Dry Type Transformers versus Oil Filled Transformers

Before going to the mark difference between Dry Type Transformer and Oil Filled Transformer, it is worth to have some discussion on Dry Type Transformer.

Dry Type Transformer:

Dry Type Transformers find use in locations where the use oil Filled Transformers increases the fire hazard such as shopping malls, Hospitals, residential complexes etc. In dry type transformers air is used as the cooling medium instead of oil.

The insulation used in such type of transformers are designed to withstand higher temperatures. Dry type transformers are more expensive than conventional transformers. Vacuum Pressure Impregnation, Epoxy Resin cast are some of the methods of Insulation adopted in Dry Type Transformer construction.

Comparison between Dry Type and Oil Filled Transformer:

  • Dry Type Transformers use air as the cooling medium. Oil Type Transformers are considered a potential fire and safety hazard for indoor application.
  • It can be located closer to the load unlike Oil Transformers which require special location and civil construction for safety reasons. Locating the Transformers near the loads may lead to savings in cable costs and reduced electrical losses.
  • Oil Type transformers may require periodic sampling of the oil and more exhaustive maintenance procedures.
  • Though Dry Type Transformers are advantageous, they are limited by size and voltage rating. Higher MVA ratings and voltage ratings may require the use of oil Transformers.
  • For outdoor applications, Oil Filled Transformers are cheaper than dry types.

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