US2518874A

US2518874A - Transformer system

Info

Publication number: US2518874A
Application number: US731991A
Authority: US
Inventors: Albert E Feinberg
Original assignee: Advance Transformer Co
Current assignee: Advance Transformer Co
Priority date: 1947-03-03
Filing date: 1947-03-03
Publication date: 1950-08-15
Anticipated expiration: 1967-08-15

Description

Aug. 15, 1950 A. E. FEINBERG,

TRANSFORMER SYSTE Filed` umn s, 1947 INVENTOR.

Albert E. Feinberg By A Homey Patented Aug. ,-15, 1950 UNITED STATES PATENT OFFICE t f 2,518,814 I 'mwst-oma SYSTEM poration ot Illinois applicati@ Mann s, 1w, serial No. 731,991 s claims. (ci. 32a- 451) This invention relates to transformers, and more particularly to a transformerV for operating a plurality of hot cathode glow discharge tubes, such as fluorescent tube lamps.

In order to improve the power factor of lighting circuits in fluorescent tube lamps, and for other desirable purposes, it hasbeen customary to operate the tubes in pairs off of a single transformer. The transformer has a primary winding and a pair of secondaries, one for each fluorescent tube, the secondaries being connected in step-up auto transformer relationship with the primary. A condenser is provided in series with only one of the tubes and of sufficient capacity to cause that tube to draw a leading current to compensate for the lagging current taken by the other tube. Y

Fluorescent lamps of the hot cathode type are started by providing a temporary series connection between the filaments at the opposite ends of the tube. In starting two lamps which are operated from a single transformer in a circuit as above set forth it has been found that the condenser in series with one ofthe lamps in many instances reduces the current flowing to that lamp to an undesirable amount. In addition, in many instances there is sufiicient intercoupling within the secondary coils of the transformer so that a reduction of thecurrent flowing in that secondary `which is in series with the condenser results in an increase of the current flowing in the other secondary which is connected to the other lamp. Thus the condenser not only diminishes the amount of current flowing to one of the lamps but frequently also increases the amount of current flowing to the other lamp, both changes being to undesirable degrees. The resulting voltages across the lamps are also changed.

Itis one of the objects of the present invention to provide an improved transformer structure and circuit arrangement wherein the current -wave of the leading lamp issubstantially sinusoidal, thereby eliminating the third harmonic which is otherwise frequently present in the wave form. It is a further object of the present invention to provide a transformer ofthe above mentioned character wherein the circuit arrangement is such as to permit a much lower saturation of the iron core and therefore a correspondingly lower maximum temperature rise in the iron. Itis a still further object of the present invention to provide a circuit 'arrangement wherein the secondary requires a lower flux density thereby permitting a diminution in thev to the drawings wherein like reference numeralsv designate like parts throughout.

In Figure l there is shown a transformer I comprising an iron core formed of a stack'of L- shaped laminations assembled through six similar (but not identical) coils. Each lamination includes a longr leg 2 and a short leg 3, the laminations being assembled so that the abutment 4 between adjacent laminations in the same layer are at thelopposite corners of a rectangle, and with the abutments 4 of adjacent layers staggered at opposite sets of corners of the rectangle. The transformer of Figure 1 includes a pair of series connectedprimary coils 6 and l, a pair of series connected secondary coils 8 and 9 which will ultimately supply the leading current, and another pair of series connected secondary coils I0 and Il which will ultimately supply the lagging current. The two coils 6 and I will hereinafter be referred to as the primary, the two coils 8 and 9 will hereinafter be referred to as azsecondary and the two coils I0 and II will hereinafter be referred to as another secondary. Each secondary is connected in step-up auto transformer relationship to the primary. The secondary I0-II is connected through a lead I5 to one side of a filament I6 of a hot cathode glow discharge tube I 8, of the fluorescent type. The other side of the filament I6 is connected through a starter I9 to one side of a filament 20 of the lamp Il. The other side of the filament 20 is connected to one line of the source of power 2|. The secondary B-S is connected through a lead 25 to the winding 26 of an iron core reactance from which the circuit is extended through a condenser 21 to one side of a filament 28 of the leading lamp 2S, which is also of the hot cathode glow discharge type. preferably a fluorescent lamp. The other side of the filament 2l is connected to a starter 30, preferably, although not necessarily. in series with a compensating winding 3| and then connected to the opposite filament 3i of the dred sixty turns.

former.

lamp 29, that illament being also connected to the line 2|.

In the construction herein shown the primary coils 6-1 are located as close as possible to the secondary coils 8 and 9 and as far as possible from the secondary coils I and In one preferred construction involving a transformer for use on a 118 volt 60 cycle line with two tubes each of 40 watts,` each of the primary coils was two inches long and contained nine hundred turns. Each of the secondary coils was one and ninesixteenths inches long and contained seven hun- The coil 26 contained five hundred turns and the compensating winding 3| contained three hundred fty turns. The windings 2|A and 3| were connected in cumulative series during starting to constitute a step-up trans- When the starting switch opens its circuit the compensating winding 3| is, of course, open circuited.

In the circuit of Figure 1 the secondary |0| is loosely coupled with the primary so that there is sufficient leakage reactance to limit the current flowing to the lamp |8, during starting, to its correct operating value. being close to the primary has insufficient leakage reactancev to supplythe proper operating current to the lamp 29 when used in series with the condenser 21 which is of a size such that the capacitative reactance of the condenser is substantially greater than the inductive reactance of the windings 8-9. The reactor 26 is of such a value that during operation the sum of the reactance 26 plus the reactance of the coils 8-9, in relation to the capacity reactance 21, is of the correct value in relation to the open circuit voltage and lamp impedance to supply the proper operating current to the lamp. The effect of the reactance 26 is to correct the crest factor of the current in the lamp 29 to a much lower value than can be obtained without it.

As a result of the circuit arrangement shown in Figure 1 the current wave form of the leading lamp 29 is essentially sinusoidal, and the watt output of that lamp is raised thereby permitting a decrease in the current flowing therethrough. The elimination of the third harmonic in the wave form and the reduction of the leakage reactance of the secondary 8-9 results in a much lower saturation of the iron core and correspondingly amuch lower temperature rise in the iron. Furthermore, due to the v,lower ux density required in the coils 8-9 it has been found possible to reduce considerably the number of turns in the other coils on the core, resulting in a still further decrease in heating and a saving in copper. The

compensating winding 3| may be wound on thev same iron core as carries the winding 26, or the compensating winding 3| may be on a different iron core.

The effect of the reactance 26 during starting is substantially greater than it is during operation, by reasonof the fact that during starting the compensating winding 3| is in the circuit whereas during operation the compensating winding 3| is not in the circuit.

The transformer and the

reactances

26 and 3| and the condenser 21 are all located in a single container or can from which extend the various connecting leads for the external circuit. This includes the leads that connect to the line 2|,

the lead |5, the two leads from the reactance 3|,'

and the lead from the condenser 21 that is to be connected to the lament 28. By this arrangement the circuit connections to the two lamps I8 The secondary 8-9 4 and 29 can be made as shown, whereby the reactance 3| may selectively be connected in circuit or disconnected from the circuit, depending upon whether or not the starter switch 30 is closed ,or open.

In Figure 2 I have shown a circuit arrangement substantially the sare as that in Figure 1, differing therefrom only in that the positions of the coils 1 and 9 have been interchanged. In other respects the two circuits are the same.

In compliance with the requirements Yof the patent statutes I have here shown and described a few preferred embodiments of my invention. It ishowever, to be understood that the invention is not limited to the precise constructions here shown, the same being merely illustrative of the principles of the invention. What I consider new and desire to secure by Letters Patent 1. Apparatus for supplying a plurality of separatly operable hot cathode glow discharge devices with leading and lagging currents respectively comprising an elongated core, a primary positioned on said core intermediate the ends thereof, a pair of secondaries positioned on the core one at each end thereof, each of the secondaries being connected to the primary to form a ste -up auto transformer, the primary being subs ntially closer to one of the secondaries than to the other secondary, a condenser in series with the secondary that is closest to the primary, and a two coil inductance with the coils thereof inductively coupled together and separate leads extending from the respective coils of the two coilzinductance to permit selective connection of one or both of the two coils of the inductance in series .with one another and with the secondary coil that is closest to the primary.

2. Apparatus for operating two hot cathode discharge tube loads, comprising a transformer having a two coil primary winding, a leading secondary winding having two coils, a lagging secondary winding having two coils spaced from the primary and less closely coupled thereto than is the rst secondary, a core for said windings, said core being of an elongated rectangular shape one coil of each of the three windings being on one longitudinal side of the core and the other coil of each winding being on the other longitudinal side of the core, leads from the respective secondaries for individual connection to different tube circuits, a condenser in the circuit of the lead from the leading secondary, and a two coil reactor having an iron core separate from the aforementioned rectangular core and magnetically coupling the coils of the reactor, one of the reactor coils being connected in series circuit with the condenser and the leading secondary and the other reactor coil having conductor leads therefrom for permitting the selective connection thereof into said series circuit during starting of the tubes and out of said series circuit during operation of the tubes, so that the value of the reactance may be changed as the associated tube changes from starting condition to operating condition.

3.' Apparatus for operating two hot cathode discharge tube loads comprising a transformer having a primary, a fu'st secondary, a second secondary spaced from the primary and less closely coupled thereto than is the first mentioned secondary, both secondaries being electrically connected to the primary in step-up autof 5 tudinai sides joined ty ondaries and said primary each comprising two series connected coils one on each of the two opposite longitudinally extending sides of the core, leads from the respective secondaries for indi- ;'vidual connection to different tube circuits, a

reactor coil and a condenser in series and connected in series with a lead from the rst secondary, said reactor coil having an iron core and being outside of the magnetic circuit of the tionship, said transformer having a rectangular core including opposite longitudinal sides joined by transverse ends, said secondaries and said primary each comprising two series connected coils one on each of the two opposite longitudinally extending sides of the core, leads from the re-V spective secondaries for individual connection to dierent tube circuits, a reactor coil and a condenser in series and connected in series with a lead Afrom the iirst secondary, said reactor coil transverse ends, said sechaving an iron core and being outside of the magnetic circuit of the transformer, an additional coil on said last mentioned iron core and magnetically coupled to the reactor coil, a starter switch in the circuit of the leading tube with the condenser, and circuit connections including said switch and said additional coil in circuit between the heating laments of said last mentioned tube and open circuiting said additional coil upon opening of the starting circuit of said last mentioned tube.

5. Apparatus such as defined in claim 2 wherein the two primary coils and the two leading secondary coils are adjacent one another and with one of the primary coils adjacent an end of one longitudinal side of the transformer core and one leading secondary coil adjacent the corresponding end of the other longitudinal side of the transformer core.

ALBERT E. FEINBERG.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Y Date