Electric motor rotor

1. A rotor assembly for an electrical induction motor, the rotor assembly comprising:

an axially stacked lamination core;

a plurality of rotor bars; and

an annular restraining ring element wherein:

said axially stacked lamination core contains a plurality of sets of laminations;

each lamination of said axially stacked lamination core containing a plurality of slots for receiving and retaining a corresponding plurality of said rotor bars in said lamination slots;

said sets of laminations comprise a first and second set of laminations each having a first outside diameter dimension, and a third set of laminations located centrally between said first and second sets of laminations in said axial stack and said third set of laminations having a second outside diameter dimension, wherein said first outside diameter dimension is greater than said second outside diameter dimension; and

said annular restraining ring element has an inner diameter dimension substantially equal to said second outside diameter dimension, a radial thickness dimension no greater than the difference between said first and second outer diameter dimensions, and surrounds said third set of said laminations to restrict outward movement of said rotor bars in said slots.

2. A rotor assembly as in claim 1 , wherein each of said lamination slots in said first and second sets of laminations substantially surround a portion of said rotor bars and said annular restraining ring element restricts the movement of said rotor bars against the outer portions of said lamination slots during high speed rotation of said rotor.

3. A rotor assembly for an electrical induction motor, comprising:

an axially stacked lamination core;

a plurality of rotor bars; and

and an annular restraining ring element wherein

said axially stacked lamination core contains a plurality of sets of laminations;

each lamination of said axially stacked lamination core contains a plurality of slots for receiving and retaining a corresponding plurality of said rotor bars in said lamination slots;

said sets of laminations comprise a first and a second set of laminations each having a first outside diameter dimension, and a third set of laminations located centrally between said first and second sets of laminations in said axial stack and said third set of laminations having a second outside diameter dimension;

said first outside diameter dimension is greater than said second outside diameter dimension;

said annular restraining ring element has an inner surface in contact with said rotor bars and an outer diameter dimension that is less than or equal to said first outside diameter dimension; and

said annular restraining ring element surrounds said third set of said laminations to restrict outward movement of said rotor bars in said slots.

4. A rotor assembly as in claim 3 , wherein said slots in said third set of laminations that retain said rotor bars each have an opening on the outer radial edge of the corresponding lamination to allow a portion of the rotor bar surface to be in contact with said annular restraining ring element.

5. A rotor assembly for an induction motor, the rotor comprising:

a first set of laminations having an outside diameter equal to a first diameter;

a second set of laminations having an outside diameter substantially equal to the first diameter;

a third set of laminations having an outside diameter equal to a second diameter with the second diameter being less than the first diameter wherein the lamination sets are aligned axially with the third set of laminations located between the first and second sets of laminations;

a plurality of rotor bars, the first, second, and third sets of lamination define openings into which the rotor bars are inserted; and

an annular restraining ring placed over the third set of laminations with an outer diameter of the annular restraining ring being substantially equal to the first diameter.

6. The rotor assembly of claim 5 wherein an inner diameter of the annular restraining ring is substantially equal to the second diameter.

7. The rotor assembly of claim 5 wherein the outside diameter of the first and second sets of laminations substantially equals the first diameter proximate the third set of laminations and a smaller diameter distal from the third set of laminations, the assembly further comprising:

containment rings over the first and second sets of laminations over the portion of the first and second set of laminations with the smaller diameter.

8. The rotor assembly of claim 5 wherein the first, second, and third sets of laminations defining a central opening, the assembly further comprising:

a shaft inserted into the central opening.

9. The rotor assembly of claim 5 wherein the first, second, and third sets of laminations defining a central opening, the assembly further comprising:

a shaft; and

a stiffener sleeve placed over the shaft with the assembled shaft and stiffener sleeve inserted into the central opening in the laminations.

10. The rotor assembly of claim 5 , further comprising:

a first balance ring having an end ring extension with the first balance ring adjacent the first plurality of laminations; and

a second balance ring having an end ring extension with the second balance ring adjacent the second plurality of laminations.

11. The rotor assembly of claim 10 , further comprising:

a first containment ring on the end ring extension associated with the first balance ring; and

a second containment ring on the end ring extension associated with the second balance ring.

12. A rotor of an electric machine, comprising:

a first plurality of laminations arranged axially;

a second plurality of laminations arranged axially;

a third plurality of laminations arranged axially with the third plurality of laminations located between the first and second pluralities of laminations wherein a plurality of longitudinal slots are defined in the first, second, and third pluralities of laminations; and the third plurality of laminations has a smaller outside diameter than the first and second pluralities of laminations;

a plurality of rotor bars inserted into the slots defined in the laminations;

a first balance ring having an end ring extension with the first balance ring adjacent the first plurality of laminations;

a second balance ring having an end ring extension with the second balance ring adjacent the second plurality of laminations;

a first containment ring on the end ring extension associated with the first balance ring;

a second containment ring on the end ring extension associated with the second balance ring; and

an annular restraining ring placed on an outside surface of the third plurality of laminations.

13. The rotor assembly of claim 12 wherein the first, second, and third sets of laminations defining a central opening, the assembly further comprising:

a shaft inserted into the central opening.

14. The rotor assembly of claim 12 wherein the first, second, and third sets of laminations defining a central opening, the assembly further comprising:

a shaft; and

a stiffener sleeve placed over the shaft with the assembled shaft and stiffener sleeve inserted into the central opening in the laminations.

15. The rotor assembly of claim 12 wherein

the first and second balance rings define a plurality of apertures; and

the plurality of apertures in the first and second balance rings engage with the rotor bars.