High-voltage switches with arc preventing or extinguishing devic – Arc preventing or extinguishing devices – Vacuum
Patent
1995-12-15
1997-08-26
Gellner, Michael L.
High-voltage switches with arc preventing or extinguishing devic
Arc preventing or extinguishing devices
Vacuum
218136, H01H 3366
Patent
active
056612818
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates generally to the field of electrical components and more particularly to the structural design of vacuum-type interrupters, whose housings are comprised of two cap-like metal parts and of an annular insulator and whose intended purpose, therefore, is for switching in a low-voltage range.
In the case of a known vacuum-type interrupter, which is used as a protective tube and, thus, for switching currents on the order of magnitude of 1 to 2 kA for voltages of up to about 1000 V, the housing enveloping the stationary contact and the contact that is axially movable thereto is comprised of two cap-like metal parts and of an annular insulator, to which the two cap-like metal parts are hermetically sealed by means of a knife-edge soldered joint. The stationary and the movable contact member, a cylindrical shield covering the annular insulator, and the bellows associated with the movable contact stud are disposed axially one behind the other inside the housing. The bellows is brazed with its one end to the supporting disk connected to the movable contact stud (EP 0 254 089 A1).
In the case of another known vacuum-type interrupter for the low voltage range, no cylindrical shielding is provided, but rather a cap-like protective shield that opens toward the bellows. In this case, the annular insulator, whose wall thickness is nearly equal to its axial length, is disposed concentrically to the bellows (EP 0 054 670 A2).
In the case of other vacuum-type interrupters used in the middle voltage range, it is likewise known to arrange a cap-shaped protective shield between the contact member and its rear space, in particular also between the movable contact member and the bellows associated with the movable contact, this protective shield protecting the bellows and, in some instances, an associated hollow cylindrical or disk-shaped insulating part from the condensing of vaporized electrode material (U.S. Pat. Nos. 3,674,958; 3,996,437; 4,417,110).
Another vacuum type interrupter switches d.c. currents up to about 6 kA given a d.c. voltage of up to 10 V. in that case one or both contacts have assigned to them a cap-like protective shield, which opens toward and projects over the arc gap and which shields the hollow cylindrical insulator disposed concentrically to the arc gap (U.S. Pat. No. 4,216,360 A1).
SUMMARY OF THE INVENTION
The invention is based on a vacuum-type interrupter that achieves the objective of having the smallest possible axial and radial dimensions, while being able to reliably switch short-circuit currents in the range of 50 to 100 kA.
To achieve this objective, the invention provides for a cap-like metal part allocated to a movable contact stud to be joined to the insulator in the outer area of an end face by a knife-edge soldered joint, for the bellows to be soldered with its one end in the immediate vicinity of the movable contact member to its contact stud, and for a cap-shaped protective shield open toward the arc gap to be disposed at the base of the movable contact member, said protective shield surrounding with its rim the base area of the contact member, the radial clearance of the shield rim from the periphery of the contact member amounting more or less to 2 to 4 mm and the height of the shield rim in the axial direction of the contact member amounting to at least about 4 mm, and being so dimensioned that any partial arcs that might be struck, whose roots at the outer wall of the movable contact member tend to migrate toward the contact stud, are confined to the zero-field space formed by the cap-shaped protective shield.
When a vacuum-type interrupter of such a design is used, it is possible to do without a special shield for protecting the inner insulating clearance formed by the annular insulator, since a relatively widely shaped end face of the annular insulator is turned away from the contact region. If need be, this insulating clearance can be extended by an axial groove. In addition, by arranging the annular insulator concentrically to
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patent: 4216360 (1980-08-01), Cherry et al.
patent: 4417110 (1983-11-01), Yanagisawa et al.
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Fieberg Klemens
Kusserow Jorg
Oberndorfer Klaus
Renz Roman
Friedhofer Michael A.
Gellner Michael L.
Siemens Aktiengesellschaft
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