US2479373A - Cooling system for electrical apparatus - Google Patents

Description

Aug. 16, 1949. c. 1 KNo'rTs ETAI. 2,479,373

COOLING SYSTEM FOR ELECTRICAL APPARATUS Filed Oct. 27, 1943 ATTOR Patented Aug. 16, 19749 COOLING SYSTEM FOB ELECTRICAL APPARATUS charles L. Knotts and any L. mwa, assignors to Westinghouse Electric Sharon, Pa., Corporation,

`East Pittsburgh, Pa., a corporation o! Pennsylvania Application October 27, 1943, Serial No. 507,818 17 Claims. (Cl. 174-15) Our invention relates to coolling systems for electrical apparatus and, more particularly, to cooling systems employing means for circulating the cooling fluid at a more rapid rate than it would naturally flow by thermal siphon action alone.

The application of radiators or coolers to liquid illled transformers as a means of disslpating heat in the transformer is well known, and for the purpose of carrying out our invention, any suitable radiator bank construction may be utilized.W4

It often occurs in the operation of electrical apparatus, such as transformers, that the natural circulation of the cooling andinsulating liquid through the transformerv tank and radiators by thermal action alone is inadequate to dissipate enough heat to keep the transformer suiilciently xootll for safe operation, particularly during peak oa s. v 'I'he heat dissipated by the windings and core of a transformer is a function of the load on the transformer. In a liquid cooled transformer having a radiator-type cooling system, the heat is conveyed first from the windings and core to the liquid, and then as the liquid circulates throughl the system, from the liquid through the walls of the transformer tank and the radiator walls to. the surrounding medium, which is usually air. It has been found desirable to operate the copper of the transformer windings at or below a certain predetermined temperature. The greater the capacity of the cooling system for dissipating the heat generated by the flow of current through the transformer windings the greater is the safe load that may be carried on a given transformer. y

In a transformer cooled by natural convection where there is no forced flow of the cooling medium, the circulation of the cooling iiuid is very slow through the cooling ducts provided between the windings. This results in a large difference in temperature between the average temperature f the copper in the coil and the average temperature of the cooling fluid. If the rate of flow of the cooling fluid can be increased to the point where there is no stationary lm of oil remaining on the coil surface, the temperature gradient between the coil and oil will be greatly reduced.

When the cooling liquid is circulated through the cooling ducts of the electrical apparatus being cooled and through an external cooler in the form of a radiator, the economic rate of circulation of the fluid to get the desired apparent cooling of the apparatus does not require a sumcient- 2 ly rapid rate of ow of the cooling liquid to provide the maximum possible reduction in temperature gradient between the copper conductors of the winding and the circulating fluid. If the fluid is circulated through the radiator at a. sufciently rapid rate to get a small temperature difference between the cooling liquid and the copper a large pressure drop results which requires a large motor and pump to cause, the forced circulation of the cooling liquid.

Our invention contemplates the circulation of cooling liquid by gravity or thermal action caused by changes in its temperature. Our invention also contemplates the additional means for increasing the rate of circulation through the transformer and cooler for bringing this liquid more rapidly into heat-exchanging relation with the outside cooling medium, such as air. It contemplates further the provision of a. by-pass co'nduit for permitting a portion of the cooling liquid to flow from the upper part of the apparatus casing to the lower part thereof without restricting the rate of iiow which results when all the liquid flows through the cooling elements of the radiator, thus reducing appreciably the amount of power required to cause the desired rate of flow -of the cooling liquid through the cooling ducts of the apparatus below that which would be required where all of this liquid is required to flow through the cooler or radiator of the cooling system.

An object of the invention is to provide a cooling system for electrical apparatus, such as transformers, employing cooling pipes or radi-V some power device, such ators spaced from the transformer tank and through winch the cooling liquid is circulated by as a motor-driven pump, and in providing means for circulating large quantities of the cooling liquid through the cooling ducts of the core and coil assembly and in circulating this fluid in part through a cooling radiator and in part through a by-pass path in parallel with the path of flow through the radiator.

Other objects and advantages of our invention will be apparent from the following description of preferred embodiments thereof, reference being had to the accompanying drawing, in which:

Figure l is a view partly in vertical section illustrating apparatus arranged in accordance with one embodiment of the invention; and

Fig. 2 is a view partly in vertical section illustrating apparatus arranged in accordance with another embodiment of the invention.

Refen'ing particularly to Fig. 1 of the drawing a tanker casing I is shown containing a transformer core comprising two separate core loops 2. each having the usual windows therein for accomodating the two vertical sides of a series of windings shown by the dotted outline 3. The core laminations are held between upper and lower end frames 4 and i the lower end frame being mounted upon the footings 3, and the two end frames being solidly held together bythe bracing and supporting members 1 in a well known-manner. Likewise vertical insulating barriers II are shown spaced between the vertically positioned coils 3 and having thereon spacer members I2 to separate the barriers slightly from the coil winding conductors to provide cooling ducts I3 between the coils and barriers through which the cooling liquid I4 in which the apparatus is immersed will flow along the lines indicated by the arrows. A baille or barrier is provided for preventing the circulation of oil upwardly about the apparatus without passing through the cooling ducts, and may consist of an outwardly extending member I6 about the lower part of the transformer core structure which registers with an inwardly extending Bange I1 shown mounted on the wall of the casing I. Sufl;.

' cient cooling ducts willbe provided to provide a slight flow of the cooling liquid upwardly in the space above the'barrier I6-I1 to prevent a dead area in this region.

A cooler is provided which, in the form illustrated, is shown as having an upper header 2| and a lower header 22 connected to the upper and lower parts, respectively, of the transformer casing above and below the barrier I6--I1. Cooler elements 23 are provided between the headers 2I and 22 through which the cooling liquid flows downwardly as indicated by the arrows. A pump 24 is provided for causing a forced circulation of the cooling liquid through the circuit including the cooling ducts I3 of the apparatus and the cooling elements 23 of the cooler 20.

A by-pass conduit 25 is illustrated, the upper end of which connects with the transformer casing above the barrier IB--Il and the lower end of which delivers cooling liquid to the bottomof the tank below the barrier. A pump 26 .is illustrated for providing forced circulation of the cooling liquid through the by-pass conduit 25.

By circulating the oil or similar cooling liquid causing a portion of it to pass through the cooler 20 and another portion to pass through the bypass pipe 25, the cooling liquid will pass upwardly through the cooling ducts I3 at a more rapid rate than would be the case if the liquid in the cooling system were circulated by thermal siphon action alone. Thus, the temperature of the cooling liquid at the top and at the bottom of the transformer tank will be more nearly at the same temperature, and the various parts of the winding being cooled by the upward iiow of this liquid through the ducts I3 will likewise be more nearly at the same temperature. This allows the average temperature of the winding to be nearly the same as the top of the winding which is normally the hottest spot of the winding.

Since the by-pass passage through the pipe 25 is relatively large in cross-section and offers a relatively low resistance to the flow of iiuid therethrough as compared to the resistance offered in forcing the cooling fluid through the vertical pipes 23 of the cooler 20, the amount of power required to operate the pumps 24 and 26 is very much less for the same rate of flow of cooling liquid through the cooling duets I3 than would be the case if all of this liquid is required to flow through the cooler 20. By varying.the rate of operation of the pumps 24 and 2B, the ow of nuid may be adjusted so that a relatively larger or smaller portion of the iiow of uid passesthrough the cooler 20 depending upon the load of the transformer and the required cooling capacity of the system as a whole. The total capacity of the transformer is, therefore, very greatly increased, and the amount of forced ow of the cooling liquid can be varied to be increased under peak loads and reduced when the loads are lighter. v r

In the embodiment of the invention illustrated in Fig. 1, two separate motor-driven pumps 24 and 26 are employed which are independently operated, a part of the cooling liquid being forced through the cooler 20, by the pump" 24, and a part of the cooling liquid being forced through the by-pass pipe 25 by the pump 26. In the embodiment of the invention illustrated in Fig. 2, the by-pass path is shown as a pipe 3| having a relatively large cross-sectional area and extending between the headers 2l and 22 in parallel with the cooling elements 23 of the radiator or cooler 20. In this embodiment of the invention, the same pump 24 causes the iiow of fluid through both the by-pass pipe 3l and the cooler elements 23 of the radiator. A valve 32 is shown for varying the size of the passageway from the header 2| into the pipe 3I to adjust the amount of the cooling liquid that passes through the by-pass pipe relative to that which passes through the cooler elements 23 of thev radiator 20.

Although for purposes of simplicity of illustration the radiator 20, as illustrated in the two' figures, is shown as having relatively few vertical cooling elements 23, it will be appreciated that the size of such radiators frequently becomesvery large and they may be divided up into a number of diierent radiator units instead of in the single unit as shown.

In the illustrated transformers the iiow of the cooling liquid within tank is upwardly from the bottom to the top and then downwardly through the cooler or the by-pass path. In some transformers the direction of flow is horizontal rather than vertical. That is, the transformer structure is, in effect, on its side so that the general direction of the cooling ducts is horizontal instead of vertical, and the general direction of the cooler elements is also horizontal instead of vertical. The liquid, in such units, nows horizontally from one end of the tank to the other instead of vertically from one end of the tank' to the other.

In the drawing the shell form of transformer is illustrated. It will be apparent that the invention may be applied to the core form of transformer also where the oil is forced through cooling ducts and guided by means of bailles.

Since modifications in the apparatus illustrated will occur to those skilled in the art withinthe spirit of our invention. we do not wish to be limited otherwise than by the scope of the appended claims.

We claim as our invention:

1. In combination with an electrical apparatus housed within a tank containing cooling liquid, a cooler for said apparatus comprising a plurality of spaced vertically extending liquid conducting elements mounted adjacent the tank and having their upper and lower ends connected to the tank by fluid conducting conduits near the top and the bottom of the tank to provide a path for permitting the circulation of cooling liquid through the tank and cooler, means for providing s a by-pass path separate from and independent of the path through the cooler for the circulation of cooling liquid from the upper part to the lower 'partofthetankinparallelwiththepaththrough the cooler, and motive means for forcing the circulation of the cooling vliquid through both of said circulating paths.

3. In combination with an electrical apparatus housed within a cooling liquid, a cooler for said appartu comprising a plurality of spaced vertically extending liquid conductin elements mounted adjacent the tank and having their upper and lower ends connected to the tank by iiuid conducting conduits near the top and bottom of the tank to provide a path for permitting the circulation of cooling liquid through the tank and cooler, means for providing a bypass path for the circulation of cooling liquid from the upper part'to the lower part of the tank in parallel with the path through the cooler,

motive means for forcing the circulation of the u cooling liquid through both of said circulating paths, and means for varying the pressure head Vrelative to each other along the two paths of liquid flow from the top to the bottom of the tank containing the electrical apparatus.

3. In combination with an electrical apparatus housed within a tank containing cooling liquid, a cooler for said apparatus comprising a plurality of spaced vertically extending liquid conducting .elements mounted adjacent the tank and having their upper and lower ends connected to the tank -by iluid conducting conduits near the top and the bottom of the tank to provide a path for permitting the circulation of liquid through the tank and cooler, means for providing a by-pass path for the circulation ofq'ooling liquid from the upper to the lower parts of the tank in parallel with the path through the cooler, motive means for forcing the circulation of the cooling liquid throughboth oi' said circulating paths, and valve means `for controlling the by-pass path for controlling the division of the cooling liquid between the path through the cooler and the path through the bypass.

4. In combination with an electrical apparatus horned within a tank containing cooling liquid, cooling ducts extending substantially vertically through the electrical apparatus for accommodating the ilow of the cooling liquid upwardly therethrough, a baii'ie`surrounding the apparatus between the apparatus and the tank wall for restraining flow upwardly past the apparatus except through the cooling ducts, a cooler for said apparatus comprising a plurality `of liquid conducting cooling elements mounted adjacent the tank with their upper and lower ends connected to the tank for conducting the ilow of cooling liquid from the upper part of the tank through the liquid conducting elements to the lower part of the tank, means for providing a vby-pass path separate from and independent of the path through the cooler for the circulation of cooling liquid from the upper part to the lower part of the tank in parallel with the path through the cooler, and motive means for forcing the circulation of the cooling liquid through both of said circulating paths.

5. In combination with an electrical apparatus vhoused within a tank containing cooling liquid,

cooling ducts extending substantially vertically through the electrical apparatus lfor accommodating the flow of the cooling liquid upwardlytherethrough, a bame surrounding the apparatus between the apparatus and the tank wall for re- 6 straining flow upwardlypast the apparatus except through the cooling` ducts. a cooler for said apparatus comprising a plurality of liquid conducting cooling elements mounted adjacent the tankvwith their upper and lower ends connected to the tank for conducting the ilow of cooling liquid from the upper'part oi.' the tank through the liquid conducting elements to the lower part oi' the tank, means for providing a by-pass path for the circulation oi' cooling liquid from the space above the bame to the space below Lthe balle for circulating a portionfof the cooling liquid through Ithe cooling ducts of the apparatus and through the by-pass path in parallel to the path of circulation through the elements of the cooler, motive means for forcing the circulation of cooling liquid through the by-pass path. and motive means for circulating cooling liquid through the path of circulation including the cooler elements and the f cooling ducts' of the apparatus.

6. In combination with an electrical apparatus housed within a tank containing cooling liquid, cooling ducts extending substantially vertically through the electrical apparatus for accommodating the flow of the cooling liquid upwardly therethrough, a baille surrounding the apparatus between the apparatus and the tank wall for restraining flow upwardly past the apparatus except through the cooling ducts, a cooler for said apparatus comprising upper and lower header members connected to the upper and lowerparts of the tank and extending outwardly therefrom and liquid conducting cooling elements having relatively small cross-sectional areas connected' between the upper and lower header members, a. by-pass conduit between the header g members having a relatively large cross-sectional area for conducting liquid betwen the header members in parallel relation to the fluid passing through the cooler elements, and motive means for forcing the circulation of cooling liquid through the cooling ducts of the apparatus, the header members and the liquid conducting cooler elements and by-pass conduit.

7. In com-bination with an electrical apparatus housed within a tank containing cooling liquid, the electrical apparatus being provided with cooling ducts for guiding the ow of cooling liquid therethrough, a. cooler for said apparatus comprising a plurality of spaced liquid conducting elements having relatively small cross-sectional areas mounted adjacent the tank and having their ends connected to provide a path for permitting the circulation of liquid through the tank and cooler, means for providing a by-pass path separate from and independent of the path through the cooler for the circulation of cooling liquid from one end to the other end of the tank in parallel with the path through the cooler, said by-pass path having a relatively large cross-sectional area, and motive means for forcing the circulation of the cooling liquid through both the cooler and the bv-passy path and through the cooling ducts of the apparatus.

8. In combination with an electrical apparatus housed within a tank containing cooling liquid, the electrical apparatus being provided with cooling ducts for guiding the flow of cooling liquid therethrough, a cooler for said apparatus comprising a plurality of spaced liquid conducting elements mounted adjacent the tank and havin! their upper and lower ends connected to provide a path for' permitting the circulation of liquid through the tank and cooler, means for providing a by-pass path for the circulation oi cooling v division of iiow of the cooling liquid between the path through the cooler and the path through the by-pass. l

9. In combination with an electrical apparatus housed within a tank containing cooling liquid, cooling ducts extending through the velectrical apparatus for accommodating the ilow of the cooling liquid therethrough, a baille surrounding the apparatus between the apparatus and the tank wall for restraining flow upwardly past the apparatus except through the cooling ducts, a cooler for said apparatus comprising cooling elements connected between the opposite ends of the tank to permit the ilow of the cooling liquid, a by-pass conduit between the opposite ends of the tank for permitting the ow of liquid in parallel relation to the uid passing through the cooler elements, motve" means for forcing the circulation vof coolingliquid through the cooling ducts of the apparatuslfthe header members and the liquid' conducting' 'cooler elements and bypass conduit, and valve means for controlling the division of ow of the cooling liquid between the cooler elements and the by-pass conduit.

10. In combination with an velectrical apparatus housed within a tank containing cooling liquid, a cooler for said apparatus comprising a plurality of spaced liquid conducting elements mounted adjacent the tank and having their opposite ends connected to the opposite ends of the tank by fluid conducting conduits to provide a path for permitting the circulation of liquid through the tank and cooler, means for providing a by-pass path for the circulation of cooling liquid `from the upper to the lower parts of the tank in parallel with the path through the cooler, motive means for forcing the circulation of the cooling liquid through both of said circulating paths, and means for varying the amount of cooling liquid that passes through the by'pass path relative to the amount of cooling liquid that passes through the path through the cooler from the one end to the other end of the tank containing the electrical apparatus.

11. In combination with an electrical apparatus housed within la tank containing cooling liquid,

cooling ducts extending through the electrical apparatus for accommodating the flow of the cooling liquid therethrough, a baille surrounding the apparatus between theapparatus and the tank wall for restraining flow past the apparatus except through the cooling ducts, a cooler for said apparatus comprising a plurality of liquid conducting cooling elements mounted adjacent the tank with their opposite ends connected to the tank for conducting the ow of cooling liquid from the one end of the tank through .the liquid conducting elements to the other end of the tank, means for providing a by-pass path for the circulation of cooling liquid from thefone end to the other end of the tank in parallel with the path through the cooler, motive means for forcing the circulation of the cooling liquid through both of said circulating paths, and means for varying the amount lof cooling liquid that passes through the by-pass path relative to the amount of cooling liquid that passes through the liquid conducting cooler elements,

i2. In combination with an electrical apparatus housed within a tank containing cooling liquid. cooling ducts extending through the electrical apparatus for accommodating the ilow of the cooling liquid therethrough, a baille surrounding the apparatus between the apparatus and the tank wall for restraining now upwardly past the apparatus except through the cooling ducts,.a cooler for said apparatus comprising a plurality of liquid conducting cooling elements mounted adjacent the tank with their opposite ends connected to the tank for conducting the ilow of cooling liquid from the one end of the tank through the liquid conducting elements tothe other end of the tank, means `for providing a by-pass path for the circulation of cooling liquid from the space on the one side cf the baille to the space on the opposite side of the baille for circulating a portion of the cooling liquid through the cooling ducts of the apparatus and through the by-pass path in parallel to the path of circulation through the elements of the cooler, motive means for forcing the circulation of cooling liquid through the by-pass path, motive means for circulating cooling liquid through the path of circulation including the cooler elements and the cooling ducts of the apparatus, and means for varying the amount of cooling liquid that passes through the by-pass path relative to the amount of cooling liquid that passes through the vpath including the cooler elements.

i 13. In an electrical apparatus, an enclosing casing, a winding within said casing, a winding duct in heat exchange relation with said winding, heat exchanger means, means'for iluidly connecting said heat exchanger means to said casing to provide a recirculating system, pump means for circulating a dielectric uid from said casing through said heat exchanger means and back to said casing, and means including a second pump for circulating a directed ow of the dielectric iluid through said duct to the exclusion of said heat exchanger.

14. In an electrical apparatus, an enclosing casing, a winding within the casing, a winding cooling duct in heat exchange relation to the winding, heat exchanger means, means for fluidly connecting said heat exchanger means to the casing to provide a path for permitting the circulation of a dielectric and cooling uid through the winding cooling duct within the casing and the heat exchanger, means for providing a bypass path for the circulation of dielectric and cooling Ailuid in parallel with the path through the heat exchanger means, and means for circulating the dielectric and cooling uid through the path including the exchanger at one rate of iluid ilow and throughsaid bypass path at a second rate of iluid ow different from the rst rate.

l5. In an electrical apparatus, an enclosing casing, a winding Within the casing, a winding cooling duct in heat exchange relation to the winding, heat exchanger means, means for fluidly connecting said heat exchanger means to the casing to provide a path for permitting the circulation of a dielectric and cooling uid from the upper part of the casing to the lower part of the casing through the heat exchanger means, means providing a bypass path for the circulation of dielectric and cooling uid from the upper part of the casing to the lower part of the casing separate from and independent of the path through the heat exchanger means, and motive means for forcing the circulation of the dielectric and cooling iiuid through said two circulatlng paths.

16. In an electrical apparatus, an enclosing casing, a winding within said casing, a winding duct in heat exchange relation with said wind ing, heat exchanger means, means for i'luidlyy connecting said heat exchanger means to said casing to. provide a recirculating system, pump means for circulating a dielectric fluid from said casing through said heat exchanger means and back to said casing, and a second pump means for circulating the dielectric fluid through said duct and between said winding and said casing so that the iiuid may flow at diiierent rates in said duct and in said heat exchanger means.

17. In an electrical apparatus, a substantially closed iiuid system containing a loss producing element and having heat r`exchanger means, a dielectric and cooling fluid within said closed iluid system, meansnfor circulatingsaid fluid through said heat exchanger means at a predetermined rate,vand means .for circulating said dielectric fluid in that part of said system containing said loss producing elementat a predetermined rate diiierent from the first mentioned predetermined rate.

CHARLES L. KNOT'IS. ROY L. BROWN.

REFERENCES CITED The following references are of record in the ille of this patent:

UNITED STATES PATENTS Number Name Date 1,083,945 Randall Jan. 13, 1914 1,706,574 Hodtum Mar. 26,1929 1,800,163 Thompson Apr. 7, 1931 15 1,835,470 Clarke Dec. 8, 1931 2,085,080 Brown June 29, 1937 2,341,058 Paluev Feb. 8, 1944 FOREIGN PATENTS n' Number Country Date 115,400 Switzerland Aug. 2, 1926

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