Winding overhang support of an electrical machine
The winding overhang of the rotor of an electrical machine is subject to strong centrifugal forces during operation, especially when the machines run at high speed. The winding overhang support prevents the production of relative movements between the winding overhang and the rotor base. These movements result in strong mechanical stresses on the winding bars. The winding overhang support includes an inner ring and an outer ring between which the winding bars are arranged in the region of the winding overhang, the outer ring being shrunk on the inner ring and both the outer ring and the inner ring being interspaced from the lamination stack.
1. An end winding support for a rotor in an electrical machine, where the rotor includes a lamination stack in which winding bars are distributed around the circumference of the stack, and end windings of the winding bars extend beyond an axial end of the lamination stack, the end winding support comprising:
an outer ring and an inner ring, wherein the end windings are arranged between the outer ring and the inner ring along a direction parallel to a rotational axis of the rotor;
a shrink fitted joint between the outer ring and the end winding, and
an assembly formed by the outer ring, the end windings and the inner ring, wherein the assembly is attached to the motor,
wherein both the outer ring and the inner ring are spaced from the lamination stack so that the assembly can move in a radial direction with respect to the stack.
2. The end winding according to claim 1 further comprising a spacer having a height in cross section at least as high as the height in cross section of each of the winding bars and the spacer is between two of the winding bars that are adjacent each other in a circumferential direction.
3. The end winding support according to claim 2 , wherein the spacer includes a hollow profile.
4. The end winding support according to claim 1 further comprising an insulation layer arranged in radial direction between the inner ring and at least one of the winding bars.
5. The end winding support according to claim 1 further comprising an insulation layer arranged in radial direction between the outer ring and at least one of the winding bars.
6. The end winding support according to claims 1 wherein the winding bars include a bottom bar and a top bar, and a spacer between the bottom bar and top bar at the end winding portion of the bars, wherein the spacer has a height in cross section at least as high as the height in cross section of the bottom bar or the top bar at the end windings portion.
7. The end winding support according to claim 6 further comprising an insulation layer between the bottom bar and top bar.
8. The end winding support according to claim 1 further comprising a retaining device abutting the inner ring and engaging the inner ring to suppress axial movement of the end winding.
9. The end winding support according to claim 1 further comprising a hollow spacer between two of the end windings adjacent each other, wherein a cooling passage extends through the spacer.
10. A method to install an end winding support on a rotor including slots are distributed in an annular array around the circumference of a lamination stack and the slots extend parallel to a rotational axis of the lamination stack, wherein the method comprises:
inserting winding bars into the slots of the lamination stack, wherein end windings of the winding bars extend axially from an axial end of each of the slots;
mounting an inner ring onto the lamination stack after inserting the winding bars, and
shrink fitting an outer ring onto the end windings, wherein the outer ring, end windings and inner ring form an assembly attached to the rotor in which the end windings are between the outer ring and the inner ring along a direction parallel to a rotational axis of the rotor, and the assembly moves in a radial direction with respect to the lamination stack.
11. The method according to claim 10 further comprising arranging a spacer between two of the end windings adjacent each other.
12. The method according to claim 10 inserting an insulation layer between at least one of the inner ring and the end windings, between the end windings, and between the end windings and the outer ring.
13. The method according to claim 10 wherein the insertion of the winding bars includes inserting a first layer of winding bars in the slots and a second layer in the slots before the step of shrinking the outer ring on the end windings.
14. The method according to claim 11 wherein the insertion of the spacer between the end windings is performed before the step of shrinking the outer ring on the end windings.
15. The method of claim 13 further comprising inserting an insulation layer into the slots after inserting the first layer and before inserting the second layer, such that the insulation layer is sandwiched between the first layer and the second layer.
16. The method according to claim 10 further comprising attaching a retaining device to the inner ring and the lamination stack, wherein the retaining device suppresses axial displacement of the end windings.