US2677740A - Arc-extinguishing oil-poor circuit-breaker - Google Patents

Description

Patented May 4, 1954 ARC-EXTINGUISHING OIL-POOR CIRCUIT-BREAKER Christian Henri. JoseplreMarie Allard, Paris, France Application March 14, 1951, Serial No. 215,580

Claims priority; application .France January 29, 1951 2 Claims. 1

My invention has for its object improvements in electric switches and circuit-breakers of the type wherein the current-breaking contactpieces are immersed in an arc-extinguishing liquid such as oil, said 011 being submitted to compression through an auxiliary arcing in series with the arc to be extinguished in order to direct an energetic jet of oil onto the latter. The current-breakers of this type are generally termed oil-poor circuit-breakers.

Such arrangements include generally a sliding spindle adapted to move inside a current-breaking chamber surrounded by and communicating with a coaxial tubular tank, said chamber being provided on one hand, with a main stationary contact-piece located at the end opposite to that provided with the sliding spindle and forming one of the terminals of the main arc, and, on the other hand, with an arrangement of intermediary contact-pieces.

The main object of the invention is to reduce the excess pressure generated in the tank by the main arc.

Another object of the invention is to provide such a reduction by the limitation of the length of the main are drawing between the sliding spindle and the stationary contact-piece. In fact, when the pressure generated by the auxiliary arc in the arc-extinguishing liquid is increased, the main arc is blown out and may consequently be conducted in the gas exit along an extended path, generally a curved path, before it attains the stationary contact-piece, which induces an excess pressure in the tank. With a view tominimize such a drawback, an electrically conductive electrode is connected with the stationary contact-piece and is located in the gas exit.

Further, when the arc-extinguishing liquid has curved the main are, it flows towards the tubular tank through the space existing between the current-breaking chamber and said tank. A pressure wave is then transmitted in said tubular tank and may generate considerable pressures which are capable to explode said tank even when it is made of an insulating material having a high mechanical resistance, which fact induces to very high cost price.

With a view to limit such an excess pressure, the'lower part of the current-breaking chamber is formed with an expansion chamber. The pressure wave is damped in said chamber by reflection and expansion, so that the resulting excess pressures in the tubular tank have a small value.

The combination of both said improvements further increases the above mentioned advantages. Owing to the fact that the length of the mainarc is limited, the pressure exerted in the current-breaking chamber has originally a value less than the value obtained in a similar circuitbreaker without supplementary electrode and, as the pressure wave is further clamped in the expansion chamber, the resulting excess pressures become unimportant and cannot cause the breaking by explosion of the insulating material forming. the tubular tank.

It is thus possible to preferably use porcelain as insulating material, said material, besides its dielectric qualities having a sufficient tightness to form the wall of the tubular tank, its mounting being very simple and safe owing to the fact that the sealing of such a material is easy. The manufacture of circuit-breakers is thus simplified, which fact gives an important saving in the cost price.

I have disclosed hereinafter, with reference to accompanying drawings, a preferred embodiment ofmy invention, said embodiment being given by way of a mere exemplification and by no means in a limiting sense. In said drawings:

Fig. l is a partial axial cross-section of a current-breaker according to my invention.

Figs. 2 and 3 are diagrammatic illustrations of the arrangement according to the invention respectively in its preliminary current-breaking and inits actual breaking position.

As illustrated, a cylindrical casing a of insulating material adapted to resist the pressure developed in the current-breaker, such as paper impregnated with a suitable plastic material, e. g. that known under the registered trade-mark Bakelite, encloses a currentbreaking: chamber b. Said cylinder at carries at its lower end a stationary tubular piece 0 connected with the lead line and through which current is fed' to the current-breaker. Said stationary piece carries main contact-pieces d submitted to the action of spring plates e secured by screws 1'. The current is switched on through the agency of a sliding contactpiece not illustrated which is connected with the return line and of a spindle g slidingly movable along the axis of the cylinder 17. with a clearance as small as possible. The current-breaking chamber b communicates freely through the channels it with an annular space i formed between the cylinder a and an outer insulating casing 7' of porcelain for instance, said annular space i and the current-breaking chamber 12 being filled with oil.

The spindle 9 made of an electrically conducit tive metal and forming the movable contactpiece, is provided with a lining is forming a spark arrester and the lower end of said spindle forms a. further conductive element 1 provided also with a spark arrester lining m which penetrates through the cylindrical space defined by the tubular piece 0, when the circuit is closed. Said element Z is separated from the body of the spindle through an insulating member n having a smaller diameter. The upper part of the spindle 9 slides inside a system of intermediary contact-pieces including a body formed by a single member of conductive metal and on which are mounted the auxiliary contact pieces 12 carried by spring plates q secured to the body 0 through screws 1*. The body 0 is guided and held inside the cylinder a through the agency of three insulating stays s.

In the gas exit illustrated at t is located an electrode at electrically connected with the lower piece or terminal c in order to limit the length of the arc.

The lower part of the tubular tank 1' forms an expansion chamber 1) having a great volume and wherein open the channels h. Near the electrode u is provided an oil-drainer for the currentbreaking chamber and the tank, said oil-drainer being closed by the threaded plug w.

The operation of the current-breaker is as follows:

When the circuit is closed, the contact-pieces p engage the electrically conductive body of the sliding spindle g slightly above the spark arresting lining is and the contact-pieces d engage the electrically conductive element 1 slightly above the spark arresting lining m.

When it is desired to break the circuit, the sliding spindle g is shifted in the direction of the arrow F in any suitable manner. As soon as the lining 1c has been disengaged from the contactpieces p, the auxiliary are A draws between said lining and said contact-pieces, as illustrated in Fig. 2. At the same time, the spark arresting lining m has moved with reference to the contact-pieces d and the main are P draws between said members. As the spindle is upwardly moving in the direction of the arrow F, the auxiliary are A generates the compression of the oil contained in the current-breaking chamber 1) in the known manner. This pressure generates a jet of oil that is directed onto the main are P which then follows a curved path through the cylindrical space defined by the stationary tubular piece 0.

Under the action of the increasing oil pressure generated by the auxiliary are A, the main are P becomes more and more curved inside said cylindrical space until it meets the electrode u and the latter limits the length of the final main are obtained, as illustrated at P1 in Fig. 3. Said final 4 main are is extinguished through the oil urged under pressure over the deflector m.

The reduction in length of the main are thus obtained has for its result a reduction in the pressure exerted by the jet of oil in the chambers.

Further, the pressure wave is damped by expansion and reflection within the annular chamber 12 so that the resulting excess pressure in the tank 2' is negligible, which fact decreases any risk of breaking the insulating casing 7' by explosion of the tubular tank.

What I claim is:

1. In an electric current-breaker of the type comprising a movable conductive spindle, a stationary tubular main contact-piece through which said spindle is movable, and auxiliary contact-pieces, and wherein the main are drawn between said spindle and the main contact-piece is blown out by a jet of arc-extinguishing liquid put under pressure by means of an auxiliary arc in series with said main arc and drawn between said spindle and the auxiliary contact-pieces; the combination which comprises a tank partially filled with an arc-extinguishing liquid, 9, currentbreaking chamber housed in said tank and communicating with the same through the stationary tubular main contact-piece, said chamber being immersed in, and filled with said liquid, both arcs in series drawing in said chamber, and an electrode directly connected with the tubular main contact-piece and the free end of which axially extends through said tubular main contact-piece near the zone where the main arc draws.

2. In an electric current-breaker of the type comprising a movable conductive spindle, a stationary tubular main contact-piece through which said spindle is movable, and auxiliary contact-pieces, and wherein the main are drawn between said spindle and the main contact-piece is blown out by a jet of arc-extinguishing liquid put under pressure by means of an auxiliary arc in series with said main arc and drawn between said spindle and the auxiliary contact-pieces; the improvement which comprises an electrode directly connected with the tubular main contactpiece and the free end of which axially extends through said tubular main contact-piece near the zone where the main arc draws.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,290,004 Thommen July 14, 1942 2,538,774 Friedrich et al Jan. 23, 1951 2,570,567 Lange Oct. 9, 1951 FOREIGN PATENTS Number Country Date 963,946 France Jan. 18, 1950

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