Top 5 manufacturers of converter transformers
Lists with top x products / brands / holiday destinations / restaurants / hotels etc are extremely popular. Today we would like to present a list of top 5 manufacturers of converter transformers. As every such list, the ranking is always somewhat subjective or personal. Our top 5 list is provided in alphabetic order. Each manufacturer has own specific strengths and limitations.
ETD Transformatory (Czech Republic)
The company was founded in 1921 in Pilsen (Czech Republic) and just last year celebrated its 100th anniversary. For most of its history it was part of the Skoda industrial holding in that time Czechoslovakia. Initially, the company was manufacturing first equipment using license of foreign companies, such as Schneider Electric. Soon, Skoda started its own construction. It was Czechoslovakia and particularly the Skoda factory where the “star” and “delta” designation of winding connections was introduced. After World War II the IEC organization adopted this designation as international one due to its understandable nature. Over the decades the brand gained excellent reputation in export countries. Skoda was a traditional supplier for the Czechoslovak market. However, most of the production was made for export.
In early 1990s the traditional markets of Skoda company fell apart. It was necessary for Skoda to transform and adapt to the new market conditions. The transformer business became part of Skoda Energo. Several years later the transformer factory was sold out of Skoda. They act since many years under the name ETD and are still entitled to use the brand
Skoda if required by customer.
Nowadays the company is a trusted manufacturer of medium and large power transformers and reactors for modern power grid.
The production capability covers:
- Rated power up to approx. 420 MVA
- Voltage class up to 400 kV
ETD’s focus is not just the mainstream but also special designs, such as complex converter duty transformers.
The company has its own certified test field that can also be rent to third party customers. All the research and development, manufacturing and testing is still done in Pilsen where the history started. The designs are modern and innovative and yet “traditional” in terms of high quality and excellent reliability. ETD products work in demanding applications such as generator step-up transformers in large thermal power plants. Recent years showed a solid growth in the segment of converter transformers.
The designers of ETD, backed by capable R&D team, accept challenging requirements in the areas where other manufacturers often decline the inquiry. An example is a very demanding 75 MVA/110 kV 24-pulse transformer with additional filter (tertiary) winding. Documentation is on an excellent level, both in tender stage and in project execution. In-house test field provides infrastructure for thorough testing.
Manufacturer’s homepage: https://etd-transformers.com/
Hitachi Energy (Finland)
For decades ABB used to be the largest transformer manufacturer in the world referring to the installed base. In 2019 it was announced that the power grid business of ABB will be sold to Hitachi. Since fall 2021 the company operates under the name Hitachi Energy as part of Hitachi group.
The transformer business of Hitachi Energy includes large network of transformer factories. Each factory typically focuses on a specific market segment. Generally, dry type and liquid immersed transformers are not manufactured at the same location. As the capabilities of each factory significantly differ, we need to be more specific. For special transformer designs incl. converter transformers the factory in Vaasa, Finland is the center of competence. This factory produces premium quality and meets highest demands. The designers have vast experience in converter transformers. In fact, the design of almost all transformer types for medium voltage VFDs of ABB was developed in Vaasa in close collaboration with the center of competence for medium voltage drives in Switzerland.
The company manufactures transformers for demanding applications such as installations on offshore platforms or even subsea solutions with IP68+ design. The factory is also very successful in developing and manufacturing transformers for wind turbine applications. The application areas are summarized here:
- Offshore applications
- Transformers for subsea installations
- Furnace transformers
- Rectifier transformers
- Ship propulsion
- Railway transformers
- Converter (VFD/VSD) transformers
The designers in Vaasa, Finland are ready to accept almost any kind of technical challenges. We shall highlight their extreme precision and accuracy, specially when comparing the calculated values with measured ones during factory testing. The manufacturer is on the approved vendor list for some of the most demanding customers. In the converter transformers segment the manufacturer covers solutions for all types of VFDs (voltage source inverters, load-commutated inverters, cyclo-converters etc).
Factory capability:
- Rated power up to approx. 63 MVA
- Voltage class up to 170 kV
- Multi-winding transformers up to 72-pulse configuration
Manufacturer’s homepage: https://www.hitachienergy.com
Brochure about VFD transformers: Link
Koncar D&ST (Croatia)
Koncar D&ST (Distribution and Special Transformers) is a transformer manufacturer located in Zagreb, the capital of Croatia. Also Koncar was established in the year 1921 in Zagreb, Croatia. The original name was “Elektra”. In the same year 1921 the company became part of Siemens group. Since 1945 it belongs to Rade Koncar. It is known under the name Koncar – D&ST since the year 1991 when the company was reorganized. As the name says, the company focuses on two production lines:
1) Small and medium distribution transformers
- Up to approx. 5 MVA and 36 kV
- Both oil filled and dry type
2) Special transformers with large portion of them being transformers for converter applications. Other applications are e.g. traction transformers or earthing transformers.
- Power rating goes up to 63 MVA
- Voltage class up to 170 kV
Majority of the production is exported worldwide (over 80%).
The company has considerable installed base of converter transformers and experienced crew of talented engineers.
Manufacturer’s homepage: https://koncar-dst.hr/en/
Specialtrasfo (Italy)
Specialtrasfo is a transformer manufacturer located in the vicinity of Milano, Italy. The company focuses on special transformer designs and their dedication is reflected even in the name of the brand. Their traditional production are converter transformers, especially for the oil & gas industry. The manufacturer can provide tailor made solutions and comply with demanding customer specifications. Specialtrasfo has significant market share in Middle East and Africa and is very experienced with transformer designs for higher ambient temperatures. The company is certified according to applicable ISO standards. Moreover, the transformers can be certified by independent bodies such as UL, CSA, ABS, DNV etc. The transformers are built according to customer requirements and are suitable even for harsh conditons such as seismic zone, corrosive environment or environment with high ambient temperature.
- Converter transformers
- Up to 110 MVA / 175 kV
- Multi-winding transformers up to 36-pulse configuration
- Solutions for hazardous area
- Furnace transformers
- Up to 150 MVA of capacity and 100 kA load current
- Rectifier transformers
- Special units with DC current up to 150 kA
Transformers made by Specialtrasfo work together with VFDs from leading drive manufacturers in many installations across the globe.
Manufacturer’s homepage: https://specialtrasfo.com/
Trasfor (Switzerland)
Trasfor is a manufacturer of dry type transformers and reactors, based in Molinazzo, Switzerland, close to the Italian border. The company belongs to the Hitachi Energy group (former ABB Power Grids). The blend of Italian engineering genuity and Swiss precision makes their products unique and renowned.
The manufacturer an offer both VPI and cast resin technology [2]. Trasfor developed specific cooling system well suitable for VFD applications with additional harmonic losses.
Trasfor’s designers almost always find a solution for your particular requirements. And the solution is not an “experiment” but something that will work for years.
The company has huge installed base of converter transformers. They deliver dry type VFD transformers for many of the renowned VFD manufacturers and end users:
- External transformers
- Integrated transformers [3]
Factory capability covers units up to:
- Rated power up to approx. 25 MVA
- Voltage class 36 kV
- Multi-winding transformers with 15 or more secondary windings
- Transformers for virtually all types of VFDs
- Various cooling solutions (AN, AF, AFAF, AFWF)
- Indoor and outdoor installations
Their R&D also focuses on medium frequency applications up to 400 Hz. Solutions from Trasfor are suitable also for special applications such as traction transformers or offshore installations.
For our rental transformer service we also rely on products from Trasfor.
Moreover, Trasfor produces wide range of reactors. Those are used, among others, also in VFD applications:
- Reactors inside the VFD itself, for example
- DC reactors for LCI drives
- Clamp reactors and dv/dt chokes
- Filter reactors
- VFD output reactors
- VFD soft starter reactors
- Output reactors for motor friendliness
Manufacturer’s homepage: http://trasfor.com/
Other reputable regional and global manufacturers of converter transformers include:
- Celduc (France)
- Niagara Transformers (USA)
- SGB (Germany)
- Sönmez (Turkey)
- Tamini (Italy)
Summary
Above named companies are all well established transformer manufacturers that cover also special applications such as converter transformers for various applications (particularly for VFDs). The companies have impressive installed base, several decades of experience, are certified according applicable ISO standards and can provide transformers with certification from independent authorities. Each of those companies spends considerable amount of money in research and development, offers innovative solutions and provides good service capabilities throughout the lifecycle.
References
[1] Variable Speed Drive (VSD) Transformers, Hitachi Energy (former ABB), https://www.hitachienergy.com/offering/product-and-system/transformers/special-application-transformers/variable-speed-drive-vsd-transformers
[2] Dry transformer technology, https://mb-drive-services.com/dry-transformer-technology/
[3] Integrated versus external transformer, https://mb-drive-services.com/integrated-versus-external-transformer/
