Generator Cooling System

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Generator Cooling System

Air cooled generator
  • In generator large amount of heat is generated and is not possible to dissipate this heat from natural system.
  • So forced air cooling system is adopted.
  • In this air is forced into the generator due to which large amount of heat is removed.
  • Air is forced circulated inside generator.
  • This air is pick up the heat from conductors of the generators and further air is cooled in a heat exchanger in which cooling water is flowing.
  • In generator small ducts are provided in which air is flowing.
  • The heat dissipation with air cooling system is limited. It is used in small size generator.
  • This system is some limitations like it is not possible to used in a large size of generator.
  • The air should be clean and free from dust & moisture (So instrument air is supplied through a line).
  • There is an optimum rating of the generator beyond which air cooling system is not economical because of air have a limit of heat for heat transfer.
  • In air cooling system is simple and there are no any special arrangement is required.


Hydrogen cooled Generator
  • In hydrogen cooled system hydrogen gas is used as a medium for cooling.
  • Water Cooled Generator
  • As hydrogen cooling is not sufficient to extract heat generated in large turbo alternators of sizes 500 MW or more. For such large machines, the volume of hydrogen gas required may be so large that its use may become uneconomical.
  • In such cases, the direct water cooling is used. In very large turbo-generators, rotors are direct hydrogen cooled and stator winding are direct demineralized water cooled. Water is circulated by an AC motor centrifugal pump. Cartridge filters are used to filter water. These filters are designed to prevent metallic corrosive particles generated in winding and piping from entering into winding hollow conductors.
  • Advantages of Water Cooling Over Hydrogen Cooling
  • Water cooled system is faster and more efficient because the thermal conductivity of water is higher than that of hydrogen.
  • The duct area of water is smaller to allow more space for conductors in the slot.
  • Disadvantages of Water Cooling
  • The water, which is used for cooling should be highly purified so that the conductivity of water does not increase.
  • Water cooling is more expensive than hydrogen cooling.
Generator Cooling Goals 
Minimize drag windage
Keep generator internals clean
Maximize generator output
Minimize electrical, mechanical and corrosion problems
Maintain low dew point for component durability









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