R.E. Uptegraff Manufacturing

Innovation · Quality · Reliability · Since 1925


Innovation · Quality · Reliability · Since 1925


Structural features


The magnetic cores of Uptegraff Power Transformers are made of high-permeability, grain-oriented steel. All cores utilize step-lapped laminations for minimum loss, sound level, and exciting current.


The general coil construction is elliptical in shape (layer wound). Round (circular) or disc wound coil construction is available upon request. Both copper and/or aluminum windings are available. The Uptegraff Company pioneered the use of aluminum conductor in transfomer windings, with eminently successful results.


Like most manufacturers, Uptegraff uses thermally up-graded kraft paper insulation in liquid-filled units. A “B” stage epoxy is applied to the insulation in a diamond pattern in order to assume minimum coil distortion under short circuit. Class “H” (Aramid) insulation is also available upon request.

Dielectric Fluids

Uptegraff liquid immersed transformers can be provided with acid-refined, filtered and deaerated mineral oil (either Type I or Type II in accordance with ASTM Standard D 3487); natural ester fluids; less-flammable silicone or non-flammable fluid alternatives. All liquid immersed transformers can be used indoors or outdoors as long as they are installed in accordance with the provisions set forth in the NEC and/or any local codes which may take precedence or be more restrictive. All Uptegraff liquid immersed transformers are shipped with dry nitrogen in the gas space above the liquid.


The standard transformer tank or enclosure is made of reinforced ASTM A-36 carbon steel plate. As an option for corrosive environments, the tank can be provided using stainless steel or copper bearing steel plate.

For liquid filled transformers, a variety of radiator configurations can be provided depending on cost, size, and site conditions. They include tubular style, corrugated style (standard is 2 1/4″ centers and can be varied to 5″ centers for ease of cleaning and/or painting), panel or plate type, or heavy plate type.




All standard ANSI tests are made on every Uptegraff transformer, using the appropriate standard procedures. In addition, and probably more pertinent to qualify the transformer for service, are such production tests as dielectric(s), power factor, sound level and insulation resistance tests.


Completed transformers, subassemblies and accessories are inspected by a Quality Control Department responsible only to top management. An inspection report is made for every transformer.


Check with factory for current lead times. We ship generally by motor-freight and complete carrier and routing information is provided. International Shipments are handled as requested.


Express warranty is typical and applies to workmanship, design and materials for a period of 30 months after receipt of the transformer or 2 years following energization, whichever occurs first. Other warranty provisions may be made upon request. Uptegraff is concerned that a customer receive good service and reasonable consideration no matter how long the equipment has been in service.

Repair - Refurbish - Modify

Repairing other makes of transformers provides Uptegraff customers with totally reliable and less expensive means of replacing failed units. The usual procedure involves, first, a ‘post-mortem’ examination for the cause of failure. The original design is often modified to correct for weaknesses. Repaired transformers are subject to the same inspection and testing requirements applied to new transformers. Repaired equipment is provided with the same warranty as new units. Usually, the efficiency of the repaired transformer is better than that of the original.



Single phase, station service units up to 500 kVA, and 69 kV primary

Three phase, power distribution units, up to 2500 kVA, 69 kV primary

Zigzag grounding units, up to 14 MVA, 69 kV primary

Three phase, small power units, up to 15 MVA, 46 kV (12 MVA @ 69 kV)

Compartmental padmounted units (live and dead front) up to 12 MVA, 46 kV primary

Special duty transformers, including submersibles, induction furnace duty, rectifier duty (up to K=6), mobile duty, load tap changing units, phase-changing units, non-standard frequencies, units for hazardous locations



All units are manufactured to IEEE, ANSI, and NEMA standards.  As a custom manufacturer, pride is taken in maintaining strict adherence to customer specifications wherever possible.  Also, unique dimensional constraints and/or terminal locations are welcome.


  • Coil construction is offered in elliptical and circular layer, as well as circular disk.  Copper and aluminum windings are both offered.  Insulation is thermally-upgraded kraft paper with “B” stage thermosetting epoxy.
  • Cores can be offered in five-legged rectangular wound cores (up to 5000 kVA), as well as three- or four-legged step-lap mitered joint stacked style (rectangular or circular) in all kVA sizes.
  • Tanks are primarily manufactured with A36 carbon steel, but copper-bearing steel or stainless steel for corrosive environments can also be provided.  Standard radiators are mild steel.  Galvanized or stainless steel radiators can be offered as well.
  • Standard paint system is alkyd enamel.  Epoxy/polyurethane systems are also offered for corrosive areas.
  • Stock fluid is Type II (inhibited) mineral oil.  High-flame point liquids including Envirotemp® FR3™, Beta, and silicone, as well as oils produced specifically for low ambient temperatures      (to -60 deg. C), can also be supplied.
  • Testing is performed in accordance with the IEEE C57.12 series, including all routine tests, as well as temperature rise, impulse, power factor, sound level, and RIV testing.