Patent Application
20220328272
Embodiments of the present disclosure relate to fuse housing and, more particularly, to fusing housing for high-voltage systems.
Fuses are current-sensitive devices which are designed as the intentional weak link in an electrical circuit. The function of the fuse is to provide discrete component or complete circuit protection by reliably melting under overcurrent conditions and thus safely interrupting the flow of current.
Fuses are selected based on the environment to be protected. Parameters such as voltage rating, interrupting rating, time-current characteristics, and current rating, to name a few, are considered when selecting a fuse. The voltage rating indicates the maximum voltage of the circuit for which the fuse is designed to operate safely in the event of an overcurrent. The interrupting rating (also known as breaking capacity or short circuit rating) is the maximum current which the fuse can safely interrupt at the rated voltage. The time-current characteristics determine how fast the fuse responds to different overcurrent events. The current rating is the maximum current which the fuse can continuously carry under specified conditions.
A 12V system is one that has a rated voltage of 12V, but may be connected to a fuse having a 32V interruption voltage. This means that, if the 12V system receives 32V, the fuse will break, creating an open circuit, and protecting the devices/components in the 12V system that the fuse is meant to protect. Similarly, a 48V system may have an interruption voltage of 70V, with the appropriate fuse for interrupting the 70 volts being selected for that system.
When the fuse protecting a circuit breaks, an arc energy is created between the two terminals of the fuse. When the fuse starts to open at the interruption voltage, the arc will occur, causing the metal of the breakable portion of the fuse element, as well as other materials, to melt and deposit within the fuse housing and, where the fuse is vented, and possibly outside the housing as well.
Whatever the voltage rating of the fuse, this arc energy occurs. However, the arc energy is much higher for the 70V system than for the 32V system. A 70V system may experience arc energy that is three times as high, or more, than the 32V system. For a 70V voltage system, the housing strength, outgassing, and Open State Resistance (OSR) of the fuse become a significantly higher challenge than for 32V systems.
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 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 a fuse housing in accordance with the present disclosure may include a top portion and a bottom portion. The bottom portion has a first labyrinth wall on a left side forming a first path for the movement of outgassing materials from the fuse housing when a fuse element breaks. The bottom portion also has a second labyrinth wall on a right side forming a second path for the movement of outgassing materials from the fuse housing when the fuse element breaks. The fuse housing also has a first vent channel located at a first exit of the first path and a second vent channel located at a second exit of the second path.
Another exemplary embodiment of a fuse housing in accordance with the present disclosure may include a first labyrinth wall on a first side, terminated by a first vent channel, a second labyrinth wall on a second side, terminated by a second vent channel. The first and second vent channels have a first depth and the first and second labyrinth walls have a second depth, and the second depth is substantially larger than the first depth. The fuse housing also has multiple ribs in a central portion which are beneath a fuse element. Outgassing materials consisting of gaseous material, molten metal, and carbonized plastic are sucked through the first and second labyrinth walls during an arc episode such that the molten metal and the carbonized plastic substantially remain in the first and second labyrinth walls while the gaseous material escapes through the first and second vent channels.
An exemplary embodiment of a fuse housing in accordance with the present disclosure may include a bottom portion with a left labyrinth wall and a right labyrinth wall with a center portion in between. The left labyrinth wall has a left vent channel at its end and the right labyrinth wall has a right vent channel at its end. The bottom portion also has a male weld on a top side and a female weld on a bottom side. The fuse housing also has a top portion with a second male weld on a second top side and a second female weld on a second bottom side. The bottom portion is mated with the top portion such that the male weld of the bottom portion mates with the second female weld of the top portion and the second male weld of the top portion mates with the female weld of the bottom portion.
A fuse housing for safe outgassing of a fuse is disclosed. The fuse housing features labyrinth walls disposed at opposing sides of the fuse housing. The labyrinth walls feature serpentine paths for the flow of outgassing material. At an end of the serpentine paths which is farthest away from a fuse element are vent channels. The vent channels are narrower in depth than that of the serpentine paths of the labyrinth walls, facilitating a suctioning effect during outgassing. Conductive material deposits along the serpentine paths so that the fuse maintains a high OSR rating. The fuse housing includes support structures for connecting a top and bottom portion as well as supporting the placement of terminals and the fuse element.
The fuse housing 100 features, on the bottom portion 108, vent channel 102a on the left side and vent channel 102b on the right side and, on the top portion 110, vent channel 102c on the left side (not visible) and vent channel 102d on the right side (collectively, “vent channels 102”). The fuse housing 100 also features, on the bottom portion 108, a labyrinth wall 104a on the left side and a labyrinth wall 104b on the right side (collectively, “labyrinth walls 104”). Similarly, the top portion 110 includes a pair of labyrinth walls (not shown). In exemplary embodiments, the bottom portion 108 and the top portion 110 are substantially similar in shape and configuration. In exemplary embodiments, the vent channels 102 and the labyrinth walls 104 of the novel fuse housing 100 helps to direct the outflow of gases caused by an arc during interruption (breaking of the fuse element). Further, as described in more detail below, the vent channels 102 and labyrinth walls 104 are designed to control the outflow of gases, reduce the temperature of the gases, and reduce the effects of outgassing, such as visible hot gases, blackened surroundings, etc., that result from the arc energy being dissipated as the fuse breaks.
As used herein, outgassing, or outgassing material, refers to gaseous airborne materials, molten materials, and housing plastic. The molten materials may result from the breaking of the fuse element (intentional weak link) inside the fuse or the heating of the fuse terminals, a busbar to which the fuse is connected, or other conductive material nearby. The plastic material making up the housing of the fuse housing 100 will, when exposed to the violent gases of the outgassing occurrence, will turn into carbon, which is semi-conductive.
The condition that causes a fuse to break is known as an overcurrent event. An overcurrent is any current which exceeds the ampere rating of the wiring, equipment, or devices under conditions of use. The term “overcurrent” includes both overloads and short circuits. The voltage rating, as marked on the fuse, indicates the maximum voltage of the circuit for which the fuse is designed to operate safely in the event of an overcurrent.
The fuse housing 100 further includes a fuse element 114, in accordance with exemplary embodiments. A left terminal 112a is connected to the fuse element 114 on a left side of the fuse housing 100, while a right terminal 112b is connected to the fuse element on a right side of the fuse housing 100 (collectively, “terminals 112”). The fuse element 114 is centrally located within the fuse housing 100 and disposed above ribs 106. The fuse element 114 is the “intentional weak point” of the fuse, designed to break at the rated voltage.
The ribs 106 of the fuse housing 100 are raised portions of a wall of the fuse housing. In the bottom portion 108, the wall would be the bottom or floor, in the case of the top portion 110, the wall would be the top or ceiling (not shown). The fuse element 114 of the fuse is disposed above the ribs 106. Multiple rows of zig-zag-shaped ribs 106 occupy a central portion of the fuse housing 100. However, the ribs 106 may assume any of a variety of shapes besides the zig-zag configuration shown, may be sized differently, and may feature more or fewer rows than are shown. Ultimately, the ribs 106 increase the surface area of the central portion of the fuse housing 100. The ribs 106 may be formed by a molding process when bottom portion 108 and top portion 110 of the fuse housing 100 are formed.
In an exemplary embodiment, the top portion 110 of the fuse housing 100 is identical to the bottom portion 108, and further includes the vent channels 102, labyrinth walls 104, and ribs 106. In an alternative embodiment, the top portion 110 includes some, but not all features of the bottom portion 108. In an exemplary embodiment, the vent channels 102, labyrinth walls 104, ribs 106, receiving apertures 202, cylindrical protrusions 204, male weld 206, and female weld 208, may be formed as a unitary structure by a molding process when the fuse housing 100 is manufactured.
Overcurrent and high voltage conditions can cause unfavorable open-state resistance results. Directing and controlling the outflow of gases caused by the arc during interruption is essential for the performance of a fuse. By directing and controlling the outflow of gases, a well-planned fuse housing design, such as in the exemplary fuse housing 100, is able to reduce the temperature of the gases produced. In an exemplary embodiment, the fuse housing 100 is also able to reduce the physical and observable effects of outgassing.
As explained above, the arc energy to be dissipated in a 48V system is significantly higher than that of a 12V system. Housing strength, outgassing, and Open State Resistance (OSR) become a significantly higher challenge for 48V systems than for the lower voltage systems. Typically listed as a fuse parameter, OSR is a test condition in which the resistance of the fuse is measured after the fuse breaks. Because the purpose of the fuse is to break so as to create an open circuit and protect other circuitry, a broken fuse ideally has as high a resistance as possible, blocking any current from reaching the protected circuitry. A fuse specification may state, for example, “Open State Resistance (after fuse opening)>1 MOhm”.
It may be the case, however, that a poorly designed fuse will nevertheless transmit current across its terminals after the fuse breaks. Despite there being no fuse element between the terminals of the fuse, the arc energy and outgassing that coincides with the breaking of the fuse may cause residue, such as electrically conductive residue from the fuse element, to remain within the fuse housing. When this occurs, there may be an electrically conductive path formed along the debris path that is sufficient for current to travel across the terminals. This phenomenon is known as creeping and causes the fuse to have a low OSR rating. Further, a low OSR rating means that the fuse has not fulfilled its intended purpose: to prevent damage to other components in the circuitry, due to the current still traveling across the fuse despite the fuse element being broken.
When a fuse is broken, due to an overcurrent condition, hot gases are created by the sudden appearance of an arc. The temperature of the arc may be greater than 6000 ° C. up to 20,000 ° C. during the interruption, for example. The suddenly increased air temperature, hot gases, and molten material create a significant pressure increase (shock wave) inside the fuse housing that will try to exit the housing very quickly, if possible. The molten material results from the breaking of the fuse element, or the heating of the fuse terminals, a busbar to which the fuse is connected, or other conductive material nearby. The housing plastic itself, when exposed to these same violent gases, will turn into carbon, which is semi-conductive. The resulting explosion of outgassing materials inside the fuse is thus a combination of hot gases, molten materials, and carbonized plastic materials.
The fuse may operate without vents, such that all the outgassing material stays within the housing of the fuse. This may be preferred in some environments where the messy aftereffects of the blown fuse are to be avoided. However, all molten material (from the copper element to the housing walls) will stay in the fuse. Particularly if the area around the fuse element is small, this may result in the fuse having too low an OSR (and unreliable fuse protection). But, if there is an opening somewhere in the fuse housing, the outgassing will exit there and the gases will transport molten and vaporized copper and carbonized semi-conductive plastic materials of the housing, to locations external to the fuse housing.
So, while some outgassing is acceptable (and even unavoidable) when the fuse breaks, to maintain a good OSR specification, the outgassing of the fuse should be reduced or controlled as much as possible. The vent channels 102 and labyrinth walls 104 of the novel fuse housing 100 are designed to strategically control the outgassing that occurs when the fuse breaks such that the OSR of the fuse remains very high. As illustrated in
The labyrinth walls 104 are used to direct and spread particles and gases of the outgassing material. The serpentine path of the labyrinth walls 104 allows the resulting debris to stick to more surfaces, which, in some embodiments, helps to reduce the build-up of conductive material and conductive paths, thus improving the OSR of the fuse housing 100. Further, in exemplary embodiments, the vent channels 102, disposed at the farthest end of the serpentine path from the fuse element 114, are narrower in depth than that of the serpentine paths of the labyrinth walls 104, facilitating a suctioning effect during outgassing.
The fuse housing 100 includes the top portion 110 that secures to the bottom portion 108, as illustrated in
In exemplary embodiments, the labyrinth walls 104 cools the outgas sing material as it travels the serpentine passages of the walls formed by the raised structures and leaves the fuse housing 100 through the vent channels 102. The labyrinth walls 104 may thus be thought of as mufflers of the outgassing material.
The labyrinth walls may be modified in a variety of ways. The labyrinth walls may be replicated, side by side, one, two, three, or more times, depending on the size of the fuse housing. Or, the shape of the labyrinth walls may be changed. Or, the edges of the “p” portion, the “d” portion, the “q” portion, and/or the “b” portion may be modified, such as by adding “teeth”, “zigzags”, scallops, and so on. Fuse designers of ordinary skill in the art will recognize a number of different ways in which the design of the labyrinth walls may change, while still providing the outgassing protection described herein.
In the simplified perspective view of the left vent channel 102a of
In exemplary embodiments, the depth 308 of the vent channel 102 is kept somewhat small, relative to the depth of the labyrinth wall 104. This relatively small depth prevents too much debris from exiting the fuse housing 100 while nevertheless allowing some outgassing materials to escape and escape very quickly. In an exemplary embodiment, a large quantity of gaseous materials can exit the vent channel 102 while only a small amount of molten material escapes.
In exemplary embodiments, the depth 308 of the vent channel 102 is small, relative to the depth of the labyrinth walls 104, so as to encourage very fast outgassing of debris from the fuse housing. In one embodiment, the depth 308 of the vent channel 102 (
By combining the two features of the fuse housing 100, the vent channels 102 and the labyrinth walls 104, the performance of the fuse is controlled, in some embodiments, through the venting that takes place and control of the OSR. The vent channels 102 and labyrinth walls 104 help to direct the outflow of gases caused by the arc following the overcurrent condition. The novel features (vent channels 102 and labyrinth walls 104) further control the outflow of the gases by the combination of a serpentine path of the labyrinth walls 104 and the thin gap of the vent channel 102 for the expulsion of outgassing material. The vent channels 102 and labyrinth walls 104 further help to reduce the high temperature of the gases in the outgassing material, in some embodiments, by creating a path for their quick movement and an exit path through the fuse housing 100. Further, in exemplary embodiments, the vent channels 102 and labyrinth walls 104 of the fuse housing 100 reduce the effects of outgassing (visible hot gases, blackened surroundings) because, on the way out of the fuse housing, the gases deposit copper (of the fuse element) and graphite (carbonized plastic of the housing) on the labyrinth walls.
In an exemplary embodiment, the thickness of the housing walls behind the ribs 106 is 0.6 millimeters (mm) while the thickness of the ribs is 0.9 mm. Thus, while material is deposited on them, the ribs 106 are not thick enough to block egress of the outgassing material toward the labyrinth walls 104. In an exemplary embodiment, the distance from the fuse element 114 to the top of the ribs 106 is sufficient that the ribs do not block the outflow of gases. The ribs 106 thus hide and distribute the conductive copper and plastic between each row of ribs.
In
Thus, due to the axial symmetry of the top portion 110 and the bottom portion 108, the outgassing has four path, as the outgassing will travel both “under” and “over the terminals 112: : 1) to the left of the fuse element 114, under the terminal 112a, through the labyrinth wall 104a, and out the vent channel 102a (of the bottom portion 108); 2) to the right of the fuse element 114, under the terminal 112b, through the labyrinth wall 104b, and out the vent channel 102b (of the bottom portion 108); 3) to the left of the fuse element 114, above the terminal 112a, through the labyrinth wall 104a, and out the vent channel (of the top portion 110) and 4) to the right of the fuse element 114, above the terminal 112b, through the labyrinth wall 104b, and out the vent channel 102b (of the top portion 110).
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.
This application is a continuation of, and claims the benefit of priority to, U.S. patent application Ser. No. 17/224,583, filed Apr. 7, 2021, entitled “FUSE HOUSING FOR SAFE OUTGASSING,” which application is incorporated herein by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 17224583 | Apr 2021 | US |
| Child | 17523186 | US |
