US3866005A - Arc electrode structure, especially for vacuum switches - Google Patents

Abstract

An arc electrode structure, especially for vacuum switches, comprising two oppositely situated electrodes for taking-up the base points of the arcs and formed of a number of plates. The narrow surfaces of the plates are disposed to confront the oppositely situated electrodes. Gaps or spaces are maintained free between the individual plates, the width of such gaps being at least equal to the thickness of a plate. A further feature of the invention contemplates rigidly electrically conductively connecting the plates with contact elements or pieces.

Description

United States Patent 11 3,866,005 Amsler Feb. 11, 1975 ARC ELECTRODE STRUCTURE, 3,773,993 11/1973 Amsler 200/144 13 ESPECIALLY FOR VACUUM SWITCHES FOREIGN PATENTS OR APPLICATIONS [75] Inventor: Joachim Amsler, Unterentfelden, 1,389,836 1/1965 France 200/144 B Switzerland 1,210,600 10/1970 Great Britain 200/144 B 224,964 2/1969 Sweden 200/144 B 1 Asslgheel P f & Sehhh Aer", 451,286 5/1968 Switzerland 200/144 B swltzerland 460,122 9/1968 Switzerland 200/144 B '22 F! d: M 23, 1973 1 l e ay Primary Examiner--Robert S. Macon PP 363,048 Attorney, Agent, or Firm-Waters, Roditi, Schwartz & Related US. Application Data N'ssen v [63] Continuation-impart of Ser. No. 232,480, March 3,

1972, Pat. No. 3,773,993. [57] ABSTRACT An arc electrode structure, especially for vacuum [30] Foreign Application Priority Data switches, comprising two oppositely situated elec-' June 22, 1972 Switzerland 9398/72 "Odes for -"P the base Points of the ares and formed of a number of plates. The narrow surfaces of 52 us. c1. 200/144 B, 200/275 the Plates are disposed to eehheht the oppositely Situ- [51] Int. Cl. H0lh 33/66 ated elctrodes- Gaps or Spaces are maintained free [58] Field of Search 200/144 B, 166 BH, 275. between the individual P the width of Such gaps being at least equal to the thickness of a plate. A fur- [56] References Cited ther feature of the invention contemplates rigidly elec- UNITED STATES PATENTS trically conductively connecting the plates with t t l t 3,210,505 10/1965 Porter ZOO/144 B con ac e emen S pieces 3,261,954 7/1966 Yonkers 200/144 B 9 Claims, 12 Drawing Flgures PATENTEDFEBHI975 I 3.866005 SHEET 10F 5 boom oo-" lU w PATENTEDFEBI 1191s a 866 005 SHEET 20F 5 15 lfflllll v16 Fig.4 Y

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ARC ELECTRODE STRUCTURE, ESPECIALLY FOR VACUUM SWITCHES REFERENCE TO RELATED CASE This is a continuation-in-part of commonly assigned United States application Ser. No. 232,480 filed Mar. 3, 1972 now issued as US. Pat. No. 3,773,993.

BACKGROUND OF THE INVENTION the switching element, the plates being assembled together into a rigid package and these plates alternately consist of two materials of different electrical conductivity. The infeed of current to the base points of the are displaced radially outwardly at the arc electrode preferably occurs at the plates possessing the better electrical conductivity so that the thus produced arcshaped current paths exert a tangential acceleration force upon the arc. As a result, the arc rotates at the outer periphery of the arc electrode about the contact axis until it is extinguished. Owing to the rapid movement of the base points of the arc there isprevented undesired, high local heating of the contact surfaces. A drawback with this arrangement is that for cut-off or interruption currents exceeding about 5 l0 kA, the contact burn-off is relatively great so that the longevity of the vacuum switch is reduced for high cut-off currents.

Experiments have shown that the arc between largesurface electrodes, such as, for instance,-between the previously mentioned arc electrodes, can burn'in two different conditions. Below SkA the arc burns in a diffuse or scattered manner. If this current boundary or limit is exceeded then there prevails a column or-pillar arc. The contact burn-off for column arcs is considerable and therefore the longevity of the vacuum switch is also reduced. A diffuse arc does not cause any appreciable contact burn-off. For the purpose of obtaining the diffuse region of the arc, there is known in the art a solution in which the arc burns and travels between two coaxial cylinders. A drawback of this solution is, however, that the ionized gas during cut-off of the switch remains between both oppositely situated electrodes and it is difficult to extinguish the arc.

According to a further known proposal in the art, there is provided two bowl-shaped electrodes disposed in confronting arrangement, each electrode being provided with an inwardly turned or flanged lip portion bounding an opening, the openings of the bowl-shaped electrodes confronting one another. With this proposal the ionized gas from the space between the electrodes is collected in the spaces of the bowl-shaped electrodes which are not electrically loaded, cooled and condensed. A drawback of this arrangement is that between the bowl-shaped electrodes there also appears a column are when exceeding approximately kA cut- -off currents, bringing about marked contact burn-off.

SUMMARY OF THE INVENTION Hence, from what has been discussedabove it will be recognized that the technology in this particular field is still in need of arc electrode structures, especially for vaccum switches, not associated with the aforementioned drawbacks and limiations of the prior art proposals. It is therefore a primary'object of the present invention to fulfill the existing need in the art.

Another and more specific object of the present invention relates to is to provide a new and improved construction of arc electrode rendering possible maintenance of the diffuse range of the are also when exceeding approximately 5 l0 kA cut-off current values.

Yet a further object of the present invention aims at the provision of an arc electrode structure which possesses the advantages of arc electrodesformed of plates arranged with intermediate gaps or spaces and which can be directly employed as a contact element.

Now in order to implement these and still further objects of the invention, which will become more readily apparent as the description proceeds, the invention contemplates leaving spaces or gaps free between the individual plates, the width of suchspaces or gaps being at least equal to the thickness of a plate. A particularly advantageous arrangement of the plates is then realized if the plates are radially arranged about an axis common to both oppositely situated electrodes.

According to a further feature of the invention and to permit the arc electrode structure to be employed directly as a contact element or piece, the plates are rigidly electrically conductively connected with contact elements.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be better understood and objects other than those set forth above, will become apparent when consideration is given to the following detailed description thereof. Such description makes referenceto the annexed drawings wherein:

FIG. 1 is a longitudinal sectional view through a preferred constructional form of inventive vacuum switch embodying the teachings of this development;

FIG. 2 is a transverse cross-sectional view taken through the center of the vacuum switch depicted in FIG. 1, taken substantially along the line lI-ll thereof;

FIG. 3 illustrates details of an electrode construction consisting of parallel plates;

FIG. 4 illustrates details of an electrode construction consisting of coaxial cylinders;

FIG. 5 illustrates details of an electrode construction formed of flexed or angled plates;

FIG. 6 schematically illustrates a portion of the surface of an electrode;

FIG. 7 schematically illustrates, partially in sectional view, an arc electrode with a substantially cylindrical tubular-shaped contact element or piece;

FIG. 8 illustrates one-half of the structure depicted in FIG. 7 in plan view;

FIG. 9 is a sectional view of vacuum switch embodying teachings of this development;

FIG. 10 illustrates an arc electrode in plan view as employed in the vacuum switch depicted in FIG. 9;

FIG.- 11 illustrates in side view a further embodiment of arc electrode with contact elements or pieces forming a loop; and i FIG. 12 is aplan view of the structure depicted in FIG. l1, illustratingthe upper arc electrode in section.

DETAILED DESCRIPTION OF THE PREFERRED a EMBODIMENTS Referring now to the drawings, in the illustration of the exemplary embodiment of vacuum switch as depicted in FIG. 1, the vacuum tight or sealed housing of the switch consists of a cylindrical portion 1 formed of electrically insulating material, a metallic cover member 2 with a switching element or piece 3 fixedly seated therein and a tubular-shaped electrode support or carrier 4 vmounted thereon, and a second metallic cover member 5 which carries a switching element or piece 7 and electrode support 8, the switching element 7 being secured so as to be movable via a diaphragm or bell'ows 6 with the metallic cover member 5. The movable switching element 7 has been illustrated in its switching-in or connection position and can be moved -to-and-fro in the direction of the arrow by means of any suitable and therefore non-illustrated actuation mechanism. The'electrodesupports 4 and 8 carry radially arranged plates 9 and l0 of the arc electrode structure.

In this connection reference should also be made to FIG. 2. The inner surface of the cylindrical portion 1 is protected against condensation "of the metal vapors which are present by means of a'tubular-shaped metal shield 11 which is only secured to the center of the cylindrical part 1 and thus completely insulated from' both metallic cover members 2 and 5.

The switching elements or pieces 3 and 7 possess a truncated or blunt contact support surface 12. During disconnection of the current, the switching elements 3 and 7 separate and the are initially burns therebetween. The base points of the are then wander over to the plates 9 and 10, wherein the delivery of current occurs by means of' both electrode supports 14 and 8. The are burning between the electrodes formed of the plates arranged so as to have therebetween intermediate compartments or spaces is practically not ableto build-up anaxial pressure or force because the axially accelerated ionized gases in the spaces between the plates arrivesat'a compartment or space which is not electrically loaded. The hot gases flowing through the spaces between the plates 9 and 10 are cooled and condensed.

The are burns in a diffuse or scattered manner between the thus constructed electrodes up to very. large values of cut-off or interruption current, considerably exceeding 5 l0 kA. The gaps or spaces formed between the plates 9 and 10 and the very narrow surfaces ofitheplates 9 and l0confronting the opposed electrodes prevent the formation of column arcs and therefore increase the longevity of the vacuum switch.

Now as best seen by referring to FIG. 3, it will be recognized that the oppositely situated electrodes could also be formed of parallel arranged plates 13. As is to be further understood the plates 13 of the arrangement of FIG. 3 are inserted into slots 14a of the electrode support 14 and welded or. riveted thereat.

. In FIG. 4 there is shown a further construction of the electrodes wherein the latter are assembled together from concentric cylinders 15 secured to electrode supports 16.

In the arrangement of FIG. 5, flexed or angled plates 18 and 19, which aresituated parallel tothe axis 17 (FIG. 1) which is common to both oppositely situated electrodes, are mounted on the electrode support 4. This construction also brings about atangential acceleration of the burning are between the electrodes.

An essential criteria for maintaining a diffuse are between the electrodes consisting of adjacently arranged plates with free intermediate spaces therebetween concerns the sum of the length of the edges appearing at one square centimeter of electrode surface. Experience has shown thatthe sum of the edge length should at least amount to 3 cm. per squarejcentimeter of electrode surface. In FIG. 6 there is illustrated'an embodiment wherein they sum of the edge lengths of the plates 20, 21 and 22 amounts to 6 cm. for a square centimeter of electrode surface. I a

The diffuse are not only has its arc projection surface at the narrow surfaces of theplates confronting the oppositely situated electrodes, but also at the wide surfaces of the plates bounding the spaces or gaps between the plates. In order tomaintain the diffuse region of the arc for cut-off currents exceeding 5 10, kA, experience has shown that the dimensions 23 (FIG. 1) of the plates below the narrow surfaces confronting the oppositely situated electrodes must amount to at least 1 cm.

The are electrodes described in conjunction with FIGS. 1 to 6 are not constructed as'c'ontact pieces or elements. When the switch is'closed, the current is conducted via an auxiliary contact bridgingthe'arc elec trode, this auxiliary contact being opened during the cut-off operation. The are thus commutates during the extinguishing operation from the auxiliary contact to the arc electrodes, where it is extinguished. While the previously discussed embodiments provide notable advantages, it still has been found that a drawback of such Therefore, considering. the arc electrode structure depicted in FIG. 7, it will be understood that such is providedfor a vacuum switch and consists of a cylindrical, tubular-shaped contact element or piece 41 and plates 43 constructedas an arc electrode and inserted in slots 42 of the contact element or'piece'4l; The plates 43 are introduced into the slots 42 and the parts of the slots 42 located directly beneath the contact surface 44 and not occupied by the plates 43 are tamped or peened over. This mode of attachment of the plates 43 provides advantageouseconomical fabrication of the arc electrode. The plates 43 are rigidly electrically conductively connected with the contact element 41. The contact surface 44 protrudes pastthe narrow surfaces of the plates 43. In order to obtain good. extinv guishing characteristics, the plates 43 must extend into one of the two are electrodes which are arranged in a vacuum switch in confronting relationship and relatively movable with respect to one another, as discussed above.

The contact element 41 consists of copper, but also can contain slight amounts of bismuth, beryllium, lead or tin. These additive materials prevent welding of the abutting contact surfaces 44 when conducting greater currents.

The plates 43 consist of iron, but also could be fabricated from nickel, chromium, chromium-nickel, molybdenum, tantalum, or tungsten. Prior to assembly into the vacuum switch, the plates vcan be degassed. Non-degassed plate electrodes possess in a vacuum, about times less burn-off than compact electrodes. Degassed plate electrodes, on the other hand, in relation to the non-degassed plate electrodes, possess five times less burn-off.

Upon opening a vacuum switch equipped with the arc electrodes of the type depicted in FIG. 7, there initially prevails between the contact surfaces 44 an arc ring. The arc commutates under the action of its inherent magnetic field from the contact surfaces 44 to the narrow surfaces of the plates 43, where it burns diffusely up to the time that it extinguishes. With the described arc electrode arrangement there can be attained for the vacuum switch a considerable increase in the maximum permissible cut-off current.

FIG. 9 illustrates a vacuum switch comprising a housing composed of metal covers 55, metallic bellows or diaphragm 56, the insulating cylinder 57, and metallic shield 58, this vacuum switch further including two are electrodes arranged internally of the housing. One arc electrode is rigidly connected with the lower metallic cover member 55. The other arc electrode is movable externally of the switch housing via the metallic bellows 56, as previously discussed.

The arc electrodes consist of both upright arranged U-shaped profile members 59 and the intermediately disposed parallel plates 50. In FIG. 10 there is illustrated the lower arc electrode in plan view. The plates 50 possess indented portions or impressions 51 forming projections which bear against their neighboring plate, so as to insure a desired spacing between the plates 50 in the presence of the forces of the parallel current paths in these plates 50. The plates 50 are inserted into the aforementioned slots of such U-shaped profile members 59 and, as explained above, these slots are tamped or peened over. When the switch is closed, the contact surfaces 52 of the U-shaped profile members 59 bear against one another. The contact surfaces 52 protrude past the narrow surfaces of the plates 50. After separation of the U-shaped profile members 59 an arc is formed at the separation location, and such arc commutates at the plates 50. As experience has shown, the arc burns in the entire space between the end surfaces of the plates 50 of both arc electrodes where it then is extinguished.

FIGS. 11 and 12 illustrate two are electrodes and specifically FIG. 11 is a side view and FIG. 12 a plan view, wherein the upper arc electrode has been depicted in sectional view in FIG. 12. The contact elements or pieces 63 and 64 form a loop for the current. The plates 65 and 66 attached to the contact elements 63 and 64 are provided for the purpose of current infeed to the arc burning between the plates 65 and 66 after separation of the contact elements 63 and 64 and for extending or enlarging the current loop. After separation of the contact elements 63 and 64, the arc is attenuated and extinguished between the plates 65 and 66 arranged at an increasing spacing in the driection of travel of the arc. Through suitable selection of the length of the plates and the angle between the narrow surfaces of the oppositely situated or confronting plates 65, 66 it is possible to arrive at an arrangement which insures that the arc will be extinguished in the presence of currents which occur in practice for almost all operations.

In order to counteract the tension force prevailing between the parallel arranged plates in the presence of high currents, the plates 65 and also the plates 66 are supported against one another by the impressions 67 provided at the plates 65, 66.

In the case where the contact surfaces of the contact elements 63 and 64 bear against one another, the plates 65 and 66 engage in a comb-like fashion with one another at the region of the contact surfaces. The overlapping of the plates 65 and 66 is smaller than the full or maximum opening distance of the contact element 63'. This arrangement renders more favorable the commutation of the arc from the contact elements 63, 64 to the plates 65, 66.

The use of the inventively constructed arc electrodes is not solely limited merely to vacuum switches, although such constitutes a particularly useful environment.

While there is shown and described present preferred embodiments of the invention, it is to be distinctly understood that the invention is not limited thereto but may be otherwise variously embodied and practiced within the scope of the following claims.

What is claimed is:

I. An arc electrode arrangement, particularly for vacuum switches comprising two oppositely located electrode assemblies, each electrode assembly including a separation contact and arcing means having an arcing face to take up the base points of the arc, said arcing means comprising a plurality of plates separated from one another by gaps therebetween, said plates extending substantially parallel to the axis of the respective separation contact, the width of said gaps being at least equalto the thickness of a plate, the edges of the plates defining said arcing face, means rigidly connecting the plates of each respective electrode assembly directly with the respective separation contact in electrically conductive fashion, said plates being so arranged in the electrode assemblies that upon closed contact the plates of one of the electrodes assembly are not in direct contact with the plates of the other electrode assembly, said separation contact having a contact surface projecting beyond the narrow end surfaces of said plates towards the other electrode assembly.

2. An arc electrode arrangement as claimed in claim 1, wherein each'separation contact comprises at least one upright profile member which contacts by means of an end face thereof, in a closed position of the electrode assemblies, the end face of the oppositely situated separation contact.

3. An arc electrode arrangement as claimed in claim 2, wherein said separation contacts form a current loop, said plates being arranged as extensions of such loop.

4. An arc electrode arrangement as claimed in claim 1, wherein each separation contact is provided with slots, said plates being mounted in said slots, said separation contact including peened-over portions above said slots to hold said plates therein.

5. An arc electrode arrangement as claimed in claim 1, wherein each separation contact comprises a tubular member and said plates are arranged at least in part internally in said tubular member.

6. An arc electrode arrangement as claimed in claim 5, wherein said tubular member is of substantially cylindrical configuration and said plates are rigidly arranged in such substantially cylindrical tubular member.

7. An arc electrode arrangement, particularly for vacuum switches comprising two oppositely located electrode assemblies, each electrode assembly including a separation contact and arcing means having an arcing face to take up the base points of the arc, said arcing means comprising a plurality of plates separated from one another by gaps therebetween, said plates extending substantially parallel to the axis of the respective separation contact, the width of said gaps being at ing the plates of each respective electrode assembly directly with the respective separation contact in electrically conductive fashion, said plates being so arranged in the electrode assemblies that upon closed contact the plates of one of the electrodes assembly are not in direct contact with the plates of the other electrode assembly, said plates being arranged on their respective separation contact to interengage the plates of the other electrode assembly in comb-like fashion in closed position of the electrode assemblies and wherein said plates have a degree of overlap which is less than the maximum open spacing between the separation contacts.

8. An arc electrode arrangement as claimed in claim 7, wherein each separation contact comprises at least one upright profile member which contacts by means of an end face thereof, in a closed position of the electrode assemblies, the end face of the oppositely situated separation contact.

9. An arc electrode arrangement as claimed in claim 8, wherein said plates extend transversely of said profile members.

Claims (9)

1. An arc electrode arrangement, particularly for vacuum switches comprising two oppositely located electrode assemblies, each electrode assembly including a separation contact and arcing means haviNg an arcing face to take up the base points of the arc, said arcing means comprising a plurality of plates separated from one another by gaps therebetween, said plates extending substantially parallel to the axis of the respective separation contact, the width of said gaps being at least equal to the thickness of a plate, the edges of the plates defining said arcing face, means rigidly connecting the plates of each respective electrode assembly directly with the respective separation contact in electrically conductive fashion, said plates being so arranged in the electrode assemblies that upon closed contact the plates of one of the electrodes assembly are not in direct contact with the plates of the other electrode assembly, said separation contact having a contact surface projecting beyond the narrow end surfaces of said plates towards the other electrode assembly.

2. An arc electrode arrangement as claimed in claim 1, wherein each separation contact comprises at least one upright profile member which contacts by means of an end face thereof, in a closed position of the electrode assemblies, the end face of the oppositely situated separation contact.

3. An arc electrode arrangement as claimed in claim 2, wherein said separation contacts form a current loop, said plates being arranged as extensions of such loop.

4. An arc electrode arrangement as claimed in claim 1, wherein each separation contact is provided with slots, said plates being mounted in said slots, said separation contact including peened-over portions above said slots to hold said plates therein.

5. An arc electrode arrangement as claimed in claim 1, wherein each separation contact comprises a tubular member and said plates are arranged at least in part internally in said tubular member.

6. An arc electrode arrangement as claimed in claim 5, wherein said tubular member is of substantially cylindrical configuration and said plates are rigidly arranged in such substantially cylindrical tubular member.

7. An arc electrode arrangement, particularly for vacuum switches comprising two oppositely located electrode assemblies, each electrode assembly including a separation contact and arcing means having an arcing face to take up the base points of the arc, said arcing means comprising a plurality of plates separated from one another by gaps therebetween, said plates extending substantially parallel to the axis of the respective separation contact, the width of said gaps being at least equal to the thickness of a plate, the edges of the plates defining said arcing face, means rigidly connecting the plates of each respective electrode assembly directly with the respective separation contact in electrically conductive fashion, said plates being so arranged in the electrode assemblies that upon closed contact the plates of one of the electrodes assembly are not in direct contact with the plates of the other electrode assembly, said plates being arranged on their respective separation contact to interengage the plates of the other electrode assembly in comb-like fashion in closed position of the electrode assemblies and wherein said plates have a degree of overlap which is less than the maximum open spacing between the separation contacts.

8. An arc electrode arrangement as claimed in claim 7, wherein each separation contact comprises at least one upright profile member which contacts by means of an end face thereof, in a closed position of the electrode assemblies, the end face of the oppositely situated separation contact.

9. An arc electrode arrangement as claimed in claim 8, wherein said plates extend transversely of said profile members.

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