US2694787A - Starting circuit for electric lamps - Google Patents

Description

Nov. 16, 1954 E. LEMMERS 2,594,787

STARTING CIRCUIT FOR ELECTRIC LAMPS Original Filed Oct. 26, 1948 4 Shets-Sheet l 36 f7 A/WEJ lrwven t'or: Egggne Lemmer's, b3 Mo K His ALiorneg.

Nov. 16, 1 E. LEMMERS 2,694,737

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Eugene Lemmrs, b8 M C- K Hi5 A=lr=torne9 United States Patent 2,694,787 Patented, Nov. 16,. 19.54

Eugene Lemmers, Cleveland Heights, Ohio, assignor to General Electric Company, a corporation ofNfcw York Original application October 26,. 1948, Serial No. 56,615, now Patent No. 2,673,?42, dated li'l arch 30, 1954. Divided and this application February 4, 1950, Serial No. 142,457

7 Claims. (Cl'. 315-98) My invention relates to starting and operating circuits for electric discharge devices, and more particularly to starting and operating circuits for low pressure mercury vapor discharge devices, such as fluorescent lamps. This application is a division of my pending application No. 56,615, filed October 26, 1948*, and assigned to the same assignee as the present invention, now U. S. Patent No. 2,673,942, issued, March 30-, 19-54.

The aforementioned parent application discloses my discovery that, with fluorescent lamps employing krypton and xenon as the starting gas, totally unexpected advantages ensue from the application of an auxiliary potential, different from that applied to either electrode, to a starting stripe external to the lamp. The claims presented therein are to combinations of krypton or xenon filled lamps with means for utilizing the restricted range of auxiliary potentials to the best advantage instarting such lamps.

The parent application also discloses various novel circuits for applying an auxiliary potential to astarting stripe or electrode. These circuits have in common the feature of utilizing dissimilar phase voltages, applied to the electrodes of a pair of lamps, as auxiliary starting potentials for the other lamp of the pair. In a preferred embodiment, this feature is brought about by means of a novel crossover connection. These novel circuits may be used with other types ofelectric discharge devices besides the krypton or xenon filled lamps with which the parent application is particularly concerned, and they are claimed in the present divisional application.

Generally speaking, according to the prior art arrangements for starting and operating low pressure electric discharge devices, such as fluorescent lamps, employing mercury vapor at a relatively low pressure ranging from several microns of mercury to 10 to 30- microns of mercury, and employing a starting gas, it has been. conventional to use the preheating type starting circuit and method, or to employ the instant starting type circuit wherein a substantially greater voltage is. impressed across the electrodesof the lamp in order to render-the lamp conducting immediately upon energization of the circuit.

In co-pending patent application Serial No. 731,488, filed- February 28, 1947, now U. S. Patent 2,504,549, Lemmers et al., there is disclosed and claimed a starting and operating circuit for electric discharge devices, such as low pressure mercury vapor fluorescent lamps, where inpreheating and instant starting operations are accomplished, obtaining the results and benefits: of both the instant-start and preheating methods without incurring any material disadvantage. The above-identified application is assigned to the assignee of this application.

Where krypton and xenon, or mixturesthereof, are employed as the filling or starting gas in a low pressure mercury vapor discharge device, it has been found that in many instances the previously available starting circuits are not adequate to provide the requirements of the improved type of fluorescent lamp, it being indicated that larger starting voltages would be required as Well as ballasts Which operate at lower voltages after the are discharges are established. At any rate, it has become necessary to provide new and improved starting circuits for lamps employing krypton, xenon, or mixtures thereof and which do not involve voltages so high as to make general and widespread use undesirable.

An object of my invention is to provide new and improved circuits for starting and operating electric discharge devices, in which circuitsv there is afforded a distinct economy in construction over and above those provided by the prior art.

For further objects and advantages and for a better understanding of the invention, attention is now directed to the following description andaccompanying drawings. The features of the invention believed tobe novel will be more particularly pointed out in the appended claims.

Briefly stated, in accordance with the illustrated embodiments of my invention I provide new and improved starting circuits for low pressure mercury vapor fluorescent lamps which employ krypton, or xenon, or mixtures thereof either alone or with argon, and which also include an associated starting means which, may take the form of a conductive stripe adherent to the surface of the elongated envelope of the lamp. Preferably, this starting stripe may be positioned on the outside surface of the lamp envelope. It has been surprising to note in connection with the work which I have conducted that while throughouta certain range the voltage required to initiate an arc discharge between electrodes of such a lamp decreases as the voltage impressed onthe starting stripe is increased, there is a point reached beyond which it is inadvisable to further increase the starting stripe voltage. There are several reasons for this conclusion. From a strictly engineering point of view, there is a pointattained beyond which itisinadvisable to go because a further increase in starting stripe voltage does not reduce the lamp starting voltage. For example, I have found that irrespective of the lamp length it is inadvisable to increase the stripe voltage to a value greater than 30.0 volts, and it is entirely satisfactory to. maintain the starting stripe voltage within a range from about to 300 volts. Once this optimum range has been attained, very little if any additional lowering of lamp starting voltage is achieved by going beyond it, thus indicating the second reason for so limiting the starting stripe voltage. This second advantage relates to circuit economy, it being clear that there is no justification for additional expenditure in apparatus cost to provide equipment to supply higher voltages than required. Lastly, there is a decided advantage from the standpoint of eliminating personnel shock. hazard incident to the presence of very high, or unnecessarily high, starting stripe voltages. This factor would be. of extreme consequence if the stripe voltage were to beproportionately increased in value as a function of lamp length, as would occur if the voltage were merely'increased upon increase of the lamp. length.

It has been my observation that at about 150 volts applied to the starting stripe, irrespective of the lamp length, there is. very little. orno advantage obtainable in reduction of lamp starting volts, byfurther increase of the stripe voltage. As an example it is significant to note that this. approximate value obtains for'lamps 4 feet long and 8 feet long, and which employ krypton at pressures ranging from about 2 mm. to about 3.5 mm. of mercury.

In accordance with a still further feature of my invention I provide an improved circuit for energizing a pair oflow pressure mercury vapor fluorescent lamps through interconnected leading power factor and lagging power factor circuits and in which cross-over connections, or other means, are provided for impressing on a starting stripe or starting means associated with one of the electric lamps a voltage derived from the energizing circuit connected; to the other lamp. I have found that it is desirable to impress onsuchstarting means a potential not less than about 150 volts with reference to either of the electrodes-of a given lamp. Alternatively, additional winding means may be associated with or constitute a part of a transforming means such as an autotransformer, or separate transforming means may be; employed, to obtain the desired difference in potential impressed on the starting stripe with reference to that of either of the electrodes of a particular lamp.

For a better understanding of my invention reference may be had to the following description taken in connection with the accompanying drawings, and its scope will be pointed out in the appended claims. Fig. 1 diagrammatically illustrates an embodiment of my invention as applied toa circuit for energizing a pair of low pressure mercury vapor fluorescent lamps; and Figs. 2 and 3 repre- .Scnt operating characteristics, of the.- preheating-instant start type circuit disclosed and claimed 'in my co-pending joint patent applicationSerial No. 731,488. Figs. 4 and 5 represent the relationship between the voltage impressed on the starting stripe and the lamp starting voltage for fluorescent lamps employing krypton as the starting gas. Figs. 6 and 7 illustrate diagrammatically further arrangements in which the desired starting stripe voltage may be supplied to the lamps; and Figs. 8 and 9 are further modifications in which separate winding means, or separate transforming means, respectively, are applied to leading power factor and lagging power factor circuits for energizing a pair of fluorescent lamps. Fig. 10 is a still further modification of my invention wherein the starting stripes of a pair of fluorescent lamps are connected to a single winding means of an auto-transformer adapted to supply starting and operating voltages as well as stripe voltages.

Referring now to Fig. l of the accompanying drawings, my invention is there illustrated as applied to a system for starting and operating a pair of low pressure electric discharge devices, such as a pair of low pressure mercury vapor lamps 1, 1 of the fluorescent type. The lamps 1, 1' comprise elongated tubular or cylindrical envelopes 2, 2' having sealed into the ends thereof filamentary electrodes 3, 4 and 5, 6 respectively. Although my invention is not limited in its broader aspects to discharge devices employing filamentary or thermionic electrodes, for the purpose of illustrating my invention in connection with one type of preheating circuit, I have chosen to refer to that being disclosed and claimed in the joint co-pending patent application Serial No. 731,488, and accordingly the electrodes have been illustrated as of the filamentary or thermionic type. However, in view of the disclosure of the present application, it will be appreciated that electrodes of the cold type (activated or otherwise) may also be employed. Where the electrodes are of the filamentary type it is preferable to employ the coiled-coil type of construction wherein tungsten wire is activated, preferably with oxides of alkaline earth metals such as a mixture of barium and strontium oxides. The envelopes 2, 2 contain gaseous atmospheres, such as starting or filling gases comprising krypton or xenon, or mixtures thereof, at a pressure ranging from about 2 mm. to about 3.5 mm. of mercury, and also a quantity of mercury which, during operation of the lamps, is at a vapor pressure of the order of several microns to or microns, the preferable operating range under normal ambient temperature conditions being of the order of 10 microns. The fluorescent lamps 1, 1 are provided with a suitable fluorescent material or phosphor coating, preferably on the interior surfaces of the envelopes. This fluorescent coating upon excitation by ultraviolet radiation produced by an electric discharge between co-operating electrodes, transforms the shorter radiation due to the discharge into longer wave radiation such as radiation within the visible range. For ease of starting, I employ starting means 7, 7', of conductive material, and which extends along the axial length of the lamps 1, 1', and preferably terminates within the vicinities of the electrodes for that lamp. As shown in Fig. 6 described hereinafter, these starting means may comprise conductive or metallic stripes adherent to the elongated envelope, and preferably adherent to the outside surface of the envelope.

The lamps 1, 1 are connected to starting and operating circuits 9, 10 and 10', 11. These circuits supply starting and operating voltages to the lamps 1, 1' each starting voltage being substantially higher than the operating voltage. Preferably, these energizing, or starting and operating circuits, have different power factors, that is, one (9, 10) has a lagging power factor and the other (10, 11) has a leading power factor. Other terminals of the thermionic electrodes 3, 4 and 5, 6 are connected to terminals labeled: a, b, c, and d, to which may be connected a suitable circuit for supplying preheating current to the electrodes. The lamps connected to the circuits forming the lagging power factor load circuit 9, 10 and the leading power factor load circuit 10', 11, are connected across a suitable source of voltage, preferably a voltage step-up auto-transformer 12 having a pair of secondary winding means 13 and 14 serving also as ballasts for lamps 1, 1, respectively, and being loosely coupled to a source of current, such as a primary winding means 15 energized from an alternating current supply circuit 16. As may be gathered from the drawing, the secondary windings 13 and 14 are poled to augment the voltage applied across the primary winding 15, in opposite phases, so that maximum potential difference occurs across the outer ends of the secondary windings 13 and 14. The alternating current supply circuit 16 may be a volt, 60 cycle commercial source of current. A usual capacitor 17 is connected to the secondary winding means 14 to render circuit 10, 11, the leading power factor circuit, by introducing a phase correction or displacement with respect to the lagging power factor circuit 9, 10.

Where it is desired in the employment of my invention to provide preheating type circuits in which the energization of the filamentary or thermionic electrodes is substantially reduced, or reduced to zero, upon initiation of arc discharges within the electric lamps, I may employ a three voltage neutralizing circuit disclosed and claimed in the above-identified joint application Serial No. 731,488. This circuit is connected to terminals a-d inclusive and may briefly be described as follows.

I may employ tertiary coils or windings 18, 19, 20 and 21 on the core of the auto-transformer 12 and inductively coupled to the transformers primary wilnding means 15; coils or windings 22, 23, 24, and 25 on the core of the auto-transformer 12 are inductively coupled to the transformer secondary winding means 13; and coils or windings 26, 27, 28 and 29 on the core of the auto-transformer 12 are inductively coupled to the transformer secondary winding means 14. The filamentary electrodes, in this case, are each connected in series with windings inductively coupled to the primary winding means 15 of the auto-transformer 12, and secondary winding means 13 and 14. Thus, electrodes 3, 4, 5 and 6 are connected in series with inductively coupled autotransformer windings 22, 18 and 26; 23, 19 and 27; 24, 20 and 28; and 25, 21 and 29; respectively, and comprises the starting and electrode control or heating circuits 9, 30; 10, 31; 10, 32; and 11, 33, respectively. The coils or windings serving electrode 3 and electrode 5, for example, may be wound in the following manner: the windings 22 and 24 are wound over the secondary winding means 13 of the auto-transformer 12 in the opposite direction to that of the secondary winding means 13; the winding means 18 and 20 are wound over the primary winding means 15 of the auto-transformer 12 in the same direction as the auto-transformers primary winding means 15; and the winding means 26 and 28 for the above electrodes 3 and 5 are wound over the secondary winding means 14 of the auto-transformer 12 wound in the reverse direction to the secondary winding means 14. The secondary winding means 13 of the auto-transformer 12 however is wound in the reverse direction to the primary winding section means 15 and the secondary winding means 14 of the auto-transformer 12. A suitable manual control switch 34 may be connected in series with the primary winding means 15 of transformer 12.

In order to impress on the starting means 7, 7' of the lamps 1, 1' potentials not less than about volts with reference to that of either of the associated electrodes for each lamp, I provide cross-over means or cross-over connections 35 and 36 which are connected to starting means 7, 7, associated with lamps 1 and 1, respectively. These cross-over connections impress on the starting means for one lamp voltage derived from the starting and energizing circuit connected to the other lamp. It will be further noted that these connections include in series therewith current limiting resistances 8 and 8 which serve to reduce the amount of current which may be drawn therefrom in the event of accidental contact. In this manner the personnel shock hazard is further reduced. This current limiting feature in which resistances of predetermined large value are employed is disclosed and being claimed in co-pending patent application Serial No. 733,595, filed March 10, 1947, now U. S. Patent 2,512,280, Lemmers.

The above-described advantages in respect to the use of krypton, xenon, or mixtures thereof, concerning the relationship between the starting strip voltage and the lamp starting voltage applies to the use of the stated gases or combinations of gases either alone or with argon. I have found that where the starting gas composition comprises 50 per cent argon, and 50 per cent krypton. xenon, or mixtures thereof, that the characteristics of the latter-mentioned gases are given or imputed to the total starting gas composition, which characteristics are shown in the curves of Figs. 4 and 5. It appears that a small amountof-gases from the group consisting-of krypton, xenon, and mixtures thereof,-.such. as. from to .per cent .of the total starting gas compos1t1on, Wlll impart to the total starting'gas composition the 111115- trated tapered voltage relationshipsv as shown by the krypton curves in Figs. 4 and 5.

It should be observed thatthere is a very defin te advantage incident to the use of krypton, xenon or mixtures thereof, either alone or in combination withargon as contrasted with the use of pure argon :alone. 1 These advantages are definitely understood by reference to Figs. 4 and 5, it being clear that the reduction in lamp starting voltage in the case of argon 1s very much less than that incident and available in lamps employing krypton, xenon, or mixtures thereof. there is a very decided advantage 1n apparatus economy incident to the correlation of starting stripe voltage and lamp starting voltage inv lamps employing thelattermentioned group of gases.

' When switch 34'is closed, power is suppl ed to the auto-transformer 12, and its associated and mductively coupled windings are energized. Cathode heating current, sufiicient for raising the temperature .of .the,electrodes of each lamp to produce electron emission therefrom and to facilitate break-down of the discharge path .therebetween is supplied to. the lamps. lProper voltages for'starting arc discharges between associated electrodes of the different lamps are also provided and impressed across co-operating-electrodes. Simultaneously w1th the closing of the switch 34 there is impressed on each of the starting means 7 and 7 a voltage which is sufficiently high or great with respect to the voltages impressed on either of the electrodesv of the associated lamp to render the lamp conducting without necessitating the use of excessively high starting voltages between elec-.

trodes. As stated above, I have found that" there is an optimum range of starting stripe voltages lying between the values of about 150 volts and 300 volts which serves this purpose very effectively. A voltage dn'ference on the starting stripe not less than about 150 volts with reference to either of the electrodes has been found to be the value at which the effect of diminishing utility is encountered concerning the use of voltages for assisting or facilitating the initiation of arc d1scharges.

In other words, the electrode or lamp starting voltage is found to decrease at a disproportionately slow rate for starting stripe voltages in excess of the range from 150 to 300 volts .or even in excess of about l volts. This has been observed to be true irrespecnve of the lamp length. For example, by referring to Fig. 4 it will be noted that for a lamp 4 feet long the lamp starting voltage-stripe voltage curve begins to approach a horizontal or uniform value at about lSOor 169 volts 1n lamps employing krypton at. a pressure ranging from about 2 mm. to 3.5 mm. of. mercury. This feature 15 in decided contrast with the characteristic .of argonfilled lamps. Likewise, it has been found that a SllTlllar condition prevails in a corresponding lamp 8 feet long. This condition and the results of tests performed on such lamps are shown in Fig. 5. I

Referring now to the electrode heatmgcrrcurt shown in Fig. 1, and which is connected to terminals ad, 1nclusive, when the switch 34 is closed, preheatlng current of predetermined magnitude is transmltted to .the electrodes 3( inclusive. Before an arc drscharge occurs in either lamp 1 or 1, induced voltages =1n each 1nductively coupled winding of a particular electrode heating circuit, for example circuit 10, 31, is either .inphaseor 180 out of phase with the voltages of the otherinductively coupled windings of that heating CllCult. Fig. illustrates vectorially the phase relationsh p. and magmtudes of the induced voltages in the windings of heating circuit 10, 31, before an arc discharge is established. V19 represents the induced voltage of winding 19; V27 represents the induced voltage of winding 27; and V2: represents the induced voltage of wmding Thus, the resultant voltage VR is the voltage Wl'llCh 1S supplied to the heating circuit 10, 31 and which is impressed across the filamentary electrode 4 and is the voltage used for raising the electrode-temperature to facihtate breakdown of the arc discharge path in the lamp and forstarting an arc discharge between the electrodes.

After the arc discharge has been established the magnitudes of, and phase relationship among, the induced voltages .of the. heating circuit 10, .31 change. -.As.1nd1- In other words,

.eated in'I- fig.v 3,--.the resultant voltage VR- may bersubstantially reduced to a predetermined operating value by proper; prop'ortioriingtand phasingofathe threev induced voltages of thecontrol or heating circuit 16,31. Perfect neutralization is diflicult to obtain becauseofthe voltage drop caused in the lamp filamentary electrode by the phase and magnitude of .its-arccur-rent. The resultant voltage Va, however, is small enough'to be negligible. Perfect correlation betweenrthe voltages of the windings to obtain substantially zerouoperating voltage'during lamp conductionisnot necessary for the successful operation of the circuit. I To summarize, in view of the above it will be appreciated, that upon closing the switch. 34 immediately there is applied to.each lamp cathode heating current and a predetermined voltage is applied to the associated starting stripe or starting means. As soon as the electron emission of the electrodes reaches a predetermined value 'the applied-lamp voltage working in conjunction with the potential of the starting means renders the lamp conducting. Thereupon, due :to' the leakage reactance of the transformer 12, the starting voltage is reduced to a lower arc-maintaining voltage andthe cathode heating'circuits through the neutralizingaction thereof reduce the cathode or electrode current to substantially zero.

Another modification of my invention is illustrated in Fig. 6 wherein fluorescent lamps 37. and 38, having enclosing envelopes 39 and 40, are provided with electrodes such ,as filamentary electrodes 41, 42 and 43, 44, respectively. The lamps 3'7 and 38 are provided on the associated envelopes with adherent conductive metallic starting strips 45 and 46. A suitable high leakage reactanceauto-transformer 47 having primary winding means 48 and associated secondary winding means 49 and St) is provided in order to supply starting and operatingvoltages to lamps 37 and 38 through circuits 51, 52 and 53, 54-, respectively. A suitable capacitor 55 may be. connected in series'relation with'the primary winding means 48 and the secondary winding-rneans49 in order to establish phase displacement between the two circuits- 51, 52 and 53, 54 for energizing the lamps. Transformer 47 is energized from a source of alternating current 56. Similar to the arrangement shown in Fig. l, cross-over connections 57 and 58 for impressingsuitable potentials on the starting stripes 45 and 46 of;lamps .37 and 38, respectively, are employed to impress thereon potential differences not-less :than about volts with respect to either of the electrodes of a given lamp. Current limiting resistances 59 and as may be connected in the above-stated manner to reduce or completely eliminate personnel shock hazard.

' Electrode or vcathode preheat circuits or cathode energizing circuits may beconnected to terminals a, b, and c, d, for the lampsin the manner explained above in connection With the circuit of Fig. 1. For example, the same type circuit may be employed if it is desired, although it will be appreciated that my instant invention is not limited to the use of a particular type preheating circuit.

Fig. 7 is a further modification of my invention, and is quite similar to the circuit shown in Fig. 6 and corresponding elements have been assigned like reference numerals. In the arrangement shown in Fig. 7, the starting means need not be an'integral part of the lamps and may comprise starting means 6l'and 62 constituted by metal lic housings or reflectors of lamp fixtures extending axially-the length of. the lamps. in addition, I may provide separate-inductances 63 and 64 which are connected in series relation with conductors 51 and 53, respectively, where additional or separate current controlling means is deemed desirablefor-larnp operation and ballasting.

in'the modification of the invention shown in Fig. 8 7. provide transforming means 65 having primary winding -means 66 connected to a suitable source of alternating current. 67. The transforming means .65 may be of the auto-transformer type having a pair of secondary winding means 68 and 69 which supply starting and op erating voltages to lamps 3'7 and 38 through circuits '70, '71 and 71, '72,. respectively. .in addition to the secondary winding means I provide-tertiary winding means '73 and 74 which impress on the starting means 61 and .62 voltages different than that existing on either of theassociated electrodes-of a lamp by value notv less than about 150 volts. These separate startingst-ripe voltages are connected; through .eurrentalimiting resistances '59 and 60.

In Fig. 9 there is illustrated diagrammatically a still further modification of my invention wherein lamps and 76 having electrodes 77, 78 and 79, 80, and starting means 81 and 82 are energized through an auto-transforming means generally similar in function and arrangement to that shown in the circuit of Fig. 1. The autotransforming means 83 comprises a primary winding means 84 and secondary winding means 85 and 86 which supply starting and operating voltage to lamps 75 and 76 through circuits 87, 88 and 88, 89, the latter circuit having in series therewith a capacitor 90 to provide phase displacement to prevent a stroboscopic effect of the light emitted by the two lamps. The transforming means 83 is provided with tertiary winding means comprising windings 90-95 inclusive, windings 90, 92 and 94 connected to energize only one of the electrodes of lamp 75, such as electrode 77; and windings 91, 93 and 95 being connected to energize only one electrode of lamp 76 such as electrode 80. A similar set of windings, of course, may be provided for each of electrodes 78 and 79, if desired. In series relation with each of the set of three tertiary windings I provide separate transforming means 96 and 97 which serve to impress on the starting means 81 and 82 voltages sufficiently above that impressed on either of the associated electrodes of a given lamp. For example, transformer 96 has a primary winding 98 connected in series relation with tertiary windings 90, 92 and 94 and is connected to terminal a, the secondary winding 99 of this transformer being connected to the starting means 81 through current-limiting resistance 99'. Transformer 97 is connected in a similar manner with respect to lamp 76.

A further modification of my invention is illustrated in Fig. 10 wherein fluorescent lamps 100 and 101 having electrodes 102, 103 and 104, 105 are enclosed within elongated envelopes 106 and 107 respectively, and wherein starting means 108 and 109 extend axially and terminate within the vicinities of the electrodes of the associated lamp. These starting means may be metallic stripes adherent to the external surfaces of the envelopes, or may comprise conductive members of a fixture, or other element, extending along the axial dimension of the lamp in order to provide the desired starting function.

Transforming means 110 including primary winding means 111, and secondary winding means 112 and 113, serve as energizing sources for a pair of energizing circuits 114, 115 and 115, 116, for electric lamps 106 and 107, respectively. The latter mentioned circuit is pro vided with a serially connected capacitance 117 to provide a phase displacement between the voltages impressed on the electrodes of the two lamps. A single tertiary winding 118 is employed and may comprise a part of the transforming means 110 to impress on the starting means 108 and 109 a voltage to assist in establishing arc discharges within the lamps. sistances 119, and 120 having a common juncture are connected to the starting means 108 and 109, respectively. The voltage provided by the tertiary winding means 118 is of sufficient value so that the voltage impressed on the starting means 108 and 109 is at least about volts greater than the voltage impressed on either one of the electrodes of a particular lamp. T ransforming means 110 may be energized from a suitable source of alternating current 121 through a starting switch 122. Secondary winding means 112 and 113 are loosely coupled with the primary winding means 111 so that these windings serve as ballasts for the respective connected lamps. Of course, the transforming means 110 is also designed by virtue of its leakage reactance to provide a lower voltage than the starting voltage after the lamps conduct current. Furthermore, suitable preheating circuits may be connected to the terminals labeled (H1 in order to preheat the electrodes 102105, which operation may be accomplished in the manner explained above in connection with the circuit of Fig. 1.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In combination, a pair of gaseous electric discharge devices of the type characterized by a pair of spaced main electrodes and an auxiliary starting electrode, and starting and operating apparatus therefor comprising a common alternating current energizing means, a leading and a lagging power factor operating circuit coupled to said common energizing means and connected across respective devices, and cross-over connections connecting the Current limiting reauxiliary electrode of one device to one of the main electrodes of the other.

2. In combination, an alternating current supply, a pair of gaseous electric discharge devices each having an envelope, a pair of thermionic electrodes positioned therein, an ionizable medium and a starting electrode, and circuit means for energizing said devices comprising a leading power factor circuit connected across one device and a lagging power factor circuit connected across the other device, a common connection between one end of said circuits, a common energizing winding for said circuits connected to said supply, and cross-over connections impressing on the starting electrode of one of said devices a voltage derived from the circuit connected to the other.

3. In combination, a pair of gaseous electric discharge devices of the type characterized by a pair of spaced main electrodes within an elongated envelope, a capacitive starting member extending along the outside of said envelope, an alternating current supply, a main winding connected to said supply, a pair of secondary windings coupled to said main winding and connected to opposite sides thereof and poled to augment the voltage applied to the main winding in opposite phases, connections joining the outer ends of said secondary windings to one main electrode of each of said devices, a crossover connection between the other main electrode in each of said devices and the junction point of the main winding with the secondary winding connected to said one main electrode of the other device, and a connection between each of said outer ends and the starting member of the device connected to the other.

4. In combination, an alternating current supply, a pair of gaseous electric discharge devices each having an elongated envelope and a pair of spaced electrodes therein, an ionizable medium and an auxiliary starting electrode, and energizing means for said devices comprising a main winding connected to said supply and a pair of secondary windings coupled thereto and connected to opposite sides thereof and poled to augment the voltage applied to the main winding in opposite phases, connections between the outer ends of said secondary windings and one main electrode of each of said devices, a crossover connection from the other main electrode in each of said devices to the junction point of said main winding with the secondary winding whereof the outer end is connected to the other device, and a connection between said one main electrode in each device and the starting electrode of the other.

5. In combination, an alternating current supply, a pair of gaseous electric discharge lamps each having an envelope and a pair of spaced electrodes therein, an ionizable medium within said envelope and an auxiliary starting electrode, energizing means for said lamps comprising a main winding connected to said supply and a pair of secondary windings coupled thereto and connected to opposite sides thereof and poled to augment the voltage applied to the main winding in opposite phases, lagging and leading power factor connections respectively between the outer ends of said secondary windings and one main electrode of each of said lamps, a cross-over connection from the other main electrode in each of said lamps to the junction points of said main and the secondary winding whereof the outer end is connected to the other lamp, and a connection from said one main electrode of each lamp to the starting electrode of the other.

6. In combination, an alternating current supply, a pair of gaseous electric discharge devices each having an envelope and a pair of spaced electrodes therein, an ionizable medium within said envelope and an auxiliary starting electrode, and energizing means for said devices comprising a main winding connected to said supply and a pair of secondary windings loosely coupled to said main winding and connected to opposite sides thereof and poled to augment the voltage applied to the main winding in opposite phases, a direct connection between the outer end of one of said secondary windings and one main electrode of one of said devices, a capacitive connection between the outer end of the other of said secondary windings and one main electrode of the other of said devices, a cross-over connection from the other main electrode in each of said devices to the junction point of said main winding with the secondary winding whereof the outer end is connected to the other device, and

a connection from said one main electrode in each device to the starting electrode of the other.

7. In combination, an alternating current supply, a pair of gaseous electric discharge lamps each having an envelope and a pair of spaced thermionic electrodes therein, an ionizable medium within said envelope and an auxiliary starting electrode, and energizing means for said lamps comprising a main winding connected to said supply and a pair of secondary windings coupled to said main winding and connected to opposite sides thereof and poled to augment the voltage applied to the main winding in opposite phases, inductive and capacitive connections respectively between the outer ends of said secondary windings and one main electrode of each of said lamps, a cross-over connection from the other main electrode in each of said lamps to the junction point of said main winding with the secondary winding whereof the outer end is connected to the other lamp, tertiary windings coupled with said main and secondary windings and connected to said electrodes for heating them at starting with neutralization of heating during operation, and a connection between said one main electrode in each lamp and 5 the starting electrode of the other.

References Cited in the file of this patent UNITED STATES PATENTS 10 Number Name Date 1,977,231 Erickson Oct. 16, 1934 2,012,236 Beck Aug. 20, 1935 2,020,731 Lederer Nov. 12, 1935 2,252,189 Lederer Aug. 12, 1941 15 2,298,935 Freeman Oct. 13, 1942 2,314,311 Karash Mar. 16, 1943 2,424,324 Murcek July 22, 1947 2,504,549 Lemmers et al. Apr. 18, 1950

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