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

• US 20030043526A1
• Filed: 08/29/2001
• Published: 03/06/2003
• Est. Priority Date: 08/29/2001
• Status: Active Grant

• Current Assignee: Eaton Intelligent Power Limited (Eaton Corporation PLC.)
• Original Assignee: Cooper Technologies Company (Eaton Corporation PLC.)
• Inventors: Ramarge, Michael M., Hartman, Thomas C.
• Granted Patent: US 7,015,786 B2
• Time in Patent Office: Days
• US Class Current: 361/117
• 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; and

a reinforcing structure attached to the outer surface, wherein the reinforcing structure comprises a fiber matrix pre-impregnated with a resin.

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

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

4. The apparatus of claim 1 wherein the electrical apparatus is constructed so as to withstand at least one 100 kA impulse.

5. The apparatus of claim 1 wherein the fibers in the fiber matrix are oriented in a predetermined orientation.

6. The apparatus of claim 1 wherein the fibers in the fiber matrix are oriented parallel to an axis of the electrical element.

7. The apparatus of claim 1 wherein the fibers in the fiber matrix are oriented in a random orientation.

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

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

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

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

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

13. The apparatus of claim 12 wherein the fiber matrix is applied circumferentially such that the fibers have a predetermined orientation at a predetermined angle.

14. The apparatus of claim 13 wherein the predetermined angle is an angle less than approximately 50 degrees.

15. The apparatus of claim 14 wherein the angle is between approximately 3 degrees and approximately 10 degrees.

16. The apparatus of claim 12 wherein the circumferentially applied fiber matrix has a predetermined thickness.

17. The apparatus of claim 1 wherein the pre-impregnated fiber matrix is applied vertically.

18. The apparatus of claim 17 wherein the vertical application comprises at least one piece of fiber matrix placed in a vertical orientation along an axis of the electrical element.

19. The apparatus of claim 17 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.

20. 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.

21. The apparatus of claim 1 wherein the reinforcing structure comprises a coating of fiber segments embedded in an epoxy.

22. An electrical apparatus comprising:

an electrical element comprising a bonded disk stack having an outer surface; and

a reinforcing structure attached to the outer surface, wherein the reinforcing structure comprises a fiber matrix pre-impregnated with a resin.

23. The apparatus of claim 22 wherein the disk stack comprises more than one MOV disk.

24. The apparatus of claim 22 wherein the fibers in the fiber matrix comprise a non-conductive material.

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

26. The apparatus of claim 22 wherein the pre-impregnated fiber matrix is applied vertically.

27. The apparatus of claim 22 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.

28. A method of reinforcing an electrical apparatus, the method comprising:

providing at least one electrical element comprising a monolithic MOV disk having an outer surface and two ends, each end being in contact with a terminal accessible from an exterior of the electrical apparatus;

preparing a reinforcing layer for application to the outer surface of the electrical element, wherein the reinforcing layer comprises a fiber matrix pre-impregnated with resin; and

applying the reinforcing layer to at least a portion of the outer surface of the at least one electrical element.

29. The method of claim 28 wherein the monolithic MOV disk has a rating greater than 6 kV.

30. The method of claim 28 wherein the monolithic MOV disk has a rating between approximately 6 kV and approximately 800 kV.

31. The method of claim 28 wherein the electrical apparatus is constructed so as to withstand at least one 100 kA impulse.

32. The method of claim 28 wherein applying the reinforcing layer comprises circumferentially applying a pre-impregnated fiber matrix.

33. The method of claim 28 wherein applying the reinforcing layer comprises vertically applying a pre-impregnated fiber matrix.

34. The method of claim 28 further comprising performing post application processing of the reinforcing layer.

35. The method of claim 34 wherein performing post application processing comprises curing.

36. The method of claim 28 further comprising heating the element.

37. The method of claim 36 wherein the element is heated between approximately 100°

F. and 200°

F.

38. The method of claim 35 wherein curing the reinforcing layer comprises heating the reinforcing layer.

39. The method of claim 38 wherein the reinforced layer is heated to between approximately 250°

F. and 400°

F.

40. A method of reinforcing an electrical apparatus, the method comprising:

providing at least one electrical element comprising a bonded disk stack having an outer surface;

preparing a reinforcing layer for application to the outer surface of the electrical element, wherein the reinforcing layer comprises a fiber matrix pre-impregnated with resin; and

applying the reinforcing layer to at least a portion of the outer surface of the at least one electrical element.

41. The method of claim 40 wherein applying the reinforcing layer comprises circumferentially applying a pre-impregnated fiber matrix.

42. The method of claim 40 wherein applying the reinforcing layer comprises vertically applying a pre-impregnated fiber matrix.

43. The method of claim 40 further comprising performing post application processing of the reinforcing layer.

44. The method of claim 40 wherein performing post application processing comprises curing.

45. A method of reinforcing an electrical apparatus, the method comprising:

providing at least one electrical element comprising a monolithic MOV disk having an outer surface and two ends, each end being in contact with a terminal that is accessible from an exterior of the electrical apparatus;

preparing a reinforcing layer for application to the outer surface of the electrical element, wherein the reinforcing layer comprises a fiber matrix having a mixture of fiber segments pre-impregnated with resin; and

applying the reinforcing layer to at least a portion of the outer surface of the at least one electrical element.

46. The method of claim 45 wherein applying the reinforcing layer comprises coating the element by dipping the element in the mixture of fiber segments and resin.

47. The method of claim 45 wherein applying the reinforcing layer comprises coating the element by casting in a pre-impregnated fiber matrix.

48. The method of claim 45 wherein applying the reinforcing layer comprises coating the element by powder coating in a fiber matrix.

49. The method of claim 45 wherein applying the reinforcing layer comprises coating the element in a fiber matrix.

50. A method of reinforcing an electrical apparatus, the method comprising:

providing at least one electrical element comprising a bonded disk stack having an outer surface;

preparing a reinforcing layer for application to the outer surface of the electrical element, wherein the reinforcing layer comprises a fiber matrix having a mixture of fiber segments pre-impregnated with resin; and

applying the reinforcing layer to at least a portion of the outer surface of the at least one electrical element.

51. The method of claim 50 wherein applying the reinforcing layer comprises coating the element by dipping the element in the mixture of fiber segments and resin.

52. The method of claim 50 wherein applying the reinforcing layer comprises coating the element by casting in a pre-impregnated fiber matrix.

53. The method of claim 50 wherein applying the reinforcing layer comprises coating the element by powder coating in a fiber matrix.

54. The method of claim 50 wherein applying the reinforcing layer comprises coating the element in a fiber matrix.