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Specialtrasfo engineers and manufactures custom designed oil immersed special transformers for industrial and power applications. We offer customised maintenance and service solutions for transformers' and state-of-the-art machinery and equipments for testing laboratories.


In Specialtrasfo each transformer is designed as a new project and customized to comply with specific project requirements. The Specialtrasfo engineering team covers the complete design of a transformer: from the definition of core and coils to the tank and the supporting structures.

Transformer engineering begins from electromagnetic and thermal design of core and windings. This activity is performed by means of standardized calculation sheets developed by Specialtrasfo over the years. 2D and 3D Finite Element Method software tools are used for particular studies, such as: short-circuit impedances of phase-shifted multi-winding transformers, eddy current and stray losses calculation due to harmonics, hot-spots calculation and localization on windings and carpentry, mechanical stresses due to short-circuit, insulation assessment.

Transformer mechanical design is carried out using 3D software tools allowing dimensions optimization, mechanical stress evaluation and taking into account special external conditions (seismic, offshore).

Electromagnetic and mechanical designs are often developed in collaboration with “Politecnico di Milano” University in addition to other highly qualified international experts.
Each transformer is supplied with a set of basic documents describing its features and functionalities, such as layout drawings, connection diagrams, auxiliary circuit diagrams, cooling system diagrams, user’s manual.


We carry out winding construction internally based on our engineering team design; in Specialtrasfo we have one dedicated workshop for all kinds of windings: foil, helical, layers, disc. Paper-insulated flat conductors are typically used for HV windings. Continuously Transposed Conductors (CTC) are generally used for MV and LV windings with currents higher than 300 A and up to 2000 A for each conductor. CTC can be either paper-insulated for MV applications or without paper for LV high-current applications. Core and coils are assembled in a dedicated workshop.

Special care is taken to ensure proper insulation of the core to the supporting structures and solid grounding of any metallic component. Coils insertion, assembly and connections are made according to design drawings. Once the active part is completely assembled, a drying treatment is carried out before final tightening and tanking. Final treatment before oil filling is performed applying heating and vacuum to the transformer. The transformer external assembly is completed with the installation of coolers and accessories.

Factory testing is performed on all transformers in accordance to IEC or IEEE/ANSI standards. We use only high-quality materials and components. All of them (copper, electric steel, coolers, accessories) are procured from well-known long-standing reputable international suppliers.

Transformers are then prepared for dispatch, packed according to contractual obligations.
During the whole process intermediate test/check-points are performed before passing to the next production step according to the internal quality assurance procedures to assess the proper manufacturing stage.


Our firm has its roots in an historical Milan-based transformer company, founded in 1946 by the Pivi brothers. Since Pivi S.r.l. began its activity has always dealt with the engineering and manufacturing of custom-designed power transformers.

Throughout the decades we have gathered experience in all special applications of power transformers, becoming, in both dry-type and liquid-filled transformers, an internationally recognized premium supplier to all major customers.

In the mid eighties (1985) the firm name became Specialtrasfo and continued developing products, making the original business grow both organically and by acquisitions of niche-specialized transformer manufacturers.

Specialtrasfo has always been a family-owned business, carried forward by CEO Francesco Pagano since the year 2000.
As part of our culture we are committed to continuously improving the range and quality of our products, investing in human resources, technology, engineering and infrastructures.

In 2011 we completed our facility renewal and expansion, substantially increasing our yearly production capacity to more than 1500 MVA. We now have three state-of-the-art workshops for a total covered surface of above 4500 square meters dedicated to offices, winding construction, core & coils assembly and overall finishing and testing. In the last decade Specialtrasfo has focused mainly on custom-designed high quality liquidfilled transformers, especially but not limited to those dedicated to rectifier circuits with 8500 MVA total installed capacity, serving customers in more than 65 countries around the globe in the most extreme environmental conditions.


“In Specialtrasfo quality goes beyond certifications programs, it is the way to obtain state-of-the-art reliability and conduct business successfully. And success for us consists in our customers’ satisfaction.”