Electromagnetic machine system having current injection for inductive excitation of windings

Patent metadata

Field	Value
Publication number	US-10498279-B2
Application number	US-201514949203-A
Country	US
Kind code	B2
Filing date	Nov 23, 2015
Priority date	Nov 23, 2015
Publication date	Dec 3, 2019
Grant date	Dec 3, 2019

Abstract

A electromagnetic machine system includes a rotor and a stator positioned about the rotor. A current injection mechanism is coupled with windings of the stator and structured to inject electrical currents therein so as to change a flux distribution of a magnetic field produced by the stator. The injected currents may be harmonic currents. The rotor further includes an inductor positioned to interact with the magnetic field when the flux distribution is changed, to produce an electrical excitation current for exciting windings in the rotor. The machine system may be a synchronous motor or generator, and may be brushless. Applications of the current injection strategy to direct torque control and vector control are also disclosed.

First claim

What is claimed is:

1. An electromagnetic machine system comprising:
a rotor including rotor windings;
a stator positioned about the rotor and including stator windings structured to conduct primary electrical currents;
a current injection mechanism coupled with the stator windings and structured to inject secondary electrical currents into the stator windings such that a flux distribution of a magnetic field produced by the stator is changed; and
the rotor further including an inductor coupled with the rotor windings and positioned to interact with the magnetic field when the flux distribution is changed, so as to produce an electrical excitation current for exciting the rotor windings, wherein the inductor is a part of exciter circuitry resident on the rotor and including a rectifier structured to convert the electrical excitation current from AC to DC.

2. The machine system of claim 1 wherein an air gap extends between the rotor and the stator, and the inductor is positioned adjacent to or within the air gap.

3. The machine system of claim 2 wherein the rotor includes a pole shoe and the inductor includes at least one coil mounted upon or within the pole shoe.

4. The machine system of claim 1 wherein the current injection mechanism includes an AC to AC converter structured to inject harmonic currents into the stator windings.

5. The machine system of claim 1 further including an exciter separate from the rotor and coupled to the exciter circuitry.

6. The machine system of claim 1 comprising a synchronous electric motor that includes the rotor and the stator.

7. The machine system of claim 6 wherein the synchronous electric motor is brushless.

8. A rotor for an electromagnetic machine comprising:
a rotor body defining a rotor axis;
a plurality of sets of rotor windings positioned on the rotor body at a plurality of locations spaced circumferentially about the rotor axis, and each of the plurality of sets of rotor windings being positioned and oriented relative to the longitudinal axis so as to produce a rotor magnetic field, when electrically excited, that interacts with a stator magnetic field produced by a stator extending about the rotor and conducting primary electrical currents; and
exciter circuitry resident on the rotor body, the exciter circuitry being coupled to the rotor windings and including an inductor having at least one of a position and an orientation about the rotor axis that is different from any one of the rotor windings, and the inductor being structured according to the at least one of a position and an orientation to interact with the stator magnetic field to produce an excitation current for exciting the rotor windings, when a flux distribution of the stator magnetic field is changed in response to injection of secondary electrical currents into the stator, wherein the exciter circuitry includes a rectifier coupled to the inductor, and a DC bus coupling the rectifier to the rotor windings.

9. The rotor of claim 8 wherein the inductor includes at least one coil.

10. The rotor of claim 9 further comprising a pole shoe, and the at least one coil is mounted upon or within the pole shoe.

11. The rotor of claim 10 further including a plurality of pole shoes mounted upon pole supports each extending outwardly from the rotor body and having a set of the rotor windings mounted thereon.

12. The rotor of claim 8 wherein the exciter circuitry further includes electrical connection leads structured to couple the exciter circuitry with an external exciter.

13. A method of operating an electromagnetic machine system comprising:
providing a rotor including rotor windings, a stator positioned about the rotor and including stator windings structured to conduct primary electrical currents, a current injection mechanism coupled with the stator windings and structured to inject secondary electrical currents into the stator windings such that a flux distribution of a magnetic field produced by the stator is changed, the rotor including an inductor coupled with the rotor windings and positioned to interact with the magnetic field when the flux distribution is changed so as to produce an electrical excitation current for exciting the rotor windings, the inductor being a part of exciter circuitry resident on the rotor and including a rectifier structured to convert the electrical excitation current from AC to DC;
injecting with the current injection mechanism electrical current into the stator windings in the electromagnetic machine system, such that the flux distribution pattern of the magnetic field produced by the stator is changed;
inducing the electrical excitation current via the magnetic field in the inductor of the rotor in the electromagnetic machine system when the flux distribution pattern is changed;
converting with the rectifier the electrical excitation current from AC to DC; and
exciting the windings of the rotor via the electrical excitation current.

14. The method of claim 13 wherein the injecting includes injecting harmonic current into windings of the stator so as to vary the flux distribution pattern in an air gap between the stator and the rotor.

15. The method of claim 14 further comprising calculating a flux reference term responsive to a magnitude of the injected electrical current, and determining a switch control command responsive to the flux reference term.

16. The method of claim 15 wherein the stator and rotor are parts of a synchronous electric motor, and further comprising maintaining synchronous coupling between the rotor and the stator by way of the exciting, during a fault condition of an external exciter.

Assignees

• Abb Technology Ltd
• Abb Schweiz Ag

Inventors

• Ouyang Wen
• Li Jun
• Kim Hongrae

Classifications

• H02K19/28

  for self-excitation · CPC title

• H02K19/26

  characterised by the arrangement of exciting windings · CPC title

• H02K19/12

  characterised by the arrangement of exciting windings, e.g. for self-excitation, compounding or pole-changing · CPC title

• H02P25/03 Primary

  with brushless excitation · CPC title