The primary and secondary windings of the transformers are made of aluminium or electrolytic copper with enamelled insulation, Nomex or fibreglass based on the size of the conductor and on the insulation voltage. The choice of the winding is determined by the voltage and currents involved, by the mechanical and thermal stresses and by the specific customer requests.

For power transformers, the windings are made disk-type with windings suitable for the voltages and currents involved. For higher currents, windings with transposed cable or other specifically designed technical solutions are applied.

For the higher voltages, all the construction measures are adopted to uniform the electric field and to distribute the capacity on the windings to protect them from overvoltages of various origins, impulsive phenomena and other factors.