US2637833A - Lighting system and apparatus - Google Patents

Description

May 5 1953 F. H. sKRo'rzKl 2,637,833

LIGHTING SYSTEM AND APPARATUS Filed Aug. 20, 1948 'ear/3a H Patented May 5, 1953 UNITED STATS fifElli'i @ENCE LIGHTING SYSTEM AND. AllEAJRA'IUS Frederick-"H, Skrotzki; Brooklyn, N. Y., assigner toNational'Inventions tlorporation, a corporation of New Jersey Application August 20, 1948,-Serial N o. 415,401,

m'ents of' the Fire-Underwriters are satisfied;`

whereiny current limitation' is.. successfully achieved `'in simple manner; together with required good system power factor."

Anotheroobject is to provide a 'powerunit for the lighting-system 'of thegeneral' .type just hereinbef'oredescribed; whichrunit is small, compact.

unitaryrand self-contained; of eXtreme-ly simple external contour;` which is ruggedsai`e"and certain under all operating conditionseznploying but a` minimum of iron and coppenwhile effectively precluding'hazard of system overload; which operates under ygood temperature regulation," and which is further characterizedby its low cost,4 rapidity and simplicity of construction; the readyV manner iii/Which; once assembled, it can `be conditionedicr operation; and by'its long useiul life', sooth'at only' infrequent repairs are required,"

simplein-:nature and easily'carriedinto effect.

These and many other desirable `oln'ects'and advantages `attendupon` thel practice of rny 1inventionyas will. be more yfully pointed. out hei-cir 1 after yc`u1r;ir1g1tl:ie coursevof the following 'descrip- Y tion.

lVly inventionvaccordingly -Will be seen to reside inthe several parts, elements .and features "of" construction as describedy herein, the scope ofV the application of which will more fully appear in the claims atv the-end of `this specification.y

In the several -views ci the drawings, whereinkv system and apparatus incorporating the wiring diagram oli-Figure l; and

Eigureis a .schematic diagram or 'a 'modified former Alighting system andrapparatus according.

to my invention:

Lilreueleren characters denote., like parts throughout the several-- views.

(Cl. S15-#4.87)

n As conductive to a more .thorough understand.- ing oi my invention it may be noted at this point thatconsifierable time and eort has `beendevoted in the art, to the production of iluorescent tube lighting systems wherein a plurality of tubes are rapidlyand `certainly brought into operation under prevailing andV available voltage supplies, and thisregardless of variation in, and the existence of extremely adverse, Weather conditions.

Because of the competitive nature of the art and the small margins of prout which are available, and 'because of the necessity that substantial operational'advantages exist to justify replacement oi existingincandescent lighting systems of fluorescent tube lighting, .it is-essential.

that such systems, in addition to possessing the several advantages hereinbefore referred to, as, Well, display the features otinitial lowcost, and,

stuxdiness and reliability, in operation. lin short, the requirement must be satisfied that such equipment capable of production through the use of assembly-line methods, so .that iollowingproduction,. but. little if any specialized attention .Will be required to condition a 4particular system for actual operation.

For one reason or another, known fluorescent tube lighting systems', and as well, known power units, have not satisiled all of the foregoing. To illustrate, one system-employs a transformer havingy tivo or more secondary windings. This iinrnediately :increases the complexity of design of the. transformer, and as well, increases its-physical dimensions, thequantity of iron required and the amount of copper employed. .The cost increases.; Moreover, the use ci such a transformer hasrequired-the provision of high leakage reactanceair'gapsf. These immediately increase both thecornplesity,crdesienthe initial cost ol materials,;and asyvvell, the amount of tert board work which is vrequired-in .adjusting the transformerl tical disadvantage -When measured from the The choke coils expensiveA standpoint or cost. and .add to size and Weight of the power unit.

It is anv important object myl invention,-

therefore, to provide a gaseous discharge tube lightingsys em and apparatus in which the aforementioned objectives are achieved end which in large .measure avoidthe several vdisadvantages` vhereinbefcire referred to.

Briefly stated, my invention comprises two fluorescent discharge tubes of generally like rating, connected electrically in series with each other. To energize these, I employ a closecoupled transformer. This may be either of the shell-type or the core type. referably, I einploy a shell-type core symmetrical in construction and formed of the usual laminations. While it is entirely possible to employ ordinary transformer connections with separate primary and secondary windings, I prefer, to achieve economies in the quantity or" copper employed, to connect these windings in autotransformer connection and to the tube in series.

An important part of my invention is to make provision that the arcs will be struck across the tube almost instantaneously, and this at a voltage approximately that of one tube only. To achieve quick starting and low secondary voltages, I shunt a small capacity condenser across one of the two tubes. The impedance of this -condenser being substantially less than that interposed by the initially high resistance of the associated fluorescent tube, the current initially transverses this shunt path, by-passing the associated tube, and thus contributes to the buildup of potential across the terminals of the second tube to almost the full secondary terminal voltage. Instantaneously the arc is struck across this second tube. the secondary system.

As soon as -conductive current ow is established across the one tube, the negative resistance characteristic of this tube brings about an important decrease in the voltage drop thereacross. Substantially all of the secondary voltage is now made available across the terminals of the first tube, so that the aro is quickly struck across that tube. Both tubes are thus brought into operation in practically instantaneous manner. The impedance interposed by the ohmic resistance across this rst tube is now lower than that interposed by the by-pass condenser, so that for all practical purposes, the latter is effectively shunted out of the system operation.

I provide a condenser of substantial size in one leg of the secondary circuit in order to limit the flow of current in the transformer and tubes. Such current limiting condenser, moreover, serves the further highly advantageous function of restoring to within permissible operational limits the basicly lagging system power-factor resulting from the inductive nature of the transformer.

As a renement of my invention, and to satisfy the requirement of the Fire Underwriters, I contemplate the provision of short-circuiting lamp holders or sockets at one end of each tube and so connect these with the primary winding of the transformer that upon the removal of either lamp from its corresponding sockets, the primary circuit of the lamp will be interrupted.

It will be noted from the foregoing that should that tube across which the by-pass condenser is shunted, fail for any reason, the system will continue in operation without appreciable electrical disturbance, inasmuch as the by-pass condenser will eectively substitute for the disabled tube, for all electrical purposes. Should the second tube, however, be disabled, the entire secondary system will go out of operation. Upon failure of either tube, the primary circuit remains energized. It is only upon removal of either tube that, in accordance with the prac- Current commences to course tice of my invention, the primary circuit is deenergized.

And now referring more specifically to my novel gaseous discharge tube lighting system, attention is directed to the several views of the drawings wherein I disclose a shell-type transformer indicated generally at I0. While I disclose and prefer to use a shell-type transformer core, it is within the province of my invention to employ a core-type transformer. The shell-type core, indicated generally at II, comprises a central leg I IA and paired outer legs I IB, I IB, closed by end pieces IIC, IIC in close-coupled relation, and without the interposition of any high reluctance leakage barriers. I provide a primary winding and a secondary winding, indicated at I2, I3, respectively.

It will be seen from the foregoing that fundamental simplicity is achieved in the design of my transformer. The number of component parts is small, and these parts are quite simple. The iron content is reduced to a minimum, while at the same time provision is made for ready coursing of adequate flux throughout the transformer core, at substantially under saturation value.

By connecting the transformer windings in auto-transformer connection, important savings are achieved in amount and cost of copper employed, and this Without appreciable sacrifice in system performance. To this end I provide the primary winding with terminals I 2A, IZB, while the secondary winding is provided with terminals I3A, ISB. The terminals I2A, I 3A, disposed physically adjacent each other, constitute one pair, while the terminals 42B, |3B physically remote from each other, constitute a second pair.

Across the paired terminals I2A, I3A, and by means of leads I5, I 6, I connect a fluorescent tube I 4. Preferably, and as is shown in the present embodiment, I provide the tube I4 of the hotcathode type, to facilitate ready striking of the arc at comparatively low terminal voltages, and under adverse operating conditions. It is entirely within the purview of my invention, however, to employ cold-cathode tubes where desired, thereby achieving greater sturdiness and longer life. Across the leads I5, I6, and shunting tube Ill, I provide a condenser I'I of low capacity rating, say in the order of 0.5 microfarad capacity. The function of this condenser will be disclosed at a later point herein.

While I have shown the by-pass condenser I1 as shunted across the tube It, disposed between the physi-cally adjacent terminals IZA, I 3A of the transformer primary and secondary, this is by no means mandatory; it is equally within the contemplation of my invention to insert the condenser I'I across the tube 20 as indicated generally at I'I' in Figure 3.

It is within the contemplation of my invention that an ohmic resistance be inserted in the stead of the by-pass condenser I 7. Experience has disclosed, however, that where an ohmic resistance is employed, and for any reason the associated tube I4 fails, then the full voltage which theretofore existed across tube I4 is impressed across the by-pass resistance, so that this latter is soon burned out, unless it be designed for the passage of heavy current. To construct the resistor to handle such heavy currents results in a product which generally is considered initially too costly and which is too bulky for operation. Such a resistance would have to be in the neighborhood of 50,000 ohms. A physically large re- .Sister :is .denitely impractical. An yohxnic resistor cof smaller dimensions would be `complieated by the requirement of .some protection, such, :for example, as a ruse. All 'in all, ithereiore, the use of fa. :by-pass 7condenser is den-- nitely indicated, -in Ypreference 4to an ohmic :refsistance.

Across terminals IZB, I3B, as by vleads 18 1:9,1 insert, in :series-connection, a second ftluorescent ttube .20.. This nuorescent tube l'of the same type and commercially the same rating as the tillbe Ill.

Ellhe :primary `Winding t2 is energized from @any :suitable source 25 :of primary ,service 4say yof .-110 `.012.220 fvolt `rating, by ymeans "of leads :21, 122 connected to :lead ,Ir5 and to lead i8, respectively, .and thenceto primary terminals 12A, I2B. .'Inieluded in this circuit preferably are-shouting type 'lamp .holders or fscekets .2,8 and 124 :for vtubes d! and.2.5 respectively.

The connection -of the tube sockets, as conyeniently illustrated, .is :such that upon the :insertion of the Itube Within the socket, 'a break 4tl-'ferr,totorfe -existing in "the ,primary circuit :is closed, and remains closed eso :long `as ,the .tube .is carried within the socket. Upon the :removal of either tube vfromz-its corresponding'socket, however, the primary circuit is again interrupted, iso :that 'the system 'stands ie-energized To yil- ;lust-rate, upon removal @of tube HI from socket 23, a break occurs in the lead 2l, -.I`5 to termi-nal 12A, -and `the primary ycircuit :is -de-energized. Sinni-arly, upon removal of vtube 20 lfrom its .corresponding socket :a w'break loccurs `in the lead 22, i8, :and :the primary Acircuit is again tde-eneragized. .Thus, the system A*is riool-proof `so far as concerns the removal :of either tube, and lthe requirements of 4the 'Fire Underwriters are satised in this respect.

It will be noted rom fthe foregoing that tno ,provision has been .made in the 4transformer las :heretofore disclosed for the .introduction of some high leakage reactance or other .current-impedi-ng means. 'Because of 'the negative resistance ,characteristics xoff the tube, therefore, it Jwould appear "that without more, :the :current :build-'up :in l:tl-1e system -wouldfreach .damaging values. .The simpliiication ci the .transformer construction :as 4heretofore described Ais made r'possible, however,

iby :the introduction :into the .systemfola :currentlimiting condenser ,26. This `condenser 2li J,ai-so .tends lto introduce :a leading component vvinto the cpoadraturc :geometry of the .basicly .lagging power-factor, andvtendsto restore the same sumciently ltowards unity `value as 'to'be vWitllin pern operation of my system, "for an assessed .half-'cycle rof 'the supply, primary current ilows to the "left (Eigure 2f) `from source 25 4through lead '22, zshort-c'ircuiting `terminal 211, lead "I8 to terminal IZB `of primary 'winding 12. *The prmary current then courses tothe :right Tin Fig- -ure `2 .across the primary winding 'I2 and then :across terminal 12A, 'lead )I 5 .short-circuiting terminal .socket .23, .and `lead 2I .to lthe right-hand .side l:of the primary `energizing source 25.

VlVhen :the ,primary Winding `I2 is .rst .energized, rthe .arcs across -the tube I4 .and '.20 .are .not .yet struck. In Aoperation the .arc .across .the tube 20 will rst be struck inasmuch as .thedesign `oi? my `'new Vsystem :is such Athat substantially all of the secondary output voltage -is rst impressed across the terminals .fof this tube. Thereafter., .following striking ,of the are thereacross, .sub-

.stsntially .all kof the secondary .terminal voltage is impressed across the tube I4.

For the given half-cycle :of .current iiow the initial secondary ycircuit may be traced, illustratively, from primary winding I2 to the left across terminal 42B, lead I8., short-circuitng socket 24, tube 20, lead |19, terminal I 3B, across secondary -wi-nding 1.3 to terminal I3A, then lead I6 and current-limiting con-denser 26, to junction 3D. ThereJ because of vthe lower impedance `of bypass `condenser I y'1., the larger part of the secondary current courses lead 29, by-pass condenser .II and lead l28 to junction 21 and thence back through lead I5 and terminal IZA to the poi-nt -of beginning. In this manner substantially ythe entire secondary voltage is impressed across 'the tube 20.

Upon ignition iof tube 2 IJ., the resistance sharply falls. Current ows `through the tube limited only by the :system current-limiting means :26. The voltage drop -thereacross likewise diminishes substantially. YSu'listantially the entire ,secondvary voltage is ,now impressed across the :terminals of the `tube I4. The arc across tube M .thereupon strikes after -the passsage of but a few additional cycles of secondary current flow. Upon the occurrence of the sharp decrease Ain the ohmic resistance of tube I 4 in its energized condition, its total impedance vbecomes substantiallv less ythan that of ithe luy-pass condenser 1H, so lthat the Aarc discharge is maintained across both Vsaid Itubes until the system becomes de- .energized for any reason, as by opening the line switch, removal of either tube, :or failure 0f the tube 20.

With stabilized operating conditions, after initial :striking rof Vthe arcs, the flow :of output current yfor the 'assessed half-cycle `is from the left-hand -end of primary winding I2, across terminals IZB v'and lead I8, short-circuiting socket 2-4, ltube 20 lead I91 to lthe right-hand terminal .13B of :secondary winding I3, lead I'S, currentlimiting condenser 26, across junction 30, .and through Atube M to short-circuiting :socket 23. Thence 4the four-rent flows up .and across Jthe lead .I5 and junction l2'! -to the right-hand terminal '-LIZAof primary winding :I2 and thence across this nyindines to the pointof beginning.

For the reuerse half-cycle .of 'primary current flow, and Ycorrespending reverse of secondary current. the now is in the `opposite direction.

While as noted above, condenser 2E is illus- .trative'ly introduced yinto vtheflead 'I6 connecting the right-hand `termi-nal of vtube 14 (Figure 21) `.with the Vterminal 113A lor secondary Winding 113, it may be inserted in vlead I9, :in lead I 5, or .in lead fla. 'The capacity fofthis condenser is vnicely .chosen oi' such rating as will represent the .best :practicalcompromise `between the required cur- `rent Ilin'iiting `irripedance andthe required `correction `necessary to restore the system `power factor to within permissible :lim-its. Illustratively, I have :found :highly satisfactory operation -to vatten-d upon thence of a condenser of approxilmately .1.5715 nu'crofarards capacity.

Reliance on the :condenser 2t as the current- 4limiting means has mad-e ypossible extreme sim- 4pliiieation .oftransformer-design as Vhas vbeen sublgested ,hereinbefora attend-ed lby the substantial .elimination Koi' atest board operation after initial assembly. ln particular, the adjustment of .the `big-h lleakage reactance shunts as included 1in transformers heretofore :frequently employed, is eliminated. Jl-Ieretoore it has been necessary Lto ailaceeach unit on .a test zboard tocalibrate the same torated reluctance. This necessity results from variation in-thicknesses of the laminations Iof which the transformer cores are comprised,

lresulting from permissible manufacturing tolerances. Illustratively, while'say twelve lamina- `tions may be required in one assembly to achieve a rated reluctance, thirteen laminations may be required in another assembly in order to lower the reluctance of the air-gap to the required value.

It has heretofore been pointed out that an important feature of novelty resides in the fact that in the use of my new system, tube failure is not necessarily accompanied by `de-energization of the system. The further important advantage has been alluded to, that upon tube failure with the system being retained in operation, no possibility exists of damage to the component system parts.l In this connection reference to Figures l and 2 will show that upon failure of tube I4, with consequent extinguishment of the arc thereacross, there remains a conductive path across the by-pass condenser I 7. This shunt circuit, now constituting part of the main secondary circuit, inter-poses a secondary impedance somewhat greater than theretofore existed and thereby imposes an additional limitation on the effective secondary current which lcan fiow. Additional protection is thereby afforded to the tube 20, which remains energized land in operation, with the arc remaining struck thereacross. However, upon failure of the tube 2c, then since there is no bypass condenser about this tube, and since the tube is introduced in series-connection in the secondary circuit, the entire secondary circuit will become de-energized, although the primary 'circuit will remain closed.

' The further highly advantageous feature exists, moreover, as provided for by my use of shortcircuiting sockets 23, 24 for the tubes I4, 20, respectively, that upon removal of either tube vfrom the socket, the primary circuit is thereby broken, so that the entire system stands de-energized.

A further important feature of my invention is the very compact vpower unit which is made possible by the practice of my invention. To insure this construction the transformer l is of minimum size since no shunt is employed and the voltage required is only approximately that for one tube. Moreover, the by-pass condenser Il and the current limiting condenser 26 preferably are found in a single container; ,this vappearing as a single condenser with terminals for the small capacitor and others for the large capacitors. ual. condensers may be used.

I arrange the transformer and condensers in juxtaposed position, snugly fitting within an outer casing or housing contoured and proportioned for snugly receiving these elements. The power unit is therefore of smallest possible compass, and can be handled as a single element.

By the employment of my new construction, it is made practical to obtain satisfactory system operation which attends the use of transformer powering equipment. At the same time the complexity of the transformer design is reduced to a minimum, and the costs thereof likewise minimized. Quick starting is achieved under the most adverse operational conditions, including outdoor service under damp, frigid weather conditions. The system is absolutely fool-proof in that upon removal of veither tube from the socket, the primary energizing system is broken. Failure of either tube interposes no serious hazard Where desired, however, separate individl 'in that When'on-e such tube fails for any reason',

the entire secondary system is de-energized, while should the other tube fail, the ysecondary impedance is slightly increased and the remaining tube continues in operation. This has been verified .by removing the tubes while maintaining the primary circuit closed through the corresponding socket.

Simplification of transformer design removes any requirement of adjusting the shunts of the high leakage reactance transformers heretofore employed. A t all times the current is maintained within safe limits through the use of a currentlimiting condenser. This condenser not only serves for its intended purpose, but as well, corrects the system power factor to within permissible limits. It is observed that the introduction of this condenser into the system is. not accompanied by any adverse reasonance peak potentials, wave form being entirely satisfactory. l Through the use of my new system, seriesconnected tubes can be both initially started and subsequently operated from a single transformer, while complying with all requirements of the Fire Underwriters and operating from readily available service supplies of usual voltage ratings. A compact power unit is made possible, with substantial savings in both iron and copper. From the standpoint of method, simplified starting and subsequent operation of the tubes is made possible.

Since many embodiments of my invention will readily suggest themselves to those skilled in the art, and since many modifications of the present embodiment will likewise occur, Aonce the broad aspects of my invention are disclosed, I intend that the foregoing be construed as simply illustrative, and not by way of limitation.

I claim as my invention:

l. A fluorescent tube lighting system, comprising a close-coupled transformer having a. primary winding adapted to be connected across a source of alternating current supply of predetermined frequency and a secondary winding, a positive column fiuorescent gaseous discharge tube connected between one end of said primary and one end of said secondary windings, a second positive column uorescent gaseous discharge tube connected between the other ends of said windings and placing said primary winding, said secondary winding and said two tubes in series connection, a by-pass condenser shunting one of said tubes, and a power-factor correcting condenser in series with both of said tubes.

2. A fluorescent tube lighting systemy comprising a close-coupled transformer having a primary winding adapted to be connected to a source of alternating current supply of predetermined frequency and a secondary winding, a pair of series-connected positive column fluorescent gaseous discharge tubes of generally like rating connected across said transformer, one being connected between one end of each of the windings and the other being connected between the other ends of the windings, a capacitative reactance shunted about one of said tubes, and two short-circuiting sockets for receiving said tubes and connected in series with the primary winding of said transformer and with the connection to said source to break the primary current upon removal of either of said tubes.

3. A fluorescent tube lighting system, comfprising a close-coupled transformer having a single primary winding adapted to be connected to a source of alternating current of predeter- FREDERICK H. SKROTZKI.

References Cited in the le of this patent UNITED STATES PATENTS Number Name Date Hendry Oct. 30, 1928 Boucher Mar. 13, 1934 Osborne Dec. 24, 1935 Foulke Oct. 6, 1936 McCarthy Dec. 30, 1941 Gustin Aug. 15, 1944 De Reemer June 4, 1946 Dosio Mar. 18, 1947 Mueller Sept. 9, 1947 Nathanson Feb. 24, 1948 Foster June 15, 1948

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