Precise energy conversion ensures safety and stability, as three-phase pad-mounted transformers empower the future of smart grids!
01 General
1.1 Project Description
300 kVA pad mounted transformer was delivered to America in 2024. This three phase pad mounted transformer was purchased by a Jamaican customer, TAK. It is worth noting that the low voltage dual voltage is the unique feature of this transformer. The rated power of the transformer is 300 kVA with ONAN cooling. The primary voltage is 12GrdY/6.9kV with ±2*2.5% tapping range (NLTC), the secondary voltage is 0.24/0.12kV, they formed a vector group of YNd11, and it is a loop feed and dead front transformer.
Pad mounted transformers, also known as American-style prefabricated cabins, are highly integrated power distribution units that compactly combine high-voltage switchgear, transformers, and other distribution components. They utilize load switches and fuses as primary protective devices, featuring a compact design, easy operation, flexible installation, and low maintenance costs. Due to their small footprint and strong adaptability, American-style box transformers are widely used in urban power distribution network construction, community power upgrades, and space-constrained areas such as commercial centers, residential communities, and temporary power projects.
Advantages: Compact size with a highly integrated structure; fully sealed oil tank and fully insulated design for safe and reliable operation; suitable for both ring network and terminal power supply, ensuring convenient operation and reliable power distribution; strong overload capacity and excellent resistance to sudden short circuits; superior impact resistance; energy-efficient with low loss, meeting or exceeding modern efficiency standards; cable heads capable of handling 200A load current, with extended mechanical and electrical lifespans.
1.2 Technical Specification
300 kVA transformer specifications type and data sheet
| Delivered to | Jamaica |
| Year | 2024 |
| Type | Pad mounted transformer |
| Standard | IEEE Std C57.12.34-2022 |
| Rated Power | 300KVA |
| Frequency | 50HZ |
| Phase | 3 |
| Feed | Loop |
| Front | Dead |
| Cooling Type | ONAN |
| Primary Voltage | 12GRDY/6.9 KV |
| Secondary Voltage | 0.24/0.12 KV |
| Winding Material | Copper |
| Angular displacement | YNd11 |
| Impedance | 4.75%(±7.5%) |
| Tap Changer | NLTC |
| Tapping Range | ±2*2.5% |
| No Load Loss | ≤0.53KW |
| On Load Loss | ≤4.755KW |
| Efficiency | ≥98.94% |
| Accessories | Standard Configuration |
1.3 Drawings
300 kVA pad mounted transformer diagram drawing and size.
02 Manufacturing
2.1 Core
| The three-phase five-limb transformer core features a unique magnetic circuit design characterized by three main limbs and two auxiliary limbs. The windings on the main limbs carry the primary magnetic flux, while the auxiliary limbs are used to close the magnetic circuit, effectively reducing leakage flux loss and short-circuit currents. Core clamps are components used to secure and fasten the transformer core. They are usually made of high-strength non-magnetic materials, such as stainless steel or special aluminum alloys, to provide excellent mechanical strength without affecting the core’s magnetic performance. The design of the clamps also needs to meet heat dissipation requirements to ensure thermal stability during operation. |  |
2.2 Winding
 | YNd11 Connection Group The high-voltage star connection provides a neutral point, meeting the needs of unbalanced loads, while the low-voltage delta connection reduces third harmonics, ensuring stable power supply. The 11 o’clock phase shift minimizes harmonic interference in the system. Low-Voltage Foil Winding Design Excellent heat dissipation with low temperature rise, extending the transformer’s lifespan. Strong short-circuit resistance and uniform inter-turn electric field distribution, ensuring reliable operation. High-Voltage Wire Winding Design Compact structure saves space. Stable electrical performance with reliable insulation. |
2.3 Tank
| The oil tank adopts a fully sealed design, effectively preventing external air and moisture from entering, ensuring the long-term stability of the transformer oil and extending the equipment’s lifespan. Designed to be compact and space-saving, the oil tank is made of high-quality steel with high mechanical strength, capable of withstanding external impacts and internal pressure. The exterior surface is treated with spray coating or hot-dip galvanization, providing excellent corrosion resistance for harsh environments such as high humidity, salt spray, or chemical exposure. | |
2.4 Final Assembly
 | Core and Winding Assembly Securely assemble the tested core with the high- and low-voltage windings, ensuring the electrical performance meets design specifications. Oil Tank Installation Install the transformer body into the oil tank, connect internal cables, and complete the sealing process. External Equipment Installation Install high-voltage components such as load switches and current-limiting fuses, as well as low-voltage output cabinets and cable terminals. Oil Filling and Leak Testing Inject insulating oil, conduct pressure tests, and check for leaks to ensure sealing and cooling performance. |
03 Testing
04 Packing and Shipping
05 Site And Summary
In conclusion, the three-phase pad-mounted transformer is an essential solution for reliable and efficient power distribution. With its robust design and advanced technology, it meets the demands of modern electrical infrastructure across various applications. Our transformers are tailored to deliver optimal performance while prioritizing safety and sustainability. By choosing our three-phase pad-mounted transformers, you are investing in a product that not only enhances your electrical system’s efficiency but also contributes to a greener future. Partner with us to experience unparalleled quality and innovative solutions for your power distribution needs.
