US2541792A - Circuit breaker - Google Patents

Description

Feb. 13, 1951 THQMMEN 2,541,792

CIRCUIT BREAKER Filed Jan. 21, 1946 23 18 mumm o J 22 6 g Fig.

In van/or VLQMJW By QM WW A Horneys.

Patented Feb. 13, 1951 CIRCUIT BREAKER Hans Thommen, Baden, Switzerland, assignor to Aktiengesellschaft Brown, Boveri & (lie, Baden, Switzerland, a joint-stock company Application January 21, 1946, Serial No. 642,478 In Switzerland January 27, 1945 3 Claims.

for operation at the highest of voltages, since the are from the beginning of its formation is subjected to a most favorable blowing action and is.

bathed entirely by compressed gas, the space between the contacts having a true compressed gas insulation. Circuit breakers constructed in this manner possess a most desirable arc extinction characteristic and may have very high power ratings in comparison to their size. For improving the circuit-breaking and for preventing a rapid rise in returning voltage following an extinction of the arc, resistance has been connected in parallel with the switch contacts. The method has been disclosed of connecting the resistance in circuit with a spark gap, the electrodes of the gap being located one behind the other in the blowing chamber which adjoins the switch contacts. Such an arrangement makes it possible to combine one electrode of the gap with the hollow switch contact with the result that a spark gap can be placed so near to the switch contacts that it is located in the range of a most favorable blowing action by the gas as it emerges from the mouth of the hollow contact. Furthermore, the distance between the electrodes of the arc gap is small and consequently the ignition and extinction characteristics for the spark gap are satisfactory.

The spark gap in the compressed gas circuit breaker acts at the same time as an excess voltage leak, when for instance an inductive circuit is to be broken, where excess voltages can make their appearance. In order to be able to effect an extinction of the arc in the spark gap even during phase opposition, the spark gap must have a good insulation characteristic, this affecting its protective effect in ordinary circuit-breaking.

This invention relates to a compressed gas circuit breaker with at least one hollow switch contact and with spaced electrodes forming a spark gap located in the blowing chamber adjoining the contact. This spark gap when bridged by an arc connects a protective resistance in parallel with the switch contacts, means being provided according to the invention by which the actuating or striking voltage of the spark gap is changed automatically during an opening op- 2 eration of the circuit breaker so that at the beginning of a circuit-breaking operation, the voltage required to bridge the arc gap is small but increases during the operation and is finally brought back to its original value upon completion of the operation.

In the drawings, Figs. 1 and 2 are vertical sections of two dilierent constructional examples of circuit breakers embodying the invention.

Referring now to Fig. 1, the circuit breaker shown includes a pair of tubular insulating casings I and 2 which are separated by, and joined to, a hollow contact element 3.

The hollow contact element of the circuit breaker consists of an assembly which includes a member 4, a pair of telescoped conductive sleeves 5 and 6, an annular plate 8 secured to the bottom of sleeve 6 and a spring Ii] positioned between the underside of fixed member 4 and the upper side of plate 8. Telescoped sleeves 5 and 6 fit snugly for good electrical contact, and these sleeves are integral with or secured to the contact member 6 and contact plate 8. respectively.

The fixed contact member 4 contains a central opening II therethrough which is tapered outwardly from the bottom to the top in nozzle form. The openings through sleeves 5 and E, the opening II through contact member 4 and the opening I2 through plate 8 are all aligned so as to permit gas flow therethrough when the contacts of the circuit breaker separate.

The interior of casing I constitutes a blowing chamber Ia for the circuit breaker, part of this chamber also serving as a spark gap X defined by a pair of electrodes I3 and I4.

Electrode I3 is annular in form and is constituted by the mouth piece of an electrically conductive sleeve I5 which includes an upper cylindrical portion I6 and a lower tapered portion H. A muiller I8 is disposed within the top of the cylindrical portion I6.

As is clear from the drawing, the outer diameter of the cylindrical portion I6 of sleeve I5 is substantially the same as the interior diameter of easing I and the sleeve I5 is joined to casing I at the junction line between the upper and lower sleeve portions I6, II. Gas pressure in the space between the inside wall surface of casing I and the outside wall of the tapered portion ll of the sleeve I5 increases under the action of the gas blast and serves a function which will be explained in detail hereinafter.

Electrode I4 is a pin that is mounted for movement along the vertical axis of the circuit breaker. Pin I4 is slidable within a guide I9 of conductive material, the outside surface of pin [4 being in good electrical contact with the inside surface of guide l9. Pin I4 moves downwardly against the action of a spring 20, which is carried within guide l9, as gas pressure in the blowing chamber la increases. Thus the length of the spark gap X will vary with the magnitude of the gas pressure. The lower portion of guide [9 terminates in an L-shaped tube 2|, the end of which extends through the hollow contact member 4 to support the same and to provide a vent for the space beneath the pin l4.

One end of a resistance 22 is connected to a terminal 23 on sleeve l and hence is in good electrical contact with electrode is since sleeve I5 is made of electrically conductive material. The other end of resistance 22 is connected via terminal 25, a conductive casing 25 and conductive bracket 26 to a fixed contact 21 of the circuit breaker which normally is engaged with the spring loaded contact plate 8.

Connections from the line to the circuit breaker are made at line terminal 28 on conductive casing 25 and at line terminal 29 on the hollow contact member 4. From what has been described, it is now evident that resistance 22 and the spark gap X are arranged electrically in series and are connected across hollow contact member 4 and the fixed contact 22' of the circuit breaker.

When an opening operation of the circuit breaker is desired, pressure gas directed. upwardly from any suitable source through casings 2 and 25 impinges against the bottom of the contact plate 8 causing the latter to rise and hence break the electrical connection between the plate 8 and fixed contact 27. Pressure gas flowing through the opening I2 in plate 8 and upwardly through the sleeves 5, E and through opening ll surrounds the are formed between the opening circuit breaker contacts on all sides and blows it upwardly. The discharged switch gases ionize the spark gap X rendering the same conductive and hence switching in the parallel connected resistance element 22 which improves the circuit-breaking operation. As the gas continues to fiow through opening Is in the hollow contact member 4, pressure of the gas in the blowing chamber ia will increase causing progressive downward movement of the contact pin 14 which thus increases the length of the spark gap between the two electrodes I3 and I4.

If, during operation of the circuit breaker, excess voltage makes its appearance, the spark gap X acts as a leak inside of the circuit breaker. When the flow of pressure gas is terminated, the circuit breaker contacts 8 and 2'! will close, and electrode pin it will be moved back to its original position by the restoring force of compressed spring 20 as the gas pressure in chamber la decreases.

In the Fig. 1 arrangement, it will accordingly now be obvious that the actuating or striking voltage of the spark gap X is accordingly adjusted by changing the distance between the two electrodes i3 and i l as a function of the accumulated gas pressure in the blowing chamber ia so that such voltage will be comparatively small at the beginning of an opening operation of the circuit breaker, the voltage increasing however, during circuit breaker operation and finally at the end of the operation of the circuit breaker being brought back to its original value. In this way, a certain protective action of the spark gap is assured for circuit-breaking and as an excess voltage leak.

Referring now to the modified form of the circuit breaker shown in Fig. 2, it will be seen that the arrangement of parts is somewhat similar to that shown in Fig. 1; hence corresponding parts of the two circuit breaker constructions have been given like reference numerals but with primes added to the numerals used in Fig. 2 to distinguish between them. However, in the construction shown in Fig. 2, variation of the striking voltage of the spark gap during an opening operation of the circuit breaker is effected by a change in the accumulated gas pressure in the are blowing chamber rather than by a change in the distance between the two electrodes which form the gap. Thus, in Fig. 2, the position of electrode pin it with respect to annular electrode It remains fixed since electrode I4 is secured rigidly to hollow contact 4. A partition 3| containing a small opening 32 is placed transversely within the sleeve IS. A throttle valve head 33 is normally held away from opening 32 by a spring 34 but during an opening operation of the circuit breaker, the initial increase of gas pressure in chamber Ia causes valve head 33 to move upwardly and increase the resistance to fiow of pressure gas through the opening 32, thus further increasing the gas pressure in chamber la and likewise simultaneously increasing the striking voltage of the spark gap X.

The invention can be used in compressed gas circuit breakers provided with multiple or compound circuit-breaking, in which a plurality of sets of switch contacts are aligned one above the other to form a series of separate arcs as the circuit is broken.

In both constructions illustrated, the resistance element paralleled with the contacts of the circuit breaker could be placed concentric with the blowing chamber instead of as a separate structural part beside the blowing chamber. A semi-conducting coating could moveover be employed as a resistance, or the blowing chamber wall itself could consist of semi-conducting resistance material.

I claim:

1. In a pressure gas operated circuit breaker, a pair of switch contact elements, one of which is hollow, an arc blowingchamber adjoining said hollow contact, means supporting said contact elements for movement relative to each other under action of pressure gas to break connecticn therebetween, first, and second spaced elec trodes disposed in said chamber to define a spark gap, said first electrode being carried by said hollow contact and located in the path of the stream of pressure gas flowing therethrough, said second electrode being an annulus formed by the smaller end of a tapered sleeve set into and in contact with the wall of said chamber to form a pressure accumulating space between the exterior wall surface of tapered sleeve and the interior wall surface of said chamber, a resistance connected in parallel with said switch contact elements through said are gap, and means acting in response to a change in pressure of the gas in said chamber producing a corresponding change in the striking voltage of :said spark gap.

2. A circuit breaker as defined in claim 1, wherein said first electrode is spring loaded for movement away from the other in response to a rise in pressure in said chamber during an opening operation of said circuit breaker, for increas- 6 ing the length of the spark gap from a predeter- REFERENCES CITED mined value the beginning of the opening op- The following references are of record in the eration and decreasing to said value upon comfile of this patent, pletion of the opening operation.

3. A circuit breaker as defined in claim 1, 5 UNITED STATES PATENTS wherein said chamber includes an outlet for the Number Name Date escape of pressure gas from said chamber, and 2,290,004 Thommen July 14 1942 valve means responsive to a rise in pressure with- 2:367934 Flurscheim Jan 1945 in said chamber for throttling said outlet, said 2,391,826 Flurscheim 25, 1945 valve means being disposed within said sleeve 10 on the downstream side of said second electrode. FOREIGN PATENTS Number Country Date HANS THOMMEN- 538,672 Great Britain Aug. 12, 1941 597,533 Germany May 26, 1934 v 15 633,945 Germany Aug. 13. 1936

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