US2371969A - Impulse-protected fuse - Google Patents

Description

March 20, 1945. D, D, MMCARTHY Em 2,371,969

IMPULSE-PROTECTED FUSE Filed April 24, 1941 v v h 6 Pl P. O s

M m 2 w m M eD i VIP G n W I m Fig.1.

Patented Mar. 20, 1945 IMPULSE-PROTECTED FUSE.

Donnell D. MacCarthy and Theodore Brownlee, Pittsfield, Mass., assignors to General Electric Company, a corporation of New York Application April 24, 1941, Serial No. 390,076 21 Claims. (Cl. 200-115) The present invention relates to fuse devices and more particularly to the type having provision for preventing their being blown by impulse or lightning discharge currents.

In various types of installations fuse devices are subjected to impulse currents, such as lightning discharges, which may cause the blowing of the fuse element and hence an interruption in service until the fuse devicemay be reconditioned. It will be obvious to one skilled in the art that a fuse provided for protection against excess power current cannot be expected to open the circuit rapidly enough to reduce the magnitude or duration of short duration impulse voltages applied to the connected apparatus. Such apparatus is usually protected against impulse failure by lightning arresters or protective gaps that limit the impulse voltage to a safe value below the voltage that will damage the apparatus. However, the fuse device may be so located in the circuit that it'will be required to carry impulse currents of considerable magnitude such as may be discharged through the protective devices or transmitted through fuses connected in series with sections of distribution or transmission lines.v It is desirable, therefore, to provide a fuse device for use in such installations whereby transient discharges will be bypassed around the fusible element leaving it intact for operation in its intend,- ed function, that is, upon the occurrence ofan excess current condition at normal power frequency.

A fuse device of the type herein considered may also be used for protecting lightning arr-esters which are susceptible to injury by subjection to a continuous excess current condition at normal power frequency such as an arcing ground. A fuse device of the bypass type could be inserted in series with the lightning arrester and which device would have no effect in the circuit as regards lightning or other transient phenomena which the lightning arrester is designed normally to handle. Upon the occurrence of an excess current condition at normal power frequency the fuse device will be blown to open the circuit through the lightning arrester and thus limit injury thereto.

It is, therefore, an object of the present invention to provide a new and improved impulse protected fuse device which is simple and relatively inexpensive in design and which is reliable in operation. i

It is a further object of the present invention to provide a new and improved electric circuit interrupter including afusible elementand havting of the gap I 6 that ing means for preventing the rupture of the fusi ble element by transient discharge currents.

Another object of the present invention is to providea new and improved impulse protected fuse device which is compact and may be readily inserted in a conventional fuse box.

It is a further object of the present invention to provide a new and improved fuse link arrangement for use in an electric cutout device of the impulse protected type and which fuse link is relatively simple in design and effective and reliable in operation for interrupting an excess current at normal power frequency and for bypassing transient discharge currents around the fusiblesection without affecting the same.

For a further consideration of what we believe to be novel and our invention, attention is directed to the following description and the claims appended thereto taken in connection with the accompanying drawing.

In-the drawing Fig. l is a sketch illustrating schematically the essential elements of one form of lightning-proof fuse arrangement; Fig. 2 is a longitudinal view partly in section of an impulse protected fuse device according to one form of the invention; Figs. 3 and 4 are other views partly in section of impulse protected fuse devices constructed in accordance with further modifications of the present invention; and Fig, 5 i a longitudinal sectional view of the fuse link of Fig. 4.

Referring to Fig. l, the fuse devices of the pres ent invention all relate to the type having a pair of terminals H and I2 adapted to be connected in a series circuit and having an impedance element 13, a fusible conductor section I4 and a flexible connection including a spring 15 for drawing the ends of the fusible section apart following arupture thereof by an excess current condition. For bypassing transient current discharges around the fusble conductor section It, electrodes forming a gap l 6 are connected in a shunt circuit extending around the impedance element l3 and the fusible section M. The impedance of the element i3 is so correlated with respect to the setthe impedance at normal power frequency will be insufiicient for causing a gap breakdown if the fusible element is intact. Under an impulse voltage, the element l3 will present a relatively high impedance to the current flow. The voltage drop occurring across the element I3 will be above the breakdown voltage for the gap I6 so that the transient current will be diverted through the bypass with little or no current flow taking place 55 through the fusible conductor section M.

the voltage drop across In the modification illustrated in Fig. 2 the fuse device comprises a fuse carrier including an insulating tube I! having spaced sleeves or line terminals I8 and i9 arranged thereupon which are so shaped and spaced as to be cooperatively received by the spring clips of the usual expulsion fuse cutout box. Arranged within the insulating tube I1 is a fuse link indicated generally at comprising a button head 2|, a fusible section 22, a flexible cable 23 surrounded by a retracting spring 24, and an enclosing insulating tube 25 of relatively small diameter. The lower end or Dietail of the flexible cable 23 indicated at 26 is se: cured by means of a suitable clamping nut 21 which is threaded onto an extension of terminal ill. The button head 2| of the fuse link is secured by the upper terminal cap 28 to the upper end of the insulating tube l1.

Arranged around the upper end of the insulating tube I1 is an impedance element 29, in this case an inductance comprising a plurality of series conductor turnsarranged upon an insulating spool 3|, the inner'diameter of which is very slightly larger than the outer diameter of the insulating tube I! so that it will fit snugly thereupon. One end of the inductance coil is conductively connected to the upper cap 28 while the other end of the coil is connected to the line terminal l8.

A gap bypass circuit is provided between the line terminal 18 and the flexible cable of the fuse link. Thev insulating tube 25 of the fuse link is divided into two sections and spaced apart in the region beneath the line terminal IS, the two adjacent ends being joined together by a metal sleeve 33. The central portion of the metal sleeve 33 has an inner diameter substantially but not quite the same as the inner diameter of the tube sections, while the opposite .ends of the sleeve 33 are enlarged for coo eratively receiving the ends of the 'tube sections which fit snugly against shoulders provided in the sleeve. The bore of the insulating tube section and the intermediate sleeve is substantially smooth so that there will be no projections to ininterfere with the expulsion of the fusible portions upon the melting thereof. Clamped over the junction between the fusible section 22 and the flexible cable 23' is a' metal sleeve 34 which isarranged within the central portion of the outer sleeve 33. The outer diameter of the sleeve 34 is somewhat smaller than the inner diameter of the outer sleeve 33 so as to provide a discharge gap therebetween for transient currents. Electrical connection is made between the line terminal l8 and the outer sleeve 33 of the fuse link by mea'nsof a thumb screw 35 threaded therein and extending through an aligned opening in the insulating tube H, the inner end of the screw 35 engaging with the outer surface of the sleeve Under normal conditions, current will flow between the terminals IB and [9 through the inductance winding 29 and the fuse link conductor portions 22- and' 2 3. At normal power frequency the impedance drop across the inductance 29 will be relatively low and considerably less than the breakdown voltage for the gap between electrode members 33 and 34 for any value of current within theinterrupting rating of the device. While the inductance and the spacing of the gap may be adjusted as desired, it has been found that'with an impedance coil having an inductance of 66 microhenries and agap space ing of 3O mils; the gap'would spark over at itto heat the fusible element to melting temperature. By use of larger inductances or shunting gaps of lower impulse spark potential the minimum rate of current rise which will spark the g gap can be reduced. Test experience with impulse protected fuses having design constants as suggested above has shown. that almost all discharges which are capable of melting the fusible element have a rate of current rise sufficient to operate the protective gap. The impedance of such a device under normal power frequencyiis low and assuminga typical resistance of 0.029 ohm for the inductance coil a 60 cycle sine wave current of at least 104,000 amperes crest would be required to break down the gap of the dimension suggested. If an impulse current initiates a power frequency current, such as a short circuit, the latter will not persist across the gap but will transfer to the fusible element early in the first half cycle of now. This is due to the fact that the voltage drop across the inductance and fusible element for power frequency currents within the rating of thedevice is less than the voltage required to maintain an arc across the bypass gap.

It will be observed that relatively large adjacent arcing surfaces are provided on the electrodes 33 and 34', and also that the space between the two electrodes is open at both ends so as to allow a rapid dissipation of the gas pressure incident to gap discharge. Moreover, the

I ends of the insulating tube section 25 next adjacent the electrodes are reinforced on their outer-surface by the extensions of the outer electrode sleeve '33 to prevent breakage thereof bythe gas pressure.

The modification illustrated in Fig. 3 is some what similar to that of Fig. 2 in that it is also adapted for insertion into a usual type of cutout-box designed for receiving conventional ex pulsion fuses. This device also includes an insulating tube 4! having spaced line terminals 43 and 44. The line terminals 43 and 44 are so spaced and shaped as to be cooperatively received by the spring contact clips of an ordinary cutout box. Arranged within the insulating tube is a lightning-protected fuse link indicated generally at 42, which in this instance comprises a button head 45 and a conductor enclosed within an insulating tube 45, the conductor including a fusible section 4'!; a flexible cable 48 surrounded by a tensioned retracting spring 49, and a pig-'- tail-50 clamped-by nut 5| to the lower terminal 44. Glampe'd around the conductor between the fusible section: .41 and the cable portion 48 is an enlarged'sleeve 52 forming one electrode of an impulse bypass gap. The insulating tube 45 is provided with an opening 54 on one side adjacent the electrode sleeve 52. Arranged within aligned openings provided through the line terminal 43 and the insulating tube 4! is an electrode pin 55, the inner end of which extends through the opening 54 in the insulating tube 45 -andis spaced from theelectrode sleeve 52 providing -an 'impulsedischarge gap of the desired width. The electrode pin 55 is provided with a shoulder 55 which is held against the outer surface of the line terminal 43 by means of a leaf spring I which engages with the outer end of the pin 55. The outer portion of the electrode pin 55 extends through a cooperating opening provided in a stop member 53 which is provided for the purpose of preventing the pin from being blown out of the openings provided therefor through the line terminal and insulating tube upon the occurrence of heavy arc discharges.

Arranged around the upper end of the insulating tube 4| between the line terminal 43 and the upper terminal cap 53 is a ring iSI of magnetic material. The terminal cap 53 is connected to the line terminal 43 by a conductor 62 extending around the outer surface of the ring GI. The magnetic ring 5| surrounding a portion of the fuse link conductor arranged within the insulating tube sufficiently increases the impedance of this conductor portion so that under an impulse discharge the gap between the electrode members 52 and 55 will break down to bypass .the

transient around the fusible conductor section. It is obvious that the magnetic member BI may be laminated if desired in any suitable manner.

The modification of the lightning protected fuse device shown in Fig. 4 is of the line clampon type designed for fastening onto an overhead line conductor. The device comprises a fuse holder formed of two insulating tube sections II and I2, the adjacent ends of which are threaded into an intermediate terminal sleeve I3. The adjacent ends of the insulating tube sections II and I2 abut against the opposite shoulders of a rib I4 of reduced internal diameter provided on the inside of the sleeve I3, the inner diameter of the shoulder I4 being just slightly less than the inner diameter of the two tube sections II and I2. A lower line terminal I5 is secured upon the lower end of the tube section I2 by means of a suitable clamp I5. Arranged within the insulating tube II, I2 is a fuse link 11, the button head I8 of which extends across the upper end of the insulating tube II while the pigtail I9 thereof extending from the lower end of the tube passes around the pin 8I and is secured by the wing nut 82 to the terminal fixture. The pin 8| is secured to an indicator arm 83 which is pivoted at 84 to an extension of the terminal fixture. Upon rupture of the fuse link and the expulsion of the plgtail from the insulating tube, the indicator arm 83 will be freed to rotate about the pivot 84 to an indicating position.

A metal ferrule 80 provided on the upper end of the tube II, I2 is threaded into a double cap terminal fitting 85 clamping the fuse link head I8 securely therebetween. Threaded into the upper end of fitting 86 and secured therein by set screw 87 is an insulating tubular extension 88 around which is arranged a spool 89 carrying an inductance coil 9!. One end of the coil 9| is connected to the terminal fitting 88 as indicated at 93, while the opposite end is connected through a metal sleeve 94 secured to the upper end of the extension 88 to the clamp-on type line terminal or contact 95. Terminal 95 and sleeve 94 are fixed to the extension tube 88 by screw 85. Conductor strips 98 and 89 effect electrical connection between the line terminal 95 and the intermediate terminal sleeve I3 through spring fingers IOI and I02, respectively. A weatherproof covering I03 which may be either of a suitable insulating material or metal is provided for the upper end of the device includingthe coil 9|.

The fuse link II is more clearly shown in Fig. 5 and comprises a button head I8 and a conductor element comprising a. fusible section I06 and a flexible cable IDI surrounded by a tension spring I08 all arranged within the insulating tube I09. Clamped around the conductor between the fusible section I06 and the cable Ill! is an enlarged metal sleeve I I0 forming one impulse bypass gap electrode. A pair of openings III is provided through the opposite sides of the insulating tube I09 providing discharge passages between the inner electrode III and an outer electrode II2 formed by a metal sleeve fitting closely around the outside of the insulating tube I59. The sleeve II2 has a length considerably greater than the inner electrode member so that sufiicient reinforcement is provided for the insulating tube I09 in the region of the discharge gap so as to prevent the rupture of the tube under pressure resulting from the are occurring across the gap.

It will be apparent that in this modification of fuse link, contact between the two electrode members III] and H2 and shorting out of the fusible section is substantially precluded and a minimum gap spacing therebetween equal to the thickness of the walls of the tube IDS is assured. The outer diameter of the inner electrode is sufficiently smaller than the inner diameter of the insulating tube so that upon melting of the fusible section I06, the electrode portion IID will be withdrawn from the insulating tube without any binding action occurring therebetween. It is furthermore preferred that the tension spring I08 be sufficiently strong so that the electrode I ID will be withdrawn from the insulating tube rapidly, or before the edges of the latter electrode are melted by the are following rupture of the fusible section I06 which melting might cause the formation of burrs on the edges of the electrode and thus hinder its passage through the insulating tube. The electrodes H0, H2 of the fuse link unit are so spaced from the upper end thereof that they will coincide in position with the inwardly extending rib T4 of the terminal sleeve I3 of the fuse holder. The outer diameter of the electrode sleeve H2 is just slightly smaller than the inner diameter of the insulating tube 7 I, I2 and rib I4 so that the sleeve I I2 will lie closely adjacent or contact with the rib I4 at one or more points. It is to be understood, of course, that it is not essential that contact be made between these two parts since the slight gap therebetween would be readily broken down upon the occurrence of an impulse voltage.

During normal operating conditions the power current will fiow between the opposite end terminals and I5 through the sleeve94, th coil 9|, fitting 86, and th fuse link 11. Upon the occurrence of an impulse voltage, such as a lightning discharge, the voltage drop across the impedance coil 9| will be substantially greater than the breakdown voltage for the bypass gap of the fuse link and the discharge current will flow from the sleeve 94, through the conductor strips 98 and 99, terminal sleeve I3 and rib I4, to the outer gap electrode II2, across the gap through the openings III to the inner electrode Ill! and through the cable IIII to the opposite end ter-.

minal I5.

It will be apparent that various elements of the lightning-protected fuse devices described may be interchanged as desired. Thus, the fuse link illustrated in Fig. 5 may be used with either one of the three different devices. Also three different connection arrangements are shown for the by-pass gap electrodes winch-may be readily interchanged either in the form illustrated or by simple modifications which may be readily made by one skilled in the art.

The specific arrangement of the "impedance unit is relatively unimportant but for convenience it may be arranged directly upon the imsulating tube of the fuse device itself. In this regard it will be obvious that it should be so airran'ged as to add impedance only to that circuit including the fusible element.

Having described the principle of operation of our invention in what we consider to represent a preferred embodiment thereof, we desire to have it understood that the specific apparatus shown is merely illustrative and that the invention may be carried out by other means.

1 What we claim as and desire to secure by Letters Patent of the United States is:

1. A fuse device comprising in combination; a

fuse carrier including an elongated tubular insulating housing having terminals respectively adacent opposite ends thereof, a fuse link removably disposed in said housing and connected between said terminals, a by-passbircuit connected l in shunt with at least a portion of Said fuse link including the fusible Section thereof, said circuit including two electrodes disposed intermediate the ends 'of saidho'using and in cooperative spaced relation to form a surge gap within the housing, means relatively permanently supported by said carrieriand associated with said portion of said fuse link for producing high impedance to flow of lightning impulse currents through said fusible section, and means operative dependently upon blowing of said fusible section for effecting relative movement apart of said electrodes.

2. A lightning protected 'fus'e device of the expulsion type comprising the combination of an elongated insulating expulsion tube having a gas discharge end, a pair of terminals on saidtube, means providing it met circuit between said terminals including a fusible element arranged in said tube, means for causingsaid first circuit to have a high impedance to lightning impulse currents, means providing a second circuit between said terminals in shunt with said first circuit and including two electrodes cooperative to form a surge gap in said tube, said second circuit including said surge gap having a relatively low impedance to lightning impulse currents, and means for moving one of said electrodes away from the other upon melting of said fusible element,

3. An expulsion fuse device comprising in combination, a fuse carrier including means providing an elongated expulsion tube having removable closure means at one end and designed for discharge of arc gases at the other end, relatively fixed terminal means adjacent said one end of said tube, a removable fuse link in said tube and connected at said one end with said terminal means, a by-pass circuit connected in shunt with at least a portion of said link which includes the fusible section of the link, said circuit including two electrodescooperative to form a surge gap therebetween in said tube at a substantial distance from said discharge end of the tube, at least one of said electrodes being supported by said fuse link for movement away from the other of the electrodes upon rupture of said fusible scc tion, and means supported by said carrier independently of said fuse link and associated with said portion of the fuse link for producing high impedance to flow of lightning impulse currents through saidfusible section. 4

4. In a fuse device, the combination of means providing an elongated tubular insulating housme having a first terminal adjacent one end thereof and designed for discharge of arc gase atthe other end, said housing having a'second terminal intermediate the ends thereof at a substantial distance from said discharge end of the housing, a removable fuse link including a fusible portion in said housing and connected at one end to said first terminal, said fuse link including an electrode intermediate the ends of said housing at a point adjacent said second terminal, means providing a second electrode cooperative with said first electrode to form a surge gap in said noussulating tube having two terminals one adjacent each of the opposite ends thereof and a third intermediate terminal, a fuse link in said tube and connected between said two terminals, said link including a fusible section and an electrode, a second electrode connected to said third terminal and arranged cooperatively with said first mentioned electrode to form an impulse discharge gap and impedance means secured around said tube and connected between said third terminal and one of said end terminals nearest said fusible section.

6. In a fuse device, the combination of an insulating tube having spaced first and second line terminals, a fuse link in said tube and connected at one end to said first line terminal, said link including a fusible section and an electrode, a second electrode connected to the second line terminal and cooperative with said first mentioned electrode to form a surge gap intermediate the ends of said insulating tube, an inductance device arranged around said tubeand connected between said second line terminal and the second end of said fuse link to cause breakdown of said gap upon the application of a relatively steep front electrical impulse to said second line terminal.

7. In an electric protective device of the expulsion type, the combination of an insulating housing providing an elongated expulsion passage having a gas discharge end, means providing a first circuit including a fusible element in said housing, means for causing said circuit to have high impedance to lightning impulse currents, and means providing a second circuit in shunt with said first circuit and including two electrodes cooperative to form a surge gap therebetween in said housing at a substantialdistance from said discharge end of said passage, at least one of said electrodes being arranged for relative movement away from the other of the electrodes upon melting of said fusible element.

8. A fuse device comprising a pair of terminals, an impedance element and a fuse link including a fusible section connected in series between said terminals, an insulating tubespace'd from an enclosing a portion of said link, said tube having an electrode spaced from said link forming a dis charge gap therebetween, means connecting said electrode to one of said terminals forming a shunt path around said impedance element and saidfusible link section for impulse discharges,

9. A fuse device=comprising a pair of terminals,

an impedance element and a fuse link including a fusible section and an electrode section connected in series between said terminals, an insulating tube spaced from and surrounding a portion of said fuse link, said tube carrying an electrode in a spaced relation with respect to said electrode section of said fuse link forming tube surrounding a portion of the length of said conductor, said tube being comprised of insulation material throughout at least a substantial portion of the length of the tube, said conductor having in said tube .a fusible section, the conductor also having means arranged to serve as an electrode in said tube, a spring forming part of said fuse unit and connected with said conductor for effecting relative movement apart of the ends of said fusible section upon melting thereof, a second electrode supported by said tube cooperative with said first mentioned electrode to form a surge gap in said housing, means for connecting said gap in shunt with at least a portion of said conductor including said fusible section, and means encircling said carrier and associated with said conductor for producing high impedance to fiow of impulse currents through said portion of the conductor including the fusible section. 1

11. In a fuse device, the combination of an elongated tubular insulating housing, a removable fuse unit extending longitudinally in said housing and comprising an elongated conductor and an elongated tube surrounding a portion of the length of said conductor, means for connecting said conductor in an electric circuit, said conductor including a fusible section and having means arranged to serve as an electrode, said tube being constructed of insulation material throughout the major portion of its length and having a conductive part arranged to serve as an electrode in cooperative spaced relation with said first mentioned electrode so as to provide a surge gap, and means including said gap providing a by-pass circuit in shunt with at least a portion of said conductor including said fusible section, said last mentioned means including a contact element supported by said housing and arranged to engage said conductive part of said tube for completing connection of said gap in said by-pass circuit.

12. In a fuse device, an insulating expulsion tube designed for discharge of arc gases at one end and having a terminal adjacent the other end, said tube having a second terminal intermediate the ends thereof, a removable fuse unit extending longitudinally in said tube and including a conductor connected at one end with said first mentioned terminal and a second tube surrounding a substantial portion of the length of said conductor, said second tube being comprised in the main of insulation material but having a conductive part arranged to serve as an electrode, said conductor including a fusible section and having means providing a second electrode cooperative with said first mentioned electrode to form a surge gap, a contact element supported by said first tube in conductive relation with said second terminal and arranged for engagement with said conductive part of said second tube, and means including said second terminal for connecting said gap in shunt with at least a portion of said conductor which includes said fusible section.

13. In a fuse unit for removable installation in an expulsion fuse tube, the combination of an elongated tube comprised of insulation material throughout the major portion of the length thereof and having a conductive part intermediate the ends of the tube adapted to serve as an electrode, a terminal element at one end of said tube, and an elongated conductor connected at one end to said terminal element and extending longitudinally through said tube, said conductor having a fusible section in said tube and having means arranged to serve as an electrode in cooperative spaced relation with said first mentioned electrode.

14. An expulsion fuse device comprising in combination, means providing an insulating expulsion tube having removable closure means at one end and designed for discharge of arc gases at the other end, said tube having a first terminal adjacent said one end thereof and a second terminal intermediate the ends thereof at a substantial distance from said discharge end, a removable fuse unit in said tube and including a conductor having a fusible section and asecond tube surrounding at least a substantial portion of the length of said conductor, said conductor being connected at one end to said first terminal and having means arranged to serve as an electrode adjacent said second terminal, said second tube having an opening opposite said electrode, a conductive element supported by said first tube in conductive relation with said second terminal and having a part disposed adjacent said opening in said second tube and in cooperative spaced relation with said first mentioned electrode to form a surge gap, and means including said second terminal for connecting said gap in shunt with at least a portion of said conductor including said fusible section.

15, In a fuse device, the combination of a conductor having a fusible section, means for connecting the conductor in an electric circuit, a body of magnetic material associated with a part of the conductor for increasing the inductance thereof, and means providing a surge gap connected in shunt with at least a portion of the conductor which includes said fusible section and said part of the conductor.

16. In a fuse device, the combination of a fuse carrier including means providing an elongated tubular insulating housing having a terminal adjacent one end and designed for discharge of gases at the other end, said housing having a second terminal spaced longitudinally of the housing a substantial distance from said first mentioned terminal, a conductor extending longitudinally in said housing and connected at one end to said first terminal, a body of magnetic material supported by said carrier in surrounding relation to said conductor intermediate said terminals, said conductor having means arranged to serve as an electrode in said housing at a point adjacent said second terminal and having a fusible section located intermediate said electrode and said first terminal, means providing a second electrode in cooperative spaced relation with said first mentioned electrode to form a surge gap, means for effecting electric connection between said second electrode and said second terminal, and conductive means supported by said carrier for electrically connecting said second terminal with said first terminal.

17. In a fuse device, the combination of a fuse carrier including means providing an elongated tubular insulating housing having a terminal adjacent one end and designed for discharge of are gases at the other end, said carrier also including anextension on said one end of the housing and a contact element supported on said extension in insulated spaced relation to said terminal,

an inductive coil supported, on said extension and I electrically connected between said contact element and said terminal, said housing having a second terminal intermediate the ends thereof in spaced relation to said first mentioned terminal and to said discharge end of the housing, a fuse link insaid housing connected at one end to said first terminal and having means arrang d to serve as an electrode in said housing at a point adjacent said second terminal, means providin a second electrodein, said housing cooperative with said first mentioned, electrode to form a u e p, m ans f r e ectin e ec ric connection between, said second electrode and said second terminal, and a conductive element supported by said carrier for f ecti e t i connecti n etween said second terminal and the said contact element; on said extension.

18. A fuse device comprising in combination,

a tube of insulating material, a fuse link including a fusible eleme t ositioned n sa d. t be, a inductive winding positiune on the, exteriorof said tube intermediate the ends thereof, a con-.

ducting member securedto one end of said tube and electrica y cn c t d o one end of said induct e w nd ng. a e e f conducting materia secured on said tube intermediate the endsthere of and en agin said in uctive Wind n said in:

duotive. winding being positioned between said member and said-sleeve, and means including a portion ofsaid fuse link adjacent said fusible element for serving as an electrode, said sleeve of conducting material cooperating with said portion of the fuse link serving as an electrode to form an arc gap inparallel with said fusible element, and said inductive winding.

19. In a fuse, spaced conducting means forming an arc gap therebetween, a series arrangement of a fusible elementand inductive means, means electrically connecting said series are rangement across said arc gap, said inductive means being annular in form for receiving said fusible element, and means of insulating material positioned between said inductive means and aid fusible element;

20, In a fuse, a tubular member of insulating material, spa ed. cond ctin me n formin an arc gap therebetween, a series arrangement of fusible element and inductive means, means electrically connecting said series arrangement across said are gap, said inductive means being annular in form for receiving said fusible element .and said tu u ar mem er, a d said us e el ment being positioned in said tubular member.

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