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Distribution Transformers

Based on its accumulated technology and extensive supply record, Hyosung Heavy Industries provides stable transformer solutions to key industries such as the semiconductor, automobile, steelmaking, and petrochemical industries. We provide customized products to suit various uses and customer requirements.

Our oil-immersed transformers are available with a maximum voltage of 77kV and a power rating from 100kVA to 80MVA. Our exceptional quality is backed by the fact that we have shipped over 150,000 units to date. Committed to developing and manufacturing competitive, high-efficiency, eco-friendly transformers, we respond to the needs of global customers as a true transformer industry leader.

Cast-resin transformers are customizable up to a maximum voltage of 36kV and a maximum power rating of 30MVA. Their safety and low-noise capacity ensure semi-permanent use. They are suitable for locations with installation restrictions, where fire safety is essential, and where high reliability, eco-friendliness, and resistance to harsh environment are required.

Oil-Immersed Transformers

The oil-immersed transformers of Hyosung Heavy Industries are utilized in key industries such as the semiconductor, automobile, and petrochemical industries. Their high reliability has been recognized by customers throughout the world.

Features and Benefits

We offer oil-immersed transformer solutions based on superior technology.

  • Excellent Design Technology

    • We have secured high reliability through insulation design using electric and magnetic field analysis technology, optimal cooling structure design, and aseismic design.
    • Our solutions are economical and highly efficient with computer-aided optimized design.
  • Easy Inspection and Maintenance

    • We have realized miniaturization and lightness through compact design.
    • We have reduced maintenance costs for customers through careful selection and use of highly reliable parts.
  • Higher Short-circuit Strength

    • Even in the event of a short circuit, our solutions have high resistance to electromechanical force, external shock, and abnormal vibration as a result of their design and production processes, which are based on continuous research and rigorous testing.
  • Smart Transformer

    • With 60 years of accumulated expertise and technology, it is possible to connect transformers to a new-concept prevention and diagnosis system.
    • Real-time data transmission of partial discharge, transformer oil deterioration, OLTC monitoring, transformer oil temperature, and cooling fan operation status to diagnose device status and determine inspection cycles.
  • Green Technology

    • We offer eco-friendly, customer-optimized solutions based on low-loss technology.
    • We are the leader in low-noise technology and eco-friendly transformers.

Product Classification

Discover which oil-immersed transformers are appropriate for your use environment.

  • Corrugated Radiator Type

  • Panel Radiator Type

  • Conservator Type

  • OLTC Type

  • Hermetical Type


Discover oil-immersed transformer solutions customized for multiple industries.

  • Distribution substations

  • Power plants

  • Petrochemical plants

  • Automobile

  • Steelmaking

  • Semiconductor and other industries

Oil-Immersed Transformers

Discover oil-immersed transformers suitable for your field of application.

  • 01

    STATCOM transformers

    • Utilizing high-capacity inverter technology, grids are managed at high speed and with precision.
    • It is designed and manufactured to be minimally impacted by harmonics and DC current inrush caused by high-capacity inverters.
    • There are numerous advantages, including enhanced grid stability, increased transmission capacity, enhanced power quality, and decreased transmission costs.
  • 02 Eco-friendly

    Eco-friendly transformers

    • It is eco-friendly as it is insulated with vegetable oil.
    • Due to the high flash point and fire point of transformer oil, the risk of fire is minimal (stable up to 300°C).
  • 03

    Scott transformers

    • It is utilized to convert three-phase power to two-phase power and vice versa.
    • It is utilized to prevent voltage unbalance in three-phase power, such as when supplying large single-phase loads (e.g. electric railways, electric furnaces) or emergency backup generators or single-phase loads in three-phase power.
    • To obtain a single phase from three phases, a Scott connection is formed by two single phases, the primary and T.
  • 04

    Furnace transformers

    • It is a transformer designed and manufactured with large-current characteristics in mind for electric furnace systems used primarily in steelmaking facilities.
    • Adopting a core-type transformer that is resistant to internal impulses generated by the furnace is advantageous against large currents due to its resistance to these impulses.
    • Manufactured with the electric field analysis technology of 765kV transformers, it ensures exceptional dielectric strength.
  • 05

    Rectifier transformers

    • This is a specialized industrial transformer designed to provide power to a diode or thyristor rectifier circuit (AC power → DC power).
    • It is of superior quality and is resistant to harmonics and load fluctuations.
    • In fusion power plants, it is also used as a transformer to supply DC current to superconducting coils.
  • 06

    Grounding transformers

    • Through impedance or ground resistance, it is used to limit ground faults for a specified time.
    • Typically, it is constructed as a zigzag winding, but it can also be constructed as a delta-wye winding.

Cast-resin transformers

As the first company in Korea to successfully develop cast-resin transformers, Hyosung Heavy Industries supplies high-efficiency, low-noise, low-loss transformers using the finest grain-oriented silicon steel sheet.

Our cast-resin transformers satisfy the needs of a wide range of customers
by analyzing quality issues caused by communication and electronic device-inherent harmonics, earthquakes, lightning strikes, and surges.

Features and Benefits

We offer cast-resin transformers solutions based on superior technology.

  • Reliability

    • Routine testing based on various international standards
    • Type testing such as a lightning shock withstand voltage test
    • Special tests such as noise measurements
    • Direct pressure test conducted under the same environmental conditions as the field site
  • Safety (Certificates)

    • High-temperature accelerated degradation test (KERI)
    • Aseismic structure: Magnitude 8.0 (MMI)
    • Quality/safety/environmental management systems (ISO 9001/14001)
    • Various international certificates (e.g. CESI, KEMA, ABS)
  • Miniaturization and Light Weight (Compact Size)

    • We have realized miniaturization and weight reduction through the use of insulators with outstanding insulation performance and heat resistance.
  • Low Loss & Noise

    • Low-loss and low-noise performance made possible by low-loss silicon steel plate, coil miniaturization, and optimum design.
  • Easy Inspection and Maintenance (Maintenance Free)

    • Due to the simple structure and excellent moisture resistance, insulation performance does not degrade, making inspection and maintenance simple.
  • Environmentally Safe

    • Product with a high recyclability and no environmental pollutants (e.g. oil and gas spills)
  • Excellent Fire Resistance

    • No risk of fire or explosion caused by electric arc due to self-extinguishing properties of epoxy resin, the main insulator.
    • Using Class H (180°C) insulation instead of our standard insulation increases thermal life expectancy by over threefold.
  • Higher Short-circuit Strength

    • Cast-resin transformers windings are molded with epoxy resin under a high vacuum, resulting in high resistance to electromechanical force, external shock, and abnormal vibration caused by a short circuit.
  • Excellent Moisture Resistance

    • Long-term storage has little effect on the insulating performance of epoxy resin-molded windings that have been exposed to moisture or contamination.

Applications and Types

Introducing various cast-resin transformers used for specialized purposes.


  • Where high-efficiency products are required due to high power consumption
  • Where eco-friendliness and environmental resistance are required
  • Where fire safety is essential (fire resistance)
  • Where high reliability is required

We have acquired C2 (crack resistance), E2 (moisture resistance), and F1 (fire resistance) certifications through specialized tests.

Seismic transformer

Zigzag transformer

OLTC transformer

Excitation transformer

Auto transformer

Self-extinguishing transformer


Our track records speak for ourselves.

  • Republic of Korea

    Oil-Filled Transformers (22.9–6.6kV 40/45MVA), Molded Transformers (6.6–0.44kV 3,000kVA), and more for Samsung Electronics

    • Semiconductor field
  • Republic of Korea

    Doosan Enerbility, 8MW Offshore Wind Power System

    • Oil-Filled Transformers (22.9–0.69kV 10MVA) (applied with eco-friendly transformer oil)
    • Molded Transformers (300kVA)
  • United States

    Major Investor Owned Utilities

    • Oil-Filled Transformers (67–12.5kV 15/20/25MVA) and more
  • Qatar

    Ph-9, Ph-10, Ph-12, Lusail, Ph-13 Project

    • Oil-Filled Transformers (66–11kV 32/40MVA)
    • Kahramaa
  • Oman

    Duqm Refinery Project

    • Oil-Filled Transformers (33–11.5kV 40/50MVA) and more
    • Application of eco-friendly transformer oil
  • Republic of Korea

    Jeju Environmental Resource Recycling Center

    • Molded Transformers (22.0–6.6kV 21/25MVA) and more
    • Jeju Environmental Resource Recycling Center


We adhere to global standards and maintain an environment of the highest quality.

View all certifications
  • RSP

  • FILK

  • KERI


  • ISO9001

  • ISO14001

  • ISO45001



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