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Publication numberUS3818166 A
Publication typeGrant
Publication dateJun 18, 1974
Filing dateAug 23, 1973
Priority dateMar 6, 1972
Publication numberUS 3818166 A, US 3818166A, US-A-3818166, US3818166 A, US3818166A
InventorsEmmerich W
Original AssigneeWestinghouse Electric Corp
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Contacts for vacuum interrupter of small outside diameter
US 3818166 A
Abstract
A vacuum type circuit interrupter is provided having separable mating contacts. Multiple arc rails are attached to each contact, the arc rails extend from the contact to which they are attached past the mating contact. The arc rails extend from the contact in a direction substantially parallel to the supporting rod means of the mating contact, so as to provide paths between the arc rails and the supporting rod means along which an arc formed during circuit interruption can travel.
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Description  (OCR text may contain errors)

United States Patent [191 Emmerich CONTACTS FOR VACUUM INTERRUPI'ER OF SMALL OUTSIDE DIAMETER Inventor: Werner S. Emmerich, Pittsburgh,

Assignee: Westinghouse Electric Corporation,

Pittsburgh, Pa.

Filed: Aug. 23, 1973 Appl. No.: 390,964

Related US. Application Data Continuation of Ser. No. 232,083, March 6, 1972, abandoned.

[52] US. Cl. 200/144 B, 313/305, 313/306,

, 315/35, 200/166 B Int. Cl. I-I0lh 33/66 Field of Search..... 200/144 B, 166 B; 313/306,

313/307, 308, 325, DIG. 5; 315/35, 36

References Cited UNITED STATES PATENTS 1/1937 Heising 313/306 Primary ExaminerRobert S. Macon Attorney, Agent, or Firm-H. G. Massung i571 ABSTRACT A vacuum type circuit interrupter is provided having separable mating contacts. Multiple arc rails are attached to each contact, the arc rails extend from the contact to which they are attached past the mating contact. The arc rails extend from the contact in a direction substantially parallel to the supporting rod means of the mating contact, so as to provide paths between the arc rails and the supporting rod means along which an are formed during circuit interruption can travel.

12 Claims, 10 Drawing Figures 3 8 l 8 l 66 1 y I 2 CONTACTS FOR VACUUM INTERRUPTER OF acting with the arc shielding. It is therefore desirable to SMALL OUTSIDE DIAMETER control are movement so that the size of the vacuum This is a continuation, of application Ser. No. 232,083 filed Mar. 6, 1972 now abandoned.

BACKGROUND OF THE INVENTION The present invention concerns a concept for separable contacts or electrodes for a vacuum type circuit interrupter. More specifically, the present invention is concerned with a method of utilizing the contact support means to aid in arc control during circuit interruption, and to substantially increase the available arcing surface.

A vacuum type circuit interrupter comprises a pair of movable contacts disposed within a highly evacuated tubular envelope. These contacts are movable between a closed position in which they are in electrical contact and an open position in which the contacts are sepa rated and an arcing gap is established therebetween. During circuit interruption the contacts are separated and an arc is established across the arcing gap. For an alternating current circuit the arc is normally maintained until approximately the first current zero of the alternating current (AC) wave, at which time the arc is extinguished. If most of the particles and vapors generated by the are are quickly removed, the vacuum regains its high di-electric strength and the arc is kept from reigniting, thereby completing interruption.

It has been recognized that the interrupting capacity of a vacuum type circuit interrupter can be materially increased by moving the are, formed during circuit interruption, along the surfaces of the contacts or adjacent structures. Movement of the arc tends to minimize the amount of metallic particles or vapors generated during interruption and also tends to increase the degree of diffusion of the vapors and particles that are generated allowing the vacuum to quickly recover its dielectric strength, after an arc is extinguished, and to thereby prevent reignition of the arc.

Measurements indicate that the interrupting capability of electrodes tends to increase with size and the surface available for arcing. However, making the electrodes larger in diameter soon brings the outer edges too close to the shield, so that a definite limitation exists in this respect. If the diameter of the contact is further increased the outer diameter of the vacuum interrupter must also be increased. For many applications, however, increasing the diameter of the interrupter is very undesirable. For example, standard spacing between the three-phase bus bars in metal clad switchgear dictates a maximum diameter for vacuum interrupters to be used therein. The diameters of the vacuum interrupter, used in these applications, must be small enough to maintain the required basic insulation level (BIL) between phases and also leave sufficient clearance for mounting and heat dissipation. Higher interrupting capacities than can be attained with a conventional vacuum type circuit interrupters of a given physical size, are desired. Another reason for limiting the diameter of vacuum interrupters is that because of the comparatively high vacuum that must be maintained therein, their volume should be as small as possible. It is very desirable to prevent the arc formed during circuit interruption from interacting with the arcing shield. High energy arcs tend to spread out of control, vaporizing electrode material, carrying metallic vapors onto the walls of the insulating housing, and also interinterrupter of a given current capacity can be reduced.

An alternate solution, rather than increasing contact diameter to increase interrupting ability, consists of changing the electrode structure so that arcing takes place at positions other than between the contacts. It has been found experimentally that current interruption limits are reached when the arc interacts with the shield. In most cases a hole is melted in the arc shield and the interrupter fails. It is therefore desirable that the are be controlled so that during circuit interruption it does not interact with the shield.

SUMMARY OF THE INVENTION This invention teaches more effective use of the available vacuum interrupter volume for are control and increased interrupting capacity. Although the diameter of electrodes is limited, without increasing the diameter of the vacuum interrupter, there is a great dealof unused space in the insulating envelope around the longitudinal axis of the vacuum interrupter. Due to the fact that the vacuum interrupter must be long enough to maintain a given basic insulation level (BIL) in air along the tubular insulating envelope, the minimum length of the interrupter is fixed. This invention teaches how to make use of this available length and volume and teaches how to increase the effective area of the arcing surfaces. v

According to the present invention, arcing rails extend outward from the primary contact surfacesand run generally parallel to and in close proximity with the longitudinal axis of the support means to which the opposite contact is attached. These are rails are made as long as practicable consistent with good design. In a given vacuum interrupter each electrode has the same number of multiple arc rails and these electrodes are disposed in the vacuum interrupter so that the arc rails are set in an interlacing configuration. These are rails are interlaced so that the arc rails of each electrode extend substantially parallel to the longitudinal axis of the conducting rod means to which the opposite electrode is attached. During circuit interruption when the contacts of the vacuum interrupter are separated an arc will be formed at the point where the contacts were last touching. If this arc is not started and maintained exactly along the center line of the contact elements, magnetic forces will force the arc towards the edge of the contact element. The direction of movement of the are then undergoes a rotation of and the arc travels along an arc rail and the rod of the opposite electrode. Whereas the volume available to an arc travelling in a radial direction is limited by the diameter of the electrodes this is not the case for an are travelling along the longitudinal axis of the interrupter. For an arc travelling along the longitudinal axis of the interrupter the length as well as width'of the interrupter can be utilized. Thus the available arcing area can be substantially increased by following the teachings of the present invention. Furthermore, the conducting rods to which the contacts are attached up to now have merely been a current carrying device, following the teachings of the present invention the contact support means becomes part of the available arcing surface. This invention also allows maximum open area towards the shield for vapor expansion and condensation of the arc generated vapors and particles so that the high dielectric strength of the vacuum will be quickly restored after arc extinction. V

In a second embodiment of the invention the rodsupport means to which the contacts are attached is contoured or flattened. This contouring of the rod support means is done to control the arc movement and to keep the arc circumferential or azimuthal rather than radial.

In a third embodiment of the invention the ends of the arc rails are interlocked for rigidity. Interlocking the ends of the arc railsby suitable means, such as a ring, increases the physical strength of the contact and permits use of a greater number of arc rails. If the material used forinterlocking the ends of the arc rails is an electrical conductor it may effect movement of the arc.

Devicesv utilizing the teaching of the present invention have several advantages. For example, the rod support means, to which the contacts are attached, which in prior art interrupters had only been used for current carrying members now become part of the available arcing surface thus drastically increasing the arcing areas available. A preliminary estimate indicates that available arcing area can easily be doubled, as compared to, butt electrodes of the diameter used in typical vacuum type circuit interrupter of the same current capacity. Another advantage of the present invention is that are movement is controlled so as to lessen the possibility that an arc will interact with the arc shield. Still another advantage of the present invention is that by constructing contacts in accord with the teaching of the present invention the outer diameter of a vacuum type circuit interrupter is smaller than the outer diameter of prior art vacuum'interrupters of the same current carrying capacity.

BRIEF DESCRIPTION .OF THE DRAWINGS Further advantages of the present invention will be readily apparent upon reading the following description taken in conjunction with the drawings in which:

FIG. 1 is a vertical sectional view of the vacuum type circuit interrupter embodying a contact construction of the present invention;

FIG. 2 is a side view of a contact used in the vacuum interrupter shown in FIG. 1; v

FIG. 3 is a top view of the contact shown in FIG. 2;

FIG. 4 is an isometric view of the contacts shown in FIG. 1;

FIG. 5 is a top view of a contact structure similar to FIG. 3 but having six arc rails; I

FIG. 6 is a side view of the contact structure shown in FIG. 4;

FIG. 7 is a side view of a contact structure in which the supporting rod means is contoured to control are movement;

FIG. 8 is a top view of the contact structure shown in FIG. 7;

FIG. 9 is an isometric view of vacuum interrupter contacts, in the closed position, in which a ring is used to interlock the ends of the arc rails; and

FIG. 10 is a view of the contact shown in FIG. 9 in the open position.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawings and more particularly to FIG. 1 there is shown a vacuum'type circuit interrupter 10 embodying the teaching of the present invention. The vacuum type circuit interrupter 10 comprises a highly evacuated envelope 12 formed of glass or suitable material and a pair of metallic end caps 14 and 16 closing off the end of the insulating envelope 12. Suitable seals 18 areprovided between theend caps 14 and 16 and the insulating envelope 12 to render the envelope 12 vacuum tight. The vacuum in envelope 12 under normal operating conditions is lower than 10 torr so that the mean free path of electrons will be longer than the potential breakdown distance within the envelope l2.

Disposed within the envelope 12 are a pair of relatively movable electrodes or contacts 20 and 22 embodying the teaching of the present invention. As shown in FIG. 1 when these contacts 20v and 22 are separated there is an arcing gap 24 located therebetween. The upper contact 20 is stationary and is secured to a conducting rod support means 26 by a suitable means such as welding or brazing. The conducting rod 26 is secured at its upper end to the stationary end cap 14 by suitable meanssuch as welding or brazing. The lower contact 22 is movable and is joined to a conducting opcrating rod support means 28. The conducting operating rod 28 is suitably mounted for movement along the longitudinal axis of the insulating envelope 12. The

movable operating rod 28 projects through an opening 30 in the bellows end cap 16. As shown in FIG. 1 a flexible metal bellows 32 is secured in sealing relationship at its respective opposite ends to movable operating rod 28 and the opening 30 in the bellows end cap 16. The flexible metal bellows 32 provides a seal about the rod 28 to allow for movement of the rod 28 without impairing the vacuum inside the insulating envelope l2.

Coupled to the lower end of the operating rod 28 suitable actuatingmeans (not shown) is provided for driving the movable contact 22 upward into engagementwith the stationary contact 20 so as to close the interrupter 10. The actuating means isalso capableof returning the contact 22 to its open position, so as to open the interrupter 10. A circuit opening operation will for example entail a typical gap length, when the contacts are fully separated, of approximately 1/2 inch.

When electrodes 20 and 22 of a vacuum interrupter 10 are opened, at the beginning of circuit interruption, a metallic arc initiates between the separated electrodes 20 and 22 and serves as a vehicle for current conduction until the arc is extinguished, which in an alternating current circuit occurs near the first current zero of the alternating current wave. The are 34 thatis established across the arcing gap 24 between the electrodes 20 and 22, as electrodes 20 and 22 are open and also when they are closed, vaporizes some of the contact material and these vapors are dispersed from the arcing gap 24 towards the inside of the insulating envelope 12. The internal surfaces of the insulating envelope 12 are protected from the condensation of the are generated metallic vapor and particles thereon by means of a tubular metallic shield 36. The tubular metallic shield 36 is supported on the insulating envelope l2, and preferably electrically isolated from both end caps 16 and 14. This shield 36 acts to intercept and condense are generated metallic vapors before they can reach the insulating envelopes 12. To reduce the chances of metallic vapors or particles by-passing the main shield 36 a pair of end shields 38 and 40 are provided at opposite ends of the central shield 36. A cupshaped shield 42 is attached to the movable operating rod 28 and surrounds the flexible metallic bellows 32 to prevent the bellows 32 from being bombarded by are generated metallic vapors or particles.

During circuit interruption a-relatively large amount of power is dissipated in the confined area of the vacuum interrupter between the contacts and 22. Because of the high energy concentration impressed upon the contacts 20 and 22, during the arcing interval, substantial contact heating and erosion takes place and it is therefore desirable to move the established are outward away from the primary contacting surfaces 44. If the are 34 is kept in continuous motion the deteriorative effects of the are 34 on the electrode material is distributed and electrodes 20 and 22 have a longer life. Referring now to FIGS. 1, 2, 3 and 4 note that the contacts 20 and 22 are identical. As shown in FIGS. 2, 3 and 4 contact 22 comprises a contact surface 44, are rails 46 and a main body portion 48. The main body portion 48 of contact 22 is attached to the conducting rod support means 28. As shown in FIGS. 1 and 4 when. the contacts 20 and 22 are disposed in a vacuum inter-,

rupter 10 contact surfaces 44 face each other and one contact 20 and 22 is rotated so that its arc rails 46 are displaced an equal angular distance from the arc rails 46 of the opposite contact 20 or 22. The are rails 46 of each contact 20 and 22 extend past the contact surface 44 of the opposite contact 22 or 20 and run parallel to and are spaced from the main body portion 48 and the rod support means 26 or 28 to which the opposite contact 20 or 22 is attached. During circuit interruption when the contacts 20 and 22 of the vacuum interrupter are separated an are 34 is formed across the arcing gap 24. Unless the arc is exactly centered, and this is an unstable position, magnetic forces will drive the arc toward the edge of the contact surface 44. One end of the are 34 will then travel along one of the arc rails 46 and the other end of the arc will move across the main body portion 48 and along the rod 26 and 28 of the opposite electrode 20 and 22 until the arc 34 is extinguished. The are 34 thus travels between the arcing rail 46 and the rod 26 and 28 to which the opposite contact is attached as shown in FIG. 1 and the are 34 is thus contained and cannot readily bow out and contact the main arc shield 36. I

FIG. 5 shows a contact similar to the contact in FIG. 3 but with six arcing rails 46 rather than two arcing rails 46 as shown in FIG. 3. When this contact 22, as shown in FIGS. 5 and 6, is used in a vacuum interrupter 10 an identical stationary contact 20 is also used. When the fixed contact 20 and the movable contact 22 each have six are rails, as shown in FIG. 5, one of the contacts 20 or 22 is rotated approximately around its longitudinal axis with respect to the other contact 20 and 22 so that when the contact 20 and 22 are disposed within the vacuum interrupter 10 the contact surfaces 44 go together and the arc rails 46 of these contacts 20 or 22 extend past the arc rails of the opposite contact 20 or 22 in an interlacing fashion. The six are rails of contact 22, as shown in FIG. 6 are attached to or made integral with the main body portion 48. Are travel for the contact shown in FIG. 6 is similar to are travel for the contact shown in FIG. 2. When an are 34 is initiated during circuit interruption one end travels along one of the arc rails 46 while the other end travels along the rod 26 or 28 of the opposite electrode until the are 34 is extinguished. Note that for both of the contacts shown in FIGS. 2 and 6 maximum open area is allowed towards the arc shield for vapor expansion, so that after circuit interruption are generated vapors and particles can be quickly condensed and the high dielectric strength of the vacuum can be quickly recovered.

FIGS. 7 and 8 show another embodiment of the invention. In this embodiment of the invention support means 50 for the contact surface 44 is contoured into a generally planar shaped configuration. When two contacts 20 and 22 of the embodiment shown in FIG. 7 are disposed within a vacuum interrupter lllthe are 34 that is initiated during circuit interruption travels between the arc rail 46 and the planar surface support means 50 of the opposite electrode 20 or 22. By having the area 50 which supports the contact surface 44 planar rather than rod shaped as shown in FIG. 2, it is felt that the are 34 can be controlled more effectively. With this embodiment the arc can be kept azimuthal rather than radial.

FIGS. 9 and 10 show still another embodiment of the invention in which the ends of the arc rails .46 are interlocked for increased rigidity. A ring 52 can be used for an interlocking means for rigidly connecting the ends of the arc rails 46 as shown in FIGS. 9 and 10. The ring 52 can be secured to the arc rails 46 by any suitable means such as welding or brazing. The are rails 46 are attached to or are integral with the main body portion 48 of contacts 20 or 22. During circuit interruption an are 34 is formed between contacts 20 and 22, one end of the arc will travel along one of the arc rails 46 while the other end of the are 34 will travel along the rod 26 and 28 which supports the opposite electrode 20 or 22, whose arc rails are not involved with the arcing. The are 34 will travel along the rod 26 or 28 and the arc rail 46 until it is extinguished.

Vacuum type circuit interrupters l0 utilizing the teachings of this invention have several advantages such as greatly increased arcing surfaces without an increase in the diameter of the vacuum interrupter 10. The are 34 is also effectively controlled so that it does not interact with the main arcing shield 36 so as to cause failure of the vacuum interrupter 10. These embodiments also allow for a large open area toward the shield for vapor expansion, so that are generated gases and vapors can be quickly condensed and removed after arc interruption in order that the high dielectric strength of the vacuum interrupter 10 may be quickly recovered.

Since numerous changes may be made in the abovedescribed apparatus and different embodiments of the invention may be made without departing from the spirit and scope thereof, it is intended that all the matter contained in the foregoing description and shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is: t

l. A vacuum type circuit interrupter comprising a sealed highly evacuated insulating envelope, a first contact disposed within said evacuated envelope, a second mating contact disposed within said insulating enterruption, a first set of a plurality of arcing rails extending from and movable with said first contact past the single arcing gap to a position in close proximity to said second contact support means, and a second set of a plurality of arc rails extending from and movable with said second contact past the single arcing gap to a position in close proximity to said first contact support means, said arcing rails are constructed to move the are formed during circuit interruption from the arcing gap to a position radially disposed between one of said arcing rails and the contact support means of the mating contact.

2. A vacuum interrupter as claimed in claim 1 wherein said first contact support means comprises a first conducting rod. and said second contact support means comprises a second conducting rod.

3. The combination as claimed in claim 2 wherein said first set of arc rails runs parallel to and in close proximity to said second conducting rod and said second set of arc rails runs parallel to and in close proximity to said first conducting rod.

4. The vacuum interrupter as claimed in claim 1 wherein said first set of arc rails are equally spaced around said first contact and said second set of arc rails are equally spaced around said second contact.

5. A vacuum type circuit interrupter as claimed in claim 1 wherein the free ends of said first set of arc rails are rigidly fixed by a first interlocking means and the free ends of said second set of arc rails are rigidly fixed by a second interlocking means. i v

6. The combination as claimed in claim 5 wherein said first interlocking means comprises a first ring to which the ends of said first set of arc rails are attached and said second interlocking means comprises a second ring to which the ends of said second set of arc rails are attached. I

7. A vacuum type circuit interrupter as claimed in claim 1 wherein said first contact support means comprises a portion having a flat surface and said second contact support means comprisesa portion having a flat surface.

8. A vacuum type circuit interrupter comprising:

a sealed highly evacuated insulating envelope;

a first relatively stationary contact disposed within said evacuated envelope; a second mating relatively movable contact disposed within said evacuated envelope;

a first contact support means to which said first contact is secured for supporting said first contact;

contact and a second position spaced from-said second contact to establish an arcing gap therebetweenacross which an arc is formed during circuit interruption; I

a first set of a plurality of arcing rails extending from said first contact'past the arcing gap to a position in close proximity to said second contact support means; Y

a second set of a plurality of arcing rails attached to and movable unitarily therewith said second relatively movable contact and extending past the arcing gap to a position in close proximity to said first contact'support means;

said first set of arcing rails and said second set of arcing rails being spaced from the support means of the mating contact by a distance less than they are spaced from each other; and,

said first set or arcing rails and said second set of arcing rails being constructed to move the are formed during circuit interruptionfrom the arcinggap to a position radially disposed between one of said arcing rails and thecontact support means of the mating contact.

9. A vacuum type circuit interrupter as claimed in claim 8 wherein a portion of said first set of arcing rails are separated from said second contact support means by a distance less than the arcing gap; and

a portion of said second set of arcing rails are separated from said first contact support means by. a distance less than said arcing gap. 10. A vacuum type circuit interrupter as claimed in claim 8 including: I r are moving means formoving an are formed during circuit interruption between said arcing rails and said associated contact support means. 11. A vacuum type circuit interrupter comprising: a sealed highly evacuated insulating envelope; a first contact being relatively stationary and disposed within said evacuated envelope; a second contact being relatively movable between a position in engagement with said first contact and a position spaced from said first contact to form an arcing gap therebetween in which an arc is formed during circuit interruption and .being disposed within said evacuated envelope; a first contact support means to which said first contact is secured for supporting said first contact;

are moving means for moving said are formed during,

circuit interruption from the single arcing gap to a position between the arcing rails of one contact and the support means for the other contact so that the arc is disposed in a generally radial alignment. 12. A vacuum type circuit interrupter as claimed in claim 11 wherein;

a portion of said first set of plurality of arcing rails are spaced from said second contact support means by a djistance less than the length of the arcing gap; an a portion of said second set of plurality of arcing rails are spaced from said first contact support means by a distance less than the length of the arcing gap.

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US2067529 *Feb 20, 1934Jan 12, 1937Bell Telephone Labor IncElectron discharge device
US3008022 *Jun 15, 1960Nov 7, 1961Gen ElectricContact structure for a vacuum-type circuit interrupter
US3185798 *Oct 8, 1962May 25, 1965Gen ElectricElectric circuit interrupter of the vacuum type with series-related arcing gaps
US3321598 *Nov 16, 1964May 23, 1967Gen ElectricVacuum-type circuit interrupter with arc-voltage limiting means
US3575564 *Sep 10, 1969Apr 20, 1971Allis Chalmers Mfg CoVacuum-type electric circuit interrupter
US3643047 *Dec 10, 1970Feb 15, 1972Gen ElectricSeries double break rod array vacuum switch
US3705144 *Dec 15, 1971Dec 5, 1972Battelle Memorial InstituteVacuum interrupter or switch for electric power networks
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US4029921 *Jul 1, 1975Jun 14, 1977General Electric CompanyVacuum-type circuit interrupter with two sets of contacts electrically in parallel
US5387771 *Apr 8, 1993Feb 7, 1995Joslyn Hi-Voltage CorporationAxial magnetic field high voltage vacuum interrupter
DE3112407A1 *Mar 28, 1981Apr 8, 1982Calor Emag Elektrizitaets AgSwitching contact for vacuum switches
WO1994024687A1 *Apr 4, 1994Oct 27, 1994Joslyn Hi Voltage CorpAxial magnetic field high voltage vacuum interrupter
Classifications
U.S. Classification218/118, 313/306, 218/123, 313/305, 200/239, 315/35
International ClassificationH01H33/66, H01H33/664
Cooperative ClassificationH01H33/6646
European ClassificationH01H33/664F