Method of manufacturing transformer windings embedded in casting resin

Method for manufacturing a transformer winding embedded in casting resin by winding coils, respectively by themselves and independently of one another for disposition thereof in tandem in axial direction of the winding;

• placing the wound coils in a substantially annular casting mold having an inner and an outer jacket, with respective impregnated corrugated mats of insulating material as spacers disposed between the inner jacket and the coils as well as between the coils and the outer jacket, the inner and the outer jackets being fixed between mold end walls at respective ends of the casting mold;
• disposing the casting mold containing the wound coils in an evacuated chamber and pouring casting resin into the casting mold through an axially parallel slot formed in the outer jacket thereof;
• and permitting the casting resin to harden at least partly in the mold at elevated temperature and at a pressure at least equal to atmospheric pressure;
• which comprises spreading the inner jacket of the casting mold in radial direction so as to permanently deform the inner spacer to a dimension at which the radical extent of the inner spacer is reduced, the inner jacket being formed with axially parallel edges at ends thereof overlapping in circumferential direction and slidable on one another during the deformation so as to spread the inner jacket in radial direction, fixing the coils of the winding on the inner spacer against movement in axial direction;
• and surrounding respective edges at the end of the inner and the outer jackets with an elastic layer at the inner face of the respective mold end walls.