750kVA 3 Phase Underground Transformer 13.8kV to 208Y/120V ANSI/IEEE Standards

Engineered for high-density commercial sites and utility underground distribution networks, this 750kVA three-phase loop-feed transformer provides a reliable step-down solution from 13,800GrdY/7,920V to a grounded 208GrdY/120V secondary system. Copper windings, a five-legged silicon-steel core, a corrosion-resistant 304L stainless-steel NEMA 3R enclosure, and fluid-immersed ONAN cooling support efficient, fan-free operation and dependable long-term service. The unit complies with ANSI C57.12.24 and meets DOE 2016 efficiency requirements.

Its loop-feed configuration features six 15kV-class 200A dead-front bushings, providing flexible incoming and outgoing primary cable connections for sectionalized underground feeders. With a full-load secondary current of 2,081.9A, the transformer can serve concentrated 208V three-phase equipment together with 120V lighting, receptacle, and control loads from one compact distribution point—making it a strong fit for commercial developments, institutional facilities, and utility distribution projects.

• 2,081.9A Massive Low-Voltage Capacity
  Delivers up to 2,081.9A on the 208Y/120V secondary side from a single compact 750kVA footprint, handling high-density 208V three-phase motors alongside 120V building operational loads effortlessly.
• Advanced Loop-Feed Architecture
  Features six 15kV-class 200A dead-front bushings for primary connections, allowing smooth integration, maintenance, and flexible power rerouting within underground feeder networks.
• Optimized Grounded-Wye System
  Converts 13,800GrdY/7,920V to 208Y/120V seamlessly, offering stable three-phase power and single-phase line-to-neutral power with robust safety grounding.
• Heavy-Duty 304L Stainless-Steel Tank
  Constructed with a 304L stainless-steel NEMA 3R enclosure, guaranteeing superior resistance against harsh weather, moisture, corrosion, and extreme outdoor environments.
• 100% Copper Windings & Five-Legged Core
  High-grade HV/LV copper windings combined with a specialized 5-legged silicon-steel core ensure lower electrical losses, improved structural strength, and outstanding performance under unbalanced loads.
• Integrated Protection & Switching Array
  Equipped with 3 two-position loadbreak switches, bayonet fuses, and current-limiting fuses to form an airtight, fully integrated primary protection system.

   

   

• High-voltage bushings for safe and flexible loop-feed cable connections.

• Low-voltage terminals provide secure, high-current connection points for distribution system.

• The oil drain valve allows convenient insulating-oil draining and sampling.

SGS On-Site Inspection

Technical drawings

• Six 15kV-Class 200A Dead-Front HV Bushings — Provide protected incoming and outgoing primary cable connection points for the loop-feed circuit.
• Three Two-Position Loadbreak Switches — Allow each primary phase path to be switched between operating positions.
• Bayonet Fuses and Current-Limiting Fuses — Provide coordinated transformer overcurrent and fault protection.
• Five-Position Off-Circuit Tap Changer — Adjusts the primary ratio from 13,110V to 14,490V with the transformer de-energized.
• Four 8-Hole NEMA Secondary Spades — Provide high-current connection surfaces for the 208Y/120V secondary conductors.
• Temperature, Oil-Level and Vacuum-Pressure Indicators — Provide direct visual checks of key operating conditions.
• Pressure Relief Valve, Oil Fill Plug and Drain Valve with Sampler — Support pressure protection, oil filling, draining and oil sampling.
• Ground Pads, Ground Blade, Parking Stands and Lifting Lugs — Support grounding, cable handling, parking of disconnected elbows and transformer lifting.

 

A: Winley delivers standard three-phase pad-mounted transformers with a 4–6 weeks production time after technical approval. We provide a detailed production schedule and real-time manufacturing photos to help track progress.

A: We offer a flexible MOQ of just 1 unit. Complete inquiries are quoted within 1–2 days with 24/7 support. Leveraging our extensive North American project experience, we ensure highly cost-effective and reliable solutions.

A: Yes, We accept OEM and ODM. Winley three-phase pad-mounted transformers are available in standard ratings from 45–5000kVA (and maximum capability up to 10MVA), with HV systems up to 36 kV. We can customize electrical parameters, structure, fluid, protection, switches, gauges, tank and paint according to customer drawings, with the capability to integrate components from brands like Qualitrol, Eaton Cooper, and MR.

A: Yes. Our full range of products are UL/cUL-certified under UL File No. E536138, designed strictly in compliance with ANSI/IEEE, CSA, DOE, and NEMA requirements to meet grid connection and regulatory standards.

A: We deliver a complete compliance package: approval drawings, datasheets, routine test reports, UL/cUL certs, DOE 2016 docs, and operation manuals. We also back your project with lifetime documentation support.

A: Winley ensures quality through 4 annual unannounced UL audits and strict ISO 9001 process management with dedicated QC oversight. Prior to delivery, every unit undergoes comprehensive routine testing, including Winding Resistance, Turns Ratio, Polarity and Phase Relation, and No-Load Loss and Excitation Current tests. We also fully support Factory Acceptance Testing (FAT) and third-party inspections (SGS).

A: 24 months from B/L. During the warranty period, If there are any accessory problems, just provide photos of damaged accessory, then we will provide free service. According to the number of products, we will provide easily damaged accessories for free. We can also provide technical support if you need.