EP0029869A1

EP0029869A1 - Spider assembly for a high voltage fuse and the fuse per se

Info

Publication number: EP0029869A1
Application number: EP79302720A
Authority: EP
Inventors: William T. Huber
Original assignee: RTE Corp
Current assignee: Cooper Power Acquisition Corp
Priority date: 1979-11-29
Filing date: 1979-11-29
Publication date: 1981-06-10

Abstract

A six rib spider assembly for a high voltage fuse including a dielectric housing having end caps for supporting the spider assembly within the housing and a fusable ribbon helically wound on the spider assembly.

The spider assembly including three mica plates (20 A,B,C) each having a number of notches (42) in their longitudinal edge for the fusable ribbon. These support surfaces (40) on each longitudinal edge of each of the plates (20 A,B,C) being offset from the support surfaces (40) on the opposite longitudinal edge as well as from the support surfaces on each of the other mica plates (20A, 20B, 20C). Each of the plates (20 A,B,C) also including at least one longitudinal slot (34,36,38) intermediate the longitudinal edges of the plates (20 A,B,C), with one of the plates (20A) including a second slot (32), whereby the plates (20A,20B,20C) can be cross fitted into each other with the plates (20A,20B,20C) angularly related so that the support surfaces (40) define a helical path for the fusable ribbon.

Description

This invention relates to a spider assembly for a high voltage fuse.
Spide assemblies for supporting fusable ribbon elements have been fabricated from numerous materials mainly classified as good dielectrics either gas evolving (organic) or non-gas evolving (in-organic). It has been the general practice to use mylar (organic) and mica with in-organic binders to make four ribbed spiders. These have been fabricated with and without notches in the ribs. Ceramic spiders generally do not have notches as the cost of producing them is prohibitive. Efforts to increase the number of ribs to six have been limited due to the additional cost and the difficulty of extruding a six rib structure and the cost of cutting notches in the ribs.
According to the present invention there is provided a spider assembly to support a fusable ribbon to be mounted within a housing which contains a granular dielectric material, comprising a number of plates (20) having support surfaces (40) along their longitudinal edges, each support surface (40) on each plate (20A) being offset with respect to each other (40) and with respect to the support surfaces (40) on the other plates (20B,20C), each plate (20) including at least one longitudinal slot (32,34,36,38) intermediate the longitudinal edges of the plates (20) whereby the plates (20) can be cross fitted into each other with the plates (20) being angularly related so that the support surfaces (40) define a helical path for the fusable ribbon (26).
This arrangement provides a more circular circum- _ference and an increased ribbon length for the same length spider.
In the preferred embodiment notches (42) are provided in the longitudinal edges of the plate (20) between each pair of support surfaces (40) whereby dielectric material (28) in the notches (42) will insulate the turns of the ribbon (28) from each other.
According to a further aspect of the invention, there is provided a high voltage fuse comprising a cylindrical housing (12), a granular dielectric material (28) in said housing (12) and a spider assembly (10) imbedded in said dielectric material (28), said spider assembly (10) including three mica plates (20) of substantially equal length, each plate (20) to form six ribs and fuse means (26) supported on the longitudinal edges (40) of said ribs.
Embodiments of the invention will now be described, by way of examply only, with reference to the accompanying drawings, in which:-

Figure 1 is an elevation view partly broken away to show the spider assembly supporting a dual range fusable ribbon within a fuse housing;
Figure 2 is a view of the spider assembly with the fusable ribbon helically would on the support surfaces;
Figure 3 is an end view of one end of the spider assembly shown in Figure 2;
Figure 4 is an end view of the other end of the spider assembly shown in Figure 2;
Figure 5 is a plan view of one of the spider plates;
Figure 6 is a plan view of the second spider plate; and,
Figure 7 is a plan view of the third spider plate.

Referring to Figure 1 of the drawing, the spider assembly according to one embodiment of the invention is shown mounted in a cylindrical insulating housing (12) and supported therein by an end cap assembly (14) provided on each end of the housing (12). The cylindrical housing is generally formed from a suitable dielectric material such as a plastic resin. The end cap assemblies each include a metallic cap (16) which is mounted over the end of the cylindrical housing and has a circuit connecting member (18) provided on each end cap. The end caps are sealed to the housing in a conventional manner.
Referring to Figures 2, 3 and 4 the spider assembly (10) includes a number of flat support plates (20) which are closely fitted together and held in a fixed relation with respect to each other by conductive metallic plates (22 & 24). The plates (22 & 24) are provided at each end of the support plates (20). A pair of fusable ribbons (26) are shown helically wound about the outer edges of the support plates (20) and soldered to the metallic plates (22 & 24) at each end of the fusable ribbon.
The cylindrical housing (12) can be filled with a suitable granular dielectric material (28) such as silica sand or coarse sand which entirely surroundsthe fusable ribbon (26). The fusable ribbons are fabricated from silver, although other alloys are usable, and dimensioned to melt when a predetermined magnitude of current is conducted through the ribbon. The ribbons are insulated by the dielectric material (28).
A second fusable element assembly (30) can be provided on the end of the fusable ribbons if a full range fuse is desired.
Referring to Figures 5, 6 and 7 the support plates (20) are shown and individually numbered 20A, 20B and 20C. Each plate is in the form of a flat sheet like member formed of a suitable dielectric material such as mica paper. Slot means are provided in each of the plates to allow the plates to becross fitted to form the spider assembly for the fusable ribbon.
In this regard the plate 20A is provided with a pair of slots 32 and 34 of unequal length located intermediate the longitudinal edges of the plate 20A. The plate 20B includes a longitudinal slot 36 intermediate the longitudinal edges of plate 20B. The plate 20C includes a longitudinal slot 38 intermediate the longitudinal edges of the plate 20C.
It should also be noted that each of the plates includes a number of support surfaces 40 along each of their longitudinal edges. The support surfaces being separated by means of notches 42. In this preferred embodiment, the support surfaces 40 are equally spaced along each longitudinal edge with the support surfaces on each longitudinal edge being offset with respect to each other and also offset with respect to the support surfaces 40 provided on each of the other plates (20B and 20C).
The spider assembly is formed by cross fitting the slot 36 in plate 20B with the slot 32 in plate 20A and the slot 38 in plate 20C with the slots 34 in plate 20A and 36 in plate 20B. The combined length of the slots 32 and 36 should be equal to the length of one of the plates 20. The combined length of the slots 34 and 38 also should be equal to the length of one of the plates 20.
The plates 20 of the spider assembly are held in a predetermined angular relation i.e. 120 degrees, by means of the metallic terminator plates 22 and 24. In this regard each of the terminator plates includes a central aperture 44 with a plurality of notches 46 located 60 degrees apart to accommodate ends of the plates 20.
The fusable ribbons 26 and the second fusable assemblies 30 are helically wrapped around the support surfaces 40. Since each plate 20 is shaped different in that the support surfaces are offset with respect to each other, a predetermined pitch can be provided for the fusable ribbon 26 as they are helically wound about the assembled plates 20.
After assembly the spider assembly 10 is positioned in the cylindrical housing 12 with the metallic terminator plates 22 and 24 secured to the end caps 16. The housing 12 is then filled with the granular dielectric material 28. It should be noted that the granular material will fill the notches 42 between the support surfaces 40 thus providing insulating material between the turns of the fusable ribbons mounted on the support surfaces 40. The use of six ribs provides a greater circular circumference and thus an increased length for the fusable ribbons for the same length spider assembly.

Claims

1. A spider assembly to support a fusable ribbon to be mounted within a housing which contains a granular dielectric material, comprising a number of plates (20) having support surfaces (40) along their longitudinal edges, each support surface (40) on each plate (20A) being offset with respect to each other (40) and with respect to the support surfaces (40) on the other plates (20B, 20C), each plate (20) including at least one longitudinal slot (32,34,36,38) intermediate the longitudinal edges of the plates (20) whereby the plates (20) can be cross fitted into each other with the plates (20) being angularly related so that the support surfaces (40) define a helical path for the fusable ribbon (26).

2. A spider assembly as claimed in claim 1, wherein notches (42) are provided in the longitudinal edges of the plate (20) between each pair of support surfaces (40) whereby dielectric material (28) in the notches (42) will insulate the turns of the ribbon (28) from each other.

3. A spider assembly as claimed in claim 2 wherein the support surfaces (40) on each longitudinal edge of each plate (20) are equally spaced from the adjacent support surface (40).

4. A spider assembly as claimed in any one of claims 1 to 3, including means (22,24) at each end of the spider assembly for maintaining the plates (20) in a fixed angular relation.

5. A spider assembly as claimed in claim 4, wherein said plates (20) are spaced to provide ribs at 60 degree intervals.

6. A spider assembly as claimed in any one of claims 1 to 5, wherein one of said plates (20) includes a second longitudinal slot (32) at the opposite end of the plate (20) from the first longitudinal slot (34).

7. A spider assembly as claimed in claim 6, wherein said plates (20) are of equal length and the combined length of the first slot (34) in said one of the plates (20A) and the slot (38) in one of the other plates (20C) is equal to the length of one of the plates (20) and the combined length of the second slot (32) in said one of said plates (20A) and the length of the slot (36) in the other of said plates (20B) is equal to the length of one of the plates (20).

8. A high voltage fuse comprising a cylindrical housing (12), a granular dielectric material (28) in said housing (12) and a spider assembly (10) imbedded in said dielectric material (28), said spider assembly (10) including three mica plates (20) of substantially equal length, each plate (20) being slotted to cross fit with the other plates (20) to form six ribs and fuse means (26) supported on the longitudinal edges (40) of said ribs.

9. A fuse as claimed in claim 8 including means (22, 24) at each end of a cylindrical housing (12) for supporting the spider assembly (10) within the housing (12).

10. A fuse as claimed in either claim 8 or claim 9, wherein each of said plates (20) includes a plurality of notches on the longitudinal edges (40) of said ribs to form a plurality of support surfaces (40) for said fuse means (28).

11. A fuse as claimed in claim 10, wherein said notches are equally spaced and offset from each other so that the support surfaces (40) define a helical path for the aforesaid fuse means (28).

12. A fuse as claimed in any one of claims 8 to 11, wherein each of said plates (20A,20B, 20C) includes a first slot (34,36,38) and one of said plates (20A) includes a second slot (32), the slots (32,34,36,38) being located intermediate the longitudinal edges (40) of the plates (20).

13. A fuse as claimed in claim 12, wherein the combined length of the second slot (32) in one of said plates (20A) and the first slot (36) in one of said other plates (20B) is equal to the length of a plate, and the combined length of the first slot (34) in said of one of said plates (20A) and the first slot (38) in the other of said plates (20C) is equal to the length of a plate.