GENERATING ELECTROMAGNETIC FORCES IN LARGE AIR GAPS

• US 20110101905A1
• Filed: 11/02/2009
• Published: 05/05/2011
• Est. Priority Date: 11/02/2009
• Status: Active Grant

• Current Assignee: Calnetix Technologies, LLC (General Electric Company)
• Original Assignee: Calnetix Incorporated (General Electric Company)
• Inventors: Filatov, Alexei V.
• Granted Patent: US 8,378,543 B2
• Time in Patent Office: Days
• US Class Current: 318/495
• CPC Class Codes: F16C 2360/44 Centrifugal pumps in general F04D
• CPC Class Codes: F16C 2380/26 Dynamo-electric machines or combinations therewith, e.g. electro-motors and generators in general H02K
• CPC Class Codes: F16C 32/0465 with permanent magnets provided in the magnetic circuit of the electromagnets
• CPC Class Codes: F16C 32/0468 of moving parts of the magnetic circuit, e.g. of the rotor
• CPC Class Codes: F16C 32/048 with active support of two degrees of freedom, e.g. radial magnetic bearings
• CPC Class Codes: H02K 7/09 with magnetic bearings

Abstract

An electromagnetic actuator generates electromagnetic forces across large radial gaps to support a body. The actuator has an actuator target having a rotational axis, and a target magnetic element arranged circumferentially around the rotational axis that has inner and outer magnetic poles. A cylindrical soft-magnetic target pole is magnetically coupled to the outer cylindrical magnetic pole of the target magnetic element. An actuator base includes radial poles arranged circumferentially around and radially spaced apart from the cylindrical soft-magnetic target pole. The radial poles and the cylindrical soft-magnetic target pole are magnetically coupled and define a plurality of magnetic control circuits. Control coils around the radial poles are configured to produce magnetic fluxes in the magnetic control circuits. The target magnetic element, the cylindrical soft-magnetic target pole, and the radial poles are magnetically coupled and define a magnetic bias circuit, the magnetic element producing magnetic flux in the magnetic bias circuit.

Claims

1. An electromagnetic actuator comprising:

an actuator target having a rotational axis, the target comprising;

a target magnetic element arranged circumferentially around the rotational axis and having inner and outer magnetic poles, the inner magnetic pole located closer to the rotational axis than the outer magnetic pole, and

a cylindrical soft-magnetic target pole piece magnetically coupled to the outer cylindrical magnetic pole of the target magnetic element;

an actuator base comprising;

a plurality of radial poles arranged circumferentially around and radially spaced apart from the cylindrical soft-magnetic target pole piece, the plurality of radial poles and the cylindrical soft-magnetic target pole piece defining radial gaps therebetween, and

a plurality of control coils around the plurality of radial poles; and

the plurality of radial poles and the cylindrical soft-magnetic target pole, magnetically coupled and defining a plurality of magnetic control circuits, the plurality of control coils configured to produce control magnetic fluxes in the plurality of magnetic control circuits, and the target magnetic element, the cylindrical soft-magnetic target pole, and the plurality of radial poles magnetically coupled and defining a magnetic bias circuit, the magnetic element configured to produce bias magnetic flux in the magnetic bias circuit.

2. The electromagnetic actuator of claim 1, wherein the actuator target further comprises a target bias magnetic flux return element magnetically coupled to the inner magnetic pole of the target magnetic element, the target bias magnetic flux return element further defining the magnetic bias circuit.

3. The electromagnetic actuator of claim 2, wherein the target bias magnetic flux return element comprises a soft-magnetic structure.

4. The electromagnetic actuator of claim 1, wherein the target magnetic element is a first target magnetic element and the cylindrical soft-magnetic target pole piece is a first cylindrical soft-magnetic target pole piece;

and the actuator target further comprising;

a second target magnetic element having inner and outer cylindrical magnetic poles arranged circumferentially around the rotational axis, the inner magnetic pole of the second target magnetic element located closer to the rotational axis than the outer magnetic pole of the second target magnetic element, the polarities of the inner and outer magnetic poles of the second target magnetic element opposite to polarities of the inner and outer magnetic poles of the first target magnetic element; and

a second cylindrical soft-magnetic target pole attached to the outer cylindrical magnetic pole of the second target magnetic element.

5. The electromagnetic actuator of claim 4 further including a third target magnetic element located axially in between the first and the second target magnetic elements and having a first disk-shaped magnetic pole and a second disk-shaped magnetic pole arranged circumferentially around the rotational axis;

the first disk-shaped pole adjacent the first target magnetic element and having the same polarity as the outer cylindrical pole of the first target magnetic element;

the second disk-shaped pole adjacent the second target magnetic element and having the same polarity as the outer cylindrical pole of the second target magnetic element.

6. The electromagnetic actuator of claim 1 wherein the actuator base further comprises a base bias magnetic flux return element magnetically coupled to the plurality of radial poles and further defining the magnetic bias circuit.

7. The electromagnetic actuator of claim 6 wherein the base bias magnetic flux return element comprises a stationary soft-magnetic cylindrical pole.

8. The electromagnetic actuator of claim 4 wherein the plurality of radial poles is a first plurality of radial poles, the plurality of control coils is a first plurality of control coils, and the plurality of magnetic control circuits is a first plurality of magnetic control circuits and the base bias magnetic flux return element further comprising:

a second plurality of radial poles arranged circumferentially around and radially spaced apart from the second cylindrical soft-magnetic target pole piece, the second plurality of radial poles and the second cylindrical soft-magnetic target pole piece defining air gaps therebetween;

a second plurality of control coils around the second plurality of radial poles; and

the second plurality of radial poles and the second cylindrical soft-magnetic target pole piece magnetically coupled and defining a second plurality of magnetic control circuits, the second plurality of control coils configured to produce control magnetic fluxes in the second plurality of magnetic control circuits.

9. The electromagnetic actuator of claim 6 further comprising a base magnetic element having a first pole and a second pole, the first pole magnetically coupled to the plurality of radial poles and having the polarity opposite to a polarity of the outer pole of the target magnetic element and the second pole magnetically coupled to the base bias magnetic flux return element.

10. The electromagnetic actuator of claim 6 further comprising a soft-magnetic spacer installed between and magnetically coupled to the plurality of the radial poles and the base bias magnetic flux return element.

11. An electric machine system comprising:

a stator;

a rotor having a rotational axis configured to move relative to the stator;

an electromagnetic actuator sub-assembly comprising;

an actuator target coupled to the rotor, the target comprising;

a target magnetic element arranged circumferentially around the rotational axis and having inner and outer magnetic poles, the inner magnetic pole located closer to the rotational axis than the outer magnetic pole, and

a cylindrical soft-magnetic target pole piece magnetically coupled to the outer cylindrical magnetic pole of the target magnetic element;

an actuator base coupled to the stator, the actuator base comprising;

a plurality of radial poles arranged circumferentially around and radially spaced apart from the cylindrical soft-magnetic target pole piece, the plurality of radial poles and the cylindrical soft-magnetic target pole piece defining radial gaps therebetween, and

a plurality of control coils around the plurality of radial poles;

the plurality of radial poles and the cylindrical soft-magnetic target pole, magnetically coupled and defining a plurality of magnetic control circuits, the plurality of control coils configured to produce control magnetic fluxes in the plurality of magnetic control circuits, and the target magnetic element, the cylindrical soft-magnetic target pole, and the plurality of radial poles magnetically coupled and defining a magnetic bias circuit, the magnetic element configured to produce bias magnetic flux in the magnetic bias circuit;

one or more position sensors configured to sense a position of the body; and

at least one control electronics package configured to control the magnetic flux in the plurality of magnetic control circuits.

12. The system of claim 11 wherein the body is coupled to a driven load, the driven load comprising at least one of a flywheel, a compressor, a generator, or an expander.

13. The system of claim 11 wherein the body is coupled to a driver, the driver comprising at least one of a motor, an engine, or a turbine.

14. The system of claim 11 wherein the electronic control package is configured to control the magnetic fluxes in the radial magnetic control circuits by energizing the control coil around each of the plurality of radial poles with a control current.

15. The system of claim 14 wherein the magnetic fluxes exert radial electromagnetic forces on the actuator target.

16. The system of claim 15 wherein the electronic control package is further configured to energize the control coils around each of the plurality of radial poles with control currents in response to changes of signals from the position sensors so that the rotor is supported by electromagnetic forces without a mechanical contact with the stator.

17. The system of claim 11 further comprising a can separating the body from the base configured to prevent access of a working fluid to at least the control coils.

18. A method for exerting a radial force on a body, the body configured to rotate about a rotational axis, the method comprising:

generating a bias magnetic flux with a target magnetic element mounted on the body circumferentially around the rotational axis and having inner and outer magnetic poles, the inner magnetic pole located closer to the rotational axis than the outer magnetic pole;

communicating the bias magnetic flux between a first radial pole assembly, the body, and a second radial pole assembly, the first and second radial pole assemblies magnetically coupled and spaced apart from one another along the rotational axis, the first and second radial pole assemblies each circumferentially arranged around the rotational axis, and the first and second radial pole assemblies separated from the body by an air gap, the bias magnetic flux propagating through the body in a direction parallel to the rotational axis;

communicating a first radial control magnetic flux between the first radial pole assembly and a first body pole coupled to the body, the first radial control magnetic flux propagating between a first radial pole of the first pole assembly, the body pole, and a second pole of the first pole assembly, the first radial control magnetic flux propagating in a radial direction orthogonal to the rotational axis; and

communicating a second radial control magnetic flux between the second radial pole assembly and a second body pole coupled to the body and spaced apart from the first body pole along the rotational axis, the second radial control magnetic flux propagating between a first radial pole of the second pole assembly, the second body pole, and a second pole of the second pole assembly, the second radial control magnetic flux propagating in a radial direction orthogonal to the rotational axis opposite from the first radial control magnetic flux, the bias magnetic flux and the first and second control magnetic fluxes combining to affect an electromagnetic force on the actuator target.

19. The method of claim 18 wherein the bias magnetic flux generated by the target magnetic element is a first bias magnetic flux;

and the method further comprising generating a second bias magnetic flux with a base magnetic element residing between the first and second radial poles assemblies, the second bias magnetic flux combining with the first bias magnetic flux.

20. The method of claim 18 wherein communicating a first and second radial control magnetic fluxes further comprises:

energizing a control coil around each of the first and second radial poles of the first and second radial pole assemblies with a control current, the control current in each of the control coils capable of variation based on the desired magnitude of the first and second radial control magnetic fluxes.