Patent Application
20180068820
The present disclosure relates generally to the field of circuit protection devices, and relates more particularly to a non-arcing fuse.
Fuses are commonly used as circuit protection devices and are typically installed between a source of electrical power and a component in a circuit that is to be protected. One type of fuse, commonly referred to as “cartridge fuse” or “tube fuse,” includes a fusible element disposed within a hollow, electrically insulating fuse body. Upon the occurrence of a specified fault condition, such as an overcurrent condition, the fusible element melts or otherwise opens to interrupt the flow of electrical current between the electrical power source and the protected component.
When the fusible element of a fuse is melted during an overcurrent condition, it is sometimes possible for an electrical arc to propagate between the separated portions of the fusible element. If not extinguished, this electrical arc may allow significant follow-on currents to flow to the protected component, resulting in damage to the component despite the physical opening of the fusible element. Thus, it is desirable to provide a fuse that effectively prevents or mitigates electrical arcing during overcurrent conditions.
It is with respect to these and other considerations that the present improvements may be useful.
This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended as an aid in determining the scope of the claimed subject matter.
An exemplary embodiment of an arc-mitigating fuse in accordance with the present disclosure may include a tubular fuse body, a first endcap covering a first end of the fuse body and a second endcap covering a second end of the fuse body, a fusible element disposed within the fuse body and extending between the first endcap and the second endcap to provide an electrically conductive pathway therebetween, and an arc-mitigating element disposed within the fuse body and held in a compressed state between the first endcap and the second endcap, the arc-mitigating element adapted to extend to an uncompressed state upon separation of the fusible element.
An exemplary embodiment of a method for manufacturing an arc-mitigating fuse in accordance with the present disclosure may include attaching a fusible element to a first endcap, securing an arc-mitigating element to the first endcap, placing a tubular fuse body over the fusible element and the arc-mitigating element with the first endcap covering a first end of the fuse body, placing a second endcap over a second end of the fuse body and in engagement with the arc-mitigating element, the fusible element extending through a hole in the second endcap, forcing the first end cap and the second end cap toward one another to compress the arc-mitigating element, and securing the fusible element to the second end cap to hold the arc-mitigating element in a compressed state.
Embodiments of a non-arcing fuse and a method for manufacturing the same in accordance with the present disclosure will now be described more fully with reference to the accompanying drawings, in which preferred embodiments of the present disclosure are presented. The non-arcing fuse and the accompanying method of the present disclosure may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the non-arcing fuse and the accompanying method to those skilled in the art. In the drawings, like numbers refer to like elements throughout unless otherwise noted.
Referring to
Referring to
The fuse body 12 of the fuse 10 may be formed of an electrically insulating and preferably heat resistant material, including, but not limited to, ceramic or glass. The endcaps 18, 20 may be formed of an electrically conductive material, including, but not limited to, copper or one of its alloys, and may be plated with nickel or other conductive, corrosion resistant coatings. The fusible element 24 may be formed of an electrically conductive material, including, but not limited to, tin or copper, and may be configured to melt and separate upon the occurrence of a predetermined fault condition, such as an overcurrent condition in which an amount of current exceeding a predefined maximum current flows through the fusible element 24.
The fuse 10 may further include an arc-mitigating element 38 disposed within the fuse body 12 and extending between the endcaps 18, 20. The arc-mitigating element 38 may be formed of a quantum tunneling compound (QTC). As will be familiar to those of ordinary skill in the art, QTCs are typically resilient rubber compounds that are loaded with particles of electrically conductive materials, which may include, but are not limited to, silver and nickel. When a QTC is in a natural, uncompressed state, the conductive particles within the QTC are relatively far apart from one another and the electrical resistance of the QTC is relatively high. However, when a QTC is compressed, the conductive particles within the QTC are moved relatively closer to one another and the electrical resistance of the QTC is therefore relatively lower than in the uncompressed state. The arc-mitigating element 38 may be a generally tubular body that radially surrounds the fusible element 24 as shown in
The arc-mitigating element 38 may be secured to the endcaps 18, 20 in electrical communication therewith, such as by electrically conductive epoxy, solder, mechanical fasteners, etc. However, at least one of the endcaps 18, 20 is not secured to the fuse body 12. Thus, at least one of the endcaps 18, 20 is free to move axially relative to the fuse body 12 as described in greater detail below.
In the assembled fuse 10, the arc-mitigating element 38 may be held in axial compression between the endcaps 18, 20 by the fusible element 24 as shown in
Upon the occurrence of an overcurrent condition in the fuse 10, the fusible element 24 may melt and separate as shown in
Since a nominal amount of current is allowed to flow through the arc-mitigating element 38 as it expands from its compressed state to its uncompressed state and as its electrical resistance increases from R1 to R2, voltage build-up between the separated ends 40, 42 of the fusible element 24 is minimized or eliminated and the likelihood of electrical arcing between the separated ends 40, 42 is thereby mitigated. The nominal current that flows through the arc-mitigating element 38 after separation of the fusible element 24 is substantially dissipated as heat. Thus, the total effect of the expansion of the arc-mitigating element 38 is that electrical arcing within the fuse 10 is mitigated and significant follow-on currents that could otherwise damage protected devices connected to the fuse 10 are prevented.
Referring to
At step 100 of the exemplary method, the fusible element 24 may be secured to the endcap 20 in electrical communication therewith, such as by a quantity of solder 32 or other electrically conductive means of affixation (e.g., welding, conductive adhesive, etc.). In one non-limiting example, an end of the fusible element 24 may be extended through the hole 28 in the endcap 20 and may be soldered to the exterior face 36 of the endcap 20 as shown in
At step 110 of the exemplary method, the arc-mitigating element 38 may be secured to the endcap 20 in electrical communication therewith, such as by solder, conductive adhesive, etc. In the embodiment of the fuse 10 shown in
At step 120 of the exemplary method, the fuse body 12 may be placed over the arc-mitigating element 38 and the fusible element 24 with the open end 16 of the fuse body 12 disposed adjacent the endcap 20 and with the arc-mitigating element 38 and the fusible element 24 extending axially through the fuse body 12. At step 130, the endcap 18 may be placed over the open end 14 of the fuse body 12 and may be secured to the arc-mitigating element 38 in electrical communication therewith, such as by solder, conductive adhesive, etc., with an end of the fusible element 24 extending through the hole 26 in the endcap 18.
At step 140 of the exemplary method, the arc-mitigating element 38 may be axially compressed, such as by the application of axial force on the endcaps 18, 20 toward one another, with the rigid fuse body 12 acting as a limit or hard stop. While the arc-mitigating element 38 is held in axial compression, the end of the fusible element 24 may, at step 150 of the method, be secured to the endcap 18 in electrical communication therewith, such as by a quantity of solder 30 or other electrically conductive means of affixation (e.g., welding, conductive adhesive, etc.). In one non-limiting example, the solder 30 may be applied to the exterior face 34 of the endcap 18 as shown in
As used herein, an element or step recited in the singular and proceeded with the word “a” or “an” should be understood as not excluding plural elements or steps, unless such exclusion is explicitly recited. Furthermore, references to “one embodiment” of the present disclosure are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features.
While the present disclosure makes reference to certain embodiments, numerous modifications, alterations and changes to the described embodiments are possible without departing from the sphere and scope of the present disclosure, as defined in the appended claim(s). Accordingly, it is intended that the present disclosure not be limited to the described embodiments, but that it has the full scope defined by the language of the following claims, and equivalents thereof.
