High-voltage switches with arc preventing or extinguishing devic – Arc preventing or extinguishing devices – Operating mechanism structure or arrangement
Reexamination Certificate
2001-04-04
2002-04-16
Donovan, Lincoln (Department: 2832)
High-voltage switches with arc preventing or extinguishing devic
Arc preventing or extinguishing devices
Operating mechanism structure or arrangement
C218S157000, C335S202000
Reexamination Certificate
active
06373016
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a low-voltage limiting electrical power circuit breaker.
The document U.S. Pat. No. 5,694,098 describes a limiting circuit breaker whose poles comprise a stationary contact and a movable contact situated at the inlet of an arc extinguishing chamber. The contacts are laterally bounded by the branches of a U-shaped magnetic circuit designed to produce a magnetic field tending to drive the movable contact in which a current is flowing to a separated position. An insulating shield is placed between the U-shaped magnetic circuit and the contacts, the side walls of the insulating shield forming a passage between the contact area and the inlet opening of the chamber.
For this type of apparatus, difficulties arise when short-circuit current breaking tests are performed with a relatively high voltage, for example at 100 kA with a voltage of about 600 Volts. This is due to the fact that, for high-rating limiting apparatuses of this type, it is difficult to obtain a high arc voltage, of about 600 to 700 Volts peak, in a small volume. The number of contact fingers and the width of the fingers are in fact conditioned by the rating of the apparatus, i.e. by the nominal value of the current intensity which is accepted by the apparatus. It then follows that when the rating of the apparatus is high, the side walls of the pole are at a fairly large distance from one another and do not enable an optimal heat exchange to be achieved with the electric arc. This deficit is then compensated by increasing the arc length, and therefore the distance between the stationary and movable contacts in the separated position, and by increasing the dimensions of the arc extinguishing chamber. The dimensions of the apparatus are therefore increased.
U.S. Pat. No. 2,555,993 describes a switch designed to interrupt the power supply of an inductance of a circuit breaker control circuit, this inductance having a direct current of about 200 A flowing through it. The switch comprises a stationary contact, a movable contact, an expansion chamber containing an inlet orifice and no outlet orifice, and a discharge stack situated between the contacts and the chamber inlet. The contacts are located in a passage whose width decreases from the contact area to the chamber inlet opening. The walls of this passage are made of an insulating material formed by phosphoreted asbestos in a 90% zircon substrate. The side walls of the passage are laterally bounded by two metal plates which form part of a U-shaped magnetic circuit excited by a winding so as to produce a magnetic field tending to displace the arc to the expansion chamber. When opening of the contacts takes place, the electric arc is propelled at high speed in the direction of the expansion chamber due to the magnetic field. When passing through the narrow part of the passage, the arc is subjected to constriction and cooling, due to the interaction with the walls of the passage. The ionized hot gases produced are outlet via the discharge stack and do not hinder the progression of the arc to the expansion chamber, so that the flames are confined in this chamber and are not discharged to the atmosphere. Expansion in the expansion chamber contributes to cooling the arc and to causing extinguishing thereof. Once the arc has been extinguished, the residual gases accumulated in the expansion chamber are outlet via the discharge stack. The object here is to increase the arc voltage until it exceeds the voltage at the terminals of the inductance in the course of discharge. The breaking performances of the apparatus are very low and dictated by the application, as the arcing current intensity never exceeds the initial value of 200 A, and the maximum dissipated energy corresponds to the energy stored in the inductance. Furthermore, the architecture of the apparatus is not transposable to a low-voltage limiting power circuit breaker, notably due to the hot exhaust gases discharged via the stack. Consequently, the teachings of this document do not appear to be transposable to low-voltage limiting power circuit breakers of the previously described type.
A power switch is described in the Patent DE 728,612. This switch comprises a stationary contact and a movable contact arranged in an arc extinguishing chamber formed by a volume containing the contacts, extended by a narrow slit which opens out, opposite the volume containing the contacts, on an open external space. The arc extinguishing chamber is bounded laterally by ceramic walls which are a relatively distant from one another at the level of the volume containing the contacts, move progressively towards one another to form a restriction at the entrance to the slit and are extended parallel to one another all along the slit. Two arcing horns extend from the volume containing the contacts to the opposite end of the slit, moving away from one another. Lateral blowing plates surround the ceramic side walls and constitute a magnetic arc blowout circuit. On opening of the contacts, the electric arc is blown magnetically into the slit. The divergent arrangement of the arcing horns is essential to compensate, or even over-compensate, the reduction of the cross-section for passage of the breaking gases to the outside. Movement of the arc inside the chamber is thus not hampered by a pressure increase. As it progresses into the slit, the arc finds new ceramic surfaces enabling a large heat exchange to take place. High-speed movement of the arc until the latter is extinguished avoids a too great local exposition in the chamber. The dimensions of this apparatus are very large. The length of the slit from the contacts to the opening onto the outside space must in fact be sufficiently great to enable the arc to be extinguished before it reaches the extremity of the chamber. In like manner, the distance between the arcing horns near to the opening to the outside is also very large, since it results from the continuous divergence between the arcing horns necessary to counteract the pressure increase due to the narrowing of the cross-section of the slit. In practice these constraints moreover impose an opening angle of about 120° between the arcing horns. Consequently, this technology would appear to be incompatible with the pursuit at the same time to achieve compactness and high breaking performances.
U.S. Pat. No. 2,970,197 describes a switch comprising a stationary contact means comprising a stationary main contact, a stationary secondary contact and a stationary arcing contact, operating in conjunction with a movable contact means bearing, on a single pivoting arm, a movable main contact, a movable secondary contact and a movable arcing contact. An arc extinguishing chamber equipped with separators is situated between the lateral branches of a U-shaped magnetic circuit. The contacts are situated in a passage which narrows progressively towards the chamber inlet. The magnetic circuit is supplied by a coil, serially connected between the stationary main contact and a lower arcing horn. Opening takes place in several stages: in a first step, the main contacts, situated at a relatively large distance from the arc extinguishing chamber, separate forcing the current to flow in the secondary contacts located closer to the chamber. In a second step, the secondary contacts also separate forcing the current to flow in the arcing contacts situated close to the chamber. A primary electric arc then arises between the arcing contacts when the latter separate. The arc lengthens and reaches the lower arcing horn dividing into two secondary arcs in series: a first secondary arc between the stationary contact and the lower arcing horn and a second secondary arc between the lower arcing horn and the movable arcing contact. As soon as the first secondary arc is drawn between the stationary arcing contact and the lower arcing horn, the magnetic circuit excitation coil is supplied. The impedance of the coil winding being lower than that of the first secondary arc, this arc is extinguished so that the whole of t
Brouillat Alain
Pellegrin Lucas
Rival Marc
Donovan Lincoln
Nguyen Tuyen
Parkhurst & Wendel L.L.P.
Schneider Electric Industries SA
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