Design and manufacture of printed fuses

Abstract

The present disclosure provides a power fuse for protecting electrical loads subjected to transient load current cycling events in a DC power system. The power fuse includes at least one fuse assembly, the at least one fuse assembly including a slender planar substrate, a plurality of fusible weak points, and a conductor. The weak points are formed on the substrate and are longitudinally spaced apart from each other on the substrate. The conductor is disposed separately from the substrate and the weak points. The conductor includes a solid, slender metal strip having no embossed weak point openings therein, thereby avoiding thermomechanical fatigue strains in the conductor when subjected to the transient load current cycling event. The solid, slender metal strip includes a coplanar connecting section and an inclined extension section, the coplanar connecting section being mounted to a corresponding one of the weak points, and the inclined extension section being bent out of the plane of the connecting section to extend above the substrate.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application is related in subject matter to, and claims the benefit of and priority to, U.S. patent application serial number 17 / 185,537, filed on February 25, 2021, and entitled “Design and Fabrication of Printed Fuse,” the complete disclosure of which is hereby incorporated by reference in its entirety. Background Art

[0003] The technical field of the present disclosure relates generally to circuit protection fuses, and more particularly to the manufacture of power fuses including fuse assemblies that are resistant to thermal mechanical strain fatigue.

[0004] Fuses are widely used as overcurrent protection devices to prevent costly damage to electrical circuits. Fuse terminals typically form an electrical connection between a power source or supply and an electrical component or combination of components arranged in the circuit. One or more fuses or fuse elements, or a fuse assembly, are connected between the fuse terminals so that when the current flowing through the fuse exceeds a predetermined limit, the fuse element melts and disconnects the circuit or circuits passing through the fuse, preventing damage to the electrical components.

[0005] Full-range power fuses are capable of operating in high-voltage power distribution to safely interrupt both relatively high fault currents and relatively low fault currents with equal effectiveness. Given the increasing variety of power systems, known fuses of this type are disadvantageous in several respects. It would be desirable to improve full-range power fuses to meet market demands. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Non-limiting and non-exhaustive embodiments are described with reference to the following figures, wherein like reference numerals refer to like parts throughout the various figures unless otherwise specified.

[0007] Figure 1 An exemplary transient current pulse curve generated in an electric power system is shown.

[0008] Figure 2A is a perspective view of a known power fuse.

[0009] Figure 2B yes Figure 2A A perspective view of a fuse assembly of a power fuse is shown in FIG.

[0010] Figure 2C yes Figure 2B Schematic diagram of the weak points of the melt component shown in .

[0011] Figure 2D is shown in the load current cycle event Figure 2B Schematic diagram of the weak points of the melt component shown in .

[0012] Figure 2E is shown to fail after a load current cycling event Figure 2E Schematic diagram of the weak points of the melt component shown in .

[0013] Figure 3 is a partial perspective view of an exemplary power fuse.

[0014] Figure 4 yes Figure 3 An enlarged view of the fuse assembly of the power fuse is shown in FIG.

[0015] Figure 5 Shown Figure 4 The substrate and weak points of the melt component are shown in Figure 4.

[0016] Figure 6 is an enlarged cross-sectional view of a portion of an exemplary melt assembly.

[0017] Figure 7 It shows Figure 4 Schematic diagram of the arc in the melt assembly shown in .

[0018] Figure 8 It is used for manufacturing Figures 3 to 7 A schematic diagram of an exemplary method for disabling a power fuse is shown in FIG.

[0019] Figure 9 It shows Figure 8 Flowchart of the method shown.

[0020] Figure 10A yes Figure 3 A perspective view of another exemplary fuse assembly of a power fuse is shown in FIG.

[0021] Figure 10B It was intercepted along line 10B-10B Figure 10A A cross-sectional view of the melt assembly is shown.

[0022] Figure 10C yes Figure 10A An enlarged cross-sectional view of a portion of a melt assembly is shown.

[0023] Figure 11 is a flow chart of another exemplary method of manufacturing a power fuse.

[0024] Figure 12 yes Figure 11 Schematic diagram of attaching a conductor to a weak point in the illustrated method.

[0025] Figure 13A yes Figure 3A top view of one or more exemplary fuse assemblies of a power fuse is shown in FIG.

[0026] Figure 13B It is intercepted along line 13B-13B Figure 13A A cross-sectional view of the melt assembly is shown.

[0027] Figure 13C It is intercepted along line 13B-13B Figure 13A A cross-sectional view of a melt assembly shown, wherein the melt has Figure 13B An alternative configuration to the one shown for the melt.

[0028] Figure 14 yes Figure 3 A schematic diagram of an exemplary coupling mechanism between a weak point of a power fuse and a conductor is shown. DETAILED DESCRIPTION

[0029] Recent advances in electric vehicle technology present unique challenges for fuse manufacturers. Electric vehicle manufacturers are looking for fusible circuit protection for electrical distribution systems that operate at much higher voltages than the vehicle's conventional electrical distribution system, while also seeking smaller fuses to meet the specifications and demands of electric vehicles.

[0030] The electrical systems for conventional internal combustion engine powered vehicles operate at relatively low voltages (typically equal to or less than about 48 VDC). However, the electrical systems for electric vehicles (referred to herein as electric vehicles (EVs)) operate at much higher voltages. The relatively high voltage systems of EVs (e.g., 200 VDC and above) typically enable batteries to store more energy from the power source and provide more energy to the vehicle's electric motor with lower losses (e.g., heat losses) than conventional batteries for internal combustion engines that store energy at 12 volts (V) or 24 V (and more recently, 48 V power systems).

[0031] EV original equipment manufacturers (OEMs) use circuit protection fuses to protect electrical loads in all battery electric vehicles (BEVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs). Within each EV type, EV manufacturers seek to maximize the EV's range per battery charge while reducing the cost of ownership. Achieving these goals drives changes in the EV system's energy storage and power delivery, as well as the size, volume, and mass of the vehicle components that carry that power system. Smaller and / or lighter vehicles can meet these demands more efficiently than larger, heavier vehicles. Consequently, all EV components are now being scrutinized for potential size, weight, and cost savings.

[0032] Generally speaking, larger components tend to have higher associated material costs, tend to increase the overall size of the EV or take up excessive space in the ever-shrinking vehicle volume, and tend to introduce greater mass, which directly reduces the vehicle range on a single battery charge. However, known high-voltage circuit protection fuses are relatively large and relatively heavy components. Historically, and for good reason, to meet the demands of high-voltage power systems, circuit protection fuses have tended to increase in size compared to lower voltage systems. As a result, the existing fuses required to protect high-voltage EV power systems are much larger than the existing fuses required to protect the lower voltage power systems of conventional internal combustion engine-powered vehicles. Smaller and lighter high-voltage power fuses are needed to meet the needs of EV manufacturers without sacrificing circuit protection performance.

[0033] The power systems for prior art EVs may operate at voltages up to 450 VDC or even higher. The increased power system voltage advantageously delivers more power to the EV per battery charge. However, the operating conditions for electrical fuses in such high voltage power systems are more demanding than those in lower voltage systems. Specifically, for higher voltage power systems, specifications related to arc conditions when the fuse opens can be particularly difficult to meet, especially when combined with the industry preference to reduce the size of electrical fuses. The current cycling loads imposed on power fuses by prior art EVs tend to also impose mechanical strain and wear, which can lead to premature failure of conventional fuses. Although known power fuses are currently available to EV OEMs for use in high voltage circuits for prior art EV applications, the size and weight (not to mention the cost) of conventional power fuses that can meet the high voltage power system requirements for EVs are prohibitive for implementation in new EVs.

[0034] Providing relatively small power fuses that can handle the high currents and high battery voltages of prior art EV power systems while still providing acceptable interrupting performance when the fuse operates at high voltages is challenging, to say the least. There exists a long-standing and unmet need in the art for improvements.

[0035] Although described in the context of EV applications and specific types and ratings of fuses, the benefits of the present disclosure are not necessarily limited to EV applications or the specific types or ratings described. Rather, it is believed that the benefits of the present disclosure are more broadly applicable to many different power system applications and can also be practiced, in part or in whole, to construct different types of fuses having ratings similar to or different from those discussed herein.

[0036] Figure 1An exemplary current drive curve 100 in an EV power system application is shown, which may make the fuse, and in particular one or more fuse elements thereof, susceptible to load current cycling fatigue. Figure 1 The vertical axis is shown in FIG, and time is shown along the horizontal axis. In a typical EV power system application, power fuses are used as circuit protection devices to prevent damage to the electrical loads caused by electrical fault conditions. The power system may operate at voltages greater than 500V and / or currents greater than 150 amperes (A). Considering Figure 1 For example, an EV power system experiences large, seemingly random variations in current load, for example, between -250A and 150A, within a relatively short period of time. This seemingly random variation in current produces a sequence of current pulses of varying magnitudes caused by seemingly random driving habits based on the EV vehicle's driver's actions, traffic conditions, and / or road conditions. This creates a nearly infinite number of current load cycles on the EV drive motor, main drive battery, and any protective power fuses included in the system.

[0037] exist Figure 1 Such random current load conditions exemplified in the current pulse curve of are cyclic in nature for both the acceleration of the EV (corresponding to battery depletion) and the deceleration of the EV (corresponding to regenerative battery charging). This current cyclic load imposes thermal cycling stresses on the melt through the Joule effect heating process, and more specifically, in the weak points of the melt assembly in the power fuse. Specifically, this thermal cycling load of the melt imposes mechanical expansion and contraction cycles on the melt weak points. This repeated mechanical cyclic loading of the melt weak points imposes cumulative strains, thereby damaging the weak points to the point of failure over time. For the purposes of this specification, this thermomechanical process and phenomenon is referred to herein as fuse fatigue. As further explained below, fuse fatigue is primarily attributed to the creep strains that the fuse endures as it endures the driving curve. The heat generated in the melt weak points is the primary mechanism that causes fuse fatigue to occur.

[0038] Figure 2A A known high-voltage power fuse 200 designed for use in an EV power system is shown. Power fuse 200 includes a housing 202, terminal strips 204, 206 configured to connect to a line-side circuit and a load-side circuit, and a fuse assembly 208 that electrically connects the terminal strips 204, 206 via terminal contact blocks 222, 224 disposed on end plates 226, 228. When subjected to a predetermined current condition, at least a portion of fuse assembly 208 melts, ruptures, or otherwise structurally fails, breaking the circuit path between terminal strips 204, 206. Thus, the load-side circuit is electrically isolated from the line-side circuit to protect load-side circuit components from damage in the event of an electrical fault condition.

[0039] Figure 2B Melt assembly 208 is shown in further detail. Melt assembly 208 is generally formed from a strip of conductive material into a series of coplanar segments 240 connected by angled segments 242, 244. Angle segments 242, 244 are formed out of the plane of planar portion 240 or are bent out of the plane.

[0040] In the example shown, planar section 240 defines a plurality of sections having reduced cross-sectional areas 241 (referred to in the art as weak points). Weak points 241 are defined by openings in planar section 240. Weak points 241 correspond to narrow portions of section 240 between adjacent openings. When current flows through melt assembly 208, the reduced cross-sectional areas at weak points 241 will experience higher heat concentrations than the remainder of melt assembly 208.

[0041] It has been found that the weak point 241 of the melt assembly 208 manufactured by metal stamping or punching is disadvantageous for EV applications with the type of cyclic current loads described above. Such stamped melt designs undesirably introduce mechanical strain and stress into the melt weak point 241, which often results in a shorter fuse life. This short fuse life manifests itself in the form of nuisance fuse operation due to mechanical fatigue of the melt at the weak point 241.

[0042] Figure 2C A cross-sectional view of the metal sheet 250 is shown after an opening 252 has been punched through the metal sheet 250. Micro-tearing 254 occurs along the boundaries 256 of the opening 252 after the punching or coining process.

[0043] like Figure 2D and Figure 2E As shown, the weak point 241 of the melt assembly 208 experiences repeated high current pulses and cycling current events ( Figure 2D ), which results in metal fatigue caused by grain boundary damage, and then fracture extension and failure occur at the weak point 241 in the melt component 208 ( Figure 2E The mechanical constraints of the melt assembly 208 are inherent in the design and manufacture of the stamped melt, and unfortunately, have been found to promote in-plane buckling of the weak point 241 during repeated load current cycles. This in-plane buckling is the result of damage to the metal grain boundaries at locations where separation or slip occurs between adjacent metal grains. This buckling of the weak point 241 occurs over time and is accelerated and more pronounced with higher transient current pulses. The larger the heating and cooling increments in the transient current pulse, the greater the mechanical impact, and therefore the greater the in-situ buckling deformation of the weak point 241.

[0044] Repeated physical mechanical manipulation of the metal, caused by the heating effect of the transient current pulse, in turn causes changes in the molten metal's grain structure. These mechanical manipulations are sometimes referred to as working the metal. Working the metal leads to the strengthening of grain boundaries, where adjacent grains become tightly confined to adjacent grains. Excessive working of the metal can lead to the destruction of grain boundaries, where grains slip past each other, resulting in so-called slip bands or slip planes. This slip and separation between grains causes a localized increase in electrical resistance, thereby accelerating the fatigue process by increasing the heating effect of the current pulse. The formation of slip bands is where fatigue fracture initially begins.

[0045] The inventors have discovered that the manufacturing method of stamping or punching metal to form the fuse assembly 208 causes localized slip bands on all stamped edges of the fuse weak point 241 because the stamping process that forms the weak point 241 is a shearing and tearing mechanical process. This tearing process pre-stresses the weak point 241 with numerous slip band areas. Slip bands and fatigue fracture, combined with the aforementioned buckling due to thermal effects, ultimately lead to premature structural failure of the weak point 241, which is unrelated to the electrical fault condition. This premature failure mode, which is unrelated to problematic electrical conditions in the power system, is sometimes referred to as nuisance operation of the fuse. Since, once the fuse fails, the circuit connected to the fuse will no longer function until the fuse is replaced, avoiding this nuisance operation in EV power systems is highly desirable from the perspective of EV manufacturers and consumers. Indeed, given the growing interest in EV vehicles and their power systems, the impact of fuse fatigue is considered a negative critical-to-quality (CTQ) attribute in vehicle design.

[0046] Therefore, improved melts and methods for producing melts that include fatigue-resistant weak points are highly desirable.

[0047] The following describes exemplary embodiments of melts and methods for producing such melts that advantageously avoid strain damage at weak points during the manufacturing process, such as stamping or coining, while also providing an effective arc extinguishing mechanism. The weak points in the exemplary embodiments are formed directly on a planar substrate, thereby avoiding microtears from the stamping or coining process. The weak points are connected by a separately manufactured conductor having a coplanar connecting section and an angled connecting section for effective arc extinguishing.

[0048] Although described below with reference to specific embodiments, such description is for illustration and not limitation. The significant benefits of the inventive concept will now be explained with reference to the exemplary embodiments shown in the accompanying drawings. Method aspects will be partially apparent and partially explicitly discussed in the following discussion.

[0049] Now refer to Figures 3 to 7 , shows an exemplary power fuse 300. The power fuse 300 includes at least one fuse assembly 302 ( Figure 3 ). The power fuse 300 may include a housing 308. The power fuse 300 further includes terminal strips 304, 306, which are configured to connect the power fuse 300 to the line-side circuit and the load-side circuit. The electrical connection of the fuse assembly 302 is completed through the terminal contact blocks 322, 324 provided on the end plates 332, 334 and the terminal strips 304, 306. When subjected to a predetermined current condition, at least a portion of the fuse assembly 302 melts, ruptures, or otherwise structurally fails, and disconnects the circuit path between the terminal strips 304, 306. Thus, the load-side circuit is electrically isolated from the line-side circuit to protect the load-side circuit components from damage when an electrical fault condition occurs.

[0050] Figure 4 Exemplary melt assembly 302 is shown in further detail. Melt assembly 302 includes substrate 310, plurality of weak points 312, and conductor 314.

[0051] The substrate 310 may be a planar substrate ( Figure 5 ). The substrate 310 can be elongated. In an exemplary embodiment, the top surface of the substrate 310 is rectangular. In some embodiments, the substrate 310 is ceramic. In one example, the substrate is an alumina ceramic. Alumina substrates have a relatively high thermal conductivity (e.g., about 30 Wm -1 K -1 ), which helps dissipate heat from the weak point 312.

[0052] In an exemplary embodiment, weak points 312 are formed on substrate 310. The number of weak points 312 can be three or another number, such as one, two, or four, that enables melt assembly 302 to function as described herein. Weak points 312 are spaced apart from one another. In some embodiments, weak points 312 are spaced apart from one another along the longitudinal direction of substrate 310. Weak points 312 are made of a conductive material such as copper. Weak points 312 can be printed on substrate 310 using known techniques. However, in some embodiments, weak points 312 can be formed on substrate 310 using techniques other than printing. Multiple layers of weak points 312 can be formed on top of each other to vary the overall thickness of weak points 312. Therefore, the resistance and performance of weak points 312 are more controllable than weak points formed by metal stamping or punching. Because the weak point 312 is formed without mechanical micro-tearing from mechanical manufacturing processes like metal stamping or punching, the weak point 312 is not subject to load current cycling fatigue like the weak point 241 of the known fuse 200, especially under the large and seemingly random cyclic current variations found in the DC power system of an EV.

[0053] In some embodiments, melt assembly 302 further includes a dielectric layer 316 disposed between substrate 310 and weak point 312 ( Figure 6 In an exemplary embodiment, dielectric layer 316 may be glass or another suitable dielectric material known in the art. If weak point 312 is formed solely of conductive material, the material separates when the conductive material melts under melting conditions, but can reconnect, allowing the circuit to reconnect. To minimize this reconnection of weak point 312 and allow power fuse 300 to operate under predetermined current conditions, a dielectric, glass-based layer 316 is deposited beneath weak point 312. The material for dielectric layer 316 is selected so that it melts at a higher temperature than weak point 312, but at a temperature sufficiently low to allow diffusion. The melting temperature of dielectric layer 316 is approximately 25°C to 50°C higher than the maximum melting temperature of weak point 312. This temperature range allows dielectric layer 316 to be mechanically stable during the melting process to support weak point 312 while allowing the dielectric material to diffuse into weak point 312. The melting temperature of dielectric layer 316 can vary depending on the material. Diffusion is desirable for two reasons. First, it provides a method to adjust the resistance of the weak point, where more melting results in more diffusion and higher resistivity. Second, the diffused dielectric layer 316 changes the wetting characteristics of the conductor and does not allow the melted weak point 312 to reattach.

[0054] See again Figure 4 , the weak point 312 of the melt assembly is connected by a conductor 314. In an exemplary embodiment, conductor 314 is made from a solid, elongated bar of metal. Conductor 314 can be manufactured by stamping or coining the solid, elongated bar of metal. Conductor 314 is thicker than weak point 312. Therefore, under predetermined current conditions, weak point 312 experiences more heat than conductor 314 and opens before conductor 314. Consequently, when subjected to a transient load current cycling event, conductor 314 does not have a coined weak point opening and is thus protected from thermomechanical fatigue strain.

[0055] In an exemplary embodiment, conductor 314 includes a coplanar connecting section 318 and an angled extending section 320. The angled extending section 320 bends out of the plane of the coplanar connecting section 318. Conductor 314 may further include a first terminal tab and a second terminal tab extending from the angled extending section 320. Conductor 314 is coupled to terminal contact blocks 322, 324 via terminal tabs 326, 328.

[0056] In a contemplated embodiment, the coplanar connecting section 318 is mounted on a corresponding one of the weak points 312. Alternatively, the coplanar connecting section 318 is mounted on the substrate 310 and connected to the weak points 312. Thus, the obliquely extending section 320 extends above the substrate 310 between the weak points 312, and the first and second terminal tabs 326, 328 can extend coplanar with each other in a plane spaced apart from the coplanar connecting section 318 and the substrate 310. The planes of the first and second terminal tabs 326, 328 can extend parallel to the coplanar connecting section 318 and the substrate 310.

[0057] In the exemplary embodiment, the power fuse 300 includes three fuse assemblies 302 ( Figure 3 ). In other embodiments, the power fuse 300 can include other numbers of fuse assemblies 302, such as one and two, that enable the power fuse 300 to operate as described herein. Multiple fuse assemblies 302 can be connected in parallel to each other to increase the rating of the power fuse 300 without increasing the physical size of the power fuse 300. The fuse assemblies 302 can be arranged so that two adjacent fuse assemblies are mirror images of each other. The fuse assemblies 302 can be stacked together with the substrate of one fuse assembly facing the conductor of another fuse assembly.

[0058] A full range fuse can be implemented by using at least one melt assembly 302 that responds to relatively low current operation (or overload fault) and at least one melt assembly 302 that responds to relatively high current operation (or short circuit fault). Melt assemblies 302 can also be used in non-full range fuses.

[0059] In an exemplary embodiment, the power fuse 300 may further include an arc-quenching filler 330 ( Figure 7 ). An arc-quenching filler 330 surrounds at least a portion of the melt assembly 302. The arc-quenching filler 330 can be disposed below the angled extension portion 320. The arc-quenching filler 330 can also be disposed above the angled extension section 320, the coplanar connection section 318, and the weak point 312. The arc-quenching filler 330 can be introduced into the housing 308 via one or more filling openings in one of the end plates 332, 334, which are sealed with a plug (not shown). In various embodiments, the plug can be made of steel, plastic, or other materials. In other embodiments, one or more filling holes can be disposed in other locations, including but not limited to the housing 308, to facilitate the introduction of the arc-quenching filler 330.

[0060] In one contemplated embodiment, arc-quenching filler 330 is comprised of quartz silica sand and a sodium silicate binder. Quartz sand has relatively high heat conduction and absorption capabilities in its loosely packed state, but can be silicated to provide improved performance. For example, a liquid sodium silicate solution can be added to the sand, and the free water can then be dried out. A separate arc barrier material (not shown) can also be provided to prevent arcing from reaching either end of terminal tabs 326, 328.

[0061] In an exemplary embodiment, the melt assembly 302 provides contact of the arc to an arc extinguishing medium, such as sand in the arc extinguishing filler 330. When the weak point 312 melts under predetermined current conditions, the arc initiates at the weak point 312. As the arc grows in length, it migrates from the weak point 312 and the substrate 310 and along the angled extension section 320 into the surrounding arc extinguishing filler 330 for efficient cooling and faster arc extinguishing.

[0062] Figure 8 and Figure 9 An exemplary method 900 of manufacturing a power fuse for protecting an electrical load subjected to transient load current cycling events in a DC power system is shown. Figure 8 A schematic diagram of method 900 is shown, and Figure 9 A flow chart of method 900 is shown. Method 900 includes forming 902 a plurality of fusible weak points on a planar substrate such that the plurality of fusible weak points are longitudinally spaced apart from one another on the planar substrate. Method 900 also includes providing 904 a conductor separated from the planar substrate and the plurality of weak points. The number of coplanar connection sections of the conductor may be the same as the number of weak points formed on the planar substrate. Method 900 also includes mounting 906 the coplanar connection sections of the conductor to corresponding weak points of the plurality of weak points. Thus, the inclined extension portion of the conductor extends above the elongated planar substrate between the plurality of fusible weak points, and the first terminal tab and the second terminal tab of the conductor extend coplanar with one another in a plane parallel to but spaced apart from the coplanar connection sections and the substrate. In one example, the coplanar connection sections of the conductor are brazed to the weak points. In some embodiments, the conductor is formed in one piece. The conductor 800 may include a support bridge 802 ( Figure 8 ). The method 900 may also include removing the support bridge after the coplanar connecting sections of the conductors have been installed over corresponding weak points of the plurality of weak points.

[0063] Figures 10A to 10C Another exemplary fuse assembly 1302 included in power fuse 300 is shown. Figure 10A is a perspective view of melt assembly 1302 . Figure 10B It is along Figure 10A A cross-sectional view of melt assembly 1302 is shown taken along line 10B-10B. Figure 10C yes Figure 10B 1302. Unlike melt assembly 302, substrate 310 is integral (see Figure 4 ), the substrates 1310 of the melt assembly 1302 are separated from each other. Weak point 1312 and its substrate 1310 can be collectively referred to as weak point pad 1203. Substrate 310 is not normally conductive, but can become conductive in a DC arc plasma. As a result, the arc may not be extinguished within the desired time period, resulting in damage to the melt assembly 302 and the power fuse 300.

[0064] In contrast, the substrates 1310 of the melt assembly 1302 are separated from each other. An arc-quenching filler 330 can be filled in the fuse 300, including the space separating adjacent substrates 1310. Thus, the arc is suppressed by the arc-quenching filler 330.

[0065] In the exemplary embodiment, weak point 1312 is included in melt assembly 1302. With weak point 312 (which is a block) (see Figure 5 ), the weak point 1312 has one or more openings 1208 ( Figure 10A , see also Figure 12 ). Opening 1208 increases the number of weak points 1312 in a weak point pad 1203. Unlike a single weak point 312, weak point 1312 includes additional weak points defined by opening 1208 in addition to weak point 1312 itself. In the illustrated embodiment, opening 1208 is shown as a rectangle for illustration purposes only. Opening 1208 can have other shapes, such as circular, oval, square, or irregular shapes, which enable opening 1208 to function as described herein. In some embodiments, melt assembly 1302 includes weak points 312 instead of weak point 1312. In other embodiments, melt assembly 1302 includes a mixture of weak points 312 and weak points 1312.

[0066] In some embodiments, the substrate 1310 may be a rod having an increased thickness compared to a substrate formed into a sheet. The rod may be a square rod or a rectangular rod, wherein the axial profile 1020 is a square or rectangular ( Figure 10B ). Axial profile 1020 may be other shapes that enable substrate 1310 to function as described herein. Compared to a thin sheet substrate, rod substrate 1310 has increased mass, which increases the thermal conductivity of substrate 1310 for transferring heat away from conductors 314 and weak points 312, 1312.

[0067] Figure 1113 is a flow chart of another exemplary method 1100 for manufacturing a power fuse for protecting an electrical load subjected to transient load current events in a DC power system. Method 1100 includes forming 1102 a plurality of fusible weaknesses on a plurality of substrates. The plurality of fusible weaknesses 1312 can be formed on an initially unitary substrate 1310 and then separated from one another by cutting substrate 1310 into a plurality of substrates, each substrate 1310 having one weakness 1312. Alternatively, substrate 1310 can be provided as separate pieces, and one weakness 1312 can be formed on one substrate 1310. Weakness 1312 can be formed on substrate 1310 by printing the weakness onto substrate 1310. Method 1100 also includes providing 904 a conductor separate from the plurality of substrates and the plurality of weaknesses. The method 1100 also includes attaching 1106 the coplanar connecting sections of the conductor to respective weak points in the plurality of weak points such that the plurality of weak points are longitudinally spaced apart from one another along the conductor and the plurality of planar substrates are longitudinally spaced apart from one another along the conductor. In other words, the weak points 1312 are spaced apart from one another along the longitudinal direction of the conductor 314 and the substrates 1310 are spaced apart from one another along the longitudinal direction of the conductor 314.

[0068] In some embodiments, when attaching 1106 weak points 1312 to conductor 314, solder 1110 is applied to weak point pads 1203, with substrate 1310 initially being integral. In one example, solder 1110 is applied to substrate 1310 by screen printing solder 1110 onto substrate 1310 and reflowing solder 1110 onto substrate 1310. Weak points 1312 are then separated from one another so that each substrate 1310 includes one weak point 1312. Weak point pads 1203 are placed in a tape and reel or matrix tray. Solder paste or flux (not shown) is applied to coplanar connecting sections 318 of conductor 314. In one example, solder paste or flux is placed on the side of coplanar connecting sections 318 opposite the valley 1112 formed by coplanar connecting sections 318 and their adjacent obliquely extending sections 320. Conductor 314 is placed over weak point pads 1203. Alternatively, weak spot pad 1203 is placed above conductor 314. In another example, solder paste or flux is placed on the same side of coplanar connection section 318 as valley 1112. Weak spot pad 1203 is picked up and placed in valley 1112 of conductor 314. Once weak spot pad 1203 and conductor 314 are placed together, conductor 314 and weak spot pad 1203 are reflowed. In one example, weight can be applied to the top of substrate 1310 or coplanar connection section 318 to facilitate reflow.

[0069] Figure 121 is a schematic diagram of an exemplary embodiment of a coplanar connection section of attached conductor 1106, wherein a weak point 1312 is mounted to the side of conductor 314 opposite valley 1112. Weak point pads 1203 can be arranged with spacing 1202 between adjacent weak point pads 1203 such that a distance 1204 between adjacent weak point pads 1203 is approximately the same as a distance 1206 between adjacent coplanar connection sections 318.

[0070] In an exemplary embodiment, the coplanar connecting section 318 includes two portions 1209 separated by a gap 1210 (see also Figure 10A ). The two portions 1209 are connected by a support bridge 802. The support bridge 802 extends from the two portions 1209 in the same direction as the extending direction of the obliquely extending section 320. When the conductor 314 is installed in the weak point pad 1203, the support bridge and the gap 1210 are used to align the coplanar connection section 318 with the weak point 1312 so that the gap 1210 is aligned with the opening 1208 (see Figure 10A After the coplanar connecting sections 318 of the conductors 314 are attached to the plurality of weak points 1312 , the supporting bridges 802 are removed.

[0071] 13A to 13C Another embodiment of attaching 1106 the coplanar connecting section to respective ones of the plurality of weak points is shown, wherein the plurality of weak points 1312 are mounted on the same side of the coplanar connecting section 318 as the valley 1112 . Figure 13A is a top view of melt assembly 1302-a. Figure 13B and Figure 13C It is along Figure 13A 13B-13B is a cross-sectional view of melt assembly 1302-a taken along line labeled 13B-13B. Figure 13C An alternative configuration of melt assembly 1302-a is shown. Figures 10A-10C) (wherein the weak point pad 1203 is disposed on the side of the coplanar connecting section 318 opposite the valley 1112), the weak point pad 1203 in the melt assembly 1302-a is disposed in the valley 1112. By disposing the weak point pad 1203 in the valley 1112, the arc is formed on the side opposite the weak point 1312 or valley 1112, surrounded by the arc quenching filler 330, thereby improving the arc quenching effect. The dimensions of the conductor 314 and / or the weak point pad 1203 can be modified with respect to the conductor 314 to receive the weak point pad 1203 in the valley 1112 of the conductor 314. In some embodiments, the angled extension section 320 and the support bridge 802 form a receptacle sized to receive the substrate 1310 therein. The angled extension section 320 and the support bridge 802 serve to align and hold the substrate in place during reflow. After the coplanar connecting sections 318 of the conductors 314 are attached to the plurality of weak points 1312 , the supporting bridges 802 are removed.

[0072] Figure 13C An alternative configuration of melt assembly 1302-a is shown. Figure 13B Compared to the melt assembly 1302-a shown, Figure 13C Melt assembly 1302-a is shown as forming a recess 1306 sized to receive weak point 1312 and weak point pad 1203. Thus, weak point 1312 and weak point pad 1203 are self-aligned within coplanar connection section 318. In some embodiments, support bridge 802 can be used for alignment. Due to the ease of self-alignment and / or alignment, the connection between weak point 1312 and coplanar connection section 318 by welding is simplified or even eliminated.

[0073] Figure 14 is a schematic diagram of an exemplary coupling mechanism between substrate 1310 and coplanar connecting section 318. The coupling mechanism can be applied to fuse assembly 302, 1302, 1302-a. In an exemplary embodiment, weak point 1312 is deposited on substrate 1310. First solder 1402 and second solder 1404 are used to couple substrate 1310 to coplanar connecting section 318. The melting temperature of first solder 1402 is higher than the melting temperature of second solder 1404. Therefore, first solder 1402 forms a diffusion barrier for weak point 312, diffusing into first and second solders 1402, 1404 and slowing the melting of first and second solders 1402, 1404, thereby reducing solder joint fatigue that can lead to electrical connection failure and render the fuse inoperable.

[0074] Weak point 312 may be used in place of weak point 1312 , or vice versa, to enable the melt assembly and method to function or operate as described herein.

[0075] It is now believed that the benefits and advantages of the present disclosure have been fully demonstrated in accordance with the disclosed exemplary embodiments.

[0076] Various embodiments of power fuses and fuse assemblies, and methods for manufacturing the same, are described herein, including forming a plurality of weak points on a substrate without stamped weak point openings, thereby avoiding thermomechanical fatigue strains in the fuse assembly when subjected to transient load current cycling events. Furthermore, the fuse assembly includes a conductor having a coplanar connection section mounted on the weak points and an angled extension extending above the substrate, such that an arc-quenching filler can be disposed around at least a portion of the fuse assembly, thereby effectively extinguishing an arc generated after the fuse assembly opens under predetermined current conditions.

[0077] While exemplary embodiments of components, assemblies, and systems have been described, variations of the components, assemblies, and systems may achieve similar advantages and effects. Specifically, the shapes and geometries of the components and assemblies, as well as the relative positions of the components within the assembly, may vary from those described and depicted without departing from the inventive concepts described. Additionally, in certain embodiments, certain components of the assembly may be omitted to accommodate the needs of a particular type of fuse or a particular installation while still providing the performance and functionality required of the fuse.

[0078] An embodiment of a power fuse for protecting electrical loads subjected to transient load current cycling events in a DC power system has been disclosed. The power fuse includes at least one fuse assembly comprising an elongated planar substrate, a plurality of fusible weak points, and a conductor. The plurality of fusible weak points are formed on the planar substrate and longitudinally spaced apart from one another on the planar substrate. The conductor is disposed separately from the planar substrate and the plurality of weak points. The conductor comprises a solid, elongated metal strip having no embossed weak point openings therein, thereby avoiding thermomechanical fatigue strains in the conductor when subjected to the transient load current cycling event. The solid, elongated metal strip includes a coplanar connecting section and an angled extension section, the coplanar connecting section being mounted to a corresponding one of the plurality of weak points on the planar substrate, and the angled extension section being bent out of the plane of the connecting section to extend above the elongated planar substrate between the plurality of fusible weak points. The conductor further includes a first terminal tab and a second terminal tab extending coplanar with each other in a plane parallel to but spaced apart from the connecting section and the substrate.

[0079] Optionally, the power fuse further includes an arc-extinguishing medium surrounding at least a portion of the at least one fuse assembly. The at least one fuse assembly further includes a dielectric layer formed above the substrate and nested between the substrate and the plurality of weak points. The conductor is formed in an integral manner. The substrate is an alumina ceramic. The power fuse further includes a housing enclosing the at least one fuse assembly. The plurality of fusible weak points are printed on the planar substrate. The power fuse has a rated voltage of at least 500V. The power fuse has a rated current of at least 150A. The at least one fuse assembly includes a first fuse assembly and a second fuse assembly electrically connected in parallel to each other.

[0080] A method for manufacturing a power fuse for protecting electrical loads subjected to transient load current cycling events in a DC power system has been disclosed. The method includes forming a plurality of fusible weak points on an elongated planar substrate such that the plurality of fusible weak points are longitudinally spaced apart from one another on the planar substrate. The method also includes providing a conductor separate from the planar substrate and the plurality of weak points. The conductor comprises a solid elongated metal strip having no embossed weak point openings therein, thereby avoiding thermomechanical fatigue strains in the conductor when subjected to the transient load current cycling event. The solid elongated metal strip comprises a coplanar connecting section and an angled extension section that bends out of the plane of the connecting section. The conductor further comprises a first terminal tab and a second terminal tab extending coplanarly with one another. The method also includes mounting the coplanar connecting section of the conductor to corresponding ones of the plurality of weak points on the planar substrate such that the angled extending section of the conductor extends above the elongated planar substrate between the plurality of fusible weak points, and the first terminal tab and the second terminal tab extend coplanar with each other in a plane parallel to but spaced apart from the connecting section and the substrate, thereby completing the first melt assembly.

[0081] Optionally, the method further includes surrounding at least a portion of the first melt assembly with an arc-extinguishing medium. Forming the plurality of weak points includes printing the plurality of weak points on the elongated planar substrate. Forming the plurality of weak points also includes providing a dielectric layer on the substrate, and forming the plurality of weak points above the dielectric layer so as to cover the dielectric layer and nest the dielectric layer between the substrate and the plurality of weak points. Forming the dielectric layer includes printing the dielectric layer on the substrate, and forming the plurality of weak points includes printing the plurality of weak points above the dielectric layer so as to cover the dielectric layer and nest the dielectric layer between the substrate and the plurality of weak points. Providing a conductor also includes forming the conductor in an integral manner. The conductor is formed by a supporting bridge connecting the coplanar connecting sections, and installing the coplanar connecting sections further includes removing the supporting bridge after the coplanar connecting sections of the conductor have been installed over corresponding weak points in the plurality of weak points. The substrate includes alumina ceramic. The method further includes forming a second melt assembly, and electrically connecting the first and second melt assemblies in parallel. The method further includes electrically connecting the first terminal tab and the second terminal tab of the conductor to first and second conductive terminals, and enclosing the first melt assembly with a housing to expose at least a portion of the first and second conductive terminals.

[0082] Another embodiment of a power fuse for protecting electrical loads subjected to transient load current cycling events in a DC power system is disclosed. The power fuse includes at least one fuse assembly comprising a plurality of planar substrates, a plurality of fusible weak points, each formed on one of the plurality of planar substrates, and a conductor. The conductor is disposed separately from the plurality of planar substrates and the plurality of weak points, wherein the conductor comprises an elongated metal strip having no stamped weak point openings therein and thereby avoiding thermomechanical fatigue strain in the conductor when subjected to a transient load current cycling event. The elongated metal strip also includes a coplanar connecting section attached to a respective one of the plurality of weak points and an obliquely extending section bent out of the plane of the coplanar connecting section. The plurality of weak points are longitudinally spaced apart from one another along the conductor, and the plurality of planar substrates are longitudinally spaced apart from one another along the conductor.

[0083] Optionally, one of the plurality of fusible weak points comprises an opening. The plurality of fusible weak points are printed on the planar substrate. Each of the plurality of weak points is attached to a side of one of the coplanar connecting sections that is coplanar with a valley formed by the coplanar connecting section and its adjacent obliquely extending section. The coplanar connecting section forms a recess sized to receive the weak point therein. The coplanar connecting section is attached to a corresponding weak point in the plurality of weak points by a first solder and a second solder, the first solder having a higher melting temperature than the second solder, the first solder being deposited over the corresponding weak point in the plurality of weak points, and the second solder being deposited over the first solder.

[0084] Another embodiment of a method for manufacturing a power fuse for protecting electrical loads subjected to transient load current cycling events in a DC power system is disclosed. The method includes forming a plurality of fusible weak points on a plurality of planar substrates. The method also includes providing a conductor separate from the plurality of planar substrates and the plurality of weak points, wherein the conductor comprises an elongated metal strip having no stamped weak point openings therein and thereby avoiding thermomechanical fatigue strains in the conductor when subjected to a transient load current cycling event. The elongated metal strip includes a coplanar connecting section and an inclined extension section that bends out of the plane of the coplanar connecting section. The method also includes attaching the coplanar connecting section of the conductor to corresponding weak points of the plurality of weak points such that the plurality of weak points are longitudinally spaced apart from one another along the conductor and the plurality of planar substrates are longitudinally spaced apart from one another along the conductor.

[0085] Optionally, attaching the coplanar connecting sections further comprises attaching one of the plurality of weak points to its corresponding one of the coplanar connecting sections on a side of the coplanar connecting sections that is opposite to a valley formed by the coplanar connecting sections and their adjacent oblique extension sections. Optionally, attaching the coplanar connecting sections further comprises attaching one of the plurality of weak points to its corresponding one of the coplanar connecting sections on a side of the coplanar connecting sections that is the same as the valley formed by the coplanar connecting sections and their adjacent oblique extension sections. The conductor further comprises a support bridge connecting the coplanar connecting sections, the oblique extension sections and the support bridge forming a receptacle sized to receive one of the plurality of planar substrates therein. Attaching the coplanar connecting sections further comprises aligning the coplanar connecting sections with the plurality of planar substrates using the support bridge and the oblique extension sections, and holding the planar substrate in place during reflow using the support bridge and the oblique extension sections. Attaching the coplanar connection section also includes removing the support bridge after the coplanar connection section of the conductor has been attached to the corresponding weak points in the plurality of weak points. Forming the plurality of fusible weak points also includes forming the plurality of fusible weak points on a single planar substrate and dividing the single planar substrate into a plurality of planar substrates such that each planar substrate includes a weak point. Forming the plurality of fusible weak points on the single planar substrate also includes applying a first solder to the plurality of weak points. Applying the first solder also includes screen printing the first solder to the plurality of weak points and reflowing the first solder on the plurality of weak points. Attaching the coplanar connection section also includes: dispensing a second solder on the coplanar connection section of the conductor, wherein the second solder has a melting temperature lower than the melting temperature of the first solder; placing the plurality of weak points together with the coplanar connection section such that the first solder and the second solder face each other; and reflowing the first solder and the second solder. Attaching the coplanar connection section also includes placing the plurality of weak points together with the coplanar connection section and applying a weight to at least one of the plurality of planar substrates and the coplanar connection section. One of the plurality of fusible weaknesses includes an opening. Forming the plurality of fusible weaknesses further comprises forming the plurality of fusible weaknesses on the plurality of planar substrates by printing the plurality of fusible weaknesses on the plurality of planar substrates. One of the coplanar connecting sections forms a recess sized to receive one of the plurality of weaknesses, and attaching the coplanar connecting section further comprises placing the weakness into the recess.

[0086] Another embodiment of a power fuse for protecting electrical loads subjected to transient load current cycling events in a DC power system is disclosed. The power fuse includes at least one fuse assembly, the at least one fuse assembly including one or more substrates, one or more fusible weak points, each printed on one of the one or more substrates, and a conductor. The conductor is disposed separately from the one or more substrates and the one or more weak points, wherein the conductor comprises an elongated metal strip having no printed weak point openings therein and thereby avoiding thermomechanical fatigue strain in the conductor when subjected to transient load current cycling events. The elongated metal strip also includes a coplanar connecting section attached to a corresponding one of the one or more weak points and an obliquely extending section that bends out of the plane of the coplanar connecting section. The one or more weak points are longitudinally spaced apart from one another along the conductor, and the one or more substrates are longitudinally spaced apart from one another along the conductor.

[0087] Optionally, one of the one or more substrates is formed as a rod having an increased thickness compared to a substrate formed as a sheet.

[0088] This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims and may include other examples that occur to those skilled in the art. If such other examples have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims, such other examples are intended to be within the scope of the claims.

Claims

1. A power fuse for protecting an electrical load subjected to a transient load current cycling event in a DC power system, the power fuse comprising: At least one melt assembly, the at least one melt assembly comprising: a plurality of planar substrates; a plurality of fusible weaknesses, each of the plurality of fusible weaknesses being formed on one of the plurality of planar substrates; and a conductor disposed separately from the plurality of planar substrates and the plurality of weak points, wherein the conductor comprises an elongated metal strip having no embossed weak point openings therein and thereby avoiding thermomechanical fatigue strains in the conductor when subjected to the transient load current cycling event, the elongated metal strip further comprising: coplanar connecting sections attached to respective ones of the plurality of weak points; and an obliquely extending section that curves out of the plane of the coplanar connecting section, The plurality of weak points are longitudinally spaced apart from one another along the conductor, and the plurality of planar substrates are longitudinally spaced apart from one another along the conductor.

2. The power fuse according to claim 1, wherein one of the plurality of fusible weak points comprises an opening; and / or The plurality of fusible weak points are printed on the planar substrate.

3. The power fuse of claim 1 , wherein each of the plurality of weak points is attached to a side of one of the coplanar connecting sections that is the same as a valley formed by the coplanar connecting section and its adjacent obliquely extending section. 4 . The power fuse of claim 3 , wherein the coplanar connecting sections form a recess sized to receive the weak point therein.

5. An electrical fuse according to claim 1, wherein the coplanar connecting section is attached to a corresponding weak point among the multiple weak points by a first solder and a second solder, the melting temperature of the first solder is higher than the melting temperature of the second solder, the first solder is deposited above the corresponding weak point among the multiple weak points, and the second solder is deposited above the first solder. 6 . The power fuse of claim 1 , wherein one of the plurality of substrates is formed into a rod having an increased thickness compared to a substrate formed into a sheet.

7. A method of manufacturing a power fuse for protecting an electrical load subjected to a transient load current cycling event in a DC power system, the method comprising: forming a plurality of fusible weak points on a plurality of planar substrates; providing a conductor separate from the plurality of planar substrates and the plurality of weak points, wherein the conductor comprises an elongated metal strip having no weak point openings stamped therein and thereby avoiding thermomechanical fatigue strains in the conductor when subjected to the transient load current cycling event, the elongated metal strip comprising a coplanar connecting section and an angled extending section bent out of the plane of the coplanar connecting section; as well as The coplanar connecting sections of the conductor are attached to respective ones of the plurality of weak points such that the plurality of weak points are longitudinally spaced apart from one another along the conductor and the plurality of planar substrates are longitudinally spaced apart from one another along the conductor.

8. The method according to claim 7, wherein attaching the coplanar connecting sections further comprises attaching one of the plurality of weak points to its corresponding one of the coplanar connecting sections on a side of the coplanar connecting section opposite a valley formed by the coplanar connecting section and its adjacent obliquely extending section; and / or wherein attaching the coplanar connecting sections further comprises attaching one of the plurality of weak points to its corresponding one of the coplanar connecting sections on a side of the coplanar connecting section that is the same as a valley formed by the coplanar connecting section and its adjacent obliquely extending section; and / or wherein attaching the coplanar connection sections further comprises: placing the plurality of weak points with the coplanar connecting sections; as well as A weight is applied to at least one of the plurality of planar substrates and the coplanar connecting sections.

9. The method of claim 7, wherein the conductor further comprises a support bridge connecting the coplanar connecting sections, the obliquely extending sections and the support bridge forming a receptacle sized to receive one of the plurality of planar substrates therein, attaching the coplanar connecting sections further comprising: aligning the coplanar connection sections with the plurality of planar substrates using the support bridges and the angled extension sections; holding the planar substrate in place during reflow using the support bridges and the angled extensions; as well as The support bridge is removed after the coplanar connecting sections of the conductors have been attached to respective ones of the plurality of weak points.

10. The method of claim 7, wherein forming a plurality of fusible weak points further comprises: forming the plurality of fusible weak points on a single planar substrate; as well as The single planar substrate is divided into the plurality of planar substrates such that each planar substrate includes a weak point.

11. The method of claim 10, wherein forming the plurality of meltable weak points on a single planar substrate further comprises applying a first solder to the plurality of weak points.

12. The method according to claim 11, Wherein applying the first solder further comprises: screen printing the first solder material onto the plurality of weak points; as well as causing the first solder to reflow on the plurality of weak points; and / or wherein attaching the coplanar connection sections further comprises: dispensing a second solder on the coplanar connection section of the conductor, wherein the second solder has a melting temperature lower than the melting temperature of the first solder; placing the plurality of weak points and the coplanar connection section together such that the first solder and the second solder face each other; and The first solder and the second solder are reflowed.

13. The method of claim 7, wherein one of the plurality of fusible weak points comprises an opening.

14. The method of claim 7, wherein one of the coplanar connecting sections forms a recess sized to receive one of the plurality of weak points, attaching the coplanar connecting sections further comprising: The weak point is provided in the recess.

15. The method of claim 7, wherein forming a plurality of fusible weaknesses further comprises forming the plurality of fusible weaknesses on the plurality of planar substrates by printing the plurality of fusible weaknesses on the plurality of planar substrates.

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