US2683798A

US2683798A - Three-phase fluorescent lighting system

Info

Publication number: US2683798A
Application number: US225350A
Authority: US
Inventors: Frederick E Craig
Original assignee: Individual
Current assignee: Individual
Priority date: 1951-05-09
Filing date: 1951-05-09
Publication date: 1954-07-13
Anticipated expiration: 1971-07-13

Description

July 13, 1954 cRAlG 2,683,798

THREE-PHASE FLUORESCENT LIGHTING SYSTEM Filed May 9, 1951 lNVE/VTOR FREDER/CK E CRAIG WM y,

F/G. Z J? Arr'rs Patented July 13, 1954 THREE-PHASE FLUORESCENT LIGHTING SYSTEM- Frederick E. Craig, Lynn, Mass. Application May 9, 1951, Serial No.'225,350

I 11 (Jlaims. 1

This invention relates to lighting apparatus employing light sources of the electric discharge type. In the illustration disclosed in this specification it is applied to apparatus in which the light sources are fluorescent lamps; and that fact is indicated by the title. However, the invention is applicable to all situations in which electric discharge light sources of any character are connected in the several phases of a three phase alternating current, and its scope is to be construed accordingly.

The objects of the invention include that of eliminating flicker and stroboscopic eliect in the operation of such light sources with greater efficiency and economy than has been possible with apparatus heretofore known; and to provide a lighting fixture for operation by three phase alternating current with a compact and economical ballast by which light of substantially uniform intensity and continuity is obtained. A related object is to provide a self contained ballast for use in the operation of gas type lamps in a three phase circuit in which the transformers for all of the lamps have a single continuous magnetic circuit and all,

together with associated equipment, are contained in a single case.

A further object is to provide circuit connections between the parts of the ballast and the sockets which removably contain the lamps, so disposed as to deliver current to the lamps of sufficiently high voltage to insure starting, and at the same time to eliminate possibility of dangerous voltage being passed through a person who may carelessly handle a lamp when inserting it into its high voltage socket.

I am aware that it has been proposed heretofore to furnish a steady light by connecting three single phase gas filled lamps in the several phases of a three phase circuit; but, to the best of my knowledge and belief, no combination of such a collection of lamps with a three phase ballast in one fixture has ever been made or proposed.

My invention consists in a combination by 4 which the objects precedently set forth are realizedand, in the preferred embodiment of which, three single phase lamps are mounted on a single fixture and are connected with a ballast in the same fixture, such ballast including-transformers for the several lamps having a single continuous magnetic circuit, and reactors, all cempactly'assembled and encased as a unit subcombination and the parts of which are connected withthe sockets of the lamps insuch v diagram, Fig. 4.

2 manner as to eliminate danger from electric shock to persons who may carelessly handle lamps while inserting them into the high voltage lamp sockets.

A further object of this invention comprises an arrangement by which should any of the three single phase lamps be removed from the fixture or become otherwise inoperative, the other lamp or lamps will remain lighted with the same brilliance as though all three lamps were in operation.

In the accompanying drawings Fig. 1 is a perspective view of a lighting fixture having three tubular gas filled lamps and including an embodiment of the other features of the invention;

Fig. 2 is aside elevation of the fixture shown in Fig. 1 and representing by broken lines the casing of the ballast which is contained within the lamp fixture housing;

Fig. 3 is a plan View of the ballast on a scale larger than that of the preceding figures, showing the casing of the ballast in section on the line 3"3 of Fig. 2;

Fig. 4' is an electrical diagram showing the lamps and the parts of the ballast connected with a three phase alternating current power source and including connections by which high voltage is removed from the circuit whenever any lamp is removed from its socket;

Fig. 5 is a diagram somewhat similar to Fig. 4 but with the several transformer primaries arranged in delta.

Fig. 6 is an exploded view of the parts of a core with which the windings of all of the transformers of the ballast are assembled so as to provide a single magnetic circuit;

Fig. '7 is a longitudinal section of the assembled core taken on line 1-1 of Fig. 3 and shown on a larger scale.

Like reference characters designate the same parts wherever they occur in all the figures.

Tie fixture here shown comprises a canopy 10 adapted to be mounted on the under side of the ceiling of a room or any other overhead structure. A housing I! is suspended from the canopy by tubular suspenders or stems and It, through either of which electrical conductors can be passed to'the interior of the housing.

Projecting from the under part of the housing at the opposite ends are sockets in which the ends of tubular single phase lamps M, iii and 15 are mounted. Two of these lamps are shown in Figs. 1 and- 2, and the third is shown in the Those represented here are the commonly used gas filled fluorescent tubes of the electric discharge type having electrodes sealed into both ends. The sockets for these tubes at one end of the housing are shown at l1, l8 and IS in Fig. 1, and those for the tubes 14 and I at the other end of the housing are shown at '29 and 2|. The third socket at this end is shown at 22 in Fig. 4.

A case for the ballast transformers and auxiliary equipment is shown by dotted lines at 23 in Fig. 2 as being contained within the housing ll suspended from the top wall of the housing. This ballast or transformer case is shown in detail in Fig. 3 with the transformers and associated power factor condensers and reactors assembled therein as a unit combination. In the specific apparatus chosen for present illustration of the invention, there are three transformers, of which the windings are separately connected in the several phases of a three phase alternating current circuit and all the windings are combined with a single iron core structure disposed to furnish a single continuous magnetic circuit. The transformer windings are shown at 24, 25 and 26 in Fig. 3 and the core structure is shown in detail in Figs. 6 and 7. The latter has elements passing through and embracing the windings and is made of laminated parts and so designed as to permit easy assemblage with the windings and provide uninterrupted paths for magnetic flux within and around the windings.

Power factor capacitors

27, 28 and 29,

reactors

30, 3! and 32, and radio

interference preventer condensers

33, 34 and 35 are connected in circuit with the condensers, and all are mounted compactly in the case 23.

Reference is directed to the diagram in Fig. 4 for a showing of the connections between these several electrical elements and the lamps. The three wires L L and L from a three phase alternating current source are led through the suspender l2 into the ballast case 23 and are connected with the

transformer windings

24, 25 and 25, respectively. The transformers here shown are auto-transformers, having the primary and secondary windings designated 13 and s, respectively. The primary winding of transformer 24 is connected by a conductor 36 with the low potential socket ll of the lamp M, by a conductor 31 with one terminal of power factor condenser 21, and by a conductor 38 with one terminal of the radio interference prevention condenser 33. The secondary winding of transformer 24 is connected by a wire 39 with the opposite terminal of the power factor condenser and by a Wire ii) with one terminal of the reactor or choke coil 30. The opposite terminal of the reactor is connected by a wire ll with the opposite side of the condenser 33 and by a wire 42 with the high voltage socket 20 of the lamp l4.

The other transformer primary windings are connected by

conductors

43 and 44 with the low potential sockets of the lamps l5 and I5, respectively; the reactors 3! and 32 are connected by

conductors

45 and 56 with the high potential sockets of these lamps; and connections essentially like those first described are made between the secondary windings of transformers '25 and 26 with the

power factor condensers

28 and 29 and reactors 3i and 32, respectively, while connections essentially like those first described are made between the primary windings of

transformers

25 and 26 with the

condensers

28, 28, 34 and 35 and betweenthe last named condensers and the reactors 3i and 32, respectively. All of the low potential lamp sockets have tWQ separate contacts arranged to bear on the metal fitting on the low potential end of the lamp tube, which is connected with the electrode at that end of the lamp, when the lam is inserted into the socket. The several condenser primary windings are connected each with one of the contacts in the several sockets, as indicated by the diagram. In this diagram the points of connection of the

conductors

36, 43 and 46 with the sockets i1, is and i5, respectively, represent one of the contacts in each socket. The other contacts of the sockets l1, l8 and is are in shunted connection with one another by a conductor t1 and branch $3.

With this mode of connection, the three transformers are connected in a three phase star circuit and the shunt 47, s8 is the center connection with the star. The metal terminal fitting of any lamp, when inserted into its socket, bridges across the separated contacts in the socket and, when all of the lamps are in place, the star circuit connection of the three transformers is completed. When any lamp is removed, the circuit between the condenser to which that lamp is related and the center connection is broken.

The core structure of the transformers, the cores of the reactors, and the metal shells in which the power factor condensers are encased are all grounded on the case 23; an insulated conductor for that purpose being shown at 59 in Fig. 3, being connected to the case at 5% and having branches connected. with the several cores and transformer shells.

An important safety feature is afforded by the circuit connections of the ballast with the low voltage sockets of the lamps. The danger against which this safety feature protects is this: Burned out lamps need to be replaced from time to time, and a person making such a replacement could, by inserting one end of the new lamp into the high voltage socket while holding the other end of the lamp and being connected to ground, cause the lamp to start and be subjected to dangerous voltage if the full voltage were then applied to the socket. Such handling of a lamp in being mounted in its sockets is very liable to occur. I have removed the possibility of danger resulting from handling of a lamp in this manner by the circuit connections here shown, which cause the voltage in the circuit of any lamp to be reduced to a safe degree when the lam is removed. Thus, assuming, for instance, that the lamp 1 3 has been removed, then no current passes through the primary winding of the transformer 24 which is connected to that tube. Consequently the voltage is not stepped up in the secondary Winding of that transformer, but the voltage from the power line which passes through the secondary winding and through the reactor 38 is too low to energize a lamp, and the person who may place one end of a lamp in the socket 2! while handling it in the manner described is insulated-against any passage of current through his body.

The core structure of the ballast is. made of numerous originally separate parts constructed for easy assemblage with prewound wire coils and with each other into a unitary structure having magnetic continuity. In the illustrated embodiment, the individual pieces are cut from sheet iron .026 inch thick. Most of them have an outline similar to the letter E, consisting of a trunk portion a and three lateral branches 1), c and 01 extending to the same side from the ends and middle of the trunk portion. A smaller proportion of these pieces are of straight bar form having the same length and width as the trunk poraeeavee tions a. Groupsof three pieces eachareeassembled :in stacks. with-each wire coil and with-their branches overlapped. Thus the. group ot-pieces designated 5|] in Fig. 6 is assembled with .thegroup designated- 5| sothat their. branches: overlap and-the middle branches ofboth pass through the central. openings of thecoils. while the. end branches embrace the coils. Other. like groups are stackedonthe two groups. above. described and interleaved with the coils until a core. of the prescribedthicknesshas beenbuilt ups other groups-iband 53 are similarly stacked up. in assembled relation with thewirecoil of a second transformer. The/trunk. portions of'the groups in each stack are spacedapart fromone anothen by the thickness of the: overlapping branches, andthe trunk: portions: of the stacked up-groups52 areinserted intothe spaces between the=-trunk portions of the stacked groups 5!. Groupsof-bar shaped pieces 54 are inserted between-thetrunkportions of the groups 50-.

A thirdsetofg-roups Ea and 56- of E shaped pieces arestacked-in assemblage'with the third transformencoil in the sameway, and the trunk portions ofthe groups. 55 are inserted in the open spaces between the trunk portions of i the groups53= Finally,- groups of bar'shaped pieces 51 areinserted'inthe-spaces between the trunk portions of the-groups 56. Then'the whole assemblage makes a: substantially solid" laminated structure, as shown' in section in Fig. '7.

In; the winding 0f the transformercoils, the secondary coil is a wound outside of the primary coil so that it is situated next to the portions of the -iron-core by-which it is embraced. Also the; coils of one-of the transformers are wound oppositely to the-winding of theother-transformer coils. Thus-the-transformers 24 and ZS may be wound-clockwisei as to both the primary and secondary windings; and the transformer 25 wound counterclockwise; Orviceversa. This is an important factor, as it suppresses the third harmonic; preventing vibration.

The cores 58', 59-and60 of the several reactors are; also provided witha trunkportion and" three lateral branchesaround and=between whichthe several coils are located; The several cores are associated with barsSl, 62'and lid-which bridge across the branches of the cores and complete the magnetic circuitsthrough the-latter-. Gaps, which may be variedinwidth from zero to a limited'maximuin value, are provided between the bars andtheadjacentbranches of the cores. By adjustment of the width of these gaps, the strength of the currentpassing through the reactor coils may be varied and adjusted. Onceadjusted, the gaps are p referably filled with solid insulation and] thereby 'made permanent.

All of-the parts herein described, i; e., ballast, condensers and reactors, are compactlyassembled in thecase 23 and made fast therein. Although no specific fastening means are shown in the drawing, itmay be understood that any mechanical fasteners or other means suitable for the. pu pose can e. sed.

By assemblingthe transformer windings of all three phases ofthe power circuit in association with what is in effect a. single core, a muchmore compactiand enicient ballasthas been made, with a very-large saving of cost. These factors; ofefficiency, economy. and convenience are enhanced bythe assemblage of all.of;the parts ofgtheapparatus (ballast, condensers; and. reactors com pactly in a single case as a self-contained unit.

In this apparatus the transformers are designed to stepv upvthel. electromot-ive force to 600 volts when the .current. isetu-rned on, which is sufiicient tostart the lamps After starting. the voltage drops to a. continuously. operating value. The. reactors cut down the current to the prescribed strength, which. may be varied, as previously stated, by adjustments-of the. gap between the cores of'these reactors and=their associated-armature bars. The normal operating current is300 milliamperes. and it can be increased by this adjustment upto 500 milliamperes.

In Fig. -5-.the threetransformer primary windings. areshown. arranged in. delta, the line Ll being connected}. to-the mid-point of the autotransformer 24. while the opposite end of the primary-of thertransformer isconnected through lead 65 andthe socket I! with the mid-point of the transformer 26: and through loads 65 to the line L3; Similarly the opposite end of the primary of thetransformer 26 is connected. through the lead 61, socket l9. and lead 58 tothe line L2 and tothemid-point of the transformer 25, whilethe. opposite end of the primary of the transformer '25 iseonnectedthrough leads. 69 and 43, socket l8 and lead 10 with the line LI and to the midz-point of'the transformer 24. The ballast, condensers, and-reactorsare connected pre cisely as. in- Figure. 4; With this. arrangement shown in Figure 5, failureor omission of one or more of the lamps in no way interferes with the operation Many of the others, each of which has impressed on its terminalsat all times the voltage difierential between two of the lines LI, L2 and L3.

This application is a. continuation-in-part of my application. Serial No. 110,725, filed August 17, 19.49, for Three Phase Fluorescent Lighting System.

While I have given specific values for some of the features of the combination herein il1ustrated, it is. to beunderstood that these values are not limiting, but they may be varied widely within the limits known to be safe in this art. The principlesof the-described embodiment are applicable with modifications understood by those skilled in the art tofixtures designed for fluorescent lamp tubes of all the various lengths and diameters employed in practice.

I claim:

1. An electric lighting system comprising three single phase gas filledlamps of the electric-dis charge type; a transformer having three separate sets of primary and secondary windings assembled with a single iron core, connections for the flow ofcurrent between the separate phases of a threephasepowersupply source and the sew eral primary transformer windings, individual connections from the-several primary windings to the several lamps atoneterrninal, and-in iv-idual connections between the several secondary transformer-windingsand the several lamps at the-opposite-terminal thereof, said windings of said transformer being arranged in tandem .nd the middle winding being in the reverse direct. tot-he direction of 'the other windings.

2. An electric-- lighting apparatus comprising three single-phase gasenlledlamps of the electric discharge-type, three auto-transformer units in assembled relation; with alaminated ironst'ructure disposed;- to provide-- uninterrupted paths for magnetic fiuig around the transformer windings, the primarywindingof each transformer'being connectedqwith one oftheconductcrs of a'three phase alternatingcurrent supplydine and with the low potential terminal of one of the lamps,

7 and the secondary windings of the same transformers being connected with the high potential terminals of the respectively same lamps; such connections of each transformer with one lamp being separate from the corresponding connections of each of the other transformers with the other lamps, the primary winding of the central unit being reversely wound to the other primary windings.

3. A three phase lighting apparatus comprising three single phase gas filled lamps of the electric discharge type, high potential and low potential sockets in which the opposite terminals of the lamps are mounted, the low potential sockets each having two separated contacts which are bridged across by the inserted lamp, three transformers connected separately with the conductors of a three phase power supply circuit, conductors leading from the primary windings of the sevcral transformers to the low potential sockets of the several lamps, each connected to one of the contacts in the respective sockets, means connecting the other contacts of all of said low po tential sockets together electrically, and connections for flow of current from the secondary windings of the respective transformers to the Several high potential sockets, one of said primary windings being in the reverse direction to the other primary windings.

4. A lighting fixture comprising three single phase gas filled lamps of the electric discharge type and three single phase auto-transformers, each primary transformer element being connected in series with one contact of a two-cork tact lamp socket and the three primary transformer elements being connected separately to the separate phases of a three phase alternating source, the other contacts of said two contact sockets being connected separately to a difierent three phase alternating source from which the first said contact of the two-contact socket is connected.

5. An electric lighting starting and controlling system comprising three single phase gas filled lamps of the electric discharge type and three single phase auto-transformers having separate sets of primary and secondary windings, said primary windings being connected in star and to one terminal of a lamp and the corresponding secondary being connected through a ballast unit to the opposite lamp terminal 6. An electric lighting apparatus comprising three single phase gas filled lamps of the electric discharge type, a three phase ballast having three transformer units provided with separate sets of primary and secondary windings assem bled on a single core, each transformer winding being connected at its secondary terminals with the terminals of one only of said lamps, the intermediate terminal of each winding being connected to one of the phases of the supply and to the low voltage terminal of one of the other or" said lamps.

7. An electric lighting apparatus comprising three single phase gas filled lamps of the electric discharge type, a three phase ballast having there transformer units provided with separate sets of primary and secondary windings assembled on a single core, each transformer winding being connected at its secondary terminals with the terminals of one only of said lamps, the intermediate terminal of each winding being connected to one of the phases of the supply and to the low voltage terminal of one of the other of said lamps, said coils being arranged in tandem on said core, one of said coils being wound in the reverse direction to the winding of the other two coils.

8. A lighting fixture comprising a housing, three single phase gas filled lamps of the electric discharge type mounted on said housing, and a three phase ballast including three transformer elements mounted in said housing and having a single iron core, each transformer element being connected at its terminals with terminals of one only of said lamps, and the several transformer elements each having terminals connected separately to the separate phases of a three phase alternating current source.

9. An electric lighting system comprising three single phase gas filled lamps of the electric discharge type, a transformer element having three separate sets of primary and secondary windings assembled with a single iron core, connections for the flow of current between the separate phases of a three phase power supply source and one terminal of the several primary transformer windings, individual connections from the other terminal of the several primary windings to the several lamps at one terminal of such lamp, and individual connections between the several secondary transformer windings and the several lamps at the opposite terminal of such lamp.

10. An electric lighting apparatus comprising three single phase gas filled lamps of the electric discharge type, a ballast having three transformer units in assemblage with a unitary laminated iron core, one terminal of one of the primary windings of the several transformer units being separately connected with the several conductors of a three phase alternating supply line, the opposite terminals of the primary windings of the several transformer units and one terminal of the secondary of the said transformer units being individually connected with one terminal f the several lamps, and the other terminal of the secondary windings of the several transformer units being individually connected with the opposite terminals of the respective lamps. 11. In combination, means for supporting three gas filled lamps of the electric discharge type and a controlling circuit for said lamps including a ballast comprising three transformer coils, a laminated iron structure supporting said coils and disposed to provide a continuous magnetic circuit around each and all of said coils, each transformer coil being connected to one termiml of one of said lamps and with one conductor of a three phase alternating current supply circuit separate from the others, said coils being arranged in tandem on said laminated iron structure and the middle'coil being wound in the reverse direction to the windings of the other two coils.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,010,849 Dorgelo Aug. 13, 1935 2,020,707 Uyterhoeven Nov. 12, 1935 2,327,755 Abernathy Aug. 24, 1943 2,342,570 Biller Feb. 22, 1944 2,359,057 Skinner Sept. 26, 1944 2,461,957 Berger Feb. 15, 1949 2,472,882 Berger June 14, 1949 2,485,398 Mandi Oct, 18, 1949 2,491,858 Hehenkamp Dec. 20, 1949