US2250566A - Circuit interrupter - Google Patents

Description

July 29, 1941. B. P. BAKER ETAL 2,250,566

CIRCUIT INTERR'UPTER Filed Jan. 24, 1940 2 Sheets-Sheet 1 WITNESSES: INVENTORS Benjamin 1. Baker &

July 29, 1941. B. P. BAKER ETAL CIRCUIT INTERRUPTER Filed Jan. 24, 1940 2 Sheets-Sheet 2 0 mad ke R V06 m MBA T RM A pfl Y mmB h Patented July 29, 1941 UNITED STATES PATENT OFFICE CIRCUIT INTERRUPTER vania Application January 24, 1940, Serial No. 315,372

8 Claims.

This invention relates to improvements in circuit interrupters, and more particularly to circuit breakers of the liquid immersed type. In United States Patent No. 1,942,294, issued January 2, 1934, to W. Kaufmann, is shown and described a circuit interrupter which operates on the expansion principle. Circuit interruption in accordince with this principle is accomplished by surrounding the arc with a vaporized fluid under pressure and suddenly decreasing the pressure of the fluid to effect a change of state from the super-heated to the saturated condition, which condition is caused to persist at least during the time the arc current passes through one current zero. The suddenly cooled vapor condenses on the electric charge carriers in the arc path to increase their mass to such a degree that their velocity is decreased to a value below that which is necessary to re-ionize the arc path under the influence of the rising voltage following a current zero. Further, in accordance with the patent, the sudden expansion of the vapor in the arc chamber is obtained by pressure responsively opening a plurality of vents close to and along the length of the are. We have discovered that the interrupting ability of a circuit breaker of the type disclosed in the aforesaid patent is quite sensitive to changes in the diameter of the arc chamber openings through which the moving contact operates, and that the interrupting capacity of a breaker of this type is limited to approximately 800,000 kva. at 15,000 volts.

The main object of our invention is to improve the interrupting ability of circuit breakers of the liquid immersed type in Which are extinction is dependent upon subjecting the arc to a turbulent blast of gas or mixture of gas and liquid.

Our invention contemplates the provision of a liquid immersed breaker having an arc chamber generally of the form disclosed by the aforesaid Kaufmann patent but which necessarily does not depend upon the expansion theory of operation to bring about arcextinction but which relies principally upon obtaining de-ionization of the arc stream by subjecting it to a turbulent blast of arc-extinguishing gas or mixture of gas and liquid.

The more specific object of our invention is to improve the interrupting ability of circuit breakers of the aforesaid type by the provision of venting means for the pressure chamber at or near one end thereof, so as to subject greater portions of the arc length to a more turbulent blast of arc extinguishing gas, and further to provide venting means, the opening of which is responsive to the pressure in the arc chamber for controlling the degree of venting inaccordance with the current to be interrupted.

A further object of the invention resides in improving the interrupting ability of liquid 1mmersed breakers by the provision of means for injecting additional liquid into the arc stream in response to opening of the vent in the pressure chamber.

Another object of the invention is to provide an arc chamber for liquid immersed circuit interrupters wherein the interrupting effectiveness is maintained to the end of the opening stroke of the moving contact member.

It is also an object of our invention to improve the general performance of a circuit breaker of the type above referred to by the provision of means for absorbing the sudden release of energy occasioned by venting the pressure'chamber, so as to relieve the breaker casing of disruptive stresses.

Other objects and advantages will be apparent from the following description when taken in connection with the accompanying drawings, in which:

Figure 1 is a sectional view illustrating the circuit breaker of our invention, taken along the line I1 of Fig. 2;

Fig. 2 is a cross-sectional view taken along the line IIII of Fig. l; and

Fig. 3 is a fragmentary sectional view showing a modified form of breaker construction. A

In the drawings, the reference numeral 5 designates a tubular casing member of insulating material having a metallic flange 1 secured to the lower end thereof. The flange member 1 has a plurality of outwardly extending lugs 9, from which is suspended, as by bolts H, a metallic casing member l3. Disposed between the tubular casing 5 and the casing member I3 is an annular support blade 15. Suitable gaskets, as shown, are provided between the meeting surfaces of the casings 5 and 13 with the plate I5, so that when the bolts I I are drawn up, a'liquidtight joint will be obtained. Bolted to the lower side of the annular plate [5 is a flanged cup-like member H which depends into the lower casing member l3. The cup-shaped member I! is preferably made of conducting material, and is utilized to support a stationary contact assembly l9 comprising a hollow cylindrical member 2| in which are disposed a plurality of yieldingly mounted finger contacts 23. Disposed within the annular plate l5 and resting upon the upper flange of the support I! is a ring member 25 of insulating material, which carries a plurality of blocks a! of insulatn. material of generally rectangular form, as more clearly shown in Fig. 2.

The blocks 2? have rounded corners and diagonal dimensions substantially equal to the inner diameter of the casin member 5. Ihe side edges of the blocks 2i are also preferably rounded so as to insure freedom of movement of the blocks in an axial direction of the cylindrical casing 5 for a purpose which will be more fully explained hereinafter. Each of the blocks 21 is provided with a central aperture 29 and an annularly disposed pocket 5! extending radially from the aperture 23. Thus the apertures 29 and the pockets 3! form a restricted arc passage rising above the stationary contact assembly l8. Resting upon the uppermost block member 27 is a tubular piston member 33 also of insulating material having a passage therethrough of a diameter considerably greater than the apertures 29 in the blocks 2?.

The upper end or" the piston member 33 is guided by a cylindrical guide member 35, which in turn is supported by a plurality of bolts 3'! carried by inwardly extending lugs 39 of a metallic cylindrical lining member ll. Disposed between the guide member 35 and the upper end of the piston is a ring 43 of resilient compressible material, such as rubber, which maintains the piston member 33 and the blocks 2'! in compression, as well as maintaining the entire assembly firmly seated upon the insulating ring 25. The transverse wall portion of the guide member is provided with a bushing 45 through which a movable contact rod 47 is adapted to operate.

The contact rod 4'! is preferably of a diameter slightly less than the apertures 29 through which it is adapted to move in making and breaking contacting engagement with the contact fingers 23. Thus the guide member the piston member 33, blocks 21, the insulating ring 25 and the support member I I provide a substantially closed pressure chamber in which an arc may be drawn upon the withdrawal of the contact rod 5'! from the stationary contact assembly [9.

The upper end of the metallic tubular member ll has an outwardly extending flange 49, to which is secured a support plate 5|. The plate all has a recessed portion 53 carrying a guide member through which the contact rod 41 is adapted to be moved. Also secured to the plate Si is a hollow casing 57 which houses the moving contact operating mechanism generally indicated at 59, whereby the contact rod 41 is operated to open and closed circuit positions.

An electrical connection is made from the upper end of the contact rod 4'! by a flexible conductor 61 to a terminal 63 which serves as one of the line terminals for the interrupter. The other line connection may be made to a terminal connector secured to the annular plate l5. Thus an electrical circuit is established through the interrupter by way of line terminal 83, flexible conductor 83, movable contact 41, stationary contact assembly !9, support member ll, annular plate i5 to the other line terminal 65.

The casing 5 is preferably filled with are extinguishing liquid. to a level so as to completely immerse the pressure chamber and maintain the same completely filled with liquid. In order to insure that the pressure chamber, as defined by the piston member 33 and the blocks 27, is maintained filled with liquid, the insulating ring member 25 may be provided with a plurality of vent passages 61.

The operation of the interrupter is as follows: In the event it is desired to open the circuit interrupter under conditions of load, the operating linkage 53 is actuated by a suitable operating mechanism (not shown) to raise the moving contact rod l"! to disengage the contact rod from the contact fingers 23, and thereby establish an arc in the apertures 29 and the liquid retaining pockets 3!. As soon as arcing takes place, pressure builds up within the pressure chamber and reacts upon the lower pressure exposed area of the lowermost block 23. Inasmuch as this area is greater than the upper area of the tubular piston member 33, the net result is to move the block assembly 27 and the piston 33 upwardly. Thus the pressure chamber will vent between the lower block 21 and the insulating ring 25. During the interruption of very low currents the pressure within the arc chamber may not be sufiicient to raise the blocks 21 from the ring in which case venting of the arc chamber takes place through the permanent passages 61.

The gases formed by the action of the arc on a liquid turbulently intermix with the arc stream and pass longitudinally thereof through the vent opening, as above described, and hence pass upwardly around the outer sides of the blocks 27 through the arc extinguishing liquid to the space above the liquid in the upper end of the casing 5. In the event that water is used as the arc extinguishing liquid, it will, of course, be understood that a greater percentage of vapor produced is in the form of steam, and will condense in passing through the body of liquid contained outside of the pressure chamber. The gases rising from the liquid, including the permanent gases, which are formed as a result of the action of the arc, are permitted to escape through an opening 69 disposed in the plate 5| into an exhaust stack ll provided on the side of the casing 57. Baflle plates I2 are provided in the stack ll for separating the liquid and gases discharged into the stack and also serve to condense the escaping water vapor.

It should also be understood that insulating liquids may be used in the interrupter forming greater quantities or" non-condensable gases, which will also rise to the surface of the liquid and escape through the exhaust stack H, as before mentioned.

It will also be noted that as the blocks 21 are raised, the piston member 33 is forced against the rubber ring 43 and displaces liquid from with in the guide member 36 axially of the moving contact 41 into the arc stream. It has been found that this liquid displacing action has been materially effective in increasing the interrupting capacity of the breaker, in that relatively cool liquid is mixed with the vapor so that at the first or second current zero the dielectric strength builds up more rapidly, thereby making re-ignition of the arc impossible.

During the circuit interrupting operation arcing is more severe in the region just above the stationary contact assembly 19 and decreases in intensity with an increase in arc resistance as the arc is lengthened. The insulating material defining the arc passage or pressure chamber is, therefore, subject to greater erosive effects at or near the stationary contact assembly l9 than at points more remote from the assembly. The repeated action of an are upon the inner walls of the pressure chamber make it necessary to .or blocks --21.

replace the pressure chamber at given intervals in order to maintain the interruptingefiiclency of the breaker at a high value. Inasmuch as the erosion of the pressure chamber takes place principally at or near the stationary contact assembly [9, this particular portion of the pressure chamber is formed of a plurality of sections Therefore, in the event that the aperture 29 in the lowermost block 21 becomes enlarged to a degree influencing the efficiency of the interrupter, it merely is necessary to replace one block of insulation instead of the entire pressure chamber. The multi-section arrangement has the further advantagev over a solid construction in that the radially extending annularpockets 31 can be more easily provided in the former arrangement than in the latter.

It should be noted that the contiguous surfaces ofthe blocks. 21 are confined to a relatively small annular area about the apertures 29. .Thisis accomplished by reces-sing the middle and lowermost blocks 21, as shown at 13 in Fig. 1. Thus, if there is any tendency for the blocks 21 to separate by pressure acting between the contacting. surfaces, this pressure is so quickly dissipated through the recesses 13 that it cannot be maintained, and causes the blocks 21 to remain in contacting engagement and move as a unit to vent the pressure chamber only at the lower end at the gap formed between the lower i block 21 and the insulating ring 25, By thus keeping the blocks 21 and the piston 33 in contacting engagement, the entire movement of gas formed by the action of the are as it is drawn upwardly through the blocks is longitudinally of the arc in a direction opposite to that of arc movement which also assists in arc extinction.

Inasmuch as interrupters of the type herein described develop sudden changes in pres-sure within the interrupting chamber and surrounding casing, suitablemeans are required for absorbing the energy when the pressure within the pressure chamber is released. Absorption of the energy upon opening of the vent from the pressure chamber may be accomplished by the use of a plurality of elastic bodies 15 disposed about the support member I! in the lower casing member 13. The elastic bodies 15, for example, may constitute rubber hose filled with air. A further form of energy absorbing means is shown in Fig. 3 which is similar in all respects to Fig. 1, with the exception that the support member I! is provided with a downwardly extending annular member 11 disposed in surrounding spaced relation so as to form an annular gas pocket 19. When the pressure chamber in the arrangement shown in Fig. 3 is vented by the upward movement of the blocks 21, the energy thus imparted to the liquid in the casing l3 will be absorbed by the elastic body of gas trapped in the annular space 19 and thereby relieve the casing of the interrupter of disruptive stresses.

From the foregoing description, it is to be understood that the various parts of the interrupter are constructed of materials most suitable to resist action of the are and corrosion of the particular liquid used to extinguish the arc. For example, in the event that water is used as an arc extinguishing liquid, the metallic parts are preferably made of brass or bronze which will resist the corrosion of water. The insulating parts, such as the casing 5, the block-s 21 and the piston member 33, are preferably constructed of resinous material of either molded or compressed form such as will withstand the action of water. It is also desirable in this instance to use a resilient ring 43 of rubber. However, in the event of the use of oil as an arc extinguishing liquid, many of the metallic parts, such as the guide member 35 and the casing I3, may becons'truoted of steel, and the resilient member 43.may bereplaced by a steel spring. The insulating member 33 and the blocks 21 in the latter instance would preferably be made of fibre or similar arc-resisting material.

Although we have shown and described a specific circuit-interrupting structure and have enumerated several materials, the use for which we have a preference, it is to be understood that the same is for the purpose of illustration, and that changes and modifications may be'made by those skilled in the art without departing from the spirit and scope of the appended claims.

We claim as our invention:

1. In a circuit interrupter, relatively movable contact members for opening and closing the circult, an arc extinguishing device surrounding said cont-act members comprising mean of insulating material defining a side wall member and end members to provide a substantially closed pressure chamber, arc extinguishing liquid in said chamber, means supporting said waltmember for relative movement with respect to said end members in response to arcing pressure within said chamber, said wall member separating from one of said end members during said movement to provide a vent opening for said chamber, and means coacting with the other end member and said wall member operative in response to movement of the latter for moving a quantity of are extinguishing liquid through said pressure chamber towards said vent opening.

2. In a circuit interrupter, relatively movable contact members for opening and closing the circuit, an arc extinguishing device surrounding said contact members comprising means of insulating material defining a side wall member and end members to provide a substantially closed pressure chamber, arc extinguishing liquid in said chamber, said side wall member being disposed in movable relation with respect to said end members and movable in response to pressure within said chamber away from one of said end members to establish a vent between said side wall. member and said one end member, resilient means for biasing said side Wall member into engagement with said one end member to normally close said vent, and means responsive to movement of said w-all member toward the other of said end members for moving a quantity of said are extinguishing liquid toward said vent.

3. In a circuit interrupter, a casing including a plurality of sections defining an elongated arc passage having a constricted portion and a portion of greater cross-sectional area and end members closing said passage to provide a pressure chamber, arc extinguishing liquid in said casing, resilient means biasing said sections together and towards one of said end members, and separable contacts within said casing for establishing an are along said are passage, said sections being movable as a unit in response to predetermined pressure conditions within said chamber to establish a vent between said one end member and the constricted arc passage end of said casing, and means responsive to said movement of said sections to cause liquid to be displaced from the larger portion of said are passage to the constriated portion of said passage.

4. In a circuit interrupter, an arc extinguishing device comprising a body member having a passage therethrough and end members closing said passage to define a pressure chamber, arc extinguishing liquid in said chamber, and contact members separable in said chamber to establish an arc, said body member being disposed for relative movement with respect to said end members and having difierential pressure reactive areas arranged to cause movement of said body member away from one of said end members in response to are pressure within said chamber to provide a vent opening between said one end member and said body member, and means responsive to movement of said body member for displacing a quantity of liquid longitudinally of said passage to assist extinction of the arc.

5. In a circuit interrupter, a support member, a stationary contact mounted thereon, a coacting movable contact, a body member having a passage therethrough, means biasing said body member into engagement with said support member to close one end of said passage, said movable contact being operable in said passage to establish an arc therealong, and an end member having a cavity therein leading to said passage and closing the other end thereof, and being arranged for relative movement with respect to said body member, are extinguishing liquid filling said passage, said body member being movable away from said support member in response to predetermined pressure conditions in said passage to establish a vent only at said stationary contact and into the cavity of said end member to force a quantity of arc extinguishing liquid longitudinally of said passage in the direction of said stationary contact.

6. In a circuit interrupter, a stationary contact, a coacting movable con-tact, an arc extinguishing device including a substantially closed pressure chamber surrounding said contacts, arc extinguishing liquid in said chamber, said pressure chamber including a plurality of wall sections, a plurality of said sections having their inner walls recessed to provide liquid retaining pockets, and

means biasing said sections together and towards said stationary contact, said sections being movable as a unit against the biasing action of said biasing means in response to pressure in said chamber to establish a vent only at said stationary contact for decreasing the pressure and for causing a blast of liquid longitudinally of the arc.

7. In a circuit interrupter, wall means of insulating material defining an elongated arc passage, a stationary support normally closing one end of said passage, a hollow casing enclosing the other end of said passage, said wall means having limited longitudinal movement between said support and casing, a quantity of are extinguishing liquid in said arc passage, means for establishing an arc in said are passage, and resilient means disposed in said hollow casing for normally biasing said wall means toward said support, said wall means having inner surface areas so arranged to cause the pressure produced by the arc to move said wall means against the action of said resilient means to open a vent between said support and said wall means, and move said wall means into said hollow casing to force a quantity of said are extinguishing liquid from said casing through said are passage,

8. In a circuit interrupter, a hollow support, a stationary contact Within said support, a plurality of sections of insulating material disposed in contiguous relation upon said support, said sections having an opening therethrough to provide an arc passage, said support normally closing one end of said passage, a movable contact coacting with said stationary contact and actuable through said sections to establish an arc in said passage, arc extinguishing liquid in said passage, a hollow casing member disposed in telescopic relation with the end one of said sections and adapted to close the other end of said passage, and a resilient member disposed in said hollow casing for biasing said sections as a unit toward said support, said are passage within said sections having pressure reactive surfaces so arranged to cause movement of said sections as a unit against said resilient member in response to pressure within said passage for opening a vent between said support member and the adjacent insulating section, and further to cause one end section to displace arc extinguishing liquid from said hollow casing member and establish a flow of said liquid through said arc passage.

BENJAMIN P. BAKER. YVINTHROP M. LEEDS.

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