Patent ID: 8115434

Claim:
An electric machine comprising: a first energy source; a second energy source; a stator, wherein the stator comprises: a first set of windings comprising AC field windings that are coupled to the first energy source; and a second set of windings comprising DC field windings that are coupled to the second energy source; a rotor; and a controller coupled to the first and second energy sources and configured to: control the first energy source to supply a first current to the first set of windings; control the second energy source to supply a second current to the second set of windings; detect an angular position of the rotor; detect the first current on the first set of windings; detect the second current on the second set of windings; determine an optimum phase shift angle of the first current relative to the second current that causes a corresponding maximum amount of torque to be generated on the rotor from the supplied first and second currents, the optimum phase shift angle of the first current being determined based on the angular position of the rotor, the detected first current, and the detected second current; and control the first energy source based on the optimum phase shift angle to modify the first current supplied to the first set of windings.