High-voltage switches with arc preventing or extinguishing devic – Arc preventing or extinguishing devices – Operating mechanism structure or arrangement
Reexamination Certificate
1999-11-29
2001-09-04
Scott, J. R. (Department: 2832)
High-voltage switches with arc preventing or extinguishing devic
Arc preventing or extinguishing devices
Operating mechanism structure or arrangement
C218S143000
Reexamination Certificate
active
06284993
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a mechanism for inserting a resistor in an electrical switch during closure of said switch so as to limit the effects of the capacitive currents present on the line of the switch. More particularly, the invention relates to a mechanism for inserting a closure resistor for a high-voltage metal-clad circuit-breaker. This type of switch comprises a metal casing which extends in an axial direction, which is generally made of sheet aluminum, and is filed with a dielectric gas, and in which two moving contact assemblies are mounted to move in the axial direction, namely a moving permanent contact assembly and a moving arcing contact assembly. One of the two contact assemblies is semi-moving in that its displacement in the axial direction is co-ordinated with the displacement of the other contact assembly via a linkage or a motion-transferring system. In order to equip that type of switch with a mechanism for inserting a closure resistor while modifying the structure of the interrupting chamber of the switch as little as possible, provision is made to extend the semi-moving arcing contact with a metal rod that extends in the axial direction between the arcing contact and the resistor.
BACKGROUND OF THE INVENTION
Conventional mechanisms comprise a metal tube coaxial with the rod and mounted to slide in electrical contact thereon, and having an end that plugs onto a conductive plug of the switch so as to short-circuit the resistor. The end of the tube that plugs onto the conductive plug is formed of a thimble of flexible fingers. A spring is disposed between a first shoulder provided on the rod and a second shoulder provided in the tube so as to be compressed during a first stage of switch opening, and so as to exert a return force on the tube to displace it in said direction in order to separate it form the plug during a second stage of switch opening subsequent to the first stage. When the switch is closed, the thimble of fingers of the metal tube is plugged onto the conductive plug which is normally connected to a terminal of the switch. During opening, it is important that the thimble of fingers on the metal tube does not come unplugged from the conductive plug before the contacts of the switch are fully separated. That is why the mechanism for inserting the resistor is designed so that the force form the compressed spring always remains lower than the tube-unplugging force, the tube being unplugged by the rod of the semi-moving contact coming into abutment in the axial direction against the metal tube.
In addition to the fact that the force at the flexible fingers of the metal tube is difficult to control, wear on the fingers over time gives rise to a loss of reliability of the mechanism for inserting the closure resistor.
OBJECTS AND SUMMARY OF THE INVENTION
An object of the invention is to remedy those drawbacks.
To this end, the invention provides a mechanism for inserting a closure resistor for an electrical switch containing a semi-moving arcing contact mounted to be semi-movable in an axial direction and secured to a metal rod which extends in the axial direction between the arcing contact and the resistor, the mechanism comprising: a metal tube coaxial with the rod and mounted to slide in electrical contact thereon, and having an end that plugs onto a conductive plug of the switch so as to short-circuit the resistor; and a spring disposed between a first shoulder provided on the rod and a second shoulder provided on the tube to displace it in the axial direction in order to separate it from the plug during a second stage of switch opening subsequent to the first stage, the mechanism further comprising a system having at least one ball which locks the tube so as to prevent it from being displaced in the axial direction during the first opening stage, and which retracts during the second opening stage so as to release the tube so that it can be displaced in the axial direction.
REFERENCES:
patent: 4324959 (1982-04-01), Hall et al.
patent: 4338500 (1982-07-01), Pham Van et al.
patent: 2 553 926 A1 (1985-04-01), None
Alstom Holdings
Scott J. R.
Sughrue Mion Zinn Macpeak & Seas, PLLC
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