Arrangement to ensure an air gap in an electric machine

1. An arrangement to ensure an air gap in an electrical machine, comprising:

an electrical machine with a stator arrangement and a rotor arrangement, the rotor arrangement rotating around a longitudinal axis, wherein:

parts of the rotor arrangement interact with parts of the stator arrangement to generate electrical power,

an air gap is defined by a distance between the parts of the rotor arrangement and the parts of the stator arrangement,

the parts of the stator arrangement are opposite to the parts of the rotor arrangement along a certain length,

a cross section of the air gap changes along the certain length such that the air gap is not uniform in view to the referred certain length,

the stator arrangement comprises a lamination stack which is constructed to support at least one winding of a stator-coil,

the rotor arrangement comprises a plurality of permanent magnets,

the cross section of the air gap is configured by a change in a shape of the lamination stack along the certain length,

the stator arrangement and the rotor arrangement are connected via a single main bearing,

the stator arrangement comprises a stator support structure and a lamination stack,

the lamination stack is constructed to support the winding of the stator-coil,

the stator support structure comprises support elements for a two-sided support of the lamination stack, the support elements being ring-shaped and connected via the single main bearing to the rotor arrangement,

outer ends of the ring-shaped support elements are attached to a hollow cylindrical support element, and

the hollow cylindrical support element carries the ring-shaped lamination stack and the winding.

2. The arrangement according to claim 1 , wherein:

the lamination stack is constructed such that a size of the lamination stack varies along a length by a height,

a first side of the air gap is adjacent to a front endplate and a second side of the air gap is opposite to the first side,

the lamination stack shows at the first side a predefined first height in reference to the longitudinal axis,

the lamination stack shows at the second side a predefined second height, and

the second height is smaller than the first height.

3. The arrangement according to claim 1 , wherein:

the rotor arrangement comprises a front endplate and a cylinder element,

the front endplate is ring-shaped, while the cylinder element is hollow,

the cylinder element carries the permanent magnets which are mounted on the inside of the hollow cylinder element,

the permanent magnets are arranged opposite to the lamination stack and the supported winding,

the air gap is located between the permanent magnets and the supported windings of the stator-coil.

4. The arrangement according to claim 1 , wherein the electrical machine is a generator.

5. The arrangement according to claim 4 , wherein the generator comprises an outer-rotor and an inner stator, the rotor revolving around the stator.

6. The arrangement according to claim 4 , wherein:

the generator has a stationary shaft with a centre axis,

the stator arrangement is arranged on an outside of the stationary shaft,

the rotor arrangement is substantially arranged around the stator arrangement,

the rotor arrangement is supported on the stationary shaft by a single main bearing, and

the main bearing is located on a front side of the generator.

7. The arrangement according to claim 4 , wherein the generator is a direct-drive-generator, which is located in a wind-turbine.