US2934726A - Transformer lead supporting means - Google Patents

Description

April 26, 1960 B. A. BARENGoLTz 2,934,726

- TRANSFORMER LEAD SUPPORTING MEANS Filed Aug. 1, 1957 3 sheets-sheet 1 BY L April 26, 1960 Filed Aug. 1, 1957 B. A. BARENGOLTZ TRANSFORMER LEAD SUPPORTING MEANS s sheets-sheet 2 INVNTR. v ernara" arenyoZtz BY L Wbb@ April 26, .1960 B. A. BARENGOLTZ 2,934,726

TRANSFORMER LEAD SUPPORTING MEANS 3 Sheets-Sheet 3 Filed Aug. l, 1957 MK2/5ml.-

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lllll z y m y m a n. o w wn. w M w 6 m d w W l. ,f Am .w MY 5 MB d United States Patent() fi TRANSFORMER LEAD SUPPORTING MEANS Bernard A. Barengoltz, Pittsburgh, Pa., assigner to McGraw-Edison Company, Milwaukee, Wis., a corporation of Delaware Application August 1, 1957, Serial No. 675,594 7 Claims. v(c1. 336-192) power type transformer provided with a stacked type laminated magnetic core having aligned vertical legs, circular electrical coils of either the helical or the pancake type surround the -core legs. The electrical coils may comprise concentric primary and secondary windings, and the leads from the secondary windings may be brought up on one side of the core and coil assembly and connected to the low voltage bushings and to a terminal board carried on the upper side framemembers and which permits connection of the secondary windings of each phase in either series or parallel. The line and tap leads from the primary windings may be brought u-p on the opposite side of the core and coil assembly and connected to the primary bushings on the casing cover and to a tap changer carried on the upper side frame members. Conventionally the leads emerge from the circular windings and extend vertically upward in spaced relation to the coils to provide adequate breakdown insulation between leads and windings and between leads and ground. Conventional supporting means for the electrical 'leads may comprise a framework having wooden supports carried on and extending laterally from the side frame members and crossed horizontal and vertical wooden strips supported on the lateral members and joined together by metallic bolts and nuts. The metallic bolts and nuts in the region between the coils and the tank wall have sharp edges and distort the electrostatic field and cause high electrostatic voltage stress resulting in corona breakdown of the oil in the regions of high voltage gradient.

Electrical breakdown of windings of prior art transformers was oocassionally caused by nuts, bolts, and washers becoming loose due to shrinkage of the wood or vibration and falling into the electrical coils. In order to insure againstthis possible cause of winding breakdown, it has heretofore been necessary to peen each bolt to prevent loosening thereof, and this operation accounted for a large proportion of the time and labor required to assemble the electrical leads. Further, considerable time and labor was required to partially disassemble the wooden framework and clamp the leads temporarily in place in the steps of construction prior to final assembly. The prior art wooden lead supporting framework was displaced a sufficient distance outward from the circular electrical windings to provide adequate electrical breakdown strengthfbetween the leads and ground and between 2,934,726 Patented Apr. 26, 1960 the leads and the windings, and this construction resulted 1n a transformer tank of greater width and a consequent greater volume of oil than that required to provide adequate cooling for the transformer.

It is an object of the invention to provide improved means for supporting the electrical leads of power type transformers which permits a material reduction in the size of :the transformer casing and in the amount of oil in comparison to transformers having prior art lead supporting means.

Another object of the invention is to provide improved means for supporting the electrical leads of power type transformers which permits a considerable reduction in assembly time and labor in comparison to transformers having conventional lead supporting means.

It is avfurther object of the invention to provide improved means for supporting the electrical leads of power type electrical transformers which eliminates metallic objects and objects having sharp points between the coils and the tank Wall and results in a more uniform electrostatic field in this region than in transformers having prior ant lead supporting means.y

It is a still further object of the invention to provide improved means for supporting the electrical leads of power type electrical transformers which obviates the danger of bolts, nuts, and washers becoming loose and falling into the windings.

These and other objects and advantages of the invention will be apparent from the following description when taken in conjunction with the accompanying drawing wherein:

Fig. l is a horizontal sectional view through an encased electrical transformer having electrical lead support means in accordance with the invention, the view being taken below the tap changer and terminal board;

Fig. 2 is an elevation view of the core and coil assembly of the transformer of Fig. l taken from the side on which the leads from the low voltage windings are disposed;

Fig. 3 is an enlarged partial view of lead supporting means in accordance with the invention taken from the same side as Fig. 2 with portions broken away to better illustrate the construction;

Fig. 4 is a horizontal sectional view taken on lines 4-4 of Fig. 2;

Fig. 5 is a horizontal sectional view taken on lines 5 5 of Fig. 2;

Fig. 6 is an elevation view of the core and coil assembly of the transformer of Fig. 1 taken from the side on which the leads from the high voltage windings are disposed;

Fig. 7 is a horizontal sectional view taken on lines 7--7 of Fig. 6; and,

Fig. 8 is a horizontal sectional view taken on lines 8-8 of Fig. 6.

The preferred embodiment of the invention is illustrated as embodied in stationary induction apparatus of the power type encased in a generally elliptical tank 19 filled with a suitable cooling dielectric fluid 11, preferably trans former oil. The transformer core and coil assembly irnmersed in the cooling dielectric fluid 11 within the tank 10 includes a laminated magnetic core 12 of the stacked type having three aligned vertical legs 15 connected by upper and lower yokes 16. Channel iron upper and lower side frame members 20 and 21 respectively are disposed on opposite sides of and bolted to the upper and lower yokes 16. Pancake type electrical coils 22 surrounding the core legs 15 are supported on horizontally extending, semiannular lower supports 25 secured to the lower side frame members 21, and semiannular upper support plates 26 disposed against the upper end of the coils 22 are connected to the lower support plates 25 by lock strips 27 (see Fig. l), disposed between the legs 15 and the inner periphery of the coils 22 to clamp the coils 22 in an `axial direction. Radial spacers 2S arranged in circumferentially spaced apart positions insulate the coils 22 from the lower support plates 25, and similarly radial spacers 28 arranged in circumferentially spaced apart positions insulate the coils 22 from the upper support plates 26.

A terminal board 30 (a portion only being shown in Fig. 2) mounted on vertical insulating members 31, preferably of wood, supported on the upper side frame members 20 permits connection of the secondary windings of each phase in either series or multiple. A straight-line tap changer 32 (a portion only being shown in Fig. 6) is mounted on insulating bushings 35 carried on horizontally extending strips 36 which, in turn, are mounted on insulating blocks 37, preferably of wood, secured to the upper side frame members 20.

Each circular coil 22 comprises concentric primary and secondary windings. Insulated electrical leads 40 from the low voltage phase windings extend vertically upward on one side o-f the core and coil assembly (see Fig. 2)\ and are connected to the terminal board 3i). Similarly insulated line leads 411. and tap leads `41T from the high voltage phase windings extend vertically upward on the opposite side of the core and coil assembly (see Fig. 6) and are connected to the tap changer 32 and the high voltage bushings (not shown) on the transformer tank cover.

In prior ait transformers the electrical leads were supported on a framework of crossed vertical and horizontal wooden strips carried on wooden members secured to and extending laterally from the upper and lower side frame members. The wooden framework was displaced outwardly from the coils a sucient distance to provide adequate breakdown strength between the leads and the windings and between the leads and the core frame members, and this construction required a transformer tank of greater width than necessary to provide adequate cooling and consequently utilized an inordinate amount of transformer oil. The crossed wooden strips were joined by metallic bolts and nuts having sharp points which distorted the electric eld in the region between the coils and the tank and caused high electrostatic voltage stress which occasionally resulted in corona breakdown in the oil at points of high voltage gradient. Further, the nuts and bolts occasionally became loose due to vibration or shrinkage of the wood and dropped into the electrical windings where they caused electrical breakdown of the coils. In order to insure against this danger it has heretofore been necessary to peen each bolt to prevent loosening, and this operation was costly in both time and labor.

ln the improved electrical lead supporting means of the invention, any bolts and nuts which might distort the electrostatic held or fall into the electrical coils are eliminated, and the resulting core and coil assembly is appreciably narrower than transformers having prior art lead supporting means. Lead supports 44U and 44L are secured to the upper and lower side frame members 20 and 21 respectively at positions in the bight deiined by the diverging peripheries of the circular electrical windings 22. Each support 44 preferably comprises a foursided enclosure having opposed pairs or" vertical walls 45 and 46 (see Figs. 4 and 5) extending only to the edge of the supporting side frame member 2t) or 21. Although each support 44 may be an integral piece secured to a side frame member 20 or 21, in its preferred form each support 44 comprises a pair of metallic U-shaped, or channel, members 49 and 56 welded to a side frame member 20 or 21 with the open sides thereof facing each other. The supports 44 are illustrated with the opposed pairs of vertical walls 45 and 46 preferably arranged in a rectangle, but it will be `apparent that the brackets 49 and can be concave or of any desired inwardly curved shape which will form an enclosure for the leads 40 and 41. The U-shaped brackets 49 and 50 are welded to the side frame members 20 iand 21 in spaced apart relation lengthwise of the supporting side frame member 20 or 21 to provide an opening 51 in the wall 45 spaced from and parallel to the supporting side frame member 2i) or 21 through which electrical leads 4t) or 41 may be inserted into the support 44. In the illustrated embodiment the supports 44U secured to the upper side frame members 20 extend the entire height of the upper side frame members whereas the supports 44L secured to the lower side frame members 21 extend only a portion of the height thereof. inasmuch as the supports 44U and 44L do not extend beyond the upper and lower edges of the supporting side frame member 20 or 21 (e.g., a support 44U secured to an upper side frame member 29 does not extend below the frame member 2G), no insulation is required between the coils 22 and the supports 44.

Each pair of U-shaped brackets 49 and 50 supports secondary leads 4i) or primary leads 41 from one of the three phases. Three supports 44U are carried on each upper side frame member 20, but three supports 44L are provided on only the side frame member 21 on the low voltage side of the core and coil assembly. Two supports 44 are mounted in superimposed relation at one position between the circular coils 22, the rst set of U-shaped brackets 49 and 5t) being welded directly to the supporting side frame member 20 or 21 and the set of brackets 49 and 50 outwardly therefrom being Welded to the rst set of brackets. On the low voltage side of the illus trated embodiment shown in Figs. 2-5, three leads 4t) from each phase secondary winding are enclosed within a support 44L secured to a lower side frame member 21 and also enclosed within a Ysupport 44U welded to an upper side frame member 2t) directly above the lower support 44L. The leads 4t) are insulated from the U- shaped brackets 49 and 5i) forming the supports 44U and 44L by U-shaped, or channel, insulating pieces 53, preferably of pressboard, tting within the brackets 49 and 5t) and also by elongated T-shaped insulating pieces 54, also preferably of pressboard, disposed between the low voltage leads 40 and the U-shaped insulating pieces 53 and extending through both a support 44U and a support 44L and below the lower end of the coils 22. It will be apparent that the elongated T-shaped pieces 54 insulate between the leads 40 and the coils 22 and also insulate between the leads 40 of the two different phases at the position where two supports 44 are superimposed. Elongated insulating spacers 55 positioned between the low voltage leads 40 within each support 44 and extending through both the supports 44U and 44L provide desired insulating strength between the leads 40 of each phase. It will be apparent that the dimensions of the insulating pieces 53, 54, and 55 can be varied as desired to provide the required insulating breakdown strength between leads and between leads and ground. The crossbar portion 57 of the T-shaped insulating pieces 54 rests on the U-shaped insulating pieces 53 and prevents downward movement of the pieces 54.

The U-shaped brackets 49 and 50 provide a convenient means for temporarily positioning the leads 40 prior to final assembly, and after final assembly the T-shaped insulating pieces 54 prevent passage of the low voltage leads 40 through the opening 51.

Six leads 41T from taps on a phase primary winding and one line lead 41L are supported within each support 44U supported on the upper side frame member 20 on the high voltage side (see Fig. 6). Channel insulating pieces 6.0 are positioned within the U-shaped metallic brackets 49 and 50 on the high voltage side of the transformer, and elongated T-shaped insulating lstrips 61 extend through the supports 44U inwardly from the insulating channel pieces 60. An insulating tube 62 surrounding the primary line lead 41L within a channel gestage t insulating piece 60 insulates the primary line lead 411, from the tap leads 41T within the same support 44U, and elongated insulating spaces 65 disposed between the tap leads 41T and the T-shaped insulating pieces 61 and extending below the support 44U to the position wherein the tap leads 41T emerge from the coils 22 provide the required insulation breakdown strength between tap leads 41T and the coils 22. It will be apparent that in the final construction the insulating pieces 61 and`65 prevent passage of the primary leads 41L and 41T through the opening 51 in the wall 45 of the support 44U.

It will be appreciated that supporting of the secondary and primary electrical leads 40 and 41 is accomplished without the use of either metallic or non-metallic bolts having sharp points and that this construction (l) eliminates the major source of loosened nuts and bolts dropping into the transformer coils and causing breakdown as sometimes occurred in' transformers having prior art lead -supporting means, (2) eliminates a source of corona breakdown in the oil due to regions of high electrostatic voltage stress and results in a more uniform electric field between the lleads and the coils and between the leads and the smooth tank wall as well as between the coils and the smooth tank wall, (3) reduces the time required to assemble the electrical leads 40 and 41 which can be placed directly into the lead supports 44, whereas partial disassembly of the wooden framework of prior art lead supporting means was required in assembling the leads, and (4) obviates the necessity of peening each bolt which results in a saving of approximately fifty percent in the time and labor required to assemble the electrical leads.

The electrical leads 40 and 41 are dispo-Sed in the bight defined by the diverging peripheries of the circular windings 22 and do not extend, in a direction perpendicular to the side frame members 20 and 21, substantially beyond a vertical plane tangent to the three circular windings 22. It will be appreciated that by utilizing this space in the bight between the circular windings 22, which space was wasted in prior art constructions, the lead supporting means of the invention obviates the use of a supporting framework positioned laterally outward from the windings 22, thus permitting a tank of considerably less width than transformers having prior art lead supporting means and resulting in the saving of a substantial amount of transformer oil. In one model of transformer a reduction of approximately four inches in the width of the transformer tank and a saving of approximately in volume of oil was accomplished by use of lead supporting means in accordance with the invention.

While only a single embodiment of the invention has been illustrated and described, many modications and variations thereof will be .obvious to those skilled in the art, and consequently it is intended in the appended claims to cover all such variations and modifications as fall within the true spirit and scope of the invention.

I claim:

l. In an electrical transformer of the power type, ini combination, a casing, a magnetic core within said casing provided with a plurality of aligned vertical legs connected by upper and lower yokes, frame members secured to and disposed on opposite sides of said yokes, circular electrical coils surrounding said legs and protruding radially `beyond said frame members, a plurality of electrical leads including line leads from said windings extending upwardly on at least one side of the core and coil assembly, certain of said leads being at high potential when said transformer is energized, a plurality of lead supports secured to at least one of said frame members at positions between said circular coils, each support having spaced apart vertical walls defining an enclosure encompassing a plurality of said electrical leads and extending in a vertical direction only to the upper and lower edges of the frame member supporting it, one of said vertical walls having an opening therethrough permitting insertion and removal of said leads from said en- 6 closure, and means for insulating between said leads and for insulating said leads from said vertical walls including an insulating sheet disposed between said leads and said one wall obstructing passage of said leads through said opening, said leads being disposed in the bight defined by the diverging peripheries of said circular windlugs.

2. In an electrical-transformer of the power type, in combination, a casing, a magnetic core within said casing having a plurality of aligned vertical legs connected by upper and lower yokes, frame members disposed on opposite sides of said yokes, circular electrical windings surrounding said legs and protruding radilly beyond said frame members, a plurality of pairs of U-shaped metallic members secured to at least one of said frame members at positions between said circular electrical windings, said U-shaped members of each pair being disposed with the open sides thereof facing each other defining an enclosing support having spaced apart vertical walls and said U-shaped members being spaced apart lengthwise of said frame members to provideA an opening in the wall spaced from the frame member supporting said U-shaped members, insulated electrical leads including primary and secondary line leads from said electrical windings extending vertically upward on at least one side of said core and disposed within said enclosing supports, certain of said leads being at high potential when said transformer is electrically energized, said leads within each said enclosing support being positioned in the bight defined by the diverging peripheries of said circular windings, and means for insulating said leads from said walls of said enclosing support including sheet insulating material disposed between said electrical leads and said wall having said opening and obstructing passage of said leads through said opening.

3. In an electrical transformer of the power type, in combination, a casing, a magnetic core within said casing having a plurality of aligned vertical legs connected by upper and lower yokes, frame members disposed on opposite sides of said yokes, circular electrical windings surrounding said legs and protruding radially beyond said frame members, a plurality of pairs of U-shaped metallic brackets secured to at least one of said frame members at positions between said circular electrical' windings, said U-shaped brackets of each pair being disposed with the open sides thereof facing each other defining an enclosing support having spaced apart vertical walls and said U-shaped brackets being spaced apart lengthwise of said frame members to provide an opening in the wall spaced from the frame member supporting said brackets, a plurality of electrical leads including line leads from said electrical windings extending vertically upward and disposed within said enclosing supports, certain of said leads being at high potential when said transformer is electrically energized, said leads within said enclosing support being positioned in the bight defined by the diverging peripheries of said circular windings, and means for insulating between said electrical leads and for insulating said leads from the vertical walls of the support enclosing them including U-shaped insulating members nested within said U-shaped bracket and elongated sheet insulation members disposed inwardly of the legs of said U-shaped insulating members and between said electrical leads and said vertical walls, one of said sheet insulating members obstructing passage of said electrical leads through said opening, said sheet insulation members having laterally extending portions preventing downward movement of said sheet insulation members.

4. In combination with a power type electrical transformer having a magnetic core provided with a plurality of aligned vertical legs connected by upper and lower yokes, frame members secured to and disposed on opposite sides of said yokes, circular electrical coils having concentric primary and secondary windings surrounding said vertical legs and protruding radially beyond said frame members, terminal means disposed above said upper yoke, a plurality oi insulated electrical leads including line leads between said primary windings and said terminal means extending vertically upward on one side of said core and a plurality of insulated electrical leads including line leads between said secondary wind ings and said terminal means extending vertically upward on the opposite side of said core, a plurality of lead supports secured to at least one of said frame members at positions between `said circular coils, each said lead support having spaced apart vertical walls defining an enclosure encompassing a plurality of said leads, one of said vertical walls having an opening therethrough permitting passage of said leads, said vertical walls of each said support extending in a vertical direction only to the upper and lower edges of the frame member supporting it, and means for insulating said leads from said vertical walls including an insulating sheet disposed between said leads and said one wall obstructing passage of said leads through said opening, said leads within said supports being positioned in the bight delined by the diverging peripheries of said circular windings.

5. In a power type electrical transformer, in combination, a casing, a magnetic core within said casing having a plurality of aligned vertical legs connected by upper and lower yokes, frame members disposed on opposite sides of and bolted to said yokes, circular electrical coils including concentric primary and secondary windings surrounding said legs and protruding radially beyond said frame members, terminal means positioned above said upper yoke, a plurality of pairs of generally U-shaped members secured to at least one of said frame members at positions between said circular electrical windings, said U-shaped members being disposed with the open sides thereof facing each other defining an enclosure having spaced apart vertical walls extending in a vertical direction only to the upper and lower edges of the frame member supporting it and said U-shaped members being spaced apart lengthwise of said supporting frame member to provide an opening in the wall of said enclosure opposite to said supporting frame member, a plurality of insulated leads including line leads from said primary winding extending vertically upward through said enclosing supports on one side of said core and connected to said terminal means and a plurality of insulated leads including line leads from said secondary windings extending vertically upward through said enclosing supports on the opposite side of said core connected to said terminal means, said leads being positioned in the bight defined by the diverging peripheries of said circular windings, and means for insulating said leads from said walls of each said enclosing support including sheet insulating material disposedA between said leads and the wall having said opening and obstructing passage of said leads through said opening.

6. In combination with an encased electrical transformer having a magnetic core provided with a plurality of aligned vertical legs connected by upper and lower yokes, frame members disposed adjacent said yokes, electrical windings surrounding said legs and extending radially beyond said frame members, a plurality of electrical leads extending vertically on at least one side of said transformer, at least one metallic lead support welded to one of said frame members at a position between said windings, said lead support having opposed, spaced apart, vertical walls within the area generally defined by the diverging peripheries of adjacent ones of said electrical windings and a vertical plane tangent to said windings, all of said spaced apart walls of said lead support being integrally united and dening an enclosure encompassing a plurality of said vertically extending leads, whereby said lead support is free of connecting members with sharp ed-ges between said windings and the casing which would cause high electrostatic voltage stress and which might become loose and fall into said windings, and means for insulating between said vertical walls of said metallic lead support and said leads within the enclosure defined by said walls.

7. In combination with an encased electrical transformer having a magnetic core provided with a plurality oi aligned vertical legs connected by upper and lower yokes,

frame members disposed adjacent said yokes, electrical' windings surrounding said legs and extending radially beyond said frame members, a plurality of electrical leads extending vertically upward on at least one side of said transformer, and a lead support secured to one of said frame members at a position between said windings and having spaced apart vertical wall portions within the bight defined by the diverging peripheries of said winding, said wall portions of said lead support dening an enclosure encompassing a plurality of said vertical leads and said wall portions being integrally united with each other, whereby said lead support is free of connecting members with sharp edges between said windings and the casing which would distort the electric tield and which might become loose and fall into said windings.

References Cited in the file of this patent UNITED STATES PATENTS 1,386,828 Winston Aug. 9, 1921 FOREIGN PATENTS 296,852 Germany Dec. 28, 1915

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