Device for protecting against overcurrents in electric circuits and uses of said device in a fuse link and in a related limiting fuse as well as in fuses for protecting semiconductors

Abstract

The invention provides an overcurrent protection device ( 1 ), comprising a current input terminal ( 2 ); a central terminal ( 3 ) for the output of current overshoots (I s ); and a terminal ( 4 ) for the output of non impulse currents (I c ) which is outwardly connected to the voltage of the central terminal ( 3 ) before the occurrence of the current overshoot (Is) at the input terminal ( 2 ); and an electrical conductor element ( 5 ) connected between the current input and output terminals ( 2 and 4 ); such conductor element showing a reduced self-induction (L) when operating without current overshoots but, which, in case that current overshoots are present at the input terminal ( 2 ), produces a high drop of the induction voltage between such input terminal and the output terminal ( 2 and 4 ); wherein the central terminal ( 3 ) is arranged in the vicinity of the current input terminal ( 2 ) at a distance (D) that may be regulated, so that when, as a result of a current overshoot, the inductive voltage drop between the input terminal and the non-impulse current output terminal ( 2 and 4 ) exceeds the dielectric strength of the dielectric material present between the input and central terminals ( 2 and 3 ), and thanks to the skin effect, an arc is generated between such input and central terminal ( 2 and 3 ), thus preventing the flow of current overshoots (Is) through the conductor element ( 5 ).

What is claimed is: 
     
         1 . An overcurrent protection device for electrical circuits, comprising:
 a current input terminal ( 2 );   a central terminal ( 3 ) for an output of current overshoots (I s ); and   an output terminal ( 4 ) for an output of non impulse currents (I e ) which is outwardly connected to a voltage of the central terminal ( 3 ) before an occurrence of the current overshoot (Is) at the current input terminal ( 2 ); and   an electrical conductor element ( 5 ) connecting the current input terminal ( 2 ) and the output terminal ( 4 ), the electrical conductor element having reduced self-induction (L) at current levels below the overcurrent condition and the electrical conductor element having greater self-induction at the overcurrent condition such that when operating without current overshoots but, which, in case that current overshoots are present at the current input terminal ( 2 ), a high inductive voltage drop (ΔU i =L·dl s /dt) is established between the current input terminal ( 2 ) and the output terminal ( 4 );   wherein the central terminal ( 3 ) is firmly arranged in the vicinity of the current input terminal ( 2 ) at a distance (D) that can be regulated, so that, when the inductive voltage drop (ΔU i ) between the current input terminal ( 2 ) and the output terminal ( 4 ), as a result of a current overshoot, exceeds a dielectric strength of a dielectric material present between the input and central terminals ( 2  and  3 ), also as a result of a skin effect, an electric arc is generated between the current input terminal ( 2 ) and the central terminal ( 3 ), eliminating the flow of the current overshoots (I s ) through the electrical conductor element ( 5 )   wherein the overcurrent protection device is used on an associated limiter fuse ( 12 ) resistant to current overshoots, wherein the associated limiter fuse ( 12 ) respectively comprises:   a first ( 120 ) and a second ( 121 ) connection capsules;   a first contact portion ( 122 ) which is connected to the first connection capsule ( 120 ) and a second contact portion ( 123 ), separated from the first portion, connected to a main fusible element ( 124 ) which is arranged following a spiral layout around a central core ( 125 );   a third contact portion ( 126 ) which is adjacent to the second contact portion and which is electrically insulated from the second portion by means of an insulating portion ( 127 ), wherein a secondary fusible element ( 1240 ) which is resistant to current overshoots and which is also arranged following a spiral layout around the central core ( 125 ) parallel to the main fusible element ( 124 ) is connected to said third contact portion;   a fourth metal contact element ( 128 ) which is connected to the second connection capsule ( 121 ),   wherein the overcurrent protection device ( 1 ) is connected to a fuse link ( 12 ) with the current input terminal ( 2 ) connected to the first contact portion ( 122 ), the output terminal ( 4 ) connected to the second contact portion ( 123 ) and the central terminal ( 3 ) connected to the third contact portion ( 126 ) through a non-fusible connection conductor ( 13 ), and   wherein the over current protection device is used on a fuse link ( 10 ) resistant to impulse currents.   
     
     
         2 . The overcurrent protection device according to  claim 1 , wherein the fuse link ( 10 ) comprises:
 a connecting cap ( 100 );   a link header ( 101 ) connected to the connecting cap;   a first connection, ( 102 ) which is connected to the link header;   a second connection ( 103 ) which is connected to a third connection ( 105 ) of a pigtail connection ( 106 ) through a fusible element ( 104 );   a tensioning wire ( 107 ) coupled between the second and the third connections; and   an ancillary protection tube ( 108 ) wherein the link header, the first and second connections, the fusible element, the tensioning wire and part of the connecting pigtail are encapsulated, and wherein the overcurrent protection device against over currents ( 1 ) is connected at the fuse link ( 10 ) to the first connection of the fuse link ( 102 ) by means of the current input terminal ( 2 ), to the second connection ( 103 ) of the fuse link by means of the output terminal ( 4 ) and to the third connection ( 105 ) of the fuse link by means of the central terminal ( 3 ) through an overcurrent-resistant conducting wire ( 11 ).