US2206709A - Electric circuit interrupting system - Google Patents

Description

July 2, 1940. c. G. surrs ELECTRIC CIRCUIT INTERRUPTING SYSTEM Filed Dec. 28, 1937 Fig.6.

Q I WNH w Patented July 2, 1940 UNITED STATESv PATENT OFFICE ELECTRIC CIRCUIT INTERRUPTING SYS TEM

New York Application December 28,1937, Serial No. 182,079

11 Claims.

My invention relates to electric circuit interrupting systems, more particularly to a method of and apparatus for interrupting a-power are by the application of steep front sound waves.

The interruption of a high voltage power are by conventional means, such as oil or magnetic blow-out switches, is often accompanied by certain difiiculties including fire hazard where oil is used, and high induced voltages with a possibility of flash-over and damage to the apparatus in the case of magnetic blow-out devices. Various other circuit-interrupting devices such as oil blast and gas blast breakers have been successfully used, but in general they are somewhat expensive and involve considerable design details, particularly where automatic pressure and blast control systems are used.

A principal object of my invention is the provision of an improved and simplified method of and apparatus for interrupting power arcs safely, quickly and with minimum disturbance. The extinguishing agent or medium for carrying out this method comprises a source of sound vibrations characterized by a comparatively steep wave front.

My invention will be more fully set forth in the following description referring. to the accompanying drawing, and the features of novelty which characterize my invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

Referring to the drawing, Fig. 1 is a diagrammatic illustration of an electric circuit interrupting system applied to a switch embodying the present invention; Figs. 2 and 4 illustrate diagrammatically other forms my invention may assume generally similar in principle to Fig. 1; Fig. 3 is a sectional view of spark gap apparatus having particular application to the present invention; Fig. 5 illustrates diagrammatically another form of my invention wherein a detonator is used as a source of sound vibrations; Fig. 6 is a sectional view of a lightning arrester embodying my invention, and Fig. 7 illustrates the invention as applied to a fuse.

I have foundthat the application of transient sound waves such as produced by an electric discharge or spark in air to an electric power are has an unusual and unexpected effect on the stability of the arc. When such sound waves, which are characterized by a comparatively steep wave front, are directed into the path of the power arc in a manner hereinafter described definite interruption of the arc occurs. The exact reason for this is not known, but there is reason to believe that the sudden and marked increase in pressure accompanying the transient sound waves is responsible to a large extent for the interruption of the arc.

High intensity continuous sound waves produced from oscillating crystals and magnetostriction oscillators have been studied forsome time. Transient sound waves consisting of a single pressure pulse produced from a spark in air, however, have not been explored extensively and many of their properties are unknown. Pressures which may be generated in these transient sound waves are very much higher than those produced from a continuous source, such as piezo electric crystals, for example. It has been calculated that a pressure of 40 atmospheres exists near the source of an exploding wire, this value, however, attenuating very rapidly within short distances.

The sound produced by an oscillatory 'or nonoscillatory spark in air consists of a spherically expanding single steep pressure wave which as observed photographically isapproximately one millimeter thick. This pressure front moves outwardly from the point of origin with a velocity that is initially high but soon attenuates to normal sound velocity not far from the source. The distance required for this attenuation to normal velocity depends upon the energy input into the spark and to a greater extent upon the rate of energy input. This pressure wave may be considered as the summation of two pressure waves, one of which, the normal sound wave, travels at a velocity of .331 10 centimeters per second (at 0 C.) and a second wave which may be called the puff, due to the heated body of air in the neighborhood of the discharge, that expands rapidly and propagates at a decreasing rate.

When sound waves of the above character are directed along the axis of a power are the arc becomes unstable and photographs of the arc clearly indicate the sound wave fronts in the arc space, together with turbulence and subsequent extinction of the arc. I have found by observation and test that the passage of a sound wave of the character above referred to through an arc is an agent in the extinction process, the same general results being observed with both A. C. and D. C. arcs in air. It has also been observed in oscillograms that the sound wave causes the arc voltage to rise abruptly, after which interruption occurs.

By way of example, in the case of a carbon arc of one centimeter in length'at 40 amperes 600 volts D. 0., extinction followed invariably upon the passage of a sound wave from a two microfarad condenser bank charged to 20 kilovolts with an L. C. frequency greater than 100,000 cycles per second. This is equivalent to a rate of energy input of 4X10 joules per second. The extinguishing effect can be increased when the spark gap is focussed by means of an ellipsoidal mirror upon the power are at the second focus.

Instead of using a reflector the sound wave may be directed by substantially confining the spark gap to an enclosure vented by a tube, for example.

As an alternative to generating a sound wave in air and passing it through an are as described above, a sound wave may be generated directly in the arc column by means of an electrode probe located in the arc space. The probe may be located some millimeters from either the cathode or anode electrode of the arc and in series with an external high voltage condenser circuit, so that the discharge passes between the probe and an arc electrode. This results in the production of an intense sound wave which expands spherically and passes through the arc.

The greater part of the energy is radiated in the form of sound, thereby indicating that high intensity sparks are the most eficient means known of converting electrical energy into sound. The are extinguishing agent used in the present case is therefore highly efficient from a practical view point.

Referring to physical embodiments of my invention, Fig. 1 illustrates an electric circuit breaker for an alternating current power circuit generally indicated at 6 comprising a pair of relatively movable electrodes or contacts 2 and 3. The contact 3 is pivotally mounted at i so as to be movable with respect to the fixed contact 2 for opening and closing the power circuit. The contacts are shown as of the abutting type, although it shall be understood that the present invention is not concerned with any particular type of contact construction. The operating means for the movable contact 3 may comprise any suitable manual, solenoid or motor device.

When the load circuit current is to be interrupted, separation of the contacts 2 and 3 draws a power are therebetween in a manner well known in the art. The arc-extinguishing agent or means comprises a source of sound vibrations which are characterized by a comparatively steep wave front as above described and produced in the present instance by means of an auxiliary circuit indicated at 5 including a spark gap defined by an electrode 8 and the breaker contact 2. The power circuit i and the auxiliary circuit 5 are interrelated by an inductive device ll constituting a transformer for inducing a high voltage in the auxiliary circuit in response to a sudden change in magnitude of the current in the power circuit occasioned by separation of the contacts 2 and 3.

The spark gap defined by the contact 2 and electrode 6 is in the present instance within the contact 2 and in communication with the point of separation of the contacts through a nozzleshaped or other suitablydesigned passage 8. The size of the spark gap is related to the inductive device i so that a predetermined change in current in the power circuit induces sumcient voltage in the auxiliary circuit to cause an electric spark discharge at the aforesaid gap. The high frequency spark discharge, which is characterized by a very sharp report, is directed into the path of the power are at the contacts 2 and 3 so as to extinguish the same at the succeeding zero value of current.

It should be understood that the means for directing the sound vibrations from the source or aaoaroe spark gap into the path of the arc may assume various forms and is not limited to the particular arrangement shown. For example. the contact 2 canbe provided with a reflector so that the sound vibrations are directed through the passage 8 toward a definite part of the arc path, or the spark gap electrodes may even be separated from the contact 2 for causing the sound vibrations to be directed into the arc.

It will be noted that the interrupting action is substantially coincident with separation of the contacts and ceases instantly after interruption of the circuit, 1. e. extinguishing of the arc. There is therefore provided a very simple and effective circuit interrupter having an automatic arc-extinguishing device which involves no inflammable insulating medium, requires no maintenance as in the case of oil and other switches, and which is effective to extinguish the power are quickly with no more attendant disadvantages than possibly the sharp report of the spark discharge.

Fig. 2 illustrates another form of my invention wherein the spark discharge for interrupting the arc is established in a somewhat different mannerfrom Fig. 1, the power circuit in the present instance having a direct current supply indicated at 9. The generator can be shun ed in the conventional manner by a condenser as shown. The relatively movable breaker contacts in the power circuit are indicated at l and II, and the auxiliary circuit forestablishing the spark discharge on opening movement of the contact ii at i2. The auxiliary circuit which includes a condenser charging resistance 12' is inductively related as in the previous instance at B3 to the power circuit and includes spark gaps at M and i in parallel with a capacitance IS. The spark gap i5 is located adjacent the arc path indicated at ill, a suitable reflector it being provided to direct the oscillations of the spark discharge directly into the arc path.

The spark gaps at M and iii in combination with the inductive device i3 produce upon opening of the power circuit what is known as the three sphere effect" wherein the spark gap l4 first breaks down under the additional induced voltage across the secondary of the inductive device i3, followed by immediate breakdown of the gap at E5. The capacitance it, which is normally charged in the closed condition of the power circuit, in discharging through the gap i5 produces the high frequency discharge of the character required for interrupting the power are.

Fig. 3 illustrates a specific form of spark discharge apparatus, or spark gun, so to speak, for utilizing the three sphere effect, for example, to direct the oscillations of a spark discharge into the path of a power are. The apparatus comprises a pair of electrode-supporting terminal members it which are mounted with respect to each other by insulating spacers 20. The upper electrode-supporting member has suitably mounted therein a conducting funnel-shaped member 29 open at its converging end 2| and closed by an insulating disc 2!" at its opposite end. Suitably mounted on the disc 2|" are a pair of interconnected electrodes 22 and 22, the electrode 22 being within the member 2| and spaced therefrom and the electrode 22' depending from the disc exteriorly of the member 2! so as to form a spark gap with another electrode 23 adjustably mounted at 24 in the lower supporting member H9.

The electrode 22 and the conducting funnel 2| in turn define a second arc gap in series with the arc gap 22'--23, so that when the device is electrically connected in an auxiliary circuit as indicated in Fig. 2, the breakdown of the gap at 2l- 22 establishes a source of steep front sound waves that are directed through the exhaust opening 2| into the power are (not shown).

In Fig. 4 the power circuit including the direct current source 9 as in Fig. 2 and breaker contacts l0 and H is provided as in the case of Fig. 3 with another form of auxiliary circuit 26 including a condenser charging resistance 28' and a capacitance 21 which is normally charged from the D. C. source in the closed condition of the power circuit. The condenser is caused to discharge through the spark gap at 28 in response to opening of the breaker contact I I. To this end the contact in the opening operation closes a circuit including the spark gap 28 in shunt with the capacitance at 29. For reasons well known in the art the capacitance 21 discharges through the gap 28 when the movable contact I I closes the circuit at 29. The oscillations of this discharge preferably take place within a suitable reflector 30 for directing the resulting steep front sound waves into the path of the power arc between the contacts In and H to extinguish the arc in the manner above described.

The interruption of the power circuit which takes place at the contacts i0 and H upon discharge of the capacitance 21 is complete for practical purposes even when the auxiliary circuit is made at 29 by reason of the comparatively high value of the current-limiting resistance at 31. However, it will be apparent that the contact at 29 may be but momentary if desired so that the contacts in the open circuit position assume the position illustrated.

Fig. 5 illustrates another source of intense sound waves for interrupting the power are between the contacts ill and II. In this case a detonator 32 is connected to a firing circuit 33 that is energized by the firing switch 34 in accordance with opening movement of the contact II. The detonator is preferably located within a reflecting tube 35 for directing the high intensity sound waves into the path of the are at ill-ll. The detonator, for example, may be of the type used in priming cups for exploding dynamite such as fulminate of mercury, or the like, capable of producing a violent explosion.

It has been clearly established experimentally that are extinction in the case of Fig. 5 is primarily effected by the steep front sound waves reflected from the tube 35 when the latter is suitably dimensioned, and not by a gas blast from the reflecting tube.

Fig. 6 illustrates my invention as applied to a lightning arrester of the spark gap type. The discharge circuit is indicated at 36 and includes a pair of gaps defined by electrodes 31 and 38, and 38 and 39 respectively. The gap 38-39 is substantially enclosed by an insulating tube 40 and the electrode 38 is formed as a tube so that the space adjacent the gap 3839 is vented only in the direction of the gap 3l--38.

Accordingly, breakdown of the gaps during a lightning discharge results in the production of high intensity sound waves at the enclosed gap 38-39 which are directed through the passage 38' of the electrode 38 directly into the series are at the gap 3l38. Interruption of the are at this gap results in clearing of the circuit.

In Fig. 7 my invention illustrated as applied to a fuse in a manner generally similar to Fig. 5.

The insulating fuse housing 4| through which the fuse terminals 42 and 43 extend, is provided with a partition 44 forming chambers 45 and 48 within which parts of the fusible element 41 are located as illustrated. The fusible element in chamber 45 is connected to an explosive charge or detonator 48 which is fired when the fuse blows or reaches a predetermined temperature.

For the purpose of directing the sound waves so produced into the arc resulting from blowing of the fuse in the chamber 46, the partition 44 is provided with an opening 44' immediately opposite the charge 48, and the opposite wall of the casing 4| is also provided with an alined opening 4| so that the sound waves can be reflected directly through the are. As in the case of Fig. 5, an intense steep front sound wave, rather than a blast or puff of gas or air. is relied upon as the arc-extinguishing agent.

In the circuit-interrupting arrangements above described the arc is in each instance extinguished by steep front sound waves produced by various methods. Although the spark discharge method may be preferred because of its simplicity, other methods of producing and applying the sound waves to the arc may obviously be used.

It should be understood that my invention is not limited to specific details of construction and arrangement thereof herein illustrated, and that changes and modifications may occur to one skilled in the art without departing from the spirit of my invention.

I claim:

1. An electric circuit interrupter operable in a gas such as air comprising arcing means at which the arc to be interrupted is formed, means for establishing adjacent to said are an electric discharge to cause a pressure wave, said wave characterized by a very steep front such as caused by high frequency electric discharges having a very high rate of energy input, and reflecting and focusing means for directing said wave into said are to extinguish it, the energy of said electric discharge being insuificient in itself to extinguish said are by air blast action.

2. An electric circuit interrupting system comprising arcing means at which the arc to be interrupted is formed in air, means for establishing also in air a pressure wave upon formation of said are, the minimum rate of energy input for said pressure wave being approximately 4X10 joules per second whereby said wave is characterized by a very steep front, and reflect ing and focusing means for directing said wave into said are whereby it is the primary are extinguishing agent.

3. An electric circuit interrupting system which comprises electrodes between which a power are is formed, means for establishing by and in accordance with formation of said power are an auxiliary electric discharge characterized in sound by a sharp report, and means for directing the sound vibrations of said discharge into the power are to extinguish the same.

4. An electric circuit interrupting system comprising a power circuit including relatively movable electrodes between which a power arc is formed, and an auxiliary circuit operatively connected to said power circuit for establishing a high frequency electric discharge upon separation of said electrodes, said discharge being related to said power are so that the oscillations of said discharge traverse said are.

5. An electric circuit interrupting system comprising a power circuit including electrodes between which a power are is formed, an auxiliary circuitincluding electrodes between which a high frequency electric discharge is formed, and means for causing the oscillations of said high frequency discharge to traverse said power arc.

6. An electric circuit interrupting system comprising a power circuit including electrodes between which a power are is formed, an auxiliary circuit including a spark gap, and an inductive device inter-relating said power and auxiliary circuits for causing an electric discharge at said gap in accordance with formation of said power arc, said gap being related to said electrodes so that the oscillations of said discharge traverse said are to extinguish the same.

7. An electric circuit interrupting system comprising a power circuit including relatively movable electrodes between which a power are is formed, an auxiliary circuit including a spark gap, and an inductive device interrelating said power and auxiliary circuits for causing an electric discharge at said gap in accordance with separation of said electrodes, said gap being related to said electrodes so that the oscillations of said discharge traverse said power arc to extinguish the same.

8. An electric circuit interrupting system comprising a power circuit including electrodes between which a power are is formed upon opening of the circuit, an auxiliary circuit including electrodes forming a spark gap, means defining a passage communicating with said spark gap and power arc, and means for causing an electric discharge at said spark gap substantially coincident with formation of said power arc, said spark gap being so disposed with respect to said passage and said power arc that the oscillations of said discharge traverse said power arc to extinguish the same. a

9. Anelectric circuit interrupting system comprising a power circuit including relatively movable contacts between which a power arc is formed upon opening of the circuit, an auxiliary circuit including a capacitance and a spark gap, and means operative upon separation of said contacts to cause discharge 01' said capacitance through said gap, said gap being related with respect to said contacts so that the oscillations 01' said discharge traverse said power arc to extinguish the same.

10. An electric circuit interrupting system comprising a power circuit including relatively movable contacts between which a power arc is formed upon opening of the circuit, an auxiliary circuit including a capacitance and a spark gap, 1

means relating said auxiliary circuit to said power circuit so that said capacitance is charged when the power circuit is closed, means operative upon separation of said contacts for causing said capacitance to discharge through said spark gap, and means for directing the oscillations of said discharge into the path or said power arc.

11. An electric circuit interrupting system comprising a power circuit including relatively movable electrodes between which a power are is formed upon opening of the circuit, an auxiliary circuit including a capacitance connected to said power circuit, said capacitance having in shunt relation thereto electrodes defining two arc gaps in a series, means for relating through an inductance one of said gaps to said power circuit, the other of said gaps being adjacent to said power are so that a discharge at said gap is eifective to extinguish said power arc.

CHAUNCEY G. SUITS.

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