US3683138A - Vacuum switch contact - Google Patents

Vacuum switch contact Download PDF

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Publication number
US3683138A
US3683138A US23392A US3683138DA US3683138A US 3683138 A US3683138 A US 3683138A US 23392 A US23392 A US 23392A US 3683138D A US3683138D A US 3683138DA US 3683138 A US3683138 A US 3683138A
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US
United States
Prior art keywords
contacts
electrodes
arc
percent
current
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.)
Expired - Lifetime
Application number
US23392A
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English (en)
Inventor
Akira Nabae
Mitsuru Arii
Osamu Arakawa
Sadao Sugiyama
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.)
Toshiba Corp
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Tokyo Shibaura Electric Co Ltd
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 Tokyo Shibaura Electric Co Ltd filed Critical Tokyo Shibaura Electric Co Ltd
Application granted granted Critical
Publication of US3683138A publication Critical patent/US3683138A/en
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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H1/00—Contacts
    • H01H1/02—Contacts characterised by the material thereof
    • H01H1/021—Composite material
    • H01H1/023—Composite material having a noble metal as the basic material
    • H01H1/0233—Composite material having a noble metal as the basic material and containing carbides
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H1/00—Contacts
    • H01H1/02—Contacts characterised by the material thereof
    • H01H1/021—Composite material
    • H01H1/027—Composite material containing carbon particles or fibres

Definitions

  • VACUUM SWITCH CONTACT [72] Inventors: Akira NabaefMitsui-u Arii, both of Tokyo; Osamu Arakawa; Sadao Sugiyama, both of Yokohama, all of Japan [73] Assignee: Tokyo Shibaure Electric Co., Ltd.,
  • ABSTRACT A vacuum switch for making and breaking an inductive electric circuit is composed of a highly evacuated envelope and a pair of separable electrodes located within the envelope.
  • At least one of the contacts of the electrodes is made of a sintered alloy essentially composed of a metal carbide, such as tungsten carbide, having low work function, another electrically conductive metal, such as silver, which also offers good machining characteristics, and certain wettable materials which allow the silver to impregnate the tungsten carbide by filling in the interstices between the particles thereof.
  • a metal carbide such as tungsten carbide
  • silver which also offers good machining characteristics
  • certain wettable materials which allow the silver to impregnate the tungsten carbide by filling in the interstices between the particles thereof.
  • the present invention relates to electrical vacuum switches, and more particularly to a vacuum circuit interrupter'of the type having a highly evacuated envelope and an enclosed pair of separable electrodes for making and breaking an electric circuit connected in series therewith which possesses improved. arc maintenance characteristics in typically low current interruptions.
  • vacuum type switches are widely used as current interrupters in alternating current circuits and in certain oscillation circuits wherein the oscillatory current form is one which typically oscillates between a substantially zero current level and a current level offset from the zero level line.
  • the electrical vacuum switches referred to herein are of the type normally employed for switching on and off" operations of an electric circuitinvolving the inductive loads therein, such as, for example, induction motors, synchronous motors, transformers, induction furnaces and the combination thereof.
  • This sudden cutting phenomena of the current flowing through the separated electrodes is referred to as a so-called chopping of the load currents, as indicated above, and the current level at which the chopping occurs is referred to as the chopping current level.
  • a type of vacuum switch has been provided in which a contact material having a high metal vapor pressure is employed in the arc regions of the electrodes,
  • the representative example of such contact material is an alloy consisting of copper as the major constituent and a substantial amount of bismuth as the minor one, extending to about 20 percent by weight of the entire amount of the contact material.
  • the current chopping phenomena is most likely to occur when a load current having a relatively small amplitude, such as, for example, one of 10 amperes, or less, is flowing through the separated electrodes. This results from the insufficiency of the metal vapors in the vicinity of the separated contact surfaces of the electrodes due to a relatively lower energy of lower current arc.
  • the arc region of the electrodes may be quickly consumed due to the extremely high temperature arcs which are initiated between the contact surfaces of the electrodes during each current interruption, and which accompany the evolvment, or giving off, of the positive evaporations of the metal vapors.
  • these vacuum type switches are usually employed so as to cause switching on and ofl of their accompanying circuits, for example, in an electric motor energization circuit, with high frequency of use.
  • the electrodes are likely to be consumed in an extremely short period of time, thereby shortening the effective life of the vacuum switch.
  • the higher temperature of the electric arc is likely to cause the electrode to melt, and then spatter down into the envelope of the vacuum switch.
  • the consumption of the electrode will occur even more rapidly than might be expected from the aforesaid evaporation, whereby additional shortening of the life of the electric vacuum switch occurs.
  • This spattering and melting of the electrodes may make many concaves on the contact surfaces of the electrodes, and thus there may be made some sharp edges at the peripheral portions of the concaves, whereby the dielectric strength of the vacuum between the separated electrodes will be reduced.
  • the dielectric strength of the vacuum type switch is reduced from the initial value to percent of that value after being subjected to several current interruption tests. This means that such switches must be produced which are capable of withstanding voltages higher by more than 40 percent of the voltage ratings thereof, and this involves an expensive manufacturing process.
  • an object of the present invention to provide a vaccuum type switch having separable electrodes within a highly evacuated envelope in which at least one of the electrodes includes an improved contact material at its contact surface, which material is not characteristic of higher metal vapor pressures than conventional materials heretofore employed, yet which maintains an electric arc between separated electrodes when the electrodes are separated to open an electric circuit connected to the switch gear.
  • Another object of the present invention is to provide an electric vacuum switch having separable electrodes within a highly evacuated envelope which possesses improved arc maintenance characteristics in low current interruptions.
  • a pair of separable electrodes positioned within a highly evacuated envelope so as to be capable of making and breaking an electric circuit in which they are connected.
  • a contact surface on at least one the the electrodes is preferably made of a sintered alloy including a mixture of a body of metal carbide having a low work function and at least one kind of wettable material being composed of nickel, copper and cobalt in preselected ranges as will be set forth in the following description.
  • the sintered 1 alloy is impregnated with at least one type of electrically higher conductive metal by an amount of sufficient proportion capable of improving the electric conductivity and machining characteristics of the entire contact material including said body of metal carbide.
  • FIG. shows an elevational sectional view of an electrical vacuum switch constructed in accordance with the present invention.
  • the vacuum type switch conventionally comprises a highly evacuated envelope 11 having a cylindrical side wall 12, which may be made of any suitable insulating material, such as, for example, glass, ceramics or the like, and a pair of separable contacts 13 and 14 made of an improved material according to the present invention and located within the envelope.
  • One of the contacts 13 is stationary and is secured to an inner end of a stationary electrode 15, the end of which extends through a metallic end cover, or plate 16 located on an upper peripheral portion of the cylindrical side wall 12.
  • a vacuum-tight seal member 17 is provided between the peripheral portions of the end cover 16 and one of the open ends of the insulating side wall 12.
  • the portion of the end cover 16 through which the stationary electrode 15 extends is vacuum-tightly sealed ofi by any suitable sealing means, such as a weld.
  • the uppermost end of the stationary electrode 15 is connected with a conductor, which, in turn, is connected to an AC. power supply (not shown).
  • the other contact 14 is a movable one, which is securely mounted on an inner end of a movable electrode 18, the other end of which is connected to an AC. conductor of an AC. load circuit located outside of the envelope, as well as to a driver which acts to reciprocably move the electrode 18 and the contact 14 between positions which are alternately close to and separate, or further away, from the stationary contact 13.
  • a vacuum-tight seal member 19 for vacuum-tightly sealing the envelope 11 between the peripheral portions at the other open end of the cylindrical side wall 12, opposite the cover 16, and a separate cover, or plate, 20.
  • the plate has an opening 21 through which an outer end of the movable electrode 18 slidably extends out of the envelope 11.
  • a flexible metallic bellows 22 is a vacuum-tightly secured at one end thereof to the edge portion of the opening 21, and the other end of the bellows 22 is vacuumtightly connected to the movable electrode 18 through a sealing cap member 23.
  • the vacuum type switch constructed in accordance with the present invention is not intended to rely solely upon the utilization of function due to the higher metal vapor pressure to maintain an electric are 25 occurring between the separated contacts 13 and 14 when the device is switched off for interrupting the current flowing in the switch circuit.
  • the contacts are opened for switching off, or interrupting the current flow, there will occur certain metal vapors between the separated contacts which arise from the composition of the contact material as explained hereinafter. These metal vapors will, however, be diffused into the vacuum space around the arc and thereby eventually result in final extinction of the arc.
  • cap type seal 23 which effectively prevents the depositions of the vapors on the surface of the bellows through its specific sealing arrangement.
  • a part of the aforesaid vapors might be deposited on the inner surface of the side wall 12 which is made of insulating material. This may result in the lowering of the dielectric strength along the axial direction of the side wall.
  • a cylindrical shield member 24 around the contact area and isolated from the inner surface of the side wall 12 and the contacts 13 and 14, respectively.
  • the shield 24 will catch the metal vapor particles randomly directed toward the inside wall of the envelope 11, and effectively preventing the aforesaid lowering of the dielectric strength of the envelope wall.
  • the arc includes substantial metallic particles which are evaporated from the contact surfaces and possess good electric conductive characteristics for normally maintaining the are even at low current levels.
  • these metallic particles or vapors will rapidly diffuse into the vacuum atmosphere around the arc, causing it to be extinguished quickly whenever the current is fully interrupted, which normally occurs at or close to the first current zero in the applied alternating current wave form.
  • the contact material is made of a sintered alloy comprising silver (Ag) and tungsten carbide (WC).
  • Tungsten carbide has the characteristic of a low work function, that is, it possesses higher thermionic electron emission characteristics, and besides, it is a kind of refractory material.
  • tungsten carbide is also difiicult to machine for making the contacts.
  • Ni, Cu, and Co are the wettable materials for the tungsten carbide (WC), and they operate to improve the wettable characteristics of the tungsten carbide (WC) so as to make capable easier impregnation of the Ag into the WC in every nook and corner, or among the interstitial spaces, thereof.
  • the powdered WC, Ni, Cu and Co are mixed, and then they are sintered to make a sintered alloy. Then, the resultant sintered alloy is located within an exhausted atmosphere, and either sunk in a bath filled with thev molten silver or has the base portion thereof immersed in the molten silver.
  • the molten silver can be impregnated among the particles of tungsten carbide to fill therewith all of the interstitial spaced among them.
  • the aforesaid wettable materials greatly contribute to this impregnation process.
  • this good state of the-impregnation has been confirmed in the fact that the resultant contact material has not shown the emanation therefrom of the ionizable gases which might have existed among the WC particles when the contact material has suffered from the higher temperature of electric arcs.
  • the examinations, or tests, on the current chopping level have been carried out more than 30 times per each pair of electrodes with 10 amperes.
  • the chopping current level is the current amplitude at which the chopping phenomena occurs and it varies with each test. Usually the maximum value out of many test datum, for example, more than 30, is adapted as the current chopping level of the electrodes.
  • the electrodes under these tests had the dimensions of 22 mm. diameter, 5 mm. thickness and 25 mm. diameter, 5 mm. thickness.
  • a sintered alloy including 30 percent by weight of Ag has given a chopping level between 1.1 A. and 2.0 A.
  • another alloy including 40 percent by weight of Ag has shown a chopping level between 1.9 A and 3.2 A.
  • a further WC alloy including 55 percent by weight of Ag has shown levels between 2.4 A and 4.2 A.
  • the contact material becomes harder to machine as the amount of silver impregnated in the sintered WC alloy is decreased.
  • the contents of Ag in the sintered WC are more than 60 percent by weight, another defect arises in that the contact material exhibits a higher chopping current level. This results from thereason that it is difficult to maintain the electric arc between the separated contacts because of the lower temperature involved due to smaller current conditions. Such a lower temperature rise also results from the higher heat conductivity of the silver.
  • the silver impregnated within the sintered WC in accordance with the present invention functions to im prove the electric conductivity of the sintered alloy.
  • the electrodes 15 and 18 having the contacts 13 and 14 are separated in order to interrupt the electric circuit, an electric are 25 is initiated between the separated contacts, and then it makes temperatures of the contact surfaces rise to cause the cathode spots on the contact surfaces from which may be emanated the thermionic electrons.
  • the WC has a low work function, so that even though the currents flowing through the are initiated between the separated contacts have smaller amplitudes, there will nevertheless occur an emission of the thermionic electrons sufiicient to ionize the smaller amounts of silver vapor which exist between the separated contacts.
  • vapor pressure of the Ag is higher than that of the Cu, comparing at the same temperature.
  • the low work function material WC may be replaced by MoC, ZrC, TiC, VC and SiC, as well as the combinations of these. It should be further noted that the amount of the free carbon involved in the contact material is preferably less than 0.05 percent by weight for the purpose of preventing the lowering of the wettable characteristics of the contact material.
  • a vacuum type switch for maintaining an arc at low current levels comprising a highly evacuated envelope and a pair of separable contacts located in the envelope so as to make and break an electric circuit, the improvement comprising:
  • At least one of the separable contacts being formed of a sintered metal carbide being selected from a group consisting of WC, MoC, ZrC, TiC, VC, SiC, and the combinations thereof, and including a wettable material composed of 0.1 to 5 percent by weight of Ni,
  • said electrically conductive material being silver (Ag).

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  • Contacts (AREA)
  • High-Tension Arc-Extinguishing Switches Without Spraying Means (AREA)
  • Manufacture Of Switches (AREA)
US23392A 1970-03-20 1970-03-27 Vacuum switch contact Expired - Lifetime US3683138A (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB1349770 1970-03-20
US2339270A 1970-03-27 1970-03-27

Publications (1)

Publication Number Publication Date
US3683138A true US3683138A (en) 1972-08-08

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Application Number Title Priority Date Filing Date
US23392A Expired - Lifetime US3683138A (en) 1970-03-20 1970-03-27 Vacuum switch contact

Country Status (7)

Country Link
US (1) US3683138A (enrdf_load_stackoverflow)
BE (1) BE756372A (enrdf_load_stackoverflow)
CH (1) CH517370A (enrdf_load_stackoverflow)
DE (1) DE2045173C3 (enrdf_load_stackoverflow)
FR (1) FR2083792A5 (enrdf_load_stackoverflow)
GB (1) GB1257417A (enrdf_load_stackoverflow)
NL (1) NL7103703A (enrdf_load_stackoverflow)

Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3996437A (en) * 1973-12-03 1976-12-07 Cutler-Hammer, Inc. Vacuum contactor for motor control and method of making
EP0042152A1 (en) * 1980-06-18 1981-12-23 Hitachi, Ltd. Vacuum circuit breaker
US4367382A (en) * 1979-05-22 1983-01-04 Tokyo Shibaura Denki Kabushiki Kaisha Vacuum circuit breaker
US4424429A (en) 1981-09-16 1984-01-03 Mitsubishi Denki Kabushiki Kaisha Contactor for vacuum type circuit interrupter
EP0153635A2 (en) 1984-02-25 1985-09-04 Kabushiki Kaisha Meidensha Contact electrode material for vacuum interrupter and method of manufacturing the same
US4940862A (en) * 1989-10-26 1990-07-10 Westinghouse Electric Corp. Vacuum interrupter with improved vapor shield for gas adsorption
US5420384A (en) * 1990-11-28 1995-05-30 Kabushiki Kaisha Toshiba Contact material for a vacuum interrupter
US6024896A (en) * 1997-03-07 2000-02-15 Kabushiki Kaisha Toshiba Contacts material
US6027821A (en) * 1995-12-13 2000-02-22 Kabushiki Kaisha Toshiba Contact material for vacuum interrupter and method for producing the same
EP0929088A3 (en) * 1998-01-06 2000-03-22 Kabushiki Kaisha Toshiba Contact material
US20070007249A1 (en) * 2005-07-07 2007-01-11 Shigeru Kikuchi Electrical contacts for vacuum circuit breakers and methods of manufacturing the same
US20100018843A1 (en) * 2008-07-24 2010-01-28 General Electric Company Low work function electrical component
US10468205B2 (en) * 2016-12-13 2019-11-05 Eaton Intelligent Power Limited Electrical contact alloy for vacuum contactors

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3997748A (en) * 1975-06-23 1976-12-14 General Electric Company Vacuum interrupter with primary electrode surrounded by high dielectric strength shield
GB2143595A (en) * 1983-07-18 1985-02-13 Bearing Technology Limited Plastics bearing
DE3428276A1 (de) * 1984-08-01 1986-02-06 Doduco KG Dr. Eugen Dürrwächter, 7530 Pforzheim Werkstoff fuer elektrische kontakte auf der basis von silber mit wolframkarbid und verfahren zu seiner herstellung

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2975256A (en) * 1958-07-24 1961-03-14 Gen Electric Vacuum type circuit interrupter
US3014110A (en) * 1959-10-29 1961-12-19 Gen Electric Alternating current vacuum circuit interrupter
US3254189A (en) * 1961-05-15 1966-05-31 Westinghouse Electric Corp Electrical contact members having a plurality of refractory metal fibers embedded therein
GB1079013A (en) * 1964-04-21 1967-08-09 English Electric Co Ltd Improvements in or relating to contacts and electrodes

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2975256A (en) * 1958-07-24 1961-03-14 Gen Electric Vacuum type circuit interrupter
US3014110A (en) * 1959-10-29 1961-12-19 Gen Electric Alternating current vacuum circuit interrupter
US3254189A (en) * 1961-05-15 1966-05-31 Westinghouse Electric Corp Electrical contact members having a plurality of refractory metal fibers embedded therein
GB1079013A (en) * 1964-04-21 1967-08-09 English Electric Co Ltd Improvements in or relating to contacts and electrodes

Cited By (19)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3996437A (en) * 1973-12-03 1976-12-07 Cutler-Hammer, Inc. Vacuum contactor for motor control and method of making
US4367382A (en) * 1979-05-22 1983-01-04 Tokyo Shibaura Denki Kabushiki Kaisha Vacuum circuit breaker
EP0042152A1 (en) * 1980-06-18 1981-12-23 Hitachi, Ltd. Vacuum circuit breaker
US4424429A (en) 1981-09-16 1984-01-03 Mitsubishi Denki Kabushiki Kaisha Contactor for vacuum type circuit interrupter
EP0153635A2 (en) 1984-02-25 1985-09-04 Kabushiki Kaisha Meidensha Contact electrode material for vacuum interrupter and method of manufacturing the same
EP0153635A3 (en) * 1984-02-25 1986-02-05 Kabushiki Kaisha Meidensha Contact electrode material for vacuum interrupter and method of manufacturing the same
US4686338A (en) * 1984-02-25 1987-08-11 Kabushiki Kaisha Meidensha Contact electrode material for vacuum interrupter and method of manufacturing the same
US4940862A (en) * 1989-10-26 1990-07-10 Westinghouse Electric Corp. Vacuum interrupter with improved vapor shield for gas adsorption
US5420384A (en) * 1990-11-28 1995-05-30 Kabushiki Kaisha Toshiba Contact material for a vacuum interrupter
US6027821A (en) * 1995-12-13 2000-02-22 Kabushiki Kaisha Toshiba Contact material for vacuum interrupter and method for producing the same
US6024896A (en) * 1997-03-07 2000-02-15 Kabushiki Kaisha Toshiba Contacts material
EP0863521A3 (en) * 1997-03-07 2001-03-21 Kabushiki Kaisha Toshiba Contacts material
CN1071925C (zh) * 1997-03-07 2001-09-26 株式会社东芝 触点材料
EP0929088A3 (en) * 1998-01-06 2000-03-22 Kabushiki Kaisha Toshiba Contact material
US20070007249A1 (en) * 2005-07-07 2007-01-11 Shigeru Kikuchi Electrical contacts for vacuum circuit breakers and methods of manufacturing the same
US7662208B2 (en) * 2005-07-07 2010-02-16 Hitachi, Ltd. Electrical contacts for vacuum circuit breakers and methods of manufacturing the same
US20100018843A1 (en) * 2008-07-24 2010-01-28 General Electric Company Low work function electrical component
US10468205B2 (en) * 2016-12-13 2019-11-05 Eaton Intelligent Power Limited Electrical contact alloy for vacuum contactors
US10804044B2 (en) 2016-12-13 2020-10-13 Eaton Intelligent Power Limited Electrical contact alloy for vacuum contactors

Also Published As

Publication number Publication date
CH517370A (de) 1971-12-31
NL7103703A (enrdf_load_stackoverflow) 1971-09-22
DE2045173C3 (de) 1980-02-14
DE2045173A1 (de) 1971-10-07
FR2083792A5 (enrdf_load_stackoverflow) 1971-12-17
DE2045173B2 (de) 1979-06-07
GB1257417A (enrdf_load_stackoverflow) 1971-12-15
BE756372A (fr) 1971-03-01

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