Certificates

A dry type transformer is cooled by normal air ventilation instead of a liquid such as mineral oil or Envirotemp FR3. Most instrument transformers and low-voltage power chargers today are also dry types. Liquid cooling inside sealed tanks and metal enclosures became the standard for AC power distribution transformers due to the higher induction heat losses and exposure to all-weather conditions. Because of improvements in design, materials and manufacturing methods over the past three decades, dry type transformers not only compete with liquid-cooled transformers in the medium voltage range (2.5KV – 34.5 KV) but have significant advantages in many commercial and industrial applications.

Dry-Type Vs. Liquid Cooled (Padmount) Transformers

When designed and built to meet current industry standards, medium-voltage dry type and padmount transformers offer essentially the same levels of power efficiency and BIL for a given KVA rating. The differences in operation depend on the application and the installation environment.

Liquid-cooled padmount transformers are used by utility companies for both medium and higher voltage applications because they are designed for all-weather outdoor installations like substations. They have a long history of providing safe, reliable power, and can be installed in outdoor public spaces (with appropriate enclosures). One of their disadvantages is that, since the mineral oil used as a coolant is flammable, a transformer failure (due to insulation failure, overheating or a lightning strike) can result in an explosion and a fire. Thus, they are not recommended for indoor installations or anywhere a fire could have catastrophic results.

Dry Type transformers are cooled by clean ambient or forced air and contain no liquids. They present a minimal fire hazard and are suitable for indoor installations or anywhere fire hazards must be avoided. Because they are designed and built to run cool and quiet, they are ideal for indoor installations in office buildings, universities, hospitals, and manufacturing clean rooms. They can replace liquid-cooled transformers in many of these settings.