31 Three-Phase Pad-Mounted Transformers Delivered for a North American Distribution Project

Finished units from the 2550 kVA and 3750 kVA batches before export shipment.

Winley Electric completed a 31-unit delivery of three-phase pad-mounted transformers for a North American distribution project, covering 2550 kVA and 3750 kVA ratings across 12.87 kV and 34.5 kV primary voltage requirements.

The order was not a single repeat build. It covered three controlled batches with different ratings and voltage classes, so engineering, production, testing, packing and export loading had to be managed under one delivery plan.

• 31 units delivered for a North American distribution project.
• Three production batches covering 10 units of 2550 kVA at 12.87/0.48 kV, 15 units of 2550 kVA at 34.5/0.48 kV, and 6 units of 3750 kVA at 12.87/0.48 kV.
• North American design basis built to ANSI C57.12.34 for 60 Hz outdoor pad-mounted applications.
• UL/cUL Listed product line under UL File No. E536138.
• Factory release checks covering electrical, pressure integrity and insulating-oil tests.
• Export-ready shipment with packing and container loading completed as part of the same delivery plan.

The customer needed a supplier that could handle scale and variation at the same time. The practical challenge was keeping each rating, voltage class, nameplate, accessory set and inspection file aligned while moving 31 units through production together.

For the project team, production volume was only part of the risk. Configuration control mattered just as much: three specifications had to move quickly without mixing documentation, labels or final inspection records.

Winley treated the order as three controlled batches inside one plan. Engineering reviewed the drawings, nameplate data, voltage classes and accessory requirements for each batch first, then production moved in parallel across active-part assembly, internal wiring, tank assembly and accessory installation.

The 2550 kVA and 3750 kVA units were managed with their own voltage configurations and nameplate data. The 3750 kVA batch used a 480Y/277 V secondary side, while project accessories across the batches included bayonet fuses, current-limiting fuses, oil level gauges, oil temperature gauges, pressure relief devices, drain valves with sampler ports, tap changers and loadbreak switch arrangements.

Engineering layout for the customized 3750 kVA pad-mounted transformer

Compliance was built into the project from the start. The transformers were built to ANSI C57.12.34 for 60 Hz outdoor pad-mounted service, with ONAN cooling and mineral-oil insulation.

Winley Electric's three-phase pad-mounted transformer product line is UL/cUL Listed under UL File No. E536138. The listed product family covers 45 kVA to 7000 kVA, which gives North American buyers one platform for different distribution requirements.

Labels, engineering documents and factory files were prepared with the information North American project teams normally check before approval.

Nameplates for 2550 kVA and 3750 kVA units, including ANSI C57.12.34 and UL Listed markings.

UL/cUL Listed product line for Winley Electric three-phase pad-mounted transformers.

Production was arranged across active-part work, internal compartment preparation and final assembly. This kept repeat work efficient while each batch stayed tied to its own drawings, labels and inspection route.

Internal compartment views from project units, including high-voltage and low-voltage sections.

Core-and-coil and active-part work moving through batch production.

Production and workshop testing details before final release.

The factory test package covered winding resistance, insulation resistance, voltage ratio error, no-load loss, load loss, short-circuit impedance, induced voltage withstand testing, separate source voltage withstand testing, pressure integrity testing and insulating-oil tests.

The 2550 kVA, 12.87/0.48 kV units were tested as 60 Hz, ONAN-cooled transformers with a YNd1 vector group. The 3750 kVA units were tested as 60 Hz, ONAN-cooled transformers with a Dyn1 vector group.

Insulating oil was checked through dissolved gas analysis and dielectric breakdown voltage testing with reference to IEEE C57.104-2019. The release files gave the customer the technical record needed before shipment.

Factory test report for a 3750 kVA unit, including model data, ANSI C57.12.34, electrical test values and qualified results.

After final inspection, the transformers were export packed and loaded into multiple containers for shipment to North America. The loading process was documented to support customer review and project delivery traceability.

Each packaged transformer was carefully positioned and secured for long-distance transportation. For heavy electrical equipment, reliable packing and loading are not just logistics steps, but part of the complete delivery quality control process.

Packaged transformers loaded into export containers.

Container loading and securing details before shipment.

The takeaway for buyers is practical: one supplier managed several ratings and voltage classes under a single plan. Engineering confirmation, batch production, factory testing, UL/cUL documentation and export loading were completed together, giving the customer a project-ready transformer package instead of separate production lots.

For North American projects that require pad-mounted transformers with different capacities and voltage classes, this delivery gives a clear reference for Winley's batch production control, customization work, standards alignment and export shipment coordination.