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The Large-capacity dry type transformer is a three-phase, cast resin insulated unit engineered for heavy indoor distribution duty. Fed at 2.4–34.5 kV and delivering 480/277V, 400/230V or 380/220V, it supports gigafactory production blocks, utility-scale renewable collection stations, iron and steel complexes, chemical processing trains and hyperscale campus backbones with a single indoor unit on each board.
Windings are cast under vacuum in epoxy resin with quartz filler, and the core is stacked from CRGO silicon steel laminations, optionally in amorphous alloy. Air circulation by AN, AN/AF or ANAF holds temperature rise inside Class F limits, and each 5000-7500 kVA dry type transformer leaves the works routine tested for partial discharge below 10 pC.
| Electrical | Rated Capacity | 5000-7500 kVA |
Rated Primary Voltage | 2.4–34.5 kV or customized | |
Secondary Voltage | 480/277V, 400/230V, 380/220V or customized | |
Frequency | 50/60Hz | |
Vector Group | Dyn11, Yyn0, Dyn5 or customized | |
H.V. Tap Changer | ±2×2.5% HV taps or customized | |
Efficiency | As IEEE, DoE 2016, GB or customized | |
Impedance Voltage | 1.1–5.75% | |
Cooling Method | AN, AN/AF, ANAF | |
Operation | Step Down & Step Up | |
| Physical & Standards | Standards/Certificate | IEEE, ISO, IEC, GB, CE, UL |
Application | Data Center, Power Distribution, Hospitals, Commercial Buildings, Hotels, indoor location | |
Total Weight | 25000 kg | |
Outline Dimensions（L×W×H） | 4800×2700×3200 mm | |
Altitude | ≤1,000m, 1000–2000m, 2000–3000m, >3000m | |
| Material | Winding Material | Aluminum / Copper |
Core Material | CRGO Silicon Steel / Amorphous Alloy | |
Color | Customized | |
Enclosure material | Mild Steel / Stainless Steel |
Located at the centre of the active part and stacked from cold rolled grain oriented silicon steel laminations to form a closed magnetic circuit. Step lap, 45° mitered joints, clamping frames and a single point ground hold no-load loss and audible noise to a minimum.
The winding closest to the core limb carries the secondary current at 480/277V, 400/230V or 380/220V. Foil or multi layer conductor in copper or aluminium distributes ampere turns evenly along the limb, which gives the low voltage winding high short circuit withstand strength.
Wound concentrically outside the low voltage winding and divided into layers separated by insulating cylinders and cooling ducts. Taps are brought out at the top for voltage adjustment, and the assembly is built to the specified Dyn11, Yyn0 or Dyn5 vector group.
Instead of transformer oil, the windings are encapsulated in epoxy resin cast under vacuum. The resin fills every turn and layer and gives dielectric strength, mechanical rigidity, moisture proofing and a self-extinguishing, flame retardant surface that adds no fuel to a fire.
Open vertical ducts between the resin cylinders and the core let air circulate freely by natural convection. Because the cooling medium is ambient air rather than a liquid, the insulation system stays dry and there is no oil to sample, filter, top up or replace.
PT100 or PTC sensors embedded in the windings feed a temperature controller that displays each phase and starts the forced air fans when a winding reaches its set point. Alarm and trip contacts let the transformer run at its AN or AN/AF rating as the load demands.
The active part is housed in a steel enclosure with louvered ventilation, fabricated in mild steel or stainless steel and finished in the specified colour. Removable panels give access for inspection and cable termination, and the enclosure keeps live parts out of reach in plant and public rooms.
Epoxy bushings or a cable termination box bring the 2.4–34.5 kV primary leads out of the enclosure. They provide the required creepage and clearance to ground, together with mechanical support for cable lugs or busbar, and carry clear phase identification and safety labelling.
Copper terminal pads on the secondary side take the 480/277V, 400/230V or 380/220V outgoing cable or busbar. Generously sized pads keep current density and temperature rise low, and neutral and earth terminals are brought out for the earthing arrangement required at site.
An off-circuit tap changer is fitted on the high voltage side with a normal ±2×2.5% range or a customer specified tap scheme. Links are set by hand while the unit is de-energized, so the secondary voltage can be corrected to match the actual supply at site.
Every dry-type transformer is tested before shipment against the applicable standard and the customer specification — from the first batch of incoming material to the routine test, including partial discharge, on the factory floor.
Dry-type quality begins with what we bring in. Every batch of silicon steel, copper or aluminium conductor, epoxy resin and insulating material is checked against approved specifications before it reaches the winding shop, with supplier qualification and traceability records kept for each shipment.
Progress tests are carried out at the key stages of dry-type manufacture — core stacking, winding, resin casting or vacuum pressure impregnation, and final assembly — to confirm that every large-capacity three-phase dry-type transformer meets its design and quality requirements before dispatch.
Before leaving the factory each transformer undergoes routine testing — conducted in accordance with IEC 60076-11 / GB 1094.11 (and IEEE C57.12.01 when specified) — covering insulation resistance, winding DC resistance, voltage ratio and vector group, no-load loss and current, load loss and short-circuit impedance, applied and induced voltage withstand, and partial discharge measurement on the cast resin winding.
A partial discharge level inside the 10 pC acceptance limit confirms that the resin encapsulation is free of voids and delamination. Once every test has passed, the unit is shipped with a factory test report and a certificate of conformity, so each delivered product meets its rated performance and safety specifications.
Large-capacity Dry Type Transformers are available with a range of configurable options to suit different electrical, thermal and environmental requirements. Customers can select the winding material, insulation class, cooling method and degree of enclosure protection according to their project conditions and the local installation code.
Copper or aluminium windings can be supplied, and the windings are encapsulated either by vacuum casting in epoxy resin or by vacuum pressure impregnation, depending on the dielectric strength required and the ambient conditions at site. Insulation class F or class H is selected to match the specified temperature rise and the expected load profile of the installation.
Cooling can be configured as air natural for quiet, lightly loaded duty, or air natural with forced air fans where extra capacity is needed during peak periods. Winding temperature sensors, a temperature controller and alarm and trip contacts are available as monitoring options, and enclosures in mild steel or stainless steel with the required degree of protection and finish colour keep the unit suited to both plant rooms and occupied buildings.
From data centers, hospitals and metro stations to commercial towers, hotels and industrial plants, the dry-type transformer can be configured to meet the required balance of fire safety, low noise, low loss and long maintenance free service life.
We ensure every three-phase dry-type transformer is safely packed, protected from moisture and ready for installation.
Secure Packaging: Cast resin windings and open terminals are the most exposed parts of a dry-type unit, so the transformer is mounted on a heavy duty skid or wooden pallet, braced with timber, banded with steel strapping and wrapped in stretch film to keep out moisture, dust and impact.
Moisture Protection: Dry-type insulation must stay dry, so every unit is sealed before it leaves the workshop and desiccant plus moisture indicators are added for long sea freight or humid destinations.
Complete Accessories: Temperature controllers, cooling fans, terminal hardware and documents are packed separately and itemized on the packing list, while factory fitted components are tested together with the transformer.
Reliable Transport: Road, rail, or sea shipping is arranged according to project requirements, with the unit braced and lashed so it cannot shift in transit.
Complete Documentation: Test reports, certificates, manuals, and shipping documents are provided.
Installation Support: Unpacking, installation, and commissioning guidance is available for smooth project delivery.
Dry-type transformers are cooled by air. AN (air natural) relies on convection through the cooling ducts; AN/AF or ANAF add fans that start at a set winding temperature to raise capacity during peak load. There is no oil pump, radiator or water circuit.
Under IEC 60076-11 the average winding temperature rise is limited to 100 K for Class F insulation and 125 K for Class H, measured at rated load. Staying inside those limits is what preserves the resin and gives a dry-type transformer its long service life.
Choose a dry-type transformer for indoor or occupied buildings where fire load and oil containment are restricted. Oil-immersed units still win outdoors and at the highest ratings on cost per kVA. Local fire codes often settle the question for you.
