US2354159A - Cooling electrical apparatus - Google Patents

Cooling electrical apparatus Download PDF

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Publication number
US2354159A
US2354159A US358650A US35865040A US2354159A US 2354159 A US2354159 A US 2354159A US 358650 A US358650 A US 358650A US 35865040 A US35865040 A US 35865040A US 2354159 A US2354159 A US 2354159A
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United States
Prior art keywords
electrical
heat
cooling
mineral
salt
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Expired - Lifetime
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US358650A
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English (en)
Inventor
Venable Emerson
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CBS Corp
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Westinghouse Electric and Manufacturing Co
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Publication date
Application filed by Westinghouse Electric and Manufacturing Co filed Critical Westinghouse Electric and Manufacturing Co
Priority to US358650A priority Critical patent/US2354159A/en
Priority to FR882752D priority patent/FR882752A/fr
Application granted granted Critical
Publication of US2354159A publication Critical patent/US2354159A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F27/00—Details of transformers or inductances, in general
    • H01F27/08—Cooling; Ventilating
    • H01F27/22—Cooling by heat conduction through solid or powdered fillings

Definitions

  • This invention relates to electrical apparatus, and more particularly, to the cooling of electrical apparatus.
  • cooling of stationary or non-moving electrical apparatus such as the transformers above-mentioned, was accomplished by the use of some fluid such as a liquid or gaseous heat transfer medium.
  • some fluid such as a liquid or gaseous heat transfer medium.
  • the greater proportion of installations employ petroleum oils as the heat dissipating medium.
  • Halogenated hydrocarbons have also been put into transformers in some instances.
  • petroleum and related hydrocarbons have a heat conductivity of the order of 0.00035 calorie per second per square centimeter per centimeter thickness per degree centigrade, which is about 1smooth of the heat conductivity of a metal such as copper, little or no reliance can be placed upon the dissipation of the transformer heat by thermal conduction.
  • Petroleum oil is exceedingly inflammable, and its use in transformers in densely populated areas and certainpotentially dangerous localities is greatly restricted or not permitted. Therefore, transformers operating with air or gas cooling are employed in such critical places. An even greater emphasis must be placed on the provision of appropriate cooling passages for air than is required for oil. The same disadvantages in apparatus construction and electrical efliciency appear with air or gas cooling just as they do with the liquid cooling construction.
  • both oil and air cooled transformers may be subject to unsatisfactory performance or failure due to deteriorating phe nomena.
  • Oil is subject to break down under arcing conditions with the formation of carbonaceous deposits, sludges and inflammable or explosive gases. results in a chemical breakdown of the oil and great care is required to prevent this occurring.
  • oil does have good electrical insulating properties and is preferable on this account to air as a cooling medium.
  • the heat transfer dielectric mineral extends in a homogeneous mass to the wall of the casing enclosing the electrical elements and contacts the casing wall closely. Therefore, a very good overall thermal 'conductivity will be had between the electrical element being cooled and the exterior casing.
  • the construction of the apparatus will not be influenced by the necessity to obtain suitable passages for conventional flow of fluid through the electrical elements, but instead the The contact of oxygen with oil primary emphasis may be placed on an economical construction of apparatus ior a given capacity, and to achieve good electrical efilciency in operation.
  • inorganic salts or minerals have a thermal conductivity which is from 50 t0 80 times greater than that of petroleum. These minerals likewise have an exceedingly high electrical insulating value. Ordinarily, materials which have high thermal conductivity likewise exhibit good electrical conductivity. However, a few crystalline minerals or salts are exceptions to this general rule. Among these minerals are fluorite (CaFz) halite (NaCl) sylvite (KCl), villiaumite (NaF), and potassium fluoride (BT). These minerals have thermal conductivities of 0.026, 0.0166, 0.0166, 0.025 and 0.016, respectively, in calories per second per square centimeter per centimeter thickness per degree centigrade.
  • This invention is predicated upon casting the above type of minerals or salts in a fused state around the electrical elements to provide for good heat transfer. While the fusion temperature of fiuorite alone is considerably above that of the melting point of the good conducting metals, such as copper, it is possible to employ a mixture oi iluorite with other salts, the mixture having a much lower melting point, for this purpose. Both halite and sylvite may be employed as pure salts, since their fusion temperature is below that of the melting point o! electrical members or elements ordinarily employed. However, the eutectic of halite and sylvite, or other mixtures thereof, having lower melting points as compared to the melting temperature of the single salts, will be preferable for many reasons.
  • the fusion temis 790 C A mixture of 50% halite and 50% sylvite has a melting point of 660 C. Owing to the relatively greater cost of sylvite as compared to halite, a 70% halite-30% sylvite mixture having a melting temperature of 697 C. may be a more economical mixture, without much increase in temperature required to produce fusion. Various mixtures of any two or all of these salts may be prepared in order to obtain a wide range of selected melting points. The electrical and thermal conductivities of the salts will remain satisfactory no matter in what proportions the mixtures of the minerals are combined.
  • the cast mineral body will effect a permanent and rigid spacing of the several electrical members both from each other and the enclosing casing. Vibration during operation of ie apparatus will be damped and greatly reduced. Short-circuiting or grounding will be obviated. Thus, a much more satisfactory electrical construction will be available to the electrical industry.
  • the inorganic filling should have a fusion temperature below that at which the electrical elements deteriorate or fail.
  • a mineral fusing above the melting point oi copper, for example, would be unsatisfactory for casting purposes in connection with conductor elements of this metal.
  • a'high melting temperature mineral, such as quartz, would not be desirable in most instances.
  • an additional requirement of the inorganic filling material is that the fused filling must recrystallze on solidifying.
  • An amorphous fusion product generally exhibits greatly decreased heat conductiv'ty.
  • quartz crystals have some ten times as great thermal conductivity as compared to amorphous fused quartz.
  • a somewhat similar hcat conductivity ratio exists with other minerals in the crystalline the amorphous state. Ii the solidified mineral recrystallizes on cooling :from ⁇ the melt, it will retain the high conductivity of the natural crystal.
  • I0 is a transformer consisting of a bottom plate I2, side plate il and top plate I6 welded into a substantially hermetically sealed unit by welding as at I8.
  • An aperture in the top plate I6 sealed by a closure member 20 is provided for the introduction of the molten solid dielectric cooling material. It is particularly desired to provide 'a hermetically sealed construction in order to prevent the entry of moisture and other deteriorating materials into the interior thereof.
  • the operative electrical elements or i members consist of a laminated core 30 of magnetic material and electrical coils 32 placed thereabout with the view to obtaining the best construction and electrical efficiency.
  • the coils 32 are mounted upon insulating sleeves 36 about the legs of the core 30.
  • the coils 32 carry relatively thin insulation 34. There is no particular need to have any heavy insulation about the coils 32, but simply a thin layer in order that the thermal conductivity be a maximum.
  • the contents of a crucible or other receptacle containing the molten salt or eutectic or mixture may be poured in through the opening at 20. It may be desirable to preheat the entire transformer assembly to a temperature approaching that of the molten salt in order to provide for good and homogeneous filling of the casing.
  • cooling from the bottom plate l2 will provide for a regular crystalline solidification of the molten salt beginning at that point.
  • a slow cooling will provide for a dense and uniform crystalline mass 40 of salt filling all the interstices between the coils, and closely adhering to the faces of the electrical elements and to the core 30.
  • the salt will adhere to or closely contact the side H and bottom I2 of the transformer which will facilitate the transfer of heat in the completed apparatus. A slight shrinkage cavity 42 will be evident after solidification of the salt.
  • a shrink head may be applied above theside u of the casing before the top plate I6 has been attached thereto and the molten salt poured to a level above that of the side il. After the salt has solidified, the portion extending above the sides Il may be chipped off or sawed oiI flush. The cover IB is then sealed to the casing.
  • the mineral filling is in a good heat transfer relation to the electrical members after solidification.
  • the recrystallized mineral possesses high thermal conductivity to dissipate the heat with a low thermal gradient between heated members and the casingY
  • the electrical conductors 26 may be made available for connecting with the bushings 22 and 24 by attaching a removable protecting plug or block thereto prior to the casting of the salt. Upon cutting or removal of the surplus salt, the blocks or plugs may be removed and conductors 28 will be exposed.
  • the transformer construction as disclosed in the drawing is much more satisfactory for cooling electrical elements with Vrespect; to a lower thermal gradient than is air cooling.
  • the possibility of the alternate expansion and contraction of the electrical elements as they are energized and deenergized may result in some fissuring or cracking of the cast block of crystalline salt or mineral.
  • an insulating liquid such as a halogenated cyclic hydrocarbon, which is relatively non-inflammable and explosion-proof
  • a viscous material such as an asphaltic compound, may be placed in the shrink cavity. The halogenated liquid material or compound will enter the fissures or cracks and provide for good thermal conductivity between the separated faces of the salt.
  • the halogenated hydrocarbon or asphaltic compound will not be suitable for operation at extremely high temperatures at which the mineral alone would be satisfactory.
  • the minerai is so inexpensive as compared to the liquid halogenated dielectric that a considerable saving may be effected as compared to an all liquid filling by employing a small proportion of liquid dielectric with a maior proportion of salt.
  • the casing Il of the transformer may be provided with an expansion joint so that the salt may be cast within the casing when the casing has been mechanically expanded, and after the salt solidifies the casing upon release and contracting will maintain a continuous, close contact about the body of solid material.
  • Electrical apparatus comprising, in combination, an electrical member subject to heating when in operation, and a heat conducting dielectric body surrounding and embedding the electrical member to provide for spacing the member, and for dissipating the heat, the heat conducting dielectric body composed essentially of a substantially homogeneous crystalline mineral solid cast about the member while in a molten state, the mineral solid selected from the group consisting of sodium chloride, potassium chloride, calcium fluoride, sodium fluoride and potassium fluoride, and providing for a good transfer of heat from the embedded electrical member to the mineral solid and a rapid conduction of the heat to the exterior of the body in order to maintain predetermined temperatures in the electrical member, the cast mineral being so disposed about the electrical member that it constitutes the major electrical insulation therefor.
  • Electrical apparatus comprising, in combination, an electrical member subject to heating when in operation, a sealed casing enclosing and protecting the electrical member and a solid heat conducting dielectric body filling the casing and embedding the electrical member to provide for electrically insulating the member, the solid heat conducting body composed essentially of a solid inorganic substantially homogeneous material having a thermal conductivity of 0.01 calorie or higher per second per degree centigrade per eter thickness per square centimeter, the inorganic material selected from the group consisting of sodium chloride, potassium chloride, sodium iuoride, potassium fluoride and calcium fluoride, cast about the electrical member while in the molten state and solidified to a crystallice mass and substantially conforming to the casing, the whole being associated to provide for D, good transfer of heat from the embedded elecicel member to the solid body, a good conduc- 'cn of the heat to the exterior of the body and transfer of the heat from the body to the seing in order to provide for a low thermal radient

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Transformer Cooling (AREA)
US358650A 1940-09-27 1940-09-27 Cooling electrical apparatus Expired - Lifetime US2354159A (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
US358650A US2354159A (en) 1940-09-27 1940-09-27 Cooling electrical apparatus
FR882752D FR882752A (fr) 1940-09-27 1941-09-18 Dispositif de réfrigération pour appareils électriques

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US358650A US2354159A (en) 1940-09-27 1940-09-27 Cooling electrical apparatus

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US2354159A true US2354159A (en) 1944-07-18

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FR (1) FR882752A (fr)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2805275A (en) * 1950-07-13 1957-09-03 Philips Corp Shrouded electro-magnetic apparatus
US2992405A (en) * 1957-03-26 1961-07-11 Raytheon Co Insulating and cooling devices
US3151210A (en) * 1960-10-12 1964-09-29 Burroughs Corp Package for electronic apparatus
US3428928A (en) * 1966-11-18 1969-02-18 Ovitron Corp Transformer including boron nitride insulation
US3467929A (en) * 1968-09-18 1969-09-16 Gen Electric Dry type transformer and improved enclosure assembly therefor

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2805275A (en) * 1950-07-13 1957-09-03 Philips Corp Shrouded electro-magnetic apparatus
US2992405A (en) * 1957-03-26 1961-07-11 Raytheon Co Insulating and cooling devices
US3151210A (en) * 1960-10-12 1964-09-29 Burroughs Corp Package for electronic apparatus
US3428928A (en) * 1966-11-18 1969-02-18 Ovitron Corp Transformer including boron nitride insulation
US3467929A (en) * 1968-09-18 1969-09-16 Gen Electric Dry type transformer and improved enclosure assembly therefor

Also Published As

Publication number Publication date
FR882752A (fr) 1943-06-15

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