The liquid filled transformers would need liquid or oil to cool, whereas the dry type transformers would use only high-temperature insulation systems that have been deemed environmentally safe. The dry type transformers would be static solid state devices having no moving parts. It would need minimum maintenance along with providing a lengthy, durable, and trouble-free life.
The dry type transformer has been deemed completely hazard-free. These transformers could be easily installed in schools, hospitals, factories, chemical plants, and buildings where fire safety has been of great concern. They could be easily installed indoors as well as outdoors. However, they would need adequate ventilation. The only drawback would be these transformers would be easily affected by dust, dirt, moisture, and corrosion, as the windings have been exposed to air. Therefore, these transformers would require periodic cleaning. It would be essential for the prevention of dust and other contaminants building up with the passage of time.
Different types of dry type transformers
There have been several construction methods entailed for manufacturing different kinds of dry type transformers. Moreover, the different kinds of dry-type transformers would be ideally suited for various applications and environments.
- Open wound transformers
The conductor coils would be pre-heated and then heated by dipping them in varnish at high temperature. These coils would then be baked for curing the varnish.
- Vacuum Pressure Impregnated Transformers
These are also called the VPI transformers constructed with high-temperature insulation. These would comprise high-temperature materials coated with moisture-resistant, high-temperature, and polyester sealants that uses a vacuum pressure impregnation process.
- Vacuum Pressure Encapsulated (VPE) Transformers
The VPE transformers have been similar to VPI transformers. The only difference would be the polyester sealant has been replaced with silicone resin. The VPE transformer manufacturer would entail various dip processes. It would be followed by curing of the coating in an oven.
In addition, the resin coating in VPE transformers would be as much as four times that of polyester in the VPI transformers. These would be highly resistant to humid environments along with the effects of salt water.
- Cast coil resin transformers
The conductor coils would be cast in resin under the vacuum in the mold. It would be evenly distributed with a high level of precision. Such transformers have been reliable and exposed to extreme conditions. They need minimum maintenance and could easily withstand short circuits. This has been the major reason why there cast coil resin transformers have been used where previously liquid-filled units have been deemed suitable for relatively harsh environments.