US2156974A - Method of and apparatus for nonarcing circuit interruption - Google Patents

Description

G. E. DOAN May 2, 1939.

METHOD OF AND APPARATUS FOR NONARCI NG CIRCUIT INTERBUPTION Filed June 12, 1955 gNVaTOR 79M? Zia w ATTORN EYS Patented May 2, 1939 UNlTED STATES PATENT OFFICE METHOD OF AND APPARATUS FOR NON- ARCING CIRCUIT INTERRUPTION 8 Claims.

The object of my invention has been to provide for the prevention of the formation of arcs during the interruption of electric circuits, and to such ends, my invention consists in the method of, and apparatus for, substantially non-arcing circuit interruption hereinafter specified.

In the accompanying drawing:

Fig. 1 is a diagrammatic representation of a form of apparatus, embodying my invention, and

19 Fig. 2 is a diagrammatic representation of another form of apparatus, embodying my inventicn.

While I shall illustrate my invention by the best embodiments thereof known to me, it is to be understood that my invention is capable of embodiment in many different forms, and for many different uses, and that it is not to be confined, either as to the method or apparatus aspects thereof, to the examples herein chosen for go illustration. My invention is based upon the following research:

Whereas, a stable are forms at the opening of an electrical circuit under ordinary conditions; that is, an arc which for a given potential differg5 ence between the electrodes, and for a given length of separation of the electrodes, will carry a high and frequently destructive amount of current, I have discovered that, if conditions of very great purity are provided for in the separating electrodes and in the atmosphere about them, no such stable arc will form. On the contrary, an unstable, weak discharge, of transient and wandering nature, appears and rapidly goes out, without apparent action upon the electrodes.

For instance, when iron electrodes of very great purity are touched and then separated, in an atmosphere of highly purified argon, the usual stable arc does not form, but rather a transient discharge of low stability which rapidly goes out,

even with a separation of the electrodes and with an applied voltage of 120 volts. Under ordinary conditions of purity, these voltage and arc-length conditions would give a stable arc and one destructive to the electrodes. The iron in 4,5 this case was prepared by the repeated solution and extraction, by recrystallization, of iron oxalate from a solution of distilled water; the oxalate was heated to ferric oxide, the oxide reduced by hydrogen, as finely divided iron, and

was then sintered and swaged and drawn into a wire. The wire was de-gasified by heating in a vacuum and sealed off in the evacuated glass tube while hot. After cooling in the evacuated glass tube, the iron may be exposed to air at room 5 temperature without contamination. The argon was purchased with a total purity content of approximately 99%, and was further purified to a purity of about 99.3% to 99.6% by treatment for several hours in the discharge of a misch-metal arc formed in a bulb which was connected with 5 the arc-testing chamber. The impurities contained in the argon purchased were mostly nitrogen and water vapor and some carbonaceous gases. 'Misch metal is an alloy obtained in the rare earth industry, containing cerium, lantha- 10 num, and other metals which absorb hydrogen strongly at room temperature, and react vigorously with oxygen and nitrogen at high temperatures. The high temperature for my purposes and for the vaporization of the metal is secured 15 by forming an arc of which the misch metal is one electrode. The metal thus vaporized reacts with all gases, except the inert ones, forming stable compounds which condense on the walls of the chamber in which the misch arc is formed, and leave the inert gas highly purified. Under these conditions of extreme purity, the above results were obtained.- But they were not fully obtained if the process of purification was not thorough and complete.-

Based on these facts, I have invented an appa ratus for and method of interrupting electrical -circuits, whether to function as a circuit breaker or in commutation or in other applications Where non-arcing circuit interruption is desired. This 30 process consists in withdrawing highly purified metal conductors, preferably iron, as the terminals of the circuit, in an inert gas, preferably argon, of great purity, as the environment of the circuit interruption. 35

' I have found by experiment that I am able to produce satisfactory arcless circuit interruption by the use of three of the five rare gases: helium, argon, neon, krypton, and xenon. It is indicated thatthe arcless interruption thus obtained is made possible by a general property of each of the rare gases.

' The rare gases were of the purity which may be specified as spectroscopically free from active gases, although in at least one instance, it con- 45 sisted of a mixture of rare gases; for example, eight-tenths of a percent. of helium in neon. In other instances, freedom of the gases from active constituents was of the order of 99.3 to 99.9 per cent. Under these conditions of lesser purity, the current interruption could be accomplished only I where smaller currents and lower voltages were involved. In this latter case currents of the order of five to ten amperes were interrupted, whereas in the cases of more complete freedom from active constituents in the gases, currents of the order of one hundred to one hundred fifty amperes were successfully interrupted without the forming of a stable arc.

I have observed that argonof 99.0 per cent. purity, the principal impurity being nitrogen with a little water vapor and carbonaceous gases, is entirely unsuitable for the practice of my invention and gives a stable arc whenever a metallic circuit capable of forming an arc is broken in this gas.

Concerning the metals used, three were tried, and all three of them were used successfully. They were the metals zinc, silver and iron. The

zinc was of spectroscopic purity, having been produced by distillation in a vacuum. It was baked at 360 C. in order to drive outany residual gases which it might contain. The silver was 99.999 percent. pure but contained spectroscopic traces of copper and iron. It likewise was baked at 600 C. to drive out any gases which it might contain. Several diiferent grades of iron were used. While my earlier experiments employed iron as pure as could be obtained, an iron which was shown by analysis to contain .07 per cent. oxygen and .0012 percent. hydrogen, my more recent experiments indicate that ordinary commercial mild steel functions successfully, provided the gas is drastically purified, as, for example, by the action of the welding arc. Thus, in argon of 99.3 to 99.6 percent. purity, ordinary steel electrodes are found to support a stable are, carrying approximately one hundred fifty amperes for several minutes. During this time, iron vapor is being liberated from the electrode tips. This very hot iron vapor seems to serve as an excellent getter or scavenger of any active gas molecules present, and combines with such molecules to form oxides, nitrides, etc. These compounds are pushed away from the hot region of the are by the freshly liberated vapors emanating from it. Once out in the cooler regions of the arc, the compounds condense leaving the inert gas purified by their removal. Soon the arc, operating now in a progressively purer atmosphere, becomes unstable and goes out of its own accord.

Under these conditions currents as high as 150 amperes can be interrupted without the formation of a stable arc.

I therefore conclude that the provision of an inert gas sufficiently free from active contaminations is adequate for the operation of my invention without the necessity of high purity in the electrode material.

I am consequently led to the following viewpoint:-

If the metals are spectroscopically pure and if the rare gases are spectroscopically free from active gases, the invention operates over a wide range of currents, voltages and pressures. It operates for silver, zinc, and iron in argon and for iron also in neon and helium. Probably it operates for all pure metals in all inert gases or mixtures of inert gases.

The purity of the electrodes may be spectroscopical in degree, but good results have been obtained in argon with the use of electrodes of commercial mild steel. In this case, it may be necessary to give a drastic purification to the gas just before the electrodes are separated, but if the gas is pure, the invention operates even with impure electrodes.

It is clear that the conditions of purity above described may be obtained in other than the above methods. -I do not wish, therefore, to be limited to the above methods of purification, nor to the above metal (iron), nor gas (argon), but wish to patent a method and apparatus using metals or alloys preferably purified, but which may be only of commercial purity in an atmosphere of highly g purified inert gas for the interruption of electrical circuits, under whatever conditions it may be desirable to interrupt such circuits.

In the apparatus, which is diagrammatically represented in Fig. 1, pure iron electrodes A and 11 B are contained in a gas-tight electrically nonconducting container C, which, in this instance, is formed of glass; The electrode A is mounted fixedly in the container and the electrode B,

which is mounted in a guide, such as a tube, is 1| maintained in contact with electrode A, by a coil spring D. Leads E and F of the circuit to be interrupted are respectively connected with electrodes A and B. The electrode chamber is filled with pure argon gas, which is preferably at a 21 pressure of from 150 to 1200 mm. mercury, and especially above 760 mm. mercury. I have used current at from zero to volts and from 1 to amperes, but have expected and intended that my invention would apply to commercial currents 2.

and voltages. A solenoid, or electro-magnet G, placed either inside or outside the container, is

provided for the purpose of overcoming the pressure of the spring D and retracting the movable electrode B from the stationary electrode A, and 31 thus breaking the circuit.

If desired, a second container H, equipped with electrodes I and J to form a misch-metal arc may be attached at its top and bottom to the container 0 respectively by tubes h and h in a.

order to maintain the purity'of the argon gas. All parts inside of the container must be, as nearly as possible, gas free.

In Fig. 2, the pure iron electrodes K and L are mounted in a container M, the upper portion v of which may be of metal or glass, and the lower portion of which consists of a flexible metal bellows N which serves both as the lower portion of the container and as mechanical means tocause separation lof said terminals K and L.

Where the entire container is made of metal. the electrodes, or one of them, must of course be insulated from each other.

This application for patent is a continuation in part of my application for Method of and 51 apparatus for substantially non-arcing circuit interruption, Serial Number 589,638, filed January 29, 1932.

I claim:

1. A substantially non-arcing circuit breaker 5.

comprising a pair of iron electrodes, means for maintaining said electrodes in an atmosphere of argon of at least approximately 99.3% purity, and means for causing relative movement of said electrodes to bring them into and out of contact.

3. A substantially non-arcing circuit breaker 6:

comprising a pair of solid metal electrodes,.means for maintaining said electrodes in an atmos--- phere consisting of at-least 99.3% rare gas and means for causing relative movement of said m electrodes to bring them into and out of contact 4. A structure as specified in claim 3, in which.

-the atmosphere consists of at least 99.3% rare gas consisting essentially of argon.

5. A structure as specified in claim 3 in which 7 9,158,074 '3 the atmosphere of at least 99.8% rare in an atmosphere of rare and subjecting gas consisting essentially of neon. such gas to the action of a misch-metal are 6. A structure as specified in claim 3 in which until it is brought to a purity of at least 99.3%. the atmosphere consists of at least 99.3% rare 8. A method as specifled in claim 'I in which gas consisting essentially of helium. the electrodes are iron and the raregas employed 6 7. A method of preparing a substantially nonisargon of an initial purity of about 99% arcing circuit breaker which comprises enclosing a pair of relatively movable solid electrodes G'I. E. DOAN.

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