Patent ID: 7466054

Claim:
A permanent magnet rotor assembly comprising: a non-magnetic cylindrical shaft having an axis of rotation and a generally cylindrical surface with an even number of recessed and overhung slots defining an even number of ribs therebetween; a plurality of generally C-shaped high magnetic permeability laminated stacks surrounding said ribs, each C-shaped laminated stack abutting overhung portions of the ribs; a plurality of permanent magnets positioned in each recessed slot, said magnets having spaced circumferential end edge faces abutting the C-shaped laminated stacks and said magnets having top and bottom faces, said magnets being magnetized with opposite poles at each circumferential end edge face and such that the poles abutting any C-shaped lamination stack are of identical polarity; a plurality of non-magnetic cradles for supporting the permanent magnets in the recessed slots, each cradle having top and bottom walls abutting the top and bottom faces of the permanent magnets and each cradle having axial end walls with circumferential edges of said axial end walls directly abutting overhung portions of the ribs, the total axial length of the top wall of the cradles in the axial direction being greater than the total axial length of the C-shaped lamination stacks and magnets permitting the C-shaped laminated stacks and magnets to fit between the end walls of the cradle, said magnets being secured against centrifugal force by the cradles bearing directly on the ribs; and a plurality of inserts filling the gaps between axially spaced C-shaped lamination stacks and circumferentially spaced non-magnetic cradles, said inserts being secured to the ribs by a dovetail tongue that fits within a dovetail groove provided along the length of each rib, said inserts engaging the adjacent cradles and having a circumferential surface that has the same radius of curvature of the top surface of the cradles.