This disclosure relates to current limiting fuses for high voltage, high current applications.
Current limiting fuses are used with high voltage applications, such as high voltage power lines and transformers. Examples of current limiting fuses can be found in U.S. Pat. No. 6,538,550, which is incorporated by reference. Current limiting fuses generally include an insulating cylindrical housing that contains a metal fuse element encased in silica sand. The housing is enclosed on either end by metallic end caps that are attached with an adhesive, such as epoxy. When an excessive current is applied, the metal fuse element melts to break the electrical circuit. When the fuse element melts, high pressures are created inside the fuse, which can cause the end plates to become separated from the housing.
In transformers, such current limiting fuses can be electrically connected to other fuses. For example, a current limiting fuse may be connected in series with a bayonet fuse, such as is described in U.S. Pat. No. 5,936,507, which is incorporated by reference.
In an aspect, a housing for a current limiting fuse includes a metal fuse element and a non-conductive filler material, where the fuse element is configured to melt to create an open circuit when an applied current exceeds a threshold amount (e.g., between about 2 to about 1200 amperes). The housing includes first and second cylindrical members. The first cylindrical member has an open end portion and the second cylindrical member has an integrally formed closed end portion and an open end portion configured to be attached to the open end portion of the first cylindrical member to close the housing. The housing also includes a fastening member configured to prevent the open end portion of the first cylindrical member from separating from the open end portion of the second cylindrical member when the fuse element melts.
Implementations of this aspect may include one or more of the following features.
The first cylindrical member may include an integrally formed closed end portion at an end of the first cylindrical member opposite from the open end portion. The first cylindrical member may be substantially longer than the second cylindrical member. The first cylindrical member may include a tube and the second cylindrical member may include a cap. The first and second cylindrical members may be about the same length. The first cylindrical member may include a first tubular member and the second cylindrical member may include a second tubular member.
The first cylindrical member may include a second open end portion opposite the end portion of the first cylindrical member. A metal end plate may be attached to the second end portion of the first cylindrical member. A third cylindrical end portion that has an integrally formed closed end portion and an open end portion may be configured to be attached to the second open end portion of the first cylindrical member. The first cylindrical member may include a tube, the second cylindrical member may include a cap, and the third cylindrical member may include a cap.
The fastening member may include a clip that is coupled to the first and second cylindrical members or may include threads on the first and second cylindrical members. An adhesive may further secure the first and second cylindrical members to one another. A sealing member, such as an O-ring, may be disposed between the first and second cylindrical members. The current limiting fuse may be configured to be used with voltage between about 5 kV and about 38 kV.
In another aspect, a fuse assembly includes a housing that includes first and second cylindrical members. The first cylindrical member has an open end portion and the second cylindrical member has an integrally formed closed end portion and an open end portion configured to be attached to the open end portion of the first cylindrical member to close the housing. The fuse assembly also includes a current limiting fuse that includes a metal fuse element and a non-conductive filler material received in the housing. The fuse element is configured to melt to create an open circuit when an applied current exceeds a threshold amount (e.g., between about 2 and about 1200 amperes). The fuse assembly also includes a fastening member configured to prevent the open end portion of the first cylindrical member from separating from the open end portion of the second cylindrical member when the fuse element melts.
Implementations of this aspect may include one or more of the following features.
The first cylindrical member may include an integrally formed closed end portion at an end of the first cylindrical member opposite from the open end portion. The first cylindrical member may be substantially longer than the second cylindrical member. The first cylindrical member may include a tube and the second cylindrical member may include a cap. The first and second cylindrical members may be about the same length. The first cylindrical member may include a first tubular member and the second cylindrical member may include a second tubular member.
The first cylindrical member may include a second open end portion opposite the end portion of the first cylindrical member. A metal end plate may be attached to the second end portion of the first cylindrical member. A third cylindrical end portion that has an integrally formed closed end portion an open end portion may be configured to be attached to the second open end portion of the first cylindrical member.
The fastening member may include a clip that is coupled to the first and second cylindrical members or may include threads on the first and second cylindrical members. An adhesive may further secure the first and second cylindrical members to one another. A sealing member may be disposed between the first and second cylindrical members. The current limiting fuse may be configured to be used with voltage between about 5 kV and about 38 kV.
In another aspect, a housing for a current limiting fuse includes a metal fuse element and a non-conductive filler material, where the fuse element is configured to melt to create an open circuit when an applied current exceeds a threshold amount (e.g., between about 2 and about 1200 amperes). The housing includes a cylindrical member with an open end portion, a cap portion configured to be attached to the open end portion of the cylindrical member to close the housing, and a joining member configured to attach the cap portion to the cylindrical member by other than an adhesive bond to prevent separation of the cap portion and the cylindrical member when the fuse element melts.
Implementations of this aspect may include one or more of the following features. The cylindrical member may include an integrally formed closed end portion at an end of the cylindrical member opposite the open end portion. The cylindrical member may include a second open end portion opposite the end portion of the cylindrical member. A metal end plate may be attached to the second open end portion of the cylindrical member. A second cap portion may be configured to be attached to the second open end portion of the cylindrical member to close the housing and a second joining member configured to attach the cap portion to the cylindrical member by other than an adhesive bond. The joining member may include a clip that is coupled to the first and second cylindrical members or threads on the cylindrical member and on the cap. An adhesive may further secure the cylindrical member and the cap. A sealing member, such as an O-ring, may be disposed between the cylindrical member and the cap. The current limiting fuse may be configured to be used with voltage between about 5 kV and about 38 kV.
In another aspect, a fuse assembly includes a housing that includes a cylindrical member with an open end and a cap portion configured to be attached to the open end portion of the cylindrical member to close the housing. A current limiting fuse that includes a metal fuse element and a non-conductive filler material is received in the housing. The fuse element is configured to melt to create an open circuit when an applied current exceeds a threshold amount (e.g., between about 2 and about 1200 amperes). A joining member is configured to attach the cap portion to the cylindrical member by other than an adhesive bond to prevent separation of the cap portion and the cylindrical member when the fuse element melts.
Implementations of this aspect may include one or more of the following features. The cylindrical member may include an integrally formed closed end portion at an end of the cylindrical member opposite the open end portion. The cylindrical member may include a second open end portion opposite the end portion of the cylindrical member. A metal end plate may be attached to the second open end portion of the cylindrical member. A second cap portion may be configured to be attached to the second open end portion of the cylindrical member to close the housing and a second joining member may be configured to attach the cap portion to the cylindrical member by other than an adhesive bond. The joining member may include a clip that is coupled to the first and second cylindrical members or threads on the cylindrical member and on the cap. An adhesive may further secure the cylindrical member and the cap. A sealing member may be disposed between the cylindrical member and the cap. The current limiting fuse may be configured to be used with voltage between about 5 kV and about 38 kV.
In another aspect, a mounting assembly for coupling a current limiting fuse to an element that defines a longitudinal axis is disclosed. The mounting assembly includes a mounting member configured to be mounted to the element in a plurality of positions about the longitudinal axis. A first attachment member is coupled to the mounting member in a fixed position relative to the mounting member. A second attachment member is coupleable to the current limiting fuse. The first and second attachment members are configured to be attached to one another in a plurality of discreet positions about an axis that is non-parallel to the longitudinal axis.
Implementations of this aspect may include one or more of the following features.
The element may include a bayonet fuse. The bayonet fuse may have a tube having a square cross section and the mounting member may be adjustable about the longitudinal axis in 90 degree intervals. The element may include a wall and the longitudinal axis may be perpendicular to the wall. The mounting member may include an L-shaped bracket with a leg configured to be mounted to the wall.
The mounting member may include a first piece and a second piece. The first piece may define a slot and the second piece may have a tab that fits into the slot. The mounting member may include a fastener for attaching the first member to the second member. The first piece may have a first concave portion and the second portion may have a second concave portion, the first and second concave portions facing each other to receive the element therebetween. The first concave portion may include a first flattened region and the second concave portion may include a second flattened region, the first and second flattened regions allow the mounting member to be mounted to the element at a plurality of discreet positions. The first attachment member may include a socket that includes a plurality of grooves. The second attachment member may include a projection that includes a plurality of teeth corresponding to the grooves.
A third attachment member may be coupled to the mounting member in a fixed position relative to the mounting member, such that the second attachment member is configured to be attached to the first attachment member or the third attachment member in a plurality of discreet positions about an axis that is non-parallel to the longitudinal axis. A third attachment member may be couplable to the current limiting fuse, such that the first attachment member is configured to be attached to the second attachment member or the third attachment member in a plurality of discreet positions about an axis that is non-parallel to the longitudinal axis. The second attachment member may be integral with and/or removeable from the current limiting fuse. The second attachment member may be integral with a clamp that may be removably couplable to the current limiting fuse.
The details of one or more implementations are set forth in the accompanying drawings and the description below. Other features and advantages will be apparent from the description and drawings, and from the claims.
Housing 12 includes a tubular member 14 with a cylindrical wall 15, an open end portion 16, and an integrally formed closed end portion 18. Fuse assembly 10 also includes a cylindrical cap 20 with a cylindrical wall 21, an open end portion 22, and an integrally formed closed end portion 24. Cap 20 has a length L2 that is substantially shorter than a length L1 of tubular member 14. When attached, open end portion 24 of cap 20 fits snugly over open end portion 16 of tubular member 14 to close housing 12. Housing 12 further includes a joining or fastening member 30 configured to attach cap 20 to tubular member 12 by other than an adhesive bond to prevent separation of cap 20 and tubular member 12 when the fuse element melts. Housing 12 and cap 20 are composed of a substantially rigid insulating material, such as ceramic or fiberglass reinforced plastic materials, and are each formed as a single-piece by a process such as injection molding.
Fuse element 50 includes a conductive element 54 that is helically wound around a non-conductive core 56. Conductive element 54 is formed from a conductive metal, such as, for example, a copper or silver alloy, that melts at an appropriate temperature for the amperage rating of the fuse. Conductive element 54 is attached at either end to disc-shaped conductive end plates 60a and 60b.
Referring also to
Wall portion 70 also includes an outwardly projecting annular flange 76 that defines a central bore 78 through wall portion 70. Received through central bore 78 is boss 61a of end plate 60a. Received in threaded central bore 62a of boss 61a and forming an electrical contact with end plate 60a is a threaded elongated portion 81 of a conductive bushing 80. Bushing 80 also includes a cap portion 82 that wraps around the exterior of flange 76. Extending partially through bushing 80 is a threaded bore 84 that is configured for attachment to another piece of electrical equipment, such as, for example, a high voltage power line, a transformer, or another fuse assembly. Disposed between conductive bushing 80 and wall portion 70 are sealing members, such as rubber O-rings 85a and 85b, that help form a seal between bushing 80 and wall portion 70.
Referring also to
Wall portion 40 also includes an outwardly projecting annular flange 46 that defines a central bore 48 through wall portion 40. Received through central bore 48 is boss 61b of end plate 60b. Received in threaded central bore 62b of boss 61b and forming an electrical contact with end plate 60b is a threaded elongated portion 27 of a conductive bushing 26. Bushing 26 also includes a cap portion 28 that wraps around the exterior of flange 46. Extending partially through bushing 26 is a threaded bore 29 that is configured for attachment to another piece of electrical equipment, such as, for example, a high voltage power line, a transformer, or another fuse assembly. Disposed between conductive bushing 26 and wall portion 40 are sealing members, such as rubber O-rings 85a and 85b, that help form a seal between bushing 26 and wall portion 40.
Joining or fastening member 30 includes a ring-shaped clip 32 having a side wall 34, a top wall 36, and fingers 38. Clip 32 is inserted over cap 20 so that the side wall 34 of clip 32 abuts the cylindrical wall 21, and the top wall 36 of clip 32 abuts the disc-shaped portion 42 of the wall portion 40. Fingers 38 are then crimped so that they clamp against an annular flange 17 that is formed on the open end portion 16 of the tubular member 14. In this way, clip 32 fastens cap 20 to tubular member 14 to help prevent separation of cap 20 and tubular member 14 when fuse element 50 melts.
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Upper bracket 620 includes a groove 626 and lower bracket 630 includes a corresponding tab 636 that fits into groove 626 to align upper bracket 620 with lower bracket 630. Upper and lower brackets 620 and 630 also include corresponding respective flanges 628 and 638, each of which defines a respective bore 629 or 639 for receiving a fastener, such as a bolt or set screw 635 that clamps upper and lower brackets 620 and 630 about tube 604. Coupled to and in a fixed position relative to upper bracket 620 are three attachment members 640. Each attachment member 640 includes a cylindrical socket 642 having interior grooves 644 arranged in a star-shaped pattern.
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A number of implementations have been described. Nevertheless, it will be understood that various modifications may be made. For example, the fuse may be rated for use at a lower or higher amperage, or at a lower or higher voltage. The shape of the fuse element can be straight rather than coiled, and multiple metal fuses can be included within the housing. The housing may be filled with something other than silica sand. The housing may be composed of other types of insulating materials such as plastic or rubber. The cap and the tubular member can have different lengths than shown in the figures. Similarly, the two tubular members can have lengths that differ from one another.
In addition to or instead of the metal clip or threads, other attachment members can be used to secure the parts of the housing together. The metal ring can be shaped by using magnetic fields to shape the fingers of the ring and hold the parts together. The metal ring can be mechanically crimped into place. Composite wrap type materials can be placed over each molded part and cured. Snap fit projections can slide over one part and snap into place to hold the fuse cap and fuse housing together. Twist lock shapes can attach the parts. Projections on one part can pass through a hole in a flange on the other part and can be melted under pressure. The parts can be joined together by ultrasonic welding, induction heating, with or without special fillers, or hot plate welding. A flange can be formed on both the fuse cap and on the fuse housing with holes projecting through the flanges for receiving fasteners, such as, nuts and bolts, self-tapping screws, and rivets. Similar techniques can be used to attach projections to the housing for attachment to the mounting member. In addition to the foregoing, the parts can be joined by adhesives such as epoxy or urethane.
The sealing members on the fuse cap and fuse housing may be made by melting the end contacts into the molded plastic parts. This may be accomplished by heating the parts in an oven and pressing them together or by using an induction heater to heat the metal parts, while pressing the parts into place or applying force to the plastic. The metal parts may be coated with materials that reflow during heating and then solidify. These coatings may concentrate the heat and/or form adhesive or mechanical seals between the molded plastic and metal parts.
The mounting member may be formed as an integral part of the mounting component (e.g., the bayonet fuse assembly). The mounting bracket may be formed from a conductive material such as copper and may be formed to mate with the mounting stud of a high voltage bushing used, for example, to connect a transformer to cables of an electrical system. The mounting member may have a smaller or larger number of sockets and the fuse may have a smaller or larger number of projections. The grooves and the teeth on the sockets and the projections may be larger or fewer in number and may have different shapes than those shown. The mounting member may include the projections, while the fuse includes the sockets. The tube of the bayonet fuse assembly may have any shape cross section, such as circular or hexagonal, or other features, such as bumps or grooves, that allow the mounting member to be mounted to the bayonet fuse assembly at additional positions.
Several possible components may be attached to the current limiting fuse, including, for example, a high voltage bushing, a bayonet fuse assembly, a MagneX interrupter, a load break switch used to reconfigure a cable system, a high voltage switch used to turn a transformer on or off, and a dual voltage or tap changing switch.
These and other implementations are within the scope of the following claims.
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Number | Date | Country | |
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20060119464 A1 | Jun 2006 | US |