Oil filled Transformers

FDUEG boasts over 25 years of experience in design and production of oil filled transformer, both for low (LV) and medium voltages (MV). The production standard involves power ratings up to 10 MVA and insulation classes up to 36 kV. Solutions with different features can be realized as custom request.

The key driver for FDUEG design is performance. All liquid filled transformers made by FDUEG are perfectly compliant with all technical specifications proposed by the customer (being them regular or special), ensuring highest quality and functionality for the whole lifespan of the apparatus. Losses are kept under control and, if applicable, below the thresholds imposed by the most demanding standards, such as EU 548/14.

Oil-filled transformers: reliability in harsh environment with power rating up to 10 MVA and 36 kV voltage

Oil filled transformers feature protection boxes to house and contain their isolating fluid. Both single phase transformers and three phase transformers can therefore be installed in environments sporting harsh conditions or air pollution which may not be easily faced by dry type transformers.

These features contributed, through the years, in driving the choice for almost any substation transformer to be built as oil filled type.

The offered power transformers can be either sealed type or with a conservator and Buchholz relay, and, based upon their rated power, they can be cooled via elastic fin-type coolers or radiators. A liquid filled transformer box from FDUEG is available with a dedicate surface finish for environments where the chemical hazard is relevant, according to ISO 12944 standard. This offer includes paintings and treatments up to the compliance to the C5M cycle, able to ensure the functionality of power supplies in the most troublesome environments. These include marine areas, characterized by high salinity and moisture, or industrial plants.

Outdoor installation

Eco-friendly oil arrangement

Long lasting

Dielectric strength of transformer oil

Mineral oil is today’s most used insulating liquid for medium and high voltage transformers, due to its reliability in performance as dielectric fluid, heat disposal features and low viscosity at the usual working temperatures.

These properties, together with a regular maintenance and working conditions under control, contribute in making oil filled transformers really durable. The design procedure followed by FDUEG makes it possible to exploit the qualities of oil at their full potential, with an eye on mechanical stability of core and windings.

In case the impact on natural environment and the recyclability are particularly important, or for special applications upon customer’s request, the electrical insulating transformer oil can be substituted with an equivalent that is either silicone-, ester- or vegetable-based.

Oil filled transformer for special applications

The company, being a custom transformer manufacturer, is able to offer to its clients a wide range of options making full usage of the liquid insulation advantages. Among all transformer types, the oil filled ones are the best in terms of lifespan and reliability in difficult conditions: special, reinforced solutions for heavy industry applications, pump stations, oil rigs and similar usages grant safety and security for an installation where mechanical risks are relevant.

FDUEG can propose to its customers dedicated solutions with liquid insulation, to be used for other applications apart from the usual MV/LV distribution transformers. Typical products realized upon request comprehend transformers for converters and for rectifiers, where the design phase needs to keep in particular consideration the effects of current harmonics and carefully balance the secondary windings.

Another application for which the design needs to be particularly detailed is the realization of earthing transformer. These products are meant to serve systems whose power rating is important, as steelworks and heavy industry applications such as electric arc soldering, and must assure high reliability since they are fundamental in fault safety measures.

The experience of FDUEG has developed in particular with respect to design and manufacturing lab transformers, deputed to test electrical components as motors, breakers, contactors and other transformers. Products meant for dielectric strength tests, both in the lab and directly where the transformer operates, may reach considerable voltages while keeping small dimensions and a high degree of safety for the personnel.


Technical data

Distribution transformer Up to  3150 kVA Up to  36kV ONAN / ONAF
Power transformer Up to  10 MVA Up to  36kV ONAN / ONAF
Transformer for converters and rectifiers Up to  10 MVA Multi-winding

High harmonic content available

Earthing transformer Up to  10kA Up to  36kV ONAN / ONAF
Test facility transformer Up to  10kA Up to  52kV ONAN


Industrial electric power supply
Power Plants
Public, Medical and Commercial Buildings
Renewable Energies
Test Lab & Research Institutes


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