Transformer core for a cut-and-stack type transformer and transformer including same

Electric transformer core of the cut-and-stack type, wherein it comprises two stacks or groups of stacks, each having a first thickness (ep1), the stacks each consisting of a single flat part or several identical flat parts isolated from each other, whose main cut directions are rectilinear and are either parallel or perpendicular to each other, the stacks or groups of stacks facing each other and having at least one residual or calibrated air gap (ε) with a maximum value of 10 mm between them, the flat parts being of at least one austenitic FeNi alloy containing Ni=30-80%, preferably Ni=40-60%, and at most 10%, preferably at most 2%, of alloying elements and impurities resulting from the preparation, the remainder being iron, the alloy having an acute cubic texture {100} <001>, of which at least 80% of the grains, preferably at least 95% of the grains, deviate by an angle (ω) equal to at most 200 with respect to the ideal orientation {100} <001>, the two main cutting directions of the flat pieces being substantially parallel to either the rolling direction (DL) or the transverse direction (DT) perpendicular to the rolling direction (DL), the crystallographic plane (100) deviating at most 20° from the rolling plane, preferably at most 100, better at most 50, and the axes [001] or [010] and respectively the rolling direction (DL) or the transverse direction (DT) deviating from an angle (α) at most equal to 200, preferably at most equal to 100, better not more than 50, the flat parts having magnetic losses in sinusoidal induction waves of the magnetic core, for a maximum induction of 1 T, less than 20 W/kg at 400 Hz, preferably less than 15 W/kg, and better, less than 10 W/kg, the apparent magnetostriction for a maximum induction of 1.2 T (λs1.2T) being less than 5 ppm, preferably less than 3 ppm, preferably 1 ppm, when the measurement is performed on an elongated rectangular sample, the field being applied in the direction of the long side of the sample and this direction being parallel to the lamination direction (DL), the apparent magnetostriction for a maximum induction of 1.2 T (λs1.2T) being less than 5 ppm, preferably less than 3 ppm, preferably less than 1 ppm, when the measurement is made on an elongated rectangular sample, the field being applied in the direction of the long side of the sample and this direction being parallel to the transverse direction (DT) perpendicular to the rolling direction (DL) and located in the rolling plane, and the apparent magnetostriction for a maximum induction of 1.2 T (λs1.2T) being less than 10 ppm, preferably less than 8 ppm, preferably less than 6 ppm, when the measurement is made on an elongated rectangular sample, the field being applied in the long direction of the sample and this direction being parallel to the intermediate direction at 450 of the rolling direction (DL) and the transverse direction (DT).