Secure Power, Contained. The Three Phase Pad Mounted Transformer Solution.
01 General
1.1 Project Description
300 kVA three phase pad mounted transformer was delivered to America in 2024. The rated power of the transformer is 300 kVA with ONAN cooling. The high voltage is 34.5GRDY/19.92 kV with ±2*2.5% tapping range (NLTC), the low voltage is 0.208GrdY/0.12 kV, they formed a vector group of YNyn0.
A three-phase pad-mounted transformer is a critical component in electrical distribution networks, designed for commercial, industrial, and residential use. As the name suggests, these units are self-contained within a lockable, tamper-resistant steel enclosure and are installed on a concrete pad at ground level. The robust steel housing is typically finished with a corrosion-resistant coating, ensuring long-term durability against environmental elements. It serves as a ubiquitous interface between the utility’s primary feeder system and the end-user’s secondary service.
The design is characterized by its robustness and reliability. The core and coil assembly, immersed in dielectric fluid, is housed within the sealed steel tank. This fluid acts as both a highly effective insulating medium and a coolant. Key features include compartmentalized high-voltage and low-voltage compartments within the steel enclosure, fault indicators, and pressure-relief devices, ensuring operational safety and minimal maintenance. Due to their compact footprint, proven durability afforded by the steel construction, and high overload capacity, these transformers are the preferred solution for underground distribution systems.
1.2 Technical Specification
300 kVA pad mounted transformer specifications type and data sheet
| Delivered to | USA |
| Year | 2024 |
| Type | Pad mounted transformer |
| Standard | IEEE C57.12.00 |
| Rated Power | 300 kVA |
| Frequency | 60HZ |
| Phase | 3 |
| Feed | Loop |
| Front | Dead |
| Cooling Type | ONAN |
| Primary Voltage | 34.5GRDY/19.92 kV |
| Secondary Voltage | 0.208GrdY/0.12 kV |
| Winding Material | Aluminum |
| Angular displacement | YNyn0 |
| Impedance | 5% |
| Efficiency | 99% |
| Tap Changer | NLTC |
| Tapping Range | ±2*2.5% |
| No Load Loss | 0.46 kW |
| On Load Loss | 4.675 kW |
1.3 Drawings
300 kVA pad mounted transformer diagram drawing and size.
02 Manufacturing
2.1 Core
At its heart lies a laminated silicon steel core in a three-phase, five-limb configuration. This core is engineered for low sound levels and high efficiency, with each limb carrying the HV and LV coils of a single phase. The entire core-and-coil assembly is securely clamped to withstand the mechanical stresses of short-circuit currents and ensure long service life.
2.2 Winding
 | It utilizes an aluminum foil for the LV winding, maximizing mechanical stability and heat dissipation, and copper magnet wire for the HV winding, ensuring optimal voltage distribution and impulse withstand capability. This hybrid approach balances performance, reliability, and cost-effectiveness. |
2.3 Tank
This transformer’s tank serves as a protective vessel, coolant reservoir, and heat exchanger. Engineered for durability, its sealed structure prevents moisture ingress and is typically coated for corrosion resistance. The tank’s design, incorporating corrugations, safely dissipates heat losses while maintaining a low aesthetic profile.
2.4 Final Assembly
 | The complete assembly results in a tamper-resistant, weatherproof enclosure where the core-coil and key components are internally secured and immersed in insulating fluid. The final product includes all necessary cooling, protection, and monitoring systems, pre-assembled and ready for direct placement on a concrete pad and connection to the distribution network. |
03 Testing
Final verification includes key electrical and mechanical tests. Initial diagnostics (DC resistance, insulation resistance, voltage ratio) ensure correct wiring. Robustness is tested through AC dielectric withstand tests at power and high frequencies. Operational efficiency is confirmed by measuring no-load/losses and impedance, while a seal test guarantees long-term fluid containment.
04 Packing and Shipping
4.1 Packing
The packaging process of the three phase pad mounted transformer is as follows: first, place a tin foil bag on the transformer tray to cover the transformer, put desiccant inside the bag, seal the bag with an opening left. Use a vacuum cleaner to pump out the gas in the bag and seal the opening with a sealing machine. Then, add corner protectors (foam, plastic or pressed cardboard special corner protectors) around the transformer and wrap it with protective film. Finally, package it in an external wooden box sprayed with forklift and center of gravity markings.
4.2 Shipping
The shipment process begins with overland truck transport to the port of departure. There, the unit is consolidated into a standard shipping container for its ocean crossing to the United States. This streamlined intermodal logistics chain provides a secure, weatherproof, and standardized solution for door-to-port delivery.
05 Site And Summary
Ultimately, our Pad-Mounted Transformer is built with one core mission: to provide safe, continuous, and efficient power transformation for your customers. Its proven design and rigorous testing provide the peace of mind you need. Invest in this critical link to a stronger and more sustainable grid.
