Epoxy Resin Dry Type Transformers

Another revolution in the field of electrical engineering is the epoxy resin dry type of transformers. Transformer is a device that transfers power at one voltage level to the power at another voltage level. In the conventional oil immersed transformers, the oil has to be handled with great care to avoid any accidents. Moreover the anti short circuit capacity is low. This leads to greater maintenance cost. Secondly faults due to wet insulation, transformer oil degradation, internal short circuits and oil leakage are common. These necessitates lead to the use of Dry type of transformers.



The epoxy resin has a property of retarding the flame. It is also self extinguishing, safe and clean material. It can be operated reliably for more than 40 years and has a high level of thermal insulation which makes it superior to the conventional type of transformers.

Following are some of the characteristics of dry type transformers:

1.    Both the high and low voltage windings( foil wound) are made up of copper.

2.    These windings are enclosed in the epoxy resin casting.

3.    This also increases resistance of the winding to lightning.

4.    The insulation being very thin( 1-3mm) the problem of insulation cracking is taken care of.

5.    These transformers are small and light weight.

6.    A temperature sensor such as PT100 can be installed in the low voltage winding which gives out the information about the temperature  to the tripping circuit.

7.    Embodies forced air cooling which increases the rated capacity by 40 to 50%.

8.    The core is made up of cold rolled silicon steel which limits the no load current i.e reduces the no load losses.

9.    This also makes the performance of the transformer noise less.

10. These transformers have typically H and F class insulation and can sustain temperatures between 155 to 180 degree Celsius.

11. It has nice appearance which maintains the aesthetic sense of the installation, maintenance free and low cost product.

Again to mention specifically, in reference to my project the first of its kind was installed in Nagpur at Batukbhai jewelers. It had the following specifications:

1.    kVA rating: 250, delta-star type.

2.    Voltage: 11kV/415 V

3.    Frequency: 50Hz

4.    Insulation: F class, epoxy resin dry type.

5.    Winding: double wound copper.

6.    Tapings: 5 taps from +5% to -5% in 5 equal steps of 2.5%.

7.    Cooling: air natural.

This transformer is installed for a load capacity of 200 Watts and a maximum demand of 140 kVA.

The use of these types of transformers is now increasing day by day due to the above-mentioned reasons.