44 and 45.

Oppositely disposed in the side wall 48 of the frame 12 are a couple of outlets 46 and 47. These outlets serve as means for placing the primary and secondary leads from the terminals inside the transformer enclosure apparatus to the exterior thereof.

When the frame 12 is positioned on top of the casing 14 in mating engagement therewith, a conduit 30 which is desirably flexible is placed one end over the upstanding duct 28 and one end over the longitudinal duct 34 to form a longitudinal passageway 32 extending along the central axis AA through the center of the transformer enclosure apparatus 10. It will be recognized that the conduit 30 should be of a suitable configuration at each end for mating with each of the ducts 28 and 34. In accordance with this embodiment, that configuration is of square cross section. It must be a non-conductor and should fit tightly against each of the ducts 28 and 34, and may desirably be constructed of fibrous material or extruded synthetic polymeric material.

It will be readily understood that the longitudinal passageway 32 and the radial channels 42, 43, 44 and 45 serve a very useful and most advantageous function. Namely, each of these channels which is open at each end to the atmosphere on the exterior of the apparatus provides a through air draft which promotes cooling of the transformer. As noted above, this is very important to the efficient operation of the transformer, and the cooling provided in this manner is superior to any such cooling available in the prior art.

The top of frame member 12 is constructed to receive a cover plate 50 suitable for covering the open top of the apparatus. One suitable construction is the embodiment illustrated in FIGURE 3. Here it is seen that the inner wall ofthe side 48 of frame member 12 includes near the top thereof an annular plate 52 of L-shape cross section which extends around the entire periphery of the side 48. One side of the L-shape plate is affixed fiush with the inner wall of side 48 just below the lip thereof as by welding as illustrated by the weld 54. The other side of the L-shape plate forms a ledge which extends a short distance from the side 48 toward the central axis A--A. This side of the plate 52 has a rim 56 aflixed to the upper part thereof as by welding as illustrated by the weld 58. The rim 56 extends upwardly from the plate 52 a distance corresponding to the upward extension of the side 48 above the plate 52, thereby forming a groove 98 suitable for retaining a suitable gasket 66. Radially inward-1y from the groove 98, the plate 52 has a hole 60 therein suitable for receiving a bolt.

The cover plate 50 is of a size and configuration corresponding to the open top of the frame member 12 as determined by the uppermost portions of the wall 48. In the center thereof, it advantageously includes an opening 68 for facilitating entry into the top of the apparatus. Around the perimeter thereof spaced from the outer edge of the plate a distance corresponding to the distance bolt holes 60 are spaced from the edge, are a plurality of holes 62 also of a size convenient for receipt of a bolt connector. When the cover plate 50 is positioned in place on the top of the apparatus 10, the openings 62 line up longitudinally with the holes 60, and then bolts 64 and nuts 65 are placed therein to firmly hold the cover plate on the apparatus. It is apparent from this arrangement that the plate 50 fits over the gasket 66 in such a manner that an air-tight connection is assured.

Similar bolt and nut arrangements may be used to retain a plate 70 over the opening 68 in the center of the cover plate 50. In this connection, the bolts are illustrated at 96 in FIGURE 1.

In this manner, an air-tight terminal chamber is provided. It is pointed out that the transformer enclosures constructed in accordance with this invention are fluid tight and may be used in areas which are susceptible to flooding. This is a distinct advantage and a safety feature which is unavailable with many prior art structures.

Instead of the specific embodiment of frame member 12 shown here, a circular frame member may be provided. In many respects, a circular frame member allows use of gaskets which provide greater seal effectiveness.

By a method which will be explained in detail below, an encapsulating material 88 is placed in the interior of the casing 14 completely surrounding the transformer 80 therein, and extending into the lower portion of the frame member 12. Terminals 72 and 74 for the primary and secondary coils are supported in the encapsulating material 88 at the upper level of the material. Leads 76 and 78 connect the coils with the terminals 72 and 74, respectively, and leads 90 and 92 connect the terminals 72 and 74, respectively, with the exterior of the apparatus through the outlets 47 and 46. A fluid-tight chamber 94 void of encapsulating material is provided in the frame member 12, this portion of the apparatus holding the terminals 72 and 74.

The encapsulating material aids in the transfer of heat from the transformer to the outer surface of the apparatus. A large surface area, aided by the various air channels through the apparatus, promotes rapid dissipation of heat and consequent eflicient operation of the transformer.

METHOD OF ASSEMBLING THE APPARATUS The assembly of the apparatus may best be understood by reference to FIGURE 6. The support rails 22 and 23 are first affixed to the casing 14, and the appropriate interconnections of the leads 76, 78, 90, 92 and terminals 72 and 74 are made on the transformer 80. The transformer 80 is then lowered into position in the casing, the coil 84 fitting in the leg 18 of the casing, the coils 85, 86 and 87 fitting in the legs 19, 20 and 21 respectively. The bottom of the toroid core 82 rests on the annular plate 36 at the bottom of the casing, as best seen in FIGURE 2.

The conduit 30 is then affixed to the upstanding duct 28, and the frame 12 is then positioned in place on the casing 14, with the longitudinal duct 34 fitting into the top of the conduit 30.

The encapsulating material is then introduced into the apparatus. Any suitable encapsulating material might be used, one such suitable material being a mixture of about 75% rock aggregate and about 25% polyester or epoxy resin. Specifically, one illustrative example used by applicant is comprised of about 75% rock aggregate and about 25% of the epoxy resin Shell No. 815, which is available from the Shell Chemical Company. The rock aggregate is first poured into the apparatus to a level just below the terminals 72 and 74, and the resin is then added, the resin filling the voids between the rock aggregate particles.

A vacuum is then conveniently drawn in the apparatus to remove air bubbles from the encapsulating material and to guarantee a homogenous mass. The edge surfaces on the exterior of the apparatus may then be suitably sealed if desired and the exterior may be painted for esthetic appeal.

The embodiment of FIGURES 7 and 8 A three-phase transformer enclosure 100 is illustrated in FIGURES 7 and 8, the apparatus resembling in many 6 details the transformer enclosure of the FIGURES l-6 embodiment, and therefore reference may be made to the discussion of that embodiment for details of construction.

The transformer enclosure apparatus is comprised generally of a longitudinal shell 102 disposed about a central axis B-B. The shell 102 is in this instance a one piece structure in contrast with the two piece structure of the enclosure 10 of the FIGURES 1-6 embodiment.

The shell 102 is comprised generally of a top portion 114, bottom portion 112, a side wall 116 which is wrapped around a major portion of the circumference of the shell, to leave an open side 118. The opening along side 118 is covered by a suitably shaped cover plate 104, which is attached to the shell 102 by a connection 138 which may desirably be similar to the connection illustrated in FIG- URE 3.

The top portion 114 includes along the central longitudinal axis BB a longitudinal duct 122, and the bottom portion 112 includes a similarly shaped upstanding duct 120. A suitable conduit 128 similar to the conduit 30 of the FIGURES 1-6 embodiment is attached to the duct 120 at the bottom and the duct 122 at the top. This conduit and these ducts define a longitudinal passageway 108 extending completely through the transformer enclosure along the longitudinal axis BB.

The bottom of the apparatus may be disposed on suitable support rails such as the rail 106, and suitable outlet means such as the connection may be supplied to provide means for entry of suitable leads to the terminal plate, the terminals being illustrated as at 126.

As is apparent from FIGURE 8, three transformers having cores 130, 132, and 134 are stacked longitudinally in the enclosure 100 with their centers located on the axis BB. Encapsulating material fills an area surrounding the central axis BB and completely surrounding the transformers throughout the entire longitudinal length of the enclosure 100. A side portion 124 of the apparatus adjacent the cover plate 104 is not encompassed with the encapsulating material. In order to dispose the encapsulating material 136 in this manner, the material may be conveniently added while the apparatus 100 is positioned on its side 116 opposite the open side 118, and not set upright to the FIGURES 7 and 8 position until after the encapsulating material has hardened.

ADVANTAGES OF THE INVENTION It is readily seen from the description of the above embodiments that a transformer enclosure is provided wherein the transformer parts are not in contact with air in the enclosure. Therefore, they cannot collect dust.

Further, there is an air channel for draft cooling which extends through the transformer core in each instance and is open to the atmosphere at both ends. In this manner, effective cooling of the transformer core is facilitated. In one embodiment, additional air channels are provided above the transformer generally transverse to the first mentioned channel.

In addition, a transformer enclosure is provided wherein a material is in contact with the transformer which aids in transfer of heat from the transformer to the surface of the transformer enclosure. And the present apparatus provides great surface area for the dissipation of heat.

A transformer enclosure is further provided which is fully submersible and waterproof. Therefore, the invention provides a means whereby transformers may be used in environments subject to flooding which is much more economical and much more convenient than anything provided in the prior art.

As specific examples of the advantage in efiiciency provided by use of the present invention, reference is made to the three examples included below, which vividly demonstrate the improvement obtainable by use of the transformer enclosures as described herein.

' 7 EXAMPLE I Using a prior art enclosure which relies exclusively on air cooling, and using aBrand A 50 kva. transformer operating at 50 kva., the coil temperature and core loss performed in the following manner, illustrated in FIGURE 9, plotted as a function of time.

EXAMPLE 11 Using a prior art enclosure similar to that used in Example I, and a Brand B 50 kva. transformer operating at 50 kva., results were obtained according to FIGURE 10.

EXAMPLE III Using a transformer enclosure apparatus constructed in accordance with FIGURES 16, and using a 50 kva. Wide- Lite transformer operating at 50 kva., results were obtained according to FIGURE 11.

While the invention has been described in terms of specifically advantageous embodiments which constitute the best mode of the invention as known to the inventor at the date of this application, it is understood that various changes may be made in the structures herein illustrated without departing from the scope of the invention, which is defined by the following claims. For one example, it is noted that the terms such as top, bottom, upper, and lower, refer to the orientations illustrated, and are used for convenience of explanation only; they are not to be construed as limiting.

What is claimed is:

1. Apparatus suitable for enclosing a transformer having a generally toroid core, in a manner to insure rapid dissipation of heat, comprising:

a generally hollow shell extending about a longitudinal axis and encasing said transformer;

encapsulating material disposed in said shell completely surrounding said transformer, whereby no part of said transformer is exposed to the atmosphere, said encapsulating material being effective to transfer heat from the transformer to the exterior surfaces of said shell;

a fluid-tight chamber in said shell void of encapsulating material, said chamber having primary and secondary terminals disposed therein;

outlet means in the surface of said shell for communication of leads into said chamber;

a first longitudinal opening through said shell extending through the center of the toroid core of said transformer, said opening being exposed to the surrounding atmosphere at both ends thereof to assure free flow of air through said opening so as to facilitate cooling of the core; and,

at least one radial opening in said shell transverse to said first opening, said radial opening also being exposed to the atmosphere at both ends thereof, to assure free flow of air through said opening so as to facilitate cooling of said transformer whereby maximum cooling of said transformer is achieved, resulting in increased transformer efficiency.

2. Apparatus in accordance with claim 1, wherein said longitudinal opening is in communication with said radial openings.

3. Apparatus in accordance with claim 1, wherein said encapsulating material is a suitable resin-aggregate mixture.

4. Apparatus in accordance with claim 1, wherein said shell comprises:

a casing for holding said transformer,

a frame member for mating with said casing, said frame member including said fluid-tight chamber, and

a cover plate for covering said chamber.

5. Apparatus in accordance with claim 4, wherein said casing is symmetrical about said longitudinal axis, and the center of said toroid core is disposed on said axis.

6. Apparatus in accordance with claim 4, wherein a sealing gasket is disposed in said frame member adjacent said cover plate, whereby said apparatus may be safely used in an environment which is subject to flooding.

References Cited UNITED STATES PATENTS 2,668,947 2/ 1954 Stewart 33696 2,743,308 4/ 1956 Bandsley 33696 XR 3,024,43'4 3/1962 Carson 33696 3,030,597 4/1962 Piaia et al 336-96 XR 3,210,701 10/1965 Fastner et a1. 3'3696 3,317,796 5/1967 Thompson 336-5'9 XR THOMAS J. KOZMA, Primary Examiner US. Cl. X.R. 33696, 229

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