US2177883A - Electric discharge apparatus - Google Patents

Description

0er- 31, 1939. T. E. FOULKE `2,177,883

' ELECTRIC DISCHARGE APPARATUS Filed Sept. l, 1938 ed E. Fo uLke Patented oct. 31,1939

1 futur-sn,A STATES 1 PATENT orrlcI-:v' j

' d varl-Lluis.l Y i A TedE. Foulke, utley, N. '1., assignor.- by mesne assignmenta'to General Electric Company, a

corporation of New York Application september 1, 193s, :serial No. 228,049

, 4 Claims. The present invention relates to electric gaseous discharge devices generally and in particular todevices having starting means of the resonance type. A particular object of the invention is to provide a novel means for throwing a resonance or "semi-resonance starting circuit out of resonance .This circuit, which is disclosedin his pending of switches connected with the startingcircuit when the discharge device is inoperative forany reason. Still other objects and advantages of my invention will appear from ,the following detailed specification, o r from an inspection of the accompanying drawing.

The invention consists in the new and novel combination of elements hereinafter set forth and claimed.

kAn extremely desirable and effective starting and operating circuit for gaseous electric discharge devices of the full-wave rectifying type has recently been devised by Harold W. Lord.

` application. Serial No. 197,357, flied March 22, 1938, provides means of the semi-resonancetype to raise one of the anodes to a much higher-potential than the other anode above the cathode potential, whereby the discharge is initiated between the first of these anodes and the cathode.

The difference in Vanode potentials `which is thus produced results in a cross-current discharge between these anodes whichis availed of, where a time 'delay is desired to permit heating up ofthe cathode, to operate ya time delay mechanism of the thermostatic type. Switching means operated by-the main rectified discharge current is ordinarily provided to disconnect this high voltage from the one anode as soon as the discharge tothe cathoderis started. In some cases, as whereI the lead to the cathode' becomes acci'- dentally disconnected, or where the cathode has lbecome deactivated, so that the discharge to the cathode cannot start, this switching means obl cross currents produce undesired voltage surges- Also, f

every half cycle, as the current reverses. since .partial resonance exists during thisstart- `ing period the current drawn from the line is nently desirable. -such as a resistance which' is adapted to be shortv shunt in the anode 'discharge circuit.

two delay means is also preferably so coordinated vthat the'circuit' is deresonated, incase the main discharge is not earlier initiated, prior to -the the first closing thereof. Due to Ithis novel means materially greater Athan that reguired during normal operation of the lamp, and the heating of the various elements of the circuit is thus relatively high, so that vsome meansof reducingthe wattage input to the device if the main discharge 5 does n ot start within a reasonable time is emi- Where atime delay device,

circuited by .a thermostat, .ist included in the anode discharge circuit in orderto keep the cross-current discharge between the anodes down to .a very small value, and at. the same time to reduce the anode potential to a value insuflicient to 'initiate the main discharge untilthe cathode has had an opportunity to reach a desired elec- 15 tron emitting temperature, failure .ofthemain discharge to start at the desired time uponA short circuitlng of this resistance resu1ts.in the recur-A rent opening and closing Aof the thermostatic i l The le- 20 peated interruption of this shunt circuit pro' ciucesv unnecessary wear and tear onthe contacts of fthe-delay mechanism, and alsoproduces undesired voltage surges. Hence under these circumstances it is desirable to 'provide means to lo'ck out the delay mechanism in case the main discharge` does -not'start within a reasonable time.

I have Adiscovered that all of these' -desiied results are produced by the use ,fof Yan 'additional delay mechanism. which Lcompletes va circuit adapted-to deresonate the means by which'the high Apotential for the one anode is created,'this new circuit preferably providing its own holding circuit, whereby when onceclosed it will not reopen without' manual intervention. Where a, time delay mechanism is provided for the protection of the cathode this novel circuit 4also preferablyshort circuits or -otherwise locks out this delay mechanism to prevent repeated useless operations thereof, and the timing of the reopening ofthe shunt inthe anode circuit after for throwing the circuit out of itssemi-resonance condition, the 4total impedance' of `the lamp circuit is materially increased, and the line current is correspondingly dec'reased, with a resultant decreasein the heating of the various components 'of the circuit. Furthermore the wear and tear which would otherwise result from Vuseless intermittent openings lof the cross-current circuit ls entirely eliminated. g

For the purpose of illustrating my invention, u

l'IIS I have shown a schematic diagram of a preferred embodiment thereof in the accompanying drawlng.

As shown in this drawing the electric gaseous discharge device or lamp I comprises a tubular sealed envelope having an activated thermionic cathode 2 at one end thereof and two similar anodes 3 and 4, of carbon or the like, the latter being preferably separated by a baille 5. 'I'he lamp which has thus been schematically shown is conveniently of the type disclosed in my copending application, Serial No. 149,707, filed June 22, ,1937, wherein the lamp contains mercury vapor and a starting gas, such as argon, and .wherein the lamp envelope is coated with a fluorescent material. y

Before starting, such a lamp has a high resistance and ordinarily requires a voltage considerably higher than that of the circuit from which it is supplied to start a discharge therein. Thus a lamp that will operate with a drop of the order of 100 volts in the arc may require as much as 450 Volts between the cathode and an ano'de to .ionize the gas and initiate the arc discharge. The

auxiliary apparatus shown is especially designed to give this starting voltage and to ballast the discharge in an extremely eicient manner. The circuit shown is essentiallythat disclosed by Lord in his co-pending application, referred to hereinbefore, with the addition of a second delay element whose action is coordinated with the action of ,the original delay element in a novel manner.

In this circuit the lamp I is supplied from the source "I of single phase alternating current which for example may be a 60 cycle, 110 volt lighting circuit, through the unitary structure represented at Stand comprising .a combined high reactance transformer and smoothing reactor. The core of the structure comprises two E-shaped members 9 and I0 reversely arranged with respect to each other and with corresponding legs spaced from each other to form magnetic gaps. In the drawing these gaps are shown for simplicity as air ,gaps but as the apparatus is manufactured they comprise a suitable non-magnetic material against which the two members are clamped. Between the legs of the member I0 are magnetic shunts shown at I I thereby increasing the'ux leakage to provide a higher leakage reactance.

On each of the outer legs of the core structure is a primary winding consisting of the coil I2, a main secondary winding consisting of the coil I3 plus the coil I2 thereby constituting an autotransformer and a separate auxiliary secondary Winding comprising. the coils I4. The ends of the primary, thus-composed of the two cells I2,\are con; nected by the leads I5 and switch I6 with the opposite sides of the so'urce 'I. The opposite ends of the main secondary, composed of the two coils I2 and the two coils I3, connect with the two anodes 3 and 4, one directly and the other through a relay which will be described hereinafter, and

'the mid-'point lthereof connects with the cathode 2. The'latter connection includes the conductor I1 and the auxiliary secondary, made up of the two coils I4, the purpose of which is to supply heating current to the lamp cathode.

As shown by the vdrawing the magnetic shunts II are arranged adjacent the upper ends of the primary coils and extend between the outer legs of the core structure and the middle leg I8 thereof,

-said shunts being spaced from those legs by magnetic gaps which preferably comprise a suitable nonmagnetic material. It will be Seel) that by this arrangement the amount of leakage of the primary flux is greatly increased since the shunts provide a relatively low reluctance leakage path,

moreover, an exceptionally high reactance is obtained between the two halves or coils of the secondary winding because of the magnetic shunt effect thereof, whereby they are virtually isolated from each other.

A capacitor 24, which is used among other purposes to improve the power factor of the unit, is connected across the secondary of the transformer in series with a suitable reactance which not only prevents undesired harmonics but also avoids an undesired decrease in the angle of commutation. In the arrangement shown, which is identical with that of the aforementioned Lord application, this inductance is furnished by the reactor or choke coil 25 which has the intermediate tap 26 dividing it yinto the two parts 2l and 28, whereby it can function as an autotransformer. The portion 2l is connected in series With the capacitor 24 across the secondary of the main transformer. The relative amounts of capacitive inductance in the closed circuit including these members and the leakage reactance between the primary I2 and secondary I2 and I3 of the transformer is such that a condition of partial resonance is produced therein, with the natural resonance frequency of this circuit preferably slightly higher than the frequency of the supply circuit, as in the ratio of 65 to 60 cycles, for example. This semi-resonance condition results, of course, in a relatively large voltage drop across the coil 21, and in the production of a still higher voltage, by transformer action; across the entire coil 25, and also in an increased potential across the secondary of the main transformer.

The reactor 25 may have any desired core pro-4 vided it is not the same as the transformer core. It may, however, be of a form that constitutes an incomplete magnetic circuit in itself but, for pur- 'poses of economy, may be arranged adjacent to a part of the transformer core which part thereby serves to complete its magnetic circuit. Such a core construction is shown by the E-shape'd member 29 separated from the transformer core by magnetic gaps 3D.

Inasmuch as the voltage applied between the cathode and either anode, namely the voltage of one half of the secondary, even when augmented by the semi-resonant condition described, is insuiicient to initiate a discharge in the lamp, a special starting means Vis provided, wherein at starting the anode 4 is connected to the extended winding 28 of the coil 25, whereby a highv potential'difference, sufcient to initiate the discharge,

ls produced between the anode 4 and cathode 2.

This starting connection is provided by an electro-magnetic switch 32 which is normally biased against the contact 34 by the spring 35. This switch'is adapted to be moved away from the starting contact 34 and into engagement with the running contact 33 by the armature 36 attached thereto in response to a predetermined value of the uni-directional iiux passing the air gap 31 in the middle leg of the transformer core, this runenvases-- ning contacta vbeing directly to the opposite end of the transformer secondary from that connected to the 'anode 3.

Included in the circuitbetweenv the contact n and the .coil 28` is a novel time delay mechanismy ornprising three bimetallic blades 2l, I! and 4l,

o arranged' as to permit electrical contact between the free ends of adjacent pairs, and the 30 ohms. These elements are so connected lthat the heaters 4I and 42 are in series in the circuit from the contact 34 to the coil 28, with the heater 4 I nearer said contact I4. One end oi'- the heater 4I is connected to the blade 3l and the other end thereof is connected to the blade il, whereby this heater is short circuited by contact between the blades 38 and 39. It maybe noted that the blade 38 is merely used to compensate lfor changes in ambient temperature, and may be replaced by'. a fixed contact where such compensation is not required.` The end of the coil 42 which is more remote from the coil .201s also connected to the blade 39, while the blade 40 is connected directly i to. the same end of the transformer secondary which is connected to the anode l. Thus upon establishment of a contact between blades I! and 40 a by-pass including lthe coil 2l and heater 42 i isestablished across the condenser 24 which deresonates the starting circuit, and at the same time provides suilcient current in heater 42 to keep the blades 39 and 40 ,in contact.

When the switch I6 is rst closed to energize the lamp and the controlling apparatus therefor, a discharge does not immediately start, due to the-l inclusion of the high resistance of the heater 4I in the circuit tothe anode 4. Heating lof the cathode 2 by the secondary I4, howevexyis immer diately started. During the interval while' the cathode is heating up to the desired 'temperature cross currents pass between the anodes as, are: sult of the high voltage existing therebetween. These cross currents flow through the Aheater 4I,

' which limits them "to a small value, of the order oi' 20 mllliamperes, and the heater 42 in series. The heat produced by this small current v110W-- ing through the low resistance heater 42 is negli gible, and hence the blade 40 is substantially unailected thereby but this lsame current ilowing through the high resistance heater 4l produces enough heat to cause the associated blade l! to move upwardly into contact with the blade il,

after a predetermined'tlme interval o! the order of x 5' seconds has elapsed, this interval being made to `the free end of thetransformer secondary. Under this normal operation the switch $2 opens the circuit through the heater 4! before it 'has functioned.

In case the discharge does not start imme-` dlateiy, however, a is evident that after a definite time interval, determined by the thermal lag of.'

theblade n and heater u, the blade as wm move away from` the blade 38, reinserting the heater 4I in the circuit, tendingto cause a recurrence of this cycle of operation. This action of the blade i! isv undesirable, since once the heater 4I has Abeen short clrcuited the' cross currents invrcrease to the order of .9 ampere,V and the opening of this circuit bythe thermostatic blade ,39 is not only destructive of the contacts but also tends to produce undesired voltage surges in the inductive circuits. This action is, however, eliminated Awith my novel circuit. since '-the increased cross currents, of the order of .9 ampere, flow through the heater 42 and provide suiiicient heat to move .the blade 40 toward the blade 39, actual. contact being made, incase the main discharge is not earlier initiated, before the blade ,39 has cooled sumciently to open the shunt across the heater 4I. When the blades 38 and 40 are thus in contact the anodes 3- and 4. are short circuited and a circuit is'created from the end of the winding 28 through the heater 42, blade 39 and blade 40 to the end of the transformer secondary of opposite polarity. This connection throws the circuit entirely out of resonance, thus reducing not only the `voltage applied to the lamp I but also materially decreasing the wattage drawn from theenergy source II to a value of the order of one third of that drawn initially, with a corresponding reduction in the heating of the various coils. A current ofthe order of 0.4 ampere still ows through the V'heater 42, however, which is suiilcient to keep thevblades 39 and 40 in contact, especially vas the -blade 39 cools and moves toward the blade". Since the anodesl land 4 were short clrcuited by the simultaneous contact of the blades n, v39 and 40 thecross currents were eliminated, and hence the later opening ofthe contact between the blades 3! and 40 does not open a current carrying circuit and-hence is of no eil'ect and unobjectionable. 'Ihis setting of the various elements of the circuit then continues until the switch I6 is manually opened and the tube I replaced, or the cause of the diiiculty otherwise eliminated.

While so far I have discussed only the case of a lamp having cathodes of the type requiring preheating, it is to be understood that my invention is also applicable to devices using other types .of thermionlc cathode. Thus where no time delay is required to protect the cathode, the heater 4| may be permanently short circuited, or as an ployed. When such a cathode only requires a` single inlead it would of course be connected directly to the center tap of the windings I2.

Likewise, while I have shown the delay mechanisms asI being of the 'thermostatic type it is to be understood that various other types of time delay mechanism can be substituted therefor without invention. I-t is also to be understood that various other changes,l omissions and substitutions, within the scope of the appended claims, may also be made in the structure illustrated without departing from the spirit of my invention.

I claim as my invention:

1. In combination, an electric gaseous discharge device having at least two electrodes, a circuit connected with said device to create a high voltage between said electrodes by series resonance at a commercial frequency, switching means operative only after the elapse ofl a given time interval after energization of said circuit v to deresonate said circuit at said frequency, and means responsive to the discharge current through said device to render said switching means in,- operative upon initiation of a discharge between said electrodes.

2. In combination, an electric gaseous discharge device having a cathode and a pair of anodes, a transformer having its ends connected to said anodes and a midpoint connected to said cathode, the connection between one end of said transformer and its associated anode including means responsive to a commercial frequency to produce a high voltage by resonance which increases the potential difference between that anode and the cathode, switching means operative only after the elapse of a predetermined interval after energization of said transformer to deresonatesaid first mentioned means, and means responsive to the discharge current through said device to render said switching means inoperative upon initiation of a discharge between said cathode and anodes. A

3. In combination, an electric gaseous discharge device having a cathode and a pair of anodes, a transformerhaving its ends connected to said anodes and a midpointl connected to said` cathode, the connection between one end of said transformer and its associated anode includingl means responsive to a commercial frequency to produce a high voltage by resonance which increases the potential difference between that anode and the cathode, switching means responsive to the flow of cross' currents between ,said anodes to deresonate said first mentioned means after fiow thereof for a predetermined time in` terval, and means responsive to the discharge current through said device to render said switching means inoperative upon initiation of a discharge between said cathode and anodes.

' 4. In combination, an electric gaseous discharge device having a cathode and a pair of anodes,

a transformer havingits ends connected to said anodes and a midpoint connected to said cathode, the connection between one end of said transformer and its associated anode including means responsive to a commercial frequency to produce a high voltage by resonance which increases the potential difference between that -anode and the cathode and between said anodes,

whereby cross currents are caused to fiow between said anodes, a high resistance in the circuit traversed by'said cross currents, thermostatic means responsive to the heat Iproduced by the flow of said cross currents through said ,high resistance to short circuit said resistance after a predetermined time interval, switching means responsive to the iiow of said cross currents thereafter to short circuit said anodes and to deresonate said voltage producing means at a predetermined time after said thermostatic means has functioned and before. said thermostatic means opens the shortcircuit across saidresist ance, and means responsive to the ow of the maindischarge current through said device to render said switching means inoperative upon initiation of a discharge between said cathode and anodes.

TED E, FOULKE,

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