What is Dry Type Transformer? (Cast Resin Dry Type Transformer)
A dry type transformer, also known as a cast resin dry type transformer, is one of the most preferred transformer types today, especially in crowded indoor environments where safety is critical. Unlike oil-immersed transformers, dry type transformers do not contain any mineral oil. They are cooled by air and insulated with epoxy cast resin, significantly reducing fire and explosion risks.
Dry type transformers are widely used in hospitals, schools, shopping malls, metro stations, data centers, and high-rise buildings. Their eco-friendly design and low maintenance requirements make them a long-term smart choice.
Dry Type Transformer vs Oil Type Transformer (Dry and Oil Type Transformer)
Transformers are generally produced in two main types: oil type and dry type.
Oil type transformers use insulating oil, which carries a risk of fire and explosion. Dry type transformers have no oil, making them much safer against fire and explosion hazards. Although they are more expensive to manufacture, they are strongly preferred in indoor applications where human safety is a priority.
Dry type power transformers are ideal for enclosed spaces such as hospitals, schools, theaters, shopping centers, hotels, and office buildings.
Advantages of Dry Type Transformer
- No risk of fire or explosion (self-extinguishing and flame-retardant properties)
- Environmentally friendly (no oil leakage or pollution risk)
- Low maintenance requirements
- High safety for indoor installations
- Suitable for sensitive and populated areas
Dry Type Transformer Sizes and Capacities
Dry type transformers typically start from 250 kVA. They can be manufactured up to 8 MVA depending on the application. 1600 kVA and 2500 kVA dry type transformers are among the most commonly preferred capacities.
High voltage windings are cast under vacuum with epoxy resin, while low voltage windings are either cast or use prepreg insulation technology. The windings are exposed to the atmosphere, which provides advantages in maintenance and fire safety.
Cooling System of Dry Type Transformers
Dry type transformers can operate with natural air cooling (AN) or forced air cooling (AF) with fans. Temperature sensors placed in the windings send data to a relay that automatically activates the fans when needed. Fans also allow up to 40% additional power capacity during overload conditions.
Standard protection class is IP00. For outdoor or humid environments, they must be placed in protective enclosures with IP21, IP23, or IP31 ratings.
Operating Temperature and Insulation Classes
Cast resin dry type transformers are usually produced in F class (155°C) or H class (180°C) insulation. They comply with IEC 60076-11 standard and are generally manufactured in E2 – C2 – F1 environmental, climatic, and fire resistance classes.
| Class | Meaning |
|---|---|
| E0 | Transformers can operate in a clean and dry room where pollution is ignored and there is no condensation. |
| E1 | Transformers can operate in an environment with low condensation and pollution. |
| E2 | The transformer may be exposed to both condensation and high pollution. |
| Climatic Class | Meaning |
|---|---|
| C1 | Dry-type transformers cannot be energized below -5 ºC. They can only be transported and stored in environments up to -25 ºC. |
| C2 | Dry-type transformers can be energized, transported, and stored in environments down to -25 ºC. |
| Fire Resistance Class | Meaning |
|---|---|
| F0 | The probability of fire is not at the expected level and there is no condition for limiting the hazard. |
| F1 | The transformer is exposed to the possibility of fire and reducing flammability is mandatory. A fire on the transformer must be extinguished within a specified time period. |
TEDAŞ Specifications for Dry Type Transformers in Turkey
For projects to be handed over to TEDAŞ, dry type transformers must comply with the technical specification TEDAŞ-MLZ/99-031.B.
ABB dry type transformer, Schneider dry type transformer, and other reputable manufacturers offer high-quality solutions that meet international standards.
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