US1421899A - Transformer - Google Patents

Description

I R. V. BINGAY.

TRANSFORMER.

APPLICATION man OCT 11. new.

1,421,899, Patented July 4, 1922- SHEET I.

4 SHEETS- R. V. BINGAY.

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APPLICATION FILED OCT IT. I919. 1,421,899, Patented July 4, 1922.

4 SHEETS-SHEET 2.

lut W 351 alien war R. V. BINGAY.

TRANSFORMER.

APPLICATION FILED OCT 17,1919. 1,421, 99, Patented July 4, 1922.

4 SHEETSSHEET 3,

$1 wow/tar UN'iTED STATES ROBERT V. BINGAY. OF PITTSBURGH. TRANSFORMER COMPANY, A

PATENT OFFICE.

TRANSFORMER.

Specification of Letters Patent.

Patented July 4, 1922.

Application filed October 17, 1919. Serial No. 831,325.

To all whom. it may COIIUPIH.

Be it known that I. Ronnn'r. V. BINGAY, a citizen of the United States. residing at Pittsburgh in the county of Allegheny and State of Pennsylvania, have invented certain new and useful lnnn'ovements in Transformers, of which the following is a specitication.

This invention relates to transformers, and the chief object of the invention is to form the transformer coils in such manner that they will be rigid and securely protected against relative shitting and short circuiting in use and at the same time permit the core and coil parts to be arranged. shaped and proportioned for most eilicicnt distrihution ot' the current and magnetic lli'ix and therehy secure improved operating charactcristics.

()thcr objects and advantages of the invention particularly in connection with oil cooled transformers having a double magnetic circuit will appear from the following description.

In the accompanying drawings the invention is shown as applied to a double magnetic circuit type of transformer which includes the so called shell-type" transformer, but it will he understood that it may be applied to any type.

Fig. l is a diagrammatic illustration 0! the method of building up the coils:

Fig. 2 is a horizontal sectional view of a transformer illustrating one embodiment of the invention:

Fig. 3 is a plan view of the coil shown in Fig. 2. and

F1gs. 4 and 5 are respectively v rtical i'ront and side views oi the same with the tank sides and upper portions omitted.

in prior transformers dillicfllty has been experienced in making them st'il'liciently thick mm front to hack for maximum elliciency of the material employed and at the same time providing coils of desired strength to resist relative shifting and the wearing down and hrcalulowu oi' the insulation. Each change in a transl'oruu'r current brings a change in the magnetism, and resultant stresses between turns of the primary and secondary coils and there are also stresses between primary and secondary coils ot'ten tending to violently drive them apart. 'lhesc stresses are applied to every part of the coiled wire so that any lengths of Wire that are not securely held shift relativeiy to the others and the loosening once started increases with every subsequent shock until finally the insulation breaks down and a short circuit occurs. Where the coil section is not of continuous curvature as in oblong coils with bends at the ends, the straight side strands cannot be laid and held snugly against adjaceiit inner coils because the winding tension on these straight strands is parallel to them and cannot press them together and when the bend at the next succeeding end is made the bending of the wire there tends to raise and loosen the straight side strand just previously laid. These ob- ]o'ng coils. therefore. are necessarily weak in their straight strands and the longer the oblong the greater will be the tendency of the side strands to loosen, so that the practicable length of transformer coils and the corresponding thickness of the core have hitherto been severely limited.

(dnditions of efficiency and economy, on the other hand. require a narrow thick core construction with a correspoi'idingly narrow and long coil. Economy of copper demands a small coil and in turn a small cross section of core through the .coil with great density of magnetic liux there and correspondin ly greater magnetic resistance at this portion of the core, and in order to compensate for this a lowered resistance and enlarged cross sectionare necessary for the remainder of the core. I? the core is of generally square section as with a circular form of coil desirable for strength these enlarged portions of the core outside of the coil assume great widths extending far from the coil so that the tendency of the magnetic circuits to expand centrifugally is given full play and the inner portions of the surrounding part of the core carry little flux and the outer portions are dense with it. This uneven distrihutiou oi flux in turn prevents the desired decrease in magnetic resistance and a large portion of the core is practically wasted while the core itself and the supporting parts are. extremely bulky. It is therefore highly dcsi able to redui'e this excessive width of core, minimize the over-all dimensions and material required. prevent the spreading of the magnetic tlux and produce a more even and eflicient magnetic liux distribution; and the only way this can he done is to increase the core depth so as to give a construction dcep from front to hack and oblong in section. Thus, while considerations of mechanical coil strength and durability favor a round coil and a core square in section, considerations of efiiciency favor a core having one dimension greater than the other in section; and comnicrical practice has not heretofore attained the best efficiency and the desired strength and durability.

The coil and core provided by the present invention avoids the disadvantages of the prior constructions in that it permits a thick and narrow section of core to be used and at the same time the coil is itself rigid, strong and self supporting in all its parts. \Vith it the core may be made of any de sired sectional construction for best economy of material and efficiency in performance and the construction will also be strong and with all parts permanently secured against loosening or distortion.

In the drawings, Fig. l. the coil 5 is shown in process of formation the wound portion 6 being fast on rotatable mandrel 7 while the winding length 8 is gripped by tension device 9. The shape of the coil and mandrel is elliptical or oval in section so that the windin of each layer takes place on a surface ot continuous though variable curvature and having comparatively large radii of curvature throughout. Hence though the coil is lon and narrow in section it is wound easily and tightly and under continuous and uniform tension, like a circular coil, from end to end of the wire. Each increment of the wire is flexed and pressed tightly against the next adjacent inner portion of the coil and the whole of the wire remains shaped and tensioned into a coil every portion of which is arched and securely self supporting with no weak parts to become loosened in service. Thus the successive layers of the coil in the same or adjacent planes tend to support each other. and the successive lonitudinal layers of the coil build up what is in effect an elliptical sleeve surrounding the core leg and providing vertical channels for ventilation or oil cooling.

As illustrated in the drawing the coil structure of this invention even for ver large transformers may safely be made umtary without the assembly of separately wound and separately reinforced sections. The mutual supporting action of all the parts throughout the entire unitary coil structure of this invention makes sectional reinforcement unnecessary and avoids loosening at any-point. In the transformer con struction shown there is an innermost barrier 10 coextensive with middle leg 21 in the core, around this is wound one coil 11 of the of successive low tension winding made u vertical layers to form anelliptical sleeve, then a barrier 12 of insulatin material then a high tension coil 13, anot er barrier 14 as and the other coil 15 of the low tension windonly reduce the len ing, coils 13 and 15 being made up of sucessive vertical layers as in the case of coil 11. Additional barriers of insulation 16 fill the spaces between the coils and the core. In order to ventilate or cool the coils adjacent windings are separated by vertical strips 17 of insulating material sons to provide vertical ducts 18 between one or more of the coil layers lying in the same plane for the cooling fluid which gains access to these ducts at the bottom and also throu h the intermediate open spaces 18' provided in winding the coils; the ducts also insulate the layers of the coils in the same plane from each other resulting in economy of material and greater efficiency, as the ducts serve two purposes. Thus with the unitary coil construetion of this invention vertical ducts continuous from bottom to top of the coils are provided for the cooling fluid, saving in the amount of metal and avoiding weakening and breakdown of the insulation. The core 19 is also provided with cooling ducts as 19' if desired. In some cases the ducts may be eliminated altogether due to the greatly increased radiatin surface.

The oval or el iptical contour of the outer periphery of the coil also permits outside legs such as 22 and 23 to be closely positioned cutting down the over all width of the transformer, because the tapering corner spaces 24 provided between the coil and these core legs give extended access of the cooling fluid to the surfaces of the parts while at the center the core and the coil insulator may be in contact.

As shown in Figs. 2 to 4 the core 19 is preferably of the double magnetic circuit type, that is, one having an interior-core surrounded by the coil and at least two outer legs connected with the interior core and in which the interior core may form a common path for the flux or may provide independent. aths therefor. In such a core the center eg 21 within the coil is only about one 1 sixth of the flux path in length, the remaining five sixths formed by the yokes and legs 22, 23 being free to have the most ellicient Size (ii cross section to com )ensate for the crowded flux in the center leg and permit this leg 21 and the coil 5 to be made smaller with resultant saving in copper. i

The deep or thick andnarrow core attained by my invention also has the advantage that by reason of its depth or thickness, 12;; the portions of the core outside the coil may be made narrow and yet afford low reluctance, and the narrow outside portions not th of magnetic path, but confine the magnetic flux to a narrow path of comparatively great depth or thickness. This insures quite a uniform distribution of the flux throughout the cross section of these narrow core portions and not only reduces the losses occasioned by irregular and 1111- 1.30

even distribution of the flux and the long flux paths of former constructions. but. also aids greatly in reducing the instantaneous charging current.

The transformer core I!) is mounted in a supporting frame 25 having verti :al corner angle irons 26 fastened together by tie bolts 27 and connected by cross bars 28 and supported on cross beams 29. supported by the base. Due to the relative narrownes of the core sections and the elongation of the elliptical coil the over all dimensions of the transformer are sufficiently nearly equal in thickness and width so as to fit most advantageously in round tank 35. such a round tank being relatively strong and inexpensive in comparison with the oblong tanks hitherto usual.

The coil structure of this invention is easily wound and permanently arched and self supporting throughout. giving the great mechanical strength required and permitting a unitary formation of the windings in compact and economical manner and at the same time providing a large number of continuous ventilating ducts carrying the cooling fluids to all portions of the coils evenly cooling il parts of the transformer coils and avoiding local highly heated portions with rapid temperature gradients which would cause a relative stressing and wearing between the parts heated to ditl'crent degrees. When assembled in the transformer it allows the core to be most eliicicntly designed and saves greatly in the amount of material used and in the over all size of the transformer. Vertical ducts at the ends of the coil are exposed to unobstructed direct flow of the cooling oil and the coil wires passing in continuous evolutions around through these end portions conduct then-to any heat tending to accumulate in the less accessible portions of the coil.

Aside from the advantages of my invontion as regards strength of construction. durability. economy in cost of manufm-turc. and the like, my invention greatly increases the efiiciency of the transformer. This is due to the shape of the parts and their interrelation.

The shape of the coil is such that it gives a very uniform distribntion'of the magnetic llnx created tiwreby. because there are no abrupt bends or sharp turns in the coil. This avoids any tendency to overcrowd the magnetic flux at certain points. it conscqucntly tends to create an evenly distributed flux of which all parts may he el'lectively and efficiently utilized.

Also the core is so shaped and related to the above form of coil that it receives and carries the magnetic llux created by the coil in a most effective and efiicient manner. The contour of the core within the coil substantially conforms to and is in close proximity to the inner surfac of the coil and there are no wasted air spaces of any appreciable amount. The interior core by thus conforming to the contour of the interior of the coil preserves the uniform flux distribution as set up by the coil and utilizes the space within the coil to a maximum dcgrec. By reason of attaining a uniform distribution of flux in the interior core. the electromotive force induced in the secondary coils is likewisc most eiiiciently set up because all parts of the secondary coils are quite uniformly acted upon by thc flux of the core. 'lhere isthus quitc a uniformly d stributed and harmonious action between the coils and core and vice versa in all parts giving ctiicient and effe tive use thereof. lrrcgular and uneven interactions which tend to reduce ciliciency are avoided.

still further advantage of my invention is that thc instantaneousexciting current is very low. thus tending to prcvcut creation of surges in the transformer and also to pro tect the transformer rom injury from surges on the line.

Also by inv improvement. the coils have all parts quite fully surroundial by iron. within and without. which grcatly aids in ctlicicncy not only by the uniform relationship between coils and corc. but also by the low reluctance of the core as a whole and by the cmnparatively short length of paths it the magnetic circuit.

\Vhile in the particularembodiment shown the coil is illustrated in connection with the unitary windings for a transformer having a double magnetic circuit. it is applicable to other forms and in particular the elliptical coil structure is equally adapted to sectional coils. 'lhe principle of the invention is not contincd to the specific structure described but is intended to cover such mmlifications thercof as fall within the scope of the up pcnded claims.

I claim:

1. in a transformer. the combination of a laminated core having a core leg comprisin;: parallel laminar the cross section of said parallel lamina having the dimension perpendicnlar to the planes of said parallel laminae greater than the width of the lamina of said core leg. and a coil around said leg similarly having one dimension greater than the. other and its greater dimension extending in the direction perpendicular to the planes of said laminae. the convolntions of said coil having continuous arch shaped curvature. throughout.

2. in a transformer. the combination of a laminated core having a core leg comprising parallel laminae. the cross section of said parallel lamina ha ing the dimension perpendicular to the p ancs of said parallel laminae greater than the width oftl e lamina of said core leggand a coil around saiddeg of section of the para general elliptical-form and having its major axis perpendicular to the planes of said laminae, the convolutions of said coil having continuous arch shaped curvature throughout.

- 3. In a transformer, the combination of a laminated core having a core legcomprising parallel laminae, the cross section of said parallel lamina: having the dimension perpendicular to the planes of said parallel aminse greater than the width of the laminae of said core leg,and a coil around said leg 'of general elliptical form and having its major axis perpendicular to the planes of said laminae, the convolntions of said coil having continuous arch shaped curvature through,-

out, said coil comprising primary and sec ondary windings located one within the other.

4. In a transformer of the double magnetic circuit type, the, combination of a core leg having its cross section of general ellipticul form. and a surrounding coil having convolutions conforming generally to the shape of said core.

5. In a transformer, the combination of a laminated core having a. double magnetic circuit and'having the laminae of its core located in parallel planes, the central leg of the core having its cross section of general elliptical form, and a coil around said leg having convolutions conforming generally to the form of said core leg and, of arch shaped curvature throughout, the formation of said core leg being such as to provide an ular ventilating spaces between the in si e of the ends of said coil and adjacent parts of said core leg.

6. In a transformer. the combination of a laminated core having a core leg comprisin.g vertica-l parallel laminae, the crow section of said parallel laminae having the dimension"prpendicular to the planes of said parallel laminw greater than the width of the laminae of said core leg, a transformer coil of general elliptical form of continuous curvature throughout around said leg and having its major axis pe ndicular to the planes of said laminae and aving success ve windings one within the other. and a series of vertical ventilating strips spaced apart from each other and separating successive windings at all points and providing vertical ducts between said s ced windings.

7. In a transformer, t e combination of a laminated core having a double magnetic circuit and having'the laminae of its core located in vertical rallel planes. the cross ll laminw of the central leg of the core having the dimension perpendicular to the planes of said laminar greater than the width of the laminae of said leg, a coil around said leg and similarly having one dimensio'n greater than the other and its greater dimension extending in the central core leg, and a coil of direction perpendicular to the planes of said laminae, said coil comprising successive windings one within the other and each winding having contimt us arch shaped curvature throughout, an a series of vertical ventilatin strips s liced apart from each other and separating said successive windings at all points to form vertical ventilating ducts.

8. In a transformer, the; combination of a laminated core having a double magnetic circuit and havin the laminae ofits core located in paralle planesra cross section of the parallel laminae of the. central leg of said core having the dimension perpendicular to" the planes of said parallel laminae greater than the width of the laminae of said general ellipticalform around said leg and having its major axis perpendicular to the planes of said laminae. the convolutions of said coil having continuous arch shaped curvature throughout. and the width of the. connecting parts of said core outside said] coil bein such that the magnetic flux carried by said connecting parts 1s distributed substantially uniformly therein. k

9. In a transformer, the coniliination of a laminated core having a doublemagnetic circuit and having the laminae of its core located in parallel planes, the centr nl leg of the core having a cross section of said parallel laminae with the dimension perpendicw lar to the planes of said parallellaminae greater than the width of the laminae of said core leg, and a coil around said core'leg having gradually and continuousl curved interior end portions, and the sai central core leg conforming in general outline to and being in close proximity throughoubto the inner surface of said coll.

10. In a transformer, the combination of a laminated core having a double magnetic circuit and having the laminae of its core located in parallel planes, the central leg of the colehaving a cross section of said parallel laminae with the dimension perpendicular to the planes of said parallel hhninae greater than the width of the laminae of said core leg, and a coil around said core leg having gradually and continuously curved interior end portions. and the said central core leg conforming in general outline to and being in close proximity throughout to the inner surface of said coil, and tlie connecting portions of said core outside said central core leg also having a cross section with the dimension perpendicular to the planes of its parallel laminae greater than the width of its laminae and having such width that the magnetic flux is distributed substantially uniformly through the cross section of said connecting outside portions of the core.

11. In a transformer. the combination of a laminated core having a core leg comprising parallel lamina, the cross section of said parallel laminae having the dimension perpendicular to the planes of said parallel laminae greater than the width of the laminae of said core leg, and a coil around said leg similarly having one dimension greater than the other and its greater dimension extending in the direction perpendicular to the planes of said laminae, the ronvolutions of 10 and being in close proxlmit y throughout to 15 the inner surface of said coll.

ROBERT V. BINGAY.

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