Classifications

• • 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
  • H01F27/20—Cooling by special gases or non-ambient air

Definitions

• the invention relates to a heat exchanger system for transformers or reactors having at least one coil being cooled by gaseous fluids circulating around.
• Transformers or any other electromagnetic apparatuses which dissipate heat during operation have to be cooled by means of a coolant which absorbs the heat resulting from losses and transfers the heat to a heat sink.
• a coolant which absorbs the heat resulting from losses and transfers the heat to a heat sink.
• Such coolant may be liquid fluids, e.g. oil in case of oil transformers, or gaseous fluids, e.g. gas in case of dry-type transformers.
• Dry type transformers have generally been constructed using one of three types of techniques: conventional dry, resin encapsulated, or solid cast.
• the conventional dry method uses some form of vacuum impregnation with a solvent type varnish on a completed assembly consisting of the core and the coils or individual primary and secondary coils.
• a problem with all kind of these transformers is the removal of heat generated by power dissipation in the windings.
• a solid insulation transformer which has a rectangular core covered with a compressible closed-cell foam to eliminate stress during curing of the cast dielectric material surrounding the core and during operation. Heat pipes are placed between the inner coil and the core to extract heat before the temperature builds up.
• an outer multi-layer casing having an incorporated grounded conductive layer is provided to cover the sides of the cast body. The outer casing prevents explosion if dielectric break down and arcing occur, and reduces the danger of electric shock. There are not any further provisions for cooling the transformer.
• a compact dry transformer which is consisting of a magnetic material core provided with a first heat sink consisting of covers having cooling fins on the outer surface thereof.
• the transformer also consists of a coil assembly provided with a second heat sink consisting of enclosures having cooling fins on the outer surface thereof.
• the second heat sink further consists of jackets with heat pipes containing a thermo fluid having low boiling point at vacuum such as water.
• the heat pipes consist of evaporator portions and condenser portions having cooling fins on the outer surface thereof. Due to the heat sinks heat dissipation efficiency of the transformer is improved.
• the whole transformer is disposed within a container as an gas tight enclosure wherein a flow of cooling gas is passing the coils and the gas heated by the heat of the transformer is being directed to pass a gas to water thermosiphon heat exchanger being thermally connected to an external water circulation.
• gaseous fluid as a coolant which dissipates its received heat to an intermediate dielectric fluid.
• the intermediate dielectric fluid which is contained in a closed loop transfers its heat to cooling water outside the transformer to carry away the heat taken from the intermediate dielectric fluid.
• This intermediate fluid is circulating naturally with gravity and evaporating inside the enclosure in a gas evaporator and condensing in a water condenser.
• a gas to water heat exchanger is formed with an arbitrary distance possible between the hot gas and the cold water thanks to the transport of heat with the phase change of the dielectric fluid.
• This is basically a gas to water thermo-siphon.
• the evaporator heat exchanger is arranged within the container and the water condenser is located outside of the container.
• gas ducts can be arranged within the container to direct the gas flow to the coils at their lower end in order to make use of fluid physics where due to gravity cool gas is heavier than heated gas which rises up.
• thermo siphon uses the method of passive heat exchange based on natural convection which circulates liquid in a closed loop without the necessity of a mechanical pump.
• thermosiphon principle can be used whereat an intermediate fluid evaporating at the gas side and condensing at the water side circulates naturally by gravity. Its intended purpose is to simplify the transport of liquid as a heat-carrier and/or heat transfer, by avoiding the cost and complexity of a conventional liquid pump.
• the gas-to-water heat exchanger is made of an extremely good heat transferring material, e.g. aluminium or copper, having a thermal conductivity of a > 150 W/mK .
• an automotive type aluminium heat exchanger which is being used on the gas side inside the container.
• the use of a special alloy for the gas-to-water heat exchanger on its water side is being significantly reduced or not required by use of optimized water i.e. preferably ultrapure water which is usually deionized in order to prevent the respective components from corrosion and the like.
• thermosiphon heat exchanger a cupro-nickel alloy is being provided where according to a further em- bodiment of the invention preferably all surfaces of the system being in contact with water are plated with the cupro-nickel alloy.
• some corrugated plate condensers will rather be made from titanium.
• the heat is transferred to the water by condensation, e.g. by using a plate type heat exchanger. Since the heat capacity on the water and condensing sides are similar this heat exchanger can be very compact, for example compared to a customary heat exchanger according to the state of the art the compact heat exchanger according to the invention has a weight of only about 29 kg for 97 kW of heat duty which results in less need of alloy by about 69%.
• thermosiphon gas to water heat exchanger in a dry transformer in the way in order to transfer the heat from the enclosure wherein the transformer is located and cooled by clean gas, to tap water.
• the condenser can be positioned anywhere, as far as it is above the evaporator which position is needed for the gravity driven natural circulation of the intermediate fluid.
• Fig. 1 a schematic view in side elevation of an arrangement of a dry-type transformer according to the invention.
• Fig. 1 shows a schematic view in side elevation of an arrangement of a transformer 10 according to the invention, where a dry-type transformer 12 is being arranged in a container 14.
• the dry-type transformer 12 comprises three coils 16 which are encompassed by an upper yoke 18 and a lower yoke 20 whereat each coil 16 is attached to a core (being not visible in this drawing) which cores are joint with the yokes 18, 20 in order to close the magnetic circuit.
• Each coil consists of at least two windings which are encased in epoxy resin.
• the dry-type transformer 14 For cooling purposes of the dry-type transformer 14 it is circulated by cooling gas while being encapsulated in the container 14. Additionally this gas flow - shown by a dashed line with large arrows - is being supported by a fan 22 which blows the cooling gas from below against the dry-type transformer 12.
• thermosiphon 24 has a vaporizer 26 and a condenser 28 which is positioned above the vaporizer 26 due to flow-physics and gravity.
• the connection between the vaporizer 26 and the condenser 28 is done on one side by a liquid downcomer 30 and on the other side by the vapor riser 33.
• the thermosiphon 24 consists of the vaporizer 26, the condenser 28, the liquid downcomer 30, and the vapor riser 33 and forms a closed loop accordingly.
• cooling gas passes the coils 16 and receives the heat generated therein and flows to the upper region of the dry-type transformer 12 where the gas flux passes the vaporizer 26 which advantageously can be a customary automotive heat exchanger.
• the enclosure 14 is provided to be gas tight wherein the circulation of gas is supported by the fan 22 takes place.
• the water there is one circuit of flow, an open circuit which is not shown in detail but indicated by two pipe ends 36 and 38 respectively by arrows for outflow and inflow.
• the gas passes through the vaporizer 26 and transfers its affiliated heat to the vaporizer 26 respectively to the intermediate fluid flowing in the closed loop 32.
• the intermediate fluid vaporised by the affiliated heat from the gas flows towards the condenser 28 through the vapor riser 33.
• the condenser 28 which actually is a heat exchanger, too.
• the vaporized intermediate fluid is condensed by dissipating its heat to the fluid of the open circle 34 which is usually water, e.g. tap water.
• Halocarbon compounds or the like are provided which change the physical condition due to thermal impact e.g. from liquid phase to gaseous phase and reverse.

Landscapes

• Engineering & Computer Science (AREA)
• Power Engineering (AREA)
• Heat-Exchange Devices With Radiators And Conduit Assemblies (AREA)
• Treatment Of Fiber Materials (AREA)

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Citations (8)

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• 2009
  • 2009-12-08 PL PL09015185T patent/PL2333798T3/pl unknown
  • 2009-12-08 EP EP09015185.3A patent/EP2333798B1/en not_active Not-in-force
• 2010
  • 2010-11-06 IN IN3300DEN2012 patent/IN2012DN03300A/en unknown
  • 2010-11-06 WO PCT/EP2010/006767 patent/WO2011069585A1/en not_active Ceased
  • 2010-11-06 CN CN201080055798.XA patent/CN102648504B/zh not_active Expired - Fee Related
• 2012
  • 2012-05-24 US US13/479,857 patent/US8922310B2/en not_active Expired - Fee Related

Patent Citations (8)

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