25 July 2019


Developed to insulate low voltage windings in distribution transformers, TUF-Flex® is a thin paper that replaces thicker papers. It combines excellent mechanical strength with electrical characteristics and aging behavior.

Using the highest quality raw materials, TUF-Flex® is manufactured following design processes that achieve the optimal electrical characteristics. The paper is produced on multi-ply machines that guarantee pinhole-free paper.

TUF-Flex® has a nitrogen content of 1.3 – 2.6 % and is upgraded to a 120 °C class paper. It is coated with B-stage epoxy in a diamond pattern which allows a high short circuit strength.

The greatest advantage of TUF-Flex® is its outstanding mechanical properties. Thanks to its 20 % elongation in the machine direction, it can absorb a high proportion of mechanical energy. In addition, TUF-Flex® has a low thickness which makes it extremely tear-resistant. It is this low thickness, or the area weight of 63 g/m2 or 86 g/m2, which leads to several advantages:

  • Lower construction volume of the coil in radial direction. This leads to direct conductor savings by reducing the
    mean turn length, even at a high voltage.
  • Shrinking the coil, with thinner low voltage winding layer insulation and lower dimensional tolerance, allows a redesign of the core size. This results in material savings and reduction of non-load loss in the operation of the transformer.
  • Cellulose insulation is a thermal barrier. Thinner insulation leads to a more efficient transfer of thermal energy and cooling of the coil. The entire system can be designed in a more compact manner, resulting in savings of tank-size and the amount of oil required.
  • A thin insulation made of TUF-Flex® dries and is impregnated easier. This results in cost savings, in terms of time and energy, during the manufacturing process.

Weidmann’s experienced team can advise you on how you can achieve the maximum savings. Contact us now.