Patent ID: 8159103

Claim:
A rotor ( 11 ) for a permanent magnet electric machine which includes a plurality of permanent magnets ( 13 ) located between the poles ( 15 ) of the electric machine and a rotor hub, wherein said rotor hub comprises an internal ferrule ( 21 ) and an intermediate ring ( 23 ) between the internal ferrule ( 21 ) and said magnets ( 13 ), with said intermediate ring ( 23 ) being made of an amagnetic material of minimum thickness which prevents flux losses and which outer surface in contact with magnets ( 13 ) has a curved form so that the magnets ( 13 ) are supported in straight lines ( 27 ) on said surface contacting just at a point C, and with the internal ferrule ( 21 ) being made of a metal material with sufficient thickness to resist, together with the intermediate ring ( 23 ), the mechanical stresses caused by rotor ( 11 ) operation.