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Doctors Medicines MCQs Q&A

  1. Closed circuit ventilation
  2. Radial ventilation
  3. Multiple inlet system of ventilation
  4. Axial ventilation
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1 Answers

Option 4 : Axial ventilation

Axial flow ventilation system: 

  • In the case of alternator cooling, a large quantity of air is passed through subslots, which are just below the main slots. Such type of cooling is known as axial ventilation. 
  • In this method, air is forced in the axial direction through passages formed by the holes in the stator and rotor.

Radial flow ventilation system: 

  • The cooling air enters the ducts through stator by way of the air gap and passes radially to the back of the stator from where it is removed.

Closed circuit ventilation:

  • In the closed system, clean hot air from the alternator is cooled by a water-cooled heat exchanger and forced through the alternator by fans.
  • The closed-circuit ventilation system is used for better cooling of the synchronous generator.

 

Note:

  • Natural cooling is not adequate to dissipate the great amount of heat produced in the alternators.
  • In the forced air-cooling system, air is forced into the alternator so that a greater quantity of air is passed over the surface and a large amount of heat is removed.
  • Ducts are provided in the stator and the rotor cores and in the field coils of the generators for increasing the surface area which is in contact with the cooling air.
  • Depending upon the direction of the air flow these ducts can be radial or axial.
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