Patent ID: 7514833

Claim:
A brushless electric machine, comprising: at least one stator assembly for receiving ac electrical power to provide a magnetic field; a rotor disposed within the magnetic field of the stator assembly and spaced from the stator to define a primary air gap relative to an axis of rotation for the rotor; wherein the rotor is disk-shaped and is spaced from the stator assembly along an axis of rotation for the rotor to form a first axial air gap; further comprising a second stator assembly disposed on an opposite side of the rotor from the at least one stator assembly and separated from the rotor by a second axial air gap; and wherein the disk-shaped rotor further comprises a nonmagnetic hub and a non-magnetic outer ring; wherein the rotor is provided with a plurality of permanent magnetic elements for coupling flux that is induced by the magnetic field of the stator assembly; and wherein the permanent magnetic elements are spaced apart and wherein reluctance poles of ferromagnetic material are positioned in spaces between the magnetic elements to couple additional flux induced by the magnetic field of the stator assembly, whereby a flux return path through ferromagnetic material is limited in the rotor to the reluctance poles; and wherein the permanent magnetic elements each have an outer cover of non-PM ferromagnetic material that covers a core of PM material and faces both the first stator assembly and the second stator assembly, the cover enhancing the torque-producing flux in the reluctance poles through the first stator assembly and the second stator assembly and short-circuiting any harmonic flux received from the first stator assembly and the second stator assembly.