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Methods Of Cooling Of Rotating Elec...Methods Of Cooling Of Rotating Elec... 13303 viewsCooling of power transformer Cooling ofpower transformer 1366 viewsRadial vs Axial ventilation Radial vs Axialventilation 2486 viewsGenerator cooling and sealing system 2Generator cooling and sealing system 2 9360 viewsElectrical machine design (III-EEE) Electricalmachine design (III-EEE) 10786 viewsTransformers Transformers 1154 viewsPower System Operation and Control PowerSystem Operation and Control 4892 viewsCooling system 2 Cooling system 2 296 viewsSeminar report on axial field elect... Seminarreport on axial field elect... 1070 viewsAcelectricalgeneratorsasope 1204080...Acelectricalgeneratorsasope 1204080... 850 viewsCooling system Cooling system 3085 viewsCooling system Cooling system 1161 views
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Methods Of Cooling Of Electrical MachinesPresentation Transcript
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Methods Of Cooling Of Electrical Machines
Methods Of Cooling Of Electrical Machinesby Rahuldey1991on May 11, 2012
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Ahmed Hamdan , مشرف تیم at الشركة السودانیة لتوزیع الكھرباء
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1. What is cooling? Process by which heat resulting from losses occurring in a machine is given up to aprimary coolant by increasing its temperature. Heated primary coolant may be replaced by a newcoolant at lower temperature or may be cooled by a secondary coolant in some form of heat exchanger.
2. Why is cooling needed? Energy transfer and energy conversion in electrical machines manifestlosses. These losses appear as heat and increase temperature of the machine beyond its optimumlevel. Heat is dissipated to surroundings by conduction and convection assisted by radiation from outersurfaces.
3. COOLANTS AND HEAT EXCHANGERSA. Primary Coolant : It has lower temperature thanmachine part. Example: WaterB. Secondary Coolant : It has Lower temperature than primary coolant.Example: Ethylene Glycol, Propylene Glycol, Calcium Chloride, Sodium Chloride.C. Heat Exchanger :Component that keeps two coolants separate but allows transfer of heat energy between them. Example:They are widely used in space heating, refrigeration, air conditioning, power plants, chemical plants,petrochemical plants.
4. Methods of cooling Size of a machine of a given duty depends on heat losses in its various parts.Small machines (Fractional H.P.) cooled by natural means. Modern machines require cooling.Cooling by Air stream -> Ventilation
5. COOLING SYSTEM CLASSIFICATION Based on origin of Based on manner of cooling:cooling:• Natural Cooling • Open Circuit Ventilation• Self Cooling • Surface Ventilation• SeparateCooling • Closed Circuit Ventilation • Liquid Cooling
6. TYPES OF VENTILATION INDUCED FORCED Fan -> Decrease in air Fan -> Sucks airfrom pressure inside machine - atmosphere-> Forces it > Air sucked in -> Pushed into machine -> Airout by fan pushed out Small, medium machines Temperature of cooling air rises due to heat loss More amount of air required
7. RADIAL VENTILATION Most common, Up to 20kW rating Large machines -> Large corelengths -> Core subdivided to provide radial ventilating ducts Advantages: Minimum energy loss forventilation, almost uniform temperature rise in axial direction Disadvantages: Makes machine lengthlarger, cooling might be unstable with amount of cooling air flowing
8. AXIAL VENTIALTION Used in induction machines (medium output, high speed machines) Solidrotor -> Restricts radial ventilation Holes punched where heat loss is more Disadvantages: Non-uniform heat transfer, increased iron loss (Ducts in slots of rotor reduce amount of iron -> Including fluxdensity in core -> Increase in iron loss
9. AXIAL-RADIAL VENTILATION For large motors, small turbo-alternators Axial system -> Largeiron loss -> So mixed system is used Rotor mounted fan forces out the air As a rule, induction motorshaving radial ducts in stator and rotor use forced self ventilation
10. COOLING OF TOTALLY ENCLOSED MACHINE Totally enclosed machines -> Heavy,expensive, Hence uneconomical Air -> Impurities -> Destroy insulation Natural cooling -> Ineffective-> Rating reduces Cooled By : Self ventilated frame, Ventilated radiator machines
11. VENTILATED FRAME MACHINES Self ventilated frame, fan enclosed on shaft outside workingpart of machine Fan enclosed by cover to secure direction of air flow for machine rating < 25kW Forrating > 25kW,internal fan (Primary coolant) + External fan (Secondary coolant) Internal fan -> Insidemachine, avoids temperature gradient across air gap
12. VENTIALTED RADIATOR MACHINES Internal fan circulates air inside machine External fan-> Sucks hot air from inside -> Pushes it back to radiators (Heat exchanger) on frame of machineTotally enclosed machine up to 5 MW At higher ratings, air may be cooled by water if convenient
13. COOLING CIRCUIT OPEN CIRCUIT CLOSED CIRCUIT VENTIALTION:VENTILATION: Cool air drawn in, forced Same volume of air out after passing over passesthrough a closed heated machine parts circuit -> Path has fans, Filters required to clean coolers, dryingagents -> air, driers to remove Hot air from outlet is moisture cooled -> Cool air enters Unsuitable forlarge through the inlets machines
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Loss of excitation
14. COOLING OF TURBO-ALTERNATORS Closed circuit ventilation Long core length, smalldiameter Methods : Air cooled (One side axial, two side axial, multiple inlet system) Hydrogencooled Direct cooled
15. COOLING OFTRANSFORMERS Different Cooling Methods Air Cooling Cooling For Oil For DryType Oil Immersed Transformer Immersed Water Transformer Cooling Air Forced type Oil Natural AirNatural Type (O.N.A.N.) Oil Forced Water (A.F.) Forced (O.F.W.F.) Oil Natural Air Forced Type(O.N.A.F.) Air natural Type Oil Natural Water (A.N.) Forced (O.N.W.F.) Oil Forced Air Natural Type(O.F.A.N.) Oil Forced Air Forced Type (O.F.A.F.)
16. AIR COOLED TURBO-ALTERNATORS For small units used as auxiliaries in large powerstations 1 side axial ventilation : Up to 3MW Air supply by propeller fan -> Air enters at an end,leaves by the other In long machines, temperature rise is high along the length
17. AIR COOLED TURBO-ALTERNATORS 2 Sided Axial Ventilation : Air forced from bothsides, both windings have same temperature rise Used for machine rating up to 12MW Multiple inletsystem : Larger machines Outer stator -> Many chambers -> Alternate inlets and outlets ->Up to rating60MW
18. HYDROGEN COOLING SYSTEM Hydrogen (4-76%)+Air -> Explosive mixture Frame strongenough, all joints gas tight Hydrogen above atmospheric pressure, so leakage is from machine toatmosphere Gas pressure maintained Explosive mix avoided Purity of hydrogen checked bymeasuring its thermal conductivity
19. HYDROGEN COOLING OF TURBO-ALTERNATORS For machines > 50MW,air coolingunsuitable No requisite amount of air, higher fan power Advantages of hydrogen cooling : Increasedefficiency Increase in rating Increase in life span Elimination of fire hazard Smaller size ofcooler Less noise
20. DIRECT COOLING OF TURBO-ALTERNATOR Conventional cooling Direct cooling : Lossesdissipated to medium circulating in windings Called supercharged/Conductor cooled/Inner cooledmachines Advantages : Hydrogen, Water, Oil
21. Coolants in direct cooling Hydrogen: Oil: Stator, rotor made hollow High gradetransformer Hydrogen pumped from oil one end to other Used in US-direct cooling Used formachines with of stator conductors rating up to 300MW Flash point, can be reached in faultconditions, damages insulation
22. Water as coolant in direct cooling Higher rating -> Mechanical limitations for hydrogencooling Water : Superior heat transfer property, Low viscosity, No high pressure heads required forcirculations Advantages :1) Higher load is possible as no temperature difference between conductors andwater2) For rating up to 600MW
23. Conclusion: Cooling is very much essential for modern output machines Makes the output ofmachine stable Increases efficiency, rating of machine Increases longevity of machines, maintainssafe operation Protects the inner parts of machine from thermal damages
24. Thank You! RAHUL DEYDept. ELECTRICALRoll. 09187016017
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