Patent ID: 8344576

Claim:
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.