CA1181788A - Low current clearing back-up fuse - Google Patents
Low current clearing back-up fuseInfo
- Publication number
- CA1181788A CA1181788A CA000452137A CA452137A CA1181788A CA 1181788 A CA1181788 A CA 1181788A CA 000452137 A CA000452137 A CA 000452137A CA 452137 A CA452137 A CA 452137A CA 1181788 A CA1181788 A CA 1181788A
- Authority
- CA
- Canada
- Prior art keywords
- fuse
- assembly
- spider
- striker pin
- elements
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Abstract
ABSTRACT OF THE DISCLOSURE
An energy-limiting fuse having a number of fuse elements spirally wrapped about a spider formed from a number of insulating plates, the fuse elements being supported in a parallel spaced relation at a distance sufficient for each element to operate independently and a striker pin assembly independently mounted in said fuse after said spider assembly has been mounted in said fuse, said striker pin assembly including a vaporizable wire for holding the striker pin in said striker pin assembly until the fuse elements are vaporized.
An energy-limiting fuse having a number of fuse elements spirally wrapped about a spider formed from a number of insulating plates, the fuse elements being supported in a parallel spaced relation at a distance sufficient for each element to operate independently and a striker pin assembly independently mounted in said fuse after said spider assembly has been mounted in said fuse, said striker pin assembly including a vaporizable wire for holding the striker pin in said striker pin assembly until the fuse elements are vaporized.
Description
'7~3~
1 ThiS ~ppllcat;on is a divislon of appllcation serlal numher 406,192 flled June 29, 1982.
BACKGROUND O~ TEIE INVENTION
Energy-limiting fuses have been supplied for many years for clearing fault currents in -the region from 300 or 400 amperes to 50,000 and more amperes in one second or less. These fuses have difEiculty in clearing smaller fault currents. To enhance fuse performance in the low current area series elements specially designed for low current clearing have been utilized alone or in combination.
These elements include ~-spots, auxiliary arcing elements, series integral e~pulsion sections, explosive charges, specialized alloys, gas-evolving spiders, and the like.
However, all of these elements require additional cost and increase the complexity of the fuse.
Fuse manufacturers have also supplied blown fuse indicators with the energy-limiting fuses. These indicators typically include a strain wire running in parallel with the main fuse elements. The strain wire ~ is solidly connected by soldering, brasing, crimping, or winding the strain wire around the lead of the indicator.
This type o solid connection makes handling of the striker pin assembly more difficult since the striker pin assembly is mounted on the spider assembly prior to incorporation of the spider assembly into the fuse. The striker pin assembly is exposed to damage in handling, requiring additional protective noses or guides, requires placing the strain wire through constricted openings, and requires that the entire s-trikex pin assembly be pushed through the lenyth o the insulated housing of the fuse.
7i 31~3 ~ Sll~ RY OP TIIF INV~NTION
- The energy-limi-ting fuse according -to -the presen-t inven-tion provicles low curren-t clearing without -the addition of any auxiliary elements. In this regard the wires which m~ke up the normal fuse element are arranged in a widely spaced relation relative to each other so that each wire acts independently of the other wires in the fuse element. A fuse designed to carry 63 amperes continuously may be composed of three elements. If a single element si~ed to carry 63 amperes is used the element could not interrupt less than 500 or 600 amperes. If two or three elements are used spaced closely together in groups, intragroup flash-overs occur so that the three elements function only slightly better than a single element. By using widely separate elements, the chance of flash-over is greatly reduced.
In effect each element functions as a single fuse in parallel with the others. Using the sample above, there are in effect three 21 ampere fuses in parallel. Each would be capable of interrupting down to 150 to 200 amperes.
By commutating, dividing the current between each of the elements and switching the current back and forth, each element functions independently creating more arc points, spreading out the heat of the arc, creating more cathode anode drops and allowing the fuse as a whole to clear the relatively low and mid-range currents. The spacing and control of the placement of the wires ensures that there will be no wire-to-wire flash-over causing shorting of the current, increasing the duty and causing the failure to clear.
1 A blown fuse indica-tor is combined with the present energy-limitlng fuse -to accomplish the required function of clearing fault curren-ts while holding -the interrupting duty imposed on associated equipment -to a point which the associated equipment can easily handle.
This is in comparison to the existing high current clearing short time melt backup fuse ~which requires 300 to 600 or more amperes before they relia~ly clearl. These currents are in excess of the duty of many of the associated switches.
I'he indicator is partially mounted in a recess in the spider allowing for a longer striker pin with a corresponding wider selection of spring forces and travel distances.
IN THE DRAWINGS
Figure 1 is a section view of the fuse according to the present invention.
Figure 2 i5 an enlarged view of a portion of Figure 1 showing the striker pin assembly.
- Figure 3 is a view taken on line 3-3 of Figure 1 showing a cross-section of the spider and striker pin assembly.
Figure 4 is a view taken on line 4-4 of Figure 1 showing the strain wire wound on the spider.
Figure 5 is a view taken on line 5-5 of Figure 1 showing the spider and one of the fuse wires.
Figure 6 is a perspective view of the striker pin assembly.
Figure 7 is a cross-section view of the striker pin assembly shown in the retracted pin posi-tion~
Figure 8 is a view of the striker pin assembly in the extended position, ~ 3 -7~
1 Figur~ ~ is a view taken on line 9-9 oE Figure 7 showing the strain wire passing through the s-triker pin.
DESCRIPTION OF THE INVENTION
The energy-limitiny ~use 10 as seen in Figure 1 generally includes a tubular housing 12, a spider assembly 14 and a striker pin assembly 16. The tubular housing 12 is closed at each end by means of electrically conductive terminal caps 18 and 20. The electrical fuse circuit between the end caps 18 and 20 is completed by means of a number of fuse elements 22 provided on the spider assembly 14. The housing is filled with a granular dielectric material 24 such as silica sand. Each of the fuse elements 22 acts independently in response to fault currents to clear the circuit between the end caps 18 and 20.
The striker pin assembly 16 is an independent unit which is mounted within the fuse 10 after the fuse has been assembled. The striker pin assembly is activated by means of a strain wire 26 provided on the spider assembly. Whenever a fault conditi.on occurs that fuses the elements 22/ all of the fault current will pass through the strain wire 26 to actuate the striker pin assembly 16.
SPIDER ASSEMBLY
More particularly and referring to Figures 1 through 4, the spider assembly 14 generally includes three electrically insulating mica plates 28 held together at each end by means of conductive end plates 30. The mica plates can be of the type shown in the Canadian Patent No. 1,108,671 issued September 8, 1981 to applicant (W.J. Huber, Inventor) Eor "Spider Assembly for a High Voltage Fuse". ~lowever, each mica plate 28 .includes a 1 plurality of tabs 32 alony each edge. The tabs on each plate are offsQt from the tabs on the opposite edge of -the plate and from the tabs on adjacent pla-tes to form a spiral suppor-t for the fuse elements 22. The fuse elements 22 are held in a constrained spaced relation on the spider assembly by means of notches 34 provided at the outer end of each of the tabs 32. The space between the notches is four to five times the width of the fuse elements 22 to prevent flash-over be~ween the elements during fault cu.rrent condition.
Two or more ~use elements can be.provided on -the spider a.ssembl~ in accordance with the rated capacity of the fuse. Each fuse element is individually ox independently connected to a tab 36 provided on the plates 30. The spider assembly is positioned within the housing 12 with the end plates 30 connected to the caps 18 and 20 by means of a con-ductive :lead 38.
Each of the mica plates 28 is provided with means at one end to accommodate the striker pin assembly 16.
~ Such means is in the form of a notch or groove 39 at one encl of each of the mica plates which define a recess for a portion of the spider assembly. The striker pin assembly is connected to the strain wire 26 by means of a conrector 40 provided at the inner end of the notches 39 ~Figure 2).
The circult through the striker pin assembly to cap 20 is completed by means of the strain wire 26~
STRIKER PIN ASSF,MBLY
The striker pin assembly 16, as seen in Figures 1,
1 ThiS ~ppllcat;on is a divislon of appllcation serlal numher 406,192 flled June 29, 1982.
BACKGROUND O~ TEIE INVENTION
Energy-limiting fuses have been supplied for many years for clearing fault currents in -the region from 300 or 400 amperes to 50,000 and more amperes in one second or less. These fuses have difEiculty in clearing smaller fault currents. To enhance fuse performance in the low current area series elements specially designed for low current clearing have been utilized alone or in combination.
These elements include ~-spots, auxiliary arcing elements, series integral e~pulsion sections, explosive charges, specialized alloys, gas-evolving spiders, and the like.
However, all of these elements require additional cost and increase the complexity of the fuse.
Fuse manufacturers have also supplied blown fuse indicators with the energy-limiting fuses. These indicators typically include a strain wire running in parallel with the main fuse elements. The strain wire ~ is solidly connected by soldering, brasing, crimping, or winding the strain wire around the lead of the indicator.
This type o solid connection makes handling of the striker pin assembly more difficult since the striker pin assembly is mounted on the spider assembly prior to incorporation of the spider assembly into the fuse. The striker pin assembly is exposed to damage in handling, requiring additional protective noses or guides, requires placing the strain wire through constricted openings, and requires that the entire s-trikex pin assembly be pushed through the lenyth o the insulated housing of the fuse.
7i 31~3 ~ Sll~ RY OP TIIF INV~NTION
- The energy-limi-ting fuse according -to -the presen-t inven-tion provicles low curren-t clearing without -the addition of any auxiliary elements. In this regard the wires which m~ke up the normal fuse element are arranged in a widely spaced relation relative to each other so that each wire acts independently of the other wires in the fuse element. A fuse designed to carry 63 amperes continuously may be composed of three elements. If a single element si~ed to carry 63 amperes is used the element could not interrupt less than 500 or 600 amperes. If two or three elements are used spaced closely together in groups, intragroup flash-overs occur so that the three elements function only slightly better than a single element. By using widely separate elements, the chance of flash-over is greatly reduced.
In effect each element functions as a single fuse in parallel with the others. Using the sample above, there are in effect three 21 ampere fuses in parallel. Each would be capable of interrupting down to 150 to 200 amperes.
By commutating, dividing the current between each of the elements and switching the current back and forth, each element functions independently creating more arc points, spreading out the heat of the arc, creating more cathode anode drops and allowing the fuse as a whole to clear the relatively low and mid-range currents. The spacing and control of the placement of the wires ensures that there will be no wire-to-wire flash-over causing shorting of the current, increasing the duty and causing the failure to clear.
1 A blown fuse indica-tor is combined with the present energy-limitlng fuse -to accomplish the required function of clearing fault curren-ts while holding -the interrupting duty imposed on associated equipment -to a point which the associated equipment can easily handle.
This is in comparison to the existing high current clearing short time melt backup fuse ~which requires 300 to 600 or more amperes before they relia~ly clearl. These currents are in excess of the duty of many of the associated switches.
I'he indicator is partially mounted in a recess in the spider allowing for a longer striker pin with a corresponding wider selection of spring forces and travel distances.
IN THE DRAWINGS
Figure 1 is a section view of the fuse according to the present invention.
Figure 2 i5 an enlarged view of a portion of Figure 1 showing the striker pin assembly.
- Figure 3 is a view taken on line 3-3 of Figure 1 showing a cross-section of the spider and striker pin assembly.
Figure 4 is a view taken on line 4-4 of Figure 1 showing the strain wire wound on the spider.
Figure 5 is a view taken on line 5-5 of Figure 1 showing the spider and one of the fuse wires.
Figure 6 is a perspective view of the striker pin assembly.
Figure 7 is a cross-section view of the striker pin assembly shown in the retracted pin posi-tion~
Figure 8 is a view of the striker pin assembly in the extended position, ~ 3 -7~
1 Figur~ ~ is a view taken on line 9-9 oE Figure 7 showing the strain wire passing through the s-triker pin.
DESCRIPTION OF THE INVENTION
The energy-limitiny ~use 10 as seen in Figure 1 generally includes a tubular housing 12, a spider assembly 14 and a striker pin assembly 16. The tubular housing 12 is closed at each end by means of electrically conductive terminal caps 18 and 20. The electrical fuse circuit between the end caps 18 and 20 is completed by means of a number of fuse elements 22 provided on the spider assembly 14. The housing is filled with a granular dielectric material 24 such as silica sand. Each of the fuse elements 22 acts independently in response to fault currents to clear the circuit between the end caps 18 and 20.
The striker pin assembly 16 is an independent unit which is mounted within the fuse 10 after the fuse has been assembled. The striker pin assembly is activated by means of a strain wire 26 provided on the spider assembly. Whenever a fault conditi.on occurs that fuses the elements 22/ all of the fault current will pass through the strain wire 26 to actuate the striker pin assembly 16.
SPIDER ASSEMBLY
More particularly and referring to Figures 1 through 4, the spider assembly 14 generally includes three electrically insulating mica plates 28 held together at each end by means of conductive end plates 30. The mica plates can be of the type shown in the Canadian Patent No. 1,108,671 issued September 8, 1981 to applicant (W.J. Huber, Inventor) Eor "Spider Assembly for a High Voltage Fuse". ~lowever, each mica plate 28 .includes a 1 plurality of tabs 32 alony each edge. The tabs on each plate are offsQt from the tabs on the opposite edge of -the plate and from the tabs on adjacent pla-tes to form a spiral suppor-t for the fuse elements 22. The fuse elements 22 are held in a constrained spaced relation on the spider assembly by means of notches 34 provided at the outer end of each of the tabs 32. The space between the notches is four to five times the width of the fuse elements 22 to prevent flash-over be~ween the elements during fault cu.rrent condition.
Two or more ~use elements can be.provided on -the spider a.ssembl~ in accordance with the rated capacity of the fuse. Each fuse element is individually ox independently connected to a tab 36 provided on the plates 30. The spider assembly is positioned within the housing 12 with the end plates 30 connected to the caps 18 and 20 by means of a con-ductive :lead 38.
Each of the mica plates 28 is provided with means at one end to accommodate the striker pin assembly 16.
~ Such means is in the form of a notch or groove 39 at one encl of each of the mica plates which define a recess for a portion of the spider assembly. The striker pin assembly is connected to the strain wire 26 by means of a conrector 40 provided at the inner end of the notches 39 ~Figure 2).
The circult through the striker pin assembly to cap 20 is completed by means of the strain wire 26~
STRIKER PIN ASSF,MBLY
The striker pin assembly 16, as seen in Figures 1,
2, 6, 7, 8 and 9, includes a tubular housing 50 having a striker pin 52 mounted for movement within the tubular housing 1 50 froM a first or w.i-thdrawn position to a second or indicating position. The pln 52 is biased outwardly from the housing 50 by means of a compression spring 54 which is seated on a shoulder 56 at the inner encl of the housincJ
50 and bears against spring xetainers 58 provided on the pin 52. The outward movement of the striker pin 52 is limited by means of a pair of stop pins ~0 provided at the entrance to the tubular housing 50.
Means are provided within the tubular housing for holding the striker pin in the first posit.ion in the housing~
Such means is in the form of an extension 62 provided at the inner end of the striker pin 52 and a flat surfclce 64 provided on the end of the housing 50. The extens.ion 62 is provided with a plurality of openings 66. A number of openings 68 are provided in the surface 64 corresponding to the openings 66 provided in the extension 62. The pin 52 is.retained within the housing 50 by ~eans of a strain wire 70 which is threaded through the openings 66 and 68.
This arrangement for holding the striker pin in the housing ~ is shown in Canadian Patent Application No. 381,544r filed - July 10, 1981 of applicant corporation (Link) and entitled "Blown Fuse Indicator". The strain wire 70 has one end connected to a tab 72 provided on the outside surface of the housing 50 and the other end connected to a contact spring 74 mounted on the inner end of the tube 50.
The striker pin assembly is an independent unit which is assembled in the fuse after the fuse has been completely assembled. The assembly is inserted through cap 20 into the recess provi.ded by -the notches 39 in the
50 and bears against spring xetainers 58 provided on the pin 52. The outward movement of the striker pin 52 is limited by means of a pair of stop pins ~0 provided at the entrance to the tubular housing 50.
Means are provided within the tubular housing for holding the striker pin in the first posit.ion in the housing~
Such means is in the form of an extension 62 provided at the inner end of the striker pin 52 and a flat surfclce 64 provided on the end of the housing 50. The extens.ion 62 is provided with a plurality of openings 66. A number of openings 68 are provided in the surface 64 corresponding to the openings 66 provided in the extension 62. The pin 52 is.retained within the housing 50 by ~eans of a strain wire 70 which is threaded through the openings 66 and 68.
This arrangement for holding the striker pin in the housing ~ is shown in Canadian Patent Application No. 381,544r filed - July 10, 1981 of applicant corporation (Link) and entitled "Blown Fuse Indicator". The strain wire 70 has one end connected to a tab 72 provided on the outside surface of the housing 50 and the other end connected to a contact spring 74 mounted on the inner end of the tube 50.
The striker pin assembly is an independent unit which is assembled in the fuse after the fuse has been completely assembled. The assembly is inserted through cap 20 into the recess provi.ded by -the notches 39 in the
3~ mica plate~.28. The contact spring 74 will engage t:he ~....~~'t'~
1 conductor 40 :located a-t the lnner end of the no-tches 39 and the con-tact 72 will engage the termination pla-te 30 to provide electrical communica-tion between the termina1ion pla-te 30 and the conductor 40. The indicator circuit will be completed between the terminal caps 18 and 20 when the con-tacts 72 and 74 engage the plate 30 and conduc-tor 40, respectively.
In the event of a faul~ current occurring which fuses the fuse elements 22, -the fault current will pass through the strain wires 26 and 70. The wire 70 will vaporize releasing the pin extension 62 from the housing 50. The bias of spriny 54 will move the striker pin 52 to a switch actuating or indicator position as seen i.n Figures 2 and 8.
1 conductor 40 :located a-t the lnner end of the no-tches 39 and the con-tact 72 will engage the termination pla-te 30 to provide electrical communica-tion between the termina1ion pla-te 30 and the conductor 40. The indicator circuit will be completed between the terminal caps 18 and 20 when the con-tacts 72 and 74 engage the plate 30 and conduc-tor 40, respectively.
In the event of a faul~ current occurring which fuses the fuse elements 22, -the fault current will pass through the strain wires 26 and 70. The wire 70 will vaporize releasing the pin extension 62 from the housing 50. The bias of spriny 54 will move the striker pin 52 to a switch actuating or indicator position as seen i.n Figures 2 and 8.
Claims (10)
1. An energy-limiting fuse comprising a tubular housing, a rigid spider assembly mounted within said housing, a plurality of notches in the outer edges of the spider, said notches being located in a spaced relation to define spiral parallel supporting surfaces, at least two fuse elements spirally wrapped around said spider, in a parallel spaced relation in said notches, said spider assembly including electrically conductive means at each end for terminating said fuse elements, whereby said fuse elements are spaced apart a distance sufficient for each element to act independently.
2. The fuse according to claim 1, wherein said notches are arranged to constrain the fuse elements in a spaced relation of at least four times the width of the elements.
3. The fuse according to claim 1, wherein said spider includes a recess at one end and a contact mounted at the inner end of the recess, a first strain wire mounted on said spider connecting the contact means to the conductive means at the opposite end of the spider assembly, a striker pin assembly partially mounted in the recess and having a contact at the inner end for engaging the contact at the inner end of the recess, a second strain wire for activating said striker pin assembly, said second strain wire connecting the pin contact to the conductive means at the other end of the spider assembly whereby said
3. The fuse according to claim 1, wherein said spider includes a recess at one end and a contact mounted at the inner end of the recess, a first strain wire mounted on said spider connecting the contact means to the conductive means at the opposite end of the spider assembly, a striker pin assembly partially mounted in the recess and having a contact at the inner end for engaging the contact at the inner end of the recess, a second strain wire for activating said striker pin assembly, said second strain wire connecting the pin contact to the conductive means at the other end of the spider assembly whereby said
Claim 3 continued....
striker pin assembly will be activated on vaporization of the strain wire.
striker pin assembly will be activated on vaporization of the strain wire.
4. The fuse according to claim 2, wherein said spider includes a recess at one end and a contact mounted at the inner end of the recess, a first strain wire mounted on said spider connect-ing the contact means to the conductive means at the opposite end of the spider assembly, a striker pin assembly partially mounted in the recess and having a contact at the inner end for engaging the contact at the inner end of the recess, a second strain wire for activating said striker pin assembly, said second strain wire connecting the pin contact to the conductive means at the other end of the spider assembly whereby said striker pin assembly will be activated on vaporization of the strain wire.
5. The fuse according to claim 3 or 4, wherein said striker pin assembly includes a tubular housing, a striker pin mounted in said housing and means for biasing said pin outwardly from said housing.
6. An energy-limiting fuse comprising an insulating housing, an electrically conductive terminal cap at each end of said housing, a spider assembly mounted within said housing, said spider assembly enclosing a number of mica plates each having a number of fuse element supporting tabs on each edge of each plate,
6. An energy-limiting fuse comprising an insulating housing, an electrically conductive terminal cap at each end of said housing, a spider assembly mounted within said housing, said spider assembly enclosing a number of mica plates each having a number of fuse element supporting tabs on each edge of each plate,
Claim 6 continued...
said tabs being arranged to define substantially parallel spiral supporting surfaces for the fuse elements, a number of fuse elements mounted on said supporting surfaces, and electrically conductive means of each end of said spider assembly for connecting said fuse elements to said terminal caps, said fuse elements being spaced apart a distance sufficient for each element to operate independently.
said tabs being arranged to define substantially parallel spiral supporting surfaces for the fuse elements, a number of fuse elements mounted on said supporting surfaces, and electrically conductive means of each end of said spider assembly for connecting said fuse elements to said terminal caps, said fuse elements being spaced apart a distance sufficient for each element to operate independently.
7. The fuse according to claim 6, wherein said tabs include a notch at the outer end to constrain the position of the fuse element in the fuse.
8. The fuse assembly according to claim 6 or 7, wherein said elements are spaced apart a distance equal to at least four times the width of the fuse element.
9. The fuse according to claim 6, including an independent striker pin assembly mounted in said fuse and means in said spider assembly for electrically engaging said striker pin assembly whereby said striker pin assembly responds to a fault current condition in said fuse.
10. The fuse according to claim 9, wherein said striker pin assembly includes a striker pin, a spring for biasing said pin to an operative position and an electrically vaporizable member holding said pin against the bias of said spring whereby on fusing of said elements under fault current conditions said vaporizable member will be vaporized releasing said pin for movement by said spring.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000452137A CA1181788A (en) | 1981-07-20 | 1984-04-16 | Low current clearing back-up fuse |
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US06/284,606 US4420735A (en) | 1981-07-20 | 1981-07-20 | Low current clearing back up fuse |
| US284,606 | 1981-07-20 | ||
| CA000406192A CA1181787A (en) | 1981-07-20 | 1982-06-29 | Low current clearing back-up fuse |
| CA000452137A CA1181788A (en) | 1981-07-20 | 1984-04-16 | Low current clearing back-up fuse |
Related Parent Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000406192A Division CA1181787A (en) | 1981-07-20 | 1982-06-29 | Low current clearing back-up fuse |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1181788A true CA1181788A (en) | 1985-01-29 |
Family
ID=27167257
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000452137A Expired CA1181788A (en) | 1981-07-20 | 1984-04-16 | Low current clearing back-up fuse |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1181788A (en) |
-
1984
- 1984-04-16 CA CA000452137A patent/CA1181788A/en not_active Expired
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEC | Expiry (correction) | ||
| MKEX | Expiry |