EP0640995A1 - Electrical resistor and application of this resistor in a current limiter - Google Patents

Electrical resistor and application of this resistor in a current limiter Download PDF

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Publication number
EP0640995A1
EP0640995A1 EP93113545A EP93113545A EP0640995A1 EP 0640995 A1 EP0640995 A1 EP 0640995A1 EP 93113545 A EP93113545 A EP 93113545A EP 93113545 A EP93113545 A EP 93113545A EP 0640995 A1 EP0640995 A1 EP 0640995A1
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EP
European Patent Office
Prior art keywords
resistance
polymer matrix
layer
resistance element
element according
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Application number
EP93113545A
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German (de)
French (fr)
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EP0640995B1 (en
Inventor
Tudor Dr. Baiatu
Felix Dr. Greuter
Ralf Dr. Strümpler
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ABB Research Ltd Switzerland
ABB Research Ltd Sweden
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ABB Research Ltd Switzerland
ABB Research Ltd Sweden
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Priority to DE59306823T priority Critical patent/DE59306823D1/en
Priority to EP93113545A priority patent/EP0640995B1/en
Priority to US08/291,903 priority patent/US5602520A/en
Priority to CA002130622A priority patent/CA2130622A1/en
Priority to JP6199857A priority patent/JPH07153604A/en
Publication of EP0640995A1 publication Critical patent/EP0640995A1/en
Application granted granted Critical
Publication of EP0640995B1 publication Critical patent/EP0640995B1/en
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01C—RESISTORS
    • H01C7/00—Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered semi-conducting material with or without insulating material
    • H01C7/02—Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered semi-conducting material with or without insulating material having positive temperature coefficient
    • H01C7/027—Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered semi-conducting material with or without insulating material having positive temperature coefficient consisting of conducting or semi-conducting material dispersed in a non-conductive organic material
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01C—RESISTORS
    • H01C7/00—Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered semi-conducting material with or without insulating material
    • H01C7/13—Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered semi-conducting material with or without insulating material current responsive

Definitions

  • the invention is based on an electrical resistance element according to the preamble of claim 1.
  • the invention also relates to the use of such a resistance element in a current limiter.
  • a resistance element of the type mentioned at the outset is known from EP 0 363 746 A1 and from the article by T. Hansson published in ABB Review 4/92 (1992), pp. 35-38, "Polyethylene current monitor for short-circuit protection".
  • This resistance element consists of a thin plastic plate made of filler-containing polyethylene, which is arranged between two comparatively thick electrodes. At room temperature, this resistance element has a very low resistance and can then easily carry the nominal current flowing in a low-voltage distribution network. The resistance element can also easily carry a nominal current that is several times higher for several seconds, since the comparatively thick electrodes can temporarily absorb the current heat generated in the resistance element.
  • the temperature of the resistance element rises very quickly in a very thin surface layer on the electrodes, which are preferably made of silver-plated copper, and melts the polyethylene in this layer.
  • the resistance of the resistance element increases abruptly and reaches approximately 30 times its initial value in less than a millisecond.
  • the short-circuit current is thereby greatly reduced and can now be switched off with a circuit breaker of low short-circuit switching capacity connected in series with the resistance element.
  • the invention has for its object to provide an electrical resistance element of the type mentioned, which can limit short-circuit currents permanently.
  • the object of the invention is also the use of this resistance element in a current limiter for nominal voltages of at least 500 V.
  • the electrical resistance element according to the invention can be produced in a simple and inexpensive manner from commercially available components, such as a polymer matrix and a suitable filler. In the low-resistance state, it has a lower specific resistance than the resistance element according to the prior art and can therefore carry larger nominal currents with the same geometric dimensions. In addition, such a resistance element can also switch off short-circuit currents without additional protective circuitry, such as switching devices connected in series with the resistance element.
  • a resistance element 10 shown in FIGS. 1 to 3 contains a resistance body 3 with PTC behavior arranged between two plate-shaped, solid, copper-containing electrodes 1, 2. Below a transition temperature T c , this resistance element 10 has a low specific cold resistance and, after installation in a current limiter, forms a path that runs between the two electrodes 1, 2 and that normally leads to the nominal current. Above the transition temperature T c changes the resistance element 10 abruptly changes its electrical conductivity and then has a high specific hot resistance compared to its specific cold resistance.
  • the resistance body 3 is formed from a polymer matrix preferably containing a thermosetting or thermoplastic or an elastomer. Two filler components formed by electrically conductive particles are embedded in this matrix, which typically consists of polyethylene.
  • a first of these filler components is a material which, like carbon in particular, in the resistance element 10 leads to the abrupt change in resistance known from the prior art due to a surface layer forming when a short-circuit current occurs.
  • the second filler component can be a metal, such as Ag, Au, Ni, Pd and / or Pt, and / or a boride, silicide, oxide and / or carbide, such as SiC, TiC, TiB2, MoSi2, WSi2, RuO2 or V2O3, each in undoped or doped form.
  • the proportion of filler is chosen to be high, for example between 30 and 50 percent by volume.
  • the size of the particles of the first filler component is typically up to 1 ⁇ m, that of the second filler component typically between 1 and 100 ⁇ m. Because the average size of particles of the first filler component is at least one order of magnitude smaller than the average size of particles of the second filler component, the particles of the first filler component are arranged in gaps between the particles of the second filler component.
  • the second filler component can thus form numerous percolating current paths, which are necessary for a high nominal current carrying capacity, at operating temperature. At the same time, however, there is also a sufficient amount of first filler component in the regions of the resistance body near the surface to form the current-limiting surface layer.
  • the first and second filler components are mixed into a polymer, such as in particular polyethylene, with a shear mixer or with an extruder.
  • a polymer such as in particular polyethylene
  • this composite is formed by hot pressing and in the case of epoxies by casting and subsequent curing at elevated temperature to form the plate-shaped resistance body 3.
  • the flat electrodes 1, 2 are constantly pressed against the end faces of the resistance body by means of spring pressure.
  • the second fillers provided in the resistance body 3 of the resistance element 10 form low-resistance current paths passing through the resistance body 3 with an order of magnitude lower specific resistance than a resistance element according to the prior art filled with a comparable amount, but exclusively with the first filler component.
  • a resistance element 10 therefore has a significantly increased nominal current carrying capacity.
  • This behavior of the resistance element 10 is achieved, as described above, by adding suitably sized and dimensioned filler components to the polymer.
  • at least one of the end faces of the resistance body 3 is formed by a thin layer 4 of the polymer matrix filled with the first filler component.
  • This layer 4 can be produced by diffusing or pressing carbon black into the filler-free or already filled with second filler component, such as in particular TiB2, polymer matrix.
  • Layer 4 should be as thin as possible, but still thick enough to withstand a required number of short-circuit actions. The thickness of layer 4 is typically a few ⁇ m.
  • the second filler component can be uniformly distributed in the polymer matrix.
  • the concentration of the second filler component can also be from the middle of the Gradually remove the resistance body towards electrode 1 and / or 2.
  • a particularly pronounced interface 41 is achieved between the layer 4 and the remaining layer of the resistance body 3 that is only doped with the second filler component.
  • the end face of the resistance body 3 contacted with the electrode 2 can also be formed as a thin layer filled with the first filler component. This layer is provided with the reference number 5.
  • Such a resistance element does have a somewhat greater resistance than the resistance element according to FIG. 2 during nominal current operation, but then forms two current-limiting surface layers connected in series when a short-circuit current occurs.
  • the boundary layer 41 and a boundary layer 51 provided between the layer 5 and the layer doped with the second filler component contain a metal grid and / or a flat metallization. This favors a uniform electrical field load on the individual layers of the resistance body 3.
  • the layers 4 and 5 have interruptions 6 which are filled with polymer containing only second filler component.
  • Such a resistance element is distinguished from the resistance element according to FIG. 1 by an increased nominal current carrying capacity.
  • the layers 4 and 5 here consist of regions 7, which also contain first and possibly also second filler component, which primarily serve to generate a plasma for forming the surface layer.
  • each of the electrodes 1, 2 facing away from the resistance body 3 can carry cooling fins 8.
  • each of the electrodes 1, 2 can also carry another heat sink, for example a liquid cooler.
  • Such heat sinks connected to the outer surface of at least one of the two electrodes 1, 2 can additionally increase the nominal current carrying capacity as a result of increased heat dissipation.
  • an intermediate layer 9 made of electrically insulating but thermally highly conductive material can be arranged between the electrodes and the heat sinks, for example the cooling fins 8, which provides the potential separation between the resistance element 10 and the heat sinks serves.
  • This layer can be formed by a filler, such as aluminum oxide, aluminum nitride and / or boron nitride, filled with silicone film or a ceramic disk, for example based on Al2O3 or AlN.
  • FIG. 4 shows a current limiter which can be used for nominal voltages up to 1.5 kV, in which three resistance elements 10 which are designed in accordance with the above embodiments and are connected to one another in series are used. Instead of three resistance elements 10, only two or possibly four or more resistance elements can also be used.
  • the electrodes 1, 2 of these resistance elements have extensions 11, 12. Between the two extensions 11 and 12 of the two electrodes 1, 2, a resistor 14 is clamped elastically resiliently with the aid of two resilient contact elements 13.
  • This resistor can have linear voltage behavior, but is advantageously a non-linear, voltage-dependent resistor, for example based on metal oxide.
  • a particularly space-saving design of the current limiter is achieved if the resistors 14 are arranged in a step-like manner, for example rotated by 90 ° and 180 ° relative to one another. With a suitable design of the electrodes 1, 2 and the intermediate insulation, the current-limiting resistance elements 10 and the resistors 14 can also be arranged one above the other. The current limiter then has a particularly easy to handle, columnar structure.

Abstract

The electrical resistor element (10) contains, arranged between two plane-parallel electrodes (1, 2) exposed to pressure, a resistor body (3) having a positive temperature characteristic and comprising a polymer matrix and two filler components of electrically conductive particles embedded in the polymer matrix (4). When a short-circuit occurs, the resistivity of the resistor body (3) changes suddenly above a temperature limit value in a surface layer located on the electrodes and containing at least a first of the two filler components. A second of the two filler components is selected such that a binder material containing at least a polymer matrix and a second filler component has a positive temperature characteristic with a step response which is at least an order of magnitude higher than the surface layer. At the same time, this binder material has a resistivity which is at least an order of magnitude less than a binder material formed by polymer matrix and a first filter component. The resistor element has a high rated current-carrying capacity and can limit large short-circuit currents with long-lasting effect. <IMAGE>

Description

TECHNISCHES GEBIETTECHNICAL AREA

Bei der Erfindung wird ausgegangen von einem elektrischen Widerstandselement nach dem Oberbegriff von Patentanspruch 1. Die Erfindung betrifft auch die Verwendung eines derartigen Widerstandselemente in einem Strombegrenzer.The invention is based on an electrical resistance element according to the preamble of claim 1. The invention also relates to the use of such a resistance element in a current limiter.

STAND DER TECHNIKSTATE OF THE ART

Ein Widerstandselement der eingangs genannten Art ist aus EP 0 363 746 A1 und aus dem in ABB Technik 4/92 (1992), S.35-38 veröffentlichten Aufsatz von T. Hansson "Polyäthylen-Stromwächter für den Kurzschlußschutz" bekannt. Dieses Widerstandselement besteht aus einer dünnen Kunststoffplatte aus füllstoffhaltigem Polyäthylen, welche zwischen zwei vergleichsweise dicken Elektroden angeordnet ist. Bei Raumtemperatur weist dieses Widerstandselement einen sehr geringen Widerstand auf und kann dann problemlos den in einem Niederspannungs-Verteilnetz fließenden Nennstrom führen. Das Widerstandselement kann ohne weiteres über mehrere Sekunden auch einen um das Mehrfache erhöhten Nennstrom führen, da die vergleichsweise dicken Elektroden die im Widerstandselement erzeugte Stromwärme vorübergehend aufnehmen können. Beim Auftreten eines Kurzschlußstromes hingegen steigt die Temperatur des Widerstandselements in einer sehr dünnen Oberflächenschicht an den vorzugsweise aus versilbertem Kupfer bestehenden Elektroden sehr rasch an und schmilzt das in dieser Schicht befindliche Polyäthylen. Hierdurch erhöht sich der Widerstand des Widerstandselements sprunghaft und erreicht in weniger als einer Millisekunde das ca. 30-fache seines Anfangswerts. Der Kurzschlußstrom wird dadurch stark verringert und kann nun mit einem in Serie zum Widerstandselement geschalteten Leistungsschalter von geringem Kurzschlußschaltvermögen abgeschaltet werden.A resistance element of the type mentioned at the outset is known from EP 0 363 746 A1 and from the article by T. Hansson published in ABB Review 4/92 (1992), pp. 35-38, "Polyethylene current monitor for short-circuit protection". This resistance element consists of a thin plastic plate made of filler-containing polyethylene, which is arranged between two comparatively thick electrodes. At room temperature, this resistance element has a very low resistance and can then easily carry the nominal current flowing in a low-voltage distribution network. The resistance element can also easily carry a nominal current that is several times higher for several seconds, since the comparatively thick electrodes can temporarily absorb the current heat generated in the resistance element. At the On the other hand, if a short-circuit current occurs, the temperature of the resistance element rises very quickly in a very thin surface layer on the electrodes, which are preferably made of silver-plated copper, and melts the polyethylene in this layer. As a result, the resistance of the resistance element increases abruptly and reaches approximately 30 times its initial value in less than a millisecond. The short-circuit current is thereby greatly reduced and can now be switched off with a circuit breaker of low short-circuit switching capacity connected in series with the resistance element.

KURZE DARSTELLUNG DER ERFINDUNGSUMMARY OF THE INVENTION

Der Erfindung, wie sie in Patentanspruch 1 angegeben ist, liegt die Aufgabe zugrunde, ein elektrisches Widerstandselement der eingangs genannten Art zu schaffen, welches Kurzschlußströme dauerhaft begrenzen kann. Aufgabe der Erfindung ist zugleich auch die Verwendung dieses Widerstandselements in einem Strombegrenzer für Nennspannungen von mindestens 500 V.The invention, as specified in claim 1, has for its object to provide an electrical resistance element of the type mentioned, which can limit short-circuit currents permanently. The object of the invention is also the use of this resistance element in a current limiter for nominal voltages of at least 500 V.

Das elektrische Widerstandselement nach der Erfindung kann aus kommerziell erhältlichen Komponenten, wie einer Polymermatrix und einem geeigneten Füllstoff in einfacher und kostengünstiger Weise hergestellt werden. Es weist im niederohmigen Zustand einen geringeren spezifischen Widerstand auf als das Widerstandselement nach dem Stand der Technik auf und kann daher bei gleichen geometrischen Abmessungen größere Nennströme führen. Zudem kann ein solches Widerstandselement Kurzschlußströme auch ohne zusätzliche Schutzbeschaltung, wie etwa mit dem Widerstandselement in Serie geschaltete Schaltgeräte, abschalten.The electrical resistance element according to the invention can be produced in a simple and inexpensive manner from commercially available components, such as a polymer matrix and a suitable filler. In the low-resistance state, it has a lower specific resistance than the resistance element according to the prior art and can therefore carry larger nominal currents with the same geometric dimensions. In addition, such a resistance element can also switch off short-circuit currents without additional protective circuitry, such as switching devices connected in series with the resistance element.

KURZE BESCHREIBUNG DER ZEICHNUNGENBRIEF DESCRIPTION OF THE DRAWINGS

Bevorzugte Ausführungsbeispiele der Erfindung und die damit erzielbaren weiteren Vorteile werden nachfolgend anhand von Zeichnungen näher erläutert. Hierbei zeigt:

Fig.1
eine Aufsicht auf einen Schnitt durch einen Teil einer ersten Ausführungsform des elektrischen Widerstandelements nach der Erfindung,
Fig.2
eine Aufsicht auf einen Schnitt durch einen Teil einer zweiten Ausführungsform des elektrischen Widerstandselements nach der Erfindung,
Fig.3
eine Aufsicht auf einen Schnitt durch eine dritte Ausführungsform des elektrischen Widerstandelements nach der Erfindung, und
Fig.4
eine Aufsicht auf einen Schnitt durch einen für eine Nennspannung von 1,5 kV vorgesehenen Strombegrenzer, in den Widerstandselemente nach der Erfindung eingebaut sind.
Preferred exemplary embodiments of the invention and the further advantages achievable therewith are explained in more detail below with reference to drawings. Here shows:
Fig. 1
2 shows a plan view of a section through part of a first embodiment of the electrical resistance element according to the invention,
Fig. 2
2 shows a plan view of a section through part of a second embodiment of the electrical resistance element according to the invention,
Fig. 3
a plan view of a section through a third embodiment of the electrical resistance element according to the invention, and
Fig. 4
a plan view of a section through a current limiter provided for a nominal voltage of 1.5 kV, in which resistance elements according to the invention are installed.

WEGE ZUR AUSFÜHRUNG DER ERFINDUNGWAYS OF CARRYING OUT THE INVENTION

In allen Figuren bezeichnen gleiche Bezugszeichen auch gleichwirkende Teile. Ein in den Figuren 1 bis 3 dargestelltes Widerstandselement 10 enthält einen zwischen zwei plattenförmigen, massiven, kupferhaltigen Elektroden 1, 2 angeordneten Widerstandskörper 3 mit PTC-Verhalten. Unterhalb einer Übergangstemperatur Tc weist dieses Widerstandselement 10 einen geringen spezifischen Kaltwiderstand auf und bildet nach Einbau in einen Strombegrenzer einen zwischen den beiden Elektroden 1, 2 verlaufenden und im Normalfall Nennstrom führenden Pfad. Oberhalb der Übergangstemperatur Tc ändert das Widerstandselement 10 sprunghaft seine elektrische Leitfähigkeit und weist dann einen verglichen mit seinem spezifischen Kaltwiderstand großen spezifischen Heißwiderstand auf.In all figures, the same reference symbols also designate parts with the same effect. A resistance element 10 shown in FIGS. 1 to 3 contains a resistance body 3 with PTC behavior arranged between two plate-shaped, solid, copper-containing electrodes 1, 2. Below a transition temperature T c , this resistance element 10 has a low specific cold resistance and, after installation in a current limiter, forms a path that runs between the two electrodes 1, 2 and that normally leads to the nominal current. Above the transition temperature T c changes the resistance element 10 abruptly changes its electrical conductivity and then has a high specific hot resistance compared to its specific cold resistance.

Der Widerstandskörper 3 ist gebildet von einer vorzugsweise ein Duro- oder Thermoplast oder ein Elastomer enthaltenden Polymermatrix. In diese typischerweise aus Polyäthylen bestehende Matrix sind zwei von elektrisch leitenden Teilchen gebildete Füllstoffkomponenten eingebettet.The resistance body 3 is formed from a polymer matrix preferably containing a thermosetting or thermoplastic or an elastomer. Two filler components formed by electrically conductive particles are embedded in this matrix, which typically consists of polyethylene.

Eine erste dieser Füllstoffkomponenten ist ein Material, welches - wie insbesondere Kohlenstoff - beim Widerstandselement 10 zu der vom Stand der Technik her bekannten sprunghaften Widerstandsänderung aufgrund einer sich beim Auftreten eines Kurzschlußstromes bildenden Oberflächenschicht führt.A first of these filler components is a material which, like carbon in particular, in the resistance element 10 leads to the abrupt change in resistance known from the prior art due to a surface layer forming when a short-circuit current occurs.

Eine zweite dieser Füllstoffkomponenten ist so ausgewählt, daß ein Polymermatrix, zweite Füllstoffkomponente sowie gegebenenfalls auch erste Füllstoffkomponente enthaltender Verbundwerkstoff PTC-Verhalten aufweist mit einem gegenüber der Oberflächenschicht um mindestens eine Größenordnung höheren Sprungverhalten des Widerstandes. Zugleich besitzt der vorgenannte Verbundwerkstoff einen um mindestens eine Größenordnung geringeren spezifischen Widerstand als ein von der Polymermatrix und der ersten Füllstoffkomponente gebildeter Vergleichverbundwerkstoff bei gleicher Menge an Füllstoff. Die zweite Füllstoffkomponente kann ein Metall, wie Ag, Au, Ni, Pd und/oder Pt, und/oder ein Borid, Silizid, Oxid und/oder Carbid, wie etwa SiC, TiC, TiB₂, MoSi₂, WSi₂, RuO₂ oder V₂O₃, jeweils in undotierter oder dotierter Form, sein. Der Füllstoffanteil ist hoch gewählt und kann beispielsweise zwischen 30 und 50 Volumenprozent betragen.A second of these filler components is selected so that a polymer matrix, second filler component and possibly also first filler component-containing composite material exhibits PTC behavior with a jump behavior of the resistance that is at least one order of magnitude higher than that of the surface layer. At the same time, the aforementioned composite material has a specific resistance that is at least one order of magnitude lower than a comparative composite material formed by the polymer matrix and the first filler component with the same amount of filler. The second filler component can be a metal, such as Ag, Au, Ni, Pd and / or Pt, and / or a boride, silicide, oxide and / or carbide, such as SiC, TiC, TiB₂, MoSi₂, WSi₂, RuO₂ or V₂O₃, each in undoped or doped form. The proportion of filler is chosen to be high, for example between 30 and 50 percent by volume.

Die Größe der Teilchen der erste Füllstoffkomponente beträgt typischerweise bis zu 1µm, diejenige der zweiten Füllstoffkomponente typischerweise zwischen 1 und 100µm. Dadurch, dass die mittlere Größe von Teilchen der ersten Füllstoffkomponente um mindestens eine Größenordnung kleiner ist als die mittlere Größe von Teilchen der zweiten Füllstoffkomponente, sind die Teilchen der ersten Füllstoffkomponente in Lücken zwischen den Teilchen der zweiten Füllstoffkomponente angeordnet. Die zweite Füllstoffkomponente kann so bei Betriebstemperatur zahlreiche, für eine hohe Nennstromtragfähigkeit notwendige, perkolierende Strompfade ausbilden. Zugleich befindet sich aber auch in den oberflächennahen Bereichen des Widerstandskörpers eine zur Bildung der strombegrenzenden Oberflächenschicht ausreichend Menge an erster Füllstoffkomponente.The size of the particles of the first filler component is typically up to 1 μm, that of the second filler component typically between 1 and 100 μm. Because the average size of particles of the first filler component is at least one order of magnitude smaller than the average size of particles of the second filler component, the particles of the first filler component are arranged in gaps between the particles of the second filler component. The second filler component can thus form numerous percolating current paths, which are necessary for a high nominal current carrying capacity, at operating temperature. At the same time, however, there is also a sufficient amount of first filler component in the regions of the resistance body near the surface to form the current-limiting surface layer.

Zur Herstellung eines Widerstandselementes 10 nach der Erfindung werden mit einem Schermischer oder mit einem Extruder die erste und die zweite Füllstoffkomponente, mit Vorteil Ruß und Titandiborid (TiB₂), in ein Polymer, wie insbesondere Polyäthylen, eingemischt. Dieses Komposit wird bei Thermoplasten durch Heißpressen und bei Epoxiden durch Gießen und anschliessendes Aushärten bei erhöhter Temperatur zum plattenförmigen Widerstandskörper 3 geformt. Die plan ausgebildeten Elektroden 1, 2 werden mittels Federdruck ständig gegen die Stirnflächen des Widerstandskörpers gepreßt.To produce a resistance element 10 according to the invention, the first and second filler components, advantageously carbon black and titanium diboride (TiB₂), are mixed into a polymer, such as in particular polyethylene, with a shear mixer or with an extruder. In the case of thermoplastics, this composite is formed by hot pressing and in the case of epoxies by casting and subsequent curing at elevated temperature to form the plate-shaped resistance body 3. The flat electrodes 1, 2 are constantly pressed against the end faces of the resistance body by means of spring pressure.

Im Normalbetrieb bilden die im Widerstandskörper 3 des Widerstandselementes 10 vorgesehenen zweiten Füllstoffe durch den Widerstandskörper 3 hindurchgehende niederohmige Strompfade mit einem um Größenordnungen geringeren spezifischen Widerstand als ein mit vergleichbarer Menge, aber ausschließlich mit erster Füllstoffkomponente, gefülltes Widerstandselement nach dem Stand der Technik. Gegenüber einem vergleichbar dimensionierten Widerstandselement nach dem Stand der Technik weist ein solches Widerstandselement 10 daher eine wesentlich erhöhte Nennstromtragfähigkeit aus.In normal operation, the second fillers provided in the resistance body 3 of the resistance element 10 form low-resistance current paths passing through the resistance body 3 with an order of magnitude lower specific resistance than a resistance element according to the prior art filled with a comparable amount, but exclusively with the first filler component. Compared to a comparable dimensioned resistance element according to the prior art Such a resistance element 10 therefore has a significantly increased nominal current carrying capacity.

Beim Auftreten eines Kurzschlußstromes bildet sich aus dem auf den Elektroden 1, 2 aufliegenden Polyäthylen und dem Ruß innerhalb einer Millisekunde die zuvor erwähnte dünne Oberflächenschicht aus. Diese Schicht verringert den Kurzschlußstrom bereits ganz erheblich. Durch den noch fließenden Kurzschlußstrom erwärmt sich der verbleibende Teil des Widerstandskörpers 3. Sobald die Temperatur des verbleibenden Teils des Widerstandskörpers 3 die Übergangstemperatur Tc überschreitet, erhöht sich der Widerstand des Widerstandskörpers sprunghaft um mehrere Größenordnungen und begrenzt den Kurzschlußstrom unter elektrischer und thermischer Entlastung der Oberflächenschicht dauerhaft. Der Kurzschlußstrom ist nun abgeschaltet. Das Widerstandselement 10 kühlt sich sodann ab und kann nun wieder Nennstrom führen.If a short-circuit current occurs, the aforementioned thin surface layer is formed from the polyethylene lying on the electrodes 1, 2 and the soot within one millisecond. This layer already considerably reduces the short-circuit current. Due to the still flowing short-circuit current, the remaining part of the resistance body 3 heats up. As soon as the temperature of the remaining part of the resistance body 3 exceeds the transition temperature T c , the resistance of the resistance body increases by several orders of magnitude and limits the short-circuit current with electrical and thermal relief of the surface layer permanent. The short-circuit current is now switched off. The resistance element 10 then cools down and can now carry rated current again.

Dieses Verhalten des Widerstandselements 10 wird wie zuvor beschrieben durch Zumischen geeignet bemessener und dimensionierter Füllstoffkomponenten zum Polymer erreicht. Es kann aber auch dadurch erreicht werden, daß wie in den Figuren 1 bis 3 dargestellt ist, mindestens eine der Stirnflächen des Widerstandskörpers 3 von einer dünnen, mit erster Füllstoffkomponente gefüllten Schicht 4 der Polymermatrix gebildet ist. Diese Schicht 4 kann durch Eindiffundieren oder Einpressen von Ruß in die füllstoffreie oder bereits mit zweiter Füllstoffkomponente, wie insbesondere TiB₂, gefüllte Polymermatrix hergestellt werden. Die Schicht 4 sollte möglichst dünn, aber dennoch dick genug sein, um eine geforderte Anzahl an Kurzschlußhandlungen zu überstehen. Typischerweise beträgt die Dicke der Schicht 4 einige µm.This behavior of the resistance element 10 is achieved, as described above, by adding suitably sized and dimensioned filler components to the polymer. However, it can also be achieved that, as shown in FIGS. 1 to 3, at least one of the end faces of the resistance body 3 is formed by a thin layer 4 of the polymer matrix filled with the first filler component. This layer 4 can be produced by diffusing or pressing carbon black into the filler-free or already filled with second filler component, such as in particular TiB₂, polymer matrix. Layer 4 should be as thin as possible, but still thick enough to withstand a required number of short-circuit actions. The thickness of layer 4 is typically a few μm.

In der Polymermatrix kann die zweite Füllstoffkomponente gleichmäßig verteilt sein. Die Konzentration der zweiten Füllstoffkomponente kann aber auch von der Mitte des Widerstandskörpers zur Elektrode 1 und/oder 2 hin graduell abnehmen. Dadurch wird eine besonders ausgeprägte Grenzfläche 41 zwischen der Schicht 4 und der nur mit zweiter Füllstoffkomponente dotierten, verbleibenden Schicht des Widerstandskörpers 3 erreicht.The second filler component can be uniformly distributed in the polymer matrix. The concentration of the second filler component can also be from the middle of the Gradually remove the resistance body towards electrode 1 and / or 2. As a result, a particularly pronounced interface 41 is achieved between the layer 4 and the remaining layer of the resistance body 3 that is only doped with the second filler component.

Wie aus Fig. 1 ersichtlich ist, kann im Unterschied zur Ausführungsform gemäß Fig. 2, auch die mit der Elektrode 2 kontaktierte Stirnfläche des Widerstandskörpers 3 als dünne, mit erster Füllstoffkomponente gefüllte Schicht ausgebildet sein. Diese Schicht ist mit dem Bezugszeichen 5 versehen. Ein solches Widerstandselement weist zwar bei Nennstrombetrieb einen etwas größeren Widerstand als das Widerstandselement gemäß Fig. 2 auf, bildet dann aber beim Auftreten eines Kurzschlußstromes zwei miteinander in Serie geschaltete, strombegrenzende Oberflächenschichten.As can be seen from FIG. 1, in contrast to the embodiment according to FIG. 2, the end face of the resistance body 3 contacted with the electrode 2 can also be formed as a thin layer filled with the first filler component. This layer is provided with the reference number 5. Such a resistance element does have a somewhat greater resistance than the resistance element according to FIG. 2 during nominal current operation, but then forms two current-limiting surface layers connected in series when a short-circuit current occurs.

Die Grenzschicht 41 und eine zwischen der Schicht 5 und der mit zweiter Füllstoffkomponente dotierten Schicht vorgesehene Grenzschicht 51 enthalten ein Metallgitter und/oder eine flächige Metallisierung. Hierdurch wird eine gleichmäßige elektrische Feldbelastung der einzelnen Schichten des Widerstandskörpers 3 begünstigt.The boundary layer 41 and a boundary layer 51 provided between the layer 5 and the layer doped with the second filler component contain a metal grid and / or a flat metallization. This favors a uniform electrical field load on the individual layers of the resistance body 3.

Bei der Ausführungsform des Widerstandselements gemäß Fig.3 weisen die Schichten 4 und 5 Unterbrechungen 6 auf, die mit lediglich zweite Füllstoffkomponente enthaltendem Polymer gefüllt sind. Ein solches Widerstandselement zeichnet sich gegenüber dem Widerstandselement gemäß Fig. 1 durch eine erhöhte Nennstromtragfähigkeit aus. Die Schichten 4 und 5 bestehen hierbei aus erste und gegebenenfalls auch zweite Füllstoffkomponente enthaltenden Bereichen 7, welche primär der Erzeugung eines Plasmas zur Bildung der Oberflächenschicht dienen.In the embodiment of the resistance element according to FIG. 3, the layers 4 and 5 have interruptions 6 which are filled with polymer containing only second filler component. Such a resistance element is distinguished from the resistance element according to FIG. 1 by an increased nominal current carrying capacity. The layers 4 and 5 here consist of regions 7, which also contain first and possibly also second filler component, which primarily serve to generate a plasma for forming the surface layer.

Wie aus Fig.3 ersichtlich ist, können die vom Widerstandskörpers 3 abgewandten Flächen der Elektroden 1, 2 Kühlrippen 8 tragen. Anstelle von Kühlrippen 8 kann jede der Elektroden 1, 2 auch irdendeinen anderen Kühlkörper, beispielsweise einen Flüssigkeitskühler, tragen. Durch solche mit der Außenfläche zumindest einer der beiden Elektroden 1, 2 verbundene Kühlkörper kann infolge erhöhter Wärmeabfuhr die Nennstromtragfähigeit zusätzlich gesteigert werden.As can be seen from FIG. 3, the surfaces of the electrodes 1, 2 facing away from the resistance body 3 can carry cooling fins 8. Instead of cooling fins 8, each of the electrodes 1, 2 can also carry another heat sink, for example a liquid cooler. Such heat sinks connected to the outer surface of at least one of the two electrodes 1, 2 can additionally increase the nominal current carrying capacity as a result of increased heat dissipation.

Wie in Fig.3 bei der Elektrode 2 dargestellt ist, kann zwischen den Elektroden und den Kühlkörpern, beispielsweise den Kühlrippen 8, eine Zwischenschicht 9 aus elektrisch isolierendem, aber thermisch gut leitendem Material angeordnet sein, welche der Potentialtrennung zwischen dem Widerstandselement 10 und den Kühlkörpern dient. Diese Schicht kann von einer mit Füllstoff, wie Aluminiumoxid, Aluminiumnitrid und/oder Bornitrid, gefüllten Silikonfolie oder einer Keramikscheibe, etwa auf der Basis von Al₂O₃ oder AlN, gebildet sein.As shown in FIG. 3 for the electrode 2, an intermediate layer 9 made of electrically insulating but thermally highly conductive material can be arranged between the electrodes and the heat sinks, for example the cooling fins 8, which provides the potential separation between the resistance element 10 and the heat sinks serves. This layer can be formed by a filler, such as aluminum oxide, aluminum nitride and / or boron nitride, filled with silicone film or a ceramic disk, for example based on Al₂O₃ or AlN.

In Fig.4 ist ein für Nennspannungen bis zu 1,5 kV einsetzbarer Strombegrenzer dargestellt, in dem drei gemäß den vorstehenden Ausführungsformen ausgebildete und miteinander in Serie geschaltete Widerstandselemente 10 verwendet werden. Anstelle von drei Widerstandselementen 10 können auch lediglich zwei oder gegebenenfalls vier und mehr Widerstandselemente verwendet werden. Die Elektroden 1, 2 dieser Widerstandselemente weisen Verlängerungen 11, 12 auf. Zwischen den beiden Verlängerungen 11 und 12 der beiden Elektroden 1, 2 ist jeweils mit Hilfe zweier federnder Kontaktelemente 13 ein Widerstand 14 elastisch federnd eingespannt. Dieser Widerstand kann lineares Spannungsverhalten aufweisen ist aber mit Vorteil ein nichtlinearer, spannungsabhängiger Widerstand, etwa auf der Basis von Metalloxid.FIG. 4 shows a current limiter which can be used for nominal voltages up to 1.5 kV, in which three resistance elements 10 which are designed in accordance with the above embodiments and are connected to one another in series are used. Instead of three resistance elements 10, only two or possibly four or more resistance elements can also be used. The electrodes 1, 2 of these resistance elements have extensions 11, 12. Between the two extensions 11 and 12 of the two electrodes 1, 2, a resistor 14 is clamped elastically resiliently with the aid of two resilient contact elements 13. This resistor can have linear voltage behavior, but is advantageously a non-linear, voltage-dependent resistor, for example based on metal oxide.

Die beiden Elektroden 1, 2, der Widerstandskörper 3, der parallel dazu geschaltete Widerstand 14 und die beiden federnden Kontaktelemente 13 bilden ein strombegrenzendes, spannungsgesteuertes Bauelement 15 des Strombegrenzers, welches für Nennspannungen bis höchstens 500V verwendet werden kann. Bei der in Fig.4 angegebenen Serienschaltung von drei solchen Bauelementen können Nennspannungen von bis zu 1,5 kV an den Strombegrenzer angelegt werden. Zwischen den Elektroden 1, 2 aufeinanderfolgender Bauelemente 15 sind im Bereich der Widerstandskörper 3 Federelemente 16 vorgesehen, welche die Elektroden 1, 2 mit Druckkraft beaufschlagen und so bei Raumtemperatur einen sicheren Strompfad für den Nennstrom I gewährleisten. Die Widerstandskörper 3 sind in einem Isolierstoffgehäuse 17 untergebracht. Die Verlängerungen 11, 12 der Elektroden 1, 2 sind durch die Wand des Isolierstoffgehäuses 17 geführt und halten die Widerstände 14 außerhalb das Gehäuses. Ein Randabschluß der Widerstandskörper 3 aus isolierendem Material ist mit dem Bezugszeichen 18 gekennzeichnet.The two electrodes 1, 2, the resistance body 3, the resistor 14 connected in parallel therewith and the two resilient contact elements 13 form a current-limiting, voltage-controlled component 15 of the current limiter which can be used for nominal voltages up to a maximum of 500V. With the series connection of three such components shown in FIG. 4, nominal voltages of up to 1.5 kV can be applied to the current limiter. Between the electrodes 1, 2 of successive components 15, spring elements 16 are provided in the area of the resistance bodies 3, which act on the electrodes 1, 2 with compressive force and thus ensure a safe current path for the nominal current I at room temperature. The resistance bodies 3 are accommodated in an insulating material housing 17. The extensions 11, 12 of the electrodes 1, 2 are guided through the wall of the insulating housing 17 and hold the resistors 14 outside the housing. An edge termination of the resistance body 3 made of insulating material is identified by the reference symbol 18.

Bei diesem Strombegrenzer fliesst der Strom zunächst in einem von der Verlängerung 11 der oberen Elektrode 1, einer Serienschaltung der drei Widerstandselemente 10 und der Verlängerung 12 der unteren Elektrode 2 gebildeten Strompfad. Beim Auftreten eines Kurzschlußstroms schaltet eines der Widerstandselemente 10 zuerst. An diesem und an dem parallelgeschalteten Widerstand 14 liegt dann die volle Systemspannung von 1,5 kV an. Der Widerstand 14 sind so bemessen, daß er bei dieser Spannung stromleitend wird, die hohe Spannung über dem Widerstandselement 10 abbaut und dieses so vor Zerstörung schützt. Nun kann ein weiteres der beiden anderen Widerstandselemente 10 schalten. Die Spannung ist jetzt über zwei der drei Widerstandselemente 10 verteilt. Bei geeigneter Bemessung der Widerstandselemente 10 ist eine Überbeanspruchung der beiden durchgeschalteten Widerstandselemente durch die nur vorübergehend voll wirksame Systemspannung nicht zu befürchten. Der nun mit verminderter Spannung beanspruchte Widerstand 14 geht in den nichtleitenden Zustand über. Der Strombegrenzer schaltet nun den Kurzschlußstrom endgültig ab.In this current limiter, the current initially flows in a current path formed by the extension 11 of the upper electrode 1, a series connection of the three resistance elements 10 and the extension 12 of the lower electrode 2. When a short-circuit current occurs, one of the resistance elements 10 switches first. The full system voltage of 1.5 kV is then present at this resistor and at the resistor 14 connected in parallel. The resistor 14 are dimensioned such that it becomes current-conducting at this voltage, the high voltage across the resistor element 10 is reduced and this protects it from destruction. Another of the two other resistance elements 10 can now switch. The voltage is now distributed over two of the three resistance elements 10. With a suitable dimensioning of the resistance elements 10, the two connected resistance elements cannot be overstressed by the system voltage, which is only temporarily fully effective fear. Resistor 14, now loaded with reduced voltage, changes to the non-conductive state. The current limiter now finally switches off the short-circuit current.

Bei der Strombegrenzung aus den Widerstandselementen 10 ausgestoßene und insbesondere Ruß enthaltende Teilchen werden durch das Isolierstoffgehäuse 17 und/oder durch den gegebenenfalls vorgesehene Randabschluß 18 von den nichtlinearen, spannungsabhängigen Widerstandselementen 14 ferngehalten.When the current is limited, particles expelled from the resistance elements 10 and in particular contain soot are kept away from the non-linear, voltage-dependent resistance elements 14 by the insulating material housing 17 and / or by the edge closure 18 which may be provided.

Eine besonders raumsparende Ausbildung des Strombegrenzers wird erreicht, wenn die Widerstände 14 treppenartig um beispielsweise 90° und 180° gegeneinander verdreht angeordnet sind. Bei geeigneter Ausbildung der Elektroden 1, 2 und der Zwischenisolation können die strombegrenzenden Widerstandselemente 10 und die Widerstände 14 auch übereinander angeordnet werden. Der Strombegrenzer weist dann eine besonders leicht handhabbare, säulenförmige Struktur auf.A particularly space-saving design of the current limiter is achieved if the resistors 14 are arranged in a step-like manner, for example rotated by 90 ° and 180 ° relative to one another. With a suitable design of the electrodes 1, 2 and the intermediate insulation, the current-limiting resistance elements 10 and the resistors 14 can also be arranged one above the other. The current limiter then has a particularly easy to handle, columnar structure.

BEZUGSZEICHENLISTEREFERENCE SIGN LIST

1, 21, 2
ElektrodenElectrodes
33rd
WiderstandskörperResistance body
4, 54, 5
Schichtenlayers
66
UnterbrechungenInterruptions
77
BereicheAreas
88th
KühlrippenCooling fins
99
ZwischenschichtIntermediate layer
1010th
WiderstandselementeResistance elements
11, 1211, 12
VerlängerungenExtensions
1313
KontaktelementeContact elements
1414
WiderständeResistances
1515
BauelementeComponents
1616
FederelementeSpring elements
1717th
IsolierstoffgehäuseInsulating housing
1818th
RandabschlußEdging
41, 5141, 51
GrenzflächenInterfaces

Claims (14)

Strombegrenzendes Widerstandselement (1) mit einem zwischen zwei planparallelen, druckbeaufschlagten Elektroden (1, 2) angeordneten, PTC-Verhalten aufweisenden Widerstandskörper (3) aus mindestens einer Polymermatrix und mindestens einer in die Polymermatrix eingebetteten ersten Füllstoffkomponente aus elektrisch leitenden Teilchen, bei dem sich der spezifische Widerstand des Widerstandskörpers (3) beim Auftreten eines Kurzschlußstroms zumindest in einer auf einer ersten (1) der beiden Elektroden (1, 2) aufliegenden Oberflächenschicht oberhalb eines Temperaturgrenzwertes sprunghaft erhöht, dadurch gekennzeichnet, daß der Widerstandskörper (3) vollständig oder zumindest in einer parallel zur Oberflächenschicht erstreckten und den größten Teil seines Volumens einnehmenden Zone eine in die Polymermatrix eingebettete zweite Füllstoffkomponente aufweist, welche so ausgewählt ist, daß ein Polymermatrix, zweite Füllstoffkomponente sowie gegebenenfalls auch erste Füllstoffkomponente enthaltender Verbundwerkstoff PTC-Verhalten aufweist mit einem gegenüber der Oberflächenschicht um mindestens eine Größenordnung höheren Sprungverhalten und dieser Verbundwerkstoff zugleich einen um mindestens eine Größenordnung geringeren spezifischen Widerstand besitzt als ein von der Polymermatrix und der ersten Füllstoffkomponente gebildeter Vergleichsverbundwerkstoff.Current-limiting resistance element (1) with a resistance body (3), arranged between two plane-parallel, pressurized electrodes (1, 2) and having PTC behavior, made of at least one polymer matrix and at least one first filler component made of electrically conductive particles embedded in the polymer matrix, in which the specific resistance of the resistance body (3) when a short-circuit current occurs at least in a surface layer lying on a first (1) of the two electrodes (1, 2) abruptly above a temperature limit, characterized in that the resistance body (3) completely or at least in one extending parallel to the surface layer and occupying most of its volume has a second filler component embedded in the polymer matrix, which is selected so that a polymer matrix, second filler component and optionally also first filler component Component containing PTC behavior has a jump behavior that is at least one order of magnitude higher than the surface layer and this composite material also has at least an order of magnitude lower specific resistance than a comparative composite material formed by the polymer matrix and the first filler component. Widerstandselement nach Anspruch 1, dadurch gekennzeichnet, daß erste und zweite Füllstoffkomponente gleichmäßig in der Polymermatrix verteilt sind.Resistance element according to claim 1, characterized in that the first and second filler components are evenly distributed in the polymer matrix. Widerstandselement nach Anspruch 1, dadurch gekennzeichnet, daß die Konzentration der zweiten Füllstoffkomponente in der Polymermatrix von der Mitte des Widerstandskörpers (3) zur ersten Elektrode (1) hin abnimmt.Resistance element according to claim 1, characterized in that the concentration of the second filler component in the polymer matrix decreases from the center of the resistance body (3) to the first electrode (1). Widerstandselement nach einem der Ansprüche 2 oder 3, dadurch gekennzeichnet, daß die mittlere Größe von Teilchen der ersten Füllstoffkomponente um mindestens eine Größenordnung kleiner ist als die mittlere Größe von Teilchen der zweiten Füllstoffkomponente.Resistance element according to one of claims 2 or 3, characterized in that the average size of particles of the first filler component is at least one order of magnitude smaller than the average size of particles of the second filler component. Widerstandselement nach Anspruch 1, dadurch gekennzeichnet, daß der Widerstandskörper (3) mindestens zwei parallel zu den Elektroden verlaufende Schichten (4) unterschiedlicher elektrischer Leitfähigkeit aufweist, von denen eine erste (4) beider Schichten mit der ersten Elektrode (1) kontaktiert ist, und von denen eine zweite beider Schichten einen geringeren spezifischen Widerstand als die erste Schicht (4) aufweist und mit der ersten Schicht (4) und auf der entgegengesetzt angeordneten Seite entweder mit einer zweiten (2) beider Elektroden (1, 2) oder mit einer mit der ersten Schicht (4) vergleichbaren dritten Schicht (5) kontaktiert ist.Resistance element according to Claim 1, characterized in that the resistance body (3) has at least two layers (4) of different electrical conductivity running parallel to the electrodes, of which a first (4) of both layers is in contact with the first electrode (1), and of which a second of both layers has a lower specific resistance than the first layer (4) and with the first layer (4) and on the opposite side either with a second (2) of both electrodes (1, 2) or with one the first layer (4) comparable third layer (5) is contacted. Widerstandselement nach Anspruch 5, dadurch gekennzeichnet, daß die erste (4) und die gegebenenfalls vorgesehene dritte Schicht (5) ein von erster Füllstoffkomponente und Polymermatrix oder von einem Gemisch aus erster und zweiter Füllstoffkomponente und Polymermatrix gebildeter Verbundwerkstoff ist.Resistance element according to Claim 5, characterized in that the first (4) and the optionally provided third layer (5) is a composite material formed by the first filler component and polymer matrix or by a mixture of the first and second filler components and polymer matrix. Widerstandselement nach einem der Ansprüche 5 oder 6, dadurch gekennzeichnet, daß eine von erster (4) und zweiter Schicht sowie von zweiter und gegebenenfalls vorgesehener dritter Schicht (5) gebildete Grenzschicht (41, 51) ein Metallgitter und/oder eine flächige Metallisierung enthält.Resistance element according to one of claims 5 or 6, characterized in that a boundary layer (41, 51) formed by the first (4) and second layer and by the second and optionally provided third layer (5) contains a metal grid and / or a flat metallization. Widerstandselement nach Anspruch 7, dadurch gekennzeichnet, daß die erste (4) und die gegebenenfalls vorgesehene dritte Schicht (5) von der zweiten Schicht ausgefüllte Unterbrechungen aufweist.Resistance element according to Claim 7, characterized in that the first (4) and the optionally provided third layer (5) have interruptions filled by the second layer. Widerstandselement nach einem der Ansprüche 1 bis 8, dadurch gekennzeichnet, daß mindestens eine der beiden Elektroden (1, 2) mit einem Kühlkörper (Kühlrippen 8) verbunden ist.Resistance element according to one of claims 1 to 8, characterized in that at least one of the two electrodes (1, 2) is connected to a heat sink (cooling fins 8). Widerstandselement nach Anspruch 9, dadurch gekennzeichnet, daß zwischen Elektrode (1, 2) und Kühlkörper (8) eine elektrisch isolierende Zwischenschicht (9) mit hoher thermischer Leitfähigkeit angeordnet ist.Resistor element according to Claim 9, characterized in that an electrically insulating intermediate layer (9) with high thermal conductivity is arranged between the electrode (1, 2) and the heat sink (8). Widerstandselement nach einem der Ansprüche 1 bis 10, dadurch gekennzeichnet, daß die Polymermatrix ein Thermoplast, wie insbesondere Polyäthylen, die erste Füllstoffkomponente Kohlenstoff und die zweite Füllstoffkomponente Titandiborid enthält.Resistance element according to one of claims 1 to 10, characterized in that the polymer matrix contains a thermoplastic, such as in particular polyethylene, the first filler component carbon and the second filler component titanium diboride. Verwendung des Widerstandselementes nach Anspruch 1 in einem Strombegrenzer mit mindestens einem Bauelement (15), welches das Widerstandselement (10) und einen parallel dazu geschalteten, vorzugsweise nichtlinearen, spannungsabhängigen, Widerstand (14) enthält, dadurch gekennzeichnet, daß mindestens zwei in Serie geschaltete Bauelemente (14) vorgesehen sind.Use of the resistance element according to claim 1 in a current limiter with at least one component (15), which contains the resistance element (10) and a parallel, preferably non-linear, voltage-dependent resistor (14), characterized in that at least two components connected in series (14) are provided. Verwendung nach Anspruch 12, dadurch gekennzeichnet, daß zwischen den Widerstandkörpern (3) und den Widerständen (14) die Wand eines die Widerstandselemente (10) oder die Widerstände (14) einschließenden Isolierstoffgehäuses (17) angeordnet ist.Use according to Claim 12, characterized in that the wall of an insulating material housing (17) enclosing the resistance elements (10) or the resistors (14) is arranged between the resistance bodies (3) and the resistors (14). Verwendung nach Anspruch 13, dadurch gekennzeichnet, daß die Elektroden (1, 2) der Widerstandselemente (10) durch die Wand des Isolierstoffgehäuses (17) geführt sind.Use according to claim 13, characterized in that the electrodes (1, 2) of the resistance elements (10) are guided through the wall of the insulating material housing (17).
EP93113545A 1993-08-25 1993-08-25 Electrical resistor and application of this resistor in a current limiter Expired - Lifetime EP0640995B1 (en)

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EP93113545A EP0640995B1 (en) 1993-08-25 1993-08-25 Electrical resistor and application of this resistor in a current limiter
US08/291,903 US5602520A (en) 1993-08-25 1994-08-18 Electrical resistance element and use of this resistance element in a current limiter
CA002130622A CA2130622A1 (en) 1993-08-25 1994-08-22 Electrical resistance element and use of this resistance element in a current limiter
JP6199857A JPH07153604A (en) 1993-08-25 1994-08-24 Electric resistance element and use of this resistance element in current limiter

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DE59306823D1 (en) 1997-07-31
EP0640995B1 (en) 1997-06-25
US5602520A (en) 1997-02-11
CA2130622A1 (en) 1995-02-26
JPH07153604A (en) 1995-06-16

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