Safe, reliable, quiet and green — the pad-mounted transformer guards every kilowatt-hour for your city.
01 General
1.1 Project Description
1000 kVA three phase pad mounted transformer was delivered to USA in 2025. The rated power of the transformer is 1000 kVA with KNAN cooling. The high voltage is 13.8D kV with ±2*2.5% tapping range (NLTC), the low voltage is 0.48Y/0.277 kV, they formed a vector group of Dyn1.
This 1000 kVA Pad-Mounted Transformer is engineered for reliable and efficient power distribution in underground residential distribution (URD) and commercial loop feed applications. Designed with a three-phase, three-limb core, this unit complies with DOE energy efficiency standards, ensuring minimal core and copper losses for optimized operational cost savings.
The transformer features a loop feed configuration, allowing for enhanced system reliability through redundant cabling and future network expansion. It is insulated with FR3 natural ester fluid, a biodegradable dielectric fluid that offers superior fire safety (high fire point) and extends the insulation life of the unit compared to conventional mineral oil. Integrated surge arresters provide robust protection against transient overvoltages, safeguarding the asset and the connected load.
Housed in a durable enclosure finished with a powder-coated white (RAL 9003) paint system, the unit is designed to withstand harsh environmental conditions while maintaining a clean, corrosion-resistant aesthetic suitable for residential and urban installations.
As one of professional pad-mounted transformer manufacturers, we understand the critical importance of reliability and safety in power distribution. For over a decade, we have focused on researching, developing, and producing pad-mounted transformers that meet IEEE/ANSI/CSA standards, dedicated to providing efficient, durable, and maintenance-free power distribution equipment for residential areas, commercial centers, industrial parks, and renewable energy projects across North America, South America, and around the globe.
1.2 Technical Specification
1000 kVA pad mounted transformer specifications type and data sheet
| Delivered to | USA |
| Year | 2025 |
| Type | Pad mounted transformer |
| Standard | IEEE Std C57.12.34-2022 DOE 2016 |
| Rated Power | 1000 kVA |
| Frequency | 60HZ |
| Phase | 3 |
| Feed | Loop |
| Front | Dead |
| Cooling Type | KNAN |
| Primary Voltage | 13.8D kV |
| Secondary Voltage | 0.48y/0.277 kV |
| Winding Material | Aluminum |
| Vector Group | Dyn1 |
| Impedance | 5.75% |
| Efficiency | 99.43% |
| Tap Changer | NLTC |
| Tapping Range | ±2*2.5% |
| No Load Loss | 1.3 kW |
| On Load Loss | 6.94 kW |
1.3 Drawings
1000 kVA pad mounted transformer diagram drawing and size.
1.4 Applicable Standards
- IEEE Std C57.12.34-2022 – Pad‑Mounted, Compartmental‑Type, Self‑Cooled, Three‑Phase Distribution Transformers
- IEEE Std C57.12.00-2021 – General Requirements for Liquid‑Immersed Distribution, Power, and Regulating Transformers
- IEEE Std C57.12.90-2021 – Test Code for Liquid‑Immersed Distribution, Power, and Regulating Transformers
- DOE 2016 – U.S. Department of Energy energy efficiency standard (efficiency ≥ 99.43%; measured 99.46%)
All design, manufacturing, and testing strictly follow the above standards, ensuring full compliance for the North American market.
02 Manufacturing
2.1 Core
- Material: High‑permeability cold‑rolled grain‑oriented silicon steel
- Construction: Three‑leg core with step‑lap stacking to reduce no‑load losses and noise
- Fastening: Non‑metallic binding straps and high‑strength clamps ensure mechanical strength and short‑circuit withstand capability
- Result: Measured no‑load loss 1.200 kW, better than the guaranteed value (≤1.3 kW +10%)
2.2 Winding
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2.3 Tank
| Material: Mild steel with powder coating (RAL 9003 white) for corrosion resistance and UV protection Construction: Sealed tank with bolted cover – leak‑proof design suitable for long‑term outdoor service Accessories: Top oil thermometer, oil level gauge, vacuum pressure gauge Pressure relief device (pull‑ring type), oil drain valve with sampling valve Upper pressure connection and fill plug Leak Test: 20 kPa static pressure for 24 hours – no leakage, no permanent deformation (passed) |  |
2.4 Final Assembly
HV Compartment:
6 separable insulated (dead‑break) bushings
3 bayonet fuses + 3 current‑limiting fuses + 1 four‑position load break switch
LV Compartment:
3 resin‑cast bushings with spade terminals; neutral grounding pad (XO)
Grounding: One unpainted stainless steel grounding pad (two holes) in each of HV and LV compartments
Accessories: Stainless steel nameplate, lifting lugs, jacking pads, three lightning arresters
Final Inspection: Full routine tests (ratio, resistance, no‑load & load losses, impedance, dielectric, leak, etc.) performed on completed unit to verify overall performance
03 Testing
All tests passed with the following key results:
| Test Item | Requirement | Measured Value | Result |
| No‑Load Loss | ≤ 1.3 kW (+10%) | 1.200 kW | ✅ Better |
| Load Loss (85℃) | ≤ 6.94 kW (+6%) | 6.661 kW | ✅ Better |
| Impedance | 5.75% ±7.5% | 5.80% | ✅ Pass |
| Efficiency | ≥ 99.43% | 99.46% | ✅ Better than DOE |
| Applied Voltage Withstand | HV: 34kV / LV: 10kV, 60s | No breakdown | ✅ Pass |
| Induced Voltage Withstand | 2Ur, 150Hz, 48s | No breakdown | ✅ Pass |
| Leak Test | 20kPa, 24h | No leakage | ✅ Pass |
| Insulation Resistance | – | ≥1.39 GΩ | ✅ Excellent |
| DC Resistance Unbalance | ≤ 5% | Max. 5.93% | ✅ Pass |
All test results meet or exceed the required values, confirming the transformer’s high reliability and long‑term operational stability.
04 Quality Assurance
 | Raw material control: All silicon steel sheets, aluminum wires, FR3 oil and sealing parts are selected from international well-known brands or suppliers that have passed strict incoming inspection. Process control: Fully automated winding equipment and vacuum oil injection technology are adopted. For key processes such as welding and assembly, first article inspection and in-process inspection are carried out. Traceability system: Each transformer has a unique serial number, and all production and testing data are archived and preserved, enabling full life-cycle traceability. |
05 Packing and Shipping
Inner Packaging: Transformer is placed into a foil bag with desiccant and vacuum‑sealed to prevent rust and moisture ingress
Outer Packaging: Wooden crate with corner protectors (foam/plastic/cardboard); forklift and center‑of‑gravity markings sprayed on the crate
Transport: Suitable for sea and land transport; designed for long‑distance shipping and multiple handling
Labeling: All labels comply with standard, including “Do Not Touch” and “Disconnect Switch” warnings
06 Site And Summary
This 1000 kVA three-phase pad-mounted transformer is fully compliant with IEEE C57.12.34-2022 and DOE 2016. It passed all routine tests per IEEE C57.12.90-2021, achieving 99.46% efficiency, 1.200 kW no-load loss, and zero leakage. Vacuum-sealed in foil bags with desiccant and packed in wooden crates, it ensures safe delivery and long-term outdoor reliability. We are a leading pad-mount transformer manufacturers with 17+ years of ODM/OEM experience.
