US3140373A - Arc ionizable beryllium electrodes for vacuum arc devices - Google Patents

Arc ionizable beryllium electrodes for vacuum arc devices Download PDF

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Publication number
US3140373A
US3140373A US168436A US16843662A US3140373A US 3140373 A US3140373 A US 3140373A US 168436 A US168436 A US 168436A US 16843662 A US16843662 A US 16843662A US 3140373 A US3140373 A US 3140373A
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United States
Prior art keywords
arc
vacuum
electrodes
beryllium
devices
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Expired - Lifetime
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US168436A
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English (en)
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Fordyce H Horn
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General Electric Co
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General Electric Co
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Publication date
Priority to DENDAT1251406D priority Critical patent/DE1251406B/de
Application filed by General Electric Co filed Critical General Electric Co
Priority to US168436A priority patent/US3140373A/en
Priority to GB18935/65A priority patent/GB1025944A/en
Priority to GB2683/63A priority patent/GB1025943A/en
Priority to FR922377A priority patent/FR1344824A/fr
Application granted granted Critical
Publication of US3140373A publication Critical patent/US3140373A/en
Priority to SE10547/65A priority patent/SE304326B/xx
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H1/00—Contacts
    • H01H1/02—Contacts characterised by the material thereof
    • H01H1/0203—Contacts characterised by the material thereof specially adapted for vacuum switches

Definitions

  • the present invention relates to vacuum are devices. More particularly, the invention relates to vacuum are devices which exhibit extremely high static breakdown voltages and rapid recovery times.
  • Vacuum arc devices are becoming increasingly more important in the control of high current, high voltage electric energy.
  • One such device is the vacuum switch or vacuum circuit interrupter, which is operative to interrupt currents of thousands of amperes in the kilovolt ranges, and, in the case of an alternating current voltage, to cause extinction thereof upon the occurrence of a first current zero.
  • Devices of this type are set forth and claimed in US. Patents Number 2,975,255--Laiferty and 2,975,256-Lee et al.
  • Lighting arresters and vacuum gaps are vacuum devices with fixed electrodes designed to withstand high electric stress up to a point, but to break down and conduct electricity upon the occurrence of a given overload and to continue conduction until a transient overload has passed or until the occurrence of a next current zero whichever is sooner.
  • Another object of the present invention is to provide vacuum are devices having high static breakdown strength, rapid recovery time and high recovery voltage. Yet another object of the present invention is to provide improved vacuum switches having'rapid recovery times.
  • Still another object of the invention is to provide vacuum gap devices having rapid recovery strength and unusually high static breakdown voltages.
  • vacuum are. devices are provided in the form of evacuable envelopes or chambers capable of maintaining a vacuum of less than millimeters of mercury, which chambers contain a pair of arc electrodes adapted to be the terminal points of 'an electric are carrying an electric curnent.
  • one are electrode is adapted to be movable and to abutt against the other, thus facilitating the interruption of electric currents.
  • both electrodes are fixed and are spaced apart from one another to define a vacuum gap therebetween.
  • the portions of the arc electrodes which serve as terminal points of an electric arc are substanice tially free of occluded and absorbed gasesand comprise beryllium, either in the elemental state or as an alloy with another electrode material, as for example, copper or silver.
  • FIGURE 1 is a vertical cross-sectional view of a representative vacuum circuit interrupter in accord with one embodiment of the invention.
  • FIGURE 2 is a vertical cross-sectional view of a representative vacuum gap device constructed in accord with another embodiment of the present invention.
  • an interrupter chamber 10 comprises a wall member 11 which may be cylindrical in shape and is constructed of a suitable insulating material, having at the ends thereof a pair of metallic end members 12 and 13 enclosing the volume therein to form an interrupter chamber. Suitable shields 14 are provided between casing 11 and end members 12 and 13 to render the interrupter chamber vacuum tight.
  • a pair of separable contacts or electrodes 15 and 16 shown in their closed circuit or engaged position.
  • Upper contact 15 is a stationary contact suitably attached electrically and mechanically to a conducting rod 17 which, at its upper end, is united electrically and mechanically with end member 12.
  • Lower contact 18, mounted upon and electrically united with a suitable conducting rod 18, is movable and is connected through bellows 20 or an equivalent vacuum tight member, permitting reciprocating motion.
  • Termi nal mounting rod 18 projects through a suitable orifice in end member 13, and suitable actuating means may be connected thereto to cause a reciprocating motion of rod 18 to cause contact 16 to enter into engagement with, and to be removed out of engagement from, contacts 15.
  • the electrical circuit which is sought to be interrupted by the interrupter device may be completed by making suitable connections to terminal 21, electrically and mechanically mounted upon end member 12, and terminal 22, electrically and mechanically mounted upon rod 18.
  • a suitable insulator shield such as metallic cylindrical member 23,'capped with anarc preventing ferrule 24, is
  • electrodes 15-16 and insulator 11 interposed between electrodes 15-16 and insulator 11 to prevent the latter from becoming coated with metal and becoming electrically short-circuited.
  • the volume within vacuum interrupter chamber 10' is suitably evacuated through an exhaust tubulation (not shown) during the final assembly thereof.
  • the pressure within chamber 10 must be maintained at a pressure no greater than 10' millimeters of mercury and preferably a pressure less than 10' millimeters of mercury.
  • the foregoing requirement is essential for the operation of the devices as vacuum interrupters of alternating currents. This requirement is necessary because, in order that a currentcarryingarc struck between electrodes 15 and 16 be extinguished at the first occurring current zero. value, there must'be substantially no ionizable gas presentwithin chamber 10.
  • the occurrence of such ionization may be substantially prevented if the possible breakdown paths between electrodes 15 and 16, or their respective supports, are small with respect to the mean free path of an electron within the atmosphere obtained within the device.
  • This mean free path is designated a statistical distance which an electron may travel without colliding with a gas molecule at a given pressure.
  • One type of commercially available vacuum circuit interrupter utilizes contacts of tungsten, molybdenum or other refractory materials which may be baked and otherwiseheat treated for a sufficiently long time and at a sufliciently high temperature to remove all absorbed gases from the vacuum arc. This is necessary because, the vacuum arc is sustained as a conducting column by ionized metallic particles which are boiled from the electrodes, primarily the cathode. During the boiling out process, if any absorbed gases or gas-forming constituents are present within the electrode material, gas is freed and becomes ionized.
  • the ionized metallic vapors within the chamber rapidly cool and migrate back to the electrodes, to the shield, or to the chamber wall, are de-ionized and removed from the chamber, lowering the pressure.
  • This is not, however, the case with ionizable gases which are boiled from the electrodes. Such gases continue to remain in the chamber and raise the pressure thereof. It is for this reason that the electrodes must be purified to such an extent as to cause the presence of gas and gas-forming constituents Within the electrodes to be low enough to allow the maintenance of a vacuum of less than 10* millimeters of mercury pressure within the device.
  • this requirement may be stated in the relationship that the contact material must contain less than 10 atomic parts of all gases or gas-forming constituents. Since arc errosion in accord with the aforementioned test consumes a substantial portion of the contact material, it proves that it provides a satisfactory test for the determination whether the arc electrodes are substantially free of all occluded and absorbed gases, since even infinitesimal presence of such would cause a substantial rise in the presence of the test chamber.
  • Vacuum switches as described above, constructed utilizing refractory type electrodes which may be readily provided in a suflicient gas-free-state suffer from a serious difficulty in that their current chopping characteristic is very bad.
  • Current chopping a term well known to the vacuum circuit interrupter art, is characterized by the instantaneous and premature extinction of the arc prior to the arrival of a current zero upon interruption of an alternating current circuit.
  • Current chopping of an alternating current is shown graphically by the curve of FIG- URE 2, in which sinusoidal current wave A is interrupted at time Ti and the arc chops at time Tc, creating a transient current change Io.
  • This event occurs at some finite value of current and, upon the occurrence thereof, there is a sudden change in the current flowing in the circuit of the order of the chopping current.
  • this transient current change causes high transient voltages which can ruin expensive equipment.
  • a precise chopping current may not be specified for any given material, statistical studies make it possible to determine a current at which the probability of instantaneous and interruption of the alternating current are may occur. This current is generally accepted as the chopping current for any given material. For tungsten and molybdenum chopping currents of the order of 15 amperes are not unusual.
  • Beryllium is effective in solving the recovery time problem in that beryllium, with an atomic number of 4 and an atomic mass of 9, is an extremely light material the ions of which appear to rapidly difiuse to cause the attainment of rapid recovery times in vacuum arc devices in which such electrodes are utilized.
  • the chopping current obtainable from devices utilizing beryllium electrodes is approximately of the same order of that obtainable utilizing copper, namely approximately 4 to 6 amperes.
  • FIGURE 4 of the drawing there are plotted the static breakdown voltage curves as a function of gap length for electrode pairs of zinc (curve A), silver (curve B), an intermetallic compound of Cu Sn (curve C), an alloy of 20% bismuth the remainder copper (curve D), an
  • gap chamber 30 comprises a wall member 31 which may be cylindrical in shape and is constructed of a suitable insulating material having at the ends thereof a pair of metallic end members 32 and 33 closing the volume therein to form a vacuum chamber. Suitable shields 34 are provided between casing 31' and end members 32 and 33 to render the chamber vacuum tight. Located within chamber 30 are a pair of spaced contacts or gap electrodes 35 and 36 which define a vacuum gap 37 therebetween. Upper contact 35-is suitably attached electrically and mechanically to a conducting rod 38 which is at its upper end united electrically and mechanically with end wall member 32.
  • Lower contact 36 is mounted upon and electrically united with conducting rod 39 which is electrically and mechanically connected with end wall member 33.
  • the electrical circuit which is sought to be protected or connected to vacuum gap device 30 is connected to end Wall members 32 and 33 by means of connecting lugs 40 and 41, electrically and mechanically affixed to respective wall end members 32 and 33.
  • a suitable insulator shield such as metallic cylindrical member 43 capped with an arc-preventing ferrule 44 is interposed between electrodes 35-36 and insulator 31 to prevent the latter from becoming coated with metal and becoming electrically short-circuited.
  • the volume within chamber 30 ' is maintained at a pressure of less than and preferably less than 1O millimeters of mercury as with respect to the device of FIGURE 1.
  • Contacts 35 and 36 are constructed in whole or in part of beryllium which is properly treated as with respect to the contacts and 16 of the device of FIGURE 1 in order to provide freedom from gas or gas-containing compounds in order to maintain the high vacuum conditions within chamber 30 as is described with respect to the device of FIGURE 1.
  • the devices constructed in accord with FIGURES 1 and 3 of the invention possess the rapid recovery time, high recovery strength and the static breakdown strength attributable to beryllium. While, to optimize these characteristics, it is desirable to have as high a proportion of beryllium as is possible in contacts utilized in the devices, it may be advisable that the beryllium be admixed in an alloy of another material in order that suitable mechanical strength, anti-welding characteristics, ductility and long life may be obtained.
  • the contacts may comprise an alloy of beryllium with approximately as much as 50% by Weight copper or silver, although it is preferable that no more than by Weight copper or silver be utilized.
  • substantially pure beryllium or an alloy of copper and beryllium or silver and beryllium, as set forth hereinbefore, may be purified so as to have less than 10* atomic parts of gas or gas-forming constituents therein and caused to be flowed into a porous matrix of a refractory material which may be formed by sintering tungsten, molybdenum, tungsten-carbide, molybdenum-carbide or like materials.
  • the tungsten or other refractory material contributes primarily the mechanical strength while the interrupting characteristics of the vacuum arc device are supplied by beryllium or the beryllium alloy which is denominated herein as the active arc-sustaining ionizable metallic substance.
  • gaseous impurities and gaseous-forming impurities as set forth herein may readily be obtained in beryllium contacts or in contacts of a beryllium alloy as utilized in the embodiments of the invention by, prior to casting the electrodes, subjecting the beryllium to a directional cooling and crystallization process so controlled as to cause a selective segregation of the gaseous-forming impurities and gases from the crystallized beryllium. Subsequent manipulative steps performed upon the beryllium involving melting, heat treating or other heat-involving process must thereafter be conducted in vacuo to maintain the necessary freedom from gases, principally oxygen.
  • a vacuum arc device exhibiting rapid recovery time and high static breakdown voltage characteristics and consisting essentially of: an evacuable envelope evacuated to a pressure lower than 10 millimeters of mercury; a pair of electrical terminals adapted for connection in an electrical circuit; a pair of electrodes located within said envelope, connected in circuit between said terminals and adapted to sustain an electric are therebetween, said are being comprised of ionized metallic parts which originate from said electrodes; each of said electrodes having a region upon which the respective elec trode spots for a current-carrying arc may be established and from which said metallic parts originate, at least one of said electrode regions being comprised of an active ionizable arc-sustaining metallic substance consisting essentially of beryllium.
  • a vacuum arc device exhibiting rapid recovery time and high static breakdown voltage characteristics and comprising: an evacuable envelope evacuated to a pressure lower than 10 millimeters of mercury; a pair of electrical terminals adapted for connection in an electrical circuit; a pair of electrodes located within said envelope, connected in circuit between said terminals and adapted to sustain an electric arc therebetween, said arc being comprised of ionized metallic parts which originate from said electrodes; each of said electrodes having a region upon which the respective electrode spots for a current-carrying arc may be established and from which said metallic parts originate, at least one of said electrode regions being comprised of an active ionizable arc-sustaining metallic substance comprising at least weight percent beryllium.
  • a vacuum alternating current circuit interrupter comprising an evacuable envelope evacuated to a pressure lower than 10* millimeters of mercury; a pair of electrical terminals adapted for connection in an alternating current circuit; a pair of electrodes located within said envelope, connected in circuit between said terminals and disposed in spaced apart relationship during circuit interrupting operation to allow for the establishment of a circuit interrupting arc therebetween, said arc being comprised of ionized metallic parts which originate from said electrodes; each of said electrodes having a region upon which the respective electrode spots for a currentcarrying arc may be established and from which said metallic parts originate, said electrode regions being comprised of an active ionizable arc-sustaining metallic substance consisting essentially of beryllium.
  • a vacuum alternating current circuit interrupter comprising an evacuable envelope evacuated to a pres sure lower than 10* millimeters of mercury; a pair of electrical terminals adapted for connection in an alternating current circuit; a pair of electrodes located within said envelope, connected in circuit between said terminals and disposed in spaced apart relationship during interrupting operation to allow for the establishment of a circuit interrupting arc therebetween, said are being comprised of ionized metallic parts which originate from said electrodes; each of said electrodes having a region 7 upon which the respective electrode spotsfor a currentcarrying arc may be established and from which said metallic parts originate, at least one of said electrode regions being comprised of an active ionizable arc-sustaining metallic substance comprising at least 80 weight percent beryllium.
  • a vacuum gap device comprising an evacuable envelope evacuated to a pressure lower than 10- millimetersof mercury; a pair of fixed electrical terminals adapted for connection in an electric circuit; a pair of fixed electrodes located within said envelope, connected in circuit between said terminals and disposed in spaced apart relationship to define a vacuum gap therebetween to allow for the establishment of an electric arc during operation, said are being comprised of ionized metallic particles originating from said electrodes; each of said electrodes having a region upon which respective electrode spots for the electric arc may be established and from which the arc-sustaining particles are taken, at least one of said electrode regions comprising an active ionizable arc-sustaining metallic substance consisting essentially of beryllium.
  • a vacuum gap device comprising an evacuable envelope evacuated to a pressure lower than 10- millimeters of mercury; a pair of fixed electrical terminals adapted for connection in an electric circuit; a pair of fixed electrodes located within said envelope, connected in circuit between said terminals and disposed in spaced apart relationship to define a'vacuum gap therebetween to allow for the establishment of an electric are therebetween during operation, said are being comprised of ionized particles of ionized metallic particles originating from said electrodes; each of said electrodes having a region upon which the respective electrode spots for the electric arc may be established and from which the arcsustaining particles are taken, at least one of said electrode regions being comprised of an active arc-sustaining ionizable metallic substance comprising at least 80 weight percent beryllium.

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US168436A 1962-01-24 1962-01-24 Arc ionizable beryllium electrodes for vacuum arc devices Expired - Lifetime US3140373A (en)

Priority Applications (6)

Application Number Priority Date Filing Date Title
DENDAT1251406D DE1251406B (US06633782-20031014-M00005.png) 1962-01-24
US168436A US3140373A (en) 1962-01-24 1962-01-24 Arc ionizable beryllium electrodes for vacuum arc devices
GB18935/65A GB1025944A (en) 1962-01-24 1963-01-22 Improvements in or relating to vacuum type circuit interrupter
GB2683/63A GB1025943A (en) 1962-01-24 1963-01-22 Improvements in or relating to vacuum type circuit interrupter
FR922377A FR1344824A (fr) 1962-01-24 1963-01-23 Interrupteur sous vide
SE10547/65A SE304326B (US06633782-20031014-M00005.png) 1962-01-24 1965-08-12

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US168436A US3140373A (en) 1962-01-24 1962-01-24 Arc ionizable beryllium electrodes for vacuum arc devices
US19657662A 1962-05-18 1962-05-18

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US3140373A true US3140373A (en) 1964-07-07

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US168436A Expired - Lifetime US3140373A (en) 1962-01-24 1962-01-24 Arc ionizable beryllium electrodes for vacuum arc devices

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US (1) US3140373A (US06633782-20031014-M00005.png)
DE (1) DE1251406B (US06633782-20031014-M00005.png)
FR (1) FR1344824A (US06633782-20031014-M00005.png)
GB (2) GB1025943A (US06633782-20031014-M00005.png)
SE (1) SE304326B (US06633782-20031014-M00005.png)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3497755A (en) * 1966-07-01 1970-02-24 Gen Electric Vacuum devices with electrode members containing oxygen - reactive minor constitutent
US3497652A (en) * 1968-11-01 1970-02-24 Helen W Horn Vacuum-type circuit interrupter with contact material containing a minor percentage of aluminum
US3742170A (en) * 1971-09-30 1973-06-26 Westinghouse Electric Corp Loud tap changer by-pass switch contact assembly and material composition thereof
US4028514A (en) * 1974-12-03 1977-06-07 General Electric Company High current vacuum circuit interrupter with beryllium contact
US4135071A (en) * 1976-03-17 1979-01-16 General Electric Company Vacuum circuit interrupter with disc-shaped beryllium contacts

Families Citing this family (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1065886A (en) * 1963-10-11 1967-04-19 Ass Elect Ind Improvements relating to vacuum-switch contacts
US3283103A (en) * 1963-12-06 1966-11-01 Gen Electric Means for controlling phase relationship between flux and current in a vacuum interrupter
GB1100259A (en) * 1965-02-16 1968-01-24 Ass Elect Ind Improvements relating to vacuum switch contacts
DE1227538B (de) * 1966-02-25 1966-10-27 Sachsenwerk Licht & Kraft Ag Vakuumschalter
US3624325A (en) * 1969-12-29 1971-11-30 Helen W Horn Vacuum-type circuit interrupter with weld-resistant contact material consisting essentially of copper and beryllium
US4072837A (en) * 1975-12-29 1978-02-07 General Electric Company High continuous current vacuum-type circuit interrupter
JPS596449B2 (ja) * 1976-05-27 1984-02-10 株式会社東芝 真空しや断器
JPS52155373A (en) * 1976-05-28 1977-12-23 Tokyo Shibaura Electric Co Vacuum breaker
GB8921475D0 (en) * 1989-09-22 1989-11-08 Gen Electric Co Plc High current switch components

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1812495A (en) * 1929-01-31 1931-06-30 Ac Spark Plug Co Electrical contact
US3014110A (en) * 1959-10-29 1961-12-19 Gen Electric Alternating current vacuum circuit interrupter

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1812495A (en) * 1929-01-31 1931-06-30 Ac Spark Plug Co Electrical contact
US3014110A (en) * 1959-10-29 1961-12-19 Gen Electric Alternating current vacuum circuit interrupter

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3497755A (en) * 1966-07-01 1970-02-24 Gen Electric Vacuum devices with electrode members containing oxygen - reactive minor constitutent
US3497652A (en) * 1968-11-01 1970-02-24 Helen W Horn Vacuum-type circuit interrupter with contact material containing a minor percentage of aluminum
US3742170A (en) * 1971-09-30 1973-06-26 Westinghouse Electric Corp Loud tap changer by-pass switch contact assembly and material composition thereof
US4028514A (en) * 1974-12-03 1977-06-07 General Electric Company High current vacuum circuit interrupter with beryllium contact
US4135071A (en) * 1976-03-17 1979-01-16 General Electric Company Vacuum circuit interrupter with disc-shaped beryllium contacts

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Publication number Publication date
SE304326B (US06633782-20031014-M00005.png) 1968-09-23
FR1344824A (fr) 1963-11-29
GB1025943A (en) 1966-04-14
DE1251406B (US06633782-20031014-M00005.png)
GB1025944A (en) 1966-04-14

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