Industrial Tough, Utility Smart – Pad-Mounted Transformers for Demanding Loads.
01 General
1.1 Project Description
75 kVA three phase pad mounted transformer was delivered to America in 2025. The rated power of the transformer is 75 kVA with ONAN cooling. The primary voltage is 23GRDY/13.28 kV with ±2*2.5% tapping range (NLTC), the secondary voltage is 0.208y/0.12 kV, they formed a vector group of YNyn0.
Pad-mounted transformers are compact, ground-level power distribution units designed for safe and efficient electricity delivery in urban, suburban, and industrial settings. Encased in durable, tamper-resistant enclosures, these transformers provide reliable voltage conversion while minimizing footprint and environmental impact. Their below-eye-level installation makes them ideal for space-constrained areas where overhead lines are impractical or aesthetically undesirable.
Engineered for both safety and performance, modern pad-mounted transformers feature advanced insulation systems, corrosion-resistant materials, and optional smart monitoring capabilities for real-time diagnostics. Whether powering residential neighborhoods, commercial complexes, or industrial facilities, these units deliver quiet operation with reduced maintenance needs compared to traditional pole-mounted alternatives.
1.2 Technical Specification
75 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 | 75 kVA |
| Frequency | 60HZ |
| Phase | 3 |
| Feed | Radial |
| Front | Dead |
| Cooling Type | ONAN |
| Primary Voltage | 23GrdY/13.28 kV |
| Secondary Voltage | 0.208GrdY/0.12 kV |
| Winding Material | Aluminum |
| Angular displacement | YNyn0 |
| Impedance | 3.25% |
| Tap Changer | NLTC |
| Tapping Range | ±2*2.5% |
| No Load Loss | 0.08 kW |
| On Load Loss | 1.27 kW |
| Accessories | Standard Configuration |
1.3 Drawings
75 kVA pad mounted transformer diagram drawing and size.
02 Manufacturing
2.1 Core
| This pad-mounted transformer features an innovative five-limb wound core with three winding limbs (A/B/C phases) and two flux-return limbs, delivering superior magnetic balance and efficiency. The seamless spiral-wound grain-oriented silicon steel core reduces no-load losses by 25-30% versus traditional designs. Key advantages include: • Enhanced load balancing and short-circuit withstand • Ultra-low noise and minimal heat rise |  |
2.2 Winding
 | This three winding transformer features an optimized design with aluminum foil low-voltage windings and copper wire high-voltage windings, delivering superior efficiency and thermal performance. The third winding provides flexible voltage regulation or auxiliary power capability. Combining the advantages of foil and wire winding technologies, this compact unit offers excellent current distribution, short-circuit withstand, and heat dissipation – making it ideal for modern power distribution networks requiring reliable three winding transformer solutions in utility, commercial and industrial applications. |
2.3 Tank
| This transformer features a robust, weatherproof oil tank constructed from high-grade corrosion-resistant steel for superior durability in outdoor installations. The oil tank incorporates multiple engineered safety features including: • Leak-proof welded seams with pressure-tested integrity • Expansion conservator with oil level indicator for thermal management • Corrosion protection through sandblasting and multi-layer epoxy coating |  |
2.4 Final Assembly
 | 1. Winding Installation: Precisely mount the HV/LV windings onto the wound core, ensuring proper insulation alignment. 2. Electrical Connections: Connect winding leads to tap changers, bushings, and other components, then secure and test conductivity. 3. Core-Coil Drying: Place the assembled active part into a drying oven for vacuum heating to remove moisture and enhance insulation. 4. Tank Insertion: Hoist and position the dried active part into the tank, securing it while maintaining proper insulation clearance. 5. Accessory Installation: Attach bushings, pressure relief devices, oil gauges, etc., and seal all interfaces. 6. Oil Filling & Sealing: Vacuum-fill insulating oil to the specified level, check oil quality and tank tightness, then finalize closure. |
03 Testing
| No. | Test Item | Unit | Acceptance Values | Measured Values | Conclusion |
| 1 | Resistance Measurements | % | Maximum resistance unbalance rate | 1.07 | Pass |
| 2 | Ratio Tests | % | The deviation of voltage ratio on the principal tapping: ≤0.5% | -0.03~0.01 | Pass |
| 3 | Phase-relation tests | / | YNyn0 | YNyn0 | Pass |
| 4 | No-load losses and excitation current | % | I0 :: provide measured value | 0.31 | Pass |
| kW | P0: provide measured value | 0.0795 | |||
| / | the tolerance for no load loss is ±10% | / | |||
| 5 | Load losses, impedance voltage, total losses and efficiency | / | t:85℃ the tolerance for impedance is ±7.5% the tolerance for total load loss is ±6% | / | Pass |
| % | Z%: measured value | 3.29 | |||
| kW | Pk: measured value | 1.156 | |||
| kW | Pt: measured value | 1.2355 | |||
| % | Efficiency not less than 99.03% | 99.10 | |||
| 6 | Applied Voltage Test | / | HV:10kV 60s LV: 10kV 60s | No collapse of the test voltage occurs | Pass |
| 7 | Induced Voltage Withstand Test | / | Applied voltage (KV):0.624 | No collapse of the test voltage occurs | Pass |
| Duration(s):30 | |||||
| Frequency (HZ): 240 | |||||
| 8 | Insulation Resistance Measurement | GΩ | HV-LV to Ground: | 190 | Pass |
| LV-HV to Ground: | 311 | ||||
| 9 | Leakage Test | / | Applied pressure：20kPA | No leakage and no Damage | Pass |
| Duration：12h | |||||
| 10 | Oil Test | kV | Dielectric Strength | 57.3 | Pass |
| mg/kg | Moisture Content | 10.6 | |||
| % | Dissipation Factor | 0.155 | |||
| mg/kg | Furan Analysis | ≤0.1 | |||
| / | Gas Chromatography Analysis | / |
04 Packing and Shipping
4.1 Packing
| The pad mounted transformer is packaged in a wooden crate with an additional layer of aluminum foil bag covering the exterior, creating a dual-protection structure. The wooden crate provides robust support and impact resistance, while the outer aluminum foil bag effectively shields the unit from moisture, dust, and other environmental contaminants, preventing corrosion and electrical performance degradation during transportation and storage. This packaging method combines mechanical durability with environmental sealing, making it suitable for long-distance shipping or harsh storage conditions. |  |
4.2 Shipping
 | The pad-mounted transformer is shipped under CIF (Cost, Insurance, and Freight) terms, with the destination port being Memphis, TN, USA. The unit is packed in a wooden crate wrapped with an aluminum foil bag for moisture, dust, and mechanical damage protection. The shipment will be transported via ocean freight to the designated port, with the seller responsible for insurance and freight costs until the goods are unloaded at the destination. The entire transportation process complies with international shipping standards to ensure the safety and integrity of the equipment during transit. |
05 Site And Summary
As a critical component in power distribution systems, the Pad-Mounted Transformer stands out for its compact design, high efficiency, and exceptional reliability, making it ideal for urban grids, industrial zones, and renewable energy projects. Manufactured in compliance with international standards, every unit delivers industry-leading performance in safety, energy efficiency, and durability. Whether facing harsh environments or complex power demands, our transformers ensure stable and efficient operation. For customized solutions or technical support, feel free to contact our team-we’re committed to providing expert assistance tailored to your needs.
