Gas-blast Circuit Breaker With Double-nozzle Contact System

Abstract

A gas-blast circuit breaker includes within a contact chamber which is filled with a pressurized arc extinguishing gas a hollow shaft rotatable about its axis, a pair of normally open power switching contact structures located at opposite sides of the shaft and which are connectable temporarily in series during an opening operation of the breaker, and a normally closed supplementary switching means of the knife blade type arranged in a current path electrically in parallel with the power switching contact structures. Each of the power switching contact structures includes a movable contact carried by the rotatable shaft and a nozzle communicating with the interior of the shaft for carrying off the flow of arc extinguishing gas when the movable contact disengages from its associated stationary contact, and the supplementary switching means includes a movable contact blade carried by the rotatable shaft in association with a stationary contact. The operating sequence of the switches during a circuit breaking operation is that when the hollow shaft is rotated, the circuit through the power switching contact structures is completed before the circuit through the supplementary switching means is opened thereby enabling the contacts of the latter to open in an arc-free manner and transfer the load current to the circuit through the then in series connected power switching contact structures.

Description

The present invention relates to a gas-blast circuit-breaker having a double-nozzle contact system, in which the extinction gas streams in the two nozzles are orientated opposite each other, the nozzle contact members being pivoted about an axis during making and breaking, and having a parallel current switching position, conducting operating current and being adapted to switch under no-current conditions.

The prior art discloses a gas-blast circuit-breaker having a contact system with two pivotable nozzle contact members. For the switching operation, the nozzle contact members are pivoted about an axis which is disposed outside the nozzle, the pivoting motion proceeding along a circular arc relative to which the nozzle axis forms a tangent (U.S. Pat. No. 3,454,734). The extinction gas flows in the nozzles are orientated opposite to each other and are allowed to escape through an exhaust valve disposed in the middle between the two nozzles. A further similar system with a pivotable nozzle contact bridge, high-pressure gas being supplied along the axis of rotation, is disclosed by the U.S. Pat. No. 3,327,082. Finally, parallel current switching positions, adapted to switch under no-current conditions, have been known for a considerable period in gas-blast circuit-breakers (see, for example, German, laid-open spec. Pat. No. 1,253,790).

SUMMARY OF THE INVENTION

It is the object of the present invention to provide a space-saving construction for a gas-blast circuit-breaker of the kind mentioned heretofore and which permits rapid motion of the contact members by virtue of a system designed for small inertia forces and therefore permits short switching periods to be obtained with a driving system of moderate complexity.

In accordance with the invention, this objective is attained by a circuit breaker structure which includes a contact chamber filled with a pressurized arc extinguishing gas, a hollow shaft located within the contact chamber and which is rotatable about its axis, and a pair of normally open power switching contact structures of the gas-blast type located at opposite sides of the hollow shaft, but which are connectible temporarily in series during an opening operation of the breaker. Each of the gas-blast contact structures includes a nozzle on and communicating with the interior of the shaft and a movable contact member arranged to temporarily engage a stationary contact member as the shaft is rotated to initiate a circuit opening operation, and the nozzles come into alignment with the stationary contact members as these contact members disengage to enable the arc extinguishing gas to flow from the chamber into and through the nozzles into and through the hollow shaft to a point of discharge. Moreover, normally closed supplementary switching means are arranged in a current path electrically in parallel with the normally open gas-blast contact structures, and the contacts of these switches, which are also actuated by rotation of the shaft, do not disengage until the temporary circuit through the power switching contact structures has been closed.

A representative embodiment of the invention will now be described in detail and is illustrated in the accompanying drawings wherein:

FIG. 1 is a sectional view taken along the longitudinal axis of the circuit breaker on line I--I of FIG. 2; and

FIG. 2 is a plan view of the circuit breaker contact structure itself, the circuit breaker chamber within which the contacts are housed and which is included in FIG. 1 being deleted.

With reference now to the drawings, the contact structure for the circuit breaker is located within a chamber 1 the walls of which are made from insulating material, and this chamber is filled with a pressurized gas obtained from a suitable gas source, not shown, which is in constant communication with the chamber. As shown in FIG. 2, the contact structure of the circuit breaker includes a pair of juxtaposed, U-shaped contact supports 2, 2' carried respectively by terminal contact members 2a, only the latter contact member correlated to contact support 2 being included in the drawing. Each leg of each of the U-shaped contact supports 2, 2' carries a pair of parallel spaced contact plates 3, 3' and each pair of these plates forms the stationary contacts of a knife switch. The movable contact of each knife switch is constituted by a knife blade 8, 8' carried by an electrically conductive hollow rotatable shaft 5 located intermediate the sets of contact plates 3, 3'. Thus there are four knife switches in all, S1 to S4, switches S1 and S2 being electrically in series and paralleled with switches S3 and S4 also connected in series. In the closed position of the circuit breaker, all four of these knife switches S1 to S4 are closed.

The power switching contact structure for the circuit breaker and with which a gas-blast is associated for interrupting the power current is constituted by two other switches S5 and S6 also connectible electrically in series. Switch S5 includes a stationary contact member 4 resiliently mounted on contact support 2 intermediate the two sets of contact plates 3, 3' of switches S1 and S3 and a movable contact structure carried by the rotatable shaft 5 comprising a nozzle 6 and arcuate contact member 7. Similarly, switch S6 includes a stationary contact member 4' resiliently mounted on contact support 2' intermediate the knife switches S2 and S4 and a movable contact structure carried by shaft 5 comprising a nozzle 6' and arcuate contact member 7'. Nozzles 6 and 6' face outwardly from and are located on opposite sides of the hollow shaft 5 and are aligned along an axis normal to the rotational axis of the shaft.

The end of the hollow shaft 5 is closed by a cover plate 11 and the interior of the shaft is divided longitudinally into two separate gas discharge passageways by means of a partition wall 9 which also mounts an auxiliary electrode 10 which is common to the two switches S5 and S6. As is evident from the drawings, one of these passageways serves for the discharge of gas from switch S5 as indicated by arrows 12a, and the other passageway serves to discharge gas from switch S6 as indicated by arrows 12b.

Opening and closing of the circuit through the breaker structure is effected by rotation of shaft 5 which is effected by any suitable type of drive, but which has not been illustrated in the interest of simplifying the drawings, and also because the details of the drive are not essential to an understanding of the invention.

As previously explained, when an electrical circuit is closed through the circuit breaker, the contacts of all four of the knife switches S1 to S4 are closed and this is indicated by position A of the knife blades 8 in FIG. 2. Also, as will be seen from FIG. 2, the arcuate contact member 7 of each switch S5, S6 is then in a position where it does not make contact with the correlated stationary contact member 4. Thus, all of the current is conducted through the electrically paralleled knife switch paths S1-S2 and S3-S4, and no current passes through the power interrupting switches S5 and S6.

When it is desired to open the circuit breaker, the hollow shaft 5 is rotated counterclockwise, as viewed in FIG. 1 towards position B. During this rotation, the arcuate contacts 7,7' engage their corresponding stationary contact members 4,4' before the knife blades 8,8' lose their contact with the contact plates 3, 3' and consequently all of the load current is then transferred in an arcless manner from the knife switches S1 to S4 to the power interrupting switches S5 and S6. As rotation of shaft 5 continues, the contacts of the knife switches open in a practically arc-free manner, followed shortly thereafter by disengagement of the arcuate contact members 7, 7' with their stationary contact members 4, 4' whereupon the power current is interrupted drawing arcs therebetween which are swept into the nozzles 6, 6' to electrode 10 partially by the magnetic effect and also by the flow of pressurized gas into these nozzles from the gas-pressurized chamber 1. This gas flow is initiated by employment of a conventional blast valve arrangement associated with the hollow shaft 5 and which is opened to a lower pressure region as the shaft 5 is rotated from the initial closed-circuit position and not later than when the contacts are separated. Optimum outward flow of the discharge gases through the nozzles 6, 6' obviously occurs when position B is reached, in which position, the two nozzles are centered with respect to the longitudinal axis of the contact system through the power interrupting switches S5, S6.

The partition wall 9 offers the obvious advantage of avoiding any interaction between the two gas flows from switches S5 and S6 as could be the case in the event that back-arcing should occur at either of these switches during the time the power currents were being interrupted.

As rotation of shaft 5 continues in the counterclockwise direction, for example, after the switching arcs become extinguished, contacts 7, 8 and 7', 8' ultimately reach position C which is 90.degree. away from the starting position, and which represents the full-open position of the circuit breaker, i.e., the optimum voltage isolation position since it is evident from FIG. 2 that the movable contact members of all of the switches S1 to S6 will then be farthest away from their respective stationary contact members.

Claims

We claim:

1. In a gas-blast circuit-breaker, the combination comprising a contact chamber filled with a pressurized arc extinquishing gas, a hollow shaft located within said contact chamber and which is arranged for rotation about its axis, a pair of normally open power switching contact structures of the gas-blast type located at opposite sides of said hollow shaft and which are connectible temporarily in series during an opening operation of said circuit breaker, each said contact structure including a nozzle communicating with the interior of said hollow shaft and a movable contact member arranged to temporarily engage and then be disengaged from a stationary contact member as said hollow shaft is rotated to initiate a circuit opening operation, each said movable contact member and the nozzle correlated therewith being spacially arranged on said shaft such that as the contact members disengage the nozzles come into alignment respectively with said stationary contact members for flow of arc extinguishing gas from said chamber into and through said nozzles into and through said hollow shaft for discharge, and normally closed supplementary switching means arranged in a current path electrically in parallel with said pair of series connectible power switching contact structures comprising movable contact means mounted on said hollow shaft and stationary contact means correlated therewith, the relative locations of the movable contact members of said power switching contact structures and of the movable contact means of said supplementary switching means on said hollow shaft being such that as said shaft is rotated the said temporary connection of said power switching contact structures in series takes place before the said supplementary switching means open.

2. A gas-blast circuit-breaker as defined in claim 1 wherein said hollow rotatable shaft includes a partition wall dividing the interior thereof into separate gas discharge passageways for the gas entering therein through said nozzles.

3. A gas-blast circuit-breaker as defined in claim 1 wherein said stationary contact members of said power switching contact structures are resiliently mounted.

4. A gas-blast circuit-breaker as defined in claim 1 wherein said normally closed supplementary switching means arranged in a current path electrically in parallel with said pair of series connectible power switching contact structures are constituted by knife switches the knives of which are mounted on said rotatable shaft.

5. A gas-blast circuit-breaker as defined in claim 4 wherein two sets of knife switches are provided respectively on opposite sides of said power switching contact structures, and each set of knife switches serves to close a current path electrically in parallel with said power switching contact structures.

6. A gas-blast circuit-breaker as defined in claim 5 wherein each set of knife switches includes two knife members located on and at opposite sides of said rotatable shaft.