Shaft for a wind turbine

A main shaft for a wind turbine axially extending along a rotation axis, the main shaft comprising:

• a first piece axially extending along the rotation axis,
• at least a second piece axially extending along the rotation axis, the second piece being axially adjacent to the first piece,
• a plurality of connections for fixing the second piece to the first piece,
• wherein the first piece and second piece are not part of a wind rotor of the wind turbine, and are not part of a generator assembly of the wind turbine,
• wherein the plurality of connections are applied to at least one of a first flange of the first piece and a second flange of the second piece, wherein each of the first flange and the second flange have a through hole for extending at least one of the plurality of connections therethrough, said plurality of connections terminating within a circumferential wall of the respective first or second piece, and
• wherein one of the first flange and the second flange extends from the circumferential wall of the respective first piece or second piece radially outward with respect to the rotation axis and the other of the first flange and the second flange extends from a circumferential wall of the respective first piece or second piece radially inward with respect to the rotation axis.

A method for manufacturing a main shaft for a wind turbine axially extending along a rotation axis, the method comprising:

• manufacturing a first axially extended piece of the main shaft,
• manufacturing at least a second axially extended piece of the main shaft,
• wherein the first axially extended piece of the main shaft and the at least a second axially extended piece of the main shaft are not part of a wind rotor of the wind turbine, and are not part of a generator assembly of the wind turbine,
• fixing the second piece to the first piece through a plurality of connections in such a way that the second piece is axially adjacent to the first piece along the rotation axis,
• wherein the plurality of connections are applied to at least one of a first flange of the first piece and a second flange of the second piece,
• extending the plurality of connections through a through hole in each of the first flange and the second flange,
• terminating each of said plurality of connections within a circumferential wall of the respective first or second piece, and
• wherein one of the first flange and the second flange extends from the circumferential wall of the respective first piece or second piece radially outward with respect to the rotation axis and the other of the first flange and the second flange extends from a circumferential wall of the respective first piece or second piece radially inward with respect to the rotation axis.

A method for manufacturing a main shaft for a wind turbine axially extending along a rotation axis, the method comprising:

• manufacturing at least a third axially extended piece of the main shaft,
• fixing the third piece to a second piece through a plurality of connections in such a way that the third piece is axially adjacent to the second piece,
• fixing a first piece to the second piece, and
• wherein the first and the third piece of the main shaft are forged, while the second, in-between, piece is cast.

A wind turbine including a main shaft rotatable around a rotation axis, the main shaft comprising:

• a first piece axially extending along the rotation axis;
• at least a second piece axially extending along the rotation axis, the second piece being axially adjacent to the first piece, wherein the first piece and second piece are not part of a wind rotor of the wind turbine, and are not part of a generator assembly of the wind turbine;
• a first plurality of connections for fixing the second piece to the first piece;
• a second plurality of connections for fixing the second piece to the first piece;
• and
• a hollow inside,
• wherein the first plurality of connections and second plurality of connections are applied to at least one of a first flange of the first piece and a second flange of the second piece, wherein each of the first flange and the second flange have a through hole for extending at least one of the first plurality of connections and second plurality of connections therethrough, said first plurality of connections and second plurality of connections terminating within a circumferential wall of the respective first or second piece,
• wherein one of the first flange and the second flange extends from the circumferential wall of the respective first piece or second piece radially outward with respect to the rotation axis and the other of the first flange and the second flange extends from a circumferential wall of the respective first piece or second piece radially inward with respect to the rotation axis, and
• wherein the first plurality of connections extend into the hollow inside of the main shaft and the second plurality of connections are outside of the hollow inside of the main shaft.

A wind turbine including a main shaft rotatable around a rotation axis, the main shaft comprising:

• a first piece axially extending along the rotation axis;
• a second piece axially extending along the rotation axis, the second piece being axially adjacent to the first piece;
• a third piece axially extending along the rotation axis, the third piece being axially adjacent to the second piece;
• and
• a plurality of connections for fixing the third piece to the second piece,
• wherein the first piece and the third piece of the main shaft are forged, and the second, in between piece, is cast.