Utility-Grade Reliability for EV Charging and Mixed-Use Projects.
01 General
1.1 Project Description
In 2026, an American contractor ordered a 1250 kVA three phase pad mount transformer for a commercial EV charging and mixed-use distribution project, where stable outdoor power distribution, operational safety, and long-term reliability were critical for daily charging infrastructure and facility operation. The transformer was installed between the local 12.47 kV utility feeder and the site’s 0.6 kV low-voltage distribution network. The transformer was manufactured according to IEEE Std C57.12.34-2022 standards, with a rated voltage of 12.47 kV GrdY / 7.2 kV to 0.6 kV Y / 0.347 kV, KNAN cooling, YNyn0 vector group, aluminum windings, and 5.75% impedance; while the 99.45% DOE efficiency design helped reduce long-term operating loss under continuous commercial loading conditions. FR3 insulating fluid was selected to improve fire safety and environmental performance for outdoor public-access installation areas. To improve operational stability under fluctuating charging loads and lightning-prone utility conditions, the 1250 kVA transformador pad mounted unit adopted a three phase five-leg core structure for balanced magnetic performance and neutral stability, together with integrated lightning arresters, grounding bars, bayonet fuse protection, and a four-position loadbreak switch to enhance surge protection, switching flexibility, and maintenance safety across the distribution system.
1.2 Technical Specification
1250 kVA transformador pad mounted specification and data sheet
| Delivered to | America |
| Year | 2026 |
| Type | Three phase pad mount transformer |
| Standard | IEEE Std C57.12.34-2022 |
| Rated Power | 1250 kVA |
| Frequency | 60HZ |
| Feed | Loop |
| Front | Dead |
| Phase | three |
| Cooling Type | KNAN |
| Liquid insulant | FR3 Oil |
| Primary Voltage | 12.47 kV GrdY / 7.2 kV |
| Secondary Voltage | 0.6 kV Y / 0.347 kV |
| Vector Group | YNyn0 |
| Winding Material | Aluminum |
| Impedance | 5.75% |
| Efficiency and Losses Standard | 99.45 % DOE Efficiency |
| Tap Changer | NLTC |
| Tapping Range | ±2*2.5% |
| No Load Loss | 1410 W |
| On Load Loss | 9050 W |
| Accessories | lightning arrester |
1.3 Drawings
1250 kVA transformador pad mounted drawing and nameplate
02 Manufacturing
2.1 Five-Leg Core
The transformer adopted a three phase five-leg core structure to improve magnetic flux balance, voltage stability, and neutral performance under nonlinear and unbalanced loading conditions commonly found in commercial charging infrastructure. High-grade CRGO silicon steel laminations were used to reduce no-load loss and operational noise, while the rigid clamping structure improved mechanical stability during transportation and fault conditions.
2.2 Winding
The winding system used aluminum conductors designed for reliable thermal performance, stable voltage regulation, and cost-efficient long-term operation in North American distribution systems. The insulation structure was optimized to coordinate with surge protection devices and outdoor operating conditions, while the 12.47 kV to 0.6 kV winding configuration supported continuous commercial load demand with improved dielectric reliability and temperature control.
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2.3 DOE Efficiency
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This 1250 kVA transformador pad mounted unit was designed to achieve 99.45% DOE efficiency, helping reduce long-term operating costs and energy losses across continuous commercial distribution applications. By optimizing core loss, load loss, and thermal performance together, the transformer maintains stable efficiency under fluctuating EV charging and building power demand conditions.
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2.4 Surge Protection & Grounding
Integrated lightning arresters and compartment grounding bars were designed together to provide an effective low-impedance surge dissipation path, helping protect transformer insulation and sensitive EV charging equipment from transient overvoltage events.
2.5 Tank Protection
The transformer adopted a dead-front loop-feed tank structure designed for safe underground cable operation and long-term outdoor service reliability. Powder coated white paint (RAL 9003) improved corrosion resistance and reduced solar heat absorption in exposed installation areas.
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03 Testing
Testing Standard
Testing Results
04 Packing and Shipping
The transformer features compact overall dimensions of 1680 × 1580 × 1880 mm, with approximately 1000 liters of insulating oil and a total operating weight of 4000 kg, providing a balanced combination of installation flexibility, thermal stability, and durable outdoor operational performance.
