Classifications

• • 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
  • H01H85/05—Component parts thereof
  • H01H85/055—Fusible members
  • H01H85/08—Fusible members characterised by the shape or form of the fusible member
  • H01H85/10—Fusible members characterised by the shape or form of the fusible member with constriction for localised fusing

Definitions

• the invention concerns a fusible element of a fast fuse for low fault-current installation protection, which fusible element is made of an electrically conductive strip, whose, with respect to the longitudinal direction, central part is narrowed with respect to the basic width by means of side cut-offs.
• a fusible element of a fast fuse of the described kind has been known. It is made of an electrically conductive strip having a total length L whose, with respect to the longitudinal direction, central part having a length 1 is narrowed with respect to the basic width by means of side cut-offs. A value of the ratio L/1 being between 2 and 4 is cited.
• the cut-offs are performed symmetrically. In the narrowed central part there are performed either circular through-holes or several pairs of semicircular cut-offs at its opposite edges.
• the specified fuse characteristic is achievable essentially by a discrete parameter representing the number of the through- holes or both-sided semicircular cut-offs.
• a fusible element of a fast fuse of the described kind is disclosed in the patent PL 312 750.
• two large side cut-offs are performed so that the width of the narrowed conducting region is far below the width of the electrically conductive strip.
• a row of mutually distant circular through-holes is performed on both sides of the narrowed region.
• the cross section of the narrowed conductive region is dimensioned so that in this place the electric current density is between 295 A/mm and 350 A/mm .
• the specified fuse characteristic is essentially adjustable merely by the width of the narrowed conductive region.
• the technical problem solved by the present invention is to propose such fusible element of a fast fuse for low fault-current installation protection that the fuse characteristic is very steep in the overload range and that it will be possible to simply dimension the fusible element with respect to a nominal interrupting current.
• the fusible element of the invention is further characterized in that in the middle of the second portion having the second reduced width f on both sides of the strip semicircular cut-offs are performed.
• the fusible element of the invention is further characterized in that in the portions having the basic width d in each case at the same distance v from the transversal symmetry axis there are performed a through-hole in the middle of the strip and also semicircular cut-offs on both sides of the strip, whereat the said distance v is equal to a double distance u from the transverse symmetry axis of the semicircular cut-offs performed in the middle of the second portions having the second reduced width f.
• the fusible element of the invention is characterized in that the distance u from the transverse symmetry axis of the semicircular cut-offs in the middle of the second portions having the second reduced width f exceeds a double length w of the portions having the first reduced width e.
• a fusible element according to the invention of a fast fuse for low fault-current installation is represented in the Figure. It is made of an electrically conductive strip, preferably of pure copper, having a total length L. Its, with respect to the longitudinal direction, central part having a length 1 is narrowed with respect to a basic width d of the strip by means of side cut-offs. The cut-offs are performed symmetrically about the transversal symmetry axis S of the fusible element and also about the longitudinal symmetry axis s of the strip. The length 1 of the narrowed part is such that the value of the ratio L/1 is between 2 and 4.
• a stepwise side cut-off is performed, actually within a distance y between portions 3 and 3', both having a first reduced width e.
• the width of the narrowed portion of the strip is at first reduced to a second reduced width f in portions 2, 2 Then this width is reduced to a smallest width g in a portion 1.
• the portions 3, 3' have the width e which is reduced with respect to the basic width d of the electrically conductive strip, whereof the fusible element is made, to such an extent that Kd/e ⁇ 1.5.
• the length x of the central region 1 having the smallest width g is such that l.l ⁇ y/x ⁇ 1.5.
• the portions 3, 3' having the first reduced width e are separated from portions 5, 5' having the basic width d by means of a second portion 4 and 4', respectively, having the second reduced width f.
• the length of the portions 4, 4' is smaller than a length w of the portions 3, 3' having the first reduced width e.
• the said distance v is equal to a double distance u from the transverse symmetry axis S of the semicircular cut-offs 4a, 4b and 4a', 4b', respectively, in the middle of the second portions 4, 4' having the second reduced width f.
• the distance u from the transverse symmetry axis S of the semicircular cut-offs 4a, 4b 4a', 4b' in the middle of the second portions 4 and 4', respectively, having the second reduced width f exceeds a double length w of the portions 3, 3' having the first reduced width e.
• the central section A comprises the stepwise region 2-1-2' and from the middle of the region 3 reaches to the middle of the region 3'.
• the central section A continues into the sections B and B' that over the portion 4 and 4', respectively, reach each time for a distance w/2 into the portions 5 and 5', respectively, having the basic width d of the strip.
• a heat dissipation from the section A is limited.
• the sections B and B' support a quenching of the electric arc due to a short-circuit current.
• the sections B and B' continue into the sections C and C, respectively, that also support the quenching of the electric arc. At the same time they decrease the heat flow from the section A towards contact blades provided to fasten the fusible element.

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• Fuses (AREA)

Priority Applications (1)

Applications Claiming Priority (2)

Publications (1)

Family

ID=27786703

Family Applications (1)

Country Status (4)

Cited By (2)

Citations (6)

• 2002
  • 2002-02-28 SI SI200200061A patent/SI21154A/sl not_active IP Right Cessation
• 2003
  • 2003-02-21 AU AU2003214789A patent/AU2003214789A1/en not_active Abandoned
  • 2003-02-21 WO PCT/SI2003/000006 patent/WO2003075298A1/en not_active Application Discontinuation
  • 2003-02-21 PL PL370776A patent/PL200261B1/pl unknown

Patent Citations (6)

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