Homopolar, flux-biased hysteresis bearingless motor

Patent metadata

Field	Value
Publication number	US-10177627-B2
Application number	US-201615227256-A
Country	US
Kind code	B2
Filing date	Aug 3, 2016
Priority date	Aug 6, 2015
Publication date	Jan 8, 2019
Grant date	Jan 8, 2019

Abstract

Described is a bearingless motor based upon a homopolar flux-biased magnetic bearing for force generation and a hysteresis motor for torque generation. The bearingless slice motor levitates and rotates a ring-shaped rotor made of a semi-hard magnetic material. The rotor is biased with a homopolar permanent-magnetic flux, on which 2-pole flux can be superimposed to generate suspension forces. Torque is generated by a hysteretic coupling between the rotor and a rotating multi-pole stator field.

First claim

What is claimed is:

1. A homopolar flux-biased hysteresis bearingless motor comprising:
(a) a stator comprising a bottom plate and a plurality of teeth projecting from said bottom plate;
(b) a flux-biasing structure disposed in a central portion of said stator and having a shape selected such that said stator and said flux-biasing structure define a space having a predetermined shape;
(c) a hysteresis rotor disposed in the space defined by said flux-biasing structure and stator;
(d) stator windings coupled to said stator teeth and through which electric current may flow to induce two sets of magnetic flux on said hysteresis rotor said two sets of flux corresponding to (1) a motor flux; and (2) a suspension flux; and
(e) means for providing a homopolar bias flux which traverses through said hysteresis rotor radially and returns via the stator teeth and the bottom plate of said stator and wherein said stator windings are configured to superpose a motor flux and a suspension flux on the homopolar bias flux to generate a torque and a radial force.

2. The homopolar flux-biased hysteresis bearingless motor of claim 1 wherein:
(a1) said stator teeth are provided having an L-shape; and
(a2) said flux-biasing structure is provided as an inner central flux-biasing structure which forms with said stator teeth an annular space having dimensions selected to accept said hysteresis rotor.

3. The homopolar flux-biased hysteresis bearingless motor of claim 1 wherein:
said stator teeth and said bottom plate are provided from a soft magnetic material having lamination to reduce eddy-current loss;
said flux-biasing structure is provided from one of: a soft magnetic material and a semi-hard magnetic material having a level of hysteresis;
said rotor is provided from a semi-hard magnetic material having some level of hysteresis.

4. The homopolar flux-biased hysteresis bearingless motor of claim 2 wherein:
(e1) said means for providing a homopolar bias flux comprises a permanent magnet disposed such that the homopolar bias flux provided by said permanent magnet traverses through the hysteresis rotor radially and returns via the teeth and the bottom plate of said stator.

5. The homopolar flux-biased hysteresis bearingless motor of claim 2 wherein:
(e1) said means for providing a homopolar bias flux comprises a permanent magnet disposed such that a radially inward homopolar bias flux provided by said permanent magnet traverses through the hysteresis rotor, the stator teeth and the bottom plate of said stator.

6. The homopolar flux-biased hysteresis bearingless motor of claim 1 wherein said stator further comprises at least one of:
(a4) windings disposed to superpose a 2-pole suspension flux on the bias flux to generate a radial force on the hysteresis rotor in a first desired direction; and
(a5) windings disposed to superpose a 2-pole suspension flux on the bias flux to generate a radial force on the hysteresis rotor in a second desired direction which is orthogonal to the first direction.

7. The homopolar flux-biased hysteresis bearingless motor of claim 6 wherein said windings are disposed such that the superimposed 2-pole suspension flux is added to the homopolar flux in a first direction and subtracted from the homopolar flux in a second opposite direction, thereby generating a differential magnetic force on said hysteresis rotor.

8. The homopolar flux-biased hysteresis bearingless motor of claim 1 further comprising:
two or more position sensors disposed to sense at least radial positions of said hysteresis rotor; and
a controller coupled to said two or more sensors such that in response to signals provided thereto from said two or more sensors, said controller regulates the strength of the flux based upon the rotor position to provide stable suspension of said hysteresis rotor.

9. The homopolar flux-biased hysteresis bearingless motor of claim 1 further comprising two or more sensors disposed in relation to said rotor so as to measure at least radial displacements of said hysteresis rotor.

10. The homopolar flux-biased hysteresis bearingless motor of claim 9 wherein the two or more sensors are provided as one of: a tachometer; an encoder; a capacitance sensor; an eddy-current sensor; or one or more sensing coils integrated together with the stator winding that generate electric potential difference as responding to the high-frequency component of magnetic flux linking to the sensing coil.

11. The homopolar flux-biased hysteresis bearingless motor of claim 10 further comprising a controller coupled to said two or more sensors such that in response to signals provided thereto from said two or more sensors, said controller regulates the strength of the flux based upon the rotor position to provide stable suspension of said hysteresis rotor.

12. The homopolar flux-biased hysteresis bearingless motor of claim 1 wherein said coils are disposed to superpose a 2n-pole rotating flux (n≥3) to generate a torque.

13. A pump comprising:
(a) a homopolar flux-biased hysteresis bearingless motor comprising:
a stator comprising a bottom plate and a plurality of teeth projecting from said bottom plate;
a flux-biasing structure disposed in a central portion of said stator and having a shape selected to define a space having a predetermined shape;
a hysteresis rotor disposed in the space defined by said flux-biasing structure and stator;
stator windings coupled to said stator and through which electric current may flow to induce two sets of magnetic flux: (1) a motor flux; and (2) a suspension flux; and
a permanent magnet for providing a homopolar bias flux which traverses through said hysteresis rotor radially and returns via the teeth and the bottom plate of the stator and wherein said stator windings are configured to superpose a two-pole suspension flux on the homopolar bias flux to generate a radial force; and

(b) an impeller assembly disposed in relation to said stator in the space defined by said flux-biasing structure and said stator teeth, said impeller assembly comprising
an impeller; and
a hysteresis rotor coupled to said impeller.

14. The homopolar flux-biased hysteresis bearingless motor of claim 13 further comprising:
two or more position sensors disposed to sense at least radial positions of said hysteresis rotor; and
a controller coupled to said two or more sensors such that in response to signals provided thereto from said two or more sensors, said controller regulates the strength of the flux based upon the rotor position to provide stable suspension of said hysteresis rotor.

15. The homopolar flux-biased hysteresis bearingless motor of claim 13 further comprising two or more sensors disposed in relation to said rotor so as to measure at least radial displacements of said hysteresis rotor.

16. The homopolar flux-biased hysteresis bearingless motor of claim 15 wherein the two or more sensors are provided as one of: a tachometer; an encoder; a capacitance sensor; an eddy-current sensor; or one or more sensing coils integrated together with the stator winding that generate electric potential difference as responding to the high-frequency component of magnetic flux linking to the sensing coil.

17. The homopolar flux-biased hysteresis bearingless motor of claim 16 further comprising a controller coupled to said two or more sensors such that in response to signals provided thereto from said two or more sensors, said controller regulates the strength of the flux based upon the rotor position to provide stable suspension of said hysteresis rotor.

Assignees

• Massachusetts Inst Technology

Inventors

• Noh Minkyun
• Trumper David L

Classifications

• F04D29/048

  magnetic; electromagnetic · CPC title

• H02K11/20

  for measuring, monitoring, testing, protecting or switching (rectifiers H02K11/04; power electronics H02K11/33) · CPC title

• H02K5/128

  using air-gap sleeves or air-gap discs · CPC title

• H02K19/08

  Motors having windings on the stator and a smooth rotor without windings of material with large hysteresis, e.g. hysteresis motors · CPC title

• F16C32/0461

  of stationary parts of the magnetic circuit · CPC title