US2912658A

US2912658A - Turburlence promoters for fluid cooled electrical apparatus

Info

Publication number: US2912658A
Application number: US328113A
Authority: US
Inventors: Konstantin K Paluev
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1952-12-26
Filing date: 1952-12-26
Publication date: 1959-11-10
Anticipated expiration: 1976-11-10

Description

Nov. 10, 1959 K. K. PALUEV 2,912,658

TURBULENCE PROMOTERS FOR FLUID COOLED ELECTRICAL APPARATUS Filed Dec. 26, 1952 2 Sheets-Sheet 1 Fig.1.

Inventor:

Konstantin K. Paluev, by @MPW Hi5 Atbonneg.

Nov. 10, 1959 K. K. PALUEV 2,912,658

TURBULENCE PROMOTERS FOR FLUID COOLED ELECTRICAL APPARATUS Filed Dec. 26, 1952 2 Sheets-Sheet 2 Inventor: Konstantin K. Paluev,

His Attorneg.

1 2,912,658 TURBULENCE PROMOTERS FOR FLUID COOLED ELECTRICAL APPARATUS Konstantin K. Paluev, Pittsfield, Mass, assignor to General Electric Company, a corporation of New York Application December 26, 1952, Serial No. 328,113

3 Claims. (Cl. 336-58) This invention relates to stationary electrical induction apparatus having a magnetic core and electrical windings and, more particularly, to an improved cooling arrangement for such apparatus.

When stationary electrical induction apparatus is operating heat is produced. The heat produced must be removed if the apparatus is to be kept within. safe temperature limits. For instance, if the heat produced is not removed, the electrical windings may become heated to such a high temperature as to destroy the insulation on the electrical windings.

Some installations of stationary electrical induction apparatus are fluid cooled. Cooling ducts are formed in the magnetic core and electrical windings and cooling fluid passes through these ducts by natural convection flow or by forced fluid flow. In forced fluid flow the cooling fluid is forced through the cooling ducts by pumps, and typically, the flow of fluid through the cooling ducts is laminar in order to keep pumping costs down.

By virtue of the fact that all the heat produced in the electrical induction apparatus must be removed, a given electrical induction apparatus cannot be operated beyond a fixed maximum load. This is because the cooling systern is designed to remove what heat is produced at maximum load, and not much more. If the load is increased beyond the fixed maximum rating, the cooling system is inadequate to remove all the heat produced, and the electrical winding insulation may be destroyed.

The amount of heat that the cooling system is capable of removing can sometimes be increased by varying the cooling duct dimensions or increasing the amount of cooling fluid circulated. However, the problem of adequate heat removal has not been found to be so relatively simple, but depends upon many considerations. Decreasing the cooling duct dimensions will increase the amount of heat that can be removed. However, electrical considerations may demand that the cooling duct dimensions be relatively large and fixed values. Increasing the amount of cooling fluid circulated will also increase the amount of heat that can be removed, but if the amount of cooling fluid circulated is increased the costs of pumping the cooling fluid are concomitantly increased.

It is an object of my invention to provide improved cooling means whereby the cooling system of stationary electrical induction apparatus is capable of greater heat removal permitting operation of the apparatus beyond maximum rated load.

It is a further object of my invention to provide improved cooling means for stationary electrical induction apparatus at a minumum of cost without increasing the amount of cooling fluid circulated or varying the cooling duct dimensions.

I have discovered that in conventional stationary electrical induction apparatus with fixed duct dimensions and rate of flow of cooling fluid the amount of heat the cooling system is capable of removing can be increased by the addition of turbulence promoters in the cooling ducts.

My invention consists of the introduction of appropriately placed restrictions or turbulence promoters in the cooling ducts of stationary electrical induction apparatus, said promoters increasing the amount of heat the cooling system is capable of removing without any change in the cooling duct dimensions or the amount of cooling fluid circulated.

States Patent 2,912,658 Patented Nov. 10, 1959 The addition of turbulence promoters in the cooling ducts, where the maximum rated output of the apparatus is not exceeded, has the eifect of reducing the temperature of the apparatus. If the temperature of the apparatus is reduced, obviously, then the load on the apparatus can be safely increased beyond the rated output. However, my inventon is useful even where it is not desired to overload the apparatus. For instance, frequently local hot spots occur in the apparatus even when the apparatus is not overloaded. It is desirable to reduce such localized hot spots. I have discovered that the introduction of an appropriately spaced continuous restriction in the area of the localized hot spot will reduce hot-spot temperature.

Therefore, my invention also consists of the introduction of appropriately placed restrictions in the cooling ducts to reduce localized hot spots.

My invention has numerous advantages. For instance, the amount of heat that can be removed by the cooling system of any given stationary electrical induction apparatus can be increased at a slight cost, as contrasted to the high costs of altering the cooling duct dimensions or increasing the amount of cooling fluid circulated. With my improved cooling means, due to the fact that the amount of heat removed by the cooling system of a given stationary electrical induction apparatus can be increased, the rated safe output in a given electrical induction apparatus can be safely exceeded. That is, at a minimum of cost, the safe operating load of an apparatus can be exceeded without harm to the apparatus. Conversely, my invention permits a reduction in the size of stationary electrical apparatus. With my invention, because the amount of heat removed can be increased, a smaller apparatus with turbulence promoters will give the output of a larger apparatus with unrestricted cooling ducts.

The features of my invention which I believe to be novel are set forth with particularity in the appended claims. My invention itself, however, both as to its organization and use, together with further objects and advantages thereof, may be best understood by reference to the following description and accompanying drawings.

In the drawings, Figure 1 represents a sectional View of one form of my invention as applied to a stationary electrical induction apparatus having a magnetic core and barrel-type windings. Figure 2 is a view in perspective of the turbulence promoters used in the electrical windings cooling ducts of Figure 1. Figure 3 is a view in perspective of the turbulence promoters used in the core cooling ducts of Figure 1. Figure 4 is another embodiment of my invention wherein the legs of an integrally interconnected series of U-shaped sections serve as the turbulence promoters. Figure 5 is still another modified type of fluid flow restriction in which the turbulence promoter is spirally wrapped. Figure 6 is a view of a sleeve arrangement for producing increased cooling in a localized region to reduce hot spots. Figure 7 is a sectional view of my invention as applied to a stationary electrical induction apparatus with disc windings. Figure 8 is a view of my invent-ion as applied to helical electrical windings.

Referring now to the form of the invention illustrated in Figures 1 to 3, there is shown in Figure l a sectional view of a stationary electrical induction apparatus, which in this case is a transformer 1 enclosed in a casing or tank structure 2. Inside of the casing 2 is positioned a magnetic core 3, around each of the winding legs of which are positioned a plurality of electrical windings. An insulating barrier in the form of a cylinder 4 surrounds each leg of the magnetic core, and an electrical winding 5 of the barrel type is positioned radially outward of insulating cylinder 4 and is separated therefrom by an axial duct 6. A second insulating cylinder 7 is positioned radially outward of barrel winding and is separated from winding 5 by an axially extending duct 8. A second barrel-type winding 9 is positioned radially outward of insulating cylinder 7 and is separated from insulating cylinder 7 by an axially eX- tending duct iii. A third insulating cylinder 11 is positioned radially outward of winding 9 and spaced therefrom by an axially extending duct 12. Thus, it is seen that the plurality of electrical windings and insulating barriers are spaced from each other in concentric telescopic fashion, with the surfaces of the electrical windings being spaced from adjacent insulating barrier surfaces to form cooling ducts.

The windings and insulating cylinders are supported at their lower ends by a suitable support member 13, which may be a metal member conforming at its radially inner portion to theperipheral outline of the core legs, and at its radially outer portion to the peripheral outline of the tank structure. An inlet pipe 14 is provided at the lower end of the tank structure and is the means by which a fluid insulating and cooling medium is admitted to the lower portion of the tank from a heat exchanger, not shown- An outlet pipe 15 is provided at the upper end of the tank and is the means by which the cooling and insulating fluid leaves the talk to the heat exchanger. Suitable apertures 16 are provided in the support member 13 to conform with the

ducts

6, 8, 19, and 12. and are the means by which the cooling and insulating fluid passes from the lower portion of the tank up into the ducts between the windings and insulatin g barriers.

in accordance with my invention, I provide a restrictive arrangement in the ducts which permits a much greater cooling effect for a duct of a given radial thickness and for a given volumetric time rate of flow of cooling and insulating fluid than is attainable in unrestricted ducts. The restrictive means comprises annular members 17 which may be made of any suitable insulating material. By the term annular I include any restrictive member interposed in the cooling ducts and conforming to the contours of the ducts. For instance, the ducts may be circular, rectangular, or oval in cross section. Accordingly, annular members 17 will conform to the circular, rectangular or oval outline of the ducts. Furthermore, the annular restrictions need not necessarily extend continuously in one piece around the periphcry of the ducts, but instead may be discontinuous.

The annular members 17 abut against the surfaces of the insulating cylinders. However, the annular members 17 can also be arranged to abut the windings instead of the insulating cylinders. a

As will be best seen in Figure 2, the annular membe'rs 17 pass through, by virtue of notches 19, and are supported by axially extending spacer members 13 which are positioned circumferentially in the ducts. The spacer members also serve to properly radially space the insulating cylinders 4 and windings 5.

it will be obvious that the promoters need not always abut the insulating cylinders. For instance, one prometer may abut theinsulating cylinder, and the next succeeding promoter may abut the electrical Winding. This can be readily accomplished by forming notches 19 first on the face of spacer 18 facing the insulating barrier 4 and then on the face of spacer 18 facing the winding 5. middle of the duct. That is, supporting holes for the promoters can be formed in the spacers between .posite sides thereof so that the promoters lie in ddle of the duct and do not abut either the insulating cylinder t or electrical winding 5.

in Figures 2 and 2 the cooling ducts are formed by an electrical winding and an adjacent but spaced insulating barrier. However, my invention is also appli- Also, the promoters can be mounted'in the.

A cable where two electrical windings are spaced from each other by axial spacers and form a cooling duct therebetween.

Referring again to Figure 1, it will 'be noted that the core 3 also has cooling ducts Zii formed therein. Magnetic cores are conventionally formed out of laminated metal sheets. Spacing the laminations provides cooling ducts 20. As in the electrical windings, turbulence promoters 21 are provided in the cooling ducts the magnetic core. As shown in Figure 3, in conventional transformers, the laminations forming the core leg and the cooling ducts typically are spaced by buttons or lugs 22. The turbulence promoters 21 are metal strips welded to one of the laminations. The cooling fluid which enters tank 2, Figure 1, through inlet 14 passes beneath the lower flange of supporting plate 13 and then enters the core cooling ducts 2i Eventually the cooling fluid leaves the ducts 29 at' the top of the magnetic core and passes out of tank 2 through exit pipe 15 to the heat exchanger, not shown.

There is shown in Figure 4 a modified structure which may be used in place of the annular restriction members 17 and spacers 18 of Figures 1 and 2. In Figure 4 a plurality of spacer and restriction members are in abutting relation to the outer surface of an insulating cylinder 23 and also in abutting relation to the radially inner surface of a winding which is not shown. Each spacer and restriction member is a strip comprising a series of alternating

portions

24 and 25, with the width of portions 24 equal to the width of the duct and the width of portions 25 equal to the restriction which is to be placed in the duct. Portions 25 are bent so as to extend circumferentially around the cylinder 23. Portions 24 extend parallel to each other in the axial direction, and any.v

two immediately succeeding portions 24 are spaced circumferentially.

Viewed in another manner, each strip is a series of integrally interconnected U-shaped sections. The bases 24 0f the U-shaped sections serve as axially extending spacer members, and the legs 25 of the U-shaped sections, suitably cut out to the desired restriction dimensions, serve as the transversely extending restriction members. Each of the ducts has a plurality of such strips circumferentially spaced therein.

Each of the portions or members 24- is provided with a circumferentially protruding tab 26, and an axial member 27 overlies tabs 26 and bears against the portions 24 to help maintain the strips in position.

There is shown in Figure 5 another embodiment of my invention. In this embodiment the duct restriction is in the form of a spirally woundmember 28. The member 28 is supported by axial spacer members 29 which also space insulating cylinder 40 and electrical winding 41.

There is shown in Figure 6 a further modification in which the duct restriction is in the form of at least one sleeve member 45. The sleeve member 45 differs from the turbulence producing restrictions previously described in that the length of the restriction member 45 is considerably greater than the duct width, and has particular utility in connection with temperature reduction of localized hot spots. As in prior embodiments, the restriction members 45 are supported by axial spacer members 43 which also space insulating cylinder 42 and electrical windings 44.

There is shown in Figure 7 another application of my invention. In this instance the electrical windings are of the disc type. In the disc type of electrical winding a single conductor is wound radially outward into a plurality of discs 34 and the discs are stacked on top of each other. Separating the disc windings are insulating discs 32.

Members

30 and 31 are cylindrical insulating cylinders. The stacked discs 34 and insulating cylinder 31 define a cooling duct 35. Each alternate disc 33 is larger than disc 32 and protrudes into the cooling duct and serves as the turbulence promoter. As in prior embodiments axial spacers space insulating cylinder 31 and the stacked discs 34 and are suitably cut out to receive the protruding turbulence promoters 33.

In Figure 8 is illustrated a helical electrical winding and my invention applied thereto. In a helical electrical winding a plurality of electrical conductors are simultaneously spirally wound on an insulating barrier. In Figure 8 the electrical winding 36 is wound on insulating barrier 37 with adjacent turns of the electrical winding spaced by insulating disc material. Protruding turbulence promoter 38 is wound for one turn, every other turn of the insulating disc material. One of the axial spacers 39 is suitably notched to receive the ends of each turn of promoter disc 38. If the axial spacer 39 were not present, the cooling fluid would have a tendency to pass through the openings defined by the spaced ends of each turn of promoter 38. The axial spacer 39 prohibits this and forces the cooling fluid to pass over the promoters. Also, spacers 39 axially space windings 36 and an adjacent insulating barrier, not shown, to form the cooling duct.

In an unrestricted cooling duct the cooling fluid has a velocity in the axial or longitudinal direction of the duct. As before stated, in conventional cooling systems, the flow of fluid typically is laminar. This is because electrical considerations demand that the duct width be relatively large and in order to keep pumping costs down, the fluid is forced through the cooling ducts at a relatively small velocity. In the practice of my invention, the only change made over conventional cooling systems is the addition of turbulence promoters. There is no change made in the duct dimensions or quantity of cooling fluid circulated per unit time. With such a slight modification at a very low cost, the output of transformers embodying my invention may be safely increased beyond present maximum ratings. My turbulence promoters make this possible by producing turbulence within the cooling ducts. That is, besides a velocity component in the axial direction, there is a velocity component in the radial direction. Thus, the relatively hot cooling fluid adjacent to the electrical windings by turbulence is caused to mix with the relatively cooler cooling fluid further removed from the surface of the electrical windings. Simultaneously, the relatively cooler fluid has an opportunity to reach the winding surfaces. Because of this, a cooling system embodying my invention is capable of removing more heat and cools the electrical windings. My invention can be used to reduce winding surface temperature when no increase in rated output of the electrical induction apparatus is contemplated. For instance, hot spots can be reduced. Also, if the electrical winding temperature can be reduced it is possible to use a cheaper grade of insulation for the electrical windings. A still more profitable use of my increased cooling effect is to increase the rated output of conventional transformers without exceeding permissible electrical winding temperatures. Also, with my improved cooling system a smaller transformer can give the output of a larger transformer with unrestricted cooling ducts. That is, a saving in space and weight can be realized.

It is also within the contemplation of my invention to grade my promoters. The downstream temperature of the cooling fluid is obviously higher than the temperature of the cooling fluid near the inlet to the cooling ducts. Consequently, as one progresses downstream in the cooling ducts, the promoters can be made progressively wider toobtain greater turbulence.

The distance between two succeeding promoters should preferably be such that the second promoter will cause turbulence before the turbulence promoted by the first promoter has, lost its effectiveness. If the promoters are too close together turbulence will not be induced, but the flow of fluid will be laminar and fluid will tend to stagnate between promoters. it the promoters are too far apart, laminar flow will be established before the next promoter is reached.

Disclosed are various embodiments of my invention as applied to barrel, disc, and helical electrical windings. Also the windings and insulating cylinders have been shown as being of a cylindrical configuration. However, my invention can be applied to oval or rectangular windings and insulating cylinders. Also, it will be obvious that the described embodiments are illustrative only of my invention and that other forms of spacers and turbulence promoters and methods of practicing my invention can be used. Therefore, I do not intend to be limited by the forms disclosed. What I believe to be my invention I have set forth with particularity in the appended claims.

What I claim as new and desire to secure by Letters Parent of the United States is:

1. In an electrical induction apparatus having a plurality of barrel-type electrical windings, cooling means for said windings comprising insulating barriers alternated with said windings and telescopically spaced from adjacent winding surfaces to form a plurality of axially extending cooling ducts, axially extending spacer members circumferentially located in said ducts and abutting adjacent insulating barrier and winding surfaces to radially space them, means for forcing a cooling fluid through said ducts at low velocity, means in said ducts for increasing the the amount of heat that can be removed from the surface of said windings by periodically causing turbulent flow, said last mentioned means comprising transverse extending turbulence promoting members partially obstructing said ducts and periodically located along the length of said ducts, said transverse members being so proportioned relative to the duct widths as to periodically produce turbulent flow, said transverse members in said ducts supported by said axially extending spacer members.

2. In an electrical induction apparatus as in claim 1, wherein said transverse turbulence promoting members are continuous annular rings lying in planes perpendicular to the axis of said ducts, a plurality of said rings periodically located along the length of each of said ducts.

3. In a fluid cooled electrical induction apparatus having a plurality of barrel-type electrical windings cooling means for the windings, comprising a plurality of insulating barriers telescoped with the electrical windings and concentric therewith, each insulating barrier surface being spaced from the adjacent electrical winding surface to form an axially extending cooling duct therebetween, means for producing a flow of cooling fluid in said ducts, restriction means in the ducts partially obstructing said ducts and adapted to periodically produce a velocity component of said fluid perpendicular to said windings, and axially extending spacer members spacing the adjacent surfaces of the windings and insulating barriers, said restriction means comprising transverse members conforming to the peripheral contours of the ducts and supported therein by said axially extending spacer members, said transverse members comprising a plurality of rings, conforming to the peripheral outline of said ducts and lying in a plane normal to the axis of said ducts, the rings within each duct being spaced along the length thereof.

References Cited in the file of this patent UNITED STATES PATENTS 1,141,199 Moody June 1, 1915 2,339,625 De Blieux Ian. 18, 1944 2,388,566 Paluev 'Nov. 6, 1945 FOREIGN PATENTS 405,512 France Jan. 6, 1910 493,431 France Aug. 8, 1919 353,774 Germany May 30, 1922 269,933 Great Britain Feb. 2, 1928 235,837 Switzerland May 16, 1945