Safe and reliable, intelligent power supply, three phase transformer protects your power needs!
01 General
1.1 Project Description
The 2500 kVA three-phase pad-mounted transformer supplied to the U.S. market was built with DOE efficiency rules in mind and shaped around long-term environmental durability, using a stainless steel tank, an intelligent protection system, and a low-loss structure that naturally reduces energy waste. By lowering losses, stretching service life, and keeping maintenance needs modest, the transformer delivers steadier and cleaner power, quietly reducing its footprint while supporting a more sustainable distribution network.
1.2 Technical Specification
2500 kVA pad mounted transformer specifications type and data sheet
| Delivered to | America |
| Year | 2025 |
| Type | Pad mounted transformer |
| Standard | IEEE StdC57.12.34-2022 |
| Rated Power | 2500 kVA |
| Frequency | 60HZ |
| Phase | 3 |
| Feed | Loop |
| Front | Dead |
| Cooling Type | ONAN |
| Primary Voltage | 12.47GrdY/7.2 kV |
| Secondary Voltage | 0.48Y/0.277 kV |
| Winding Material | Aluminum |
| Tank Material | Stainless Steel |
| Compartment Material | Stainless Steel |
| Angular displacement | YNyn0 |
| Impedance | 5.75% |
| Tap Changer | NLTC |
| Tapping Range | ±2*2.5% |
| No Load Loss | 2.4 kW |
| On Load Loss | 15.79 kW |
| Accessories | Standard Configuration |
1.3 Drawings
2500 kVA pad mounted transformer diagram drawing and size.
1.4 Energy Efficiency Advantages
DOE-Compliant Low-Loss Design The transformer meets DOE efficiency requirements, which means its no-load loss of 2.4 kW and load loss of 15.79 kW stay consistently low. Although these numbers seem small in isolation, they accumulate into long-term energy savings that steadily reduce operating costs and environmental burden over the years of continuous work.
Optimized Magnetic Circuit – Five-Column Core The five-column core creates a smoother magnetic path, lowering flux density, suppressing harmonics, and reducing the background hum that transformers typically produce. It also naturally cuts down on reactive losses, allowing the entire system to run more efficiently and with a quiet stability that feels intentional rather than accidental. ONAN Natural Cooling Its ONAN cooling system depends entirely on natural air movement-no fans, no motors, nothing extra drawing power-so the transformer cools itself with almost effortless simplicity, using ambient airflow to regulate temperature while avoiding auxiliary energy consumption, reducing noise, and lowering long-term maintenance demands. |  |
02 Manufacturing
2.1 Core
 | Utilizing the three-phase five-column core ensures uniform magnetic flux distribution for each phase, achieving excellent magnetic coupling. This design not only reduces stray magnetic flux but also optimizes the energy conversion efficiency of the transformer, thereby enhancing overall performance. The five-column design effectively suppresses harmonics, reduces noise, and minimizes thermal losses, ensuring reliability and safety under various load conditions. Additionally, the Y-Y connection with the three-phase five-column core supports neutral point grounding, which improves handling of unbalanced loads and short-circuit faults. |
2.2 Winding
| Low-voltage foil winding uses thin aluminum foil, providing excellent heat dissipation and low conductor loss, which reduces the skin effect and improves efficiency under low voltage. High-voltage wire winding employs high-voltage aluminum wire with good insulation properties, ensuring the ability to withstand high voltage impulses and maintaining safe and stable operation. |  |
2.3 Tank
 | The oil tank of the three-phase pad-mounted transformer is made of stainless steel, and its manufacturing process includes several key steps. First, high-corrosion-resistant stainless steel is selected to ensure the oil tank can be used for an extended period in humid and harsh environments. Next, advanced welding techniques such as TIG welding or MIG welding are used to assemble the oil tank, ensuring the strength and seal of the welds to prevent oil leakage. After welding, surface treatment is performed, including sandblasting and application of a protective paint layer to prevent oxidation and corrosion. Then, pressure testing and leak testing are conducted to ensure the oil tank can withstand normal operating pressure without leaks. Finally, the oil tank is assembled with other components of the transformer, and necessary monitoring attachments are installed to ensure the oil tank’s safety and efficiency under various working conditions. |
2.4 Final Assembly
| 1. Hoisting the Active Part into the Oil Tank: Hoist the active part of the transformer (core and windings) and place it into the oil tank. 2. Electrical Connections: Connect the windings to the bushings, ensuring secure and well-insulated connections. 3. Accessory Installation: Install accessories, including three gauges and one valve, along with other related components. 4. Sealing the Oil Tank: Seal the oil tank and fill it with transformer oil for insulation and cooling. |  |
03 Environmental Feature
3.1 Stainless Steel Tank - Long Life, Less Waste
| The stainless steel tank resists corrosion, endures harsh outdoor conditions, extends service life beyond standard steel, reduces replacements and waste, and remains highly recyclable. |
3.2 Internal Fault Detector (IFD)
| The IFD monitors internal changes and alerts early, preventing leaks, equipment damage, and environmental risks before they escalate. |  |
3.3 Aluminum Windings - Lighter Carbon Footprint
| Aluminum windings use less energy to produce than copper, dissipate heat efficiently, reduce carbon footprint, and support long-term transformer efficiency. |
04 Testing
| No. | Test Item | Unit | Acceptance Values | Measured Values | Conclusion |
| 1 | Resistance Measurements | % | Maximum resistance unbalance rate | 2.43 | Pass |
| 2 | Ratio Tests | % | The deviation of voltage ratio on the principal tapping: ≤0.5% | 0.03-0.05 | Pass |
| 3 | phase-relation tests | / | YNyn0 | YNyn0 | Pass |
| 4 | No-load losses and excitation current | / | I0 :: provide measured value | 0.26% | Pass |
| P0: provide measured value(20℃) | 2.302kW | ||||
| the tolerance for no load loss is +10% | / | ||||
| 5 | Load losses impedance voltage and efficiency | / | t:85℃ the tolerance for impedance is ±7.5% the tolerance for total load loss is +6% | / | Pass |
| Z%: measured value | 5.79% | ||||
| Pk: measured value | 16.196kW | ||||
| Pt: measured value | 18.498kW | ||||
| Efficiency not less than 99.53% | 99.53% | ||||
| 6 | Applied Voltage Test | kV | LV: 10kV 60s | No collapse of the test voltage occurs | Pass |
| 7 | Induced Voltage Withstand Test | kV | Applied voltage (KV): 2 Ur | No collapse of the test voltage occurs | Pass |
| Duration(s):60 | |||||
| Frequency (HZ): 120 | |||||
| 8 | Leakage Test | kPa | Applied pressure：20kPA Duration：12h | No leakage and no Damage | Pass
|
| 9 | Insulation Resistance Measurement | GΩ | HV-LV to Ground | 21.6 | / |
| LV-HV to Ground | 19.4 | ||||
| HV&LV to Ground | 20.9 | ||||
| 10 | Oil Test | / | Dielectric Strength; | 58.1 kv | Pass |
| Moisture Content | 9.4 mg/kg | ||||
| Dissipation Factor | 0.00211% | ||||
| Furan Analysis | ≤0.03 | ||||
| Gas Chromatography Analysis | / |
05 Packing and Shipping
06 Application & Green Benefit
6.1 Long-Term Environmental Benefits
| A long service life means fewer replacements and lower material use, supporting sustainability. | Low-loss design saves energy continuously, cutting costs and environmental impact over decades. | Durable tanks minimize replacements and waste oil, keeping operations cleaner and greener. | The IFD detects faults early, preventing leaks or damage and lowering environmental risks. |
6.2 Applicable Scenarios
