US2355482A - Electric circuit breaker - Google Patents

Description

Aug. s, 1944.

lC. G. SUITS ELECTRIC CIRCUIT BREAKER Filed April 26, 1940 Inventor". Chauncey C5. Suits,

by jww is Attorney.

MAGNET/C HF) 7' 15K/,4L

Patented Aug. 8, 1944 ELECTRIC CIRCUIT BREAKER ChaunceyA G. Suits, Schenectady, N.

Y., assigner to General Electric Company, a corporation of New York Application April 26, 1940, Serial No. 331,797

6 Claims. (Cl. 20o- 152) My invention relates tc electric circuit breakers and more particularly to circuit breakers wherein the circuit is interrupted in a high-pressure gaseous atmosphere and which circuit breakers may employ liquid contacts such as mercury.

Circuit breakers utilizing magnetic means for forcing an arc into an arc chute structure have been used heretofore. In such arrangements, it will be understood by those skilled in the art that the force exerted by the magnetic means is proportional -to the square of the current. Itis characteristic of a breaker of this kind to show a. decreasing number of half cycles of arcing as the current to be interrupted is increased. The magnetic means for forcing the arc into the arc chute necessarily produces a large force at high currents, but a very small force at low currents and, hence, it is generally more difficult to obtain satisfactory interruption of the circuit at low currents. Under these conditions, wide separation of the contacts has been resorted to since, at low currents, the only force available for moving the arc into the arc chute is the convection Aforce due to the buoyancy of the heated air in the arc column.

I have discovered that arcs drawn in high pressure gases show a remarkable increase in convection effects which is fundamentally due to the fact that the buoyancy for a. 'fixed temperature increases directly as the pressure, whereas the opposing factor, namely the viscosity, is substantially independent of pressure. It is clear, therefore, that low-current interruption will be greatly favored by the enhanced convection eiect in highpressure gases and that, at some high pressure, convection alone will serve as the sole means for forcing an arc into an arc chute or other arcextinguishing structure. It would be desirable, therefore, to provide an electric circuit breaker which would interrupt the circuit as rapidly under low-current conditions as under high-current conditions and which would not require the large physical dimensions of circuit breakers of comparable rating used heretofore.

Mercury switches for low voltages and low curn rent values have been used to some extent but have proved unsatisfactory in large-capacity circuit breakers. In most of the mercury switches of the prior art, the circuit was completed by ilowing together two streams of mercury through a narrow bridge of some sort. It is well known that the current flowing through a conductor produces a magnetic field which exerts a, force normal to the surface of such conductor. In the case of the two streams of mercury flowing together through a narrow bridge, this force at the instant of contact is made up of two components, one

view taken along line which tends `to separate the two streams of mercury and the other which tends to pinch o3 the small cross-section of mercury. Under low-current values, these forces are small and, hence. mercury switches of this type are satisfactory. However, at high currents, it becomes diilicult to close the circuit through the narrow mercury stream because ofA this magnetic force and circuit breakers employing a mercury circuit have heretofore been impracticable for large interrupting capacities. ,It wouldfbe desirable to provide an electric circuit breaker employing a mercury circuit which would have a larger interrupting capacity than was heretofore possible since such a circuit breaker would eliminate the re hazard associated with oil circuit breakers and would be much more compact than the so-called "air circuit breakers.

Accordingly, it is anobject of my invention to provide a compact circuit breaker which will overcome the disadvantages noted above in connection with circuit breakers of the prior art.

It is another object of my invention to provide a new and improved circuit breaker employing liquid contacts which have an interrupting capacity considerably higher than was heretofore possible.

Still another object of my invention is to provide a circuit breaker which will interrupt the circuit in a very short interval of time, which interval of time will not vary substantially with variations in the current to be interrupted.

It is a further objectof my invention to provide a circuit breaker including an arc chute wherein the circuit is interrupted in a gas under very high pressures so that the convection effect will force the arc into the arc chute to extinguish the same rapidly.

Further objects and advantages of my invention will become apparent as the following description proceeds and the features of novelty which characterize my invention will be pointed out with particularity in the claims annexed to and forming a part of this specication.

For a better understanding of my invention, reference may be had to the accompanying drawing in which Fig. l is a schematic diagram of a circuit breaker embodying my invention; Fig. la is a ,schematic illustration to aid in explaining the theory of my invention; Fig. 2 is a crosssectional view of my circuit breaker at the instant the contacts are separated; Fig. 3 is a crosssectional view of the circuit breaker in the closedcircuit position; Fig. 4 is a sectional view taken along line 4--4 of Fig. 3; Fig. 5 is a sectional 5-5 of Fig. 3; and Fig. 6

is a perspective view of a portion of my circuit breaker.

Referring now to Fig. l, I have illustrated my invention as applied to a circuit breaker Il employing liquid contacts, such as mercury, which circuit breaker is adapted to interrupt the current flowing in electric circuit Il and comprises a pressure-conning chamber I2. In order toA interrupt the circuit, pressure-comming chamber l2 is tilted so as to cause separation of the liquid contacts therein. Any suitable means for tilting chamber I2 may be provided and, in Fig. l, I have illustrated pressure-comming casing or chamber I2 as mounted in a cradle Il which is pivotally mounted at I l and arranged to be op' erated by any suitable mechanism, such as I5. The entire unit may be mounted on a suitable insulating base I6, if desired.

Referring now to Figs. 2 and 3, pressure-oonning chamber I2 is illustrated as aV metallic cylinder so constructed as to withstand relatively high pressures therein. One end of chamber I2 is closed by a metallic closure member I1 preferably welded thereto and associated with a suitable threaded electrode Il through which connections to the external circuit may readily be made. A suitable passage II is provided in closure member I1 for purposes which will be hereinafter described and this passage is sealed oi! at 2II as by welding when the circuit breaker is completely constructed. The other end of pressure-conilnlng casing I2 is provided with an electrode 2| extending therein and insulated therefrom by any suitable glass-to-metal seal 22 of rugged construction to withstand the high pressures within pressure-connning chamber I2. Preferably this seal 22 is of the type disclosed now Patent No. 2,299,750 issued Oct. 2'?, 1942, and broadly claimed in copending joint application Serial No. 305,666, filed November 22, 1939, on behalf of Albert W. Hull and Roy W. Moore, and assigned to the same assignee as the present invention.

As mentioned above, when two mercury surfaces flow together through a narrow bridge,

point contact is made by virtue of the convex meniscus. In any conductor, the. force due to the magnetic field of the current upon itself is normal to the surface of the conductor. As illustrated in Fig. la, this force may be resolved into two components, FA which tends to force the mercury away from the junction box and Fa which tends to pinch off the small section of mercury. 'I'he resultant of the forces FA and Fs is represented by F in Fig. 1a and is normal to the surface of the mercury stream. From the above discussion and particularly with reference to Fig. la, is will be observed that the forces are such as to prevent\closure of/the circuit under high currents. The forces which prevent the liquid contacts from closing the circuit will be rendered much less effective if as large a radius of curvature as possible is provided for the two contacting surfaces; that is, by having two relatively wide streams of mercury flow together so as to meet substantially on a straight line. With a narrow stream of mercury. this is impossible due to the effect of the meniscus. Therefore. I provide a cup-shaped member 21 of insulating material resiliently supported from closure member I1 by spring means 2l. 'I'his cup 22 preferably of ceramic material is provided with a shallow end remote from the supporting means 24 which is closed by a barrier or dam 2l across the edge assumes of which the liquid contacts meet and separate on a straight line of substantial width during the circuit-closing and opening operations. Pressure-coniining casing I2 is filled with mercury to the level indicated at 26 and it may be observed from Fig. 2 that barrier 25 has just interrupted the mercury circuit in so far as the mercury within and without ceramic cup 22 is concerned.

Electrode 2l is suitably connected to the mercury in ceramic cup 22 by a conductor 21, shown in detail in Fig. 6, which ends in a flattened portion 28 bearing against the wall of ceramic cup 23 adjacent spring 2l so that, by virtue of the force of spring 24, ceramic cup 22 will be held stationary and in proper position within pressure conining casing I2.

Since the resistance of mercury is relatively high compared with that of copper, for example, considerable heating would occur under high currents if the current had to tlow through a long mercury path for any length of time. However, I eliminate this diiliculty by closing an auxiliary circuit in parallel with the liquid contacts after the initial closing of the liquid contacts at the barrier 25 of ceramic cup 2l. Accordingly, conductor 21 is arranged to extend below electrode 2| and is constructed with a portion thereof in the form of a shoe 29 of relatively large surface area. Further tilting toward the horizontal of pressure-confining chamber I2 in Fig. 2 will cause the electric circuit to be closed between shoe 23 and the walls of pressure-coni'ining chamber I2, as shown in Fig. 3. By virtue of the arrangement of shoe 29 relative to the walls of chamber I2, the cross-section of the mercury conductor at this point is very large while the length of conqucting path is very shorI so that the internal resistance of the circuit breaker becomes negligible during the closedcircuit condition. Furthermore, by this arrangement, the interrupting ability of the circuit breaker is enhanced since the resistance of the long mercury path is inserted in series with the circuit prior to interruption thereof.

In order to aid in extinguishing the arc drawn upon circuit interruption, a suitable arc chute I0 is provided comprising a plurality of relatively thin baille plates 2| having the edges thereof extending close to and perpendicular with the barrier 25 of ceramic cup 22. This arc chute 20 is illustrated as being provided with ends I2 and 22 so as to prevent the arc gases from escaping adjacent the portion 2l of conductor 21 or adjacent the portion of conductor 21 associated with electrode 2l, thereby preventing the formation of any ionized path between these conducting members. Also, in order to prevent the arc gases from passing through arc chute 30 directly against conductor 21 and the walls of chamber I2, I provide a top cover member Il for arc chute 2l which is arranged so that the arc gases may be vented through openings 2l, shown in Fig. 5, at the upper corners of the arc chute. Furthermore. pressure-comming chamber I2 is provided with an insulating liner 2l so as to prevent any arcing to the walls of casing I2. 'I'his insulating liner Il may be provided only for the upper walls of chamber I2 if desired, as illustrated in Fig. 3 and supported by suitable means such as 21.

be supported in any suitable manner from conductor 21 and, as will be understood by those skilled in the art, may be formed of any suitable insulating material. 'Ihe interrupting Arc rchute Il mayclockwise direction`,

ability of my circuit breaker is further increased by providing suitable cooling or deionizing -means 38 comprising alternate layers of flat and corrugated screen, for example, to aid the baille plates 3| of arc chute 3l in cooling the arc gases. Preferably, the baille plates 3i and the deionizing means I8 are ilnely subdivided so as to provide the maximum cooling of the arc and arc gases. However, these subdivisions must not be so small that they are destroyed as by melting. l

In order to overcome the magnetic field due to the circuit configuration and thus permit the arc to be drawn across barrier 25 of ceramic cup 23 into the arc chute III, I provide magnetic means in the form of a horseshoe-shaped electromagnet which comprises an iron horseshoe l0, mounted just outside the walls of ceramic cup 2l Aadjacent barrier 26, around which a plurality of turns 40 of conductor 21 are wound. Suitable insulating means 4I are provided between iron horseshoe 39 and the turns 4l.

In order that my circuit breaker will interrupt an electric circuit in the 4same interval of time at low currents when the force due to the electromagnet comprising horseshoe 39 is very low as compared to high-current conditions when this force is verylarge, I nll pressureconfining casing I2 witha suitable gas, preferably hydrogen, under relatively high pressures of the order of several atmospheres and prefervrably ten or more. This gas vmay be supplied to chamber I2 through passage I9, which is thereafter sealed oil? at as by welding. The highpressure gas will greatly 4increase the convec tion leffect so as to force the arc into the arc chute without depending upon the magnetic means for accomplishing this result. It will be understood by those skilled in the art that an arc chute used in connection with a circuit breaker operating in an atmosphere of hydrogen under high pressure may be applied to other circuit breakers and is not limited to circuit breakers having liquid contacts, such'as mercury.

The operation of my new and improved ciri cuit breaker will be considered first with reference to Fig. 3 where the electrical circuit is closed and the current flows from the bottom walls of chamber I2 through the short mercury path to the shoe 29 of conductor 21 which is associated with electrode 2|, cylinder I2 being connected to the other electrode I8. The circuit through circuit breaker I 0 may be interrupted by tilting chamber I2 in a .counterwhereupon the circuit through shoe 29 of conductor 21 is ilrst interrupted and all the current must be carried by the long mercury path from the portion 28 o! conductor 21 to electrode I8. Further tilting` of casing I2 to the position shown in Fig.\2 causes a separation between the mercury within ceramic cup 23 and the rest of the mercury in chamber I2 by virtue of barrier 25 across `which an arc is drawn. This arc is forced into arc chute 30 by theconvection effect of the high-pressure gas in chamber` I2 and, under high-current conditions, also bythe force due to the magnetic means comprising horseshoe 3,8. The baiiles 3| and the ionizing means, aid in rapidly quenching the arc, whereupon the circuit is interrupted.

In closing the circuit, the mercury within cup 23 and that in chamber I2 flow together over barrier 25 lso as to approach each other inl a modifications as fall within the true spirit and y,

scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States, is:

l. An electric circuit breaker for interrupting relatively high currents, `a. closed chamber, means including liquid contacts within said chamber arranged to draw an arc upon separation thereof to interrupt an associated electric circuit, a cup-shaped member of insulating material supported within said chamber having a relatively shallow portion at one end thereof, said shallow end being closed by a barrierv of substantial'width across which said'liquid contacts are separated when interrupting said circuit, a. conductor arranged to extend into said cup-shaped membery to engage one of said liquid contacts, and spring means for biasing said cup-shaped member against said conductor. 2. In an electric circuit breaker, a chamber, means including liquid contacts within said chamber arranged to draw an arc 'upon separa,-y tion thereof to interrupt an. associated electric circuit, a rrectangular ceramic cup supported within said chamber having one shallow end closed by a barrier of substantial width across which said liquid contacts are separated when interrupting said electric circuit, a conductor arranged to extend into said cup-shaped member to engage one of said liquid contacts, means for biasing said cup-shaped member against said conductor. and means for closing a circuit in parallel with the circuit through the liquid contacts subsequent to the completion of the latter to increase the current-carrying ability of said circuit breaker.

3. In an electric circuit breaker, a chamber. means including liquid contacts within said chamber arranged to draw an arc upon separation thereof to interrupt an associated electric cuit may be obtained, and means for preventing said arc gases from coming into contact with conducting portions of said circuit breaker before they are sufficiently cooled and deionized by said arc chute.

4. An electric circuit breaker comprising a pressure-conning chamber containing hydrogen under a pressure of ten or more atmospheres,

means including liquid contacts within said chamber arranged to draw an arc upon separation thereof to interrupt an vassociated electric circuit, a rectangular cup-shaped member of insulating .material supported within said chamber, one edge of which comprises a barrier of substantial width across which said liquid contacts are separated when interrupting said electric circuit, an arc chute comprising a plurality of baiiie plates adjacent said barrier, and magnetic means for forcing said arc into said arc chute under highcurrent conditions so that high-speed interruption of said circuit may be obtained, said arc being forced into said arc chute under low-current conditions solely by the convection effect of said hydrogen under pressure.

5. An electric circuit interrupter oi the type capable of interrupting low currents as well as high currents comprising a pressure confining chamber, relatively movable contacts in said chamber arranged to draw an arc upon separation thereof, an arc chute comprising a plurality oi baille plates arranged in said chamber above said contacts, magnetic means ior forcing said arc into said are chute under high current conditions, and means for forcing said arc into said arc chute under low current conditions quickly to extinguish the same comprising hydrogen under ten atmospheres or more of pressure contained in said chamber to produce a greatly enhanced convection ei'lect forcing said arc into said arc chute.

6. An electric circuit interruptelof the type capable of interrupting low currents as well as high currents, comprising a pressure confining chamber, means including liquid contacts within said chamber arranged to draw an arc upon separation thereof, an arc chute comprising a plurality oi baiiie plates arranged in said chamber above said contacts, means for forcing said arc into said arc chute to extinguish the same under high current conditions, and means for forcing said arc into said arc chule under low current conditions quickly to extinguish the same comprising hydrogen under a pressure of ten atmospheres or more contained in said chamber so as greatly to enhance the convection eiIect forcing zo said arc into said arc chute.

CHAUNCEY G. SUITS.

Images