US2388566A

US2388566A - Electric apparatus

Info

Publication number: US2388566A
Application number: US532126A
Authority: US
Inventors: Konstantin K Paluev
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1942-05-16
Filing date: 1944-04-21
Publication date: 1945-11-06
Anticipated expiration: 1962-11-06

Description

NOV 5, 1945- K. K. PALUEv ELECTRIC APPARATUS 5 Sheets-Sheet l Original Filed May 16 1942 e ,si

Inventor` Konstantin KPEULLQV,

`DISTANCE ALONG TRANSFORMER Hts Attorney.

NOV' 6, 1945- K. K. PALUEv ELECTRIC APPARATUS Original Filed May 16 1942 5 Sheets-Sheet 2 v, :a r rP o @Klim mm i? H fmm Y. mb K Nov. 6, 1945. K. K. PALUL-:v

ELECTRIC APPARATUS original Filed May 16, 1942 5 Sheets-Sheet 3 Inventor: Konstantin K. Paiuev,

His Attorney.

NOV 6, 1945 K. K. PALUEV ELECTRIC APPARATUS 5 Sheets-Sheet 4 original FiledMay 16, 1942 I [lll/lll Inventor: Konstantin Kpaluev,

His Attorney.

Nov. 6, 1945. vK. K. PALUl-:v

ELECTRC APPARATUS Original Filed May 16, 1942 5 Sheets-Sheet 5 V, e 1| Pa @P tK. nn Si v+m rma t Idir.

l l l Il @f7 by WW HIS Att orney.

Patented Nov. 6, 1945 ELECTRIC APPARATUS Konstantin K. Paluev, Pittseld, Mass., assigner to General Electric Company, a corporation of New York Original application May I6, i942, Serial No. 443,310. Divided and this application April 2li, 1944, Serial No. 532,126

(till. lfm-362D 5 fllaiins.

My invention relates to electric apparatus and to a structure for facilitating the cooling thereof, and although not limited thereto it has particular application to transformers.

This application is a division of my application S. N. 443,319, filed May i6, 1942.

It has been appreciated, in a general Way, that a thermal efliciency of electrical apparatus, such as transformers may be improved by forcing the circulation of an insulating or cooling fluid over the transformer structure in order to remove heat clue to the losses. However, it has been common practice to manufacture transformers with tanks having vertical cooling tubes connected to the top and bottom of the transformer casing, and to depend upon convection currents to circulate the uid over the transformer structure and through the cooling tubes to maintain the degree rise in temperature below an accepted maximum value, or to force the fluid through the conventional structure. Thus, when the advance in the electrical industry there is presented a problem of producing a practical, economical, and efficient structure which is not only designed for forced cooling, but which will have a high space factor and a resulting structure in which there is structural harmony with respect to electrical, mechanical, and thermal considerations.

It is therefore an object of my invention to provide an improved structure for an electrical apparatus for facilitating the circulation of an insulating iiuid through the apparatus.

Another object of my invention is to provide an electrical apparatus with an improved strucacterize my invention will be pointed out with particularity in the claims annexed to and forming a part oi this specication.

In the drawings, Fig. i is a perspective view, partially diagrammatic and in partial section, of a transformer and fluid system therefor, the

transformer structure being provided with an ture so as to improve the economy thereof and substantially decrease the size thereof over apparatus of previous constructions having the same capacity.

A further object of my invention is to provide the winding structure with an improved duct system which will allow a forced circulated fluid to remove the heat from the windings at a relatively rapid rate.

A still further object of my invention is to provide a transformer structure with an enclosing tank which will allow an insulating fluid to be continuously circulated from an intake port in the tank through the transformer structure into an exit opening in the tank structure in an improved manner.

Further objects and advantages of my invention will become apparent from the following description referring to the accompanying drawings, and the features of novelty which Acharembodiment of my invention; Fig. 2 illustrates curves which will be used in explaining thermal results of my invention; Fig. 3 is a side elevation in partial section of the transformer illustrated in Fig. l; Fig. Ll is a sectional side elevation of a portion of the transformer illustrated in Fig. 3, showing winding ducts, coil supporting, and fluid directing structure at one endy or the lower end; Fig. 5 is a perspective view in partial section of a portion of the structure illustrated in Fig. 3 showing the lower core clamp and coil supporting structure; Fig. 6 is an end View of the upper or second end of one of the core legs of the structure illustrated in Fig. 3, showing the coil supporting structure; Fig. l is a sectional side ele- Ivation taken along the lines 'l-l of Fig. 6; Fig. 8

is a Sectional side elevation of a portion of a transformer structure illustrating a modification of the fluid directing arrangement of Fig. 3; Figs. 9 and l0 illustrate modifications of the coil and duct system shown in Figs. 3, 4, and 5; Fig. ll is a perspective view in partial section of a transformer illustrating a modification of the fluid directing structure of Figs. 3 and 8; Fig. 12 is a side elevation in partial section and partially diagrammatic of the lower'- end of the transformer of Fig. 3, illustrating a modification of the fluid directing structure; Fig. 13 is a side elevation in partial section and partially diagrammatic of the transformer of Fig. 3, illustrating a further modification of the fluid directing system, and Fig. 14 is a sectional side elevation partially diagrammatic of the transformer of Fig. 3, illustrating the relationship between the windings, duct structure, and coil supporting arrangements. Y

In the arrangements illustrated in the drawings, I have provided an improved structure for directing the flow of an insulating or cooling fluid over a winding structure or over a portion of the surfaces of the winding to conduct heat theremay be employed with other types of structures, such as air-cooled transformers having an open casing.

Referring to Fig. l of the drawings, I have illustrated a transformer and iluid system therefor including a tank 2d having a core structure 2l with

Winding legs

22 and 23. Windings such as a low voltage Winding 21S and a high voltage Winding 25 surround both the winding legs and a suitable insulating fluid may be provided in the tank, such as mineral oil or a suitable chlorinated hydrocarbon such as for example, the liquid described in Claris Patent 1,931,373, issued October 17, 1933, and which is assigned to the same assignee as this present invention. In order to provide for forced circulation of the fluid through the transformer tank, there is provided a pump 2G of any suitable type, the intake side of which is connected to a port El in the transformer casing through a pipe 28. The pump 25 exhausts into a header 29 of a heat exchanger 39, the exhaust end of the heat exchanger being connected to a port 3i in the tank through a pipe 32. A conservator or expansion chamber 33 is provided which is iluidly connected to the top of the tank 29 through a pipe 3d. Such a transformer system with a substantially hermetically sealed fluid system and an improved arrangement for maintaining the degree of lpurity of the insulation and fluid dielectric and for maintaining the iluid pressure of the system within predetermined limits is described and claimed in my Patent 2,341,058, issued February 8, 1944 and which is assigned to the same assignee as the present invention.

As has already been stated, it has been generally appreciated that the thermal eciency of an electrical apparatus, such as a transformer may be improved by forcing a uid dielectric through the transformer structure in order to increase the rate of heat transfer from the transformer structure to the uid. I have found, however, that when a fluid is directed through a winding structure in a manner which will be described below, the ciciency of the resulting transformer structure is unexpectedly improved.

Referring to Fig. 2 of the drawings, I have illustratcd this unexpected improvement by showing the relative relationships between the temperatures of the various parts of the transformer system of my improved structure, as compared with that of previous constructions. Thus, the distance y sents the temperature of the duid in the casing surrounding the windings of the conventional structure, while curve Sii represents the temperature of the radiator. The relative temperatures. however, of a transformer of similar kva. capacity and manufactured according to my invention, are shown by the full line curves, and curve 39 represents the temperature of the copper, and curve d@ represents the temperature of the outside insulation. Curve 4i represents the temperature of the fluid dielectric in the heat exchanger when fluid that is forced through the transformer Casing 1S SED directed over the winding according to a feature of my invention.` It therefore, be seen that with a transformer manufactured according to my invention, not only is the average temperature of the various parts of the transformer structure and the winding hot spot lowered over that of prior constructions having equivalent kva. capacity, but the temperature changes from the bottom to the top of the transformer structure are considerably less with my improved structure than with prior constructions. It will also be noted that this is accomplished with similar average cooler temperatures.

The winding structure through which the fluid may be forced includes the lowvoltage winding 2C having concentric barrels or windings i3 and lili which surround the winding leg 22, as will be seen more particularly in Figs. 3 and 4. Each of the windings may have a plurality of axially disposed coils i5 each having any suitable construction, such as including a plurality of concentrically or radially disposed turns with insulation t5' between adjacent surfaces. The windings are spaced by suitable spacers to provide an axially extending duct d5, and in circulating a cooling uid through the duct it will ow over the outer axial surface of only the outer turn of each coil to vconduct heat therefrom. -The idea of disposing a duct between adjacent turns or parallel connected strands of adjacent coils of a winding with solid insulation closely adjacent or in intimate contact with the inside and outside surfaces of the winding is described and claimed in -my copending application Serial No. 443,309, illed concurrentlyy herewith, and which is assigned to the same assignee as this present invention. The windings may be wound around a suitable insulating cylinder which surrounds the winding leg 22. An insulating cylinder d8 surrounds the low d@ voltage winding and is spaced therefrom to provide a duct 9. Around the cylinder d8 may be placed the high voltage winding 25 having any suitable construction, and in the arrangement illustrated in the drawings I have illustrated two barrel windings Si! and 5i, the winding E0 being wound on the cylinder Q8 and the winding 5i being wound on a concentric cylinder 52.

In order to provide an axially extending duct through the high voltage windings, the winding 59 is suitably spaced from the cylinder 52 by suitable spacers so as to provide a. duct 53. The high voltage barrel windings EU and 5i may have any suitable construction and in the arrangement t illustrated in the drawings they include a plurality of axially disposed coils E6 and 55, the coils 55 being wound from the inside out in a U-shaped spacer and the adjacent coils 54 being wound from the inside out and then reshuled so that the turns progress inwardly from the outside in. This construction along with an improved spacer is de- .scribed and claimed in my copending application Serial No. 441,782, filed May 5, 1942, and which is assigned to the same assignee as my present invention. A suitable high voltage shield 56 is provided around the high voltage winding, the shield being supported by a cylinder 5l`which may be spaced from the outer high voltage winding so as to provide an additional axially extending duct 5B.

Around the winding leg 23, see Fig. 3, I also provide a low voltage winding including a pair oi' concentric barrels S9 and 6i and a high voltage winding including

barrel windings

32 and 93. These windings may also be provided with ducts similar to those described in relation to the windings surrounding the winding leg 22. The

connections between the various concentric high and low voltage-windings around each leg will be described below in relation to the description of Fig.14.

In order to direct the insulating fluid which enters the transformer casing through the intake port 3l into the ducts between the windings which surround the winding leg 22, I provide a suitable barrier arrangement 65 which prevents fluid from passing up through the space between the shield and casing. The barrier 65 may include any suitable construction and in the arrangement illustrated in the drawings it is provided by a portion of a diaphragm which extends from or forms a portion of a core clamping structure 66. As will be seen more clearly in Fig. 5, the clamping structure 66 includes a pair of spaced angle bars 61 and B8 between which the lower ends of the laminations which make up the winding

legs

22 and 23 are supported. Since the transformer structure illustrated in the drawings includes two winding legs, the clamping structure is provided to accommodate the ends of the laminations of two winding legs. However, it is to be understood that my invention may be employed with a transformer having any suitable number of winding legs. Laminations forming -yoke portions are also supportedbetween the angle bars 61 and 68. Partitions 69 extend from the central portion of the angle bars 61 and 68 so that the radial extending diaphragm 65 with the axial extending partition 69 forms with the cooperating surfaces of the tank structure a plurality of chambers 10 and 1l. A partition similar to that shown in Fig. 5 is provided on the opposite side. These chambers and 1| in turn lead to the ducts surrounding the winding

legs

22 and 23 respectively and their purpose will be described below.

As will be seen in Fig. 5, in order to support the windings, the diaphragm 65 is provided with portions below the winding

legs

22 and 23 including a plurality of ring portions 12 between which are provided openings which communicate with the various ducts between the windings. All the ducts which

surround winding legs

22 and 23 communicate with a passage or compartment- 13 which is above the barrier 65, see Fig. 3, through radially extending ducts 14 provided in Upon operation of the pump 26, the circulation of fiuid, as shown by the arrows in Fig. 3, may be traced as follows: The fluid will be circulated through the intake port 3| and due to the barrier 65 and the compartment partitions 69, the fluid will be directed up through the various ducts which are in the high and low voltage windings which surround the winding leg 22. The fluid will then pass out through the ducts 1li of the winding leg 22 into the compartment 13, and into the ducts 14 of the winding leg 23 and through the ducts which are within 4the windings which surround the winding leg 23. The fluid will then pass into the chamber 1i and out through 4the exhaust opening 21 and through the pump and cooler 30. With such a construction all the fluid is directed through the group of ducts which surround the .winding

legs

22 and 23 in series. In thisI manner the forced fluid is passed through the ducts at a much faster rate than it would be if the same amount of fluid were circulated through the groups of ducts surrounding the winding legs in parallel. With such a construction the fluid passes through the ducts at a maximum rate for a given total quantity of fluid so that the temperature rise in the windings is maintained at a minimum value, since the'rate of transfer of heat from a heated surface to a flowing fluid isy increased with an increased rate of velocity of lfluid flow.

In order to provide an arrangement for obtaining relatively tight seals between the cooperating surfaces of the diaphragm and the partition 69 and the tank, I provide suitable gaskets which will be effective merely upon the lowering of the core and coil structure with the brackets E1 and 68 in place in the transformer casing 20. As will be seen in Fig. 4, a gasket for providing a relatively tight seal between the periphery of the diaphragm 55 and the adjacent surface of the tank 2U includes an inwardly extending shoulder portion 15 and a right angularly extending portion 16. Within this portion I have provided a channel member 11 made of any suitable insulating material, and a coil spring 1B which has a helical cross section and is circular so as to surround the entire periphery of the channel member 11. Thus, when the core and coil structure is lowered intothe transformer casing 20, the channel member is so positioned with respect to the bottom 19 of the tank structure that as the core and coil structure is firmly supported on the bottom of the clamp structure B1 and 68, the insulating material 11 will be forced a. small amount toward the collar portion 'l5 thereby compressing the spring 18 to provide a relatively tight joint between the channel portion and the cooperating surfaces of the shoulder 15 and the diaphragm 65.

A relatively tight joint may be provided between the partition 69 and a cooperating portion which extends inwardly from the tank wall toward the partition 69, by a seal which includes a channel member 8l which is integral with the partition portion 80 of the side wall. A gasket 82 is supported in the U-shaped channel 8| and a plate 83 is Isupported by the U-shaped channel 8| against the gasket 82. The plate 83 is designed for a limited movement toward and away from the channel member 8l so that when a cooperating plate 84 which is integral with the partition 69 pushes against the plate 83 a relatively tight joint will be formed between the

plates

83 and 84 due to the resiliency of the 'gasket material 82.

In order to clamp the core structure and support the windings at the upper or second end of the apparatus structure, I provide a pair of clamp members and 9|, see Fig. 6, which are placed on either side of the laminations forming the yoke portions 92 over the winding leg 22. The laminations 92 are rigidly atached together by a pair of bolt members 93, see Fig. 7, which extend through' aligned openings in the lamlnations 82 and have nuts Qt at either end for tightly clamping the laminations. The clamp or plate members 90 and 9i may then be forced downwardly against the upper ends of the windings so as to rigidly clamp or support the windings between the ring members 12 of the lower coil structure and ring members which' are rigidly attached t0 the plate members 90 and 9| through webs 96. The plate members 90 and 9| have elongated slots 91, see Figs. 3 and 7, for accommodating the nuts 94 and so as tov allow limited movement of the plates 9U and 9i after the bolts and nuts are made tight. The plate members 90 and 9| may be held in this position by inserting plugs 94' between th'e nuts 94 and the top and bottom suriaces of the slots di. Plates 9@ are then placed over the slots el, the plates having openings for accommodating ends of the bolts @3, ln order to hold the plugs QG' in place and hold the plate members e@ and'til rigidly against the upper ends of the windings, nuts t@ may be tightly screwed- 8G@ has a tongue portion Urli which extends upA through a slot lil, see Fig. 6, in th'e yoke lamination structure Q2. A transversely extending bar atouts against the upper surface oi the .tongue portion lill. In order to pull the bar ilil toward the windings and thereby force the tongue lill with its root member ill@ against the windingsl I provide block members Hilti which are' rigidly attached to the plates and el. The block niembers leb and the bar member dell have aligned openings for the reception oi bolts Miti. Nuts lill are then screwed on the ends oi the bolts lub, and it will be seen that both ends of the bar member ldd are forced downwardly towards the ends or the winding structure, thus forcing the ioot member ill@ against the windings. A core and coil yclamping and supporting structure is also placed above the winding leg 23 which is similar to that described above.- In Fie. 8 l have illustrated a modiilcation o th arrangement described above for directing the ilow of an insulating or cooling fluid into the several ducts between the windings. VA plurality of concentric windings l lll are spaced by spacers i l i providing axially extending ducts i i2. At the ends or the windings there are provide lll escasos which entend inwardly from a cylinder il between coils 23, and collars itt which' extend outwardly from a cylinder it@ on the opposite sides of the coils from the collars tile.

In liig. ll I have illustrated an arrangement for selectively controlling the rate oi flow oi an insulating duid between parallel ducts. The structure includes ducts lSl around one winding, such as a low voltage winding iii@ and ducts i8@ around another winding, such as s, high voltage winding lll. in insulating :fluid may then be circulated through the separate duct systems from a common source through a pipe i3d.' One branch pipe i3d then communicates to the lower end of the ducts |33 while a 'pipe i3? communicates to the lower end of the ducts ibi around th'e low voltage winding. Valves |133 and @3Q are placed in the pipes i3d and i3? respectively and by varying the setting oi the valves, the amount ci iluid which flows through the parallel duct system may be selectively controlled.

In the structures which have been described v. above barirers have been placed between the lower radially extending ducts which communicate withA the axial extending ducts. These radial extend such as by splitting the ends il@ ol the spacers iiiwhich form the axial ducts as is shown at H2. Upon splitting th'e ends H3 they may be bent over so as to form ducts between suitable insulating members llfl which may be the flanged ends of cylinders upon which the windings are wound. The dielectric fluid may then be forced into the casing l l5 through an opening ld, and in order to direct the fluid into the axially extending ducts I provide a barrier lil which cooperates with an insulating cylinder ||B for preventing the iiow of the dielectric fluid up through th'e space between the electrostatic shield H9 and the casing. The cylinder il 8 may therefore be a part of the insulating structure of the shield lle. Another cylinder |2u may be provided inside th'e shield H9, the cylinder being spaced from the outer winding layer l lll so as to provide a duct between the outer winding layer and the electrostatic shield l IS.

In Fig. 9 I have illustrated a disk coil winding having a plurality of axially spaced turns |2| between concentric cylinders |22 and |23. In order that the uid which' iiows through the space between the winding space may wash a major portion of the winding surface, I provide a zig-zag path which is obtained by providing spacers |26 between every other winding |2| and the cylinder 623. Spacers |25 are also placed between the cylinder |22 and the windings adjacent th'ose which are spaced by the spacers We. Thus a zig-zag path is provided. Another arrangement for providing a zig-zag path, as illustrated in Fig. 10, includes insulating collars or washers |26 ing ducts may be formed in any suitable manner ends of the windings and the casing or shield for directing the flow of the insulating ud through the ducts and preventing the :duid from passing through the space between the outside of the winding or electrostatic shield and the inside of the casing. By such a construction a maximum amount of heat may be carried away from the winding conductors while the fluid is being iorced .through the ducts.

loads or when the pressure which forces the dielectric fluid through the transformer construction fails, I provide an openable port i6@ in a barrier itil, as may be seen in Eg. 12, which illustrates somewhat diagrammatically a construction similar to that oi Figs. 3, 4, and 5, the barrier lill accomplishing the same function as the diaphragm S5. Since the barrier Se divides the lower end-of the casing into chambers l@ and ll, the diaphragm lill is provided with a similar closable opening i432 communicating with the chamber ll. The opening lil@ may be held in any suitable condition, such as normally closed by a valve M3, the operation of which may be controlled in any suitable manner, such as being held against the lower surface of the opening Mu by the force of the incoming iiuid against a pilot vane Ulti. The valve |23 and vane |64 are rotatably mounted on a shaft |65 and when the force of the incoming fluid through the pipe 3| stops, the valve and vane assembly will drop to the dotted line position due to the force of gravity and thus open the port Illu. The iluid in the tank may then circulate, as shown by the dotted arrows, up through the ducts and down through the space between the windings and the casing, the full line arrows indicating the ow when the pump is ln operation. Since the iiuid circulates out through a pipe 21, a similar valve and vane arrangement including a valve |6 is provided which cooperates with the upper portion of the opening |62, the operation of which may be controlled in any suitable manner such as by a. pilot vane Vllil which is held in the solid line position shown in Fig. 12 by the force of the outgoing'uid. Howeveigupon cessation of the movement of the insulating iiuid the vane |46, due to any suitable biasing force, such as that of a. counterweight Ml', will move around a pivot point |48 and thus raise the valve |66 and open the opening |42.

'Thus the insulating uid may circulate as shown by the dotted arrows up through the ducts and down through the space between the winding legs and the casing, the full line arrows showing the direction of forced fluid iiow.

In Fig. 13 I have illustrated another arrangement for opening ports |49 and |50 in a diaphragm the ports being on both sides of the partition 69. Upon cessation of the flow of the insulating uid continued operation of the transformer will cause the temperature to rise particularly in the upper portion of the casing.' I have therefore provided a bimetallic element |52 which is attached to a rod S53. The rod is in turn attached to valve members |54 and |55 through a suitable linkage mechanism |56. The 'bimetallic element is so attached to the rod |53 that upon heating it will move and operate the linkage mechanism to the dotted line position as Aillustrated in Fig. 13 and, therefore open the ports. The uid may then circulate as shown by the dotted line arrows due to natural convection currents.

In the apparatus described above it is so designed as to bring about structural harmony between the various parts. By this is meant an improvement in the structure from a mechanical point of view also contributes to the thermal and electrical efficiencies of the resulting structure, etc. This is brought out in Fig. 14 which somewhat diagrammatically illustrates the insulated windings of the structure of Figs. 3 to 7. The low voltage winding 60 is provided with insulation |60 at either end of the winding which insulations have similar thicknesses, as is indicated yby the letter a. The lower end of the winding 6| also has insulation |60, and the upper end of the low voltage winding 6| has insulation in the form of a collar |6| and spacers |62 providing the radially extending ducts 14 which communicate with the axially extending ducts between the windings 60 and 6|. The total thickness of the collar |6| and spacers |62 is also equal to a. Since the top and bottom coilsof the low voltage windings 60 and 6| are connected together by cross-overs |63 and |63 respectively, the insulation at the top and bottom of the two windings may 'be of the same thickness, a. In this manner an insulation distance at the top end of the winding 6| is provided which is similar to the distance a, but the insulation thickness includes solid insulation |62 and insulation in the form of ducts having a fluid dielectric and spacers. Thus for magnetic symmetry the upper and lower ends of both low voltage windings have the same thickness of insulation and the upper end of the 4outer winding 6| has an insulation with suitable y ducts as part of the insulation The inner high voltage winding 62 also has inl sulation in the form of a collar between the lower end and the lower core clamp The upper end insulation includes the spacers |62, a flanged end [64 of the cylinder upon which the winding 62 is wound and insulation |65. The sum of the thicknesses of the various insulation at the upper end of the winding 62 is also equal to a, The outer high voltage winding 63 has insulation |66 at its lower end equal to a distance b. In determining the required thickness of the insulation at the top and bottom of any winding for any given voltages at the top and bottom, the amount of insulation necessary may be computed, given the dielectric strength per unit of axial length for the insulation to be used at each end. The end requiring the greater thickness may then be used as a measure of the thickness for the other end. The upper end of the winding 63 is insulated from the upper core clamp by insulation which includes a collar |61, spacers |68 forming a radially extending duct which leads to the axial ducts and flanged collars |64 and |69 of the winding cylinders. The sum of these thicknesses is also equal to the distance b so as to contribute to the magnetic symmetry of the construction. The thickness of the insulation at the ends of the winding 63 is however thicker than the distance a since the upper coil 0f the winding 62 is connected to the lower end of the winding 63 so that the upper end of the Winding 63 will be at a higher potential than the upper end of the winding 62. may be made through a crossover l'lll- The lower end of the winding 62 may be connected to ground through a lead It Will be seen that for both the

windings

62 and 63 the upper ends of the windings are respectively at a higher voltage than the lower ends of the windings. The upper composite insulation however has a higher dielectric strength per unit of axial length than the lower due to the greater creepage length and the fact that part of this length is over edges of insulating flanges. In the construction illustrated in Fig. 14 the upper end of the winding 63 is connected to the lower end of the inner high voltage winding 50 around the leg 22 through a crossover |12. The upper end of the winding 50 is connected to the lower end of the winding 5| through a crossover |13, and the upper end of the Winding 5| may be connected to a suitable high voltage line. Insulation at the lowerend of the winding 50 is provided by an insulating collar |14, and the insulation at the upper end of the winding 50 is provided by an insulating collar |15 and by a ange |16 which is integral with the cylinder 48 upon which the winding -50 is wound. Spacers |11 are provided for providing the ducts 14 which communicate with the ducts which surround the

low voltage windings

43 and 44. Since the upper end of the winding 50 willbe relatively -at a higher potential than the lower end of the winding 50 and the upper end of the winding 63, the thickness of the insulation indicated by the letter c will be greater than b. For magnetic symmetry, however, the thickness of the insulation |74 is also equal to c. The lower end of the winding 5| will have suitable insulation |18 and the upper end will have insulation including a collar |19, integral iianges |16 and |8| of the cylinders upon which the

windings

50 and 5| are wound and spacers |11 between the anges which provide the ducts 14. Since the upper end of the winding 5| is at a higher potential than the upper end of the winding 50, the thickness of insulation d will .be a greater thickness than that indicated by the letter c. For magnetic symmetry, however, the thickness of the'insulation |18 will also -be equal to d, The insulation around the

low voltage windings

43 and 44 is also equal to c which is the thickness of the insulation of the adjacent high voltage winding, in order to carry out the magnetic symmetry so as to take care of short circuit forces. The upper and lower ends of the

low voltage windings

pairs

43, 44, and 60, 6| may be connected to any This connection suitable external lines through conductors i555 and ist respectively.

Although I have shown and described, particular embodiments of my invention, i do not desire to be limited to the particular embodiments described, and intend in the appended claims to cover all morlications which come within the spirit and. scope of my invention,

What claim as new and desire to secure lov Letters Patent of the United States, is:

i. In an electric induction apparat a core having a pair oi Winding legs, a plurality of concentric barrel windings surrounding said Winding legs, spacer means between said concentric harrel windings providing a plurality of concentric ducts between adjacent barrel windings, a substantially enclosing casing, a iiuici @electric within said. casing, a plurality o intake ports leading to one end of said ducts, ultl passage means connecting from the exhaust end ci said ducts to said intake ports providing a closed fluid system, pump means for circulating said huid from said intake ports through said ducts and through said passage means baci: to saici intake ports, and valve means in said intake ports ier selectively controlling the rate at which the circulating fluid may circulate through said. ducts.

2. In an electric induction apparatus, a core having a winding leg, a low voltage winding and a concentric high voltage winding surrounding said leg, means forming fluid passages in heat conductive relationship with said high voltage and low voltage windings, a casing surrounding said core leg and winding, a ucl dielectric in said casing, ports connecting to the intake ends of said low voltage ducts and salcl high voltage assenso ducts, a fluid dielectric within esiti casing, nula passage means connecting from the exhaust end of said ducts to said intake ports forming a closed uid system, and, valve means in said low voltage ports and said high voltage parte for selectively controlling the rate at which the cir culating huid may circulate through said low voltage and high voltage ducts,

3. A transformer having relatively' high and low voltage windings, a senarate cooling duct associated with each Winding, means for orcing lpump for forcing cooling finis saisi ducts in parallel, and means for selectively adjusting the relative new oi cuoli g fluid 'through saisi ducts.

5. A transformer comprising, a core having a plurality o winding legs, senara high and low voltage windings on each leg, separate cooling ducts in heat exchanging relation with the outer surface of each winding on each leg, means for directing a flow of cooling huid through the ducts for corresponding windings in series and through the ducts for diierent windings in narallel, and means for seiectveigr varying the rela tive now through said ducts for diiierent vrincl.-z

ings.

'KONSTAN'M l. PALUEV.