US2061945A

US2061945A - Circuit interrupter

Info

Publication number: US2061945A
Application number: US707928A
Authority: US
Inventors: Koppelmann Floris; Kaufmann Werner; Kesselring Fritz
Original assignee: Westinghouse Electric and Manufacturing Co
Current assignee: CBS Corp
Priority date: 1933-01-23
Filing date: 1934-01-23
Publication date: 1936-11-24
Anticipated expiration: 1953-11-24
Also published as: FR769291A; FR44687E; USRE20962E

Description

Nov, 24, 1936.

F. KOPPELMANN El AL CIRCUIT INTERRUPTER Filed Jan. 25', 1934 2 Sheets-Sheet l INVENTORS Flor/3 Aoppe/mann, t h/yrnqr A ATTORNEY W H 'NESSES: 6d 1 Nov. 24, 1936.

F. KOPPELMANN El AL.

C IRCUIT INTERRUPTER Filed Jan. 23, 1934 2 Sheets-Sheet 2 v WITNESSES:

Patented Nov. 24, 1936 2,061,945 cmomrm'rnanuma Floris Koppclmann and Werner Kauimann, Berlin-Sicmensstadt, and Fritz Kesselring, Berlin-Hermsdori, Germany, assignors to Westinghouse Electric & Manufacturing Company,

East Pittsburgh, Pa., a corporation of Pennsylvania Application January 23, 1934, Serial No. 707,928 In Germany January 23, 1933 tissue) 4 Claims. (Cl- 200-150) have been known in the art for some time. In

most 01' these structures, however, the jet of liquid or gas which eiiects the extinguishment oi the arc is not controlled to the best possible advantage, and even if the jet is produced by such refined structures as the well known blowout nozzle of the heavy-duty compressed air switch, an appreciable amount of the arc extinguishing fluid is not utilized at all eflectively.

In some of the known fluid. type are extinguishing devices, the arc is drawn within. a narrow, oil-filled channel or chamber, which is provided with a vent opening at one end thereof, through which opening one or the cooperating contacts is adapted to move. Upon the separa- 5 tion of the contacts, an arc is established within the arc chamber, and a considerable quantity of the fluid contained therein is volatized. This volatile fluid, in venting, flows outwardly through the open end or the arc passage with an expulsive or blast action and thereby extinguishes the arc. To improve the operation of these devices, it

has been proposed to provide further fluid moving means for assuring an adequate blast of arc extinguishing fluid through the are at all times,

5 the pressure for forcing this additional quantity of liquid through the are being preferably pro duced by the arc itself. More specifically, a portion of the arc, which portion is drawn within the main arc extinguishing chamber or within 40 a separate pressure chamber connecting with the main arc chamber, is utilized. This separate pressure chamber, if this means is used, communicates with the outer atmosphere only through the arc passage itself, and while during 45 the normal operation of such devices, a greater amount of fluid is caused to flow through the arc passage, a'large proportion of this fluid is in the heated gaseous state, with the result that the arc extinguishing operation takes place much less efliciently than would be the case were liquid alone forced through thearc. Furthermore, the considerable quantity of liquid which is disposed intermediate the pressure producing arc and the arc extinguishing passage proper prevents the rapid expansion of the gas formed therein and delays the arc extinguishing operation.

Substantially the same conditions are present in all known switches and fuses, wherein a portion of the arc, which is drawn through the arc passage, exists in a separate closed chamber fllied with liquid, the separate chamber communicating with the atmosphere only through the arc passage.

According to the present invention, the arc is drawn within a narrow arc passage, which is filled with a flowing stream of arc extinguishing liquid, under pressure, for effecting the extinction of the arc during the operation of the device. The novel feature of the present invention hes in the fact that the Supply of arc extinguishing liquid is eflected during the circuit opening pressure of the arc extinguishing liquid is independent of the arc magnitude, the liquid surrounding the arc is capable of counteracting the internal pressure of the arc stream at all times.

The expansion chambers, into which the ends of the arc passage open, permit the free expansion oi the gases expelled from the arc passage, and are so proportioned that they do not cause any substantial increase in the pressure, which is required to force the arc extinguishing fluid through that passage' The expansion chambers must, consequently, be of considerable size and normally free of liquid. Preferably, the means which defines the walls of the arc passage is arranged in a chamber free of liquid, except during the circuit opening operation, the pressure of the fluid moving means being thereby minimized.

The magnitude of the pressure force which moves the arc extinguishing fluid through the arc passage is such that the liquid surrounding the arc is caused to follow the decreasing crosssection of the arc alorg the entire length of the arc passage, without delay, when the alternatingcurrent wave approaches its zero value. The pressure must also, of course, be sufliciently large to assure that the arc extinguishing passage shall be filled with liquid within a very short interval of time following the establishment of an arc therein. We have found that pressures of 2 to 20 atmospheres are necessary for effecting a most eflicient operation of our invention, the magnitude of the pressures depending upon the design of the arc passage, the size of the supply conduit for the arc extinguishing liquid, and the current magnitude of the arc.

Low pressures are satisfactory under the more favorable expansion conditions, since then the pressure supplied to the arc extinguishing fluid need only be sufficiently large to overcome the normal pressure existing within the arc stream. Similarly, low pressures are satisfactory when small quantities of liquid have to be moved into and accelerated along the arc passage. We have found that the best arrangement comprises an arc extinguishing passage of small cross-sectional area in combination with a low loss conduit and a particular liquid container especially designed for cooperating therewith, the liquid being forced into the arc passage by compressed air or similar means.

The effectiveness of the arc extinguishing action of our invention depends upon the length of the portion of are which comes into intimate contact with the surrounding stream of liquid. It is, therefore, essential for the successful accomplishment of our invention that the arc passage shall be filled with liquid under pressure during the entire circuit opening operation, and

that the passage shall have a predetermined minimum length, depending upon the operating voltage and the possible magnitude of the current to be interrupted, the length being calculable on the basis of experimentally obtained values of arc extinguishing capacity per unit length of the device. The channel must not be too short, since the arc extinguishing liquid vents freely at the open ends of the arc passage, and suflicient pressure for effecting the contraction of the fluidarc stream is available only adjacent the central portion. Likewise, the channel must not be too long, since the thickness of the gas column flowing in an axial direction through the, arc passage during the circuit opening operation increases from the center towards the end of the channel, and after a predetermined length has been excited, the temperature of the flowing gas stream so nearly approaches the temperature of the are that no substantial cooling action is eflected.

The arc extinguishing device of our invention may be operated with practically any insulating liquid, and may be satisfactorily operated with semi-conducting liquids, such as water, since the arc extinguishing effect is not, primarily, a result of the insulating properties, but rather of the heat absorbing capacity of the arc extinguishing liquid.

Arc extinguishing devices, according to the present invention, are capable of interrupting high-voltage circuits with much smaller arc chambers and with a much less gas evolution than has heretofore been thought possible. These advantages arise from the fact that the extinguishing device possesses a very high are interruption capacity per unit length, and is capable of effecting the opening of the controlled circuit within the first cycle of operation. Another advantage of our invention resides in the fact that in comparison to the well known circuit interrupting devices very small quantities ofarc extinguishing medium need be supplied during its operation. In addition, the work expended in effecting the delivery of the arc extinguishing medium is likewise small, which fact may be attributed to the high efllciency with which the heat capacity of the liquid is utilized. Furthermore, it is not necessary to utilize insulating liquids which possess the undesirable property of inflammability with the devices of our invention. And lastly, our invention makes possible a structure which is very simple in construction, which may be operated with comparatively low-pressure supplies of gas, and which, being open to the atmosphere during its operation, is substantially explosion-proof.

The improved operation of our invention results from the fact that devices embodying our invention produce a particularly high-temperature gradient between the arc and the external surrounding fluid, and that the minimum arc diameter for any particular value of arc current is assured. This small arc diameter and hightemperature gradient is brought about by means which causes the heated vapor and gas, produced in the immediate neighborhood of the arc stream, to be constantly carried away and replaced with fresh cool liquid. Specifically, this means comprises, as mentioned above, a surrounding sleeve or jacket of flowing liquid, under pressure, which intimately contacts and surrounds the are for a given length, and which flows along the arc stream throughout its entire axial length, the flowing stream of arc extinguishing fluid venting through openings disposed at the ends of the arc passage. This surrounding jacket of liquid consists of an outer sleeve of liquid, an inner sleeve formed by the are gases, and a thin vapor jacket intermediate the outer and inner sleeves. By continuously replacing the highly heated gases in the immediate neighborhood of the arc stream by a cooling means of high heat absorbing capacity per unit volume, the physical dimensions of the arc stream will be minimized in cross-section, and when the current passes the zero value, the arc will become incapable of reigniting itself, and will thereby be extinguished. Since all of the gases and the vapor produced by the heat of the arc are continuously removed from the arc passage by the flowing stream of liquid, excessive pressures within that passage are prevented and satisfactory operation of the device may be accomplished with fluid pressures of a few atmospheres.

For high voltage circuits of large current capacity, a plurality of arc extinguishing devices, according to our invention, may be connected in series, each of the devices being provided with an arc passage of limited length, this arrangement effecting the extinction of high voltage arcs with a maximum efficiency. As another means of improving the operation of the devices, the arc passagemay be provided with radial vent openings intermediate the ends thereof, and the liquid may be supplied to the channel at various points between the vent openings.

The arc extinguishing passage may have a rectangular or elliptical cross-section. In the case of a circular cross-section, it is preferable, for most applications, to make the diameter less than 15 millimeters.

In order that the arc extinguishing liquid shall reach the immediate neighborhood of the arc for the maximum possible length during the passage of the arccurrent through zero value, we have provided means in the neighborhood of the are which will act as buffers or energy accumulators, the frequency of these energy accumulating means being preferably approximately two or three times the natural frequency of the arc.

Through this means, the flowing stream of liquid is caused to more closely, surround the arc and to follow the oscillations of the arc with a minimum time lag, the energy accumulating means having a higher natural frequency of vibration than the arc. An energy accumulating effect may be accomplished by suitable design of the arc passage itself or through the provision of separate means, as will be described in detail later.

Through the provision of an energy storing means, the operation of the extinguishing device may be effected with a much lower pressure than is possible without such an arrangement. In effect, the energy accumulator absorbs the shocks imparted to the liquid flowing through the arc stream due to the variation in cross-sectional area of the arc with the normal alternations of the current wave.

One suitable arrangement resides in the provision of air dashpots or air containing pressure vessels connected to the supply conduit for the pressure liquid, intermediate the arc passage and the main body of arc extinguishing fluid. This means prevents the oscillations in the liquid flowing through the arc passage from being transferred to the main body of the arc extinguishing liquid, and limits them to a relatively small quantity of liquid in the immediate neighborhood of the arc. As an alternative arrangement, the body enclosing the extinguishing chamber may be made of elastic material. Likewise, it is possible to provide suitable gas-filled elastic sleeves or bodies disposed within the arc passage in the neighborhood of the extinguishing chamber. To prevent the arc extinguishing liquid from flowing continuously through the arc extinguishing de vice, the supply means for the liquid is preferably placed under pressure only during the operation of the-switch. The pressure may be produced by the gear or other means which actuates the moving contact or suitable valve means may be provided.

It is also possible to supply pressure which varies periodically with alternating-current wave, this pressure being produced approximately 1-1/ 1000 of a second before the alternating-current wave reaches the zero value.

The minimum pressure under which the liquid mustbe placed in the immediate neighborhood of the arc is a function of the dimensions of the arc passage. As pointed out above, too high pressures are undesirable, since they are unnecessary and even dangerous, because the forcing of liquid into the arc extinguishing chamber in such manner that the arc may be extinguished during a Fig. 11 is a curve showing the variation of pressure within a device utilizing an energy accumulating device and in a device wherein such a device is not utilized;

Fig. 12 is a diagrammatic view showing a circuit interrupter embodying the features of our invention;

Fig. 13 is a sectional view on the line XIII- XIII of Fig. 5;

Fig. 14 is a sectional view on the line XIV- XIV of Fig. 6; and

Fig. 15 is a sectional view on the line XV-XV of Fi 8.

A circuit interrupter embodying the features of our invention is illustrated diagrammatically in Fig. 12. As shown in that figure, the insulating means I, which defines the walls of the arc passage 2, is disposed within an outer casing 3, which is of suflicient size that the outfiowing gases may freely cxpand therein during the operation of the device. To further assure that no objectionable back pressures shall be built up within the casing, a plurality of openings 5, leading to the atmosphereare provided. A stationary contact -I3 is supported at one end of the casing and is adapted to cooperate with a movable contact M which is supported by suitable guide and actuating means 6. The main body of arc extinguishing liquid 1 is contained within a suitable reservoir 8 and the pressure for moving this liquid is supplied thereto from a gas containing pressure cylinder 9. The flow of the arc extinguishing fluid through the passage is controlled by an electrically operated valve 40 which is operable in response to an overload relay 4| which controls the operation of the movable contact memher or to other means, as may be desired. A pump means 42 may be provided for returning the arc extinguishing fluid to the main reservoir following each operation of the interrupter.

During the circuit opening operation of this device, the coil 43 forming a part of the actuating means 6 for the movable contact is energized and causes the movable contact rod M to be moved through the arc passage 2 formed within the arc extinguishing chamber. At the same time the arc extinguishing fluid begins to flow through the arc passage to eifect the extinguishment of the arc when drawn therein. The particular form of the circuit interrupter is not an important part of this invention, which is more particularly concerned with improving the operation of the arc extinguishing device utilized therewith, and any suitable structure may be employed.

In Figs. 1 to 3, the circuit interrupter is shown as including tubular means L for defining the walls of an arc passage wherein the arc is drawn in an axial direction, both ends of the passage opening into a suitable expansion space. The conduit Z is provided for supplying the are extinguishing liquid to the interior of the passage defining means L at the central portion thereof. Three successive steps in the arc extinguishing operation are shown. The difference of time between the step shown in Figs. 1 and 2 and between that shown in Figs- 2 and 3 amounting to about .0005 second. The difference in time between Figs. 1 and 3 totals, therefore, .001 second. Fig. 3 represents the are at the time when the alternating current passes through a zero value and the other figures show the arc shortly before the current reachesthe zero value. The current magnitude of the arc might be 3000 amperes in Fig. 1, 1500 amperes in Fig. 2, and 0 in Fig. 3, assuming an alternating current of 50 cycles.

Shortly before the arc is drawn through the arc passage, which is defined by the member L,

a quantity of arc extinguishing liquid is forced into that passage through the supply conduit Z. The are is, therefore, surrounded by a cylindrical jacket M of arc extinguishing liquid which is under a suitable pressure immediately upon its formation. The are evaporates the layer of liquid immediately adjacent thereto, and as a result forms a vapor jacket around itself, which par-' tially insulates the liquid from the arc. The entire fluid column, however, together with the vapor jacket is caused to flow rapidly in the axial direction of the arc passage because of the great difference in pressure prevailing between the central portion of the arc passage and the open ends thereof.. The flowing liquid, thus replaces the escaping .gases so that with the decreasing gas generation accompanying the normal decrease in current magnitude of the arc, the liquid channel M surrounding the arc increases in cross-section. The are extinguishing liquid is under such a pressure and is admitted to the arc passage under such a large conduit that the complete filling of the arc extinguishing passage is assured at all times.

To assure absolute freedom of movement of the arc extinguishing fluid through the arc passage, it is essential that the open ends shall be free of any restriction and an adequate supply of arc extinguishing fluid under a suitable pressure shall be available throughout the entire circuit opening operation.

In Fig. 2, the arc passage is substantially filled with liquid, and in Fig. 3, the arc has shrunk to a small liquid channel. At this time, the portion of the arc stream in the arc passage has a very high temperature gradient, and since a large quantity of liquid with a very high heat absorbing capacity is being moved through the arc passage, the temperature of that remaining portion of the arc stream drops very considerablywithin the short interval of time (which amounts to about .0001 to .00001 second), when the current passes. through the zero value and before the restored voltage reaches a sufficient magnitude to cause the restriking of the arc. The arc,

therefore, does not reignite itself in the arc passage, provided, of course, that the fluid column therein is sufllciently insulating to withstand the circuit voltage.

The conditions prevailing in the arc extinguishing chamber during one alternation of the supply current are illustrated in Fig. 4. The curve T denotes a half. wave of the alternating current; the curve V the velocity of flow of arc extinguishing liquid through the arc passage; the

curve K and the force which must be available for accelerating the fluid supply in order that the arc passage may be entirely filled with liquid during the arc extinguishing operation. The pressure force to be applied to the liquid is, of course,

a function of this accelerating force.

During tests of our invention, an arc of 8,000 amperes at an operating voltage of 15,000 volts was extinguished within an arc passage having a length ofv 49 millimeters at the flrst'zero value in current wave, the arc passage being vented to the atmosphere at either end and water, at a pressure of 10 atmospheres, being utilized as the arc extinguishing fluid. The insulation of the arc passage was found to be capable ,of withstanding 3,000 volts per centimeter of length immediately following the first zero point in the wave, which value is much higher than can beobtained in the devices heretofore known in the art.

Figs. 5 to 7 show variousmodifled forms of an arc passage during the operation of the device,

is provided for cooperating therewith. The are passage II is filled with are extinguishing fluid which flows through the channel l2, immediately upon the initiation of a circuit opening movement, and the extinction proceeds exactly as described above. Fig. 5 illustrates the manner in which the gas evolved by the heat of the arc causes the arc stream to increase from the center toward the outer ends thereof.

The arc chamber shown in Figs. 6 and 14 is substantially similar to that shown in Fig. 5, except that an annular passage l1 surrounds the arc passage I6, which is formed within the wall defining insulating body l5. Through this arrangement, a more even in-flow of the arc extinguishing fluid is accomplished.

A further modification is illustrated in Fig. '7 wherein a cylindrical arc passage I9 is formed within an insulating body It and is provided with a radial relief opening 20 and a pair of supply channels 2| and 22. In this embodiment, the usual decreased efliciency of a relatively long are extinguishing passage is obviated, since the passage is divided by the relief opening into two shorter passages, each of which is in effect opened at both ends. By this means, two restricted portions of the arc stream are made possible.

In Figs. 8 to 10, we have shown certain devices which are provided with energy storing means for assuring a continuous flow of arc extinguishing liquid into the arc passage during the circuit opening operation. As pointed out above, this arrangement makes possible the use of lesser pressures in the supply means for the are extinguishing fluid and increases the reliability of operation of the device. The structure shown in Figs. 8 and 14 comprises an air vessel 24, which is connected to the arc passage by a suitable conduit. This vessel acts similarly to any of the other well known energy storing arrangements.

Fig. 11 shows the effect of the energy storing means time plotted on the horizontal axis. The curve T1 represents the arc current, the curve Vi the velocity of the flow of the liquid in the arc passage without the energy storing buffer device. and the curve V: the velocity of flow of the liquid with the buifer device. The accelerating force to be applied .to the liquid is proportional to the tangent of the angle B. As will be apparent, the pressure producing force may be reduced by the provision of a properly designed energy storing bufler means.

Fig. 9 illustrates another embodiment. The variations of pressure in the neighborhood of the arc passage are absorbed by gas-filled elastic bodies 26 and 21' arranged in the supplycondult for the arc extinguishing medium, and the pressure in the liquid is produced by forcing downwardly a piston 29 which entraps a quantity of gas in the space 30 between the surface of the liquid and the piston. Instead of compressing the gas by forcing downwardly by moving a piston, the chamber may be connected with a pressure source, such as illustrated in Fig. 12, the valve 0 controlling the force of pressure being opened upon the interruption of the switch. The gas-filled

elastic bodies

26 and 21 are compressed when the current magnitude of the arc is high and expand as the current magnitude decreases to the zero value.

The are extinguishing device shown in Fig. 10 is provided with a particularly large cross-sectional area supply means. The are passage is formed within an insulating body 31- which is connected with the liquid chamber 35 through

various supply openings

32, ,33, and 34, which are so arranged that, at one side only the

walls

85, 36, 31, and 38 remain, and the channel is divided into a plurality of single sections. An elastic cushion means 36, which serves as the energy storing buffer, and which may take the form of a rubber balloon or similardevice, is disposed within the pressure chamber 35. The liquid enters the pressure chamber 35 and through it and the arc passage from an external .supply source, the direction of flow being indicated by the arrow 31. The large cross-sectional area of the supply source aids in minimizing the pressure which must be supplied to the liquid by reducing the fluid friction.

The arc extinguishing devices as shown in Figs. through may be arranged in a liquid container as in such manner that the surface of the liquid contained therein lies somewhat above the upper edge of the arc passage. The are extinguishing passage is then completely filled with liquid at all times and during the circuit opening operation it is necessary merely to provide a pressure for moving the liquid through the passage. It is also possible to accomplish our invention wherein the arc passage is opened at only one end.

We claim as our invention:'

1. In a circuit interrupter for use with alternating current circuits, means for defining the walls of a tubular arc passage having a length at least several times its greatest cross sectional dimension, means for establishing the arc incldent to the opening of said interrupter longitudinally within said are passage, a body of arc extinguishing liquid, and means operable during each circuit opening operation of said interrupter to move a quantity of said liquid which has not been subjected to the arc into said are passage, said liquid being introduced into said passage under suflicient pressure, with respect to the dimensions of said passage, to cause at least a portion of said arc to be surrounded by a flowing stream of fresh, unionized, arc extinguishing liquid which intimately contacts said are at all times at least several times its greatest cross sectional dimension, means for establishing the arc incl- .dent to the opening of said interrupter longitudinally of said passage, a body of arc extinguishing liquid, and means, including a conduit which connects with said passage intermediate its ends, operable during and only during each circuit opening operation of said interrupter to move a quantity of liquid which has not been subjected to the arc into said passage, said are passage being open at either end and except for said conduit means being otherwise completely enclosed, said quantity of liquid being moved into said are passage under sufficient pressure to cause said arc to be surrounded by a flowing stream of fresh, unionized, arc extinguishing liquid which is in intimate contact therewith throughout each circuit opening operation, the dimensions of said passage and the pressure at which said liquid is introduced therein being so correlated that said flowing stream of liquid follows the normal variations in the dimensions of said are resulting from the normal fluctuations in the magnitude of the arc current' 3. In a circuit interrupter for use with alternating current circuits; solid means for defining the walls of a substantially cylindrical arc passage having a length at least several times its crosssectional diameter; means for establishing the arc incident to the Opening of said interrupter within said are passage, the cross sectional area of said arc passage being not more than slightly greater than the maximum cross sectional area of the largest current magnitude are which may be drawn therein during the operation of said interrupter; a body of arc extinguishing liquid; means, including a conduit which connects with said passage intermediate its ends, operable during each circuit opening operation of said interrupter to cause a quantity of said liquid to be moved into said are passage without substantial heating orionization thereof; said quantity of liquid being under suflicient pressure to cause at least a portion of said are to be surrounded by. a flowing stream of fresh, unionized, arc extinguishing liquid; saidarc passage being open at either end and except for said conduit means being otherwise completely enclosed; and energy storage means sufficiently low inherent inertia to prevent the normal fluctuations in the physical dimensions of the arc, due to normal variations in the current wave, from causing excessive fluctuations in the pressure within said are passage, in order that said flowing stream shall intimately contact said are at all times during the operation of said interrupter.

-4. In a circuit interrupter, means for defining the walls of a tubular arc passage having a length at least several times its greatest cross-sectional dimensions, means for establishing the arc incident to the opening of said interrupter within said are passage, a body of arc extinguishing liquid, means, including a conduit which connects with said are passage intermediate its ends, operable during each circuit opening operation of said interrupter to move a quantity of said liquid into and through said are passage to extinguish said are, said quantity of liquid being moved into ing said chamber into pressure responsive relationship with said are passage, for preventing the normal fluctuations in the magnitude of--the arc current from causing sufficient fluctuation in the pressure in said passage to permit said intimate contact between said are and said liquid to be broken, said are passage being open at at least one of the ends thereof and except for said conduit means and said means for connecting said gas containing pressure chamber into pressure responsive relationship therewith being otherwise not substantially less than twice the period of the substantially completely enclosed, the ph,,sical dialternating current circuit with which the intermensions of said are passage, the pressure at rupter is used.

which said liquid is introduced thereinto, and the FLORIS KOPPEIMANN. characteristics of said energy storage means being WERNER KAUFMANN. so correlated that the natural frequency of oscil- FRITZ KESSELRING.

lation of said energy storage means is at all times