EP0494507A1 - Hochenergie-Zinkoxid-Varistor - Google Patents

Hochenergie-Zinkoxid-Varistor Download PDF

Info

Publication number
EP0494507A1
EP0494507A1 EP91311317A EP91311317A EP0494507A1 EP 0494507 A1 EP0494507 A1 EP 0494507A1 EP 91311317 A EP91311317 A EP 91311317A EP 91311317 A EP91311317 A EP 91311317A EP 0494507 A1 EP0494507 A1 EP 0494507A1
Authority
EP
European Patent Office
Prior art keywords
disc
varistor
electrodes
zinc oxide
accordance
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.)
Ceased
Application number
EP91311317A
Other languages
English (en)
French (fr)
Inventor
Herman F. Nied
Howard F. Ellis
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.)
Electric Power Research Institute Inc
Original Assignee
Electric Power Research Institute Inc
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 Electric Power Research Institute Inc filed Critical Electric Power Research Institute Inc
Publication of EP0494507A1 publication Critical patent/EP0494507A1/de
Ceased legal-status Critical Current

Links

Images

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
    • H01C7/10—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 voltage responsive, i.e. varistors
    • H01C7/102—Varistor boundary, e.g. surface layers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01C—RESISTORS
    • H01C1/00—Details
    • H01C1/14—Terminals or tapping points or electrodes specially adapted for resistors; Arrangements of terminals or tapping points or electrodes on resistors

Definitions

  • the present invention relates to a disc shaped, zinc oxide-based varistor for high voltage or high current applications, and more particularly relates to improvements in the physical stability thereof.
  • a zinc-oxide-based varistor as typically manufactured, comprises a sintered disc of zinc oxide and additives, the disc having a pair of electrodes on opposite faces. It is also typical for the electrode on the face to only extend part way to the rim of the disc, in order to avoid arcing, also called fringing current or flash over. See, for example, U.S. Patent Numbers 4,460,497 to Tapan K. Gupta et al., 4,451,815 to Eugene Sakshaug et Ano., and 4,450,426. In addition, the rim is usually protected from the elements or some aspect of the manufacturing process by an electric insulator. See, for example, U.S. Patent Numbers 4,371,860 to John E. May et Ano., and 3,138,686 to Steven P. Mitoff et Ano.
  • the interior of the disc may reach a high temperature while the rim remains close to ambient temperature.
  • the situation is exacerbated by the anti-arcing design in which the margin of the face is left bare.
  • the electric field drops suddenly near the rim, as does the temperature, resulting in a thermal shock condition. This may result in physical cracking on the rim, and substantial damage to the device.
  • Figure 1 is a cross sectional view of a prior art zinc oxide varistor.
  • Figure 2 is a perspective view of the prior art zinc oxide varistor shown in Figure 1.
  • Figure 3 is a cross section view of a zinc oxide varistor in accordance with the present invention.
  • Figure 4 is a perspective view of the zinc oxide varistor illustrated in Figure 3.
  • Figure 5 is a cross sectional view of the zinc oxide varistor comprising a second embodiment of the invention.
  • Figure 6 is a drawing illustrating the contours of equal temperature of a typical varistor.
  • Figure 7 is a block diagram illustrating the process for predicting the thermal stability of a varistor disc.
  • FIG. 1 and 2 illustrate the prior art zinc oxide varistor, generally indicated at 10.
  • This varistor comprises a disc of sintered zinc-oxide and additives, the disc having a bulk interior 25 and a cylindrical surface 30 extending between the opposite faces 40 and 41.
  • a pair of electrodes 50 and 51 are affixed to the opposite faces 40 and 41, but extend only part-way to the cylindrical surface 30 in order to avoid arcing.
  • the margin 60 is that part of the face 40 or 41 not covered by the electrodes.
  • the cylindrical surface 30 is generally covered with an insulator (not shown), usually a thin glass coating, to protect it from the elements or some aspect of the manufacturing process.
  • the interior 25 of the disc When the prior art varistor 10 is exposed to high current for a short period of time, the interior 25 of the disc will have a generally uniform electric field.
  • the margin region 60 is narrow and will be subject to a severe electric field gradient.
  • the interior 25 may briefly reach a temperature as high as 160 degrees C. above the ambient temperature.
  • the regions of the disc near the cylindrical surface 30 will remain near ambient temperature since any heat would be rapidly dissipated to the environment. Additionally, this region has a significantly lower current flow. Due to the current gradient and the dissipation characteristics of the disc severe thermal gradients may develop across the disc. These thermal gradients may produce a thermal shock condition, which may result in physical cracking of the disc.
  • FIGs 3 and 4 illustrate a zinc oxide varistor of known composition according to the present invention, generally indicated at 100.
  • the varistor comprises a disc-shaped body 155 of sintered zinc-oxide and additives, the disc having a cylindrical outer surface 130 and opposite faces 140 and 141.
  • a pair of electrodes 150 and 151 are affixed opposite faces 140 and 141 and extend up to the edge of the outer cylindrical surface 130.
  • a collar 160 with high dielectric and high temperature insulating properties is then positioned around the outer cylindrical surface 130.
  • the collar 160 is a high temperature polymer.
  • the collar 160 may be made of polyetherimide (ULTEM) which has a high dielectric strength of 33 KV/mm in air @ 1.6 mm.
  • Polyetherimide is a high temperature polymer which can be used in applications where the temperature goes above 2100 C, well within the range of expected use.
  • Metal coatings 170 and 171 extend across the bottom and top electrodes 150 and 151 and the junction between the polyetherimide collar 160 and the body 155 and may be formed by one of a variety of techniques, such as vacuum metallization, flame/arc spraying. This metal coating effectively forms an extension to the electrodes (150, 151) and produces a more uniform electric field gradient across the disc body 155.
  • the collar 160 is made of porcelain enamel, thermal plastic or a suitable polymer.
  • Polyetherimide has a higher coefficient of expansion than zinc oxide, so if a polyetherimide collar is used, it will fit snugly on the disc 100 upon cooling down, and it will be in a state of tension while slightly compressing the disc 100.
  • Figure 5 illustrates another embodiment 101 of the invention, differing from the embodiment discussed above in that the electrodes 140 and 141 are not extended outwardly beyond the cylindrical surface 130.
  • the interior of the disc When the varistor 100 according to the present invention is exposed to high current or voltage, the interior of the disc will have a generally uniform electric field tending to equalize the current distribution. This is a result of the electrodes extending entirely across the faces of the disc. Problems due to high electric fields in the regions near the outer cylindrical surface are reduced by the high dielectric properties of the collar. This results in more uniform heating of the varistor disc for a given current and dissipation while reducing arcing problems associated with prior electrodes when they extended to or beyond the cylindrical surface.
  • Joule heating is more uniformly distributed throughout the disc, resulting in a lower thermal gradient across the disc. Reducing the thermal gradient reduces susceptibility to physical cracking caused by a thermal shock condition, common in prior art varistors.
  • the present invention further provides a method for determining the energy handling capacity of a particular disc, that is the disc's resistance to cracking, prior to assembly of the varistor. This permits discs having low or unacceptable dissipations to be discarded to improve the quality of finished varistors.
  • FIG. 6 is a drawing illustrating typical curves corresponding to constant temperature patterns, thermometry across the face of a typical varistor disc. In this illustration only three curves, labeled "A”, "B” and “C” are illustrated. However, in most applications more profiles may be used. These profiles are used to predict the stability of the finished varistor, as described below.
  • FIG. 7 is a block diagram illustrating the process used to evaluate the thermal characteristics of a particular varistor disc.
  • Each of the newly manufactured zinc oxide varistor discs 195 is subjected to a low energy pulse. For example, rapid application of 27 kJ energy will increase the average temperature of the varistor by about 60 degrees C.
  • the thermograph is produced using an infrared camera recorder and converted to digital form. This data is analyzed by a digital computer to determine the thermal stress of the varistor disc.
  • the thermal stress analysis involves calculating the thermal stress at various locations on the varistor disc, and especially on and near the outer cylindrical surface, as this is the region of expected maximum stress. All calculations in this thermal stress calculation step are performed directly from the thermal data, previously described. That is they are performed in closed form, and thus need very little computer memory, and numerical results are obtained rapidly.
  • the energy handling capability step compares this data with known physical properties of the material, and determines the maximum energy handling capability of the particular disc. Any disc having a thermal capability lower than the desired value are discarded. This permits varistors of a given capability to be manufactured with a lower disc volume.

Landscapes

  • Engineering & Computer Science (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Thermistors And Varistors (AREA)
EP91311317A 1990-12-12 1991-12-04 Hochenergie-Zinkoxid-Varistor Ceased EP0494507A1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US62630890A 1990-12-12 1990-12-12
US626308 1990-12-12

Publications (1)

Publication Number Publication Date
EP0494507A1 true EP0494507A1 (de) 1992-07-15

Family

ID=24509856

Family Applications (1)

Application Number Title Priority Date Filing Date
EP91311317A Ceased EP0494507A1 (de) 1990-12-12 1991-12-04 Hochenergie-Zinkoxid-Varistor

Country Status (2)

Country Link
EP (1) EP0494507A1 (de)
JP (1) JPH0536504A (de)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2734059A1 (fr) * 1995-05-11 1996-11-15 Hitachi Ltd Procede pour estimer la capacite de decharge d'un element de puissance a base d'oxyde de zinc, procede pour selectionner cet element et systeme pour la mise en oeuvre de ce procede
EP0955644A2 (de) * 1998-05-06 1999-11-10 Abb Research Ltd. Verfahren zum Herstellen eines Varistors auf Basis eines Metalloxids und ein nach diesem Verfahren hergestellter Varistor
WO2015096932A1 (en) * 2013-12-24 2015-07-02 Epcos Ag Method for fabricating a varistor device and varistor device
LU100140B1 (en) * 2017-03-15 2018-09-19 Abb Schweiz Ag Circuit Breaker having Semiconductor Switch Element and Energy Absorbing Device

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3905006A (en) * 1972-12-29 1975-09-09 Michio Matsuoka Voltage dependent resistor
US4692735A (en) * 1984-04-25 1987-09-08 Hitachi, Ltd. Nonlinear voltage dependent resistor and method for manufacturing thereof

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3905006A (en) * 1972-12-29 1975-09-09 Michio Matsuoka Voltage dependent resistor
US4692735A (en) * 1984-04-25 1987-09-08 Hitachi, Ltd. Nonlinear voltage dependent resistor and method for manufacturing thereof

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
PATENT ABSTRACTS OF JAPAN vol. 13, no. 531 (E-851)28 November 1989 & JP-A-1 216 504 ( NGK INSULATORS ) 30 August 1989 *
PATENT ABSTRACTS OF JAPAN vol. 3, no. 159 (E-162)27 December 1979 & JP-A-54 139 095 ( MATSUSHITA ELECTRIC ) 29 October 1979 *

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2734059A1 (fr) * 1995-05-11 1996-11-15 Hitachi Ltd Procede pour estimer la capacite de decharge d'un element de puissance a base d'oxyde de zinc, procede pour selectionner cet element et systeme pour la mise en oeuvre de ce procede
CN1077322C (zh) * 1995-05-11 2002-01-02 株式会社日立制作所 估计氧化锌元件放电容量的方法,筛选元件的方法及系统
EP0955644A2 (de) * 1998-05-06 1999-11-10 Abb Research Ltd. Verfahren zum Herstellen eines Varistors auf Basis eines Metalloxids und ein nach diesem Verfahren hergestellter Varistor
US6199268B1 (en) 1998-05-06 2001-03-13 Abb Research Ltd. Method for producing a varistor based on a metal oxide and a varistor produced using this method
EP0955644A3 (de) * 1998-05-06 2003-12-17 Abb Research Ltd. Verfahren zum Herstellen eines Varistors auf Basis eines Metalloxids und ein nach diesem Verfahren hergestellter Varistor
WO2015096932A1 (en) * 2013-12-24 2015-07-02 Epcos Ag Method for fabricating a varistor device and varistor device
EP4339973A1 (de) * 2013-12-24 2024-03-20 TDK Electronics AG Verfahren zum herstellen eines varistors und ein nach diesem verfahren hergestellter varistor
LU100140B1 (en) * 2017-03-15 2018-09-19 Abb Schweiz Ag Circuit Breaker having Semiconductor Switch Element and Energy Absorbing Device

Also Published As

Publication number Publication date
JPH0536504A (ja) 1993-02-12

Similar Documents

Publication Publication Date Title
Bartkowiak et al. Failure modes and energy absorption capability of ZnO varistors
He et al. Discussions on nonuniformity of energy absorption capabilities of ZnO varistors
US5708555A (en) Surge arrester having controlled multiple current paths
US5264819A (en) High energy zinc oxide varistor
US4571660A (en) Lightning arrester insulator
JP2005348596A (ja) ガス密閉型のサージ・アレスタのための動作部分
Bartkowiak et al. Influence of nonuniformity of ZnO varistors on their energy absorption capability
EP0494507A1 (de) Hochenergie-Zinkoxid-Varistor
Bartkowiak et al. Energy handling capability of ZnO varistors
Saengsirwan et al. Lightning arrester modeling using ATP-EMTP
EP0050735B1 (de) Zinkoxid-Varistor und Verfahren zu seiner Herstellung
US6342828B1 (en) Resistor which is designed in the form of a column and is resistant to high current in particular a varistor on a metal-oxide base, and method for producing such a resistor
Kobayashi et al. Metal oxide surge arrester
Bui et al. Electrical characteristic degradation of ZnO varistors subjected to partial discharges
US2947801A (en) Contamination and moisture resistant insulator
Choi et al. Surge energy capability of ZnO-based varistors according to the Sb2O3 and Bi2O3
Bargigia et al. Comparison of different test methods to assess the thermal stresses of metal oxide surge arresters under pollution conditions
Ohbuchi et al. Characterization of interface states in degraded ZnO varistors
US4409728A (en) Method of making a stable high voltage DC varistor
Kourdi et al. Behaviour of metal-oxide-based varistors subjected to partial discharges in air
Fang et al. Failure Modes and Energy Handling Capability of ZnO Varistors with Different Electrode Edge Margins Stressed by Current Impulses
Bialek Insulation system protection with zinc oxide surge arresters
US5037594A (en) Method for making varistor discs with increased high temperature stability
Kuang et al. Temperature distribution in a ZnO arrester subjected to multiple current impulses
Zhang et al. Statistical investigation on the electrical responses of ZnO-based varistors to different impulse currents

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

AK Designated contracting states

Kind code of ref document: A1

Designated state(s): AT BE CH DE DK ES FR GB GR IT LI LU NL SE

17P Request for examination filed

Effective date: 19921215

17Q First examination report despatched

Effective date: 19940607

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

Free format text: STATUS: THE APPLICATION HAS BEEN REFUSED

18R Application refused

Effective date: 19950911