Dry Type Transformers

Open Ventilated Dry Type (OVDT) Vacuum Pressure Impregnated (VPI) Eco Friendly Transformers

KOTSONS was one of the first Indian manufacturer to use the DuPont ReliatraN® branded solution and develop Ventilated Dry Type Transformers in collaboration with E. I. du Pont de Nemours and Company, U.S.A.

KOTSONS Eco Friendly VP transformer coils are vacuum pressure impregnated in high temperature varnish. The process includes complete submersion in varnish under vacuum and pressure and regulated curing using PLC controlled equipment to ensure consistency. The finished coils are effectively protected against moisture, dirt, and most industrial contaminants. A 220°C Class NOMEX® Listed insulation system is used on KOTSONS OVDT VPI transformers regardless of specified temperature rating. This system accommodates a standard temperature rise of 155°C. Optional temperature rises of 90°C and 115°C and fan cooling allow for unsurpassed overload capacity.



Salient Features & Advantages of OVDT VPI Dry Transformers:

1. Excellent mechanical and short-circuit strength due to the VPI Process

2. No danger of fire or explosion. No liquids to leak hence no flammable liquid & no oil pollution

3. Less weight than comparable cast resin units

4. Low total ownership costs and low initial costs

5. Use of NOMEX® UL® Certified Insulation Materials, listed 220°C insulation system, regardless of temperature rating

6. VPI transformers are non-explosive with high resistance to flame and do not require vaults, containment dikes, or expensive fire suppression systems

7. Low Partial Discharge - VPI process ensures void free insulation system

8. Moisture Ingress Resistant & Immune to polluted atmosphere

9. Easy to repair (open coils) due to OVDT Design

10. Eco Friendly, No harm to environment at the end of Life

Temperature Rise / Overload Capacity :

Options & Accessories

• UL listing
• IEEE 344 - Seismic Certification
• NEMA 3R enclosurer
• 90°C or 115°C average temperature rise
• Copper windings
• Provisions for Future Fan Cooling (FFA)
• Electronic temperature monitor
• Increased basic impulse levels
• Loss optimized designs
• Air-filled terminal chambers
• Special paint colors

Standard VPI Range & Features:

• Up to 5000kVA & up to 33kV
• Aluminum / Copper Windings
• With Dry Type On Load Tap Changer
• Step-Lap mitered Core / Amorphous Metal Core
• 220°C insulation system - 155°C average temperature rise
• Vacuum pressure impregnation with high temperature varnish
• Vibration isolation pads between Core, Coil and Enclosure
• Base equipped with Jacking Pads and designed for Rolling or Skidding the Enclosure in any direction
• Suitable for Package Substation installation
• 100% QC Partial Discharge Test

Key Strengths


To provide competitiveness in price with continuous improvement in quality.


Assurance to deliver goods on time, A basic requirement for any transformer company.


Provide optimum productivity through improved working methods for employees.


We ensure involvement & cooperation of our employees via effective communication.

With Expertise spanning almost four decades in transforming power into efficient energy that's safe for users and the environment, Kotsons has emerged as the undisputed leader in providing quality and reliable transformer manufacturing.

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