GB2133523A

GB2133523A - Tank for oil-filled electric equipment

Info

Publication number: GB2133523A
Application number: GB08300428A
Authority: GB
Inventors: Takayuki Yamazaki; Hiromu Nishio; Akihiro Yamuguchi
Original assignee: Hitachi Ltd
Current assignee: Hitachi Ltd
Priority date: 1983-01-07
Filing date: 1983-01-07
Publication date: 1984-07-25
Also published as: GB2133523B; GB8300428D0

Abstract

A tank (11) for oil-filled electric equipment including an upper frame (12), a lower frame (13) and corrugated heat dissipating sheets (20, 21) mounted between corresponding sides of frames 12, 13 to constitute a shell. The tank further includes an upper junction plate (14, 14') and a lower junction plate (15, 15') extending sideways from frame 12 and frame 13 respectively in each corner, and a stanchion (16, 16') connected to plates 14, 14', 15, 15'. An upper edge and a lower edge of an extension (20b) of each sheet (20) and side sections (24 and 25) of the heat dissipating sheets (20, 21) bent in the direction of bulges (22, 23) of the sheets (20, 21) are oiltightly welded to plates 14, 14' and 15, 15' and the stanchion respectively as indicated at 26a, 26b, 26c and 26d. By this arrangement, the bulges (22, 23) of the sheets (20, 21) can be made to swell in balanced condition in each corner of the tank when the internal pressure of the tank increases. <IMAGE>

Description

SPECIFICATION Tank for oil-filled electric equipment FIELD OF THE INVENTION This invention relates to improvements in or relating to a tank for oil-filled electric equip ment provided with a shell formed by using corrugated heat dissipating sheets of high cooling efficiency produced by continuously bending thin steel strip material.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a front view of a transformer having a tank of the prior art using a corrugated heat dissipating sheet; Figure 2 is a transverse sectional view of the shell of the tank of the prior art; Figure 3 is a view showing, on an enlarged scale, the essential portions of the shell shown in Fig. 2; Figure 4 is a view in explanation of the deformation that the tank of the prior art might undergo due to the internal pressure; Figure 5 is a transverse sectional view of the essential portions of another example of tank for oil-filled electric equipment using a corrugated heat dissipating sheet of the prior art; Figures 6, 7 and 8 are a front view, a side view and a plan view respectively of the tank for oil-filled electric equipment comprising one embodiment of the invention;; Figure 9 is a sectional view of the essential portions taken along the line IX-IX in Fig. 7; Figure 10 is a sectional view of the essential portions taken along the line X-X in Figs.

7 and 9; Figure 11 is a fragmentary perspective view of the tank frame and the corrugated heat dissipating sheets; Figure 12 is a view showing the manner in which the lug is used; Figure 13 is a transverse sectional view of another embodiment of the invention; Figure 14 is a vertical sectional view of the embodiment taken along the line XIV-XIV in Fig. 1 3; and Figure 15 is a fragmentary perspective view of the tank frame and the corrugated heat dissipating sheets of the embodiment shown in Fig. 13.

DESCRIPTION OF THE PRIOR ART Fig. 1 is a front view of an oil-filled transformer using a tank of the prior art of the type described in the field of the invention, Fig. 2 is a transverse sectional view of the shell of the tank and Fig. 3 is a sectional view, on an enlarged scale, of a corner of the tank. The tank 1 shown in the figures comprises an upper frame 5 having flanges for mounting a tank cover 4, a lower frame 6 having a tank bottom plate secured thereto, and a shell constituted by a corrugated heat dissipating sheet 2 having a multiplicity of fin-shaped bulges 3 joined by welding at upper and lower ends to adjacent sides of the upper and lower frames 5 and 6. The shell has four corners 4 each of which is formed by bending the corrugated heat dissipating sheet 2 at a right angle or joining corrugated heat dissipat ing sheets 2 at ends by welding.

A tank using this type of corrugated heat dissipating sheet is mainly used with a me dium or small oil-filled transformer, to help obtain an overall compact size and a light weight in a transformer. However, when the tank is used with a transformer or other equipment of large capacity, limitations are placed on the height and number of the finshaped bulges of the corrugated heat dissipat ing sheet on grounds presently to be described and there have been restrictions to the attempt to reduce the size and weight of transformers or other equipment.

This type of tank has insulating oil filled therein for cooling and insulating the main body of the electric equipment, and is formed, depending on the use to which the tank is put, with a space for adjusting pressure, before being sealed. Thus when the tank is in use, a static force created by the head of the insulating oil and a dynamic force stemming from expansion of the volume of the internal air caused by a rise in temperature are exerted on the shell of the tank.

Fig. 3 shows the fin-shaped bulges of the heat dissipating sheet of a tank of the prior art being deformed by these interbal pressures, as indicated by dash-and-dot lines. The deformation manifests itself on opposed sides 3a of the adjacent fin-shaped bulges 3 symmetrically with respect to a point A as indicated by 8, and the deformation is rather low in magnitude.However, the fin-shaped gulge 3 located near the corner 7 has its side 3b facing the corner 7 show a deformation of higher magnitude as indicated by 82. For example, when an internal pressure of 0.1 kg/cm2 was applied to a tank provided with a corrugated heat dissipating sheet of a thickness t = 1.2 mm, a height of the bulges h = 315 mm, a breadth of the bulges b = 10.4 mm, a spacing interval between the bulges 1l = 37.5 mm, a distance from the corner 7 to the nearest bulge 12 = 50 mm, and a vertical length of the bulges 13 = 1 524 mm, the deformations were 8, = 10 mm and 82 were 20 mm.The deformation of the fin-shaped bulges increases with a rise in internal pressure until it exceeds the elastic limit of the material and permanent deformation sets in. Thus in a tank construction in which deformations vary from each other as indicated by S, and 82, it would be necessary to set an allowable range of internal pressures based on the value of 53.

The fact that the deformation Si and 82 of the fin-shaped heat dissipating sheet near the corner are in the relation 82 > 8r could be accounted for by the following hypothesis. As shown in Fig. 4, when an internal pressure of P per unit area is applied to each section of the corrugated heat dissipating sheet 2, a force M = p.a. (a is the pressure receiving area) would act on the sides 3a and 3b of the fin-shaped vulges 3. Let us discuss the moment around the center point A of a force M acting on the opposed sides 3 of the adjacent fin-shaped bulges 3.The moment of force acting on the opposed sides 3a would exert a force on the opposite side 3a that would cahcel out the force M, so that the deformations S, appearing in the opposed sides 3a would be symmetrical and reiatively low in value. However, the aforesaid force arising from the opposed sides 3a would not act on the side 3b facing the corner 7 of the finshpaed bulge 3 near the corner 7, and it would only be a force N applied to the pressure receiving surface of the corrugated heat dissipating sheet extending from the side 3b to the corner 7 that would oppose the force M.Thus the forces M and N would not balance because M > N, so that the deformations 8, and 53 would be considered to become 53 > 51. This tendency appears to be more marked when the ratio of the height h of the bulges 3 to the breadth b thereof increases in value. Thus if the distance 13 from the corner 7 to the nearest bulge 3 is made as large as the height h of the bulges 3, 8,~8,.

However, it would be necessary to reduce the heat dissipating area by reducing the number of the bulges 3 to bring about the relation 62~81 It will be appreciated that tanks for oil-filled electric equipment using corrugated heat dissipating sheets of the prior art are restricted in the height and number of the fin-shaped bulges of the corrugated heat dissipating sheet. Thus in medium and large type equipment of high heat loss generation in relation to the size (for example, it is over 750 KV A in an oil-filled self-cooled transformer), it is necessary to increase the length 13 of the finshaped bulges to ensure that the necessary cooling area is obtained.Moreover, when necessary to effect cooling, the dimensions x and y of the main body of the tank shown in Fig. 2 should be increased to increase the space ih which the corrugated heat dissipating sheet is mounted. The result of this would be that the dimensions and weight of the tank would increase, making it difficult to design an economically viable tank.

To cope with this situation, proposals have been made to use a junction plate 8 of the same shape and size as the fin-shaped bulges 3 of the corrugated heat dissipating sheet in each corner 7 of the shell of the tank as shown in Fig. 5 in such a manner that the adjacent sides of the shell are symmetrical to each other with respect to the junction plate 8 and extensions 9a and 9b of the junction plate 8 open at right angles are welded to the corrugated heat dissipating sheet 2 at welds 1 0a and lOb respectively.When this is the case, it would be possible to obtain a tank construction of balanced strength because when an internal pressure is applied to the tank, imbalance in the deformations S, and 82 of the fin-shaped bulges as shown in Fig. 3 could be wiped out by the relative actions of forces exerted on opposed sides of the finshaped bulge 3 of the corrugated heat dissipating sheet 2 and the junction plate 8. At the same time, the junction plates 8 serve as heat dissipating plates, thereby increasing the heat dissipating area of the shell of the tank.

However, this arrangement makes it impossible to make best use of the dead space at each corner of the tank.

SUMMARY OF THE INVENTION An object of this invention is to provide a tank for oil-filled electric equipment capable of preventing deformations of the corrugated heat dissipating sheets caused by the tank internal pressure from becoming unbalanced.

Another object is to provide a tank for oilfilled electric equipment enabling an overall contact size to be obtained in a tank of the type described without having any dead space.

The outstanding characteristic of the invention enabling the aforesaid objects to be accomplished is that a stanchion extending from each corner of the tank has joined to its sides in oiltight relationship end edge portions of extensions of the corrugated heat dissipating sheets constituting the shell of the tank.

DESCRIPTION OF THE PREFERRED EMBODI MENTS Preferred embodiments of the invention will now be described by referring to Figs. 6-12.

Fig. 11 shows in detail the tank according to the invention. The tank 11 comprises an upper frame 12, a lower frame 13, upper and lower junction plates 14 and 15, stanchions 16, and base members 17.

The upper frame 12 comprises L-shaped members arranged into a framework having longer and shorter sides and formed with a flange 18 serving as a seat on which a tank cover is mounted. The upper junction plates 14 each extending parallel to one of the longer sides of the upper frame 1 2 is constituted by an extension of the L-shaped member of the longer side of the frame 1 2 in each corner.

The lower frame 1 3 is formed by bending a steel sheet into a framework having longer and shorter sides and has a tank bottom plate 1 9 connected thereto in a unitary structure.

The lower frame 1 3 has in each corner a plate of the same thickness as the upper unction plate 14 joined thereto by welding to serve as the lower junction plate 1 5 extending parallel to the longer sides. The lower frame 1 3 is placed on the base members 1 7 comprising U-shape steels combined with one another.

The stanchions 1 6 of L-shaped cross section are each joined by welding to forward ends of the upper and lower junction plates 14 and 1 5 in such a manner that its longer side is located parallel to the shorter sides of the upper and lower frames 1 2 and 1 3 and its shorter side is located on an extension of the longer sides of the upper and lower frames 1 2 and 1 3. The stanchion 1 6 has its lower end joined by welding to the base member 1 7.It is to be understood that the invention is not limited to the L-shaped cross sectional shape of the stanchions 1 6 and that any shape of stanchions may be used so long as they each have two sides overlapping and joined to side sections 24 and 25 of corrugated heat dissipating sheets 20 and 21 presently to be described.

The frames 1 2 and 1 3 of the aforesaid construction have the corrugated heat dissipating sheets 20 and 21 attached to their four sides to provide a shell of the tank.

The corrugated heat dissipating sheets 20 and 21 are each formed with a multiplicity of fin-shaped bulges 22 and 23 formed by bending a thin steel sheet into a corrugation and welding the elevations of the corrugations at upper and lower ends to seal them after they are closed. The corrugated heat dissipating sheets 20 and 21 are formed with side sections 24 and 25 respectively at opposite ends which are substantially parallel to the finshaped bulges 22 and 23.

As shown in Figs. 6-8, the corrugated heat dissipating sheets 20 located on two of the four sides of the tank each have a breadth equal to the length x' obtained by adding the length I of the upper and lower junction plates 1 2 and 1 3 to the length of the longer sides of the upper and lower frames 1 2 and 1 3. The corrugated heat dissipating sheets 20 each have a central portion 20a superposed at upper and lower ends on the longer side of the upper and lower frames 1 2 and 1 3 and have upper and lower ends of left and right extensions 20b superposed on one side of the upper and lower junction plates 1 4 and 15, and they are joined together by welding in oiltight relationship.The corrugated heat dissipating sheets 20 each have left and right side sections 24 superposed on longer sides of the stanchions, and they are joined by welding at three end edges thereof in oiltight relationship.

The corrugated heat dissipating sheets 21 located on the other two sides of the tank each have a breadth equal to the length y' of the shorter sides of the upper and lower frames 1 2 and 1 3. The corrugated heat dissipating sheets 21 each have upper and lower ends superposed on the shorter sides of the upper and lower frames 1 2 and 1 3 and joined together by welding in oiltight relationship.

The corrugated heat dissipating sheets 21 each have three end edges of the left and right side sections 25 superposed on the other side of the upper and lower junction plates 14 and 1 5 and the shorter sides of the stanchions 1 6 located flush with the other side of the upper and lower junction plates 14 and 15, and they are joined together by welding in oil-right relationship.

Fig. 9 is a sectional view of the shell of the tank of the aforesaid construction taken along the line IX-IX in Fig. 7, and Fig. 10 is a sectional view taken along the line X-X in Figs. 6 and 9. In the figures, the numerals 26a and 26b are welds between the corrugated heat dissipating sheets 20 and 21 and the upper and lower junction plates 14 and 15, and the numerals 26c and 26d designate welds between the corrugated heat dissipating sheets 20 and 21 and the stanchion 16.

In the construction shown in Figs. 9 and 10, an oil passage 27 is defined in each corner of the tank which is surrounded on three sides by the upper and lower junction plates 14 and 1 5 and the stanchion 1 6 and covered on two sides by the elongation 20b of the corrugated heat dissipating sheet 20 and the side section 24 of the corrugated heat dissipating sheet 21. The oil flows through the oil passage 27 from the tank into the bulges 22 formed in the extension 20b of the corrugated heat dissipating sheet 20 and a gap between the side section 24 of the corrugated heat dissipating sheet 20 and the stanchion 1 6 as indicated by arrows in Fig. 9.

Thus when the tank is of the same external dimensions as the tank of the prior art shown in Figs. 1-3, the tank according to the invention has its heat dissipating area increased by an amount corresponding to the extensions 20b of the corrugated heat dissipating sheet 20, thereby making it possible to make use of the dead space in each corner of the tank to the utmost as a heat dissipating surface.

In addition, when the tank 11 has an internal pressure applied thereto, a force corresponding to the force M shown in Fig. 4 is exerted on the side sections 24 and 25 of the corrugated heat dissipating sheets 20 and 21 facing the oil passage 27, so that the moment of this force causes a force resisting the force M to act on sides 22b and 23b of the bulges 22 and 23 opposite the side sections 24 and 25 respectively. Likewise, a force resisting the force M acts on the side sections 24 and 25 from the sides 22b and 23b of the fin-shaped bulges 22 and 23 respectively As a result, deformations (swellings) substantially symmetrical with each other are caused to occur at the opposed sides of the fin-shaped bulges 22 and 23 and the side sections 24 and 25 respectively, and the deformation 82 is substantially equal to a deformation Si 2 = Si) occurring at the sides 22a and 23a of the fin shaped bulges that are opposed each other.

Thus the deformation 62 becomes markedly lower in magnitude than would be the case if no side sections 24 and 25 are provided, with the results that the tank according to the invention is free from the defects that deformations are unbalanced and the strength is lopsided. Additionally the limitations that have hitherto been placed on the number and height of the fin-shaped bulges of the tank of the prior art with a view to maintaining the strength of the tank at a desired level can be eliminated to a large degree and the heat dissipating surface can be further increased.

In the tank of the aforesaid construction, the stanchions 1 6 of high rigidity are mounted at four corners or at the outermost sides of the tank. By providing each stanchion 16 with a lug 28 and a pull hole 29 for pulling rollers and each base member 1 7 with a jack rest 30 on the undersurface thereof in a position for supporting the stanchion 1 6 as shown in Figs. 11 and 12, it is possible to prevent forces from becoming unbalanced when they are exerted on the tank in lifting the equipment, pulling same by rollers or pushing same upwardly with a jack. Thus crack formation in the weld beads causing oil leaks to occur can be avoided because no unbalanced forces are exerted on the corrugated heat dissipating sheets of the shell of the tank according to the invention.

As described hereinabove, the stanchions 1 6 are each provided with the lug 28 in an extension rising above the upper frame 1 2.

When a shackle 32 of a lifting rope 31 is hitched to the lug 28 as shown in Fig. 12, it is possible to prevent the lifting rope and the shackle from coming into contact with a tank cover 33 or upper strutures thereon, such as bushing, terminal box, etc.

In the tank of the prior art shown in Fig. 1 in which lugs 34 are located on the upper frame 5, it has been necessary to increase the height m of the upper frame 5 because of the need to hitch a rope to the lug 34. By providing the lug 28 to the upper end of each stanchion 1 6 as described hereinabove, it is possible to reduce the height m of the upper frame 1 2 (the value of m is 110 mm in the prior art but about 50 mm in the invention), enabling the height of the tank to be reduced and allowing the rigidity of the upper frame 1 2 to be incrased.This minimizes deformation of the upper frame 1 2 due to the internal pressure of the tank and reduces stresses developing in the welds between the upper frame 1 2 and the corrugated heat dissipating sheets 20 and 21, thereby increasing the withstand pressure strength of the tank.

The jack rest 30 is formed by cutting out a portion of the underside of each base member 1 7 contacting the ground to improve operability.

A comparison of the tank of the prior art shown in Figs. 1-3 with the tank according to the invention is shown in a table below by referring to oil-filled transformers of 3-phase, 1000 KV A.

Oil volume Weight Height (kg) (mm) Prior Art 865 3350 1735 The Invention 670 2920 1575 Rate (-)23% (-)13% (-)1OS/o Figs. 1 3-1 5 show another embodiment of the invention in which parts similar to those shown in Figs. 6-1 2 are designated by like reference characters. As shown in detail in Fig. 15, this embodiment of the tank in conformity with the invention comprises an upper frame 12, upper and lower junction plates 14' and 15', stanchions 16' and base members 1 7. The upper and lower junction plates 14' and 15' are formed integrally with the stanchion 16' to define therebetween a cutout 34.The stanchions 15' are each in the form of a letter L but its direction is in reverse to the L-shaped stanchion 1 6 of the embodiment shown in Figs. 4-12. The lower junction plates 15' are each secured in plate with its lower end portion being placed on the base member 1 7. The stanchion 1 6 of the L-shape in cross section has its longer side located parallel to the shorter sides of the upper and lower frames 1 2 and 1 3 and welded thereto through the junction plates 14' and 15' and has its lower end welded to the base member 1 7 on the surface of the latter.

In the tank 11 of the aforesaid construction, the corrugated heat dissipating sheets 20 and 21 are attached to the four sides of the frames 12 and 1 3 to constitute a shell of the tank 11.

The corrugated heat dissipating sheets 20 and 21 are each produced by bending a thin steel sheet in corrugation and elevations thereof are closed and welded together at upper and lower ends and have a multiplicity of fin-shaped bulges 22, 23, and side sections 24, 25 located at opposite ends of the heat dissipating sheets 20 and 21 which are bent to be substantially parallel to the finshaped bulges 22 and 23.

Fig. 1 3 is a transverse sectional view of the shell of the tank 11 of the aforesaid construction, and Fig. 14 is a vertical sectional view of the shell of the tank taken along the line XIV-XIV in Fig. 1 3. In the figures, the numerals 26a' and 26b' designate welds between the corrugated heat dissipating sheets 20 and 21 and the upper and lower junction plates 14' and 15', and the numerals 26c' and 26d' welds between the corrugated heat dissipating sheets 20 and 21 and the stanchion 16' respectively.

As can be seen in Figs. 1 3 and 14, an oil passage 27' is defined in each corner of the tank 11 which is surrounded on three sides by the upper and lower junction plates 14' and 15' and the stanchion 16' and covered on two sides by the extension 20b of the corrugated heat dissipating sheet 20 and the side section 25 of the corrugated heat dissipating sheet 21. The oil in the tank 11 flows through the oil passage 27' into the bulges of the fin shape 22 formed in the extension 20b of the corrugated heat dissipating sheet 20 and a gap between the side section 24 of the corrugated heat dissipating sheet 20 and the stanchion 16'.This enables the heat dissipating area of the tank 11 according to the invention to be increased by an amount corresponding to the extensions 20b of the corrugated heat dissipating sheet 20 as compared with the tank of the prior art shown in Figs.

1-3, when the two tanks have the same external dimensions, thereby allowing the dead space at each corner of the tank of the prior art to be utilized fully as heat dissipating surfaces.

Additionally the embodiment of the tank 11 shown in Figs. 1 3-1 5 can achieve the same effects as described by referring to the embodiment of the tank shown in Figs. 4-12 when the internal pressure of the tank 11 is applied thereto.

From the foregoing description, it will be appreciated that the tank according to the invention is capable of eliminating the defects of the prior art of the deformation of the corrugated heat dissipating sheets due to the inernal pressure of the tank becoming unbalanced and minimizes limitations placed on the height and number of the fin-shaped bulges of the heat dissipating sheets with a view to maintaining the strength of the tank at a desired level. Also, the invention enables the heat dissipating area to be increased by mounting the corrugated heat dissipating sheets in the dead space at each corner of the tank of the prior art shown in Figs. 1-3. This allows the corrugated heat dissipating sheets of the type described to be used with the tanks of oil-filled electric equipment of medium and large capacities with excellent effects and makes it possible to obtain an overall compact size in this type of equipment.

Claims

1. A tank for oil-filled electric equipment comprising: an upper frame; a lower frame; and a shell constituted by a plurality of corrugated heat dissipating sheets each formed with a multiplicity of fin-shaped bulges attached to sides of said upper frame and lower frame; wherein the improvement comprises: an upper junction plate and a lower junction plate extending sideways from each corner of the upper frame and the lower frame respectively; and a stanchion connecting said upper junction plate and said lower junction plate together in each corner of the upper and lower frames and supported at a lower end thereof by one of base members; wherein an extension of said corrugated heat dissipating sheet mounted between corresponding sides of said upper and lower frames and a side section bent to be substantially parallel to fin-shaped bulges of said corrugated heat dissipating sheet are superposed on one side of said two junction plates and one side of said stanchion respectively and end edges thereof are oiltightly joined together by welding, and a side section bent to be substantially parallel to fin-shaped bulges of other said corrugated heat dissipating sheet mounted between other corresponding sides of said upper and lower frames is superposed on the other side of said two junction plates and the other side of said stanchion and end edges thereof are oiltightly joined together by welding.

2. A tank as claimed in claim 1, wherein said upper and lower junction plates extend substantially parallel to one side of said upper and lower frames.

3. A tank as claimed in claim 1 or 2, wherein said upper junction plate and said lower junction plate extend from one corner of said upper frame and said lower frame respectively a distance substantially equal to the distance covered by the bulges of said corrugated heat dissipating sheet extending hori zontaily from the upper and lower frames.

4. A tank as claimed in any one of claims 1-3, wherein said upper junction plate and said lower junction plate are formed integrally with said stanchion.

5. A tank as claimed in any one of claims 1-4, wherein said stanchion extends upwardly from said upper frame and is formed with a lug at its upper end portion.

A tank for oil-filled electrical equipment, such tank being constructed and arranged substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.