US2525457A - Liquid cooling means for electrical apparatus - Google Patents

Description

Oct. l0, 1950 K. K. PALUEv LIQUID COOLING MEANS FOR ELECTRICAL APPARATUS Filed Feb. 15, 1944 Inventor: Konstantin Kpaluev,

His Attorney.

` as oil.

Patented Oct. 10, 1950 LIQUID COOLING MEANS FOR ELECTRICAL APPARATUS Konstantin K. Paluev, Pittsfield, Mass., assignor to General Electric Company, a' corporation of New York Application February 15, 1944, Serial No. 522,519 1 Claim. (Cl. 174-15) My invention relates to an electrical apparatus and to a circulating system for an electrical induction apparatus.

Heretofore it has been customary to manufacture electrical induction apparatus such as transformers of the enclosed type having a winding with suitable cooling ducts within anenclosing casing which is filled with a dielectric fluid such In order to provide a, cooling arrangement for the oil a heat exchanger arrangement is connected to the casing so that the hot oil which passes through the winding ducts may pass through the heat exchanger and give up the heat which has been received from the winding. Such systems have either depended upon the natural circulation effect due to the difference in temperature between the bottom and top of the transformer casing or an auxiliary pump has been provided for forcing the cooling iiuid through the Winding ducts and through the heat exchanger and back to the winding ducts again.'

It is an object of my invention to provide an electrical induction apparatus of the above mentioned type with an improved arrangement for circulating the cooling and dielectric fluid through the apparatus.

A further object of my invention is to provide a fluid immersed electrical induction apparatus which is thermally efficient in operation.Y

A still further object of my invention is to provide an electrical apparatus having a loss producing element and a heat exchanger for cooling the dielectric fluid within the apparatus with an improved arrangement for circulating the dielectric fluid 'through the apparatus.

Further objects and advantages of my invention will become apparent from the following description referring to the accompanying drawing, and the features of novelty which characterize my invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

In the drawing Fig. 1 is a sectional side elevation of an electrical induction Yapparatus which is provided with an embodiment o f my invention, and Fig. 2 illustrates a modification of the construction illustrated in Fig. l.

In the design of electrical induction apparatus such as transformers, windings are provided which have a copper cross section dependent upon the electrical characteristics of the apparatus. Also, in order to cool the winding it is conventional to provide ducts between the various coils, and when concentric cylindrical windings are used ducts are usually provided between the cylindrical windings. The higher the normal operating voltage between the coils or concentric windings the wider must the ducts be in order to provide the desirable insulation characteristics between the windings so as to prevent electrical failure.

The design of efficient coolers or heat exchange arrangements to' be used'with transformers, however, is not dependent upon electrical characteristics but isv dependent upon thermal phenomena and considerations of economy, and it has been lcustomary to employ a fairly large number vof cooling tubes in series, and each cooler design requires a certain optimum velocity of the circulating fluid in the tubes. Thus, it is known that the amount of heat exchange between a surface and a fluid is proportional to fluid velocity. `But the power required for fluid flow increases approximately as the third power of its velocity, so the optimum velocity is dependent upon thermal as well as economical considerations, Thus given an area of cross section through which the cooling oil passes and the optimum velocity to obtain a cooler with the best overallv efficiency, a certain quantity of oil will flow into the intake manifold of the cooler and be exhausted from the output of the cooler.

I have determined, however, that the amount of oil flow through the cooler determined by the characteristics mentioned above may be quite different from the optimum quantity of oil flow through the winding ducts, and in conventional transformer constructions since the cooler is connected in a recirculating system so that the oil flows from the casing through the cooler and back to the casing, the oil flow through this series system may be quite different from the optimum `quantity of oil flow through either the cooler or` winding ducts. This is particularly true in the so called directed flow transformers where baffles are used kbetween the winding and the outside of the casing so that all the oil which is` exhausted from the cooler and passes into the transformer casing must pass through th various winding ducts. y y In the arrangements illustrated in the drawing I provide ways of circulating the oil or cooling dielectric fluid through the winding ducts and at the optimum quantity and velocity for the design of the winding and through the cooler atthe optimum quantity and velocity depending upon the cooler construction, and these two optimum values may be and are usually quite different, particularly in directed flow transformers.

`lteferring more particularly to Fig. l of the vdicated by the dotted line arrows.

drawing, I have provided an electrical apparatus which includes a core having winding legs I and II and with windings I2 and I3 surrounding the winding legs. The windings illustrated in the drawing are of the concentric cylindrical type and are provided with ducts for carrying iluid in 'heat exchange relation with the windings. In the construction illustrated in the drawing it will be seen that two concentric ducts I4 are provided which extend axially through the winding I3 and two concentric ducts I5 which extend axially through the winding I2, but it is to be understood that any suitable number of ducts may be provided. In order to provide what is called directed flow insulating cylinders I6 and I1 are placed around the windings I3 and I2, respectively, and a partition or coil support I8 is placed under the windings and extends to the cylinders. The partition is provided with suitable openings in registry with the ducts. The core and coils are placed in a casing and the cylinders I6 and I1 extend from the bottom 2l of the casing so that the cylinders provide a partition arrangement between the windings and the casing. A suitable dielectric fluid such as oil or gas may be placed in the'casing 20.

In order to provide a convenient arrangement for cooling the dielectric iluid a heat exchanger means 23 is provided which is fluidly connected to the casing by pipes 24 and 25. The fluid may be forced through the circulating system by a pump 26 which is operated in any suitable manner such as by an electric motor 21. Thus the fluid may be withdrawn from the casing 20 through the pipes 24 as is indicated by the arrows, pass through the heat exchanger and be discharged into the casing through the pipe 25. The pump 26 may have such characteristics as determined by the cooler 23 so that the oil will pass through the cooler at the optimum velocity and quantity for the particular cooler design. As shown, the pump 26 is of the centrifugal type which is characterized by a relatively high pressure head and a relatively low flow. This is especially suitable for forcing cooling liquid through a cooling radiator as the latter often has a relatively high hydraulic resistance and does not require a large ilow of liquid through it in order to obtain optimum cooling.

In order to circulate the dielectric and cooling fluid through the winding ducts at the optimum velocity and quantity determined by the winding design, I provide a second pump means 30 which forces the oil from the area between the partitions I5 and I1 and the casing 20 into the bottom of the ducts and so that the oil will pass through the winding ducts at the optimum velocity and quantity depending upon the area and characteristics of the winding. This circulation is in- As shown, pump 30 is of the propeller type which is characterized by a relatively low pressure head and a relatively high ilow. This is especially suitable for circulating cooling liquid through winding ducts at the optimum rate for cooling. It will therefore be seen that I have provided a circulatory system including the ducts and two parallel return paths, one return path being between the partition I6 and I1 and the casting 20 and the second return path being through the cooler, or the uid may be pumped from the pipe 24 through the cooler and to the casing at one rate and through the ducts at another rate. Thus, for example, the flow through the winding ducts may be 4000 gallons per minute while 4 the ilow through the heat exchanger may be 1000 gallons per minute.

In the construction illustrated in Fig. 2 I have shown a modication of the system of Fig. 1 including windings 35 and 3S which have ducts 3 1 and 38 respectively. The windings are provided in a casing 40 and a heat exchanger 4I is connected to the casing 40 through pipes 42 and 43. In order to force the cooling fluid through the heat exchanger I provide a pump 44, similar to pump 26, which may be operated through an electric motor 45. In order to provide what is called directed ow, a baille 46 is provided at the bottom of the winding and which extends from the outer surface of the windings to the casing. The baille, however, is provided with suitable openings which communicate with each one of the ducts. Thus oil below the baille 46 in order to reach the other side of the baffle must pass through the winding ducts.

In order t0 provide a convenient arrangement for circulating the iluid dielectric within the casing at its optimum velocity and volume, I provide a second pump 41, similar to pump 30, which operates in an opening 48 in the baille. The pump 41 may be operated in any suitable manner and in the construction illustrated in Fig. 2 I provide a turbine impeller or bladed wheel arrangement 49 which is rotated by the movement of the fluid due to the pump 44. Thus a directing baille 50 is provided which communicates with the pipe 43 so that the fluid which is discharged from the pipe 43 is directed against the impeller 49 causing it to rotate. Thus when the pump 44 is operated iluid will be withdrawn from the casing 40 through the pipe 42 as is indicated by the arrows and be discharged into the casing 40 through the pipe 43. At the same time due to the rotation of the second pump 41, oil will pass through the opening 48 as indicated by the dotted line arrows and up through the various winding ducts 31 and 38. Thus the fluid flow in the windings will be the sum of the ilows of the pumps. It will be understood that here again by suitably designing the pump the iluid may be forced through the ducts and through the heat exchanger at predetermined rates depending upon the characteristics of the winding and cooler. It will be noted that in the system of Fig. 2 the fluid is exhausted below the baille so that the uid flowing through the cooler will ilow through the ducts, while in Fig. 1 the fluid is exhausted from the pump through the pipe 25 between the baille and casing. Thus in the Fig. 2 construction if,

: for example, the flow through the winding ducts vis 4000 gallons per minute and that through the heat exchanger is 1000 gallons per minute,

Y the ilow through the opening 48 will be the difierencev or 3000 gallons per minute.

Although I have shown and described particular embodiments of my invention, I do not desire to be limited to the particular embodiments described, and I intend inthe appended claim to cover all modifications which do not depart from the spirit and scope of my invention.

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

A transformer comprising, in combination, an enclosing tank, a winding assembly therein, a normally vertical duct in said winding assemby, a partition in said tank forming a substantially closed bottom compartment therein having a top opening communicating with the bottom end of said duct, a dielectric cooling liquid substantially filling said tank, a cooling radiator outside said tank, a centrifugal pump connected to force said liquid through said radiator by withdrawing it near the top of said tank and discharging it into said tank near the bottom thereof and outside of said compartment, and a pr/opeller type pump mounted in another opening in said partition for circulating said liquid through said duct by propelling it from outside said compartment into said compartment.

KONSTANTIN K. PALUEV.

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

Number Number 6 UNITED STATES PATENTS Name Date Baxter Dec. 19, 1882 Nichols May 25, 1915 Hodtum Mar. 26, 1929 MacLeod May 5, 1931 Clarke Dec. 8, 1931 Knotts et al Aug. 16, 1949 FOREIGN PATENTS Country Date England June 29, 1928

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