Main frame for a wind turbine
The disclosure relates to a support structure of a wind turbine, in particular a main frame. An object is to develop an ideal load distribution and stiffness distribution of the main frame with a least possible use of material. The main frame is intended optimally to fulfill the requirements with respect to the operating and extreme loads and the stiffness for the given space conditions inside the nacelle. The main frame has a top, bottom, front and rear side, and includes a circumferential annular wall between the bottom and the top side. The main frame includes two lateral portions of the wall that extend between the front side and the rear side of the main frame. Additionally included are two lateral flanges on the top side of the main frame, a plurality of arms being arranged inside the wall. The arms are connected to the wall via a box profile.
1. A main frame for a wind turbine comprising:
a main frame body having a top side, a bottom side, a front side and a rear side;
said main frame body including a circumferential annular wall between said bottom side and said top side;
said circumferential annular wall including two lateral portions extending between said front side of said main frame body and said rear side of said main frame body;
two lateral flanges on said top side of said main frame body;
a plurality of arms arranged inside said circumferential annular wall;
a box profile;
said plurality of arms being connected to said circumferential annular wall via said box profile;
said plurality of arms including at least four arms;
said at least four arms including two arms connected to said box profile and said circumferential annular wall as a first symmetrical pair at said rear side;
said two arms of said first symmetrical pair defining an angle V;
said at least four arms including a further two arms connected to said box profile and said circumferential annular wall as a second symmetrical pair at said front side of said main frame body; and,
said two arms of said second symmetrical pair defining an angle U.
2. The main frame of claim 1 , wherein:
said two arms of said second symmetrical pair end directly at said front side; or,
said two arms of said second symmetrical pair extend beyond said circumferential annular wall and each end at corresponding ones of said two lateral flanges.
3. The main frame of claim 1 , wherein said at least four arms each have a collar formed thereon inwardly, outwardly or on both sides, on said top side or said bottom side.
4. The main frame of claim 1 , wherein said angle (V) between said two arms of said first symmetrical pair and said angle (U) between said two arms of said second symmetrical pair are determined in dependence on a length and a width of said main frame body.
5. The main frame of claim 1 , wherein said box profile is arranged in a centered manner in relation to said main frame.
6. The main frame of claim 1 , wherein:
said main frame body defines a center thereof; and,
said box profile is arranged at said center.
7. The main frame of claim 1 , wherein said box profile has a rectangular shape.
8. The main frame of claim 1 , wherein said box profile has a trapezoidal shape tapering towards said rear side or towards said front side of said main frame body.
9. The main frame of claim 1 , wherein:
said box profile has an open or closed construction and has two limbs of equal length;
said box profile has a first basic side and a second basic side;
said two limbs each have a first end facing said rear side of said main frame and a second end facing said front side of said main frame;
said first ends of said two limbs being connected to said first basic side and said second ends of said two limbs being connected to said second basic side; and,
said two limbs, said first basic side and said second basic side each having a respective length adapted to the main frame with respect to load bearing and stiffness, width and length.
10. The main frame of claim 9 , wherein said first basic side and said second basic side are equal in length.
11. The main frame of claim 9 , wherein one of said first basic side and said second basic side is shorter than the other.
12. The main frame of claim 9 , wherein:
said box profile includes at least one box profile wall extending at least one of transversely and longitudinally; and,
said box profile has further interior sub-divisions between said two limbs and said first basic side and said second basic side, as a result of said at least one box profile wall.
13. The main frame of claim 1 , wherein said bottom side of the main frame body has a circular, partly closed, contour that is curved spherically in a direction of said top side.
14. The main frame of claim 1 , wherein said circumferential annular wall defines an elliptical cutout in said top side at said front side and at said rear side.
15. The main frame of claim 3 , wherein said top side of said main frame body is provided with a concave curvature in a longitudinal direction, said concave curvature determining a configuration both of said box profile and of said at least four arms with said collars formed thereon.
16. The main frame of claim 1 , wherein the main frame is made via at least one of welding and casting.