Strength and Weaknesses of Dry Type Transformers


Electrical appliances are generally incapable of bearing voltage fluctuation. They either get damaged or fused due to this. To tackle the situation, a transformer is needed so that electrical appliances that one is using get the same frequency of voltage or current. In case of Dry type transformers air is used as coolant for which it needs an insulation system for air circulation. The best part about these transformers is that they require very little electrical maintenance with trouble free services for many years.

Dry transformers are often called cast resin transformers as their windings are covered in epoxy resin. These transformers are usually dry and do not need oil as coolant due to which it is easier to install. They are suitable for both indoor and outdoor.

The usage of dry type transformers are mostly seen in places where transformers that use oil as a coolant creates an unsafe working environment.

Here are different types of Dry type electrical transformer that are available

  • VPI dry-type transformers (Vacuum Pressure Impregnated)
  • Cast coil transformer­­
  • Vacuum Pressure Encapsulation (VPE) transformer
  • Open wound transformers


Let’s have a look at the areas of strength in Dry type transformers

  • It provides 100% safety during its use. As it does not require oil as coolant, it is appropriate and safe to use at every setting. It keeps the winding safe from fire.
  • As mentioned before there is no involvement of oil in these transformers as they use air for cooling purposes. It highly reduces cost and labor both.
  • its winding is covered with resin that prevents moisture penetration
  • Chances of transformer exploding are also less with these transformers when compared to others.
  • It’s a nature friendly transformer as it does not use oil, there is no scope of oil leakage and above all it does not pollute the environment.
  • It comes with an easy maintenance facility. The oil free usage means no oil testing and because of its plain and smooth coil surface it does not accumulate much dirt which makes it easy to clean
  • The installation cost of dry transformers is relatively low. It can easily be fixed near the load because there are no constraints in the installation site.
  • It is resistant to cracks
  • It is long lasting and has a compact design
  • It is more sustainable than others
  • it is a vibration proof transformer
  • It has the capability of operating in extreme weather conditions and can bear temperature from -50°C to 50°C.

The list of disadvantages of these transformers is much smaller than its advantages. Have a look at them

  • Undoubtedly its maintenance is easy but it is difficult to repair
  • Their purchasing cost is higher than oil type transformers
  • Coils can pose a threat in case it is not cleaned properly
  • Oil type transformers have a better overload capacity than this
  • It is not a suitable option for indoors as it makes a lot of noise

When you are getting a dry type transformer, you need to consider the following things

  • Its primary and secondary voltages
  • Frequency
  • Power rating

Whether you choose a dry type transformer or an oil type transformer, consider the above mentioned advantages and disadvantages of dry type transformers before making the final decision. It will surely help you in selecting the right one for your need.