Unlike liquid fill transformers that require oil or liquid to cool, dry type transformers use only high temperature insulation systems that are environmentally safe. Dry type transformers are static solid state devices with no moving parts, which require minimum maintenance and provide a long reliable trouble-free life. Because they are completely hazard-free, these transformers can be easily installed in hospitals, schools, factories, chemical plants and buildings where fire safety is a great concern. They can be easily installed indoors as well as outdoors only confirming that there is enough ventilation. However, one drawback with these transformers is that they are easily affected by dirt, dust, moisture and corrosion because the windings are exposed to air. Therefore, these transformers need to be periodically cleaned to prevent dust and other contaminants to build up over time.
Types of Dry Type Transformers
There are various construction methods involved for manufacturing different types of dry type transformers. And, each of these different types is well-suited for different environments and applications.
Open Wound Transformers
The conductor coils are pre-heated and then heated, dipping them in varnish at an elevated temperature. These coils are then baked to cure the varnish. This is called the dip-and-bake method.
Vacuum Pressure Impregnated (VPI) Transformers
VPI transformers are constructed with high-temperature insulation and are comprised of high-temperature materials coated with high-temperature, moisture-resistant and polyester sealants using a vacuum pressure impregnation process.
Vacuum Pressure Encapsulated (VPE) Transformers
These are similar to VPI transformers, only that the polyester sealant is replaced by resin made of silicone. The manufacture of these transformers involves several dip processes, followed by curing the coating in an oven. Also, the resin coating in these transformers is as much as four times that of polyester in VPI transformers. VPE transformers are highly resistant to humid and caustic environments and the effects of salt water.
Cast Coil Resin Transformers
The conductor coils are solidly cast in resin under vacuum in a mould with even distribution and high level of precision. These transformers are reliable and can be exposed to extreme conditions. They require minimum maintenance and can withstand high short circuits. This is the reason these cast coil resin transformers are now being used where earlier only liquid-filled units were available for harsh environments. These transformers today are highly used in tunnels, ships, cranes, nuclear plants and mining industries.
Dry type transformers have a wide range of benefits. Firstly, they are light-weight and require the least amount of maintenance, except the fact that they need to be periodically cleaned. They are very efficient and have a silent operation. They also require the most reduced installation costs. Moreover, they have no fire or hazard risk.
Whatever your purpose, you can get all kinds of transformers including toroidal, medical isolation, power transformers, audio output transformers, three phase transformers, E&I transformers, audio line matching, SMPS and UI, at Miracle Electronics, who is a leading transformer manufacturer in India with all its transformers being RoHS Compliant, Reach Compliant, and available with CE and UL marks with request.