US2594315A - Current-limiting fuse - Google Patents

Current-limiting fuse Download PDF

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Publication number
US2594315A
US2594315A US192003A US19200350A US2594315A US 2594315 A US2594315 A US 2594315A US 192003 A US192003 A US 192003A US 19200350 A US19200350 A US 19200350A US 2594315 A US2594315 A US 2594315A
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Prior art keywords
casing
link
fuse
current
pair
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Frederick J Kozacka
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Chase Shawmut Co
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Chase Shawmut Co
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Priority to US192003A priority Critical patent/US2594315A/en
Priority to CH309310D priority patent/CH309310A/de
Priority to DEC4866A priority patent/DE906356C/de
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H85/00—Protective devices in which the current flows through a part of fusible material and this current is interrupted by displacement of the fusible material when this current becomes excessive
    • H01H85/02—Details
    • H01H85/04—Fuses, i.e. expendable parts of the protective device, e.g. cartridges
    • H01H85/041—Fuses, i.e. expendable parts of the protective device, e.g. cartridges characterised by the type
    • H01H85/044—General constructions or structure of low voltage fuses, i.e. below 1000 V, or of fuses where the applicable voltage is not specified
    • H01H85/045—General constructions or structure of low voltage fuses, i.e. below 1000 V, or of fuses where the applicable voltage is not specified cartridge type
    • H01H85/0458—General constructions or structure of low voltage fuses, i.e. below 1000 V, or of fuses where the applicable voltage is not specified cartridge type with ferrule type end contacts

Definitions

  • This invention relates to fuses and more particularly to fuses of the current-limiting type.
  • the term current-limiting fuse is generally ap plied to any fuse which limits the flow of current in a circuit to a substantially smaller value than the available short-circuit current of the circuit.
  • the highest current which a current-limiting fuse permits to pass is referred to as the letthrough current.
  • the current-limiting effect of most currentlimiting fuses is due to the interaction ofl the metal vapors resulting' from vaporization of the link of the fuse and an inert pulve'rulent filler by which the link is surrounded.
  • the link consists not necessarily but generally of silver because silver has a relatively high conductivity in its solid state, While its vapors have a relatively low conductivity unless their temperature is particularly high. In other words, at a given temperature slightly above the boiling point of silver the percentage of ionized silver is relatively low, resulting in a relatively small conductivity of silver vapors at this temperature range.
  • a fuse link made of silver is vaporized in an inert pulverulent filler such as quartz sand, which practically does not evolve any gases under the heat of the arc.
  • the silver vapors resulting from vaporization of the link are rapidly reduced to a low temperature Where they Will not support a flow of current.
  • the duration of arcing through the labyrinth path formed by the inter'- stices between the particles of granules of the filler may be, or actually is, extremely shrt, a portion of the particles melt ⁇ or fuse and form a fulgurite or semi-conductor.
  • Ihe semi-*cone ductor or fulgurite resulting from fusion and sin- ⁇ tering of quartz particles is in the nature of a glass body, and as it cools down to ambient temperature it loses its conductivityand4 turns into an insulator.
  • AMetal vapors which diffuse in the pulverulent ller beyond the immediate arcing zone condense on the large surfaces ofthe quartz particles and form a silver-quartz conglomerate which has an extremely high resistance and which, for any practical purpose, may be consid ered as an insulator.
  • Another object of the invention is to provide a current-limiting fuse which is particularly suitable for the voltage range of 1000 volts and higher voltages and which is more compact than prior-art current-limiting fuses for that voltage range.
  • fuse links of which substantially the ventire length consists of a variable cross-sectional area section having a relativly large number of serially related portions of relatively small crosssectional area and intermediate portions of relatively large cross-sectional area are being used in high voltage current-limiting fuses to produce series arcs and for other reasons.
  • fuse links having a geometrical configuration of this type to fuses having a voltage rating in the neighborhood of 1000 volts makes it possible to distribute the thermal duty of the arc quenching filler relatively evenly over the entire filler body which is a factor tending to permit a reduction of the overall size of the fuse and more particularly of the internal space of the fuse casing.
  • a current-limiting fuse having a variable cross-sectional area section as above described is subjected to fault currents in the nature of short-circuit currents, all of the portions of relatively small cross-sectional area fuse and vaporize almost simultaneously, resulting in the formation of arclets in series. Frequently only a part of each intermediate relatively large cross-section portion of the link is completely vaporized during the interrupting process.
  • the fulgurite or semi-conductor formed under such conditions consists actually of a string of small spaced fulgurites or semi-conductors and intermediate portions of more or less solid metal.
  • the interrupting process in a current-limiting fuse having a variable crosssectional area section is quite diiferent if the fuse is subjected to relatively small protracted fault currents. In this case there are appreciable intervals of time between'initiation of arcing at various relatively small cross-sectional area portions. Generally the arc gap first formed is being progressively enlarged by vaporization of the link until the gap is of suicient length to effect final interruption of the circuit. Because of these facts the fulgurite or semi-conductor formed in current-limiting fuses of the silver-link quartzo sand-filler type which are provided with links having a variable cross-sectional area section, as above described, is generally continuous when such fuses are subjected to small protracted overload currents.
  • venting means permitting the escape of gaseous products out of the link-receiving casing into an enclosed space Where the hot gaseous products are trapped to prevent them from causing any harm, and in particular to prevent them from causing any electric breakdown. Except for appropriately positioned venting means the link-receiving casing ought to be completely, or at least substantially, gas tight.
  • the mechanical strength of the link-receiving casing is less than required to withstand the total pressure resulting from the partial vapor pressure due to the vaporization of a preponderant portion of the length of the above referred-to variable crosssectional area section of the fuse link, and the partial pressure due to the follow-current through the fulgurite formed upon fusion of a portion of the arc-quenching filler.
  • the partial vapor pressure can be determined from a measurement of the internal volume of the link-reH 'ceiving casing and the amount or" link metal Vaporized during the arcing period.
  • the partial pressure due to the flow or" a follow-current through the fulgurite may be determined by an oscillo'graphic investigation or" the post interruption period of the fuse. If the link-receiving casing' were designed to withstand the high pressure which develops in the fuse, this would require 'such thickness of the Walls of the link-receiving casing as to ofiset vthe reduction of space requirements due to the decrease of the internal linkereceiving space within the fuse casing. Provision of a judiciously selected venting means enables the use of link-receiving casings of more limited mechanical strength. It is, however, desirable to use tubular materials of considerable mechanical strength for manufacturing the link-'receiving casing such as laminated materials Y including layers of spun and woven glass fibers impregnated with a heat resisting plastic substance.
  • Fig'. l is a substantially central longitudinal section through a fuse constructed in accordance with my invention with certain of its parts shown in elevation;
  • Fig. 2 is a transverse cross-sectional view of the fuse shown in Fig. 1 taken along the line Il-I thereof;
  • Fig. 3 is a substantially central longitudinal section through a modied form of fuse constructed in accordance with my invention with certain parts thereof shown in elevation;
  • Fig. 4 isa transverse cross-sectional View of the fuse shown in Fig. 2 taken along line IIL-III thereof;
  • Fig. 5' is a section similar to those in Figs. l and 3 showing another fuse structure embodying my invention.
  • link 2 might be of a metal other than silver such ass for instance, zinc, but for the reasons stated above silver is preferable.
  • Link 2 is provided with a plurality of circular equi-distant perforations or holes 2a which determine the points where fusion of the link is initiated, at least when the fault current and its rate of rise are high.
  • Link 2 is inintimate contact substantially along its entire length with the quartz filler 3.
  • the perforations or holes 2a form portions of reduced cross-sectional area of which each comprises two parallel current paths, one on either side of each hole oi: perforation.
  • each pair of arcs or arcletsin parallel extinguishes soon thereafter.
  • the space which was originally occufile by the fuse link and thereafter occupied by the arc is finally occupied by aglass-like body resulting from the fusion of the quartz filler immediately adjacent the arcing zone.
  • that body may consist of a plurality of spaced fulgurite elements with residual metal particles in the gaps therebetween. As long as that body is relatively hot it is a fairly good conductor of electricity. It turns into an insulator of high dielectric strength and f ohmic resistance as it cools down to ambient temperature.
  • the full line potential prevails across the glass-like semi-conductor resulting from the fusion of the quartz filler.
  • the full line potential tends to cause continued Iiow of current through the semi-conductor and though the rate of current flow is generally very small and may appear to be insignificant, yet the resulting 12T losses may be sufliciently large to critically delay the cooling of the semi-conductor. In such instances a post interruption failure is likely to occur.
  • interruption of low currents differs in certain respects from interruption of high currents.
  • interruption of low currents differs in certain respects from interruption of high currents.
  • the casing I of the fuse is provided with a pair of external spaced radial flanges Ia and Ib which support an outer casing or tubular member 3 in coaxial relation with casing I.
  • Flanges Ia, Ib and the outer casing 4 define jointly a substantially closed toroidal chamber 5.
  • Both casings I and 4 consist preferably of a suitable laminated material, e. g., spun and woven glass fibers which are impregnated with a suitable plastic.
  • Casing I is provided with a plurality of radial bores Ic which are angularly related and arranged in a common transverse plane, as can best be seen in Fig. 1.
  • the bores Ic are situated about midway between the axially outer ends of casing I and fuse link 2 and they interconnect the center region of casing I with the chamber 5. Because of this particular configuration there is a tendency for the gases formed ⁇ by vaporization of the fuse link 2 and Iby heating the air in the interstioes between the quartz granules to produce a pair of opposite gas flows enveloping and cooling the fulgurite or semiconductor formed upon fusion of the link 2 and of the adjacent mass of quartz filler 3. These two opposite gas flows have been clearly indicated by arrows in Fig. l. Both gas flows meet in the center region of the fuse, turn about degrees and escape through the passages Ic into the chamber 5.
  • the openings or passages Ic are normally obstructed by vadhesive cellulosic tape 6. Upon blowing of the fuse under overload conditions the tape israpidly deand projects beyond the ends thereof.
  • a pair of caps la, Eb is provided on the ends of casing or outer shell 4.
  • Another pair of caps 8a, 8b is provided on the ends of the casing l, which casing is longer than the casing or outer shell i
  • the ends of casing l are provided with an additional or outer pair of caps 9a, gb.
  • Each end of link 2 is secured, as by Welding or soldering, to one of caps 8a, 8b and each of caps 8a, 8b has a circular indentation ma, ib engaging one of a pair of circular grooves I ia, i lb in casing i.
  • Each of the pair of caps 9a, 9b covers one of the pair of caps 8a, 8b and is in metallic contact therewith.
  • Each of the pairs of caps “a, “ib has on the lateral surface thereof a circular indentation ld, 52h engaging one of a pair of circular grooves i3d, 13b in casing or outer shell t.
  • the caps la, 'ib are each provided with a central aperture Ma, Ilib on their top portion lia and i512, respectively.
  • Caps 9a. and 9b project through the apertures Ida and
  • caps 90;, 0b enter toroidal spaces dened by casing l and shell li.
  • the above described triple cap arrangement provides for a great amount of mechanical strength required in spite of the complete absence of gas evolving substances mainly because of the relative large ratio between the amount of metal vaporized by the heat of the arc to the internal volume of the link-receiving casing I.
  • the amount of metal vaporized by the heat of the arc is proportional to the arc energy dissipated during the interrupting process. ft is possible to decrease progressively the ratio of arc energy dissipated during the interrupting process to internal volume of the fuse-link and quartz-sand- .iiller-receiving casing. The smaller that ratio,
  • Figs. 1 and 2 of the drawing represent in about natural size a current-limiting fuse capable of -controlling D.C. circuits having an available short-circuit current above 80,000 amperes at a rated voltage of 1000 volts.
  • the let-through current of the fuse is in the order of 3,500 amperes and its current rating 30 amperes.
  • the fuse When interrupting short-circuits the clearing time is in the order of 1/@00 seconds.
  • the fuse is capable of interrupting both short-circuit currents and relatively small overload currents of inadmissible duration and is not subject to post interruption failures even at the critical minimum fusing current range.
  • tion of the surrounding quartz filler is sufliciently intense.
  • the gap length formed will depend upon the amount or arc energy which is being dissipated during the interrupting Iprocess and the arc gap is being bridged by a fulgurite or semiconductor which is in the nature of glass since it is produced by the fusion of quartz sand.
  • the interrupting process is actually more complex on account of chemical reactions which may take place in addition to the more obvious thermal processes, and I do not v/ish to limit my invention by referring merely to the thermal aspects of the interrupting process.
  • the effectiveness of my invention may be fully explained by reference to thermal aspects only.
  • a silver link is provided with an alloy-forming element which reduces the fusing temperature of the link at the point where it is located, then initial gap formation at low current interruptions is generally limited to the neighborhood of the fusing-temperature-reducting element.
  • a fuse having an alloy-forming fusing-pointreducing element it may be sufficient to produce a single gas ow for cooling the semi-conductor resulting from the fusion of quartz sand rather than a pair of semi-conductor cooling gas cur-
  • the double flow feature may, however, be retained where it is desired or necessary to establish more eifective cooling conditions, and in that particular instance the fuse link ought to be provided with two alloy-forming elements, one adjacent each end of the link.
  • Figs. 3 and 4 show an embodiment of a preferred structure which involves one single alloy-forming element.
  • the fuse link 2 shown in Fig. 3 has a plurality of portions of reduced cross-sectional area and a plurality of portions of relatively larger crosssectional area intermediate said reduced crosssectional area portions.
  • Each reduced crosssectional area portion has a hole 20LV laterally bounded by a pair of metallic current paths in parallel.
  • the link 2 is provided with an insert I'i in one of said holes 2a remote from the center of the link.
  • the insert l' may be in the general shape of a rivet and it consists of a metal having a lower fusing point than the metal of which the fuse link 2 is made and adapted to form an alloy with the metal of which the fuse link is made having a lower fusing point than the metal of which the fuse link is made.
  • the fuse link is made ci silver the insert I'I may consist of tin.
  • An inert semi-conductor-forming pulverulent filler 3a such as quartz sand, is arranged in intimate contact with the portions of the link remote from insert I l, and a pulverulent filler 3b evolving gaseous products under the heat of the arc as, for instance, chemically pure chalk, is arranged in intimate contact with the portion of the link 2 adjacent the lower fusing point insert II.
  • the quartz filler 3a and the chalk iiller 3b are preferably separated by a disc Ii! equal in diameter to the internal diameter of casing I.
  • the .fuse shown in Figs. 3 and 4 operates in the same wayas the fuse shown in Figs. 1 and 2 inasmuch as interruption of currents of large magnitude is concerned. Its operation is different from the operation of the fuse shown in Figs. 1 and 2 inasmuch as the interruption of relatively small protracted overloads is concerned. On the occurrence of such overloads fusion and arcing are initiated at the point where the insert I 'I is located. The vapors resulting from vaporization of the alloy formed by the silver of link 2 and the metal of element I'I are highly ionized.
  • the average grain size of the quartz filler and the size of the passage means or bores I c to achieve interruption of small protracted overloads Without signs of post interruption distress.
  • the interstices between the filler particles and the vent openings Ic of the casing I must be of suincient size to permit development of sufficiently rapid flow conditions.
  • the flow of hot gases through the interstices of the quartz ller is obviously highly turbulent which tends to increase the rate of deionization of the arc products but tends also to increase the flow resistance.
  • the grain size of the quartz filler should be relatively coarse as, for instance, /40 mesh size.
  • nner grain size of the filler may have its advantages, but it is adverse to eiective interruption of small currents and more particularly to formation of an effective flow of gas in a direction longitudinally of the fulgurite.
  • the grain size of the nller should be coarser than 60 mesh and this is particularly important if the ller contains some impurities.
  • the flow resistance through the passage means or bores I c must be kept sufficiently low by judicious selection of their cross-sectional area.
  • each of the bores Ic should by far exceed the average grain size, and this requires the provision of a means, such as the adhesive tape seal G, which normally prevents the leakage of filler out of the casing into the deionizing chamber 5, but is easily destroyed by heat and pressure to permit the outflow of gaseous products of arcing.
  • the adhesive tape seal remains generally intact at the interruption of large currents, but is destroyed at the interruption of small currents.
  • the strength of the seal E is deliberately so selected that the seal remains unimpaired by the relatively small pressures resulting from the interruption of currents of short-circuit current proportions.
  • the fuse structure shown in Figs. 3 and 4 is provided with three venting bores or passages Ic which ⁇ are angularly related, or displaced, degrees, and have a diameter of .04 inch.
  • the number and diameter of the venting passages Ic may vary but must always lie within the limits required for producing an eiective scavenging flow from the point of gas generation in a direction substantially longitudinally of the link 2 toward the center of the fuse.
  • the con.- guration of the venting passages ought to be circular in order to produce a gas ilow which envelops the entire substantially cylindrical surface of the fulgurite.
  • Fig. 5 shows a fuse which has the triple cap, dual casing feature without having any means for producing an internal gas ow in a direction longitudinally of the fuse and without having any gas receiving and gas cooling chamber arranged between the outer and the inner fuse casing.
  • Like reference signs are applied in Fig. 5 and in Figs. 1 to 4 to indicate similar parts and, therefore, the structure of Fig. 5 will be readily understood without a separate description thereof.
  • the described flow of gases in the directions of the arrows may involve some pulsation, with some flow of gases in the opposite directions.
  • a current-limiting fuse comprising a first tubular casing, a second tubular casing arranged in spaced coaxial relation in said rst casing, means for closing the toroidal spaced formed between said rst casing and said second casing at the axial ends thereof, a fuse link arranged in substantially coaxial relation in said second casing and extending straight :between the ends thereof, a non-gas evolving granular fulguriteforming ller in said second casing in immediate contact with said link, passage means arranged substantially at the center of said second casing and the center of said link for the passage of gases from said second casing into said first casing, the cross-sectional area of said passage means exceeding the average grain size ofY said ller, and pressure responsive sealing means for controlling said passage means, said passage means being the only way of escape of gaseous products from said second casing.
  • a current-limiting fuse comprising a tubular casing, a fuse link arranged in substantially coaxial relation with regard to said casing and extending straight Ibetween the ends thereof, the preponderance of the length of said link consisting of a variable cross-sectional area section having a relatively large number of serially related portions of relatively small cross-sectional area and intermediate portions of relatively large cross-sectional area, an inert arc-quenching nller of the fulgurite-forming type in intimate contact with said link, and means tending to produce a :pair of opposite gas flows enveloping the fulgurite formed upon vaporization of a substantial portion of said link and fusion ci a substantial portion of said ller, said means tending to produce said pairs of gas ilows including a plurality oi angularly related passage means arranged in said casing substantially adjacent the center of said vvariable cross-sectional area section of said link, and means defining an outwardly closed chamber in communication with said passage means, said chamber being
  • a current-limiting fuse comprising a tubular casing, a fuse link arranged in substantially coaxial relation With regard to said casing and extending straight between the ends thereof, the preponderance of the length of said link consisting of a variable cross-sectional area section having a relatively large number of serially related portions of relatively small cross-sectional area ⁇ and intermediate lportions of relatively large cross-sectional area, an inert arc-extinguishing filler of the fulgurite-forming type in intimate contact with said link and means tending to produce a pair of opposite gas ows in a direction substantially longitudinally of the fulgurite formed upon vaporization of a portion of said link and fusion of a portion of said filler, said means Vtending to produce said pair of gas iiows including a plurality of angularly related passage means vprovided in said casing substantially adjacent the center of said variable cross-sectional area section of said link,- and means dening an outwardly closed chamber in communication with said passage means, said chamber being
  • a current-limiting fuse comprising a first relatively short and relatively wide tu-bular casing, a second relatively long and relatively narrow tubular casing arranged in spaced coaxial relation in said rst casing and extending beyond both ends thereof, said second casing having a pair of spaced external radial anges for closing said first casing, a fuse link arranged in substantially coaxial relation in said second casing and extending straight between the ends thereof, an inert granular fulgurite-forming nller in said second casing in intimate contact with said link, passage means arranged substantially at the center of said second casing and the center oi said link for the passage of gaseous products vfrom said second casing into said first casing, the cross-sectional area of said passage means exceeding the average grain size of said filler, and pressure responsive sealing means for normally closing said ⁇ passage means, said passage means being the only way of escape of gaseous products from said second casing.
  • a current-limiting fuse comprising a first tubular casing, a second tubular casing arranged in spaced coaxial relation in said rst casing, means for axially closing said first casing, separate means for axially closing said second casing, a fuse link arranged in substantially coaxial relation with regard to said second casing and extending straight between the closed ends thereof, substantially the entire length of said link Consisting of a variable cross-sectional area section having a relatively large number of serially related equi-distant portions of relatively small cross-sectional area and intermediate portions ci relativelyajige cross-sectional area, and inert fulgurite-forming arc extinguishing ller in said second casing in immediate contact with said link, the dimensions of said link and the arc extinguishing capacity of said filler being so re lated as to result in vaporization of a preponderant portion o' the length of said variable cross-sectional area section of said link on the occurrence of relatively small protracted fault currents, the
  • a current-limiting fuse comprising a rst relatively short and relatively wide casing, a second relatively long and relatively narrow casing arranged in spaced coaxial relation in said rst casing and projecting beyond both ends thereof, said second casing having a pair of spaced external flanges for closing said first casing, a rst pair of caps one on each end of said rst casing, a second pair of caps one on each end of said second casing, each of said rst pair of caps having a central aperture through which one of said second pair of caps projects and each of said second pair of caps' having a shoulder portion in engagement with one of said iirst pair of caps, a fuse link arranged in substantially coaxial relation in said second casing and extending straight between said second pair of caps, an inert fulgurite-forming ller in said second casing in intimate contact with said link, passage means arranged substantially at the center of said second casing and substantially adjacent the center of said link for permitting the escape of gaseous products from
  • a current-limiting fuse comprising a iirst tubular casing, a second tubular casing arranged in spaced relation in said nrst casing, means arranged substantially at the center of said seoond casing for venting said second casing into the spaced formed between said rst casing and said second casing, a fuse link arranged in said second casing and comprising a low melting point means for initiating circuit interruption at relatively small protracted overloads, said low melting point means being arranged adjacent an axially outer end of said link, a pulverulent inert semi-conductor-forming-ller in said second caing in intimate contact with a substantial portion of said link remote from said low melting point means, and a pulverulent filler evolving gas under the heat of the arc arranged in intimate contact with the portion of said link immediately adjacent said low melting point means.
  • a current-limiting fuse comprising a first tubular casing, a second tubular casing arranged in coaxial spaced relation in said first casing, said second casing having a pair of radial flanges jointly defining with saidiirs.l casing a substantially closed deionizing chamber', passage means arranged remote from the ends of said second casing permitting the escape of gaseous products from said second casing into said deionizing chamber, a fuse link arranged in said second casing, said link having a plurality of portions of reduced cross-section and a plurality of portions l of relatively larger cross-section intermediate said reduced cross-section portions, each said reduced cross-section portion having a hole laterally bounded by a pair of current paths in parallel, an insert in one of said holes remote from the center of said link, said insert consisting of a metal having a lower fusing point than the metal of which said link is made and adapted to form alloy with the metal of which said link is having a lower fusing point than the metal of which said insert
  • a fuse comprising a natrelatively short and relatively wide casing, a second relatively long and relatively narrow easing arranged in spaced coaxial relation in sad first casing and projecting beyond both ends thereof, external radial axially spaced iiange means on said second casing engaging the surface of said first casing, passage means in said second casing for permitting the escape or gaseous products from said second casing into said first casing, a fuse link arranged in said second casing, a pulverulent arc-quenching iiller in said second casing in immediate contact with said link.
  • each of said rst pair of caps having a central aperture for the passage of one of said second pair of caps and each of said second pair of caps having a shoulder portion in abutting relation with one of first pair of caps.
  • a fuse comprising a first relatively short and relatively wide casing, a second relatively long and relatively narrow casing arranged in spaced coaxial relation in said rst casing and projecting beyond both ends thereof, external radialaxially spaced flange means on said second casing substantially equal in diameter to internal diameter of said rst casing, passage means in said second casing for permitting the escape of gaseous products from said second casing into said rst casing, a fuse link arranged in substantially coaxial relation in said second casing and extending straight between the end portions thereof, a pulverulent arc-quenching ller in said second casing in immediate contact with said link, a rst pair of caps one on each end of said nrst casing, a second pair of caps one on each end of said second casingy a third pair of caps one on each end of said second casing.
  • each end of said link being secured to one of said third pair of caps and each of said third pair of caps havingT a circular lateral indentation engaging one of a pair of circular grooves in said second casing-each of said second pair of caps covering and surrounding one of said third pair of caps and being in metallic contact therewith, and each of said iirst pair of caps having on the lateralsurface thereof a circular indentation engaging one of a pair of circular grooves in said nrst casing and on the top portion thereof la circular aperture for the passage of one of said second pair of caps, said top portion of each of said first pair of caps also engaging a shoulder pcrtionon each of said second pair of caps.
  • a current-limiting fuse comprising casing means dening a radially outer substantially closed chamber and a. radially inner substantially closed chamber, a fuse link arranged Within and in substantially coaxial relation with regard to said radially inner chamber and extending straight between the ends thereof, the preponderance of the length of said link consisting of a variable cross-sectional area section having a relatively large number of serially related portions of relatively small cross-sectional area and intermediate portions of relatively large crosssectional area, an inert arc-quenching ller of the fulguriteforining type in intimate contact with the major portion of said variable crosssectional area section, said variable cross-sectional area section being adapted to vaporize in said filler on the occurrence of small protracted overloads along a substantial portion thereof, a plurality of angularly related passages arranged in a common transverse plane for interconnecting said radially inner chamber and said radially outer chamber, means for initiating fusion of said link at a temperature below the fusing point of the
  • a current-limiting fuse comprising a first relatively short and relatively wide tubular casing, a second relativelylong and relatively narrow tubular casing arranged in spaced coaxial relation in said iirst casing and projecting beyond both ends thereof, external radial axially spaced iianges on and forming an integral part of said second casing, said iianges being substantially equal in diameter to the interna-l diameter oi?
  • said passage means including a plurality of angularly related passages arranged substantially in a common transverse plane, a fuse link arranged within and in substantially coaxial relation withregard to said second casing and extending straight between the ends thereof, the preponderance of the length of said link consist ing of a variable cross-sectional area section having a relatively large number of serially related portions of relatively small cross-sectional area and intermediate portions of relatively large cross-sectional area, each said relatively large cross-sectional area portions having a hole laterally bounded by a pair of current paths in parallel, a pulverulent quartz ller in intimate contact with the major portion of said variable cross-sectional area section, means for initiating fusion of said link at a temperature below the fusingpoint of the metal of which said link is made, said fusion initiating means being arranged in axially
  • a current-limiting fuse comprising a first relatively short and relatively wide casing, a second relatively long and relatively narrow casing arranged in coaxial relation with respect to and within said rst casing, said second casing comprising an axially inner sectionequal in diameter to the internal diameter of said iirst casing and axially outer sections of smaller diameter pro- ⁇ iecting beyond both ends of said rst casing, a fuse link arranged in substantially coaxial relation in said second casing and extending straight between the ends thereof, a pulverulent filler in said second casing in immediate contact with said link, a nrst pair of caps one on each end of said iirst casing, a second pair ofV caps one on each end of said second casing, a third pair of caps one on each end of said second casing, each end of said link being secured to one of said third pair of caps and each of said third pair of caps having substantially the same configuration as said axially outer sections of said second casing, each of said second
  • 'A current-limiting fuse comprising a rst relatively short and relatively wide casing, a second relatively long and relatively narrow casing arranged in coaxial relation with respect to' and within said iirst casing, said second casing comprising an axially inner section equal in diameter to the internal diameter of said first casing and axially outer sections of smaller diameter projecting beyond both ends of said iirst casing, a fuse link arranged in substantially coaxial relation to and within said second casing and extending straight between the ends thereof, the preponderance of the length of said link consisting of a variable cross-sectional area sectionthaving a relatively large number of serially related portions of relatively small cross-sectional area and intermediate portions of relatively large cross-sectional area, a pulverulent quartz-filler in intimate contact with the major portion of said variable cross-sectional area section, a rst pair of caps one on each end of said iirst casing, a second pair of caps one on each end of said second casing,
  • a current-limiting fuse for the 1090 volt rating range comprising a straight fuse link of sheet metal, the preponderance of the length of said link consisting of a variable cross-sectional area section having a relatively large number of serially related portions of relatively small crosssectional area and intermediate portions oi relatively large cross-sectional area, a cylindrical casing of laminated material wherein said link is mounted in coaxial relation, the internal diameter of said casing being less than three times the width of said link, said link being surrounded by a granular quartz-filler the average grain size of which is coarser than 60 mesh, and means tending to produce at least one flow of gas in a direction longitudinally of the fulgurite formed upon vaporization or" said link due to a fault current oi relatively small magnitude and inadmissible duration, said means including passage means in said casing, vsealing means for controlling said passage means, said sealing means being adapted to be unaffected by the relatively small pressures generated in said casing during the interruption of currents of short-circuit

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US192003A 1950-10-25 1950-10-25 Current-limiting fuse Expired - Lifetime US2594315A (en)

Priority Applications (3)

Application Number Priority Date Filing Date Title
US192003A US2594315A (en) 1950-10-25 1950-10-25 Current-limiting fuse
CH309310D CH309310A (de) 1950-10-25 1951-10-16 Elektrischer Schmelzsicherungseinsatz.
DEC4866A DE906356C (de) 1950-10-25 1951-10-25 Elektrische Sicherung, namentlich strombegrenzende Niederspannungs-Hochleistungssicherung

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US192003A US2594315A (en) 1950-10-25 1950-10-25 Current-limiting fuse

Publications (1)

Publication Number Publication Date
US2594315A true US2594315A (en) 1952-04-29

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ID=22707834

Family Applications (1)

Application Number Title Priority Date Filing Date
US192003A Expired - Lifetime US2594315A (en) 1950-10-25 1950-10-25 Current-limiting fuse

Country Status (3)

Country Link
US (1) US2594315A (de)
CH (1) CH309310A (de)
DE (1) DE906356C (de)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2647970A (en) * 1951-10-23 1953-08-04 Chase Shawmut Co Current-limiting fusible protective device
US2843702A (en) * 1952-10-22 1958-07-15 Ite Circuit Breaker Ltd Protective device with current limiting means
US3007019A (en) * 1960-02-02 1961-10-31 Chase Shawmut Co Cable protection
US3401246A (en) * 1967-08-24 1968-09-10 Westinghouse Electric Corp High voltage circuit interrupter
US20060119464A1 (en) * 2004-12-06 2006-06-08 Muench Frank J Jr Current limiting fuse

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
None *

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2647970A (en) * 1951-10-23 1953-08-04 Chase Shawmut Co Current-limiting fusible protective device
US2843702A (en) * 1952-10-22 1958-07-15 Ite Circuit Breaker Ltd Protective device with current limiting means
US3007019A (en) * 1960-02-02 1961-10-31 Chase Shawmut Co Cable protection
US3401246A (en) * 1967-08-24 1968-09-10 Westinghouse Electric Corp High voltage circuit interrupter
US20060119464A1 (en) * 2004-12-06 2006-06-08 Muench Frank J Jr Current limiting fuse
US7477129B2 (en) * 2004-12-06 2009-01-13 Cooper Technologies Company Current limiting fuse
US7834738B2 (en) 2004-12-06 2010-11-16 Cooper Technologies Company Current limiting fuse
US8035473B2 (en) 2004-12-06 2011-10-11 Cooper Technologies Company Current limiting fuse

Also Published As

Publication number Publication date
CH309310A (de) 1955-08-31
DE906356C (de) 1954-03-11

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