US3278801A - System of arc suppression for electrical switches and circuit breakers - Google Patents

Description

Oct. 11, 1966 J. E. CHAUVINEAU 3,278,801

SYSTEM OF ARC SUPPRESSION FOR ELECTRICAL SWITCHES AND CIRCUIT BREAKERS Filed March 28, 1962 P A W/ 7 7 I 91/ 524% 3 V W ATTORNEY United States Patent M 3,278,8il1 SYSTEM OF ARC SUPPRESION FSR ELECTRICAL SWITCHES AND CIRCUIT BREAKERS Jean Emilien Chauvineau, Lozere, France, assignor of fifty percent to Karl Kath, New York, NY. Filed Mar. 28, 1962, Ser. No. 183,266 4 Claims. (Cl. 31711) The present invention relates to a system of arc suppression in electrical switches or circuit breakers,,more

particularly, those of the type for use in electrical power circuits or networks designed to carry relatively heavy loads or currents, both A.C. and BC.

One of the major problems encountered in the design and operation of electrical switches and circuit breakers, especially those for use in high power circuits or networks, consists in the suppression of the intense spark or are discharge produced at the instant of separation of the switch contacts or interruption of the current flowing through the circuit or network being controlled.

Numerous remedial means and expedients have been suggested and used in the past in an effort to suppress or minimize the interrupting are produced in high power switches or circuit breakers, to prevent damage to or rapid deterioration and destruction of the electrodes and other defects well known. Among the known are suppression devices and methods, which while partly successful have never been able to achieve a complete suppression of the arc discharge, are the embedment of the electrodes in a highly insulating oil or equivalent liquid medium, the fractionization of the are into a series of elemental arcs, which while reducing some of the defects, does not result in a full arc suppression, the various arc quenching methods and devices, the mounting of the electrodes in an inert gaseous atmosphere, and many other devices and suppression methods none of which has been found fully satis factory in completely suppressing the interrupting are discharge or minimizing the defects resulting therefrom.

Accordingly, an important object of the present invention is the provision of an improved system of arc suppression for high power electrical switches or circuit breakers by which the foregoing and related difiiculties are substantially overcome or minimized.

A more specific object of the invention is the provision of a novel are suppression system especially suitable for use in high power circuit breakers or switches, by Which a practically complete elimination of the undesirable are discharge during the interruption of the current flowing in a circuit is achieved.

Among the remaining objects of the invention is the provision of a novel and improved arc suppression system of the type referred to which is both simple and economical in design; which is highly efficient and reliable in operation; which may be easily and readily embodied in existing circuit breaker and switch designs; and which will require a minimum of supervision during use and operation.

The invention, both as to its ancillary objects and novel aspects, will be better understood from the following detailed description, taken in conjunction with the accompanying drawing forming part of this specification and in which:

FIG. 1 is a circuit diagram illustrative and explanatory of the operation of the arc suppression method and operation according to the invention;

FIG. 2 is a theoretical diagram explanatory of the function and characteristics of the circuit shown by FIG. 1;

FIG. 3 diagrammatically illustrates a complete arc suppression system constructed according to the principles of the invention and embodied in a high power electrical switch or circuit breaker, the position of the contacts and control device corresponding to the closed circuit or operative condition of the circuit; and

3,278,801 Patented Get. 11, 1966 FIGS. 4 to 6, being fractional diagrams of FIG. 3, illustrate successive intermediate as well as the final or end position of the circuit breaker device during a complete current interrupting operation or cycle.

Like reference characters denote like parts and elements in the different views of the drawing.

With the foregoing objects in view, the invention involves generally the provision and utilization of a gaseous discharge tube or device, preferably a tube of the type for producing a high intensity relatively short or intermittent ionic or gas discharge current, such as used for instance in electronic flash light systems, stroboscopic devices, and the like, said tube being permanently connected across the interrupting contacts of the switch or circuit breaker. There is furthermore provided, according to the invention, means being synchronized with the circuit breaker control or operation to change the normal condition of said device of relatively zero ionization, or infinite electrical impedance (OFF state), to a condition of practically full ionization, or zero impedance (ON state), at the instant immediately prior to the initial separation of the circuit breaker contacts, whereby to cause the operating current to be bypassed through said device and to allow of a separation of the contacts substantially free from any spark or are formation, and without the defects and drawback-s resulting therefrom, in the manner as will become further apparent as the following description proceeds.

In a similar manner, the device is restored to its nonionized or high impedance state immediately after the contacts have arrived at a safe or the final end position. As a consequence, the suppressor tube, provided a proper design of the control mechanism of the circuit breaker, being called upon to conduct during only a relatively short period, may temporarily assume a considerable load or by-pass current, whereby to render the invention especially suitable for use in connection with high power switches or circuit breakers involving the interruption of load currents of the order of many hundred amperes and more.

As pointed out, gas discharge devices, including gaseous flash tubes, normally present a relatively high impedance to the passage of an electric current and, in fact, such tubes may be regarded as an interrupter or perfect insulator under ordinary conditions If, however, a potential difference or voltage of a sufl'iciently high value, that is, exceeding the ionization or critical breakdown voltage of the tube, is applied between the main discharge electrodes, the impedance of the discharge path suddenly changes to a very low value being equivalent to a practical short circuit. This, in turn, will enable the flow of an extremely high intensity current, provided provision is made to suppress the current or increase the impedance of the tube after a short duration, to prevent damage to or destruction of the tube. According to the present invention, the interruption of the discharge current is achieved by the synchronous ionization control by the circuit breaker operating mechanism. Ionization control or change between high impedance and low impedance, and vice versa, is advantageously effected by the use of an auxiliary control potential of a special type being applied to a separate control electrode of the tube, as will be further described in the following.

For the latter purpose, the invention utilizes an efiicient and reliable impedance control of the ionic suppressor tube synchronized with the operation of the circuit breaker. More specifically, the tube is provided with an auxiliary control electrode, preferably in the form of a capacitative electrode applied to the outside surface of the glass envelope, said electrode being excited by periodic peak voltage pulses for the control of the ionization or impedance of the tube. The control pulses may have a suitable repetition frequency and peak voltage such as to enable both the initiation and suppression of the ionization by the application and removal of the pulse voltage, respectively, in the manner described in further detail in the following.

Ordinarily, while the application of a starting voltage or potential to an auxiliary electrode of a gaseous dis charge tube may result in the ionization or breakdown, interruption of the ionic current cannot be effected by the mere removal of said voltage, whereby to make it necessary, in order to restore the high impedance of OFF state, to interrupt the main discharge or to reduce the main operating voltage to a value below the de-ionization or distinction voltage of the tube. This procedure is evidently not possible in an electrical power circuit including a number of load or consuming devices, as will be understood. On the other hand, the periodic peak control voltage as used by the present invention, enables an ionization or conductivity control between the full ON and OFF conditions of the tube by the application and removal, respectively, of the control voltage. This, in turn, enables the attainment of a sufficiently short ON or conducting period of the suppressor tube by the proper design of the circuit breaker control mechanism, to afford the intermittent passage or by-pass of considerable load currents as encountered in high power electrical circuits or networks.

Referring more particularly to FIG. 1 of the drawing, the numeral 10 denotes a gaseous discharge tube having a pair of main discharge electrodes, such as a tube for the production of relatively short high intensity instantaneous discharge as used in electronic flash lights or the like, said electrodes being connected in series with a source of voltage 11, which may be either AC. or DC, and a current limiting or load resistor 12. The critical or operating voltage of the tube 10 is below the operating voltage of the source 11, that is, at least one half or less the former, whereby the tube acts as an ionic switch or current interrupter devoid of mechanically moving parts. Applied to the outside of the glass envelope of the tube 10 is a capacitative starting or control electrode 13, such as in the form of a spiral wire wound around the tube as shown or a metallic coating applied to the outside wall of the tube, FIG. 3, or the like. Item 15 collectively denotes a periodic peak voltage generator producing a series of discrete ionizing voltage pulses p for the intermittent excitation of the electrode 13 by applying said pulses between the electrode 13 and one of the main electrodes of the tube, in the manner shown and readily understood.

As a consequence, short intermittent conducting periods of the tube may be established by temporarily applying the pulse voltage p, such as by the control of the generator 15 by the switch 20, to effect an arc suppression by by-passing the interrupting contacts of a switch or circuit breaker by the tube 10, in the manner further described in the following. The peak voltage generator 15 may be of any suitable type known in the art, but preferably consists of a transistor blocking oscillator as shown in the drawing, comprising a transitor 16 and a feedback and output transformer 17 designed to effect a sufficient voltage peaking to produce pulses p which, by way of example, may have a voltage of the order of 3000 volts, being substantially above the critical or breakdown voltage e (FIG. 2) of the tube 10, and a repetition frequency of from 3000 to 5000 cycles per second, although these values may be varied substantially according to the power or size of the circuit breaker or suppressor tube, respectively, to suit existing conditions and requirements.

As is well known, the blocking oscillator resembles a standard inductive feedback oscillator having a high feedback factor, whereby to result in a rapid rise of the emitter-collector current to full saturation of the transistor 16 upon closing of the switch 20. As the saturation point is reached, the feedback ceases suddenly, whereby to cause the current to fall, or to produce a short current pulses. The energy stored in the inductance of the base circuit is then allowed to discharge according to the time constant of the circuit, whereupon the operation is repeated, to result in a series of current pulses converted into the ionizing voltage pulses by the action of the peaking transformer 17. The pulse repetition frequency is determined by the time constant of the base circuit and may be controlled, for instance, by the variation of the resistance of the circuit. In place of the use of an inductive discharge reactance, a capacitor and leak resistance may be provided in the base circuit in accordance with conventional practice for the control of the intervals between the current pulses, this and other details of the peak voltage pulse generator being well known and forming no part of the present invention.

In place of a transistor blocking oscillator for the production of the ionizing peak voltage or pulses 2, other solid state devices may be employed for the purpose of the invention, such as uni-junction transistor oscillator, silicon controlled rectifier chopper circuits and the like including a suitable peaking reactance to result in a series of discrete ionizing voltage pulses of the type used by the invention.

In operation, closing of the switch 20 will result in the control voltage pulses p being applied to the electrode 13, whereby to ionize the tube and to initiate the discharge current which may be limited by the load resistor 12 to prevent damage to the tube, unless the switch 20 is opened after a brief period, as in the case of the circuit breaker operation in accordance with the invention being described presently.

The ionization of the tube 10 by the pulse voltage p is believed to be due to the large number of higher harmonics of said voltage, whereby to cause ionization of the gas molecules by high frequency, while the discrete nature of the pulses p enables both an ON and OFF control of the ionic discharge current, provided the main breakdown voltage is a sufiiciently low fraction of the operating voltage of the source 11 and the amplitudes of the pulses are sufficiently above the critical control voltage e,,, as shown in FIG. 2.

FIG. 2 shows the characteristic curve of the gaseous suppressor tube, representing discharge current i as a function of the control Voltage e applied to the auxiliary electrode. The peak voltage pulses 2 used for the control according to the invention, which may have a spacing distance of the order of the pulse width, substantially exceed the critical control or ionizing voltage e whereby, by using pulses having a sufiiciently high repetition frequency, an efficient ON and OFF control of the ionic current through the tube may be effected within the brief or intermittent operating periods required for the arcless operation of an electrical switch or circuit breaker, as described in further detail in the following in reference to FIGS. 3 to 6 of the drawing.

Referring to FIG. 3, the circuit or network to be controlled is shown to include a generator or source 21, either AC. or DC, providing an operating voltage of say 380 volts and supplying a load current of say a maximum of 500 amperes, by way of example, to a consumer, or a number of consuming or load devices, as the case may be. The circuit breaker for the closing and interruption of the load circuit is schematically represented by the contacts 23 and 24 shown in the closed position and including control mechanism for the operation of said contacts from closed to open position, and vice versa, during a predetermined relatively short operating or interrupting period. There is shown for this purpose a control lever 25 carrying a rotating cam or disk 26 or the like control member and being operatively connected in a known manner with the contacts 23 and 24 through suitable actuating or operating mechanism indicated schematically by the dot-dash line 27 in the drawing.

Permanently connected across the circuit breaker contacts 23 and 24 is a gaseous discharge or ionic suppressor tube 28 filled with a rarified gas under suitable pressure, such as neon, xenon, argon or the like, or a mixture of such gases, and being fitted with a capacitative ionizing or control electrode 30 shown in the form of a metal coating applied to the outside surface of the glass envelope of the tube. The electrode 30 is connected to the output of the peak voltage generator 31 which may be of the type according to FIG. 1 or of any other suitable construction known in the art. The input leads of the generator 31 are connected to a pair of stationary sliding electrodes 32 and 33 arranged to cooperate with the control disk or cam 26 for the connection and disconnection of the generator 31 in synchronism with the operation of the circuit breaker. Disk 26, in the example shown, is provided for this purpose with a projection 34 adapted to intermittently engage the contact 33, While the contact 32 is in continuous sliding contact with the periphery of said disk.

In operation, as the control lever 25 is rotated in clockwise direction for the opening of the electrical circuit, the peak voltage p is first applied to the control electrode 30, upon engagement of the contact 33 with the projection 34, while the circuit breaker contacts 23 and 24 are still in closed position, thus instantly reducing the impedance of the tube 28 from practically infinity to a very low value, FIG. 4, whereupon by continued rotation of the lever 25 the contacts will become initially separated while the contact 32 still engages the projection 34, FIG. 5. In other words, the circuit breaker contacts are opened while the full load of the circuit is allowed to pass through the shunt or by-pass provided by the suppressor tube 28, thus substantially preventing any discharge spark or arc formation between the contacts during the opening operation. After the contacts 23 and 24 reach the fully open or end position, FIG. 6, the contact 33 will be disengaged from the projection 34, whereby to remove the ionizing voltage p and to reduce the conducting or ON time of the tube 28 to an absolute minimum such as to enable the tube to carry the maximum intermittent load current during the circuit breaker operation. During the return movement of the lever 25 or closing of the circuit, the operation will be in the reverse direction by first closing the circuit through the tube 28 and thereafter through the contacts 23 and 24, whereupon the tube will be returned to its non-conducting or OFF state, in a manner readily understood.

According to an improved feature of the invention, an R-C parallel circuit is connected in series with the suppressor tube or by-pass circuit, as shown at 28' and 30' in FIG. 3. This circuit, being of special advantage in the case of a highly inductive load 22 of the generator 21, serves to store and dissipate any residual inductive energy released at the instant of separation of the contacts 23 and 24. More particularly, at the instant of ionization of the tube 28, FIG. 4, the load current pases in part through the tube 30 and in part through the still closed contacts 23 and 24. If the latter are then initially separated, FIG. 5, the inductive voltage charges the capacitor 30' of the R-C network, whereupon in the fully open position of the circuit breaker, or OFF position of the tube 28, FIG. 6, the stored energy of the capacitor is allowed to be dissipated gradually through the parallel resistor 28.

There is thus provided by the invention a simple and efiicient system for the suppression of the interrupting arc in a high power circuit breaker by substantially instantly by-passing the current to be interrupted through a specially designed gaseous discharge device normally exhibiting an extremely high impedance and capable of temporarily passing the considerable load current of the circuit being controlled. The suppression device is characterized by a simplicity of design and a minimum of size and bulk, whereby to render it suitable for the incorporation in existing circuit breaker structures or designs. The fact that the peak voltage generator used for the impedance control of the suppressor tube is called upon to draw power only during the relatively brief operating periods of the circuit breaker, further greatly enhances the economy and efiiciency of the suppression system.

In the foregoing, the invention has been described with reference to a specific illustrative device. It will be evident, however, that variations and modifications, as Well as the substitution of equivalent parts and elements for those shown herein for illustration, may be made without departing from the broader scope and spirit of the invention as set forth in the appended claims. The specification and drawing are accordingly to be regarded in an illustrating rather than in a restrictive sense.

I claim:

1. In arc suppression apparatus for high power electrical circuit breakers having a pair of contacts and operating mechanism therefor to operate the same from closed to fully open position during a predetermined relatively short operating period, a gaseous discharge device having a pair of main electrodes being permanently connected to said contacts, said device having a critical operating voltage below the operating voltage of the circuit in which said circuit breaker is connected, an auxiliary ionizing electrode of said device, a generator producing an ionizing voltage in the form of a series of peaked discrete high voltage pulses substantially exceeding the critical breakdown voltage of said auxiliary electrode, a rotary switch having cooperating stationary and rotating contact means, to connect and disconnect said generator, and means operably connecting said rotating contact means with said mechanism, to apply said ionizing voltage to said control electrode immediately prior to the beginning of a circuit breaker operating period and to remove said ionizing voltage from said control electrode immediately after the end of said operating period.

2. In arc suppression apparatus as claimed in claim 1, said peak voltage generator being comprised of a selfrunning blocking oscillator including peaking reactance means to produce a series of discrete output voltage peaks of a frequency proportional to the oscillating frequency.

3. In arc suppression apparatus as claimed in claim 1, the repetition frequency of said high voltage pulses being of the order of from 3000 to 5000 pulses per second.

4. In arc suppression apparatus as claimed in claim 1, including an R-C parallel network connected in series with said device.

References Cited by the Examiner UNITED STATES PATENTS 1,681,196 8/1928 Rudenberg 31711.1 1,690,524 11/1928 Berthold 327--11.1 1,902,958 3/1933 Jackson.

2,557,739 6/ 1951 Goldstein et al.

2,619,524 11/1952 Van Dorstein 317-11.1

MILTON O. HIRSHFIELD, Primary Examiner.

SAMUEL BERNSTEIN, Examiner.

R. V. LUPO, Assistant Examiner.

Claims (1)

1. IN ARC SUPPRESION APPARATUS FOR HIGH POWER ELECTRICAL CIRCUIT BREAKERS HAVING A PAIR OF CONTACTS AND OPERATING MEACHANISM THEREFOR TO OPERATE THE SAME FOR CLOSED TO FULLY OPEN POSITION DURING A PREDETERMINED RELATIVELY SHORT OPERATING PERIOD, A GASEOUS DISCHARGE DEVICE HAVING A PAIR OF MAIN ELECTRODES BEING PERMANENTLY CONNECTED TO SAID CONTACTS, SAID DEVICE HAVING A CRITICAL OPERATING VOLTAGE BELOW THE OPERATING VOLTAGE OF THE CIRCUIT IN WHICH SAID CIRCUIT BREAKER IS CONNECTED, AN AUXILIARY IONIZING ELECTRODE OF SAID DEVICE, A GENERATOR PRODUCING AN IONIZING VOLTAGE IN THE FORM OF A SERIES OF PEAKED DISCRETE HIGH VOLTAGE PULSES SUBSTANTIALLY EXCEEDING THE CRITICAL BREAK-

Images