Shielded power coupling device

• US 20070188284A1
• Filed: 01/29/2007
• Published: 08/16/2007
• Est. Priority Date: 02/26/2003
• Status: Active Grant

• Current Assignee: Analogic Corporation
• Original Assignee: Analogic Corporation
• Inventors: Dobbs, John
• Granted Patent: US 8,350,655 B2
• Time in Patent Office: Days
• US Class Current: 336/120
• CPC Class Codes: A61B 6/56 Details of data transmission or power supply, e.g. use of slip rings
• CPC Class Codes: H01F 27/36 Electric or magnetic shields or screens movable for varying inductance H01F21/10
• CPC Class Codes: H01F 27/363 made of electrically conductive material
• CPC Class Codes: H01F 38/18 Rotary transformers

Abstract

Axisymmetric solid of revolution derivable from section at FIG. 5 is generally toroidal with electric current(s) in windings 110, 160 preferably flowing circumferentially along major circle(s) during power coupling device operation. Current(s) in windings 110, 160; current(s) in half-shields 120, 170; and the volume of space swept out by shield airgap(s) 101 emerge from plane of paper perpendicularly at FIG. 5 but as these emerge therefrom they curve to follow toroidal major circle(s). Cores 115, 165 preferably shunt and align magnetic flux such that magnetic field lines escape therefrom primarily only in region(s) of core airgap(s) and such that magnetic flux loops lie in planes of toroidal minor circle(s). Half-shield(s) 120, 170 preferably have electrically conductive material(s) distributed therein as is sufficient to substantially cancel magnetic flux lines impinging thereon before effects of such impinging magnetic flux lines would reach shield airgap(s) 101 and/or outer surface(s) of half-shields 120, 170.

Claims

1. A shielded power coupling device transferring electric power between a stationary subsystem and a rotatable subsystem that is inductively coupled to and arranged in close proximity to the stationary subsystem and that, during operation of the shielded power coupling device, is capable of rotating about an axis of rotation which is also substantially an axis of symmetry for both the stationary subsystem and the rotating subsystem, the shielded power coupling device comprising:

a) an inductive field generating element capable of converting electric power to an inductive coupling field;

b) an inductive coupling field receiving element capable of converting the inductive coupling field to electric power;

c) an inductive coupling efficiency increasing element capable of increasing inductive coupling between the inductive field generating element and the inductive coupling field receiving element; and

d) shielding peripheral to the inductive coupling efficiency increasing element that is capable of substantially eliminating leakage of electromagnetic radiation from the shielded power coupling device when the shielded power coupling device is operated at power levels exceeding 2.5 kW.

2. A shielded power coupling device transferring electric power between a stationary member and a rotating member, the shielded power coupling device comprising:

a) a reluctance-decreasing primary core defining a first primary core recess;

b) a reluctance-decreasing secondary core disposed adjacent the primary core and defining a first secondary core recess, the primary core and the secondary core being arranged so as to form a core airgap therebetween permitting relative rotation of the primary core and the secondary core about an axis of rotation;

c) a first electrically conductive primary winding disposed substantially within the first primary core recess;

d) a first electrically conductive secondary winding disposed substantially within the first secondary core recess; and

e) a shield;

f) wherein a first primary electric current flowing through the first primary winding produces a first secondary electric current flowing through the first secondary winding, creating a fringing field at the periphery of the core airgap; and

g) the shield substantially cancels the fringing field.

3. A shielded power coupling device in accordance with claim 2 wherein the shield forms at least one substantially continuous electrical path constituting a closed electric circuit around the axis of rotation.

4. A shielded power coupling device in accordance with claim 2 wherein the shield forms at least one substantially circular electrical path constituting a closed electric circuit around the axis of rotation.

5. A shielded power coupling device in accordance with claim 2 wherein the shield comprises electrically conductive material in at least one ring-like band adjacent to and alongside the core airgap.

6. A shielded power coupling device in accordance with claim 2 wherein the shield has electrically conductive material at such locations and in such electrical conductivity or conductivities and thickness or thicknesses as is sufficient to support electric currents capable of inducing a magnetic field that is capable of substantially canceling the fringing field.

7. A shielded power coupling device in accordance with claim 2 wherein, during cancellation of the fringing field by the shield, an image current flowing in the shield produces a magnetic field that is capable of canceling the fringing field.

8. A shielded power coupling device in accordance with claim 7 wherein the net image current in the shield flows substantially circumferentially about the axis of rotation during cancellation of the fringing field by the shield.

9. A shielded power coupling device in accordance with claim 7 wherein the overall configuration of the shielded power coupling device is substantially axisymmetric, and the net image current in the shield flows substantially circumferentially about the axis of axisymmetry during cancellation of the fringing field by the shield.

10. A shielded power coupling device in accordance with claim 7 wherein the overall configuration of the shielded power coupling device is substantially toroidal, and the net image current in the shield flows substantially along a circle coaxial with a major circle thereof during cancellation of the fringing field by the shield.

11. A shielded power coupling device in accordance with claim 2 wherein, during cancellation of the fringing field by the shield, a net image current flows in the shield that is substantially equal in magnitude but opposite in sign to the net electric current flowing through the windings.

12. A shielded power coupling device in accordance with claim 2 wherein the shield is a single-part shield having a shield airgap that is substantially nonadjacent with respect to the core airgap.

13. A shielded power coupling device in accordance with claim 12 wherein, as measured in a direction perpendicular to an imaginary surface bounding the volume of space swept out by the core airgap during operation of the shielded power coupling device, the shield airgap is not less than three core airgap thicknesses from the core airgap.

14. A shielded power coupling device in accordance with claim 12 wherein, as measured in a direction perpendicular to an imaginary surface bounding the volume of space swept out by the core airgap during operation of the shielded power coupling device, the shield airgap is not less than five core airgap thicknesses from the core airgap.

15. A shielded power coupling device in accordance with claim 2 wherein thickness of the shield in the region of the core airgap is sufficient to achieve an electrical conductivity equivalent to that of aluminum in a thickness of not less than five core airgap thicknesses.

16. A shielded power coupling device in accordance with claim 2 wherein thickness of the shield in the region of the core airgap is sufficient to achieve an electrical conductivity equivalent to that of aluminum in a thickness of not less than ten core airgap thicknesses.

17. A shielded power coupling device in accordance with claim 2 wherein the shield is a multipartite shield having a shield airgap permitting relative movement during operation of the shielded power coupling device.

18. A shielded power coupling device in accordance with claim 17 wherein the shield airgap is substantially adjacent the core airgap.

19. A shielded power coupling device in accordance with claim 18 wherein thickness of the shield in the region of the core airgap is sufficient to achieve an electrical conductivity equivalent to that of aluminum in a thickness of not less than five core airgap thicknesses.

20. A shielded power coupling device in accordance with claim 18 wherein thickness of the shield in the region of the core airgap is sufficient to achieve an electrical conductivity equivalent to that of aluminum in a thickness of not less than ten core airgap thicknesses.

21. A shielded power coupling device in accordance with claim 18 wherein thickness of the shield in the region of the core airgap is sufficient to achieve an electrical conductivity equivalent to that of aluminum in a thickness of not less than two shield airgap thicknesses.

22. A shielded power coupling device in accordance with claim 18 wherein thickness of the shield in the region of the core airgap is sufficient to achieve an electrical conductivity equivalent to that of aluminum in a thickness of not less than four shield airgap thicknesses.

23. A shielded power coupling device in accordance with claim 2 wherein, during operation of the shielded power coupling device, the net electric current flowing through the windings is substantially zero.

24. A shielded power coupling device in accordance with claim 2 wherein

a) the primary core further defines a second primary core recess;

b) the secondary core further defines a second secondary core recess;

c) the shielded power coupling device further comprises;

i) a second electrically conductive primary winding disposed substantially within the second primary core recess; and

ii) a second electrically conductive secondary winding disposed substantially within the second secondary core recess;

d) wherein a second primary electric current flowing through the second primary winding produces a second secondary electric current flowing through the second secondary winding; and

e) during operation of the shielded power coupling device, the instantaneous net electric current flowing through the primary windings is substantially zero.

25. A shielded power coupling device in accordance with claim 2 wherein the secondary core recesses are disposed opposite the primary core recesses and are spaced apart therefrom.

26. A shielded power coupling device in accordance with claim 2 wherein the recesses are substantially annular.

27. A shielded power coupling device in accordance with claim 2 wherein the cores are of substantially semitoroidal configuration.

28. A shielded power coupling device in accordance with claim 2 wherein the primary core and the secondary core are of substantially axisymmetric configuration with mutually collinear axes of symmetry thereof being collinear with the axis of rotation.

29. A shielded power coupling device in accordance with claim 2 wherein, during operation of the shielded power coupling device, the core airgap sweeps out a volume in space of configuration substantially corresponding to one or more species selected from among the group consisting of planar configuration, cylindrical configuration, and conical configuration.

30. A shielded power coupling device in accordance with claim 2 wherein a volume in space swept out by the core airgap during operation of the shielded power coupling device is of substantially planar configuration and intervenes axially with respect to the axis of rotation between the primary core and the secondary core.

31. A shielded power coupling device in accordance with claim 2 wherein a volume in space swept out by the core airgap during operation of the shielded power coupling device is of substantially cylindrical configuration and intervenes radially with respect to the axis of rotation between the primary core and the secondary core.

32. A shielded power coupling device in accordance with claim 2 wherein a volume in space swept out by the core airgap during operation of the shielded power coupling device is of substantially conical configuration and intervenes both axially and radially with respect to the axis of rotation between the primary core and the secondary core.

33. A shielded power coupling device in accordance with claim 2 wherein the shield is of substantially axisymmetric configuration with axis of symmetry thereof being collinear with the axis of rotation.

34. A shielded power coupling device in accordance with claim 2 wherein loops of magnetic flux linking the primary core and the secondary core during operation of the shielded power coupling device lie in substantially meridional planes with respect to the axis of rotation.

35. A shielded power coupling device in accordance with claim 2 wherein mutually opposed core surfaces separated by the core airgap are substantially smooth, substantially mutually parallel, and substantially normal to the predominant direction of magnetic flux lines bridging the mutually opposed core surfaces during operation of the shielded power coupling device.

36. A shielded power coupling device in accordance with claim 2 wherein the overall configuration of the shielded power coupling device is substantially toroidal, loops of magnetic flux linking the primary core and the secondary core during operation of the shielded power coupling device lying substantially in planes of minor circles thereof.

37. A shielded power coupling device in accordance with claim 2 wherein, as viewed in a meridional section with respect to the axis of rotation, except for lines of magnetic flux that are responsible for presence of the fringing field, lines of magnetic flux linking the primary core and the secondary core during operation of the shielded power coupling device bridge the core airgap so as to be normal to an imaginary surface bounding a volume in space swept out by the core airgap during operation of the shielded power coupling device.

38. A shielded power coupling device in accordance with claim 2 wherein the primary core and the secondary core each comprise a plurality of core segments arranged in substantially mutually adjacent fashion so as to collectively approximate a substantially axisymmetric configuration.

39. A shielded power coupling device in accordance with claim 38 wherein at each the primary core and the secondary core, the core segments are arranged such that space intervening between mutually adjacent segments in a circumferential direction with respect to the axis of rotation is not more than the width of one of the core segments in the circumferential direction.

40. A shielded power coupling device in accordance with claim 38 wherein at each the primary core and the secondary core, the core segments are arranged such that space intervening between mutually adjacent segments in a circumferential direction with respect to the axis of rotation is not more than one-half of the width of one of the core segments in the circumferential direction.

41. A shielded power coupling device in accordance with claim 38 wherein at least one of the core segments has a passageway permitting passage therethrough of a lead wire for at least one of the windings.

42. A shielded power coupling device in accordance with claim 41 wherein the passageway is disposed on the core segment at such location and in such manner as to not substantially alter reluctance of the path taken by magnetic lines of flux therethrough during operation of the power coupling device.

43. A shielded power coupling device in accordance with claim 41 wherein the passageway is disposed on the core segment at a location other than a core-airgap interface.

44. A shielded power coupling device in accordance with claim 41 wherein the passageway is disposed on the core segment at a location on the core segment which is a back face that is a farthest surface thereof from the core airgap.

45. A shielded power coupling device in accordance with claim 38 wherein passageways permitting passage of at least one pair of lead wires for at least one of the windings are disposed in kitty-corner fashion on mutually adjacent core segments.

46. A shielded power coupling device in accordance with claim 38 wherein passageways permitting passage of at least one pair of lead wires for at least one of the windings are disposed on the same core segment at diagonally opposed locations at either end thereof in the direction in which at least one of the windings is wound within at least one of the recesses.

47. A shielded power coupling device in accordance with claim 2 wherein lead wires of the first primary winding pass through the primary core in such fashion and at such locations as will substantially minimize magnetic field of a virtual current loop formed in part by the first primary winding lead wires.

48. A shielded power coupling device in accordance with claim 2 wherein lead wires of the secondary winding pass through the first secondary core in such fashion and at such locations as will substantially minimize magnetic field of a virtual current loop formed in part by the first secondary winding lead wires.

49. A shielded power coupling device in accordance with claim 2 wherein misaligned magnetic flux including that due to the fringing field and any virtual current loops is not more than 1/100th of total magnetic flux linking the cores during operation of the shielded power coupling device.

50. A shielded power coupling device in accordance with claim 2 wherein misaligned magnetic flux including that due to the fringing field and any virtual current loops is not more than 1/1,000th of total magnetic flux linking the cores during operation of the shielded power coupling device.

51. A shielded power coupling device in accordance with claim 2 wherein misaligned magnetic flux including that due to the fringing field and any virtual current loops is not more than 1/10,000th of total magnetic flux linking the cores during operation of the shielded power coupling device.

52. A shielded power coupling device comprising:

a) a primary winding

i) having substantially axisymmetric configuration, and

ii) defining a circumferential direction;

b) a secondary winding

i) having substantially axisymmetric configuration,

ii) substantially concentric with or lying in a plane substantially parallel to a plane containing the circumferential direction,

iii) capable of rotating relative to the primary winding, and

iv) inductively coupled to the primary winding; and

c) a shield having at least one airgap permitting relative rotation between the primary winding and the secondary winding;

d) wherein the shield supports flow of electric current in the circumferential direction.

53. A shielded power coupling device comprising:

a) at least two substantially arcuate windings arranged in mutually radially and/or axially displaced fashion relative to an approximate major circle of an imaginary toroid; and

b) at least one electrically conductive shield encircling and/or encircled by the windings;

c) wherein, upon application of an alternating electric current to at least one of the windings, flux lines linking at least a portion of the windings lie substantially in planes of minor circles of the imaginary toroid; and

,

d) the shield supports flow of electric current along a direction of a circle coaxial with the major circle of the imaginary toroid sufficient to induce a magnetic field capable of substantially canceling a magnetic field due to a net electric current flowing in the windings upon application of the alternating electric current to at least one of the windings.

54. A shielded power coupling device transferring electric power between a stationary subsystem and a rotatable subsystem that is inductively coupled to and arranged in close proximity to the stationary subsystem and that, during operation of the shielded power coupling device, is capable of rotating about an axis of rotation which is also substantially an axis of symmetry for both the stationary subsystem and the rotating subsystem, the shielded power coupling device comprising:

a) inductive field generating means for converting electric power to an inductive coupling field;

b) inductive coupling field receiving means for converting the inductive coupling field to electric power;

c) inductive coupling efficiency increasing means for increasing inductive coupling between the inductive field generating means and the inductive coupling field receiving means; and

d) shielding means peripheral to the inductive coupling efficiency increasing means for substantially eliminating leakage of electromagnetic radiation from the shielded power coupling device when the shielded power coupling device is operated at power levels exceeding 2.5 kW.

55. A method for transferring electric power between a stationary subsystem and a rotatable subsystem that is inductively coupled to and arranged in close proximity to the stationary subsystem and that, during operation of the shielded power coupling device, is capable of rotating about an axis of rotation which is also substantially an axis of symmetry for both the stationary subsystem and the rotating subsystem, the method comprising:

a) using an inductive field generating element to convert electric power to an inductive coupling field;

b) using an inductive coupling field receiving element to convert the inductive coupling field to electric power;

c) using an inductive coupling efficiency increasing element to increase inductive coupling between the inductive field generating element and the inductive coupling field receiving element; and

d) using shielding peripheral to the inductive coupling efficiency increasing element to substantially eliminate leakage of electromagnetic radiation from the shielded power coupling device when the shielded power coupling device is operated at power levels exceeding 2.5 kW.

56. A flux-aligning core set for use with one or more windings and one or more shields, the core set comprising:

a) a plurality of flux-aligning core segments, each of which

i) is composed of one or more substances having reluctance lower than that of air and

ii) has at least two arm-like members;

b) wherein the plurality of flux-aligning core segments are arranged in substantially axisymmetric fashion such that

i) at least one of the winding or windings can be routed along one or more circumferentially oriented cradle-like recesses formed by cooperation of at least two of the two or more arm-like members of each of at least a portion of the plurality of flux-aligning core segments; and

ii) when at least two of the two or more arm-like members of each of at least a portion of the plurality of flux-aligning core segments are arranged in mutual opposition across an airgap with at least two arm-like members of each of at least a portion of a counterpart plurality of core segments of a counterpart core set that is substantially a reflection of the flux-aligning core set across the airgap, at least a portion of the flux-aligning core segments and at least a portion of the counterpart core segments cooperate to complete or lower reluctance of a multiplicity of magnetic paths

1) passing through the flux-aligning core set and the counterpart core set to bridge the airgap, and

2) substantially lying in meridional planes relative to the axis of axisymmetry.

57. A passage-containing core segment composed of one or more substances having reluctance lower than that of air and comprising:

a) one or more passages permitting passage of one or more windings therethrough; and

b) two or more arm-like members creating one or more cradle-like recesses therebetween along which at least one of the winding or windings can be routed;

c) wherein at least one of the passage or passages is disposed on the passage-containing core segment in at least one location such that, when at least two of the two or more arm-like members of the passage-containing core segment are arranged in mutual opposition across an airgap with at least two arm-like members of a first counterpart core segment that is substantially a reflection of the passage-containing core segment across the airgap, reluctance of a magnetic path passing through the passage-containing core segment and the first counterpart core segment to bridge the airgap is not substantially different than what the reluctance of the magnetic path would be were there no passage in the passage-containing core segment.

58. A system including a shielded inductive power coupling device, the system comprising:

a) a stationary member;

b) a rotatable member inductively coupled to the stationary member;

c) a power source; and

d) a shielded inductive power coupling device responsive to the power source and capable of transmitting power from the power source to at least one of the stationary member and the rotatable member, the inductive power coupling device comprising;

i) a primary reluctance-decreasing core defining a primary core recess;

ii) a secondary reluctance-decreasing core defining a secondary core recess and disposed adjacent the primary core;

iii) a primary electrically conductive winding disposed within the primary core recess;

iv) a secondary electrically conductive winding disposed within the secondary core recess; and

v) an electrically conductive shield;

vi) wherein the primary and secondary cores are arranged so as to form a core airgap therebetween permitting relative rotation of the cores about an axis of rotation;

vii) a primary electric current flowing through the primary winding produces a secondary electric current flowing through the secondary winding, creating a fringing field at the periphery of the core airgap; and

viii) the shield is capable of substantially canceling the fringing field.

59. A system in accordance with claim 58 wherein

a) the system is a CT scanner;

b) the stationary member comprises a stationary gantry in the CT scanner; and

c) the rotatable member includes an x-ray source.