A permanent magnet rotor assembly includes a cylindrically shaped shaft having an outer surface, a plurality of permanent magnets constituting portions of annular segments and an outer retaining cylindrical sleeve surrounding the plurality of permanent magnets. The assembly further includes a cylindrical magnet housing mounted on the cylindrically shaped shaft for supporting the plurality of permanent magnets. The cylindrical magnet housing is formed of a magnetic material. The retaining cylindrical sleeve is preloaded by a resultant interference fit IF2 defined by the following formula IF2=−ØY+√{square root over (((ØY+IF1)^2+ØY^2−ØX^2))}, where ΦY is an external diameter of the plurality of permanent magnets, ΦX is an internal diameter of the cylindrical magnet housing, and IF1 is a primary interference fit between an external diameter of the cylindrically shaped shaft and the internal diameter of the cylindrical magnet housing.