EP0979520A2 - Limiteur de courant - Google Patents

Limiteur de courant

Info

Publication number
EP0979520A2
EP0979520A2 EP98904479A EP98904479A EP0979520A2 EP 0979520 A2 EP0979520 A2 EP 0979520A2 EP 98904479 A EP98904479 A EP 98904479A EP 98904479 A EP98904479 A EP 98904479A EP 0979520 A2 EP0979520 A2 EP 0979520A2
Authority
EP
European Patent Office
Prior art keywords
polymer
electrode
current limiter
flat
limiter according
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP98904479A
Other languages
German (de)
English (en)
Inventor
Maria Bijlenga
Lars Banghammar
Ola Jeppsson
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
ABB AB
ABB Research Ltd Sweden
Original Assignee
ABB Research Ltd Switzerland
Asea Brown Boveri AB
ABB Research Ltd Sweden
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by ABB Research Ltd Switzerland, Asea Brown Boveri AB, ABB Research Ltd Sweden filed Critical ABB Research Ltd Switzerland
Publication of EP0979520A2 publication Critical patent/EP0979520A2/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • 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

Definitions

  • the present invention relates to a current limiter for use in an electric device or installation.
  • the current limiter comprises an electrically conducting polymer-based body and electrodes for electrical connection of the body.
  • the body is in free contact with at least one electrode.
  • a current limiter comprising a polymer-based thermistor with positive temperature coefficient, a PTC element, and two electrodes for connection of the PTC element, is known from European patent document EP 0 487 920.
  • At least one of the contact surfaces of the polymer body is in free contact with one of the electrodes.
  • the fact that the body is in free contact with an electrode means in this patent application that the body is not fixedly connected to the electrode by welding, soldering, fusion, chemical or physical bonding, etc . , but that the electrode and the body are retained by and electrical contact is ensured by means of a clamping force which is applied by external pressure-applying means.
  • this is designated in such a way that the body is in free contact with the electrode whereas a body which is secured to an electrode by welding, soldering, fusion, chemical or physical bonding, etc., is designated as being secured to the electrode.
  • the polymer body and the electrodes are retained by resilient and pressure-applying means .
  • This results in a contact pressure in a contact surface where the polymer body is in free contact with an electrode. Since current transition between electrode and polymer body only takes place at certain contact points, a current displacement occurs at the contact surface, which results in a voltage drop close to the contact surface. By the difference in resistivity between the polymer body and the electrode, this voltage drop occurs substantially in the body which has the highest resistivity, that is, the polymer body.
  • a low contact resistance is maintained in a contact surface by the contact pressure which is applied by the pressure-applying devices, which ensures a current transition at a sufficient number of contact points.
  • the temperature at the contact surface is raised. This increase in temperature results in a local melting and/or gasification of the polymer material at certain of the contact points, whereby the resistance is further increased. Finally, a layer of gasified polymer/carbon arises near a contacting contact surface which is in free contact, whereby a strong increase of the resistance across the layer is obtained, that is, the current limiter trips. Since the contact pressure during a trip is maintained by the pressure- applying devices, the original contact and the original contact resistance are essentially restored across the mentioned contact surface in connection with the gas pressure decreasing.
  • the international patent document WO 96/25783 describes a current limiter of the above-mentioned kind, in which one of the contact surfaces of the polymer body makes contact with an electrode, that is, the voltage drop close to and above the contact surface between the electrode and the polymer body has been minimized.
  • the polymer body is contacted in that it is arranged with a low resistance surface layer close to ' the electrode.
  • This low resistance surface layer has an increased electrical conductivity relative to the bulk of the polymer body.
  • a contacted contact surface may be in free contact with or be secured to an electrode.
  • a surface which is connected to or is in free contact with an electrode and for which the voltage drop close to and above the contact surface between the electrode and the polymer body has been minimized is referred to hereinafter in this application as being contacted.
  • the object of the invention is to suggest a current limiter which has a simple electrical and mechanical construction with few parts, comprising an electrically conducting polymer body and electrodes for connection to an electric circuit. For its rated current, the current limiter has small dimensions and a reliable electrical insulation. Especially the risk of flashover and external creeping currents between the electrodes has been essentially eliminated. This has been achieved with a current limiter which still exhibits - low resistance at current intensities below rated current and
  • a current limiter comprising electrodes and at least one electrically conducting polymer-based body
  • this is achieved by at least one electrode being embedded in the polymer-based electrically conducting body and by one or more of the contact surfaces of the body being in free contact with at least one external electrode.
  • the embedded electrode is preferably secured to the polymer body and fixed to the polymer body while at the same time pressure-applying resilient devices retain the parts included in the current limiter.
  • several of the external contact surfaces of the electrically conducting polymer body are adapted to be in free contact with a plurality of external electrodes.
  • the external electrodes are electrically connected to one another and electrically separated from the embedded electrode by the electrically conducting polymer-based body.
  • the retaining and pressure-exerting members retain the parts included in the current limiter while at the same time achieving a contact pressure, acting in the contacting contact surfaces being in free contact, which is essentially directed in the normal direction of these surfaces.
  • the electrically conducting polymer body is contacted close to the embedded electrode, that is, the voltage drop across and close to the contact surface has been minimized for the embedded electrode.
  • the polymer body has been arranged with low resistance layers or zones adjacent to this contact surface.
  • the shape of the electrode may also been chosen on the basis of the criterion to ensure a large effective contact surface between the embedded electrode and the polymer body.
  • effective contact surface is meant in this application the actual surface in which current transition between electrode and polymer body takes place.
  • Commonly occurring shapes of the embedded electrode are a plate, a net or a web, a plurality of electrically and mechanically inter- connected needles or pins which are preferably contacted by means of low resistance layers or zones close to the contact surface.
  • An enlargement of the contact surface for reduced current displacement and improved contacting may also be obtained with open structures or a large area/volume ratio of the electrode, such as wire gauge electrodes, pins and the surface structure of the electrode.
  • These shapes which are based on an enlarged contact surface presuppose that the polymer-based material penetrates into the open structure of the electrode and is bonded to the electrode with good adhesion.
  • measures must be taken to avoid gas or air pockets as well as precipitations in or adjacent the contact surface since the occurrence of such inhomogeneities disturb the current transition or creates current displace- ment.
  • a flat current limiter with an embedded electrode comprises, according to one embodiment, a flat metal electrode of copper, nickel or an alloy based on any of these metals.
  • the electrode is preferably wholly or partially coated with a surface layer of an alloy, which has very good conductivity, such as a layer of silver or a silver-based alloy.
  • the electrode has been embedded into a polymer body by placing two polymer-based electrically con- ducting plates, which are wider and longer than the electrode, on either side of the flat electrodes. Those parts of the major surfaces of the polymer plates which are in contact with the electrode are arranged with a surface layer or surface zones with reduced resistivity, for example a layer of the silver alloy mentioned above, or a polymer-based coating containing silver.
  • the polymer plates and the electrode have then been compressed under heating. During the compression, the edges of the polymer plates have been welded together such that the electrode has been embedded into and essentially surrounded by the flat polymer body formed, while at the same time the polymer body has been caused to make contact with the electrode.
  • the embedded electrode may be connected to an insulated conductor or by the fact that part of the embedded electrode has been left open and uninsulated for connection. Electrodes have then been adapted to be in free contact with the major surfaces of the flat polymer body obtained.
  • a flat current limiter with an embedded metal electrode may be manufactured by extruding an electrically conducting polymer composition around a metal band.
  • the strip obtained comprises a metallic strip surrounded by two polymer layers and has then been cut in suitable lengths into flat polymer bodies.
  • the embedded electrode may be connected to an insulated conductor or by leaving part of the embedded electrode open and uninsulated for connection.
  • the major surfaces of the body have been arranged to be in free contact with external electrodes. In certain embodiments, only one of the major surfaces is in free contact with an electrode whereas the other major surface is electrically insulated.
  • the embedded electrode is metallic but in alternative embodiments it is polymer-based with a reduced resistivity relative to the PTC element.
  • Preferred metallic electrodes are silver, copper, nickel or alloys based on any of these metals. Copper- or nickel-based electrodes are often coated with a low-resistance chemically resistant silver alloy.
  • a polymer-based electrode comprises a conducting polymer or an electrically conducting polymer composition, an electrically conducting plastic, based on a polymer such as a thermoplastic resin, an elastomer or a thermosetting resin to which an electrically conducting powdered material has been added.
  • powder additive there is preferably chosen a metallic powdered material based on a metal with good electrical conductivity such as silver, gold, copper, nickel or aluminium.
  • a metallic powdered material based on a metal with good electrical conductivity such as silver, gold, copper, nickel or aluminium.
  • Other feasible powdered materials are soot, carbon black and other graphite-based materials, ceramic powders based on, for example, borides such as titanium diboride, zirconium dibo- ride, carbides such as tantalum carbide, silicon carbide, tungsten carbide, zirconium carbide, nitrides such as zir- conium nitride, titanium nitride, oxides such as vanadium trioxide, titanium oxide, or mixtures of two or more of these powders.
  • the polymer-based electrode has a reduced resistivity in relation to the polymer-based body.
  • the polymer-based electrically conducting body and the polymer- based electrode have been jointly extruded.
  • the jointly extruded polymer-based electrode is preferably chemically bonded to the polymer-based electrically conducting body and has a reduced resistivity in relation to the electrically conducting polymer-based body.
  • the two electrically conducting polymer compositions have been jointly extruded into a layered strip, whereby the polymer composition which has the lowest resistivity is surrounded by the polymer composition which has a higher resistivity. After the extrusion, the extruded strip has been cut into suitable lengths.
  • the electrode exposed in the cutting surfaces during the cutting has then been coated such that the electrodes have been surrounded essentially completely.
  • the embedded electrode may be connected to an insulated conductor or by leaving part of the embedded electrode open and uninsulated for connection.
  • the major surfaces of the body have been adapted to be in free contact with external electrodes. In certain embodiments, only one of the major surfaces is in free contact with an electrode whereas the other major surface is electrically insulated.
  • an electrically conducting polymer body with a polymer-based electrode has been formed by simultaneous injection moulding of two electrically conducting polymer-based materials . The material which has the lowest resistivity has been arranged as an embedded electrode surrounded by the other polymer material which has a higher resistivity. The obtained polymer body with the embedded electrode is then adapted to be in free contact with at least one external electrode.
  • a current limiter according to the embodiments of the invention described in the foregoing is simple, compact and has a reliable electrical insulation while at the same time it still exhibits a high withstand strength in relation to overcurrents which are of the order of magnitude of 10 times the nominal current or less and a rapid and very reliable current limitation in case of short-circuit currents .
  • a device according to the invention provides a possibility of predicting where tripping occurs. In this way, constructive measures may be taken to further reduce the resistance across the electrically conducting body, increase the withstand strength against brief and limited overcurrents and improve the ability to rapidly and reliably limit short- circuit currents.
  • Examples of such measures are to arrange the external electrodes with means for absorbing heat which is generated in the polymer-based electrically conducting body close to these and/or means for emitting the heat which is absorbed by the electrodes.
  • the electrodes are arranged as heat-absorbing and/or heat-emitting bodies such as cooling bodies of aluminium with or without cooling flanges.
  • the electrodes are arranged in thermal contact with such cooling bodies.
  • the embodiment of the invention shown in Figures la, lb and lc comprises a polymer-based electrically conducting body in the form of a plate 10 with an electrode 13 embedded in the body and external electrodes 11, 12 with which the two major surfaces 100', 100" of the plate are in free contact.
  • the figures show and describe an embodiment with two electrodes, but of course one of the electrodes may be replaced by an electrically conducting disc or an electrically insulating coating, or, alternatively, additional electrodes be arranged.
  • the electrodes 11, 12 are flat bodies .
  • a flat body or a plate is meant in this patent application a body, the thickness of which is essentially smaller than its length and width.
  • the plates included in the current limiter are retained in the embodiment according to the figures by one or more elastically resilient elements 14, 15 which engage the flat body 10 of the current limiter and the electrodes 11, 12, 13 and retain them by applying a resilient clamping force to act in the major surfaces 100', 100" essentially perpendicularly to the plane of the flat bodies.
  • the polymer-based plate 10 is preferably an electrically conducting resin based on a polymer such as a thermoplastic resin, an elastomer or a thermosetting resin, to which an electrically conducting powdered material has been added.
  • a polymer such as a thermoplastic resin, an elastomer or a thermosetting resin
  • powder additive there is preferably chosen carbon, carbon black or another carbon-based electrically conducting powder.
  • a metallic powdered material based on a metal with good electrical conductivity such as silver, gold, copper, nickel or aluminium
  • ceramic powders based on, for example, borides such as titanium diboride, zirconium diboride, carbides such as tantalum carbide, silicon carbide, tungsten carbide, zirconium carbide, nitrides such as zirconium nitride, titanium nitride, oxides such as vanadium trioxide, titanium oxide, or mixtures of two or more of these powders.
  • borides such as titanium diboride, zirconium diboride, carbides such as tantalum carbide, silicon carbide, tungsten carbide, zirconium carbide, nitrides such as zirconium nitride, titanium nitride, oxides such as vanadium trioxide, titanium oxide, or mixtures of two or more of these powders.
  • borides such as titanium diboride, zirconium diboride,
  • the embedded electrode 13 is shown in the figures as a plate, which is centrally arranged in the bulk of the polymer-based electrically conducting plate 10 and oriented in a plane which is essentially parallel to the external electrodes 11, 12 and the major surfaces 100', 100" of the polymer plate 10.
  • the embedded electrode 13 is preferably a metallic plate, for example a silver, copper or nickel plate.
  • the polymer-based body is arranged with low-resistance and chemically resistant layers or zones close to the embedded electrode.
  • the embedded electrode 13 shown in the figures is a plate, the shape may be arbitrary with an expressed ambition to raise the effective contact surface between the embedded electrode 13 and the polymer body 10 through the shape of the elec- trode .
  • Electrode shapes by which a large contact surface is achieved are nettings, webs, interconnected needles or pins, perforated plates, plates with a modular surface structure. It is also important that measures be taken such that no air or gas pockets remain at the boundary between embedded electrode and polymer bulk, 13/10. Likewise, precipitations in or close to this boundary must be avoided. Gas pockets, gas-filled pores as well as precipitations reduce the effective contact surface and hence raise the contact resistance.
  • metallic electrodes, plates, webs, etc. of graphite or other electrically conducting unorganic materials may be used as well as electrically conducting polymer-based materials with a resistivity lower than the polymer-based body 10.
  • Polymer-based electrodes may comprise electrically conducting polymers with an intrinsic electrical conductivity or electrically conducting resins which have received their electrical conductivity through electrically conducting particular fillers .

Landscapes

  • Engineering & Computer Science (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Chemical & Material Sciences (AREA)
  • Dispersion Chemistry (AREA)
  • Ceramic Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Thermistors And Varistors (AREA)
  • Secondary Cells (AREA)
  • Emergency Protection Circuit Devices (AREA)

Abstract

L'invention concerne un limiteur de courant comprenant des électrodes (11, 12, 13) et au moins un corps (10) à base de polymère et électriquement conducteur, doté d'au moins une surface de contact (100', 100'') extérieure. Une électrode (13) est insérée dans le corps (10) à base de polymère et le corps à base de polymère est appliqué avec ses surfaces de contact extérieures librement contre au moins une électrode (11, 12).
EP98904479A 1997-02-17 1998-02-12 Limiteur de courant Withdrawn EP0979520A2 (fr)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
SE9700537 1997-02-17
SE9700537A SE511234C2 (sv) 1997-02-17 1997-02-17 Strömbegränsare
PCT/SE1998/000237 WO1998036427A2 (fr) 1997-02-17 1998-02-12 Limiteur de courant

Publications (1)

Publication Number Publication Date
EP0979520A2 true EP0979520A2 (fr) 2000-02-16

Family

ID=20405809

Family Applications (1)

Application Number Title Priority Date Filing Date
EP98904479A Withdrawn EP0979520A2 (fr) 1997-02-17 1998-02-12 Limiteur de courant

Country Status (4)

Country Link
EP (1) EP0979520A2 (fr)
AU (1) AU6233898A (fr)
SE (1) SE511234C2 (fr)
WO (1) WO1998036427A2 (fr)

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4685025A (en) * 1985-03-14 1987-08-04 Raychem Corporation Conductive polymer circuit protection devices having improved electrodes
SE515262C2 (sv) * 1995-02-16 2001-07-09 Abb Research Ltd Anordning för strömbegränsning och skydd mot kortslutningsströmmar i en elektrisk anläggning

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO9836427A3 *

Also Published As

Publication number Publication date
WO1998036427A3 (fr) 1998-10-15
SE511234C2 (sv) 1999-08-30
AU6233898A (en) 1998-09-08
SE9700537L (sv) 1998-08-18
WO1998036427A2 (fr) 1998-08-20
SE9700537D0 (sv) 1997-02-17

Similar Documents

Publication Publication Date Title
CA1331399C (fr) Ensemble de dispositifs de protection pour elements de circuit a coefficient de temperature positif
US4780598A (en) Composite circuit protection devices
EP1911047B1 (fr) Dispositif de protection de circuit ayant en couplage thermique un element de surtension mov et un element de surintensite pptc
CA2054487C (fr) Element a coefficient de temperature positif
US5414403A (en) Current-limiting component
US6074576A (en) Conductive polymer materials for high voltage PTC devices
EP0826223A1 (fr) Dispositif de protection pourvu d'un circuit a coefficient de temperature positif et procede de fabrication correspondant
WO1990003713A1 (fr) Dispositif chauffant flexible comprenant un polymere conducteur
US6388553B1 (en) Conductive polymer current-limiting fuse
EP2133973B1 (fr) Dispositif de protection de circuit
US5896264A (en) Device for current limitation and protection against short-circuit currents in an electric installation
US6862164B2 (en) Circuit protection arrangement
US5793278A (en) Limiter for current limiting
US20020125982A1 (en) Surface mount electrical device with multiple ptc elements
US5861795A (en) Current-limiting resistor having PTC behavior
EP0607269A1 (fr) Dispositif de protection contre la surcharge et les courts-circuits dans des installations electriques
EP0591348B1 (fr) Dispositifs de protection de circuits
WO1998036427A2 (fr) Limiteur de courant
CN109637762B (zh) 具有混合的导电填料组成的pptc材料
AU772381B2 (en) An electrical device comprising a PTC polymer element for overcurrent fault and short-circuit current fault protection
TWI690110B (zh) 複合式保護元件以及電池組
EP1126478A1 (fr) Dispositif a coefficient de temperature positif et son procede de fabrication
JP3815026B2 (ja) 限流器
JP3828238B2 (ja) 限流器
JP3829692B2 (ja) 限流器

Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

17P Request for examination filed

Effective date: 19990910

AK Designated contracting states

Kind code of ref document: A2

Designated state(s): CH DE FR GB IT LI SE

RAP1 Party data changed (applicant data changed or rights of an application transferred)

Owner name: ABB AB

Owner name: ABB RESEARCH LTD.

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: THE APPLICATION IS DEEMED TO BE WITHDRAWN

18D Application deemed to be withdrawn

Effective date: 20020903