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25MVA 3 Phase Power Transformer

The 25 MVA 3-Phase Power Transformer is a robust, oil-immersed unit engineered to serve high-demand industrial loads with precision and reliability. Built to IEEE C57 standards, it steps down 24.5 kV Delta to 14.4 kV Wye, delivering 25 MVA in natural ONAN cooling and up to 30 MVA when its first-stage ONAF fan engages. Its copper windings and Dyn1 connection group provide stable voltage regulation, while a ±2.5 % (5-step) off-circuit tap changer allows fine tuning under varying load conditions. The sealed conservator tank and silica-gel breather maintain oil purity across –20 °C to +45 °C, and porcelain bushings rated to 125 kV BIL (HV) and 95 kV BIL (LV) ensure long-term dielectric integrity. Disassembled for safe transit and reassembled on-site, this transformer combines straightforward installation with proven performance for mission-critical applications.

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Product Accessories

Oil & Winding Temperature Gauges: Four-contact dial indicators for fan control (starts at 55 °C, stops at 45 °C) and high-temp alarm/trip.

Oil Level Indicator: Magnetic sight glass with high/low-level alarm contacts.

Buchholz & Pressure-Vacuum Relays: Twin-float gas/oil detector and vacuum gauge for rapid fault detection.

On-Load Tap Changer Handle: External driver for five-step ±2.5 % voltage adjustment.

Fans & Detachable Radiators: Bolt-on ONAF fans and hot-dip galvanized radiators for enhanced cooling.

Porcelain HV/LV Bushings: Three 4-hole NEMA HV pads; four 4-hole LV pads—bottom entry.

Drain & Sampling Valves: Main tank and ONAF compartment valves for oil testing.

Terminal Control Box: Prewired with CTs, alarms, trips, and analog outputs for SCADA integration.

Lifting Lugs & Packaging Frame: Skid and wooden crating with impact recorders for overseas shipment.

Nameplate & Wiring Diagrams: Stainless steel data plates and detailed interconnection schematics.

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Product Specifications

Rated Power

25 MVA (self-cooled), 30 MVA (fan-cooled)

Primary Voltage

24 500 V (Delta), ±2.5 % tap steps

Secondary Voltage

14 400 V (Wye)

Tap Positions

5 × 2.5 % off-circuit

Vector Group

Dyn1

Frequency

60 Hz

Impedance

8 % at 25 MVA

Temperature Rise

Oil: 65 °C; Winding: 65 °C

BIL Rating (HV/LV)

125 kV / 95 kV

Weight & Dimensions

~84 800 lbs; 4 550×2 109×2 950 mm

Product Applications

Economy is more affordable

Powers high-precision tooling and assembly lines with stable voltage despite variable loads.

Aerospace Manufacturing
Drives compression and pumping units requiring continuous, high-capacity supply.

Petrochemical Facilities
Feeds multiple fast-charging stations with dependable medium-voltage service.

Electric Vehicle (EV) Charging Parks
Integrates into urban grid nodes for reliable distribution and grid-support functions.

Utility Substations

Product Advantages

Dual-Mode Cooling Flexibility

ONAN/ONAF design allows seamless transition from 25 MVA to 30 MVA without hardware changes, optimizing load management.

Precision Voltage Control

A 5-step off-circuit tap changer delivers ±2.5 % adjustments, ensuring downstream equipment operates within tight voltage tolerances.

Transport-Friendly Design

Modular disassembly and impact-monitored packaging simplify overseas shipment and reduce onsite rigging time.

WellDone Power Transformer Plan Drawing

FAQ

What range of transformer products do you offer and which standards do they meet?

We manufacture a diverse array of transformers including Oil-Immersed Distribution Transformers, Dry Type Transformers, Power Transformers, Three Phase Pad Mounted Transformers, Single Phase Pad Mounted Transformers, Substation Transformers, and Pole Mounted Transformers. Our technical team, with nearly 20 years of industry experience, ensures that our designs comply with international standards such as ANSI, IEEE, DOE, CSA, AS, AZS, GOST, IEC, and more. Additionally, many of our products have obtained UL, cUL, and CSA certifications, affirming their safety and performance in global markets.
How do you ensure the quality and reliability of your transformers?

Our transformers are produced under a rigorous quality management system covering every stage from material selection to final testing. Each product comes with a minimum 24-month warranty, ensuring long-term safety and reliability. This commitment to quality has earned the trust of global customers and leading industry players.
What are your production lead times, customization options, and global market reach?

For standard models, our production lead time is typically 10 to 25 days, and we offer flexible OEM/ODM services for customized projects. We also tailor packaging solutions to meet specific customer requirements. Our transformers are exported worldwide—including North America, Europe, South America, Australia, Asia, and Africa—with successful partnerships involving renowned companies. For more details or personalized support, please contact us via email or WhatsApp.