Patent Application
20060012934
1. Field of the Invention
The present invention relates to power circuit interruption and, more particularly, to fuses providing circuit interruption for low voltage power busses.
2. Background Information
Load side fuses of various designs are used in network protectors for underground power distribution. The primary purpose of these fuses is to act as a back-up to the network protector in the event of a malfunction thereof. Such a fuse coordinates with the network protector and should not blow on a network feeder fault before the network protector trips. However, if the network protector does not timely trip open, then the fuse must blow in a reasonable time in order to prevent transformer damage.
Copper Z, copper Y and S fuse links are designed to handle relatively high currents (e.g., about 800 A to about 6 kA) and low voltage (e.g., up to about 600 VACRMS). Typically, the fuses are made of pure copper and are silver plated. The interrupting mechanism for the fuses (e.g., copper Z; copper Y; type S) is the heat generated by passing fault level currents through a relatively small cross-sectional area of the fuse.
Known interrupting fuses that provide close to optimum melting curves, in order to permit selective operation with cable limiters, include copper link style fuses (e.g., type Y25; type Z50). However, such fuses produce about 50% of the power (watts) thermal losses inside a network protector enclosure.
Other known alloy fuses have adequate interrupting capacity and relatively more favorable power (watts) thermal loss characteristics. However, such fuses have undesirable damage and blowing characteristics and do not permit selective operation with limiters.
Another known fuse, the type “S” fuse, provides advantages in protection and blowing characteristics over alloy fuses and advantages in power (watts) thermal losses over copper link style fuses. However, the construction of type “S” fuses requires that each fuse element be brazed and pinned to a copper fuse base.
The temperature required to braze the fuse assembly weakens the relatively thin fuse elements, thereby causing variability in both damage and blowing characteristics.
There is room for improvement in fuses.
These needs and others are met by the present invention, which provides a continuous laminate fuse to address protection and blowing characteristics, power (watts) thermal losses, and variability in damage and blowing characteristics.
Preferably, the continuous laminate fuse is not soldered and employs uniform length laminates, as contrasted with a relatively small soldered link, in order to provide advantages in power (watts) thermal losses.
The fuse may be manufactured by employing a press welding technique. With press welding, the fuse resistance value is equal to that of a flat copper bar. As a result, voltage losses are minimized, thereby maintaining a uniform current flow. Furthermore, a consistent pocket is preferably provided for tin alloy to reside.
As an aspect of the invention, a fuse is adapted for electrical connection between a first low voltage power bus and a second low voltage power bus, the fuse comprises: at least one pair of spacer laminations, each of the at least one pair including a first spacer lamination and a second spacer lamination, the first and second spacer laminations having a first area; and a plurality of fuse element laminations, each of the fuse element laminations including a first portion laminated to the first spacer lamination of at least one of the at least one pair, a second portion laminated to the second spacer lamination of the at least one of the at least one pair, and a third portion disposed between the first and second portions and intermediate the first and second spacer laminations of the at least one of the at least one pair, wherein the first and second portions of the fuse element laminations have a second area, which is about equal to the first area.
The third portion may include a fuse element alloy pocket. The fuse element alloy pocket may have a semi-rectangular profile. The semi-rectangular profile may be filled with a tin alloy in a non-interrupted state of the fuse.
The third portion may have a general V-shape.
A first count of the at least one pair of spacer laminations may be equal to a positive integer, N, and a second count of the plurality of fuse element laminations may be equal to N plus one.
A first count of the at least one pair of spacer laminations may be equal to three, and a second count of the plurality of fuse element laminations may be equal to four.
A first count of the at least one pair of spacer laminations may be equal to two, and a second count of the plurality of fuse element laminations may be equal to three.
A first count of the at least one pair of spacer laminations may be equal to one, and a second count of the plurality of fuse element laminations may be equal to two.
A full understanding of the invention can be gained from the following description of the preferred embodiments when read in conjunction with the accompanying drawings in which:
As employed herein, the statement that two or more parts are “connected” or “coupled” together shall mean that the parts are joined together either directly or joined through one or more intermediate parts. Further, as employed herein, the statement that two or more parts are “attached” shall mean that the parts are joined together directly.
As employed herein, the term “fastener” shall expressly include, but not be limited to, any suitable fastening member(s) (e.g., without limitation, a threaded fastener; a non-threaded fastener; a removable fastener; a non-removable fastener; a bolt; a machine screw; a rivet; a soldered connection; an adhesive connection), which is employed such that two or more parts are connected or coupled together.
Referring to
The fuse 2 further includes one or more pairs 8 of spacer laminations. Each of these pairs 8 (e.g., three pairs 8 are shown in
As best shown in
The fuse element laminations 14 extend and are preferably laminated between the pairs 8 of spacer laminations 10,12 by a suitable press welding method to form a fuse base. The fuse element laminations 14 are designed with a suitably consistently dimensioned pocket 32, which holds a suitable predetermined amount of an alloy 34. The alloy 34 (e.g., tin; lead; and/or a combination thereof) is applied by a cast in place method to each of the pockets 32. The alloy 34 (e.g., tin) functions (e.g., by molten metal corrosion) to start the initial melting of the fuse 2, since the alloy 34 has a lower melting temperature than that of the lamination 14 (e.g., which is made of copper). The alloy 34 amalgamates into the structure of the lamination 14 changing the resistance of the joint to a relatively high resistance and allowing for consistent interruption.
The mounting holes 22,24 through the fuse element laminations 14 are added in varying configurations (e.g., as shown in
As best shown in
Referring to
Although fasteners 30 are disclosed, the two ends of the fuse 2 may be electrically and mechanically connected to corresponding heat sinks (not shown), which, in turn, are electrically and mechanically connected to corresponding low voltage power busses (e.g., busses 4,6). An example of such conductive heat sinks is disclosed in U.S. Pat. No. 6,510,047, which is incorporated by reference herein. Corresponding fasteners (not shown) may protrude from the terminal end (not shown) of the corresponding heat sinks. Otherwise, the fuse 2 may be directly electrically and mechanically connected to the corresponding low voltage power busses 4,6, as shown in
The fuse 2 melts and vaporizes between the non-interrupted state (
Although press welding is disclosed, the low loss continuous laminate fuses 2,42,62,72 may be laminated by any suitable method, such as, for example, riveting, swaging, brazing and/or soldering.
While specific embodiments of the invention have been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular arrangements disclosed are meant to be illustrative only and not limiting as to the scope of the invention which is to be given the full breadth of the claims appended and any and all equivalents thereof.
