US1802678A - High-tension transformer - Google Patents

Description

April 28, 1931.

H. B. SMETH HIGH TENSION TRANSFORMER Filed Aug. 14. 1929 4 Sheets-Sheet l 16 i Kg;

9 10 g I 9 10 i 11 12 25 INVENTOR Apri1 2 8, 1931. H, B, mm 1,802,678

HIGH TENS ION TRANSFORMER Filed Aug. 14, 1929 4 Sheets-Sheet 2 INVENTOR @5445 JMZPZ H. B. SMITH HIGH TENSION TRANSFORMER 4 Sheets-Sheet I 3 April 28, 1931.

k Filed Aug. 14. 1929 April 28, 1931. a-a. B. SMITH HIGH TENSION TRANSFORMER- Filed Aug. 14, 1929 4 Sheets-Sheet 4 Patented Apr. 28, 1931 UNITED STATES PATENT OFFICE.

HAROLD B. SMITH, 0F WORCESTER, MASSACHUSETTS, ASSIGNOR TO WESTINGHOUSE ELECTBIO & MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA HIGH-TENSION TRANSFORMER Application filed August 14, 1929. Serial No. 885,943.

My invention relates to electrical translating devices, and it has particular relation to high-tension transformers.

It is the usual practice to immerse the windings and the associated magnetizable core structures of high-tension transformers in an insulating fluid, such as oil, in order that the proper insulation may be obtained between the windings and the core structures, and in order that the windings and core structures may be maintained comparatively cool.

Experience has demonstrated that a certain distance in oil ofa given quality will insulate for a predetermined voltage, but that, as the voltage is increased, the length of oil distance required increases at a greater rate. It is apparent that, as higher voltages are employed, the relative increase in space and volume required for oil is considerably greater and, consequently, the size of the transformer assumes very large or even prohibitive proportions.

This difliculty has, to some extent, been overcome by employing plates or barriers of conducting material, and of annular form,

surrounding the high-tension winding and subdividing the oil space into properly divided sections. With this construction, the layers of the dielectric are each worked at potential gradients approaching their dielectric strengths and suitable electrostatic densities, thereby increasing the insulating value of the oil and decreasing the total oil space and volume required.

It has been found that, at certain voltages and other conditions, a corona discharge occurs, under oil, in such apparatus, with the result that a certain amount of the insulating oil 'or other insulating material is decomposed, thereby causing the accumulation of deleterious substances which rapidly deteriorate the oil and other organic material. In addition to the decomposition of the insulating oil, there is an actualdeterioration of the other insulatingmaterial employed in the transformer.

By removing all sharp edges from the several structural elements and by interposing such suitable shieldsand flux distributors in the electric fields that the potential gradient between the several shields and distributors shall not exceedcorona-forming or incipient ionizing or corona values, the development of corona or incipient ionization or coronaforming potentials are prevented.

It is usual to build up the high-tension winding with flat pancake or cylindrical coils. The difference of potentialbetween adjacent coils is different at various parts of the coils, but the insulating space between the coils has been great enough to take care of the maximum potential difl'erence between the coils. Under these conditions, the dielectric is not 4 stressed uniformly and is not utilized to its greatest possible degree. It appears, with the present method of winding that the dielectric is utilized to only about fifty percent of its maximum theoretical value. There is a' large and increasingly important number of transformer applications where the currents are. relatively small and the voltages relatively high. If the cross section of copper appropriate to the relatively small current is used, the cross section of di-electric insulating space becomes of paramount importance. Inasmuch as the dimensions of a high-tension transformer depend, in general, upon the dimensions of the space occupied by the high-tension winding, and the total volume, weight and cost depend upon that space. it is highly desirable to pro-- duce a transformer in which the high-tension winding shall be as compact as possible.

An object of my invention is to provide a transformer of the above-indicated character that shall be simple, rugged, compact, easilymanufactured and adaptable for veryhighoil, using electric-flux-distributing shields for suppressing corona and incipient corona and ionization, and so arranging the coils of. the high-tension windings, that the insu lating space between adjacent coils is built up in direct proportion to the increase in voltage, that I have been able to greatly reduce the size, cost and weight of a transformer over that heretofore obtainable.

For a better understanding of my inrention, reference is made to the accompanying drawings, in which,

Figure 1 is a sectional elevational view of one embodiment of my invention;

Fig. 2 is a perspective view, on a reduced v scale, of a metallic potential-di'stributorv shield Fig. 3 is a sectional view of'a modified form of the upper turn of the high-tension winding;

' Fig. 4 is a view, partially in plan and pariially in section, of the transformer shown in Fig. 5 is a sectional elevational viewof one portion of the transformer windings;

Fig. 6 is a sectional view showing a portion of the high-tension winding employing a metallic shieldbetween the adjacent coils;

Fig. 7 is a perspective view of a machine suitable for producing the coils of the hightension winding, which is illustrated in Fig. 5,'and

Fig. of a coil and the manner in which it is sewed to a backing of insulating material.

Referring to Figs. 1, 4 and 5 of the drawings, my invention comprises,-in general, a

transformer 2 comprising a low-tension winding 3 and a high-tension winding 4 consisting of a plurality of coils 5 of flat conical form disposed concentrically about 'a core member 6 in such manner that each coil makes a definite angle with adjacent coils.. The several coils are provided, at their outer edges, with metallic potentialand flux-distributing members 7 of toroidal form. Nested metallic shields 8 of annular form are attached to certain of the metallic distributors 7, for distributing the potential and Ilux fields generated within the transformer. The shields 8 comprise cylindrical or annular portions 9 and bottom portions 10 which are separate and have, respectively, toroidal portions 11 and 12 which are electrically connected to each other when assembled. The distributing members 7, the annular portions 9 and the bottom portions 10, inside and outside the high tension winding 4, are split somewhere in their circumference, leaving an air gap 13, as illustrated in Fig.2, so as not to form short-circuited secondary turns.

The upper turn 14 of the high-tension winding consists of a semi-cylindrical tube composed of wood 15 and a sheet-metal outer cover 16 having a split somewhere in its cir- 8 is a detail view showing a portion 0 cumference to avoid forming a short-circuited secondary turn.

The upper turn 14 of the high-tension winding may comprise, as illustrated in Fig. 3, a plurality of. turns of pipe formed into a 'spiral that serves as a reactive inductance at the end of the high-tension winding to permit discharge of excess local potentials between turns of the pipe through the insulating fluid medium. The upper contour of the entire turn is curved so that, as in the case form, that are disposed in nested relation and project upwardly concentrically with the distributing terminal 17. The extensions 18 are severally connected to horizontally extending portions 19 that terminate in toroidal potential-and-flux-distributing members 20. The toroidal members 20 are disposed concentrically about the distributingv terminal 17 in such'manner that the potential gradient therefrom to ground or to each other is maintained below corona or incipient corona or ionizing potentials.

Concentric metallic shields 21 and 21a are provided above the winding 4 to sub-divide the oil space and to complete the shield around each section of the winding. The shields 21 and 21a, respectively, are electrically connected to corresponding cylinders 9 and thus have a space 22 between them to prevent a short circuit of a section of the wlnding 4. The shields 21 and 21a are supported by insulating spacing members 23 disposed at certain points around the core 6. To allow the c lindrical extensions 18 to extend upward y, the continuity of each shield 21 and 21a is'necessarily interrupted, thus preventingthe formation of short-circuited secondary turns.

Tapered spacing blocks 24 and 25 are placed between the shields 9 and the shield extensions 18. at certain points around the periphery to hold them in spaced relation, the blocks associatedwith the left-hand portion of the shield being omitted for. clarity. Spacing blocks 26 are employed at certain points between the horizontally extending portions 19, the ones to the left of the terminal 17 being omitted for clearness. Wooden or other dielectric supporting members .27 surround the core ,member and serve to support the v shields 8 and space them apart.

connected, by a suitable conductor 28, to

ground, thereby grounding that terminal of the high-tension winding 4. The uppermost fiat conical coil 5 is connected directly to the upper turn 14, and the latter is connected to. the distributing terminal 17, thereby placing the several coils 5 and the turn 14 in seriescircuit relation between the terminals 17 and 28.

'The several coils 5 are formed of suitable very small wire on a backing of Fuller board 29 or the like,in a manner described heretube 7 are all tied matter. The coils are. maintained at a definite angle to each other and at the angle at which they are wound and sewed by radial Wedge shape insulating members 30 which are inserted betweenthe coils at certain intervals. Disc members 31 of insulating material extend around the core member between adjacent coils at the place of their greatest divergence; The disc members 31 are held in slots in the wedges and extend approximately more than one-half the distance inwardly toward the junction point of the adjacentcoils. The adjacent coils 5 are maintained at such an angle that the space between corresponding turns of the coils is great enough to insure with the discs and flux distributors su cient insulating space between them. The disc members 31 may be employed to reduce the insulating space needed at the point of greatest potential difference, thereby reducing the size of the high-tension windmg.

At the end of the wedges 30, the two coils 5 on the Fuller board 29, the two pieces of Fuller board and the flux-distributing together by tape passing through holes in the wedge and- Fuller board in a region at a given potential and 0 without any difference of potential between these points. This holds the radial wedge 30 in position without fastening at the thick ends of the Wedge, where the maximum difference of potential exists. It will be observed that every turn of each coil is exposed to free circulation of oil, and the construction is such that any slight heating effect will facilitate such circulation and free the coils from any small air bubbles or particles of moisture.

,Flat metal annular plates 32 split some where inthe circumference to prevent forming a short-circuited secondary, may be employed instead of the disc members 31. The annular plates 32 extend inwardly to the junction point of the adjacent coils and are held bytwo triangular shape insulating members 33 that are substituted for the wedge-shape members 31. At the junction point, the two coils 5, the two pieces of Fuller board 29, the triangular shaped members 33 and the fluxdistributing tube 7 are all connected together. The inner and outer edges of certain or all of the coils 5 are provided with toroidal distributors 7, in order to distribute flux andpreventthe accumulation of coronaforming potentials at the edges of the several coils 5. The distributor 7 may or may not constitute the outer turn of the winding 5, as desired, and it may also be omitted when possible.

Vith this construction, the insulating space is directly proportional to the potential difference between coils at any point, and the dielectric is stressed with a close approach to absolute uniformity throughout the stack of coils 5 from terminal 17 to terminal 28. That is, I utilize the insulating space to its maximum efliciency,thereby reducing to a minimum, the amount of high-tension-Winding space for a given quality of dielectric at a predetermined high voltage.

Referring to Fig. 7 of the drawing, the apparatus for winding the coils comprises a table 34 for holding the coil and the Winding equipment, although any suitable base may be employed, a motor-driven sewing machine 35 that is adapted for zig-zag stitching, guide members 37. 38 and 39 and spools of winding Wire 40 and insulating cord 41 suitably attached to a leg of the table 34 by a support 42.

The guide'member 37 comprises two pulleys 43 and 44 rotatably mounted on a bolt 45 that is secured to the table 34. The guide member 38 comprises an arm 46 suitably attached to a motor support 47 holding a roller 48. The guide member 39 comprises a plate 49 having a recess extending longitudinally therethrough of sufiicient size to accommodate the wire 40 and the insulating cord 41.

on a pro ection 56 which extends upwardly from the table 34. A pluralitv of radial arms 56a extend outwardly from the center of the plate 55, holding two flat annular members 57 having the rim of an annular member 58 of Fuller board, or similar material, disposed therebetween and held tightly together by bolts 59 and nuts 60. A plurality of rollers 61 are disposed under the Winding frame to facilitate the movement thereof. The frame 54 is made of such size that the inside diameter of the Fuller board is suitable for mounting in the transformer.

I the table to hold the edge of the uller board 58 up and prevent it from extending over Rollers 62 pro ect vertically u ward from mined distance from the edge of the annular members 57. The winding wire 40 and the insulating cord 41 are then fed, as indicated in Fig. 7 over the pulleys 43 and 44, respectively. under the roller/48 and the guide memher 39 and are sewed tothe Fuller board; As soon as the first turn of the wire and 1nsulating cord are sewed, the second turn of each is sewed to the first turn and to the moves away Fuller board, the ordinary feed mechanism of the sewing machine serving to rotate the disc and automatically wind the spiral.

Sometimes it may be necessary to provlde an auxiliary drive for the disc. For this purpose, I have provided a motor 64, mounted on a bracket 65 attached to a leg of the table 34. A belt 66, passing over the pulleys 67, located in the table, serves to connect the pulley of the motor-64 and the center plate 55. Insewing the wire and the insulating cord to the Fuller board, the thread passes over several turns of each, extends through the insulating cord, loops through the Fuller board and passes over several more turns in zig-zag shape, substantially as shown for an insulated conductor in Fig. 8. Astbe sewing process is continued, the sewing needle from the center of the coil 'to adjust itself to the increasing diameter of the coil. When the coil is completed, the flat annular members 57 are taken, apart and the coil removed. The portion of the frame '54, except the Fuller board, may be used again in winding other coils.

When it is desired to make the coil of insulated conductor, the insulating cord 41 'is omitted and, in stitching, the thread passes over several turns of the insulated conductor, extends through the insulation, loops through the'Fuller board and passes over several more turns of the coil, similarly to the operation hereinbefore described.

The axis of the frame 38 may be placed at any angle with the sewing machine that is desired by change inthe angle of the winding table or machine or both. This permits the production of a coil of a single layer with any angle desired for the conical surface of the coil, from flat pancake coils illustrated in this embodiment to fully cylindrical coils. The important angles for such conical windings are those approaching the plane flat coil illustrated herein, or those angles approaching a cylinder, either of which may be wound on this machine.

From the foregoing description, it will be apparent that I have provided a high-tension transformer in which the space required for the high-tension winding is materially reduced, thereby makingthe transformer more compact andeconomica-l.

The accompanying descriptionand illustration are merely illustrative and are not to be construed in a limiting sense. Since many modifications, within the spirit and scope of my invention, may occur to those skilled in the art, I do not wish to be limited otherwise than by the scope of the appended claims.

I claim as my invention:

1. In a transformer, a magnetizable core member, a plurality of windings surrounding said core member and submerged in an insulating fluid, one of said windings com prising a plurality of coils, each coil disposed at an angle to the adjacent 0011 so that the dielectric between said coils is stressed uniformly, a potential-control and flux-distributing means of annular form attached to each pair of, coils atthe point of zero-potential difl'erence between the coils, and potential-control and flux distributing shields electrically associated with certain of said annular dissulating barrier disposed between adjacent coils at the point of greatest divergence and extending toward the apex of the two coils for a certain distance, the end coil having a contour, the general radius of curvature ofwhich is such that the potential gradient at or near its surface is less than will causeincipient corona or ionization, said end coil comprising a helix of tubular conducting material.

3. A high-potential winding, comprising a plurality of circular coils disposed in vertical alinement and at such an angle to each other that the dielectric stress between adjacent coils is substantially uniform, an insulating barrier disposed between adjacent coils at the point of widest separationand extending inwardly toward the apex of the two adjacent coils, radial wedges disposed at certain points aI'OllIkd the coil for maintains ing the coils at the desired angle, the end turn having a contour, the radius of curvature bf which is such that the potential gradient at or near its surface is less than will cause incipient corona or ionization.

4. A coil for electrical apparatus comprising a series of convolutions of insulated wire disposed in a single plane, the successive convolutions of the insulating covering being sewed to each other and to a backing member of insulating material by zig-zag stitches constituting a spiral.

5. A coil for electrical apparatus comprising a series of convolutions of insulated wire disposed in a single plane, the successive convolutions of the insulating covering being sewed to each other and to a backing member of insulating material by zig-zag stitches constituting a spiral.

6. A coil for electrical apparatus comprising a series of convolutions of insulated wire forming a conical surface, the successive convolutions being sewed to each other and to a backing member of insulating material by zig-zag stitches and constituting a conical spiral.

7. A. coil comprising a spiral of smallgauge insulated wire, the successive turns of the insulation being sewed to each other and to an insulating backing member by zig-zag stitches constituting a spiral.

8. The method of forming a coil for electrical apparatus which consists in attaching one turn of said coil to a base and attaching each successive turn to the turn or turns next preceding it and to the base by zig-zag stitches.

9. The method of forming a coil for electrical apparatus having a plurality of convolutions of insulated wire, said convolutions being disposed on a base at any desired angle to the axis of the coil, which consists in placing the axis of a form carrying the base at the desired angle with respect to a sewing surface, sewing one turn to the base and sewing each successive turn to the turns preceding it and to the base by zigzag stitches 1 0. The method of forming a coil for elec tric al apparatus having the convolutions of said coil disposed at any desired angle to the axis oi the coil which consists in placing the axis of a form carrying a base for the coil the desired angleto a sewing surface, sewing one turn to the base, gradually rotating the base, stitching each succeeding turn or turns to the next preceding turn or turns and to the base and adjusting the stitching point to accommodate the increase in diameter of the coil.

11.. A. coil for electrical apparatus comprising aseries of alternate convolutions of wire prising a series of alternate convolutions of wire and insulating material forming a conical surface, the successive convolutions being sewed to each other and to a backing member of insulating material by zig-zag stitches and constituting a spiral.

13. A coil for electrical apparatus comprising a series of alternate convolutions of bare wire and insulating material forming a conical surface, the successive convolutions being sewed to each other and to a backing member of insulating material by zig-zag stitches and constituting a spiral.

14. The method of forming a coil for electrical apparatus having a plurality of alternate convolutions elf-conductor and insulating material, the said convolutions being disposed at any desired angle to the axis of the coil, which consists in placing the axis of a form carrying a base for the coil at any desired angle to a sewing surface, gradually rotating the form and stitching the alternate convolutions of conductor and insulating material to the base and to each other by zigzag stitches, and adjusting the stitching point to accommodate the increase in diameter or the coil.

In testimony whereof, I have hereunto subscribed my name this ?th day of August,

HABULD B. SMITH.

and insulating material disposed in a single Q plane, the successive convolutions being sewed to each other and to a background of insulating materialby zig-zag stitches constitutmg a spiral.

12. A. coil for electrical apparatus com-

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