Patent ID: 7719153

Claim:
A brushless electric machine comprising: a stator; a rotor having an axis of rotation, the rotor being spaced from the stator to define a primary air gap that receives an AC flux from the stator, the rotor having PM pole portions alternating in polarity around a circumference of the rotor; at least a first source of field excitation flux positioned across at least one of the primary air gap or a secondary air gap from the rotor so as to induce a DC flux in the rotor which increases a resulting flux in the primary air gap; and wherein portions of PM material are positioned to form boundaries that separate PM pole portions of alternating north polarity and south polarity that are spaced apart around a circumference of the rotor, for conveying the DC flux to or from the primary air gap and for inhibiting flux from leaking from said pole portions prior to reaching the primary air gap; further comprising reluctance poles of ferromagnetic material that are positioned in spaces between the PM pole portions of alternating north polarity and south polarity, to produce reluctance torque in the rotor in response to AC flux in the primary air gap; wherein said PM pole portions further comprise pole portions of one polarity having enlarged flux paths in relation to flux paths for pole portions of an opposite polarity, said enlarged flux paths communicating with a core of the rotor so as to increase torque produced by the electric machine; and wherein at least one source of field excitation is positioned across a secondary air gap from the rotor so as to induce a DC flux in the rotor in an axial direction and then through the PM pole portions to the primary air gap which increases a resulting flux in the primary air gap when said direct current is of a first polarity and which reduces the resulting flux in the primary air gap when said direct current is of a second polarity opposite said first polarity.