Pole retention configuration for electric machine rotors
View Patent ↗A retention system in which rotor pole pieces are retained within complementarily shaped channels in a rotor hub, permanent magnets are secured between the pole pieces and within clamp members, and wedge-shaped pieces are used to apply positive locking forces along the axial length of each clamp member and of adjacent pole pieces. A curable resin preferably in disposed within gaps between the permanent magnets and the clamp members.
1. A rotor retention system, comprising:
a rotor hub having a plurality of axially extending channels configured to receive therein complementarily shaped portions of pole pieces and effective to retain the pole pieces therein against centrifugal forces;
a plurality of axially extending clamp members configured with lateral extensions which engage under pole-hub gaps between the pole pieces and the rotor hub, the clamp members also configured to contain therein complementarily shaped permanent magnets; and
for each permanent magnet, a pair of axially extending wedge-shaped base members configured to fit between the permanent magnet and the rotor hub, the wedge-shaped base members tapered to have inclined surfaces which engage against each other in sliding fashion, the wedge-shaped base members expanding laterally as thicker portions of the tapers abut and creating lateral forces that force the lateral extensions of the respective clamp member into the pole-hub gaps of adjacent pole pieces.
2. The rotor retention system of claim 1 , wherein the wedge-shaped base members are substantially trapezoidal in shape with the engaging surfaces skewed along the axial dimension of the machine.
3. The rotor retention system of claim 1 , wherein the wedge-shaped base members are non-magnetic.
4. The rotor retention system of claim 1 , wherein the clamp members are ferromagnetic.
5. The rotor retention system of claim 1 , wherein the axially extending channels in the rotor hub are substantially T-shaped in cross section.
6. The rotor retention system of claim 1 , wherein edges of the lateral extensions of the clamp members are tapered.
7. The rotor retention system of claim 1 , wherein the clamp members are substantially U-shaped in cross section.
8. The rotor retention system according to claim 1 , further comprising a curable fluid within gaps between the permanent magnets and their respective clamp members.
9. The rotor retention system according to claim 8 , wherein the curable fluid is sufficiently flexible when cured so as to be effective to protect the permanent magnets against mechanical damage.
10. The rotor retention system of claim 1 , wherein the rotor hub is made of a nonmagnetic material selected from the group consisting of stainless steel, high grade aluminum and composite materials.
11. The rotor retention assembly of claim 1 further comprising said pole pieces, said pole pieces being relatively highly permeable to magnetic fields.
12. The rotor retention assembly of claim 11 , wherein said pole pieces comprise ferromagnetic laminations.
13. The rotor retention assembly of claim 1 further comprising said permanent magnets, each permanent magnet comprising a magnetic material selected from the group consisting of ferrite, NdFeB, ceramic and Samarium-Cobalt.
14. A rotor assembly, comprising:
a shaft;
a rotor hub on the shaft;
a plurality of pole pieces;
a plurality of axially extending channels in the hub configured to receive therein complementarily shaped portions of the pole pieces and effective to retain the pole pieces therein against centrifugal forces;
a plurality of axially extending clamp members configured with lateral extensions which engage under pole-hub gaps between the pole pieces and the rotor hub;
a plurality of permanent magnets complementarily shaped to fit within the clamp members and retained therein; and
for each permanent magnet, a pair of axially extending wedge-shaped base members configured to fit between the permanent magnet and the rotor hub, the wedge-shaped base members tapered to have inclined surfaces which engage against each other in sliding fashion, the wedge-shaped base members expanding laterally as thicker portions of the tapers abut and creating lateral forces that force the lateral extensions of the respective clamp member into the pole-hub gaps of adjacent pole pieces.
15. The rotor assembly of claim 14 , wherein the pole pieces comprise ferromagnetic laminations.
16. The rotor assembly of claim 14 , wherein each permanent magnet comprises a magnetic material selected from the group consisting of ferrite, NdFeB, ceramic and Samarium-Cobalt.
17. The rotor assembly of claim 14 , wherein the rotor hub is made of a nonmagnetic material selected from the group consisting of stainless steel, high grade aluminum and composite materials.
18. The rotor assembly of claim 14 wherein the base wedge-shaped members are trapezoidal in shape.
19. The rotor assembly of claim 14 , wherein the base wedge-shaped members are triangular in shape.
20. An electric machine, comprising:
a shaft;
a rotor hub on the shaft;
a plurality of pole pieces;
a plurality of axially extending channels in the hub configured to receive therein complementarily shaped portions of the pole pieces and effective to retain the pole pieces therein against centrifugal forces;
a plurality of axially extending clamp members configured with lateral extensions which engage under pole-hub gaps between the pole pieces and the rotor hub;
a plurality of permanent magnets complementarily shaped to fit within the clamp members and retained therein; and
for each permanent magnet, a pair of axially extending wedge-shaped base members configured to fit between the permanent magnet and the rotor hub, the wedge-shaped base members tapered to have inclined surfaces which engage against each other in sliding fashion, the wedge-shaped base members expanding laterally as thicker portions of the tapers abut and creating lateral forces that force the lateral extensions of the respective clamp member into the pole-hub gaps of adjacent pole pieces.
21. The electric machine of claim 20 , wherein the pole pieces comprise ferromagnetic laminations.
22. The electric machine of claim 20 , wherein each permanent magnet comprises a magnetic material selected from the group consisting of ferrite, NdFeB, ceramic and Samarium-Cobalt.
23. The electric machine of claim 20 , wherein the rotor hub is made of a nonmagnetic material selected from the group consisting of stainless steel, high grade aluminum and composite materials.
24. The electric machine of claim 20 , wherein the base wedge-shaped members are trapezoidal in shape.
25. The electric machine of claim 20 , wherein the base wedge-shaped members are triangular in shape.
26. The electric machine of claim 20 , wherein the electric machine is a generator.
27. The electric machine of claim 20 , wherein the electric machine is a motor.
28. The electric machine of claim 20 , wherein the rotor hub is irremovably secured to the shaft.
29. The electric machine of claim 19 , further comprising a curable resin disposed in gaps between the permanent magnets and the clamp members.