Switched reluctance machine with rotor excitation using permanent magnets

1. A switched reluctance machine comprising:

a stator that extends in an axial direction, the stator having a plurality of salient stator poles and corresponding phase windings to form at least three phases of the switched reluctance machine, wherein each phase winding is wound axially about the corresponding stator pole and the phase windings are adapted to carry electric current to generate magnetic flux; and

a rotor that extends in the axial direction, the rotor being disposed concentrically with and spaced radially from the stator, the rotor having a plurality of salient rotor poles arranged circumferentially on the rotor;

wherein at a given location of the stator and the rotor in the axial direction, the salient rotor poles and the salient stator poles extend radially towards one another along a radial plane that is perpendicular to the axial direction;

wherein each salient rotor pole has a first distal corner and a second distal corner that is spaced circumferentially from the first distal corner;

wherein each rotor pole comprises at least two permanent magnets defining an excitation source for that rotor pole, the at least two permanent magnets comprising a first permanent magnet positioned on the first distal corner and a second permanent magnet positioned on the second distal corner, wherein the first permanent magnet and the second permanent magnet have opposite polarity.

2. The switched reluctance machine of claim 1 , wherein the rotor is disposed outside the stator.

3. The switched reluctance machine of claim 1 , wherein the rotor is disposed inside the stator.

4. The switched reluctance machine of claim 1 , wherein the excitation source for a first rotor pole in the plurality of salient rotor poles has a first polarity configuration, the excitation source for a second rotor pole in the plurality of salient rotor poles that is circumferentially adjacent to the first rotor pole along the radial plane has a second polarity configuration, and the first polarity configuration is different from the second polarity configuration.

5. The switched reluctance machine of claim 1 , wherein the excitation source for a first rotor pole in the plurality of salient rotor poles has a first polarity configuration, the excitation source for a second rotor pole in the plurality of salient rotor poles that is circumferentially adjacent to the first rotor pole along the radial plane also has the first polarity configuration.

6. The switched reluctance machine of claim 1 , further comprising a controller configured to control current in each phase winding of the stator based on position of the rotor poles.

7. The switched reluctance machine of claim 1 , further comprising a controller coupled to the phase windings, wherein the controller is operable to monitor an inductance profile of each phase of the switched reluctance machine and to energize the stator phase having an increasing inductance profile.

8. The switched reluctance machine of claim 7 , further comprising a plurality of bidirectional converters corresponding to the at least three phases of the switched reluctance machine, each bidirectional converter coupling the controller to the phase windings in one phase of the at least three phases of the switched reluctance machine.

9. A method of manufacturing a switched reluctance machine, the method comprising:

providing a stator that extends in an axial direction, the stator having a plurality of salient stator poles and corresponding phase windings to form at least three phases of the switched reluctance machine, wherein each phase winding is wound axially about the corresponding stator pole and the phase windings are adapted to carry electric current to generate magnetic flux; and

disposing a rotor that extends in the axial direction concentrically with and radially spaced from the stator, the rotor having a plurality of salient rotor poles arranged circumferentially on the rotor and a plurality of permanent magnets, wherein at a given location of the stator and the rotor in the axial direction, the salient rotor poles and the salient stator poles extend radially towards one another along a radial plane that is perpendicular to the axial direction, and wherein each salient rotor pole has a first distal corner and a second distal corner that is spaced circumferentially from the first distal corner,

and

providing each rotor pole with at least two of the permanent magnets defining an excitation source for that rotor pole, the at least two permanent magnets including a first permanent magnet on the first distal corner and a second permanent magnet on the second distal corner, wherein the first permanent magnet and the second permanent magnet have opposite polarity.

10. The method of claim 9 , wherein the rotor is disposed outside the stator.

11. The method of claim 9 , wherein the rotor is disposed inside the stator.

12. The method of claim 9 , wherein the excitation source for a first rotor pole in the plurality of salient rotor poles is defined to have a first polarity configuration, the excitation source for a second rotor pole in the plurality of salient rotor poles that is circumferentially adjacent to the first rotor pole along the radial plane is defined to have a second polarity configuration, and the first polarity configuration is different from the second polarity configuration.

13. The method of claim 9 , wherein the excitation source for a first rotor pole in the plurality of salient rotor poles is defined to have a first polarity configuration, the excitation source for a second rotor pole in the plurality of salient rotor poles that is circumferentially adjacent to the first rotor pole along the radial plane is also defined to have the first polarity configuration.

14. The method of claim 9 , further comprising coupling a controller to each of the phase windings, wherein the controller is configured to control current in each phase winding of the stator based on position of the rotor poles.

15. The method of claim 9 , further comprising coupling a controller to each of the phase windings, wherein the controller is operable to monitor an inductance profile of each phase of the switched reluctance machine and to energize the stator phase having an increasing inductance profile.

16. The method of claim 15 , further comprising providing a plurality of bidirectional converters corresponding to the at least three phases of the switched reluctance machine, wherein each bidirectional converter is used to couple the controller to the phase windings in one phase of the at least three phases of the switched reluctance machine.