US3704354A

US3704354A - Arc igniter circuit closing device and methods of operation thereof

Info

Publication number: US3704354A
Application number: US131929A
Authority: US
Inventors: Guy Jean Theodore Lagofun
Original assignee: Defense National France
Current assignee: Defense National France
Priority date: 1970-04-13
Filing date: 1971-04-07
Publication date: 1972-11-28
Anticipated expiration: 1989-11-28
Also published as: FR2086882A5; GB1352073A; BE764525A; DE2113798A1; NL7104662A

Abstract

An arc is struck across a gap between opposed contacts of a circuit maker by detonation of an explosive to produce a rapid flow of ionized gas and guiding the gas flow to the gap.

Description

United States Patent [151 3,704,354 Lagofun [45] Nov. 28, 1972 ARC IGNITER CIRCUIT CLOSING [56] References Cited DEVICE AND METHODS OF OPERATION THEREOF UNITED T PATENTS [72] Inventor; u Jean More Lagofun, 2,559,024 7/1951 McFaxlin ..3l7/66 R X ,Tarbes; France 3,179,851 4/1965 Smith, Jr ..317/66 R Etat- F cais Le 3,418,510 12/1968 Melhart ..3l7/60 R X Sslgnee: ran represe P ,5 ,00 19 11 ..20 1 B Minlstr' e Charge de La Defense Na- 3 00 9 3/ 70 Be 0/ 44 neleganon Mimsteneue pour Primary Examiner-Robert S. Macon men Attomey--Waters, Roditi, Schwartz & Nissen [22] Filed: April 7, 1971 1 21 Appl; No.: 131,929 [57] ABSTRACT An arc is struck across a gap between opposed con- 30 F A M D tacts .of a circuit maker by detonation of an explosive 1 orelgn pp ca .0 on y to produce a rapid flow of ionized gas and .guiding the 13, France 3 gas flow to the gap. 52 us. Cl. ..200/1'44 R, 200/148 G 1 m, 6 Drawing Figures [51] Int. Cl. ..H0lh 33/59 [58] Field of Search.....' ..200/144 R, 144 B, 148 G; 317/60 R, 66 R m 9 I0 8 12 /e sows a 0r/m1 ARC IGNITER CIRCUIT CLOSING DEVICE AND METHODS OF OPERATION THEREOF BRIEF SUMMARY OF THE INVENTION This invention relates to an arc igniter circuit closing device. I

According to the present invention an arc igniter is provided including means for striking an arc across a switching gapbetween opposed contacts of the circuit closing device when there is a high voltage across the gap, said means comprising an explosive charge" mounted fordetonation at a selected instant so as to' provide a rapid flow of ionized gas into said gap.

A circuit closing deviceembodying the present in-- vention may be used in testing other circuit closing devices at reduced power, while having the same effect as tests at operating power. By connecting a plurality of circuit closing devices embodying the present invention in series with one another and striking their respective arcs substantially simultaneously, high voltages may be switched without imposing an excessive overvoltage on any-one of the circuit closing devices.

BRIEF DESCRIPTION THE DRAWING For a better understanding of the invention, and to DETAILED DESCRIPTION FIG. I shows a circuit closingdevice I, which is to be tested and which is connected to two circuits simultaneously, one capable of supplying a test voltage at low current, and including a resistor 2, an inductor 3 and two

capacitors

4 and 5, serving for the production of oscillation conditions, and a spark gap G, while the other circuit serves for introduction of current under low voltage conditions; the sum of the powers delivered by these two circuits is about one-sixth of the actual test power I 4 The current circuit for limiting the current to a certain value achieves this by means of an auxiliary circuit closing device 6.

When a break in the circuit is produced by opening the circuit closing device 6, the arc across the opposed contacts of the closing device 6 is restruck by means of the detonation of an explosive charge so that a second test can be carried out substantially immediately after the first test. Thus tests can be reproduced substantially immediately, and this is sometimes necessary for the validity of circuit closing device tests.

It is desirable to be able simultaneously to switch several circuit closing devices connected in series in order to control the transmission of electric energy at very high voltages.

Until now. no single known circuit closing device has been capable of interrupting these very high voltages and it has proved necessary to employ-several circuit closing devices connected in series so that each indifficulty may thereby be avoided. The restrikingis effected even in the presence of an air blast in a switching chamber of the circuit closing device caused by blowing of air under high pressure (about 18 bars) tending to extinguish the arc. The time between the instant of firing the explosive charges and the instants at which respective flows of ionized gas reaches the respective opposed contacts may be as short as 30 microseconds thus making it possible to ensure the restriking of the circuit closing device during the same alternation of current chosen for sending the switching wave.

The dispersion of the propagation times between several circuit closing devices may be as little as 3 microseconds, and this permits them to be used in simultaneous operations for the restriking of several circuit closing devices connected in series. Thus, n circuit closing devices mounted in this way and each capable of supporting a maximum voltage U would be capable of causing the interruption of a total voltage of nU. The very simplified diagram of FIG. 2 shows the use of four circuit closing devices 7 connected in series.

The operational time of the explosive charge proper may be as little as 3 microseconds. v

The explosive used may be a secondary explosive, for example pentrite, which has the characteristic of having a high detonation volocity (8,000 m/s) and a thin and very conductive jet of ionized gas. By the term secondary explosive is meant an explosive charge whose detonation is produced by another charge (primary charge) detonated by a relatively small electrical or mechanical pulse, as is well known in the art.

The graph of FIG. 5 shows the characteristic of the displacement of the ionized medium which accompanies the detonation wave as a function of time outside the explosive. The speed of this wave is constant in the explosive, while it is supported by the exothermal chemical reaction of the detonation. After the departure from the explosive, it is no longer supported. The speed of displacement of the ionized medium first decreases very quickly with a constant deceleration of about 210 m/s', then it remains approximately constant when it reaches a fairly small value of the order of 1,500 m/s). The conduction qualities of this medium are maintained to a distance of about 20 cm from the explosive, in the case of a small charge.

. Taking these values into account, the ionized medium travels through the first I00 millimeters of its travel in about 27 microseconds, that is to say, at an average velocity of 3,300 m/s after leaving the explosive.

FIG. 3 shows the characteristic of the conductivity as a function of the thickness of the ionized medium inside the secondary explosive mass.

FIG. 4 shows the same characteristic, but when the ionized medium has undergone displacement by mm from the position at which the explosive was situated.

The resistivity of the front is 29 cm in the first case and about 100 cm in the second. However, the fact that the front is spread after leaving the explosive, increases the switching power in the zone of use.

The circuit closing device shown in FIG. 6 comprises a housing 8 carrying an explosive charge in a centering ring 1 l and provided with a guide channel 9 for the ionized medium. This housing is not destroyed by the detonation of the charge 10', only the centering ring 11 must be replaced, because it is deformed by the lateral forces of the detonation. The housing 8 can be recharged at will. It may be regarded as a cartridge supplied ready for use and recharged by the manufacturer. The user should have available a number of such housings. The housing 8 provides a high degree of safety for the operating personnel, since an inopportune. functioning of the explosive charge during manipulation does not pose any danger, provided that the guide channel 9 is not facing the operator. The housing is additionally fluid-tight at .a gas pressure of 18 bars.

A guide tube 12 for the flow of ionized medium is directed towards the gap between the contacts and 16 of the circuit closing device. This tube extends through an insulating wall 13 and a screen 14 of the circuit breaker, thus channelling the ionized, and hence conductive, medium over a major portion of the distance 100 mm) which separates the explosive charge 10 and the contacts 15 and 16. The tube 12 threadably receives the charge-carrying housing 8. The internal diameter of tube 12 is enlarged at the discharge end thereof, so as to provide directed expansion of the detonation front towards the contacts 15 and 16 of the circuit closing device. The contacts 15 and 16 are at a mutual spacing of about 3O mm, even under a pressure of 18 bars.

A cartridge-carrying belt 17 capable of receiving several charges is provided in alignment with the gap between the contacts of the circuit closing device for the purpose of reproducing the test automatically or improving the reliability of thesystem by simultaneous firing of several charges.

The explosive charge 10 is contained in a small cell, which also receives a system for initiating the operation, known as the exploded wire system, causing the detonation of a charge of lead nitride. The charge 10 comprises 200 mg of pentrite to which is added a variable quantity of barium nitrate, the purpose of which is to make the ionized medium more dense while reducing the brisance of the explosive. The firing of the charge 10 is effected by a coaxial connection 18. The connection 18 is protected from backward effects of the detonation by a screen 19. A ring 20 serves to maintain the explosive charge 10 in position. The mutual insulation of the initiating wire and of the initial charge of leadnitridehas the effect that the initiator is only able to cause'the detonation of the explosive charge from a certain electrical energy threshold value, which is very high (-of the order of 33-10 Joules). This quality makes the detonator insensitive to any intense electromagnetic fields in the area surrounding the place of use.

The possibilities of industrial application of this invention are concerned with the rapid switching operations carried out with a high precision as a function of time (a fcwmicroseconds), and independently of any mechanical inertia. This is of particular interest for the passage of high energies in a circuit at a very precise moment, the simultaneous switching of several circuit closing devices disposed in series and the rapid closing of an open circuit at the time of an accidental disconnection.

What is claimed is:

l. A circuit closing device comprising opposed contacts with a switching gap therebetween and means for striking an arc across said switching gap between said opposed contacts when there is a high voltage across the gap, said means comprising an explosive charge including a charge of a secondary explosive spaced from and facing said gap, and means for detonating said explosive charge at a selected instant to cause explosion of said secondary explosive and production of a rapid flow of ionized gas into said gap to strike said are.

2. A circuit closing device as claimed in claim 1, wherein said secondary explosive is pentrite.

3. A circuit closing device as claimed in claim 1, comprising a tube extending from said explosive charge towards the said gap for guiding said flow of ionized gas to said gap.

4. A circuit closing device as claimed in claim 3, wherein said tube has a widened discharge portion for guiding lateral expansion of said rapid flow of ionized gas as it travels longitudinally towards said gap.

5. A circuit closing device as claimed in claim 3, comprising a rechargeable cartridge for said explosive charge detachably mounted on that end of the tube which is remote from said gap.

6. A circuit closing device as claimed in claim 5, wherein said cartridge is fluid tight and it is threadably engaged in fluid-tight manner on said end of the tube.

7. A circuit closing device as claimed in claim 5, wherein a plurality of said cartridges are provided, each secured to a a guiding tube extending from the charge of the cartridge towards said gap.

8. A circuit closing device as claimed in claim 1,

' wherein said detonating means comprises an exploded wire detonator operable by the passage of electrical power exceeding a predetermined value through the wire, said detonator not being incorporated in said secondary explosive whereby the detonator is rendered insensitive to intense ambient electromagnetic fields.

9. A combination of a plurality of circuit closing devices as claimed in claim 1 having their respective opposed contacts connected together in series and their respective explosive charges adapted for detonation at substantially the same instant, thereby simultaneously to strike arcs across the respective switching gaps.

10. A method of striking an arc across a switching gap between opposed contacts of a circuit closing device, said method comprising positioning an explosive device containing a secondary explosive charge outside said gap but facing the same, detonating the secondary explosive charge and directing a rapid flow of ionized gas carried by detonation of the charge into the gap between the contacts to strike said are and close the circuit breaker when a high voltage is across the gap.

11. A method as claimed in claim 10 comprising guiding the flow of ionized gases from the detonated material to the gap between the contacts.

12. A method as claimed in claim '10 comprising simultaneously striking arcs across a plurality of circuit closing devices connected in series by simultaneously detonating explosive charges associated with respective circuit closing devices.

Claims

1. A circuit closing device comprising opposed contacts with a switching gap therebetween and means for striking an arc across said switching gap between said opposed contacts when there is a high voltage across the gap, said means comprising an explosive charge including a charge of a secondary explosive spaced from and facing said gap, and means for detonating said explosive charge at a selected instant to cause explosion of said secondary explosive and production of a rapid flow of ionized gas into said gap to strike said arc.

8. A circuit closing device as claimed in claim 1, wherein said detonating means comprises an exploded wire detonator operable by the passage of electrical power exceeding a predetermined value through the wire, said detonator not being incorporated in said secondary explosive whereby the detonator is rendered insensitive to intense ambient electromagnetic fields.

10. A method of striking an arc across a switching gap between opposed contacts of a circuit closing device, said method comprising positioning an explosive device containing a secondary explosive charge outside said gap but facing the same, detonating the secondary explosive charge and directing a rapid flow of ionized gas carried by detonation of the charge into the gap between the contacts to strike said arc and close the circuit breaker when a high voltage is across the gap.

12. A method as claimed in claim 10 comprising simultaneously striking arcs across a plurality of circuit closing devices connected in series by simultaneously detonating explosive charges associated with respective circuit closing devices.