Abstract:
A puffer-type compressed-gas circuit-interrupter is provided having a tubular stationary and at least two movable contacts which draw at least two arcs within at least two regions in the interrupter. The two regions are connected by a series of insulating flow guides, tubular contacts, and an insulating nozzle to a single fluid motor which during contact opening, after a predetermined portion of the opening travel of the interrupter, provides a blast of puffer gas extinguishing the arcs.

Description:
TECHNICAL FIELD 
     This invention relates to electrical circuit interrupters and, more particularly, to a puffer circuit interrupter with enhanced power handling capability. 
     BACKGROUND OF THE INVENTION 
     The continued growth and industrialization of the country demands an increase in the amount of electrical power supplied. These higher urban load current densities in conjunction with the scarcity of available space for substation construciton in urban areas present a problem for power distribution systems. In the past, larger loads have been accommodated by increases in the size of substation circuit-breakers. However, for current connection and disconnection, it is desirable to replace these larger circuit-breakers with smaller devices to meet the increasing demand for electrical power. 
     Load-breaker-disconnecting-switches as a smaller alternative to the larger circuit-breakers are well known in the art. Some earlier load-breaker-disconnecting-switches employed a circuit interrupter electrically in series with a disconnecting switch and mechanically linked to operate in concert. This combination increased the current disconnecting capacity of the load-breaker-disconnecting-switch without a corresponding increase in size. 
     Modern high current circuit-breakers are reliable and perform their duties adequately. However, they are physically large and expensive. Where space is a limiting factor, circuit-breakers must acommodate current disconnection requirements in the available space or be replaced by a more space efficient current disconnecting device. Therefore, it is highly desirable to have circuit interrupters which have increased current connection and disconnection capability without increased physical size to replace the corresponding capacity circuit-breakers. 
     Over the past few years, the circuit interrupter coupled to a disconnecting switch combination has been replaced by a modern circuit interrupter which can connect and disconnect current without the necessity of a series disconnecting switch. This has been accomplished by constructing circuit interrupters which extinguish the arc drawn on disconnection with a jet of a highly insulating gas such as sulfur-hexafluoride. These circuit interrupters are called puffer-type circuit interrupters because of the jet or puff of gas used to extinguish the arc. Because the circuit interrupters are filled and sealed with a gas more insulating than air, a smaller contact distance is required to prevent further arcing once the initial arc is extinguished, therefore leading to smaller equipment. Circuit interrupting devices of this type are set forth in U.S. Pat. No. 3,943,314 which issued Mar. 9, 1976 to Frink, U.S. Pat. No. 4,000,387 which issued Dec. 28, 1976 to Milianowicz, U.S. Pat. No. 4,328,403 which issued May 6, 1982 to Frink et al., and U.S. Pat. No. 3,588,407 issued June 28, 1971 to Frink. 
     These patents disclose circuit interrupters which operate effectively in a confined space and have a low noise level during the interruption. However, the circuit interrupters taught by Frink and Milianowicz puff only a single volume of sulfur-hexafluoride gas upon a single arc to extinguish it. This puffer circuit interrupter design is limited because the volume of puffer gas can only cool and extinguish so many kilo amperes of arc current. Therefore, to increase the current interrupting capabilities of the prior art design, the volume of available puffer gas would have to be increased which would mean either an increase in the length of the interrupter, or an increased cross sectional area of the puffer mechanism leading to an increased diameter of the interrupter. It is desirable to have a puffer type circuit interrupter that has increased power disconnecting capacity yet without an increased physical size. 
     SUMMARY OF THE INVENTION 
     The present invention is provided to overcome one or more of the problems set forth above. According to the present invention, a puffer circuit interrupter has an insulating tube means having first and second spaced external terminal means thereon communicating with the internal portion of said tube means. A first electrical contact means is disposed within the tube means in electrical contact with the first external terminal means. A second electrical contact means is also disposed within the tube means in electrical contact with the second external terminal means. A third electrical contact means is disposed within the tube means and is movable relative to the first and second contact means. A fluid motor means is disposed upon the first contact means. The fluid motor means defines a chamber and has an opening therein which controllably communicates with at least a first arc region between the first and third contact means and at least a second arc region between the second and third contact means. Puffer gas, which is within the chamber, is forced to flow from the chamber through the opening into the first arc region as the first contact means disengages from the third contact means to extinguish an arc between the first and third contact means and serially into the second arc region to extinguish an arc between the second and third contact means. 
     The present invention handles increased current connection and disconnection requirements without an increase in physical size and can replace physically large circuit-breakers. This is accomplished by providing multiple arc regions within the puffer circuit interrupter. 
     By having multiple arc regions which are serially cooled by a common jet of puffer gas, the instant invention has the same arc extinguishing and hence current interrupting capability in the first arc region as previous circuit interrupters, plus the additional arc extinguishing and current interrupting capability of the additional arc region(s). The jet of puffer gas flows out of the first arc region serially into each additional region. Between arc regions the gas recovers most of its arc extinguishing properties and thus is able to extinguish the arcs in those regions(s) also. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     While the specification concludes with claims particularly pointing out and distinctly claiming the subject matter which is regarded as the invention, it is believed that the invention will be better understood from the following description of the preferred embodiment taken in conjunction with the accompanying drawings in which: 
     FIG. 1. is a diagrammatic longitudinal cross-sectional view of an embodiment of a puffer gas interrupter in the circuit open position; 
     FIG. 2. is a diagrammatic longitudinal cross-sectional view of an embodiment of a puffer gas interrupter in the circuit closed position; 
     FIG. 3. is an enlarged partial view similar to portion of FIG. 1 showing the arc regions and contacts in the open position; and 
     FIG. 4. is an enlarged partial view similar to FIG. 2 showing the arc regions and contacts in the closed position. 
    
    
     DETAILED DESCRIPTION 
     Referring to FIG. 1, an embodiment of a puffer circuit interrupter 10 is shown. The interrupter 10 has a first arc region 12 and preferably a second arc region 14. The interrupter 10 includes an insulating tube 16 closed at each end by a first external terminal such as first metallic end plate 18, and a second external terminal metallic end plate 20. The external terminals provide electrical connections and physical support to the internal workings of the interrupter 10. 
     A first electrical contact 22, preferably a tubular elongated movable venting contact, is located within the insulating tube 16, and electrically connected to the first external terminal 18. A second electrical contact such as a tubular stationary venting contact 24, is located within the insulating tube 16 and electrically connected to the second external terminal 20. A third electrical contact such as a tubular elongated follow contact 26, is located within the insulating tube 16. The third electrical contact is movable relative to the first contact 22 into and out of elctrical engagement therewith and is movable relative to the second contact 24 into and out of electrical engagement therewith. 
     A fluid motor 38 is mounted upon the first contact 22. The fluid motor 38 has a chamber 40 which controllably communicates puffer gas 42, preferably sulfur hexafluoride, through an opening. The puffer gas 42 within the chamber 40 is forced to flow from the chamber 40, through the opening into the first arc region 12 as the first contact 22 disengages from the third contact 26 to extinguish an arc between the first and third contacts, and then serially into the second arc region 14 to extinguish an arc between the second contact 24 and the third contact 26. 
     The first arc region 12 shown in FIG. 1 is essentially identical to the only arc region in heretofore known interrupters and the fluid motor 38 is essentially identical to heretofore known interrupters. Therefore, if the second arc region 14 never opened, the circuit interrupter 10 would have essentially the same current and voltage interrupting capabilities as the heretofore known devices. However, the second arc region 14, because it does open and draw an arc which is extinguished by puffer gas 42 which flows from the fluid motor 38, through the first arc region 12, and the inside of the third contact 26, increases the circuit interrupter 10 current and voltage capabilities beyond those of the heretofore known interrupters without appreciable changes in outside physical dimensions. 
     Referring to FIG. 3, the third electrical contact 26 preferably has annular electrical contacts 27 on each end. Preferably the third electrical contact 26 as slotted flexible contacts on each end to provide a mechanical biasing force against the respective mating contact in the circuit closed position. 
     Referring to FIG. 3 and FIG. 4, the first electrical contact 22 preferably has an insulating nozzle 46 fixed thereon which surrounds one end of the first electrical contact 22 and the third electrical contact 26 and effects a sliding gas-seal therebetween. 
     Preferably, the insulating nozzle 46 directs the flow of puffer gas into the first arc region 12 to extinguish the arc therein. A cooler 47 may be mounted inside the insulating nozzle 46 to cool the puffer gas as it flows across it. The insulating nozzle 46 has annular ridges on its inside surface to prevent arc creepage between the first electrical contact 22 and the third electrical contact 26 in the circuit open position. 
     Referring to FIG. 1 and FIG. 2, the fluid motor 38 preferably has a piston 41, attached to first terminal 18 by an extension of guide 52, located concentrically about the first electrical contact 22 effecting a sliding gas-seal therewith. The piston 41 preferably has at least one one-way valve 44 allowing the fluid motor 38 to fill with puffer gas during circuit closing. Valve 44 blocks puffer gas passage during circuit opening. Preferably the fluid motor 38 has a movable cylinder 39 attached to the first contact 22 forming a chamber 40. The chamber 40 is filled with puffer gas 42 in the circuit-closed position. The chamber 42 decreases in volume with the progression of the circuit-opening motion compressing the puffer gas 42 until the valve-like abutting contact between the first and third contacts is separated allowing the puffer gas to escape the chamber. 
     Referring to FIG. 3 and FIG. 4, the puffer circuit interrupter preferably has an insulating flow guide 48 affixed to the third electrical contact 26, and concentrically surrounding one end of the third electrical contact 26 and the second electrical contact 24 effecting a sliding gas-seal therebetween. 
     Referring to FIG. 1 and FIG. 3, the puffer circuit interrupter preferably has a lost motion mechanism 29 fastened to the second terminal 20 and affixed to the third electrical terminal 26. Preferably the lost motion mechanism 29 has a spring 34, a spider 28 with a plurality of arms 30 fastened to the third electrical contact 26, an insulating tube 32 fastened to the spider 28 and riding on the spring 34, and a spring guide to direct and limit the spring expansion during circuit opening. 
     Referring to FIG. 3 and FIG. 4, preferably the first electrical contact 22 has an annular electrical contact 58 thereon. Preferably the second electrical contact 24 has an annular electrical contact 60 thereon. 
     In operation, a conductive path is provided from the first external terminal 18, and through first electrical contact 22, a third electrical contact 26, and a second electrical contact 24, to the second external terminal 20. 
     During circuit interruption, the improved capabilities of this invention are shown. As shaft 54 is pulled out of first external terminal 18, the stroke myltiplying or &#34;lazy tongs&#34; mechansim retracts the first electrical contact 22 in a direction away from the third electrical contact 26 and at the same time causes fluid motor 38 to begin compressing the puffer gas 42 within decreasing volume chamber 40 because the gas is temporarily blocked within the chamber 40 by the valve-like abutting action of the third contact 26 and the first contact 22 within the gas sealing insulating nozzle 46. As the first electrical contact 22 is retracted, a compressed spring 34 acting through insulating cylinder 32 and spider 28 expands providing a lost motion delay of the separation of the first and third contacts. Instead all of the first contact motion results in a separation of the second electrical contact 24 and the third electrical contact 26 drawing an arc in the second arc region 14. The third contact 26 continues to follow the first contact 22 and puffer gas 42 continues to be compressed within fluid motor 38 until spring 34 reaches the limit of spring guide 36. Once the limit of spring guide 36 is reached, first electrical contact 22 disengages from third electrical contact 26, drawing an arc in arc region 12 within insulating nozzle 46. At the same time the valve-like abutting contact between third contact 26 and first contact 22 is likewise disengaged releasing compressed puffer gas, such as sulfur hexafluoride, from fluid motor 38. The compressed puffer gas flows through insulating nozzle 46 into first arc region 12 puffing out the arc therein, then divides with part of the gas continuing to flow through third electrical contact 26 and insulating flow guide 48 into second arc region 14 puffing out the arc therein and exhausting through second contact 24 into the sealed volume within insulating tube 16. The remainder of the compressed puffer gas flows out of the first arc region 12 through the interior of first electrical contact 22 and is exhausted into the sealed volume within insulating tube 16. Thus, the arcs drawn during contact opening in all arc regions are puffed out, quickly interrupting a current flow of over ten times the steady state current rating and leaving a wider gas-filled-gap thereby providing an increase in interruption voltage rating between the external terminals at the current rating. 
     Thus, by using two or more arc chambers through which the compressed puffer gas is serially released, an increase in circuit interrupting capacity is achieved without an increase in physical size. Where desirable, the cooler element can be used to control the temperature of the puffer gas as it approaches the second of the series of arc chambers. The cooled puffer gas is then able to quench the second arc which means that the overall current interrupting capacity is increased. 
     As will be evident from the foregoing description, certain aspects of the invention are not limited to the particular details of the examples illustrated, and it is therefore contemplated that other modifications or applications will occur to those skilled in the art. It is accordingly intended that the claims shall cover all such modifications and applications as do not depart from the true spirit and script of the invention.