Permanent magnet generator providing alternating current which has a selected frequency

• US 5,874,797 A
• Filed: 09/08/1997
• Issued: 02/23/1999
• Est. Priority Date: 12/10/1996
• Status: Expired due to Fees

• Current Assignee: Active Power Incorporated
• Original Assignee: Active Power Incorporated
• Inventors: Pinkerton, Joseph F.
• Primary Examiner(s): Ramirez, Nestor
• Assistant Examiner(s): ENAD, ELVIN GENARGUE
• Application Number:
  US08/925,078
• Time in Patent Office: 533 Days
• Field of Search: 310/114, 310/121, 310/156, 310/112, 310/113, 322/10, 322/51, 290/6, 318/732
• US Class Current: 310/156.25
• CPC Class Codes: H02K 21/024 Radial air gap machines
• CPC Class Codes: H02K 2201/12 Transversal flux machines
• CPC Class Codes: H02K 35/04 with moving coil systems and stationary magnets
• CPC Class Codes: H02K 7/025 for power storage
• CPC Class Codes: H02P 9/42 to obtain desired frequency without varying speed of the generator
• CPC Class Codes: Y02E 60/16 Mechanical energy storage, e.g. flywheels or pressurised fluids

Abstract

An electrical generator has at least one rotating ring of field magnets which produce a circular array of magnetic fields, and a ring of generator output coils which are in the magnetic fields. The field magnets are permanent magnets. The generator output coils are movable in a displacement path toward and away from a null position at which they are exposed to zero net flux from the magnetic fields. Movement of the coils by an actuator varies the amplitude of the voltage induced in these coils by the rotating field magnets. The actuator is energized by an alternating current to create a mechanical oscillation of the generator output coils in their displacement path. The coils provide a raw amplitude-modulated signal that has a carrier frequency which is a function of the rotational velocity of the field magnets and a modulation frequency that is proportional to the mechanical oscillation of the generator output coils. The raw output signal is fed to a signal processor which converts it to a final output signal, the frequency of which is equal to the modulation frequency.

Claims

1. A permanent magnet generator for providing alternating current which has a selected frequency comprising:

a loop assembly and a magnet assembly, one of which is rotatable relative to the other said assembly;

said magnet assembly provided with at least one ring of field magnets which are arranged to provide a circular array of magnetic fields which vary in magnitude from one circumferential position to another;

said loop assembly provided with at least one ring of electrically conductive output loops which are in said magnetic fields and occupy different circumferential positions on the loop assembly, at least a portion of said loop assembly being movable along a displacement path in said magnetic fields to change the position of said output loops with respect to said magnetic fields independently of the relative rotation between said magnet assembly and said loop assembly;

actuator means for providing displacement movement which gives said loop assembly an oscillatory motion having a mechanical oscillation frequency along said displacement path, said mechanical oscillation frequency corresponding to said selected frequency, said rotary motion and said oscillatory motion providing in said loop assembly a raw amplitude-modulated output signal having an amplitude which is modulated as a function of the displacement of said loop assembly and a induced current frequency which is a function of the rotary motion, said induced current frequency being higher than said mechanical oscillation frequency;

a signal processor for converting said raw output signal to an alternating current signal which has said mechanical oscillation frequency.

2. A permanent magnet generator according to claim 1 wherein said loops have nonmagnetic cores.

3. A permanent magnet generator according to claim 1 having a drive means for rotating said magnet assembly.

4. A permanent magnet generator according to claim 1 wherein said magnet assembly is rotatably supported and said loop assembly is supported for said displacement movement.

5. A permanent magnet generator according to claim 1 wherein said displacement path includes a null position where said loops are exposed to zero net flux during relative rotation between said magnet assembly and said loop assembly.

6. A permanent magnet generator according to claim 5 wherein said oscillatory movement includes excursions on opposite sides of said null position.

7. A permanent magnet generator according to claim 5 wherein the loop assembly is movable to said null position.

8. A permanent magnet generator according to claim 1 wherein said induced current frequency is at least about ten times said mechanical oscillation frequency.

9. A permanent magnet generator according to claim 1 wherein said signal processor includes at least four diodes.

10. A permanent magnet generator according to claim 1 wherein said signal processor includes at least four thyristors.

11. A permanent magnet generator according to claim 1 wherein the signal processor includes a bridge formed of semiconductor switches.

12. A permanent magnet generator according to claim 11 wherein said switches comprise at least four thyristors.

13. A permanent magnet generator according to claim 11 wherein said switches comprise at least four diodes.

14. A permanent magnet generator according to claim 11 wherein the state of the bridge is changed when the raw generator output signal has a zero voltage crossing to convert the raw output signal to an alternating current signal which has said mechanical oscillation frequency.

15. A permanent magnet generator according to claim 11 wherein the signal processor includes a capacitor which smooths the bridge output to provide said alternating current signal which is substantially a sine wave.

16. A permanent magnet generator according to claim 11 wherein the signal processor includes a inductor which smooths the bridge output to provide said alternating current signal which is substantially a sine wave.

17. A permanent magnet generator according to claim 1 wherein the signal processor includes a full wave rectifier for providing a signal which has identical adjacent half-waves, and an inverter circuit for reversing alternate half-waves to provide an alternating current output signal.

18. A permanent magnet generator according to claim 11 wherein the signal processor includes a full wave rectifier which produces at its output a signal in the form of a sine wave which does not cross an axis which represents zero voltage, a transformer which has primary windings connected to the output of said rectifier, said transformer having secondary windings which provide said alternating current signal which has said mechanical oscillation frequency.

19. A permanent magnet generator according to claim 1 wherein the magnet assembly has a first ring of field magnets and a second ring of field magnets, said first and second rings being concentric and being axially offset from each other, said loop assembly having loops which each lie in the magnetic fields of both rings of field magnets, said displacement movement being in an axial direction to vary the proportion of each loop which is exposed to the magnetic fields of the first ring and the magnetic fields of the second ring.

20. A permanent magnet generator according to claim 19 wherein the actuator means includes at least one ring of actuator loops which lie in said magnetic fields of said magnet assembly.

21. A permanent magnet generator according to claim 19 wherein the actuator means includes a first ring of actuator loops which lie in the magnetic fields of said first ring of field magnets, and a second ring of actuator loops which lie in the magnetic fields of the second ring of field magnets, said first and second rings of actuator loops being fixed with respect to said loop assembly so that a current induced in said actuator loops by a said magnetic field produces Lorentz forces which move said loop assembly axially.

22. A permanent magnet generator according to claim 19 wherein the actuator means includes a ring of actuator loops which lie in the magnetic fields of both the first ring of magnets and the second ring of magnets, said ring of actuator loops being fixed with respect to said loop assembly so that current flowing in said actuator loops produces Lorentz forces which move said loop assembly axially.

23. A permanent magnet generator according to claim 22 wherein a said ring of output loops and a said ring of said actuator loops have a same diameter and form an output/actuator ring in which said actuator loops are located between said output loops.

24. A permanent magnet generator according to claim 23 having two of said output/actuator rings which both lie in the magnetic fields of the first and second rings of magnets.

25. A permanent magnet generator according to claim 1 wherein the magnet assembly includes a first ring of field magnets, and a second ring of field magnets which is axially spaced from said first ring of field magnets, said loop assembly having a first ring of loops and a second ring of loops, said first ring of loops lying in the magnetic fields of the first ring of field magnets, said second ring of loops lying in the magnetic fields of the second ring of field magnets, said loops of the first ring being electrically connected to the loops of the second ring to provide said raw output signal.

26. A permanent magnet generator according to claim 1 wherein the loop assembly has a first ring of loops and a second ring of loops, said first and second rings of loops being concentric, said displacement movement being an angular movement of said first ring of loops which varies the relative angular position between the loops of the first ring and the loops of the second ring, said loops of the first ring being electrically connected to the loops of the second ring to provide said raw output signal.

27. A permanent magnet generator according to claim 26 wherein the first and second rings overlap so as to be simultaneously exposed to said magnetic fields.

28. A permanent magnet generator according to claim 26 wherein there is a first said ring of field magnets which provide magnetic fields to said first ring of loops, and a second said ring of field magnets which provide magnetic fields to said second ring of loops.

29. A permanent magnet generator according to claim 1 wherein the field magnets each have a polarity which is opposite to that of an adjacent field magnet, whereby adjacent magnetic fields are oppositely directed.

30. A permanent magnet generator according to claim 29 wherein said adjacent field magnet is a circumferentially adjacent field magnet.

31. A permanent magnet generator according to claim 29 wherein said adjacent field magnet is an axially adjacent field magnet.

32. A permanent magnet generator according to claim 29 wherein said adjacent field magnet is a radially adjacent field magnet.

33. A permanent magnet generator according to claim 1 wherein one of said assemblies is rotatable about an axis of rotation, said generator having, in said magnetic fields, a body which is capable of being attracted by a magnet, said body being spaced from said field magnets to define a gap which lies between the field magnets and the body, said output loops being located in said gap.

34. A permanent magnet generator according to claim 33 wherein said gap has a thickness which is less than one-fifth the distance between the axis of rotation and the center of an output loop which is in said gap.

35. A permanent magnet generator according to claim 33 wherein said output loops have nonmagnetic cores.

36. A permanent magnet generator according to claim 1 wherein the actuator means includes at least one actuator loop which lies in one or more magnetic fields, said generator having means for controlling the flow of current in said actuator loop to control Lorentz forces which move the loop assembly in said displacement path.

37. A permanent magnet generator according to claim 1 wherein there is a first ring of said field magnets and a second ring of said field magnets, said second ring of field magnets being axially offset with respect to said first ring of field magnets, said field magnets being positioned to provide radially directed magnetic fields, said displacement path being an axial displacement path which changes the positions of the output loops to increase the exposure of the output loops to the magnetic fields from said first ring of field magnets and to decrease the exposure of the output loops to said second ring of field magnets.

38. A permanent magnet generator according to claim 1 wherein said field magnets are positioned to provide axially directed magnetic fields, said generator having a first ring of said field magnets and a second ring of said field magnets, said first ring of said field magnets being radially spaced from said second ring of said field magnets, each of said output loops being in said magnetic fields from both of said rings of field magnets, said displacement path being a radial displacement path which changes the positions of the output loops to increase the exposure of one said output loop to the magnetic fields from the first ring of field magnets and decrease the exposure of said one output loop to the magnetic fields from the second ring of field magnets.

39. A permanent magnet generator according to claim 1 wherein there is a first ring of output loops and a second ring of output loops, said first and second rings of output loops being located in magnetic fields emanating from one said ring of field magnets, said displacement movement being an angular movement of the first ring of output loops relative to the second ring of output loops to change the positions of said output loops relative to the magnetic fields and provide a difference in phasing between voltages induced in the first and second rings of output loops.

40. A permanent magnet generator according to claim 1 wherein the actuator means includes an electrical conductor located in a magnetic field, and means for providing a flow of electrical current in said conductor to produce Lorentz forces which move the loop assembly in said displacement path.

41. A permanent magnet generator according to claim 1 having a plurality of flexible members which support and guide said loop assembly, each of said flexible members having a stationary portion and a movable portion, said movable portions being fixed relative to said loop assembly and being movable parallel to said displacement path.

42. A permanent magnet generator according to claim 41 wherein said flexible members are resilient and are operable to bias said loop assembly to a given position.

43. A permanent magnet generator according to claim 41 wherein said flexible members are diaphragms which are spaced axially from each other to support and guide said loop assembly for movement in an axial direction.

44. A permanent magnet generator according to claim 43 wherein said diaphragms are parallel to each other.

45. A permanent magnet generator according to claim 41 wherein the flexible members have their movable portions spaced axially from their stationary portions to support said loop assembly for angular movement, said flexible members being circumferentially spaced from each other.

46. A permanent magnet generator according to claim 45 wherein said flexible members are inflexible in a radial direction and flexible in a circumferential direction.

47. A permanent magnet generator for providing alternating current which has a selected frequency comprising:

a loop assembly and a magnet assembly, one of which is rotatable relative to the other said assembly about an axis of rotation;

said magnet assembly provided with at least one ring of field magnets which are arranged to provide a circular array of magnetic fields which vary in magnitude from one circumferential position to another said loop assembly provided with at least one ring of electrically conductive output loops which are in said magnetic fields and occupy different circumferential positions on the loop assembly, at least a portion of said loop assembly being movable along a displacement path in said magnetic fields to change the position of said output loops with respect to said magnetic fields independently of the relative rotation between said magnet assembly and said loop assembly;

actuator means for providing displacement movement which gives said loop assembly an oscillatory motion having a mechanical oscillation frequency along said displacement path, said mechanical oscillation frequency corresponding to said selected frequency, said rotary motion and said oscillatory motion providing in said loop assembly a raw amplitude-modulated output signal having an amplitude which is modulated as a function of the displacement of said loop assembly and a induced current frequency which is a function of the rotary motion, said induced current frequency being higher than said mechanical oscillation frequency;

said actuator means including an electrical conductor located in a magnetic field, and means for providing a flow of electrical current in said electrical conductor to produce Lorentz forces which move the loop assembly in said displacement path;

a signal processor for converting said raw output signal to an alternating current signal which has said mechanical oscillation frequency.

48. A permanent magnet generator according to claim 47 wherein said magnet assembly is rotatably supported and said loop assembly is supported for said displacement movement.

49. A permanent magnet generator according to claim 47 wherein said electrical conductor is located in a magnetic field which extends in a radial direction, and the electrical conductor is a loop which is spaced from the axis of rotation.

50. A permanent magnet generator according to claim 47 wherein said electrical conductor is located in a magnetic field which extends in an axial direction, and the electrical conductor is a loop which is spaced from the axis of rotation.

51. A permanent magnet generator according to claim 47 wherein the electrical conductor is a loop which is concentric with the axis of rotation.

52. A permanent magnet generator for providing alternating current which has a selected frequency comprising:

a loop assembly and a magnet assembly, one of which is rotatable relative to the other said assembly;

said magnet assembly provided with at least one ring of field magnets which are arranged to provide a circular array of magnetic fields which vary in magnitude from one circumferential position to another;

said loop assembly provided with at least one ring of electrically conductive output loops which are in said magnetic fields and occupy different circumferential positions on the loop assembly, at least a portion of said loop assembly being movable along a displacement path in said magnetic fields to change the position of said output loops with respect to said magnetic fields independently of the relative rotation between said magnet assembly and said loop assembly;

actuator means for providing displacement movement which gives said loop assembly an oscillatory motion having a mechanical oscillation frequency along said displacement path, said mechanical oscillation frequency corresponding to said selected frequency, said rotary motion and said oscillatory motion providing in said loop assembly a raw amplitude-modulated output signal having an amplitude which is modulated as a function of the displacement of said loop assembly and a induced current frequency which is a function of the rotary motion, said induced current frequency being higher than said mechanical oscillation frequency;

a plurality of flexible members which support and guide said loop assembly, each of said flexible members having a stationary portion and a movable portion, said movable portions being fixed relative to said loop assembly and being movable parallel to said displacement path;

a signal processor for converting said raw output signal to an alternating current signal which has said mechanical oscillation frequency.

53. A permanent magnet generator according to claim 52 wherein said magnet assembly is rotatably supported and said loop assembly is supported for said displacement movement.

54. A permanent magnet generator according to claim 52 wherein said flexible members are resilient and are operable to bias said loop assembly to a given position.

55. A permanent magnet generator according to claim 52 wherein said flexible members are diaphragms which are spaced axially from each other to support and guide said loop assembly for movement in an axial direction.

56. A permanent magnet generator according to claim 55 wherein said diaphragms are parallel to each other.

57. A permanent magnet generator according to claim 52 wherein the flexible members have their movable portions spaced axially from their stationary portions to support said loop assembly for angular movement, said flexible members being circumferentially spaced from each other.

58. A permanent magnet generator according to claim 57 wherein said flexible members are inflexible in a radial direction and flexible in a circumferential direction.