Durable and flexible, three-phase pad-mounted transformers provide reliable support for all your power needs!
01 General
1.1 Project Description
400 kVA padmount transformer was delivered to Chile in 2024. The rated power of the transformer is 400 kVA with KNAN cooling. The primary voltage is 23kV with ±2*2.5% tapping range (NLTC), the secondary voltage is 0.4kV, they formed a vector group of YNyn0, and it is a radial feed and dead front transformer.
Our clients in municipal infrastructure, industrial parks, and commercial developments frequently face critical challenges: ensuring absolute operational safety in public spaces, managing grid expansions within tight physical footprints, and maintaining power continuity under demanding load conditions.
To address these pain points, our core product strategy focuses on compact, fully insulated, and highly resilient design. This is embodied in our 400 kVA pad-mounted transformer, engineered to deliver unmatched reliability and safety.
Key Design Features to Meet Modern Challenges:
Fully Insulated, Safe-by-Design Architecture: The high-voltage inlet utilizes an elbow-type cable plug connected to the bushing, sealing all live parts within insulation. This creates a dead-front design where the terminal surface is at zero potential, fundamentally eliminating the risk of electrical exposure and ensuring personnel safety in even the most congested locations.
Operational Flexibility for Emergency Response: The elbow connector not only simplifies cable connection but also doubles as a load-breaking switch in emergencies. This design provides critical flexibility for maintenance and fault isolation, minimizing downtime and enhancing grid resilience.
Resilient Core Performance with FR3 Fluid: The transformer is filled with high-fire-point FR3 natural ester oil, offering superior environmental and safety benefits. It delivers exceptional performance: low loss, low noise, and a low operating temperature rise. This foundation grants it a strong overload capacity, excellent short-circuit resistance, and robust impact resistance, ensuring reliability during power surges and in harsh operating conditions.
Built with advanced technology and premium materials, our 400 kVA transformer is engineered for a long and dependable service life. Every unit undergoes rigorous full acceptance testing before delivery.
We support our products with a comprehensive one-package service, covering everything from consulting and quoting to manufacturing, installation, commissioning, training, and after-sales support. With our transformers operating successfully in over 50 countries, we are committed to being your most reliable supplier and your trusted partner in power.
1.2 Technical Specification
400 KVA padmount transformer specifications type and data sheet
| Delivered to | Chile |
| Year | 2024 |
| Type | Pad mounted transformer |
| Standard | IEEE Std C57.12.34-2022 |
| Rated Power | 400KVA |
| Feed | Dead |
| Front | Dead |
| Frequency | 50HZ |
| Phase | 3 |
| Cooling Type | KNAN |
| Liquid Insulant | FR3 |
| Primary Voltage | 23KV |
| Secondary Voltage | 0.4KV |
| Winding Material | Copper |
| Angular displacement | Dyn1 |
| Impedance | 4.5% |
| Tap Changer | NLTC |
| Tapping Range | ±2*2.5% |
| No Load Loss | ＜0.75KW |
| On Load Loss | ＜5.605KW |
| Accessories | Standard Configuration |
1.3 Drawings
400 KVA padmount transformer diagram drawing and size.
02 Manufacturing
2.1 Core
| Faced with the industry challenges of transformer inefficiency, instability, and high lifetime costs, our strategy centers on a superior three-column core design. This approach directly tackles these issues by creating a shorter, symmetrical magnetic path that reduces energy loss (iron loss), prevents magnetic bias for stable operation, and minimizes leakage. Furthermore, the design inherently improves natural cooling and provides a robust mechanical structure, resulting in a transformer with higher efficiency, superior resilience, and lower total cost of ownership. |  |
2.2 Winding
 | Our hybrid winding strategy, combining a low-voltage foil winding with a high-voltage wire winding, directly addresses key challenges of insulation integrity, thermal management, and short-circuit resilience. This design creates a more uniform electric field to prevent breakdown, enhances heat dissipation for greater overload capacity, and provides superior mechanical strength to withstand fault currents. Furthermore, the close coupling of the windings optimizes the magnetic circuit, reducing leakage losses to achieve higher overall efficiency. |
2.3 Tank
| To ensure transformer reliability and longevity under high loads and harsh environments, our design strategy integrates a robust tank and advanced cooling system. This is realized through a forced-oil circulation radiator for superior heat dissipation, a high-strength stainless steel tank with superior sealing to prevent leaks and corrosion, and critical safety features like a pressure relief valve, collectively guaranteeing stable performance and extended service life in demanding applications. |  |
2.4 Final Assembly
 | To ensure manufacturing excellence and long-term operational reliability, our production strategy integrates rigorous quality control at every critical stage. This encompasses precise component inspection, specialized insulation treatment during core-winding assembly, and the use of sealed, corrosion-resistant enclosures. The methodology is completed with secure electrical connections, integrated safety protections, and efficient cooling systems, delivering a transformer built for superior performance and durability. |
03 Testing
| No. | Test Item | Unit | Acceptance Values | Measured Values | Conclusion |
| 1 | Resistance Measurements | % | Maximun resistance unbalance rate≤5% | 1.18 | Pass |
| 2 | Ratio Tests | % | The deviation of voltage ratio on the principal tapping: ≤0.5% Connection symbol: Dyn1 | -0.02% ~ -0.01% | Pass |
| 3 | phase-relation tests | / | Dyn1 | Dyn1 | Pass |
| 4 | No-load losses and excitation current | / | I0 :: provide measured value | 0.52% | Pass |
| P0: provide measured value(t:20℃) | 0.625kW | ||||
| 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 | 4.82% | ||||
| Pk: measured value | 5.551kW | ||||
| Pt: measured value | 6.176 kW | ||||
| Efficiency not less than 99.00% | 99.07% | ||||
| 6 | Applied Voltage Test | kV | HV: 40kV 60s LV: 10kV 60s | No collapse of the test voltage occurs | Pass |
| 7 | Induced Voltage Withstand Test | kV | Applied voltage (KV):2Ur | No collapse of the test voltage occurs | Pass |
| Induced voltage(KV):46 | |||||
| Duration(s):40 | |||||
| Frequency (HZ): 150 | |||||
| 8 | Leakage Test | kPa | Applied pressure：20kPA | No leakage and no Damage | Pass |
| Duration：12h | |||||
| 9 | Insulation Resistance Measurement | GΩ | HV-LV to Ground : | 3.76 | / |
| LV-HV to Ground: | 4.41 | ||||
| HV&LV to Ground: | 2.51 | ||||
| 10 | Oil Dielectric Test | kV | ≥45 | 54.35 | Pass |
04 Packing and Shipping
4.1 Packing
| Our three-phase pad-mounted transformer is securely packaged in a custom-built, heavy-duty wooden crate, designed to ensure complete protection during transit and storage. The robust wooden frame is reinforced with steel straps to prevent shifting, while the transformer itself is internally blocked and braced to absorb any shock or impact. This packaging solution guarantees that your unit arrives on site in perfect condition, ready for installation. |  |
4.2 Shipping
 | Our padmount transformer are optimally prepared for safe and efficient ocean freight. Each unit is securely block-mounted within its heavy-duty wooden crate, fully weatherproofed to withstand harsh marine conditions. This robust packaging, combined with clear lifting and stacking markings, ensures seamless handling, deck stowage, and on-time delivery to global project sites. |
05 Site And Summary
To meet the critical challenges of ensuring power distribution safety, adaptability, and efficiency across diverse settings, our strategic focus is on a fully insulated, compact three-phase padmount transformer. Its elbow-type plug-in connectors create a dead-front design for maximum safety in public spaces, while its low-loss core and corrosion-resistant tank ensure high energy efficiency and long-term reliability with minimal maintenance, delivering a resilient power solution for industrial, commercial, and residential projects.
