Eco-safe, resilient, and built for North America's underground power - 750 kVA liquid filled transformers you can trust
01 General
1.1 Project Description
Delivered to the United States in 2025, this 750kVA liquid-filled three-phase pad-mounted transformer is engineered in full compliance with IEEE Std C57.12.34-2022, making it well-suited for medium-voltage distribution systems across North America.
This 750 kVA liquid-filled transformer features a loop-feed configuration for flexible network integration and enhanced power reliability. The dead-front design ensures safe operation in public or high-access areas by eliminating exposed live components. Elbow arrester for overvoltage protection. Its five-leg core construction effectively accommodates zero-sequence flux under unbalanced load conditions, improving performance in real-world distribution networks.
FR3 natural ester fluid as the insulating medium. FR3 is a fire-safe, biodegradable, and environmentally friendly alternative to mineral oil, offering a high flash point and excellent thermal performance.
It is ideal for suburban neighborhoods, industrial parks, commercial facilities, and campuses requiring dependable underground distribution.
1.2 Technical Specification
750kVA three phase pad mounted transformer specification and data sheet
| Delivered to | America |
| Year | 2025 |
| Type | Three phase pad mount transformer |
| Standard | IEEE Std C57.12.34-2022 |
| Rated Power | 750KVA |
| Frequency | 60HZ |
| Feed | Loop |
| Front | Dead |
| Phase | three |
| Cooling Type | KNAN |
| Liquid insulant | FR3 Oil |
| Primary Voltage | 12.47 Kv |
| Secondary Voltage | 0.6 Kv |
| Vector Group | YNyn0 |
| Winding Material | Copper |
| Number of core leg | 5 |
| Impedance | 5.75% |
| Tap Changer | NLTC |
| Tapping Range | ±2*2.5% |
| No Load Loss | 0.99 KW |
| On Load Loss | 5.6 KW |
| Accessories | Elbow arrester |
1.3 Drawings
750kVA three phase pad mounted transformer dimensions and weight details
02 Manufacturing
2.1 Core
The 750kVA, 12.47/0.6kV YNyn0 pad-mounted liquid-immersed transformer adopts a five-leg core design to ensure proper handling of zero-sequence flux caused by unbalanced loads or grounded systems. The additional side limbs provide a low reluctance path for zero-sequence flux, ensuring better insulation performance, lower noise, and improved reliability under real-world distribution network conditions.
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2.2 Winding
 | The coils for the YNyn0 vector group transformer have been completed using copper conductors-foil winding for the LV side and wire winding for the HV side. Workers are now removing the winding molds after ensuring the coils meet dimensional and insulation requirements. Preparation is underway for the next step: core and coil assembly, where the windings will be mounted onto the iron core structure. |
2.3 Tank
The sealed tank with bolted cover, made of mild steel, has completed its painting process and is awaiting quality inspection. Inspectors will check paint film thickness, surface smoothness, and overall appearance. If defects such as blisters, peeling, pinholes, bare spots, uneven coating, or scratches are found, the painting supervisor will be notified and a rework order issued. The next step is tank assembly, including the main tank, front cabinet door, skid base, and enclosure, etc. |  |
2.4 Final Assembly
 | The active part assembly of the 750kVA 12.47/0.6kV three-phase pad-mounted transformer has been completed, including core stacking, winding insertion, lead connection, and installation of the NLTC (no-load tap changer). A technician is currently conducting the insulation resistance test between windings and ground using a digital megohmmeter to verify the insulation condition before moving to the next production step. |
03 Testing
Routine Test and Testing Standard
- Insulation Resistance Measurements： According to IEEE C57.12.90-2021
Purpose
Supervise the insulation materials and manufacturing process and check the dryness and cleanliness of the body. - Ratio Tests： According to IEEE C57.12.90-2021 Clause 7 & Clause 9.1
Purpose
a) Check whether the tap lead is connected correctly, and the voltage ratio of each winding is correct and meets the requirements.
b) Whether the linkage group meets the requirements of the agreement. - Phase-relation Test： According to IEEE C57.12.90-2021 Clause 6
Purpose
a) Whether the Polarity and phase relation meet the requirements of the agreement.
b) Each phase of a polyphase transformer shall have the same relative polarity - Resistance Measurement：According to IEEE C57.12.90-2021 Clause 5
Purpose
a) Calculation of the I²R component of conductor losses
b) Calculation of winding temperatures at the end of a temperature-rise test
c) As a quality control test of the manufacturing process
d) As a base for assessing possible damage in the field - No Load Losses and No Load Current：According to IEEE C57.12.90-2021 Clause 8 & Clause 9.3
Purpose
a) Measure no-load losses at a specified excitation voltage and a specified frequency.
b) Measure no-load current and no-load loss whether it complies with standards and technical protocols. - Load Losses, Impedance Voltage and Efficiency：According to IEEE C57.12.90-2021 Clause 9 & 9.2
Purpose
Check if the impedance voltage and load loss values in accordance with standards and technical protocols. - Applied Voltage Test：According to IEEE C57.12.90-2021 Clause 10.6
Purpose
Check the withstand strength of the transformer’s main insulation. - Induced Voltage Withstand Test：According to IEEE C57.12.90-2021 Clause 10.7
Purpose
Check the longitudinal insulation strength of the transformer. - Leak Testing with Pressure for Liquid Immersed Transformers：According to IEC60076-1
The leaking test at 20KPa shall be conducted for 24h without leakage. No permanent deformation.
Purpose
To prove the transformer tank will not leak in service.
04 Packing and Shipping
05 Site And Summary
From core construction to final assembly, the manufacturing process emphasizes structural integrity, electrical performance, and long-term durability. A five-leg core design is adopted to enhance performance under unbalanced load conditions, while copper windings ensure efficient electrical conductivity and thermal stability. The fully sealed and painted tank undergoes rigorous quality checks before integration into the enclosure assembly.
Each production stage-core stacking, coil winding, tank fabrication, and insulation testing-is meticulously executed to ensure compliance with design requirements and field performance expectations. The result is a robust, utility-grade transformer built for dependable service in demanding distribution environments.
