What is a VPI Dry Type Transformer?

A Vacuum Pressure Impregnated (VPI) transformer is an open-wound, dry-type transformer whose core and windings are subjected to cycles of deep vacuum and high pressure while submerged in solventless polyester or silicone resin. This process thoroughly fills microscopic voids, delivering exceptional dielectric strength, superior heat dissipation, and robust protection against moisture, dust, and industrial contaminants.

What are the main advantages of VPI dry type transformers over oil-immersed transformers?

VPI transformers eliminate the risk of flammable oil leaks and catastrophic explosions, making them ideal for indoor environments, high-rise buildings, underground facilities, and data centres. They require minimal maintenance, do not need oil-containment basins or complex fire-deluge systems, and provide higher environmental safety.

How does VPI compare to Cast Resin (CRT) dry type transformers?

VPI units utilize non-encapsulated windings impregnated with Class H (180°C) or Class C (220°C) insulation systems. They are lighter in total weight, exhibit higher resilience against thermal shock and frequent harmonic cycling, offer superior field repairability, and represent a lower initial capital cost compared to thick solid epoxy cast resin transformers.

Which international testing standards do URJA VPI transformers comply with?

URJA VPI transformers are engineered, built, and rigorously tested in compliance with global standards including IEC 60076-11, IEEE C57.12.01, ANSI C57.12, and IS 11171. Each unit undergoes comprehensive routine and type testing including partial discharge verification, temperature rise, and impulse testing.

VPI Dry Type Transformer Manufacturer & Exporter

Industrial Grade Electrical Engineering

Dry Vacuum Pressure Impregnated (VPI) Transformers Manufacturer & Exporter

URJA Techniques (India) Pvt. Ltd. is an internationally accredited transformer manufacturing house specializing in high-reliability Vacuum Pressure Impregnated (VPI) Dry Type Transformers. Managed by veteran technocrats with over two decades of precision design, thermal analysis, and production expertise, our manufacturing operations deliver robust power solutions up to 33 kV voltage classes across India, the Middle East, Africa, and Southeast Asia.

Built under rigorous quality protocols certified to ISO 9001, ISO 14001, and ISO 45001 standards, URJA VPI transformers eliminate flammable liquids, toxic off-gassing, and oil-containment complexities. They are purpose-built for harsh indoor environments, heavy harmonic loads, and critical infrastructure where uninterrupted operation, personal safety, and fire prevention are non-negotiable.

URJA VPI Dry Type Transformer Core and Coil Assembly

VPI Core & Coil Assembly (Class H / C)

VPI Dry Transformer with Ventilated Protective Enclosure

Enclosed Indoor / Industrial Substation Duty

The Advanced Vacuum Pressure Impregnation (VPI) Technology

Standard dip-and-bake methods frequently leave microscopic air pockets inside tightly wound conductor layers. These air voids degrade dielectric integrity and cause accelerated partial-discharge failure under thermal stress. The URJA Advanced VPI Process completely neutralizes this operational hazard through a multi-stage autoclave treatment cycle:

Deep Vacuum Degassing

Windings and core assembly are pre-heated and enclosed in a sealed vacuum chamber to extract all residual moisture, volatile solvents, and microscopic air pockets.

High-Pressure Resin Penetration

High-grade solventless polyester or high-temperature silicone varnish is introduced under deep vacuum, followed by dry nitrogen pressure up to 8 bar to drive resin into the deepest inter-turn layers.

Precision Thermal Polymerization

Assemblies undergo controlled computer-monitored baking in industrial ovens, curing into an impenetrable, void-free, and mechanically homogeneous solid insulation structure.

Key Engineering Advantages for EPCs & Industrial Plants

Exceptional Fire Safety & Non-Explosive: Completely oil-free construction eliminates fire hazard, requiring no water-spray deluge systems, fire-barrier walls, or civil oil retention pits.
Superior Thermal Performance (Class H / C): High-temperature insulation systems rated up to 180°C (Class H) and 220°C (Class C) provide superior overload margins and thermal longevity during peak load periods.
Severe Harmonic Handling (K-Factor Rated): Specifically engineered with low-loss CRGO silicon laminations and optimized transposition to withstand severe non-linear harmonic distortion generated by Variable Frequency Drives (VFDs) and rectifiers.
High Dynamic Short-Circuit Withstand: The monolithic resin bond prevents coil movement, vibration resonance, and mechanical coil fatigue under heavy faults, certified through rigorous testing.
Superior Repairability & Lower Lifecycle Cost: Non-encapsulated construction permits on-site inspection, coil repair, and maintenance that is structurally impossible on solid epoxy cast resin transformers.

Technical Specifications & Design Ratings

Design Parameters	Engineering Specification Range
Rated Power Capacity	100 kVA up to 5000 kVA (Custom Higher Capacities Engineered on Demand)
Voltage Class Rating	Primary: 3.3 kV, 6.6 kV, 11 kV, 22 kV, 33 kV \| Secondary: 415 V, 433 V, 690 V, or custom
Cooling Methodology	AN (Air Natural) / AF (Air Forced with Forced Ventilation Fans for +40% Boost)
Insulation System	Class H (180°C) or Class C (220°C) utilizing Nomex® and solventless resin
Core Construction	High-permeability, cold-rolled grain-oriented (CRGO) silicon steel step-lap mitred core
Winding Conductor	Electrolytic High Conductivity Copper (Cu) or Grade-A Aluminium (Al) strip/foil
Vector Groups	Dyn11, Dyn5, Ynd11, Dd0, or custom configuration specified by project SLD
Enclosure Protection Class	IP00 (Core & Coil for OEM cubicles), IP21, IP23, IP31, IP33, up to IP54 (Air-to-Air Heat Exchanger)
Applicable Standards	IEC 60076-11, IEEE C57.12.01, ANSI C57.12, IS 11171, BS Standards

Global Industrial Applications & Installation Footprint

URJA VPI dry transformers are chosen by project directors and EPC consultants across mission-critical infrastructure where fire containment and supply reliability are vital:

Commercial High-Rises Data Centres & IT Parks Pharmaceutical Production Chemical & Petrochemical Belts Marine Vessels & Offshore Platforms Mining & Heavy Excavation Steel & Rolling Mills Metro Rail & Traction Power Clean Room Substations Renewable Solar & Wind Arrays

Export Capabilities & International Compliance

With transformers installed in harsh climatic conditions ranging from high-ambient desert environments in Saudi Arabia and the UAE to humid tropical corridors across Southeast Asia and Africa, URJA delivers customized packaging, marine-grade seaworthy containerization, and comprehensive vendor documentation packages including third-party test certifications, factory acceptance test (FAT) reports, and installation drawings.

VPI Dry Type Transformer