Natural air cooling is generally restricted for transformer upto

Natural air cooling is generally restricted for transformer upto

Right Answer is:

1.5 MVA

SOLUTION

Air natural cooling method:

  • The natural air cooling method is also known as the self-cooled method.
  • The heat produced in the transformer due to losses dissipated by conduction, convection, and radiation.
  •  In natural cooling, the coolant circulating inside the transformer transfers the entire heat to the tank walls from where it is dissipated to the surroundings, and transformers gets cooled by natural air circulating surrounding the tank walls.
  • It is used for small voltage transformers.
  • Due to the available insulating materials like glass and silicon resins nowadays, the method can be used for the transformers upto ratings 1.5 MVA.
  • Beyond that level, natural air cooling is not very effective and the transformer can be heated upto a dangerous level which can cause serious damage to the transformer.

Note:- 

  • In air blast or air forced the heat generated is cooled by the forced air circulation. This method is used for transformer rating up to 15 MVA.
  • Oil natural and air natural method is used for transformer rating up to 30 MVA.
  • Oil natural and air forced method of cooling can be used up to 60 MVA.
  • For transformer having rating more than 60 MVA oil forced air forced, oil natural water forced and oil forced water forced methods of cooling is used.
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