Abstract: Single-phase transformer, including windings being wound around an axis and cast in resin forming a cast resin body, the cast resin winding body having an outer surface and a rectangular window formed therein with sides disposed in given planes, a wound core formed of tape material extended through the window, two flanges being cast with and integral with the cast resin winding body on opposite sides thereof and parallel to the winding axis and to the window, the flanges having outer edges, mutually parallel inner surfaces substantially disposed in the plane of the narrow sides of the window and grooves formed in the inner surfaces in the vicinity of and parallel to the outer edges, an encapsulation for the wound core being anchored in the grooves, and a grounded metallization layer formed on the outer surface of the cast resin winding body at least immediately adjacent to the wound core.