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High Power Transformers


Rex dry type power transformers are primarily designed for stepping down high voltages from transmission and distribution systems to utilize voltages in commercial and industrial, institutional or utility applications. They are ideally suited for both indoor and outdoor applications.

Dry type power transformers require minimal maintenance to provide many years of reliable trouble free service. Unlike liquid filled transformers which are cooled with oil or a fire resistant liquid dielectric, dry type units utilize only environmentally safe, CSA and UL recognized high temperature insulation systems. Every dry type design provides a safe and reliable power source which does not require fire proof vaults, catch basins or the venting of toxic gasses. These important safety factors allow the installation of dry type transformers inside buildings close to the load, which improves overall system regulation and reduces costly secondary line losses.

Rex Power Magnetics provides quality dry type power transformers up to 15 MVA at 34.5 kV and 150 kV BIL. A sampling of their applications are:

  • Power Distribution
  • Indoor or Outdoor Primary and Secondary Unit Substations
  • Grounding Transformers
  • Mining, Pulp and Paper Application
  • Corrosion Resistant Transformers for Marine Distribution and Power
  • Low Electromagnetic Field Emission Transformers For Hospital and Institutional Use
  • Traction Power Rectifier Transformers for Transit Systems
  • Motor Starting & Drive System Applications
  • High Harmonic and Intermittent Load Applications
  • Many Other Applications


  • Using Computer Aided Design (CAD) techniques and modern materials, Rex engineers have created a range of highly efficient transformers having long trouble-free life with reduced weight, size, and cost.
  • Ventilation openings in the enclosure are coordinated with the cooling ducts in the coils to ensure proper natural circulation of the cooling air for long life and minimum losses.
  • General-purpose ventilated steel enclosure, suitable for indoor locations. After fabrication, they are finished in ASA 61 grey powder coating, suitable for most industrial and commercial installations.
  • CSA certified, File No. LR34493.
  • UL listed, File No. E108255.
  • Transformers up to 75 kVA capacity may be readily hung on H-columns, walls , shelves or floor mounted to suit each installation. All units have lifting lugs, conduit KOs and a removable front cover for convenient access to terminals.
  • Transformers rated 112.5–300 kVA capacity are suitable for floor or platform mounting and complete with integral lifting lugs, a removable top, as well as front and rear panels for convenient access to the terminals.
  • Class 220 insulation used throughout range
  • Transformer terminations rated below 330 Amps are supplied with suitable hardware and lugs for cable connection. Terminations above 330 Amps are supplied with terminal pads only.
    Typical Configurations


The lifespan of the insulation is the main determinant in the life of the transformer. The working temperature of the transformer affects the life of the insulation. This temperature is a combination of the unit's temperature rise, the ambient temperature and the hot spot temperature.

Rex Power Magnetics Transformers are manufactured with class 220OC Insulation materials. Only high temperature resistant materials of the best quality are used including Nomex Aramid papers, Silicone or Polyester Coated Fiberglass, Nomex Sleeving, Glass Tapes and Polyester/Glass Duct Sticks.

Core Construction

Every Rex Power Transformer core is constructed from electrical grade, cold rolled grain oriented silicone steel of M5 grade or better. Grain oriented steel is utilized for its superior magnetic permeability, low hysteresis and eddy current losses. Steel is cut into individual laminations on automated cutting machines to ensure precision and consistency.

Core laminations are meticulously stacked on specially designed jig tables. The individual laminations of the core are then clamped together by structural grade steel core clamps. Once the core is complete, an epoxy coating is applied to guard against corrosion.

At Rex Power Magnetics, we construct our transformer cores with either rectangular or cruciform configuration. The core configuration is chosen to provide the most efficient unit with the best weight and dimension factors. Both configurations may utilize either the Butt & Lap stacking method or the Full Miter cut stacking method.

Standard Factory Testing

Every power transformer by Rex Power Magnetics receives the following standard production tests.

    • Resistance Measurement
    • Ratio test
    • Polarity and Phase Relation test
    • No-Load Loss and Excitation Current test
    • ULoad Loss Test
    • Impedance Test
    • Applied Potential Test
    • Induced Potential Test

Other Tests available as options:

  • Basic Impulse Insulation Level (BIL)
  • Temperature Rise Test
  • Partial Discharge Test (Corona)
  • Sound Level Test
  • RIV test
  • EMT test
  • Power Factor test

Optional Accessories

  • Provision for Future Fans or Fan Packages (ANF) completely installed with or without Control Power
  • Buss Co-ordination with primary and secondary switchgear
  • Dial (Analog) or Digital Thermometers to monitor winding temperatures
  • Neutral Ground Resistors (NGR)
  • Strip Heaters to avoid condensation when the transformer is not energized
  • Ground Fault Relays (GFR)
  • Anti-Vibration mounting to reduce transformer hum (sound level)
  • Provision for Seismic mounting or complete Seismic Snubbers and Restraints
  • Lighting Arrestors (LA) available in Distribution, Intermediate or Station Class
  • Provision for Buss Duct Entry
  • Fully Insulated Buss
  • Mimic Buss
  • Kirk-Key Interlock Systems

Typical Drawings of Medium Voltage High Power Transformersin Nema-1 Enclosure

Drawings of 150°C or 115°C Rise, Stubs Up, Max. 600V/10kV BIL on L.V.
BIL 10kV 30kV 45kV 60kV 95kV 125kV 150kV
Rating 1,200V 5,000V 8,700V 15,000V 18,000V 25,000V 34,500V
225kVA 225KVA-BIL10 225KVA-BIL30 225KVA-BIL45 225KVA-BIL60 225KVA-BIL95 Consult Eng. Consult Eng.
300kVA 300KVA-BIL10 300KVA-BIL30 300KVA-BIL45 300KVA-BIL60 300KVA-BIL95 Consult Eng. Consult Eng.
450kVA 450KVA-BIL10 450KVA-BIL30 450KVA-BIL45 450KVA-BIL60 450KVA-BIL95 450KVA-BIL125 450KVA-BIL150
500kVA 500KVA-BIL10 500KVA-BIL30 500KVA-BIL45 500KVA-BIL60 500KVA-BIL95 500KVA-BIL125 500KVA-BIL150
600kVA 600KVA-BIL10 600KVA-BIL30 600KVA-BIL45 600KVA-BIL60 600KVA-BIL95 600KVA-BIL125 600KVA-BIL150
750kVA 750KVA-BIL10 750KVA-BIL30 750KVA-BIL45 750KVA-BIL60 750KVA-BIL95 750KVA-BIL125 750KVA-BIL150
1000kVA 1000KVA-BIL10 1000KVA-BIL30 1000KVA-BIL45 1000KVA-BIL60 1000KVA-BIL95 1000KVA-BIL125 1000KVA-BIL150
1250kVA 1250KVA-BIL10 1250KVA-BIL30 1250KVA-BIL45 1250KVA-BIL60 1250KVA-BIL95 1250KVA-BIL125 1250KVA-BIL150
1500kVA 1500KVA-BIL10 1500KVA-BIL30 1500KVA-BIL45 1500KVA-BIL60 1500KVA-BIL95 1500KVA-BIL125 1500KVA-BIL150
1750kVA 1750KVA-BIL10 1750KVA-BIL30 1750KVA-BIL45 1750KVA-BIL60 1750KVA-BIL95 1750KVA-BIL125 1750KVA-BIL150
2000kVA 2000KVA-BIL10 2000KVA-BIL30 2000KVA-BIL45 2000KVA-BIL60 2000KVA-BIL95 2000KVA-BIL125 2000KVA-BIL150
2250kVA 2250KVA-BIL10 2250KVA-BIL30 2250KVA-BIL45 2250KVA-BIL60 2250KVA-BIL95 2250KVA-BIL125 2250KVA-BIL150
2500kVA 2500KVA-BIL10 2500KVA-BIL30 2500KVA-BIL45 2500KVA-BIL60 2500KVA-BIL95 2500KVA-BIL125 2500KVA-BIL150
3000kVA 3000KVA-BIL10 3000KVA-BIL30 3000KVA-BIL45 3000KVA-BIL60 3000KVA-BIL95 3000KVA-BIL125 3000KVA-BIL150
3500kVA Consult Eng. 3500KVA-BIL30 3500KVA-BIL45 3500KVA-BIL60 3500KVA-BIL95 3500KVA-BIL125 3500KVA-BIL150
3750kVA Consult Eng. 3750KVA-BIL30 3750KVA-BIL45 3750KVA-BIL60 3750KVA-BIL95 3750KVA-BIL125 3750KVA-BIL150
4000kVA Consult Eng. 4000KVA-BIL30 4000KVA-BIL45 4000KVA-BIL60 4000KVA-BIL95 4000KVA-BIL125 4000KVA-BIL150
4500kVA Consult Eng. 4500KVA-BIL30 4500KVA-BIL45 4500KVA-BIL60 4500KVA-BIL95 4500KVA-BIL125 4500KVA-BIL150
4750kVA Consult Eng. 4750KVA-BIL30 4750KVA-BIL45 4750KVA-BIL60 4750KVA-BIL95 4750KVA-BIL125 4750KVA-BIL150
5000kVA Consult Eng. 5000KVA-BIL30 5000KVA-BIL45 5000KVA-BIL60 5000KVA-BIL95 5000KVA-BIL125 5000KVA-BIL150

Typical Drawings of Medium Voltage High Power Transformersin Nema-3R Enclosure

Drawings of 150°C or 115°C Rise, Stubs Up, Max. 600V/10kV BIL on L.V.
BIL 10kV 30kV 45kV 60kV 95kV 125kV 150kV
Rating 1,200V 5,000V 8,700V 1,5000V 18,000V 25,000V 34,500V
225kVA 225KVA-BIL10-3R 225KVA-BIL30-3R 225KVA-BIL45-3R 225KVA-BIL60-3R 225KVA-BIL95-3R Consult Eng. Consult Eng.
300kVA 300KVA-BIL10-3R 300KVA-BIL30-3R 300KVA-BIL45-3R 300KVA-BIL60-3R 300KVA-BIL95-3R Consult Eng. Consult Eng.
450kVA 450KVA-BIL10-3R 450KVA-BIL30-3R 450KVA-BIL45-3R 450KVA-BIL60-3R 450KVA-BIL95-3R 450KVA-BIL125-3R Consult Eng.
500kVA 500KVA-BIL10-3R 500KVA-BIL30-3R 500KVA-BIL45-3R 500KVA-BIL60-3R 500KVA-BIL95-3R 500KVA-BIL125-3R 500KVA-BIL150-3R
600kVA 600KVA-BIL10-3R 600KVA-BIL30-3R 600KVA-BIL45-3R 600KVA-BIL60-3R 600KVA-BIL95-3R 600KVA-BIL125-3R 600KVA-BIL150-3R
750kVA 750KVA-BIL10-3R 750KVA-BIL30-3R 750KVA-BIL45-3R 750KVA-BIL60-3R 750KVA-BIL95-3R 750KVA-BIL125-3R 750KVA-BIL150-3R
1000kVA 1000KVA-BIL10-3R 1000KVA-BIL30-3R 1000KVA-BIL45-3R 1000KVA-BIL60-3R 1000KVA-BIL95-3R 1000KVA-BIL125-3R 1000KVA-BIL150-3R
1250kVA 1250KVA-BIL10-3R 1250KVA-BIL30-3R 1250KVA-BIL45-3R 1250KVA-BIL60-3R 1250KVA-BIL95-3R 1250KVA-BIL125-3R 1250KVA-BIL150-3R
1500kVA 1500KVA-BIL10-3R 1500KVA-BIL30-3R 1500KVA-BIL45-3R 1500KVA-BIL60-3R 1500KVA-BIL95-3R 1500KVA-BIL125-3R 1500KVA-BIL150-3R
1750kVA 1750KVA-BIL10-3R 1750KVA-BIL30-3R 1750KVA-BIL45-3R 1750KVA-BIL60-3R 1750KVA-BIL95-3R 1750KVA-BIL125-3R 1750KVA-BIL150-3R
2000kVA 2000KVA-BIL10-3R 2000KVA-BIL30-3R 2000KVA-BIL45-3R 2000KVA-BIL60-3R 2000KVA-BIL95-3R 2000KVA-BIL125-3R 2000KVA-BIL150-3R
2250kVA 2250KVA-BIL10-3R 2250KVA-BIL30-3R 2250KVA-BIL45-3R 2250KVA-BIL60-3R 2250KVA-BIL95-3R 2250KVA-BIL125-3R 2250KVA-BIL150-3R
2500kVA 2500KVA-BIL10-3R 200KVA-BIL30-3R 2500KVA-BIL45-3R 2500KVA-BIL60-3R 2500KVA-BIL95-3R 2500KVA-BIL125-3R 2500KVA-BIL150-3R
3000kVA 3000KVA-BIL10-3R 3000KVA-BIL30-3R 3000KVA-BIL45-3R 3000KVA-BIL60-3R 3000KVA-BIL95-3R 3000KVA-BIL125-3R 3000KVA-BIL150-3R
3500kVA Consult Eng. 3500KVA-BIL30-3R 3500KVA-BIL45-3R 3500KVA-BIL60-3R 3500KVA-BIL95-3R 3500KVA-BIL125-3R 3500KVA-BIL150-3R
3750kVA Consult Eng. 3750KVA-BIL30-3R 3750KVA-BIL45-3R 3750KVA-BIL60-3R 3750KVA-BIL95-3R 3750KVA-BIL125-3R 3750KVA-BIL150-3R
4000kVA Consult Eng. 4000KVA-BIL30-3R 4000KVA-BIL45-3R 4000KVA-BIL60-3R 4000KVA-BIL95-3R 4000KVA-BIL125-3R 4000KVA-BIL150-3R
4500v Consult Eng. 4500KVA-BIL30-3R 4500KVA-BIL45-3R 4500KVA-BIL60-3R 4500KVA-BIL95-3R 4500KVA-BIL125-3R 4500KVA-BIL150-3R
4750kVA Consult Eng. 4750KVA-BIL30-3R 4750KVA-BIL45-3R 4750KVA-BIL60-3R 4750KVA-BIL95-3R 4750KVA-BIL125-3R 4750KVA-BIL150-3R
5000kVA Consult Eng. 5000KVA-BIL30-3R 5000KVA-BIL45-3R 5000KVA-BIL60-3R 5000KVA-BIL95-3R 5000KVA-BIL125-3R 5000KVA-BIL150-3R

Rex Power Magnetics Technical Capability

We have the engineering capability to design, manufacture and test all standard and specialty dry type transformers, related magnetic products, and power transformers rated up to 15,000KVA and 150kv BIL. All Rex Power Magnetic Products are CSA certified and most are UL listed including Dry Type Power Transformers.