US2971124A

US2971124A - Apparatus for igniting and operating gaseous discharge devices

Info

Publication number: US2971124A
Application number: US847314A
Authority: US
Inventors: Albert E Feinberg; Berger Paul
Original assignee: Advance Transformer Co
Current assignee: Advance Transformer Co
Priority date: 1959-10-19
Filing date: 1959-10-19
Publication date: 1961-02-07
Anticipated expiration: 1978-02-07

Description

Feb 7 1961 A. E. FEINBERG r-:rAL 2,971,124

APPARATUS FOR IGNITING AND OPERATING GASEOUS DISCHARGE DEVICES Filed Oct. 19, 1959 2 Sheets-Sheet 2 1 *uid luffe s, 3Q,

l 'Hulwnnn 'F' CP Pl) lll mmm {www} il v (P2 l 52 43 @a L//Vf g-MQ?, ML, fda? United States Patent O F" APPARATUS FOR IGNITIN G AND OPERATING GASEOUS DISCHARGE DEVICES Albert E. Feinberg and Paul Berger, Chicago, Ill., assignors to Advance Transformer Co., Chicago, Ill., a corporation of Illinois Filed Oct. 19, 1959, Sex'. No. 847,314

23 Claims. (Cl. 315-97) This invention relates generally to apparatus whose purpose it is to cause ignition and operation of gaseous discharge devices and more particularly it is concerned with the construction of a ballast for such purposes and the system in which the ballast is adapted to be used.

The invention herein is directed primarily to the solution of several important problems which have arisen in recent years With the advent of fluorescent lamps of ,the so-called rapidstart type, which are designed to draw relatively higher currents than usual. Such lamps draw currents during operation of the order of 1.5 amperes and require a considerable number of turns of heavy Wire in the secondary winding of transformers used to ignite and operate same. For example, the characteristics of two relatively high-output, heavily-loaded lamps which are available at this time are:

Lamp 1 (Power Groove) 96 T-17 Ignition voltage volts 335 Operation voltage do-.. 175 Rated wattage watts-- 216 Rated current amparos 1.5 Diameter of lamp inches-- 2% Lamp 2 (V.H.O.) 96 T-IZ `Ignition voltage Y "volts" 335 Operation voltage do 175 Rated wattage watts-- 216 Rated current aniperes-- 1.5 Diameter of lamp inches-- 11/2 Two such lamps in series will operate at approximately 350 volts, and open circuit voltage for such an arrangement is about 525 volts.

Probably one important cause for the problems which have arisen is the necessity that the ballast be accommodated in a narrow cross-section housing, which means that the secondary winding serving the apparatus must be narrow and elongate. The narrow cross-section housing is usually a channel structure which comprises a part of a fixture for fluorescent lamps. Modern fixture design in general demands that the ballasts for fluorescent lamps be as narrow as possible, and in most cases, the maximum width permitted for the ballast is somewhat more than three inches. The proportions of the windings dictated by this requirement will be noted hereinafter..

In any event, the problems which have arisen have not heretofore been solved and these include the following:

a. The extreme length of the secondary means that since the coupling with the primary decreases with the distance from the primary, there is considerable loss of coupling so that a larger number of turns is required to achieve a given open circuit voltage. The increased number of turns increases costs, size, weight and heat. The result is that a compromise must be made, and in the past this has been achieved by operating the ballast at reduced output, with less turns than needed.

b. The extreme length of the secondary has resulted in 2,971,124 Patented Feb. 7, 1961 very high leakage reactance which distorts'the shape of the current wave and hence decreases lighting eflciency. In addition, the condenser which is in series with the ,lamps must be of higher voltage rating. Further, there .is diiculty in adjusting the leakage reactance in designing a ballast because the high value is not readily changed merely by making changes in the core structure, and in any event, these are expensive, especially in a leading type of circuit.

c. High leakage reactance gives rise to many less important diiculties, such as circuit instability, flux fringing, noise, etc.

The primary object of the invention is the provision of apparatus which will obviate the diculties, but which will result in a structure which is more economical and eificient than heretofore.

Specically, the invention achieves the following advantages:

(l) The coupling between the primary winding and secondary winding is increased, thereby decreasing the number of turns and the amount of wire used. This provides for full output with no compromise and with reduced heating.

(2) The leakage reactance is decreased, but, because of the construction, is readily adjustable over wide ranges which enables economical laminations and condensers to be used. Furthermore, the structure gives a high degree of flexibility to enable many designs to be readily achieved for a single kind of core structure for different types of lamps without expensive changes being made therein.

(3) The structure also provides for great flexibility in adjustability of coupling to enable stable and balanced arrangements to be readily made, without increasing leakage reactance.

(4) The advantageous structure can be operated at high flux densities in the primary Without danger of distortion of the current wave shape caused by saturation in the secondary.

The invention is characterized by the provision of a ballast which includes a transformer mounted on an elongate iron core which has a secondary winding in the center thereof and with a primary winding coaxially mounted relative to the secondary winding, but split into two parts, with each part located on opposite sides of the secondary winding. The central winding core has one or two bridged gaps or slots therein arranged in a fashion to adjust the coupling between the secondary and the respective primary parts and to adjust leakage reactance, and gapped shunts are provided between the secondary winding and at least one of the primary parts to produce proper balance and leakage reactance in the secondary. It may be said generally that the apparatus which is provided by the invention has good coupling character` istics between the primary and secondary and the proper leakage reactance to give good wave shape correction, increasing lighting etliciency, cutting down on the number of turns required, and with lower heat losses.

Many objects and advantages of the invention will occur to those skilled in this art as a description of the invention proceeds, in connection with which the preferred embodiments have been set forth in detail, for the most part comprising different circuit variations, but all being associated with the same or a similar construction of core. It is not to be inferred that the invention is specically directed to the construction and arrangement of these preferred embodiments, but rather it is to be understood that considerable variation is capable of being made without departing from the spirit of the invention.

In the drawings which are appended hereto:

Fig. l is a sectional View taken through a transformer which is constructed in accordance with the teachings of the invention and which is adapted to be incorporated into the apparatus of the invention. A fragment ofY the canister for holding the ballast is also illustrated.

'Figv 2 is a circuitdiagram illustrating the apparatusY relationship and a somewhat different arrangement offilament windings is shown.

Fig. 6 is a view similar to that of Fig. l but showing a modified form of core.

The rapid-start lamp, as known today, is a fluorescent lamp in which there are filaments secured in the ends of a glass envelope the walls of which are coated with phosphors and the lamp containing a minute quantity of gas at 1ow pressure with a few droplets of mercury. The lamp is connected into a circuit in which thellaments of the lamp are continuously supplied with a low current and hence the transformer which is used to provide the igniting and operating voltages must have filament windings. The general characteristics of the lamp are notmuch different than those of other gaseous discharge devices. The lamp starts at a voltage which is substantially higher than that at which it operates. Starting is accomplished by a break-down of the gas molecules in the envelope, caused by the ionization thereof. At open circuit the lamp presents substantially kinfinite impedance to the flow of current, but upon ignition, thisimpedance drops to practically zero. The transformer which provides power for the lamp hasssutiicient leakage reactance so that the ow of current is limited when the lamp commences to conduct.

The basic circuit used with rapid-start lamps usually includes a primary and secondary winding connected in autotransformer relationship across a pair of series-connected lamps, one of the lamps being shunted by a condenser. Upon open circuit, all of the output voltage is applied to the lamp which does not have the condenser because the condenser acts as a conductor insofar as voltage is concerned. lgnition of the tirst lamp causes flow of current through the condenser shunting the second lamp, and the flow of current develops a voltage across the shunting condenser sucient to ignite the second lamp. Thereafter current flows through both lamps in series, there usually being a power factor condenser inseries with the lamps to provide for a leadingv current.

As previously stated, in this invention, the primary winding is divided into two parts which are physically located on opposite sides of the secondary winding, to give rise to the benefits mentioned. One or more bridged gaps are provided in the central winding leg of the core, and suitable shunts are provided between the secondary winding and one or both of the primary parts. As in the case of the conventional ballast, the condensers, transformer, and suitable radio interference condensers and bleed resistors, the latter two types of elements not oeing shown, are enclosed in a suitable sheet metal canister and potted in a pitch compound, with the necessary leads extending through suitable openings in the canister. These are connected to the lamps and the line in accordance with specic diagrams normally carried upon the canister.

Fig. 2 illustrates a circuit diagram of the apparatus in` which the primary parts are parallel, this structure, being designated 10, and Fig. 3 illustrates a similar structure inwhich the primary parts are in series. The same transformer 12 is used kin both cases, although as will be4 explained, the transformer is subject to variation in its" construction.

In Fig. 1 the transformer 12 is shown to comprise a shell-type core which has an elongate central winding leg 14 which has a T-shaped configuration, the cross-bar of the T being the bridging end 16. The side legs 18 are parallel with and spaced from the central winding leg 14 to provide the elongate spaces on opposite sides of the central winding leg 14 which are occupied by the windings. pairs of windows, the center elongate window Ztl' accommodating the secondary winding S, and end

windows

22 and 24 for accommodating the primary parts P1 and P2 respectively, together with such of the filament windings F1, F2 and F3 as. may be located in close coupled relationship with the respective primary parts. Practically, the spaces between side legs 18 and the central winding leg 14 are continuous throughout their length, although the invention contemplates that the shunts which will be described may be formed as integral extensions, either from thc central winding leg 14 directed toward the side legs 18, or from the side legs l directed vtoward the central winding leg 14. Another structure would have portions integral with both the central winding leg 14 and the side legs 18.

The side legs 1S are both of elongate L conguration, With the short legs 26 extending toward one another at the right hand end of the core and abutting opposite edges of the end 28 of the central winding ieg 14 to form therewith a bridging portion opposite the end 1d. The ends 30 of the elongate portions of the side legs 18 abut the ends of the bridging end 16. Preferably the central winding leg 14 has twice the width of the side legs 18; In addition, it is preferred that the laminations from which the core of the transformer 12 is formed be stamped from a continuous strip of electrical or cold rolled steel, with substantially no waste. note the

pilot hole notches

32 and 32 and 34 and 34.

These notches would face one another in pairs if thetwo side legs 18 were shifted to the right and movedl close to the edges of the central winding leg 1d. This arrangement of nested parts provides a substantially rec` tangular configuration readily stamped with substantially no scrap from a strip of steel, either along the length of the strip or crosswise thereof.

The ends of the side legs 1S are notched, as at 36 to accommodate sheet metal end clamps of any suitable construction, for holding a stack of the laminations to gether in the arrangement shown. lf desired, the stacks of laminations may be riveted together by suitable eyelets or rivets, in addition to or instead of the end clamps. Likewise, it is within the purview of the invention to utilize the so-called forced core type of construction inV Y ponents making up the ballast.

Referring now to Figs. 2 and 3, in cach case there is a primary winding which is formed of a pair of parts P1 and P2 and in each case the left terminal 4Z of the.

primary part P1 is connected by the lead da which may be the white lead to one side of a line which may be.

volts, 60 cycles A.C. in the apparatus 1t?, the right hand terminal 46 of the primary part P1 is connected tu the left hand terminal of the secondary winding S and.

also to the lead i3 whichextends from the left hand terminal of the primary part P2.v This terminales extends by way-ofA the lead 5- whiclrmay be. a black lead, ,toi Note thatthe right hand,`

the second side of the line. terminalof the primary partizisconnected by the lead it may be considered that there are threev For exam-ple,-

52 with the lead 44 so that electrically the two primary parts P1 and P2 are in parallel, and the full line voltage is across both.

ln the apparatus 19, on the other hand, the right hand terminal of the primary part P1 is connected by means of the lead 48 only to the left hand terminal of the primary part P2, while the right hand terminal of the primary part P2 is connected by the lead 52 to the left hand terminal of the secondary winding S, and by way of the conductor 5@ to the right hand side of the line. Thus, the primary parts P1 and P2 of ap,- paratus are connected in series. Obviously, in both cases, each of the primary parts is connected in voltage aiding relationship with the secondary winding S, but only in the apparatus 10 are the primary parts P1 and P2 in voltage aiding relation to one another. In apparatus 10, since the primary parts P1 and P2 are in parallel with one another, the same voltage is applied across both, and the load voltage is the voltage of S added to the voltage across either of these parts. Primary parts P1 and P2 of apparatus 10 share the total line voltage across 44 and Sti so that in this case the load voltage is the voltage of S added to the voltages of both of the primary parts. In either case, the secondary winding S has a voltage greater than the total primary voltage and as such may be considered in voltage step-up relationship with the primary winding.

in all other respects, the two apparatuses are equivalent. Thus, each has the filament windings F1 and F2 closely coupled with the primary part P1 and the filament winding F3 closely coupled with the primary part P2. Filament windings F1 are connected by

leads

56 and 58 to the lett hand larnents 65B of the lamps L1. Filament wind.- ings F2 are connected by the leads 62 and 6ft to the conductors do and 63 respectively, which connect with filaments 76 and 72. The lilament windings F3 connect by the leads 74 and 76 to the filaments 78. The leads 76 each connect to a common terminal of the conductor 80 which extends from the right hand terminal of the secondary winding S in each case, through the series capacitor Cp to one side of the filament 78. The shunting lcondenser Cs in each case connects from the lead 68 to the same side of the filament 73 to which lead 80 is connected.

Small shunts

82 and 84 are shown in both apparatuses, but it is not intended that all structures will have both shunts. ln addition, a pair of slots or bridged gaps are shown in the central winding leg lei, one at and one at S2. The gap 8S is slightly to the right of the center of the transformer 5.2, and the gap do is shorter in width and located substantially closer to the primary part P1. Shunts 82 and 8.41 have

gaps

81 and 83.

The operation of the apparatus is not substantially different the conventional rapid start circuit, insofar as ignition and operation are concerned. The energization of the primary winding parts P1 and P2 results in small currents flowing in the iilament windings F1, F2 and F3 with heating of the lamp lilaments 6), '76, 72 and 7S. The voltage across the primary P1, P2 induces a voltage in the secondary winding S the value of which is approximately the turns ratio, reduced somewhat by the reduction of coupling from 100%. The voltage from the secondary winding S is combined with the voltage across the primary P1, P2 due to the auto-transformer arrangement, and the total voltage is more than sufficient to ignite lamp L1. rhereatter current iiows through the lamp L1, the by-pass branch including condenser Cs and the lead Sii. This low of current through Cs which has a high capacitive reactance produces a voltage drop across Cs which is sufcient to ignite lamp L2. As soon as lamp L2 ignites, its impedance is substantially lower than the reactance of the by-pass branch and hence practically all of the current iows through the lamps in series.

The total power factor of the circuit is controlled by the inductance and leakage reactance balanced against the capacitive reactance, the latter being primarily controlled by the condenser C11. in recent years the ratio of capacitive to inductive reactance in apparatus of this type has been increased from the former value of about two to one to higher values. In this apparatus, the ratio approaches three to one, which is still a leading circuit, giving rise to problems of wave shape distortion and the like, but providing economies in construction and operation.

n the case of the parallel circuit 10, the total number of turns of wire in each of the primary parts P1 and P2 is equal to twice the number' of turns of wire in each of the primary parts P1 and P2 of the series circuit fr0 because the total primary voltage is not divided between the parts as in the case of the series circuit. The current in each primary part of the circuit 10 is half of the current through the primary parts of the circuit .10 and hence the wire used may be much liner. As a matter of practicability, it was found that there was some advantage insofar as current carrying capacity in the parallel case. All of the above assumes the same secondary winding.

The

shunts

82 and 84 were formed of small strips of electrical sheet steel, about three or four in number, to give a total thickness of about .100 inch, shaped to t between windings. These pieces are of a width to provide total air gaps of approximately .040 inch at the shunts, their length being equal to that of the stack 0f laminations. An assemblage of these strips is shown in Fig. 4.

The division of the primary into its parts P1 and P2 and location at opposite ends of the secondary S gives more than suiiicient coupling between the windings, and thus the central slot 88 gives the control of leakage reactance and coupling which renders the structure advantageous.

It serves also to prevent saturation and corrects wave shape. The additional slot S6 decreases the coupling with the primary part P1 and thus increases the leakage reactance at the left end of S. While the exact nature of the theory of operation is not completely understood, it has been found that the arrangement shown, with the central gap 88 slightly oit center, and the gap S6 toward one of the primary parts, gives highly satisfactory results. Note that the gap 86 is shorter in transverse dimension. In certain cases gap 86 has been eliminated with good results, and also one or the other of the

shunts

82 and 84 may be eliminated.

The basic structure requires at least the center gap 88 which is of substantially greater length (along the length of the central winding leg 14) than usual for bridged gaps of the type heretofore used for Wave shape correction. This provides the advantages in combination with the split primary to give the goed coupling, proper leakage reactance and good wave shape correction.

The following examples of practical versions of the apparatus are for two Power Groove rapid-start lamps, of the rating set forth above. The configuration of the laminations is to scale, the overall length being 11.6 inches, the overall width being 3.05 inches. Other core dimensions are length of the windings P1 and P2 along the core-1.4 inches; length of the winding S-7.52 inches; width of side legs 18, end bridging portion 16, short arms 26-.515 inch; width of windows-.475 inch. The bridged gaps are both .190 inch in length, the gap 86 being .6 inch in transverse dimension and the gap 88 being .768 in transverse dimension. The center of the gap or slot S6 is 3.5 inches from the left hand end of the core, and the center of the gap SS is 5.5 inches from theA right hand end of the core. The shunts 84 were in each case made up of four pieces of .O25 thickness steel .430

by 1.5 inches in dimensions. inches to 1.5 inches.

The stack height was 1.25

P2 4370 turnsof21gauge wire-carrying lf-.4-amperes,

S 1560 turns of 181/2 gauge Wire carrying 2.8 amperes.

"Forapparatus iti', series primary parts:

P1 173 turns of 18 gauge wire carrying 2.8 amperes. P2 186 turns of 17 gauge wire carrying 2.8 amperes. S 1628 turns of 181/2 gauge wire carrying 2.8 amperes.

vOpen circuit voltage across the windings for both cases was 525 volts, so that the open circuit for S alone was 405 volts. The condensers used in the circuits were the same in both cases. The shunting condenser CS had a capacity of .075 microfarad and a voltage rating. of 575 volts R.M.S. The series condenser is 6.8 microfarads with a rating of 525 volts R.M.S. Usually the two condensers are mounted in the same container and have a common terminal.

The two primary parts P1 and P2 need not have the same number of turns, but in the case of the parallel circuit 10, there must be balance between these parts in order that both primary parts draw the same current to avoid localized heating and possible excessive magnetizing current in one or the other. Equal turns, and/or adjustment of the shunts enable this balance to be achieved.

Note that the turns ratio of secondary to primary turns is quite substantial, being approximately 5 to 1, and that the secondary winding S has a length greater than half the length of the entire core, the winding occupying the greater portion of the window space of the core.

In Fig. 5 there is illustrated another apparatus, identied by the reference character which differs from the apparatus of Fig. 2 in several respects. The primary parts P1 and P2 instead of being connected in auto-transformer relationship with the secondary winding S are together connected in straight voltage step-up transformer relatlonship therewith. The voltage across the primary winding P1, P2 in this circuit does not add to the open circuit or operating voltages of the secondary winding S. In certain instances this form of circuit may be desired. The primary parts are connected in series by way of lead 48 and the opposite terminal of primary. part P2 is connected by lead 52 to one side of the line, while the lead 44 of the primary part is connected to the other side of the line. The secondary winding S is thus connected directly across the series connected lamps by leads 58 and Sti.

`A modified arrangement of i'ilament windings is also illustrated in this case, to demonstrate that variations in this phase of the circuit are also possible. All three filament windings F1, F2 and F3 are coupled with the primary part P1 which may be ot physical character diiierent from that of winding P2 to enable this arrangement. Filament winding F1 uses lead S6 and common lead 58 to energize filament 60 and lament windings F2 and F3 are connected like those of Figs. 2 and 3.

But for the need for a somewhat higher turns ratio, and those diierences mentioned above, the structure is quite similar to that of Fig. 2. Modication of the primary winding connections to parallel primary parts is practically identical to the modification of Fig. 2 to Fig. 3, and hence it is believed not essential to illustrate this.

The transformer structure 12 illustrated in Fig. 6 is interchangeable with that of Fig. 1 insofar as basic construction and operation are concerned. Instead of being formed from three stacks of laminations held together by clamps or the like, this is a forced core type of structure. There is an outer rectangular frame having side legs 1% and end legs 1.6 and 26, formed of integral rectangular laminations held together by rivets or grommets as indicated. The central winding leg 14 is also formed of .a stack of laminations which are punched from the outer laminations during manufacture to assure close iit former 12, except thatassembly may be somewhat different. Here, the windingsare all assembled to the winding leg ifi in advance of assembly, by sliding the coils over the winding leg. For example, the right hand shunt 8d may be formed of inward extensions integral with the side legs iti meeting outward extensions integral with the central windingv leg id at gaps gli, so that the'winding P2 can be slipped onto central winding leg from its right hand end and will seat properly. The other windings are siipped on from the other end. Shunt S2 is shown here wholiy formed from integral extensions of the side iegs i5 stopping short of the central winding leg to form gaps 331.

incidentally, in all structuresv it was found that the length ot' gaps of shunts 32 and d' is not critical.

Note that in the transformer il the filament windings F1, F2 and F3 are all in the window 221i. Other arrangements are obviously feasible, such as tor example, having four filament windings, two closely coupled to each of the primary parts, respectively.

It is believed the invention has been sufficiently described to enable those skilled in this art to make and use the same, and it is pointed out that considerable variations can be made within the scope of the claims appended hereto, without sacrificing any of the features and advantages of the invention. Y

What it is desired to secure by Letters Patent of the United States is:

1. Apparatus for igniting and providing the operating voltages for at least one gaseous discharge device from a source of A.C. voltage insuiicient to ignite said gaseous discharge device, which comprises, an elongate iron core having an elongate winding leg and at least one parallel side leg forming therewith a plurality of windows, a transformer mounted on the coreV and having a primary winding formed of twov parts and a secondary winding, the secondary winding having a physical length greater than half the length of said winding leg and being mounted in one of said windows on said winding leg with the parts of said primary winding mounted in others of said windows coaxially with said secondary winding on said winding ieg and being located on opposite ends of said secondary winding, the primary winding adapted to be connected across said source and being in voltage step-up transformer relationship with the secondary winding, means including electrical leads for connecting said gaseous discharge device at least with said secondary winding to be subject to the voltages of said transformer, and a bridged gap in said core substantially at the center of said secondary winding and completely enclosed therein.

2. Apparatus as ciairned in claim 1 in which said primary parts are in parallel with one another.

3. Apparatus as claimed in claim 1 in which said primary parts are in series with one another.

4. Apparatus as claimed in claim 1 in which said electrical leads have a capacitive reactor therein, the reactance of which is substantially greater than the total inductive reactance of the transformer.

5. Apparatus for igniting and operating at least one gaseous discharge device from a source of A.C. voltage insuicient to ignite said gaseous discharge device, which comprises, a shell-type iron core having a central winding leg and side framing legs, a transformer comprising a secondary winding and a primary winding mounted on said core with the primary winding formed of two parts and the secondary winding being coaxial with the central winding leg and having the two parts located at opposite ends thereof, the primary winding adapted to be connected across said source, means including electrical leads for connecting said primary winding and secondary winding in voltage step-up transformer relation with one another and at least said secondary winding across said gaseous-,discharge device, a siot in the central winding leg approximately at the center thereof completely within. said secondary windingand at least ashunthaving high reluctance gap between one of said parts and said secondary winding.

6. Apparatus as claimed in claim in which there is a second similar shunt between the second of said parts and said secondary winding.

7. Apparatus as claimed in claim 5 in which there is a second slot in said central winding leg, also completely within said secondary winding, but located substantially closer to one part of said primary winding than the other.

8. Apparatus as claimed in claim 5 in which said primary parts are connected in parallel with one another.

9. Apparatus as claimed in claim 5 in which said primary parts are connected in series with one another.

10. Apparatus for igniting and operating a pair of gaseous discharge devices from a source of A.C. voltage, which comprises, an elongate iron core having a central winding leg, a transformer mounted on said core and having a secondary winding and a primary winding all mounted coaxially along said central winding leg, said primary winding having two parts and the secondary winding being physically located between said parts, means including electrical leads and a series capacitor forconnecting said primary and secondary windings in voltage aiding auto-transformer relationship and across both of said gaseous discharge devices in series, and said last mentioned means including a capacitor shunting one of said gaseous discharge devices, the primary winding adapted to be connected with said source, and means in said central winding leg for adjusting the coupling of said primary parts and secondary and the leakage reactance of said secondary winding comprising at least one relatively large transverse slot substantially in the center of the said central winding leg between the ends thereof beneath the secondary winding.

11. Apparatus as claimed in claim in which there is at least one gapped shunt between said secondary winding and one of said primary parts.

12. Apparatus as claimed in claim 10 in which there is a second transverse slot in said winding leg spaced from said one slot closer to one of said primary parts, and also beneath said secondary winding.

13. Apparatus as claimed in claim 12 in which there are gapped shunts between each ot said primary parts and said secondary winding.

14. Apparatus of the character described adapted to be energized from an A.'C. source, comprising, a pair of gaseous discharge devices connected in series and having a starting capacitance shunting one of said devices, an elongate iron core having a central windinv leg, a transformer mounted on said core and including a primary winding adapted to be connected to said source and a secondary winding of a number of turns many times the number of primary turns, said windings being mounted coaxial with said central winding leg along the length thereof, the length of the core being several times its Width and there being relatively narrow windows confning said windings whereby the physical length of said secondary winding is greater than half the length of said core, the primary winding and secondary winding being connected in voltage aiding auto-transformer relationship and across said pair of gaseous discharge devices and there being a series condenser in said connection, the primary winding being formed of two physically separated parts located on opposite ends of said secondary winding at the ends of said central winding leg, and said central winding leg having a transverse slot with closed ends located in the center beneath said secondary winding.

15. Apparatus as claimed in claim 14 in which there is another similar slot, albeit of shorter Width in said winding leg spaced between the rst slot and one end of the said secondary winding.

16. Apparatus as claimed in claim 14 in which said primary parts are connected in series with one another.

17. Apparatus as claimed in claim 14 in which `said primary parts are connected in parallel with one another.

18. Apparatus as claimed in claim 14 in which gapped shunt means are provided between each of said primary parts and the secondary winding.

19. Apparatus of the character described adapted to be energized from a source of A C. voltage, comprising, a pair of gaseous discharge devices each having a filament at opposite ends thereof, and the devices being connected in series with a condenser shunting one of the devices, a transformer having a secondary winding and a primary winding connected in voltage step-up transformer relation and at least the secondary being in connection across said pair of devices and having a series condenser in said connection, a plurality of lament windings coupled with said primary winding, and an iron core mounting said transformer, said secondary winding having a substantially greater length than width, said core having a central winding leg, said secondary winding being mounted coaxial of said central winding leg, said primary winding being formed of two parts and there being a part located adjacent the opposite ends of said secondary also coaxial of said central winding leg, said central winding leg having a central bridged gap beneath said secondary winding, and gapped shunt means between said secondary winding and at least one of said primary parts, said primary winding adapted to be connected to said source.

20. Apparatus as claimed in claim 19 in which said core has elongate winding windows and the said secondary winding is disposed in one window, and each of the primary parts in other windows, and the said filament windings also disposed in the windows of said primary parts.

21. Apparatus for igniting and providing the operating voltages for at least one gaseous discharge device from a source of A.C. voltage insufficient to ignite said gaseous discharge device, which comprises, an elongate iron core having an elongate winding leg and at least one parallel side leg forming therewith a plurality of windows, a transformer mounted on the core and having a primary winding formed of two parts and a secondary winding, the secondary winding having a physical length substantially greater than half the length of said winding leg and being mounted in one of said windows on said winding leg with the parts of said primary winding mounted in Others of said windows coaxially with said secondary winding on said winding leg and being located on opposite ends of said secondary winding, the primary winding adapted to be connected across said source and having an auto-transformer connection with said secondary winding, means including electrical leads for connecting said gaseous discharge device with said secondary and primary windings to be subject to the combined aiding auto-transformer voltages thereof, and a bridged gap in said core substantially at the center of said secondary winding and completely enclosed therein.

22. Apparatus for igniting and operating at least one .gaseous discharge device from a source of A.C. voltage msuicient to ignite said gaseous discharge device, which comprises, a shell-type iron core having a central winding leg and side framing legs, a transformer comprising a secondary winding and a primary winding mounted on said core with the primary winding formed of two parts and the secondary winding being coaxial with the central winding leg and having the two parts located at opposite ends thereof, the primary winding adapted to be connected across said source, means including electrical leads for connecting said primary winding and secondary winding in voltage aiding auto-transformer relation with one another and across said gaseous discharge device, a slot in the central winding leg approximately at the center thereof completely within said secondary winding, and at least a shunt having a high reluctance gap between one of said parts and said secondary winding.

l23. Apparatus of the character described `adapted toa-be energized from a source of A.C. voltage, comprising, a` pair of gaseous discharge -vdevices each havingaV lament at opposite ends thereof, and thedevices being connected in series with a condenser shuntingone of the devices, a transformer having a secondary Winding and a primary Winding connected in voltage aiding autotransformer relation. and across said pair of devices and having a series condenser in said connection, a plurality of filament windings coupled with said primary winding and an iron core mountingfsaid transformer, said secondary-Winding havingv a substantially greater length than Width, said core yhaving a central Winding leg, said secondary Winding being mounted coaxial of said central Winding leg, said primary winding being formed of two parts and" there being a party located adjacent the opposite ends ,oi said secondary also coaxial of said central Winding leg,

said central winding leg having a central bridged gap beneath said secondary winding, and gapped shunt means between said secondary winding and at least one 'of 'Said primary parts, said primary Winding adapted to be connected to said source.

References Cited in the le of this patent UNITED STATES PATENTS