US3048683A - Extinguishing chamber for oil circuit breaker - Google Patents

Description

Aug. 7, 1962 H. FORWALD & 5

EXTINGUISHING CHAMBER FOR OIL CIRCUIT BREAKER Filed Sept. 16, 1959 2 Sheets-Sheet 1 z z//// //////I/// INVENTOR. orwa [d flforn ex.

Han/ron T 2 Sheets-Sheet 2 H. FORWALD EXTINGUISHING CHAMBER FOR OIL CIRCUIT BREAKER Aug. 7, 1962 Filed Sept. 16, 1959 INVENTOR. Haakon ?bum Id -flornef United States Patent O 3,048,683 EXTINGUISHI'NG CHAMBER FOR OIL CIRCUIT BREAKER Haakon Forwald, Grottvage 31, Ludvika, Sweden Filed Sept. 16, 1959, Ser. No. %46,333 Claims priority, application Sweden Oct. 4, 1958 7 Claims. (CI. 200-150) In extinguishing chambers for oil circuit breakers it is already known to conduct the breaking gases generated by an arc from a pressure generating chamber, which surrounds the said breaking gap, through separate metal pipe channels provided with back valves, to an annular closed space above the oil surface in the extinguishing chamber. The oil below the annular space is in communication with the -breaking gap through other channels which channels, however, during the first part of the breaking action are closed by the movable contact and are not opened until this has been fully drawn out of the pressure generating chamber, so that the oil is forced by the pressure in the annular space through the last mentioned channels against the arc.

By conducting the breaking gases through separate channels from the breaking gap to the `annular space it is desired to cause the Volume of this space to be held constant, and not upon breaking pressed together by the rising of the oil surface due to the gas bubbles, which are formed in the oil around the breaking gap and are not conducted away.

In both cases the same pressure is -obtained in the annular space but a different Volume, and as the energy which is accumulated in the annular space, is proportional to the product of Volume and pressure, it is easily seen that a larger Volume at one and the same pressure corresponds to a larger accumulation of energy.

In previously known devices, however, the chamber which surrounds said breaking gap has never 'been fully closed during the first part of a breaking action but has, in addition to the mentioned metal pipe channels been provided with at least one opening, through which the oil in the pressure generating chamber is in permanent communication with the oil below the annular space. Due to this it has never been possible to completely avoid during a breaking action the rising of the oil surface adjacent to this space. Further, the annular space, which is limited by the outer, cylindrically formed walls of the extinguishing chamber and an inner cylinder, has an unsuitable form as a pressure accumulating chamber compared to a cylindrically formed space arranged within the extinguishing chamber, the Volume of which is only lessened by that part of the movable contact it surrounds. This latter space has at the same Volume as the annular space a smaller limiting surface, on which thus the total pressure Will be smaller than on the limiting surface of the annular space, for the same inner pressure. From -a Constructive point of view this is an indisputable advantage. Lastly, to use as above separate metal pipe channels for the communication between the pressure generating chamber and the pressure accumulating chamber must involve considerable disadvantages. To obtain the same insulating resistance between the opened contacts of the breaker it is thus necessary to make the breaking gap between them larger, as a part of this breaking gap is bridged by said channels, and this, moreover, complicates the construction of the extinguishing chamber.

The present invention relates to an oil circuit breaker With the advantages of the said devce but without its disadvantages. The extingushing chamber of the oil circuit breaker constitutes a container, which has been filled With oil to a suitable level. In the lower part of the container a stationary contact is arranged in a pressure generating Patented Aug. 7, 1962 chamber, which is fully closed, except for an opening through which a movable contact may be passed in to the stationary contact. The invention is characterised in that within the container above the pressure generating chamber a pressure accumulating chamber is arranged, in the walls of which two openings for the movable contact are made, so that this can -be passed straight through the pressure accumulating chamber and through the opening in the pressure generating chamber to the stationary contact. The pressure accumulating chamber is filled with oil to a certain level and above the oil surface in this a space is formed, which during the first part of a breaking action communicates through a channel in the movable contact with the pressure generating chamber.

To make the oil in the pressure accumulating chamber and the pressure generating chamber rise to the same level as before the breaking action, the pressure accumulating chamber communicates through a lower opening in its wall facing the pressure generating chamber and the pressure generating chamber through its opening 'with the remaining spaces of the container by at least one connecting channel, when these openings are not closed by the movable contact. The walls of the connecting channel suitably constitute the adjacent walls of the pressure generating chamber and the pressure accmulating chamber, so that an annular slot is formed by the last said walls around the movable contact.

The extinguishing chamber can also be arranged to give a flow of the extinguishing medium perpendicularly to the arc, by providing the pressure .accumulating chamber, besides the two openings 'for the movable contact, with one more opening, through which the pressure accumulating chamber through a cross channel, which during the first part of the breaking action is closed by the movable contact, communicates with the container. This latter embodment of the invention gives a smaller width of the breaker pole.

To make as much use as possible of the pressure in the space above the oil surface in the pressure accumulating chamber, the channel in the movable contact leads from the foot point of the movable contact, said foot point facing the stationary contact, to an opening located in the wall of the movable contact at such a distance from the foot point, that the pressure generating chamber through said channel communicates with the space above the oil in the pressure accumulating chamber until the movable contact has been drawn out of the 'opening in the wall of the pressure generating chamber. About the same time the channel in the movable contact is cut off from its communication wtih -the pressure accumulating chamber. The axial flow of extinguishing oil, however, does not begin until the movable contact has been drawn out of the lower opening of the pressure accumulating chamber, upon which the oil in the chamber is forced by the pressure above the oil surface in said chamber against the arc and out through said opening. Due to the -fact that the pressure accumulating chamber, when the movable contact has been drawn out of its lower opening, communicates with the container through this opening as well as through the channel in the movable contact, an additional flow is obtained out through the movable contact during the breaking action.

The accompanying drawings show two different ernbodiments of the invention. FIGURE 1 shows an exting'uishing chamber for axial flow of the extinguishing medium along the ane and FIGURE 2 an extinguishing chamber for a flow of extinguishing medium perpendicular to the arc. FIGURE 3 shows a section on the line A- A of FIGURE 2.

In FIGURE l, 1 designates a container of insulating material in the lower part of which a stationary contact 2 is arrangedin a pressure generating chamber 3 which is closed except 'for an opening 4 for the movable contact 5 Inside the container 1 a pressure accu'mulating chamber 6 is arranged above the pressure generating chamber 3. The chamber 6 is provided With two openings, a lower opening 7 and an upper opening 8, which lie in alignment with the opening 4 in the pressure generating chamber 3. The container at its top is provided with a cover 9 of metal and `an opening 10. Through this opening 10 and the openings 3, 7 and 4 the movable contact 5 is passed in to the -stationary contact 2. The pressure accumulating chamber 6 is centrally arranged in the container 1 and at the same distance from the pressure generating chamber 3 with the help of supports 11 so that an annular slot is formed between the chambers around the movable contact 5, which slot 12 communicates with the remaining space of the container. The movable contact 5 is provided With `a central channel 13, which extends from the foot 'point of the movable contact 5 to the opening Min its wall.

The cover 9 is provided with a vent 15 for the breaking gases. The upper opening 8 in the pressure accumulating chamber 6 is provided with scaling rings 16 to tighten around the movable contact 5, so that a closed space 17 is formed above the oil surface in the chamber 6. The pressure generating chamber can :be suitably in communication with the container 1 through a safety valve 18 and a channel 19.

Upon a breaking action, gases of high pressure are generated around the are, which gases through the channel 13 and the openings 14 are led straight from the pressure generating chamber 3 to the space 17 above the oil surface in the chamber 6. This gas movement is continued until the movable contact 5 has been drawn out of the opening 4. [For this purpose the lower edge of the openings 14 should lie at such a distance (a) from the foot point of the movable contact, that, at about the same time as the foot point s drawn out of the opening 4, the openings are cut off from their communication with the space 17, due to the fact that they are drawn into the wall of the chamber 6. Furthermore, the channel 13 in the movable contact 5 should be so arranged that when the movable contact 5 has been drawn out of the lower opening 7 of the chamber 6, the chamber 6 will communicate with the container 1 :through the opening 7 as well as through the channel 13. The oil surface in the chamber 6 is held at the same level as long as the `lower opening 7 of the chamber 6 is closed by the movable contact 5. Because of this the pressure in the space 17 Will rise to the same value as the pressure of the breaking gases generated by the arc. When the movable contact during the 'breaking action is drawn out of the opening 7, the oil in the pressure accumulating chamber is set free and is forced by the pressure in space 17 against the arc and out to the container 1, partly through the opening 7 and the slct 12 and partly through the channel 13 and the openings 14 in the movable contact 5 so that the arc is extinguished. After `a breaking action the oil in the chamber 6 rises to the same level as the oil in the container 1 due to the chamber 6 communicating with the container 1 through the opening 7 :and the slot 12, at the same time as the space 17 communicates with the space above the oil surface in the container 1 thnough the channel 13 in the movable contact S.

FIGURE 2 shows an extinguishing chamber, which functions in principle the same way as in FIGURE 1 with the difference, that the pressure accumulating chamber is provided with an extra opening Zt), which is in communication with a cross channel 21. This communicates with the container 23 but is closed during the first part of a breaking action by the movable contact 22. Up- `on breaking action the pressure in space 24 is raised in the same way `as described 'for the space 17 in FIG- URE l, and when the movable contact 22 during its 'upward movement opens the cross channel 21 a. powerful flow of oil is forced by the gas pressure in the space 24 out of the chamber 25 through the opening 20 and the cross channel 21 against the arc which is thus extinguished. Thus the arc in this chamber is exposed to` a fiow :of oil which is directedrn-ainly perpendicularly against the arc. The advantage with this Construction is that as FIGURE 3 shows, it gives a smaller width of the breaker pole than a Construction according to FIGURE 1.

I claim:

l. Oil circuit breaker comprising a container, a body of oil partially filling the container, means forming a pressure generating chamber having a fixed upper wall in the bottom of the container, said wall having a single opening therethrough, a stationary contact within said generating chamber spaced from the fixed upper wall, means forming :a constant-Volume pressure accumulating chamber in the container above and having a bottom wall spaced from the upper wall of the generating chamber, said accumulating chamber forming means having openngs in its top and bottom walls aligned with the opening in the upper wall of the generating chamber, said body of oil only pantia lly filling the accunulating chamber, and a movable contact slidable through all said openings to engage the stationary contact, said movable contact having :a passage leading from the lower end thereof to an opening on the side thereof, the distance from the lower end of the movable contact to the lowest point of the opening therein being less than the 'distance between the uppermost contact area of the stationary contact and the top Wall of the accumu lating chamber, whereby said passage connects said chambers during the first part of the movement of the movable contact as it breaks contact with the stationary contact said container including a space on the outside of the accumulating chamber, oil only partly filing said space, said space comm-un-icating with the space between the upper wall of the generating chamber and the bottom wall of the taccumulating cham- =ber.

2. A circuit breaker `as claimed in claim 1 in which the distance from the top of the upper wall of the generating chamber to the top Wall of the `accumulating chamber is at least as great as the distance from' the bottom of the movable contact 'to the lowest point of the opening therein, whereby the generating chamber communicates through said passage with the space above the oil in the accumulating chamber until the movable contact has been drawn out of the opening in the wall of the pressure chamber.

3. A circuit breaker as claimed in claim 1 in which the distance from the top of the upper wall of the generating chamber to the top wall of the accumulating chamber is equal to the distance from the bottom of the movable contact to the lowest point of the opening therein, whereby `at the same time that the movable contact leaves the generating chamber the passage in the movable contact is cut off from its communication with the accumulating chamber.

4. In -a circuit breaker as claimed in claim 1, the pressure accumulating chamber having a third opening, a channel connecting said opening with the interior of the container outside the pressure accumulating cham-ber, the movable contact closing said opening during the first part of the breaking action.

5. An oil circuit breaker as claimed in claim 4, in`

which the genenating chamber communieates through said passage "with the space above the oil in the accumulating chamber until the movable contact has been drawn out of the opening in the wall of the pressure chamber.

6-. An oil circuit breaker as claimed in claim l in which at the same time that the movable contact leaves the generating chamber the passage in the movable contact is cut off from its communication with the `accumulating chamber.

7. An oil circuit breaker as claimed in claim 1 in which the generating chamber communicates through said pas- References cited in the file of this patent UNITED STATES PATENTS Davies Aug. 6, 1935 Ehrenberg et al. Apr. 7, 1936 FOREIGN PATENTS Great Britain June 23, 1937 Great Britain Sept. 1, 1937 Germany Feb. 6-, 1942 Great Britain Oct. 4, 1946

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