US1942294A - Circuit breaker - Google Patents

Description

Jam 2E 1934. w. KAUFMANN CIRCUIT BREAKER Frgled June 27.1951 2 sheets-Sheet 1 Jan. 2, 1934. w. KAUFMANN 1,942,294

CIRCUIT BREAKER Filed June .27, 1951 2 Sheets-Sheet 2 l Patented Jan. 2, 1934 CIRCUIT BREAKER Werner Kaufmann, Berlin-Siemensstadt, Germany, assignor, by mesne assignments, to Westinghouse Electric & Manufacturing Com-f pany, a corporation of Pennsylvania applicati@ June 27, 1931, seria No. 541,297,11111 in Germany July 3, 1930 10 Claims.

My invention relates to electric circuit breakers operating on theexpansion principle.

The expansion principle of. circuit interruption consists in the surrounding of an arc'with a vaporized fluid under pressure, and then sudvdenly decreasing the pressure of the' fluid to effecta change of`state from the superheated to the saturated condition, the change of state being caused to persist at least during the time the arc current passes throughone current zero. The expansion and subsequent cooling of the vaporized fluid causes it to condense on the electric charge. carriers present in the arc path. Hereby, the mass of these charge carriers is increased to such a degree that their freedom of movement under the inuence of the returning voltage is greatly decreased. Reionization of the arc path is thereby prevented, and the arc remains extinguished. A v

Heretofore, circuit breakers operating on this principle have included a pressure chamber illed with a conducting or insulating liquid, prefera# bly water, Within which the separation of the contacts takes place. This chamber was kept closed during the steam-producing process until considerable internal pressure had developed. The

chamber was then suddenly opened to the ex terior space, the pressure was lowered, and the subsequent saturated vapor formation caused the extinguishment of the arc.

It has been suggested' to provide an arcing chamber having escape or outlet openings for the steam, which are entirely independent of the opening in the cover of the chamber for the movable conductingrod, this proposed arrange'- ment making it possible to dimension the outlet mechanisms for controlling the expansion solely in accordance with their function as such Withouthaving to consider other functions.

My invention relates particularly to a circuit breaker` with an arcing lchamber of the above mentioned type wherein independent outlets are provided for the vapo'r developed in the chamber by the arc. In the preferred structure, these outlets are kept closed by means of lclosing parts operated by special closing forces,\thus permitting the venting of the chamber without delay as soon as a predetermined internal pressure hasbeen attained. By this means it is possible to choose the moment for the beginning, and to accurately control the degree, of the expansion, irrespective of the magnitude of the arc current flowing at the time. With a chamber of this type, the heavycurrent arcs which result from the occurrence of short circuits are extinguished as readily as the the outlet controlling means.

(Cl. 20o-150) smaller current arcs resulting from the interruption of the controlled circuit kunder service conditions. v

The closing parts for the outlet openings, in the preferred form of my invention, comprise 00 parts of the chamber walls themselves, the chamber being built of members movable with respect to one another and biased toward each other by When the pressure of the vapor within the chamber exceeds the biasing force, outlets are formed between the adjacent movable parts. I have found it particularly desirable to utilize a casing for the vapor chamber which consists of members capable of moving with respect to one another in the vaxial direction and which. are held together by a spring v or springs.

As the arc extinguishing action Within anexpension chamber is most effective at the instant when the current 'passes through the zero value) 75 and since the operation of the outlet closing parts does not, as a rule, coincide exactly with a passage of the current through zero, the escape mechanisms for the vapor are so designed that, after responding to a predetermined overpressure, they so remain open until the pressure within the chami ber drops to a fraction of its initial value. One Way of accomplishing this is to make the parts controlling the expansion openings in such a manner that the areas of theparts exposed to the interior pressure are substantially increased by the movement of the parts accompanying the opening of the outlet passages. The effect of the interior pressure causing the Vexpansion process is thus increased many times at the instant in which the l expansion begins. Owing to the. substantial uniformity of pressure withinv the chamber, the Vexpansion effect takesrplace practically instantaney ously and the subsequent progressive increase in the area of the expansion openings permits the 95 continuing of the arc extinguishing operation with a maximum of effectiveness. 'Particularly satisfactory operation is secured by making the vent outlets open slots which are controlled by means having large surfaces laccessible to the interior pressure, as the time required for opening such a slot is very short.

'Another satisfactory structure includes a plurality of outlets which are distributed along the arc path Within the casing of the pressure 105 chamber. By this means a large expansion area can be formed in a short time, and in addition, since the resistance to the free outflow of the entrapped gas is minimized, the expansion from different parts of the chamber can begin simulcreased rate of decrease in pressure over the single vent structure.

The pressure chamber may be sub-divided by parallel insulating plates which have openings therethrough for closely engaging the conducting rod, annular parts being inserted between the insulating plates, so that the pressure chamber shall comprise a plurality of separate chambers. Each of the chambers of the structure has its own outlet formed by the lifting of the annular parts.

Embodiments of my invention are illustrated in accompanying drawings wherein:

Fig. 1 is a sectional view, partially in elevation, of an arcing chamber constructed according to the invention,

Fig. 2 is a sectional view, partially in elevation, of a modified form of arcing chamber surrounded by a condensing vessel,

Fig. 3 is a sectional view, partially in elevation, of a further modincation of my invention.

In Fig. 1 the expansion chamber consists of a metal vessel 10 having a thick flange 11 and an insulating cover 14. The insulating cover is connected to the vessel 10 by the bolts 12 and 13. The bolts are biased downwardly by the springs 17 and 18, abutting against discs 15 and 16 at the lower end of the bolts, and are adapted to slide in suitable holes in the flange 11. At their upper end, the springs 17 and 18 abut against the flange 11. The cover 14 is provided with a face or joint 19. The expansion chamber is mounted'on a supporting insulator 20 and is provided with a stationary contact member 21, which cooperates with the conducting rod 22 passing through a suitable opening in the cover 14. The means 23 indicates the surface of the liquid in the expension chamber.

This expansion chamber operates as follows:

The arc is established Within the pressuire chamber upon the separation of the contact members, the arc extinguishing liquid which is entrapped within the chamber is gassified by r the arc action, and the internal pressure increases until it reaches the expansion pressure,

,the time involved depending upon the amount of current flowing in the arc. Upon reaching the expansion pressure, the venting means operate to produce a sudden decrease in the internal pressure thereby changing the fluid surrounding the arc from the superheated state to the saturated state. The space in which the fluid expands may, for example, be a condensation vessel open to normal atmospheric pressure. The springs 17 and 18 are so adjusted that as soon as the predetermined expansion pressure is reached the cover 14 is raised from the edge of the pressure chamber 10. The gas entrapped within the chamber then escapes through the opened annular area, owing to the existing pressure-drop. When the current passes through zero, the entrapped lluid which has been cooled by the expansion and is, therefore, in the supersaturated state, condenes on the electric charge carriers in the arc path and effects the extinguishment of the arc. The rate at which the pressure drops when the expansion takes place is determined by the rate at which the expansion area is opened.

In order to open the vent passages as rapidly as possible, additional pressure surfaces are provided between the flange 11 and the outward part of the cover 14 resting on the flange.

The cover 14 is provided with a face or joint 19 ln order to prevent the entrapped fluid from taneously, thus producing a considerably inescaping before the expansion pressure has been reached. Were some means not provided to prevent a premature lifting of the cover 30, the venting action might be effected by the leakage before the necessary pressure had been built up within the chamber.

The expansion operation begins at the instant the cover is lifted and the bottom edge of the face or joint 19 uncovers the top edge of the flange 1l. At that moment an annular gap or vent passage is opened between the flange 11 and the cover 14 which is instantly filled with the escaping fluid under pressure. The surface on which the pressure acts is immediately increased by the area of the gap, thus increasing the force available to lift the cover 14, and upon further lifting of the coverl 14 a comparatively large annular area is made available to effect an enlarging of the vvent opening. This large increase in the available area for the vapor to press upon, prevents the cover 14 from reclosing under the'action of the springs 17 after the pressure has decreased, and as a result it is only after the pressure has dropped to a fraction of what it was when the expansion operation began that the force exerted by the springs 17 and 18 is sufficient to restore the cover of the expansion chamber 10 to the sealed position.

Referring to Figure 2, the circuit interrupter there shown includes an expansion chamber 26 of insulating material which is fastened by means of the pins 27 and 28 to a metal ring or flange 29. This metal ring 29 is fastened to the bottom of a condensation vessel 25 by the bolts 30 and 31. Suitable guide' openings for the bolts 30 and 31 are provided in the outer edge of the flange 29 in order that the flange together with the extinguishing chamber may be capable of slidable movement with respect to the base of the extinguisher. The springs 32 and 33, which abut against the heads of the bolts 30 and.31 and the annular ange 29, press the expansion chamber 26 into its position of rest against the base of the extinguisher. The stationary contactmember 34 is positioned within the pressure chamber and cooperates with the movable conducting rod 35 to open and close the electrical circuit. The level of the arc extinguishing fluid (indicated by the means 36) is the same both inside and outside of the expansion chamber since the condensing vessel 25 communicates with the expansion chamber 26 through a small opening 37. The opening 37 is so small, however, that any loss of pressure which might be caused by vaporflowing outwardly therethrough during the arc extinguishing operation is negligible. The face or joint 38 corresponds to the face or joint 19 in the previously described structure. i

The operation of this modification is likewise similar to that described above with the excep tion, however, that the vapor does not expand di rectly into the gas space of the surrounding condensing vessel but through the liquid filling the bottom part of 25. The expansion is thus aided by the intensive cooling and condensing action of the liquid surrounding the escaping vapor.

The'modiflcationshown in Fig. 3 comprises, generally, a' cylindrical insulating vessel or chamber having walls which are defined by a plurality of rings movable with respectto one another, in

vthe direction of the longitudinal axis of the chamber. Specifically Athe cylindrical vessel is supported on an insulating base member 41 which, in turn, is fastened to an insulator 40, and includes a short insulating cylinder 42 'rigidly joined to to permit the passage of the movable contact rod 51 which cooperates with the stationary contact 61 to open and to close the electrical circuit.

As will be described in some detail later, all of the rings 49 and the plates 44 to 48, inclusive, are movable with respect to each other to establish annular vent passages longitudinally along the.

arc path. This feature in combination with the division of the pressure chamber into. a plurality of separate chambersf-the opening in the spacing plates 49 being of but slightly greater diameter than the conducting rod 51-each of which is capable of independent separate operation makes possible a circuit interrupter capable of interrupting electric arcs of practically any current magnitude.

' 'Ihe cover 50 of the pressure chamber is also made of insulating material and is provided with an opening 51 to permit the passage of the conducting rod 52. The cover is fastened to the base member 41 by means of the guide bolts 53 and 54 whichare adapted to slide in suitable openings provided for them in the vbase member 4l.

The Shanks of the bolts '53 and 54 are covered with insulating` tubes 55 and 56 and serve to support and position the rings 44 to 49. The springs 59 and 60 abut against the end plates or discs 57 and 58 of the bolts 53` and 54, and by producing a downward pull upon the bolts resiliently bias the rings 44 toV 48, the spacing plates 49, and the cover 50 together. The pressure chamber is preferably positioned within an external closure which has a base 62 and which is partially filled with the arc extinguishing liquid. The liquid within the outer closure reaches the interior of the pressure chamber through the opening 51 for the conducting rod. The surface of the liquid'is indicated bythe means 63.

` The operation of the modication-shown in Fig.

3 is substantially as follows:

An arc is established Within the pressure chamber immediately following the separation of the contact members 52 andl. Some of the entrapped uid is gasified and builds up pressure within those parts of the chamber wherein the arc has been drawn by the movement of the contact rod 52. The pressure depends on the rate of gassification (a `function of the arc current), the rate of leakage at the opening for the contact rod 52 in the spacing plates 49, and the rapidity with which the superposed spaced chambers are opened to the effect of the arc (a function of the speed of movement of the contact rod 52). The gas is restricted at rst and its pressure acts only on areas of the small diameter d.

When arc currents of considerable magnitude are being interrupted sufficient pressure is reached within the chamber to cause operattion of the venting means (separation of the plates) when the conducting rod has moved but a short distance on its path. For some values of arc cur- A rent this occurs when the lower end of the conducting rod has reached the lowest plate 49, the gas filling only the lowest of the several chambers formed by the rings 44 to 48 and the plates'49. The springs 59 and 60 are so dimensioned that the force exerted on the circular surface of the diameter d by the expansion pressure overcomes the resistance of the springs at the predetermined value. yThe cover 50 is, therefore, moved upwardly; the rings 44 to 48 are loosened owing to the bolts sliding in the base member 4 1; and the springs 59 and 60 are compressed. However, since the pressure causing the upward movement of the separable plates is present only in the lowest chamber (or chambers) and since the effective working area is at once increased from an area of diameter d to one of diameter D, the upper rings 45 to 49 remain pressed together and the expansion or vent area opens only in the lower end of the chamber in the form of two (or possibly more) annular As explained previously, the additional surface created by the gaps, produces a force which tends to cause enlargement of the expansion area despite the resulting decrease in pressure. This results in a rapidand effective expansion of the entrapped gas.

When arc currents of low magnitude are being interrupted, the conducting rod 52'will travel a greater distance whilesuflicient arc extinguishing fluid is being gassied to produce the necessary expansion pressure. Thus the middle and the upper superposed chambers will also be filled lwith gas. Then, when the expansion pressure is reached annular' vent Apassages will be formed substantially simultaneously between spacing plates 49 and the rings 44 to 48. These gaps or vent passages which together form the several superposed chambers aremore or less equally opened and th'e expansion-takes place from all parts of the chamber. Alarge total area is thus made available for effecting the expansion and as a result a considerable pressure drop is effected in a very short space of tirne. The plates 49 may also be so made that their interior diameter is the same as that of the rings 44 to 48. If that is done, however, the feature of the sev eral separate chambers each capable of independent operation is lost.

-In the previously described inodication it has been presumed that for all magnitudes of are current the expansion operation and the extinguishment of the arc hasV been completely eiected before the conducting rodv 52 leaves the opening in the top of the chamber.

As an arc extinguishing medium for these circuit breakers, I prefer to use a liquid which forms a condensable vapor under the influence of the arc, water being a particularly suitable substance.

ings therebetween and means biasing said platesV toward each other.

v2. Ina circuit interrupter, relatively movable contact members for opening and closing the circuit, and an arc extinguishing device including Y tact members move to establish an arc, Aa bodyof liquid contained therein, the walls of said chamber comprising a stack of separable plates of insulating material which are movable to vent said a substantially closed chamber wherein said conchamber, and spring means biasing said plates toward each other.

3. In an electric circuit breaker, a fixed contact, a cooperating movable contact disposed for connection with and disconnection from said xed Contact, a casing forming a chamber arranged about said contacts, a iluid contained Within said chamber about said contacts and vaporizable by the a'rc occurring upon separation of said contacts, a plurality of plates arranged in stacked relation Within said casing operative to separate one from another in response to pressure created by the vaporization of said fluid upon occurrence of an arc between said contacts to thereby reduce the temperature of the vapor.

4. A circuit interrupter including an arc extinguishing device comprising a plurality ofcontiguous laminations defining a pressure chamber, contact members separable within said chamber, and means forrnorrnally maintaining said laminatlons in contiguous relation and for permitting said laminations to separate in response to excessive pressure internally of said casing' to relieve said pressure.

5. A circuit interrupter comprising a casing having a pressure chamber and comprised of a series of normally contiguous laminations, contact members separable in said chamber, and means yieldingly holding said laminations in contiguous relation and responsive to an excessive pressure internally of said chamber to yield and to establish vent passages between said laminations.

6. A circuit interrupter comprising a substantially closed pressure chamber, the walls of which are defined by a stack of separable plates, said chamber having a plurality of sections formed therein by some of said separable plates, means for establishing an arc within said chamber, and

means for drawing an arc within said openings, and means responsive to the pressure within each of said plurality of sub-chambers for individually venting said sub-chambers through the side wall of said chamber. 4

8. In a circuit interrupter, an arc extinguishing chamber having pressure resisting side walls that are normally substantially closed, a plurality of sub-chambers formed therein by a plurality of insulating plates having openings therethrough, means for drawing an arc through said openings into each of said sub-chambers successively, and means responsive to the pressure within each of said plurality of sub-chambers for venting each of said sub-chambers laterally through the side wall of said chamber.

9. In a circuit interrupter, an arcextinguishing chamber having side walls of insulating material and a plurality of partitions of insulating material dividing said chamber into a plurality of sub-chambers, said partitions having aligned openings therethrough, a contact member xedly mounted adjacent one end of said chamber, and a Contact member movable through said aligned openings to draw an arc from said xedly mounted contact into said sub-chambers in succession, each of said sub-chambers having means, responsive to the pressure therein, for individually venting said sub-chambers through the side Walls of said chamber, said venting means functioning successively as the arc is drawn into said sub-chambers.

10. In a circuit interrupter an outer casing a body of liquid within said casingv an arc extinguishing device likewise within said casing and comprising a pressure chamber that is normally substantially closed, the walls of said chamber being defined by separable members, contact means movable to establish an arc Within said chamber, and means for normally maintaining said separable wall defining members in contact with each other and for permitting said wall defining members to separate in response to the pressure Within said chamber to dene vat least one vent 'opening connecting with said outer casing.

WERNER KAUFMANN.

Images