Dry type transformer as its name dry type means it does not require oil or any other liquid to cool the electrical core and coils. The purpose is served by normal air ventilation.
In India, dry type transformer in the range up to 11 kV and capacity 2.5 MVA are manufactured.
Dry type transformer
The popular design in dry type construction are :
- Resin Impregnated
- Cast resin
Resign Impregnated :
- Resign impregnated this is also termed as vacuum pressure impregnated (VIP).
- VIP transformers are constructed with the insulation which sustains high temperatures and exceeds the rating of cellulose.
- Polyesters sealants are applied to the winding of interchanging pressure and vacuum cycles, termed as vacuum pressures impregnators.
- The polyester sealant is high temperature and moisture resistant.
- Then coils are treated in the oven.
- These units propound greater is an resistance to corona.
Cast resign :
- Cast resign in these units coils are enveloped in resign by process of molding.
- The transformer coils are solidly cast, in resign under a vacuum in a mold.
- The manufacturing process is such that winding is locked in strong epoxy resign.
- Epoxy resin with a high dielectric strength which makes the transformer sustain extreme operating conditions.
- In the actual environments like chemical process plants, constructional material factories outdoor installations coil needs additional strength and protection. Cost resin type is suitable for this.
- In such environments salts, moisture caustic gases and metal particles ruin other types of dry transformers.
- Electrical surges and overloads of repeated short duration are handled by this type.