Mechanical reinforcement to improve high current, short duration withstand of a monolithic disk or bonded disk stack

• US 7,015,786 B2
• Filed: 08/29/2001
• Issued: 03/21/2006
• Est. Priority Date: 08/29/2001
• Status: Expired due to Term

• Current Assignee: Eaton Intelligent Power Limited (Eaton Corporation PLC.)
• Original Assignee: Mcgraw-Edison Company (Eaton Corporation PLC.)
• Inventors: Ramarge, Michael M., Hartman, Thomas C.
• Primary Examiner(s): HOANG, TU BA
• Application Number:
  US09/940,539
• Publication Number:
  US 20030043526A1
• Time in Patent Office: 1,665 Days
• Field of Search: 338/20, 338/21, 311/127, 298/30, 298/25, 298/40, 298/46
• US Class Current: 338/20
• CPC Class Codes: H01C 7/102 Varistor boundary, e.g. surface layers H01C7/12 takes precedence
• CPC Class Codes: H01C 7/126 Means for protecting against excessive pressure or for disconnecting in case of failure

Abstract

A mechanical reinforcement for an electrical apparatus has at least one electrical element with an outer surface and a reinforcing structure attached to the outer surface. The electrical element may be a monolithic MOV disk or a bonded MOV disk stack. The monolithic element may, for example, have a rating greater than 6 kV. The reinforcing structure may be pre-impregnated fiber matrix that may be, for example, pre-impregnated with resin. The mechanical reinforcement provides improved high current durability to the electrical apparatus.

Claims

1. An electrical apparatus comprising:

two terminals accessible from an exterior of the electrical apparatus;

an electrical element comprising a monolithic MOV disk having an outer surface and two ends, the ends being in contact with the two terminals, the monolithic MOV disk having a rating of at least 6 kV; and

a reinforcing structure attached to the outer surface and constructed so as to enable the monolithic MOV disk to withstand at least one 100 kA impluse without cracking, wherein the reinforcing structure comprises a fiber matrix pre-impregnated with a resin, the fiber matrix comprising a pre-woven fabric.

2. The apparatus of claim 1 wherein the monolithic MOV disk has a rating between approximately 6 kV and approximately 800 kV.

3. The apparatus of claim 1 wherein the fibers in the fiber matrix are oriented in a predetermined orientation with respect to an axis of the electrical element.

4. The apparatus of claim 3 wherein the fibers in the fiber matrix are oriented parallel to the axis.

5. The apparatus of claim 1 wherein the fibers segments are oriented in a random orientation.

6. The apparatus of claim 1 wherein the fibers in the fiber matrix are of a uniform length.

7. The apparatus of claim 1 wherein the fibers in the fiber matrix are of a non-uniform length.

8. The apparatus of claim 1 wherein the fibers in the fiber matrix comprise fiberglass.

9. The apparatus of claim 1 wherein the fibers in the fiber matrix comprise a non-conductive material.

10. The apparatus of claim 1 wherein the fiber matrix is applied circumferentially.

11. The apparatus of claim 10 wherein the fiber matrix is applied circumferentially such that the fibers have a predetermined orientation at a predetermined angle with respect to an axis of the electrical element.

12. The apparatus of claim 11 wherein the predetermined angle is an angle less than approximately 50 degrees.

13. The apparatus of claim 12 wherein the angle is between approximately 3 degrees and approximately 10 degrees.

14. The apparatus of claim 10 wherein the circumferentially applied fiber matrix has a predetermined thickness.

15. The apparatus of claim 1 wherein the fiber matrix is applied vertically.

16. The apparatus of claim 15 wherein the vertical application comprises at least one piece of fiber matrix placed in a vertical orientation along an axis of the electrical element.

17. The apparatus of claim 15 wherein the vertical application comprises a single piece of fiber matrix placed in a vertical orientation along an axis of the electrical element and having a sufficient width to cover the majority of an outer surface of the electrical element.

18. The apparatus of claim 1 wherein the reinforcing structure further comprises at least one layer of pre-impregnated fiber matrix applied circumferentially and at least one layer of pre-impregnated fiber matrix applied vertically.

25. The apparatus of claim 1 wherein the reinforcing structure has a uniform thickness.

26. The apparatus of claim 1 wherein the reinforcing structure is configured to reinforce a selected portion of an area of the monolithic MOV disk along a lengthwise axis of the disk.

27. The apparatus of claim 26 wherein the selected portion of the area comprises less than all of the area.

28. The apparatus of claim 26 wherein the selected portion of the area comprises an area excluding the ends of the monolithic MOV disk.

29. The apparatus of claim 26 wherein the selected portion of the area comprises an area including a center of the monolithic MOV disk.

30. The apparatus of claim 3 wherein the predetermined orientation is based upon the orientation of the fabric with respect to the axis.

31. The apparatus of claim 3 wherein the predetermined orientation is based upon a woven pattern of the fibers in the pre-woven fabric.

32. The apparatus of claim 3 wherein the predetermined orientation comprises one of approximately zero degrees and approximately ninety degrees with respect to the axis.

33. The apparatus of claim 11 wherein the predetermined angle is based upon the angle of the fabric with respect to the axis.

34. The apparatus of claim 11 wherein the predetermined angle is based upon a woven pattern of the fibers in the pre-woven fabric.

35. The apparatus of claim 11 wherein the predetermined angle comprises one of approximately zero degrees and approximately ninety degrees with respect to the axis.

66. The apparatus of claim 1 wherein the monolithic MOV disk has a rating greater than 6 kV.

67. The apparatus of claim 66 wherein the monolithic MOV has a rating of 9 kV.

19. An electrical apparatus comprising:

an electrical element comprising a bonded disk stack having an outer surface, the bonded disk stack comprising two or more MOV disks, each disk having a face-to-face bond with each adjacent disk, the bonded disk stack having a rating of at least 6 kV; and

a reinforcing structure attached to the outer surface and constructed so as to enable the bonded disk stack to withstand at least one 100 kA impulse without breaking the face-to-face bonds, wherein the reinforcing structure comprises a fiber matrix pre-impregnated with a resin, the fiber matrix comprising a pre-woven fabric.

20. The apparatus of claim 19 wherein the bonded disk stack comprises more than two MOV disk.

21. The apparatus of claim 19 wherein the fibers in the fiber matrix comprise a non-conductive material.

22. The apparatus of claim 19 wherein the fiber matrix is applied circumferentially.

23. The apparatus of claim 19 wherein the fiber matrix is applied vertically.

24. The apparatus of claim 19 wherein the reinforcing structure comprises at least one layer of pre-impregnated fiber matrix applied circumferentially and at least one layer of pre-impregnated fiber matrix applied vertically.

36. The apparatus of claim 19 wherein the bonded disk stack has a rating between approximately 6 kV and approximately 800 kV.

37. The apparatus of claim 19 wherein the electrical apparatus is constructed so as to withstand at least one 100 kA impulse.

38. The apparatus of claim 19 wherein the fibers in the fiber matrix are oriented in a predetermined orientation with respect to an axis of the electrical element.

39. The apparatus of claim 38 wherein the predetermined orientation is based upon the orientation of the fabric with respect to the axis.

40. The apparatus of claim 38 wherein the predetermined orientation is based upon a woven pattern of the fibers in the pre-woven fabric.

41. The apparatus of claim 38 wherein the predetermined orientation comprises one of approximately zero degrees and approximately ninety degrees with respect to the axis.

42. The apparatus of claim 38 wherein the fibers in the fiber matrix are oriented parallel to the axis.

43. The apparatus of claim 19 wherein the fibers in the fiber matrix are of a uniform length.

44. The apparatus of claim 19 wherein the fibers in the fiber matrix are of a non-uniform length.

45. The apparatus of claim 19 wherein the fibers in the fiber matrix comprise fiberglass.

46. The apparatus of claim 19 wherein the fibers in the fiber matrix comprise a non-conductive material.

47. The apparatus of claim 19 wherein the fiber matrix is applied circumferentially.

48. The apparatus of claim 47 wherein the fiber matrix is applied circumferentially such that the fibers have a predetermined orientation at a predetermined angle with respect to an axis of the electrical element.

49. The apparatus of claim 48 wherein the predetermined angle is based upon the angle of the fabric with respect to the axis.

50. The apparatus of claim 48 wherein the predetermined angle is based upon a woven pattern of the fibers in the pre-woven fabric.

51. The apparatus of claim 48 wherein the predetermined angle comprises one of approximately zero degrees and approximately ninety degrees with respect to the axis.

52. The apparatus of claim 48 wherein the predetermined angle is an angle less than approximately 50 degrees.

53. The apparatus of claim 52 wherein the angle is between approximately 3 degrees and approximately 10 degrees.

54. The apparatus of claim 47 wherein the circumferentially applied fiber matrix has a predetermined thickness.

55. The apparatus of claim 19 wherein the fiber matrix is applied vertically.

56. The apparatus of claim 55 wherein the vertical application comprises at least one piece of fiber matrix placed in a vertical orientation along an axis of the electrical element.

57. The apparatus of claim 55 wherein the vertical application comprises a single piece of fiber matrix placed in a vertical orientation along an axis of the electrical element and having a sufficient width to cover the majority of an outer surface of the electrical element.

58. The apparatus of claim 19 wherein the reinforcing structure further comprises at least one layer of pre-impregnated fiber matrix applied circumferentially and at least one layer of pre-impregnated fiber matrix applied vertically.

59. The apparatus of claim 19 wherein the reinforcing structure has a uniform thickness.

60. The apparatus of claim 19 wherein the reinforcing structure is configured to reinforce a selected portion of an area of the bonded disk stack along a lengthwise axis of the bonded disk stack.

61. The apparatus of claim 60 wherein the selected portion of the area comprises less than all of the area.

62. The apparatus of claim 60 wherein the selected portion of the area comprises an area excluding the ends of the bonded disk stack.

63. The apparatus of claim 60 wherein the selected portion of the area comprises an area including a center of the bonded disk stack.

68. The apparatus of claim 19 wherein the bonded disk stack has a rating greater than 6 kV.

69. The apparatus of claim 68 wherein the bonded disk stack has a rating of 9 kV.

64. An electrical apparatus comprising:

an electrical element comprising a bonded disk stack having an outer surface, the bonded disk stack comprising two or more MOV disks, each disk having a face-to-face bond with each adjacent disk, the bonded disk stack having a rating of at least 6 kV; and

wherein the bond between adjacent MOV disks has a first Young'"'"'s modulus and each MOV disc has a second Young'"'"'s modulus that is at least twice as great as the first Young'"'"'s modulus.

65. The apparatus of claim 64 wherein the fibers are oriented in an arbitrary orientation.

70. The apparatus of claim 64 wherein the bonded disk stack has a rating greater than 6 kV.

71. The apparatus of claim 70 wherein the bonded disk stack has a rating of 9 kV.

72. The apparatus of claim 64, wherein the second Young'"'"'s modulus is at least ten times greater than the first Young'"'"'s modulus.