US2292034A - Arc ignition circuit - Google Patents

Description

w. E. BAHLS ARC IGNITION CIRCUIT Aug. 4, 1942;

Filed Ndv. 26, 1958 2 sheets-sheet 1 Lbad Control fbiential Control Potential WI'TNESSES: QINVENTOR 'WaZtErEBafiZS.

ATTORN Au 4, 1942. w. E. BAHLS 2,

ARC IGNITION CIRCUIT Filed Nov. 26. 193B 2 Sheets-Sheet 2 Load Fzj 3.

Load 7 Control Etc/dial Fig.4.

WITNESSES; LIQNVENTOR WaZfrEBa/vls. WWWM I "7%, ATTORN Y Patented Aug. 4, 1942 2,292,034 ARC IGNITION CIRCUIT Walter E. Bahls, Verona, N. J assignor to West= inghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application November 26, 1938, Serial No. 242,487

11 Claims.

My invention relates to electric discharge apparatus and has particular relation to ignition circuits for discharge devices of the immersedignition-electrode type.

A discharge device of the immersed-ignitionelectrode typecomprises, an anode of nickel, carbon or other suitable material, a mercurypool cathode and an ignition electrode of a high resistance material such as boron carbide or silicon carbide. To render the discharge device conductive, a current of substantial magnitude is transmitted between the ignition electrode and the mercury-pool cathode. For a device of moderate rating, the current transmitted may be of the order of 10 amperes. Since the resistance of the ignition electrode is relatively high, the potential required to transmit the current is substantial. For the 10 ampere ignition electrode, the power required is of the order of 2000 watts.

In view of the large magnitude of the power required in rendering a discharge device conductive, it isessential that the ignition current flow for as short a time as possible. If the starting current flows for a substantial interval of time, the ignition electrode becomes heated to a relatively high temperature and is seriously damaged.

In accordance with the teachings of the prior art, of which I am aware, the ignition electrode is connected to the anode of the discharge device through an auxiliary valve. To render the main device conductive, current is supplied through the auxiliary valve and the ignition electrode. As soon as the main arc strikes, the ignition current is interrupted, since the potential drop across the auxiliary valve and the ignition electrode is equal to the main arc drop and this potential is too small to maintain current flow through the auxiliary valve.

In many situations, it is inconvenient to use the above described prior art ignition circuit. In such cases, what may be designated as independent ignition is applied. An independent ignition circuit, as the name implies, is supplied from an independent source and the connection to the anode of th main device which makes possible the decrease in the ignition current is no longer available. In this case, it is, of course,

also important that the current fiowthrough the ignition electrode be discontinued as soon as it has performed its function.

' It is accordingly an object of my invention to provide an independent ignition circuit for a discharge device of the immersed-ignition-electrode operate with a minimum expenditure of energy for a discharge device of the type in which substantial current is required between the ignition electrode and one of the principal electrodes.

An ancillary object of my invention is to provide a novel oscillation generator of the type that supplies a saw-tooth wave form.

More concisely stated, it is an object of my invention to provide an independent ignition circuit that shall operate without causing damage to the ignition electrode or the other associated elements of an electric discharge device.

According to my invention, I provide an ignition circuit in which, by one means or another, the ignition current is quickly extinguished after it has performed its function. This may be accomplished by supplying the ignition current through an auxiliary valve and providing a second auxiliary valve which is rendered conductive in response to the flow of the main current, to short circuit the first auxiliary valve and the ignition electrode. The same object may also be accomplished by supplying the ignition current through an auxiliary valve and a capacitor in series. In this case, the capacitor may function to extinguish the auxiliary valve and interrupt the flow of current after a short time. same purpose, a charged capacitor may be quickly discharged and recharged through the ignition electrode and an auxiliary valve. In the above described ignition circuits, the flow of current need not persist for an interval of time longer than one or two microseconds, sinc it need fiow for only this interval to render the main valve conductive.

The novel features that I consider characteristic of my invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and its method of operation, together with additional objects and advantages thereof, will best be understood from the following description of specific embodiments when read in connection with the accompanying drawings, in which Figure l is a diagrammatic view showing an embodiment of my invention;

Fig. 2 is a diagrammatic view showing a modification of my invention;

Fig. 3 is a diagrammatic view showing another modification of my invention; and

For the Fig. 4 is a diagrammatic view showing a further modification of m invention.

The apparatus shown in Fig. 1 comprises a discharge device 5 of the immersed-ignition-electrode type having an anode I, a cathode 9 and an ignition electrode II which dips into the cathode. Anode-cathode potential is impressed on the discharge device from a source of alternating current I3 through a supply transformer I5 and when the discharge device is rendered conductive, current flows through whatever load I! is to be energized.

To render the discharge device 5 conductive, current of substantial magnitude is supplied between the ignition electrode II and the cathode 9. For this purpose, the ignition electrode and the cathode are connected in series with an auxiliary discharge device I9, a pair of resistance elements 2I and 23 and the secondary section 25 of an auxiliary transformer 21. The latter may be, as indicated, supplied from a source 29 independent of the main source I3. On the other hand, the secondary section 25 may be a section of the main transformer I5.

The auxiliary discharge device I9 is of the arelike discharge type having an anode 3 I, a cathode 33 and a control electrode 35 and a suitable gaseous or vaporous medium. To determine its operation a control device 31 of any well known type is provided. When the auxiliary device I9 is rendered conductive, current flows through it, the ignition electrode II and the cathode 9 of the main device 5, and the latter is rendered conductive. The current fiow through the ignition electrode II need only persist for an interval of time of the order of several micro-seconds to perform its function. After this, there is no longer any necessity to continue the current flow and to save power and prevent the ignition electrode from being damaged, the ignition current flow is interrupted.

For this purpose, a second auxiliary discharge device 39 is connected across the series circuit comprising one of the resistors 2|, the anode 3| and the cathode 33 of the first auxiliary discharge device I9, the ignition electrode I I and the cathode 9 and is thus supplied from the auxiliary secondary 25. The second auxiliary device 39, like the first device, is of arc-like type and comprises an anode 4|, a cathode 43, a control electrode I5, and a gaseous medium. It is rendered conductive in response to the fiow of load current through the main discharge device 5.

The change produced in the load circuit by current fiow through the load I! is transferred to the auxiliary device 39 through another auxiliary transformer 41. The primary 49 of the transformer is connected in series with the load I1 and the anode I and cathode 9 of the main device 5. The secondary 5| of the transformer 41 is connected across a resistor 53 through a rectifier 55 which may be of the dry coppercopper-oxide type. The terminal 51 of the resistor 53 which becomes positive when current flows through the rectifier 55 is connected to the control electrode 45 of the second auxiliary device 39. The other terminal 59 of the resistor is connected to the cathode of the second auxiliary device through a biasing source 6| which normally applies a negative potential between the control electrode 45 and the cathode 43 of the device to maintain it non-conductive. When current flows through the main discharge device 5, the auxiliary transformer 41 in its main circuit supplies unidirectional current through the resistor 53 and a potential is impressed between the control electrode 45 and the cathode 3 oi the auxiliary device 39 which is suflicient to counteract the effect of the biasing source CI and to render the auxiliary device conductive. Under the action of the potential drop through the ignition electrode II and the impedance II in series with the first auxiliary device I9, current now flows through the second device 39 and the potential across the first auxiliary device I9, its series impedance 2| and the ignition electrode II is reduced to the arc drop across the second device 39. The first device is therefore rendered non-conductive and the fiow of current through the ignition electrode is discontinued.

The second auxiliary device 39 now remains conductive as long as the anode-cathode potential impressed thereon is suflicient to maintain the are. When this potential becomes too small to maintain the discharge, the second device becomes non-conductive and the apparatus is reset for another operation if one is necessary or desirable. Where the main device 5 and the auxiliary devices I9 and 39 are supplied from the same source, or from sources of the same frequency, the second auxiliary device may be rendered non-conductive substantially at the same time or a short time before the main device is extinguished. After this, the three discharge devices remain non-conductive until the first auxiliary device I9 is again rendered conductive and as a consequence, the main device 5 isrendered conductive and causes the second auxiliary device 39 to become conductive and deenergize the first device.

In the apparatus shown in Fig. 2, the ignition current is supplied from the auxiliary secondary 25 through the series circuit including a capacitor 63, an auxiliary discharge device 55, the' ignition electrode I I and the cathode 9 of the main device 5. The auxiliary discharge device 65 is of the arc-like type comprising an anode 61, a cathode 69, and a control electrode II. A resistor 13 is connected in parallel with the capacitor 53 to discharge it when it has been charged. The magnitude of the resistor I3 is such that continuous current fiow through it and the auxiliary discharge device 65 is not suflicient to cause damage to the ignition electrode.

To ignite the main discharge device 5, the proper potential is supplied between the control electrode II and the cathode 69 of the auxiliary device 65 to render it conductive. Current then flows through the capacitor 63, the auxiliary device 65 and the ignition electrode II and the cathode 9 of the main device 5 and the capacitor becomes charged with the plate I5 connected to the anode 61 of the auxiliary device negative and the other plate 11 positive. The properties of the capacitor 63 and the auxiliary device 35 are such that the current flow is suflicient to render the main device 5 conductive. The relationship between the capacitor 53, the auxiliary device 65 and the ignition electrode II is such that the capacitor is thereafter quickly charged to a potential such that the auxiliary device 55 is quickly extinguished. After the latter event, the main device 5 continues to "carry current while no current flows through the ignition electrode II until the capacitor 03 has been suii'.l ciently discharged to permit reenergization of the auxiliary device 65. Preferably, the discharging resistor I3 is so dimensioned that this does not occur for substantially as whole period of the main source I3, since it is undesirable that current-be conducted through the ignition electrode H until such current is necessary and the ignition current flow is only necessary when the main device is again to be rendered conductive.

In the Fig. 3 modification, the ignition circuit also includes a capacitor 19 and an auxiliary discharge device 8| of the arc-like type having an anode 83,21 cathode 85 and a control electrode 87. In this case, one plate 89 of the capacitor 18 is connected to the terminal 9! of the main secondary section 93 of the supply transformer 95 to which the anode I of the main device 5 is connected through the load H. The other plate 91 of the capacitor I9 is connected to the ignition electrode ll through the anode 83 and the cathode 85 of the auxiliary discharge device fill. The capacitor is first charged with its lower plate 91 positive and its upper plate 89 negative from another secondary section 99 of the transformer 95 through the rectifier NH. The sections 93 and 9d of the transformer 95 are so wound that the charging of the capacitor l9 occurs during the half period during which the anode l oi the main device 5 is negative and the cathode is positive.

When the main device 5 is to be rendered conductive, suitable control potential is supplied to the auxiliary device 88 and the latter is rendered conductive when the potential of the secondary section 93 is of proper polarity. Current now flows. from the main winding 93 of the supply transformer 95 through the auxiliary device it and the ignition electrode 9! and the cathode 9 g of the main device to discharge the capacitor and recharge it to the opposite polarity. The current flow is suficient to render the main device conductive. Moreover it persists for only a short'interval of time, since by reason of the iact that the resistance in series with the capacitor is small, the latter soon charges to a potential tending to extinguish the auxiliary device iii. At the same time no current flows through the rectifier EM to charge the capacitor iii since the potential of secondary section iii-l is such that the rectifier Mi blocks current flow. When the potential supplied by the main secondary section 533 and the section 99 subsequently reverse in polarity current again flows through the rectiiier tilt to again discharge the capacitor J9 and recharge it to the first polarity. The latter operation need not take place at the same rate as the ignition operation, and, therefore, a resistor M13 is connectedin series with the rectifier. It is to be noted that if the resistor is of proper magnitude, the discharge and recharge of the capacitor 79 through the rectifier Mil may take place relatively slowly while the discharge and recharge through theauxiliary device 86 may take place quickly. The wave form produced by the charging and discharging of the capacitor is thus of the saw-tooth type.

The modification of my inven'ion shown in Hg. 4 is similar to that shown in Fig. 3 except that the auxiliary secondary section 99 of the main transformer is omitted. The capacitor 79 is in this case charged from the main section 93 of the supply transformer through the rectifier Ml. For this purpose, the lower plate iii of the capacitor is connected to the cathode terminal I05 of the secondary section 93 through the rectifier WI." The capacitor 119 is now charged during the half periods during which the. main anode-cathode potential is negative and discharged and. recharged to the opposite polarity during the positive anode-cathode periods of the source.

My invention has been shown herein as applied specifically to a discharge device of the immersed ignition electrode type. While it has peculiar advantages when used with a discharge device of this type, it may also be used with discharge devices in which the ignition electrode is spaced a short distance from the cathode and a make-alive are requiring substantial current is ignited. Where the essence of my invention is applied with discharge devices of this type, it is intended that the use shall fall within the scope thereof.

Although I have shown and described certain specific embodiments of my invention, I am fully aware that many modifications thereof are possible. My invention, therefore, is not to be restricted except insofar as is necessitated by the prior art and by the spirit of the appended claims.

I claim as my invention:

1. In combination, a main electric discharge device having a plurality of principal electrodes and an ignition electrode disposed adjacent one of said principal electrodes, current of substantial magnitude being required between said ignition electrode and said one principal electrode to render said device conductive, a current path for supplying ignition current between said ignition electrode and said one principal electrode and means. including an auxiliary electric discharge device connected to be rendered conductive in response to the conduction of current through said main electric discharge device, for interrupting current how in said current path.

2. In combination, a main electric discharge device of the immersed ignition electrode type having a plurality of principal electrodes and an ignition'electrode disposed in contact with one of said principal electrodes, current of substantial magnitude being required between said ignition electrode and said one principal electrode to render said device conductive, a current path for supplying ignition current between said ignition electrode and said one principal electrode, and means including an auxiliary electric discharge device connected to be rendered conductive in response to the conduction of current through said main device, for interrupting the current flow in said path.

3. In combination, a main electric discharge device having a plurality of principal electrodes and an ignition electrode disposed adjacent one of said principal electrodes, current of substantial magnitude being required between said ignition electrode and said one principal electrode to render said device conductive, a current path including a first auxiliary electric discharge device of the arc-like type, for supplying ignition current between said ignition electrode and said one principal electrode and means, including a second auxiliary electric discharge device connected to be rendered conductive in response to the conduction of current through said main electric discharge device, for interrupting current flow in said current path.

4. In combination, a main electric discharge device having a plurality of principal electrodes and an ignition electrode disposed adjacent one of said principal electrodes, current of substantial magnitude being required between said ignition electrode and said one principal electrode to render said device conductive, a current path including a first auxiliary electric discharge device of the arc-like type, impedance means and means for causing current to flow through said first device and said impedance means in series for supplying ignition current between said ignition electrode and said one principal electrode and means, including a second auxiliary electric discharge device of the arc-like type in parallel with said first device and said impedance means, connected to be rendered conductive in response to conduction of current through said main electric discharge device, for interrupting current flow in said current path.

5. In combination, a main electric discharge device of the immersed ignition electrode type having a plurality of principal electrodes, and an ignition electrode disposed in contact with one of said principal electrodes, current of substantial magnitude being required between said ignition electrode and said one principal electrode to render said device conductive, a current path for supplying ignition current between said ignition electrode and said one principal electrode, including the series circuit consisting of a source of current, impedance means. a first, auxiliary discharge device of the arc-like type, said ignition electrode and said one principal electrode, and means including a second auxiliary electric discharge device of the arc-like type in parallel with said first device, said impedance means, said ignition electrode and said one principal electrode connected to be rendered conductive in response to the conduction of current through said main device, for interrupting the current flow in said path.

6. In combination, a main electric discharge device having a plurality of principal electrodes and an ignition electrode disposed adjacent to one of said principal electrodes, current of substantial magnitude being required between said ignition electrode and said one principal electrode to render said device conductive, a current path for supplying ignition current between said ignition electrode and said one principal electrode, said path comprising a capacitor, an auxiliary electric discharge device of the arc-like type connected in series with said ignition electrode and said one principal electrode and a source of alternating current for charging said capacitor through said series connected elements, means for rendering said auxiliary device conductive so that said capacitor is charged, and means for discharging said capacitor, said capacitor being of such magnitude that when said auxiliary device is rendered conductive, it is charged sufllciently to render said auxiliary device non-conductive in an interval oi time that is short compared to a half period of said source and said discharging means being such that said capacitor is discharged sufliciently so that said auxiliary device may be again rendered conductive during substantially a period of said source.

7. In combination, an electric discharge device having a plurality of principal electrodes and an ignition electrode disposed adjacent to one oi! said principal electrodes, current 01 substantial magnitude being required between said ignition electrode and said one principal electrode to render said device conductive, a capacitor, means for charging said capacitor to one polarity and a current path for supplying ignition current between said control electrode and said one principal electrode including a source of potential having one terminal connected to said one principal electrode and the other terminal to one plate of said capacitor, and means for discharging said capacitor and recharging it to the opposite polarity, said discharging and recharging means including means for connecting the other plate of said capacitor to said ignition electrode.

8. In combination, an electric discharge device having a plurality of principal electrodes and an ignition electrode disposed adjacent to one oi said principal electrodes, current of substantial magnitude being required between said ignition electrode and said one principal electrode to render said device conductive, a capacitor, means, including a first source of potential, for charging said capacitor to one polarity, a current path including a second source of potential for supplying ignition current between said control electrode and said one principal electrode, said second source having one terminal connected to said one principal electrode and the other terminal to one plate of said capacitor, and means for discharging said capacitor and recharging it to the opposite polarity, said discharging and recharging means including means for connecting the other plate of said capacitor to said ignition electrode.

9. In combination, a capacitor, means including a first source of potential for charging said capacitor to one polarity, a work circuit including said capacitor, a second source of potential in said circuit, and a discharge device of the arc-like type for controlling the flow of current through said circuit, said device and second source being effective to discharge said capacitor through said circuit and recharge it to the opposite polarity.

10. In combination, a capacitor, means including a source of direct current potential for charging said capacitor to one polarity, a work circuit including said capacitor, a source of alternating current potential in said circuit, and a discharge device of the arc-like type in said circuit for controlling the flow of current therethrough, said device and alternating current potential source being effective to discharge said capacitor through said circuit and recharge it to the opposite polarity.

11. In combination, a capacitor, means including a source of direct current potential for charging said capacitor to one polarity, a work circuit including said capacitor, a source of alternating current potential in said circuit, and a discharge device of the arc-like asymmetric type in said circuit and having its anode connected to the plate of said capacitor that is charged positive, said device and alternating current source of potential being effective to discharge said capacitor through said circuit and recharge it to the opposite polarity.

' WALTER E. BAHLS.

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