The magnetic core is manufactured using high-permeability and low-loss grain-oriented steel sheets. The insulated surface of these sheets minimises losses due to stray currents.

The core components are assembled on special workbenches in order to prevent any deformation of the individual sheets, also assuring a perfect core alignment.

The joints are 45° step–lap type to minimise stray-flux losses and to prevent joint vibrations, which is the primary cause of noise. Non-hygroscopic paint covers sheet surfaces, protects the various sheared parts against oxidation and corrosion, and further contributes to noise reduction.