Reluctance machine with auxiliary field excitations

• US 5,780,949 A
• Filed: 10/13/1997
• Issued: 07/14/1998
• Est. Priority Date: 01/29/1996
• Status: Expired due to Fees

• Current Assignee: Emerson Electric Company
• Original Assignee: Emerson Electric Company
• Inventors: Li, Yue
• Primary Examiner(s): Stephan, Steven L.
• Assistant Examiner(s): MULLINS, BURTON S
• Application Number:
  US08/953,830
• Time in Patent Office: 274 Days
• Field of Search: 318/701, 318/521, 318/523, 318/529, 310/166, 310/168, 310/198, 310/180, 310/181
• US Class Current: 310/198
• CPC Class Codes: H02K 19/103 Motors having windings on the stator and a variable reluctance soft-iron rotor without windings
• CPC Class Codes: H02K 3/28 Layout of windings or of connections between windings windings for pole-changing H02K17/06, H02K17/14, H02K19/12, H02K19/32
• CPC Class Codes: H02P 25/092 Converters specially adapted for controlling reluctance motors
• CPC Class Codes: H02P 25/0925 wherein the converter comprises only one switch per phase

Abstract

A reluctance machine system including a reluctance machine having a rotor and a stator including at least one phase winding and a full pitch auxiliary filed winding where constant currents are established in the auxiliary field winding to assist in the establishment of a magnetic field in the machine so as to improve the machine'"'"'s performance.

Claims

1. A reluctance machine system comprising:

(a) a reluctance machine including;

a stator defining a plurality of stator poles;

a rotor defining a plurality of rotor poles, the rotor being mounted for rotation with respect to the stator, the stator poles and the rotor poles being configured such that the total area of overlap between the rotor and stator poles is constant as the rotor rotates with respect to the stator;

at least N, separately energizable phase windings, where N is an integer greater than 2, each phase winding including a plurality of winding coils, where each winding coil surrounds a stator pole;

a full pitch auxiliary field winding, the auxiliary field winding comprising one or more full pitched coils, where each full pitched coil encircles a group of N stator poles, and wherein the group includes, for each of the N phase windings, a stator pole surrounded by a winding coil from that phase winding; and

(b) a power converter coupled to the reluctance machine, the power converter including;

a DC bus;

power switching devices coupling the phase windings to the DC bus for providing phase energization currents to the phase windings; and

circuitry for providing continuous energization current to the auxiliary field winding, wherein the magnetic flux produced by the auxiliary field winding is relatively constant.

2. The reluctance machine system of claim 1 wherein the rotor defines eight rotor poles, the stator defines twelve stator poles, wherein the there are three phase windings and wherein the auxiliary winding includes at least one winding coil surrounding three stator poles.

3. The reluctance machine system of claim 1 wherein the rotor defines four rotor poles, the stator defines six stator poles and wherein the auxiliary winding includes at least one winding coil surrounding three stator poles.

4. The reluctance machine system of claim 1 wherein the stator poles are defined by a plurality of slots defined by the stator and wherein the auxiliary winding is positioned within at least two of the slots.

5. The reluctance machine system of claim 4 wherein the slots containing the auxiliary winding are deeper than the slots that do not contain the auxiliary winding.

6. The reluctance machine system of claim 5 wherein the slots containing the auxiliary winding are substantially Y-shaped.

7. The reluctance machine system of claim 1 wherein the auxiliary field winding comprises a plurality of winding coils connected in series.

8. The reluctance machine system of claim 1 wherein the auxiliary field winding comprises at least one winding coil and where the number of winding turns in the auxiliary field coil is the same as the number of turns of a phase winding coil.

9. The reluctance machine system of claim 1 wherein the power switching devices are coupled to switching circuitry to provide discontinuous energization currents to the phase windings.

10. The reluctance machine system of claim 9 wherein the discontinuous currents provided to the phase windings comprises current pulses of a substantially trapezoidal shape.

11. The reluctance machine system of claim 10 wherein the average peak magnitude of the trapezoidal current pulses is the same as the average peak magnitude of the continuous current provided to the auxiliary field windings.

12. The reluctance machine system of claim 1 wherein the circuitry for providing continuous energization current to the auxiliary field winding comprises electrical connections for coupling the auxiliary field winding across a source of substantially constant DC voltage.

13. The reluctance machine system of claim 12 wherein the source of substantially constant DC voltage is the DC bus of the power converter.

14. The reluctance machine system of claim 12 further including a power switching device coupling the auxiliary field winding to the electrical connections, wherein the switching signals for the power switching device may be controlled to regulate the magnitude of the continuous current in the auxiliary field winding.

15. The reluctance machine system of claim 12 further including a circuit for providing switching signals to the power switching device to control the torque output of the machine.

16. A reluctance machine system comprising:

(a) a reluctance machine including;

a stator defining a N*6 stator poles, where N is an integer;

a rotor defining a N*4 rotor poles, the rotor being mounted for rotation with respect to the stator;

three phase windings, each phase winding including a plurality of winding coils, wherein each winding coil surrounds a stator pole;

a full pitch auxiliary field winding, the auxiliary field winding comprising at least one full pitch auxiliary winding coil surrounding a group of 3 stator poles, and wherein the group includes, for each of the phase windings, a stator pole surrounded by a winding coil from that phase winding; and

(b) circuitry for providing continuous energization current to the auxiliary field winding.

17. The reluctance machine system of claim 16 wherein N equals 2.

18. The reluctance machine system of claim 16 wherein N equals 1.

19. The reluctance machine system of claim 16 wherein the circuitry for providing continuous energization current to the auxiliary field winding comprises electrical connections coupled to a series connection of the auxiliary field winding and a variable resistor.

20. A reluctance machine system comprising:

(a) a reluctance machine including;

a stator defining a N*8 stator poles, where N is an integer;

a rotor defining a N*6 rotor poles, the rotor being mounted for rotation with respect to the stator;

four phase windings, each phase winding including a plurality of winding coils, wherein each winding coil surrounds a stator pole;

a full pitch auxiliary field winding, the auxiliary field winding comprising at least one full pitch auxiliary winding coil surrounding a group of 4 stator poles, and wherein the group includes, for each of the phase windings, a stator pole surrounded by a winding coil from that phase winding; and

(b) circuitry for providing continuous energization current to the auxiliary field winding.

21. The reluctance machine system of claim 20 wherein N equals 1.

22. The reluctance machine system of claim 20 wherein N equals 2.

23. A reluctance machine system comprising:

a reluctance machine comprising a rotor,

a stator defining a plurality of stator poles,

at least N separately energizable phase windings, N being an integer greater than 2,

wherein each phase winding surrounds a plurality of non-adjacent stator poles and wherein each stator pole surrounded by a given phase winding is separated from each other stator pole surrounded by the given phase winding by at least two stator poles;

the stator poles being configured in relation to a plurality of rotor poles such that the total area of overlap between the rotor and stator poles is constant as the rotor rotates with respect to the stator;

a full pitch auxiliary winding, wherein the full pitch auxiliary winding comprises at least one full pitch coil, wherein the full pitch coil encircles a group of N stator poles and where the group includes, for each of the N phase windings, at least one stator pole encircled by that phase winding; and

circuitry for maintaining constant current in the auxiliary winding during normal operation of the machine, wherein the magnetic flux produced by the auxiliary field windings is relatively constant.

24. The reluctance machine system of claim 23 wherein the circuitry for maintaining constant current in the auxiliary winding comprises a source of DC voltage.

25. The reluctance machine system of claim 24 wherein the source of DC voltage provides a substantially constant DC voltage to the auxiliary winding.

26. A reluctance motor system comprising:

a reluctance machine including a rotor, a stator, a plurality of phase windings and a full pitch auxiliary winding;

circuitry for energizing one or more of the phase windings with bi-polar current as a function of the rotor'"'"'s position with respect to the stator;

circuitry for energizing the auxiliary winding with uni-polar current so as to maintain continuous current in the auxiliary winding, wherein the magnetic flux produced by the auxiliary field winding is relatively constant.

27. The reluctance machine system of claim 26 wherein there are N phase windings, where N is an integer and wherein the auxiliary winding comprises a winding coil surrounding N stator poles.

28. A method of energizing a reluctance motor including a plurality of phase windings and a full pitch auxiliary winding, the method comprising the steps of:

energizing the phase winding with bi-polar current as a function of the rotor'"'"'s position with respect to the stator; and

energizing the auxiliary winding with uni-polar current so as to maintain continuous current in the auxiliary winding, producing relatively constant magnetic flux in the auxiliary field winding.

29. A reluctance machine system comprising:

(a) a reluctance machine including;

a stator defining a plurality of stator poles;

a rotor defining a plurality of rotor poles, the rotor being mounted for rotation with respect to the stator;

a plurality of phase windings, each phase winding including a plurality of winding coils, where each winding coil surrounds a stator pole;

a full pitch auxiliary field winding, the auxiliary field winding surrounding a plurality of stator poles; and

(b) a bi-polar power converter coupled to the reluctance machine, the power converter including;

a DC bus;

power switching devices coupling the phase windings to the DC bus for providing phase energization currents to the phase windings, where the phase energization currents vary in polarity over time and

circuitry for providing continuous energization current to the auxiliary field winding, wherein the magnetic flux produced by the auxiliary field winding is relatively constant.

30. The reluctance machine system of claim 29 wherein the power switching devices are controlled such that the polarity of the phase energization current for a given winding changes approximately when the inductance for the phase winding is at its maximum.

31. The reluctance machine system of claim 30 wherein the current in a given phase winding is controlled such that the phase current is positive when the inductance for the phase winding is increasing and negative when the inductance for the phase winding is decreasing.