An electric machine including a stator having a plurality of stator windings configured for generating a magnetic field and a rotor configured for rotating within the stator according to a torque induced by the magnetic field. The rotor includes a plurality of electrically independent rotor winding sets wrapped around each of a plurality of circumferentially spaced rotor protrusions. The electric machine further includes a power transfer circuit operable for independently controlling electrical excitation of the rotor winding sets. The electric machine further includes a cooling system for dissipating heat way from the rotor winding sets.