US2509188A - Transformer - Google Patents

Description

y 23, 1950 v A. E. FEINBERG 2,509,188

TRANSFORMER Filed June 6, 1949 3 Sheets-Sheet l 4&2 im m Ill W y 1950 A. E. FEINBERG 2,509,188

TRANSFORMER Filed June 6, 1949 3 Sheets-Sheet 2 P01. y lead- .recondmyflwz imp 32 .33 .36

la 4e candy Lil/Le M m fim May 23, 1950 A. E. FEINBERG TRANSFORMER S Sheets-Sheet 3 Filed June 6, 1949 2 ii a a Patented, M 2a, 1950 TRANSFORMER Albert E..Feinberg, Chicago, Ill., assignor to Advance Transformer 00., Chicago, Ill., 2. corporation of Illinois Application June 6, 1949, Serial No. 97,381

This invention relates generally to transform- 8 Claims. (Cl. 171-119) ers and more particularly is directed to a transformer for operating a plurality of gaseous discharge devices such as for example, fluorescent tube lamps.

My invention is adapted for use with the socalled instant-start type of lamps, but is not limited thereto, being capable of utilization in any of the arrangements known for operating a, plurality of fluorescent tube lamps, especially where a high ignition voltage is required.

It has heretofore been the practice in circuits oi. the type with which my transformer is used, to utilize the combination of an auto-transformer with two reactors, one for each of two lamps, for example, In order to correct for the resulting low power factor, it was customary to connect a condenser in series with one of the reactors, which caused the particular reactor having the condenser to draw a leading current thereby compensating for the lagging current drawn by the other reactor. In assembling a device of this type it is advantageous to utilize as little iron as possible and as little wire as possible commensurate with the required induced voltage and resulting current. It is also essential for the maximum of efliciency insofar as lighting is concerned, to have the currents in the lamps as close to sinusoidal as possible. The greater variation from a sine wave, the less light is obtained from a given current passing through a lamp.

It is accordingly a broad object of my invention to provide a. transformer which will require a lesser amount of wire and iron than ordinarily used, but which nevertheless will provide a current wave with substantially sinusoidal shape.

In building high leakage reactance transformers for the purpose described herein, where a leading current is drawn in a high inductance secondary as in the case of that portion of the transformer which has a condenser in series therewith, there is an increase in the flux density of the core because the magneto-motive force of the lead reactor is in phase with the magnetomotive force produced by the transformer primary resulting in a tendency of the iron core adjacent the leading reactor to become saturated. As well-known, the efiect of saturation upon the core of an electromagnetic device is to destroy the linear relation between voltage and current with a result that the current in the leading coil of prior devices had a tendency to vary from sinusoidal. As pointed out, this resulted in decreased lighting eificiency of the fluorescent tube lamps. One manner of alleviating this diiiiculty was to provide a construction known as the brick.type of transformer. Such a construction consisted of a complete auto-transformer including a closed magnetic circuit with leading and lagging chokes at opposite ends thereof mounted for example upon E-shaped cores with the free ends of the cores arranged pointing towards the respective ends of the auto-transformer core. Thus the magnetic end members of the autotransformer core each served as a part of the magnetic circuit of the respective chokes.

The brick type of transformer resulted in satisfactory current wave forms in the leading reactor because little or no voltage was induced in the leading reactor by the auto-transformer. The brick type of transformer was expensive because of the necessity of providin a complete auto-transformer in the center of the assembly, including a secondary winding therefor, in order to achieve the open circuit voltage required to initiate the striking of the arcs in the lamps. Other factors made the brick type expensive, such as for example increased labor costs, the necessity for clamping the parts together, and the increased cost of the additional wire. Notwithstanding the production of satisfactory wave form by reason of elimination of saturation, the brick type of transformer was heavy, and had relatively large volume.

It is another object of my invention to achieve all of the benefits of a "brick type transformer with none of its disadvantages, namely by providing good wave form, decreased weight and size and greater economy.

I recognize that others have made attempts to achieve the ends set forth in the above objects, but certain reasons have made my invention advantageous over prior constructions. I have especial reference to a construction described in United States Letters Patent issued to George B. Horn, No. 2,241,261 dated May 6, 1941 and to another construction described in United States Letters Patent issued to Paul Berger, No. 2,461,957 dated February 15, 1949. In these patents there are described auto-transformers of the leaky type, i. e., having high leakage reactances. In the Horn construction, the primary of the auto-transformer is mounted upon the center of a closed magnetic circuit, such as for example formed as a closed elongate rectangular core, and the leading and lagging reactors form the secondaries oi the transformer, are connected in parallel and positioned on opposite side of the primary, at the ends of the core. Not only does Horn achieve the objective of attaining a satisfactory open circuit voltasc. but as well, inter-reaction between the leading and lagging reactors is prevented whereby in case one lamp is operating and the second lamp is connected into the circuit, the resulting leakage reactance will not have adverse effect in possible extinguishment of the first lamp. A great disadvantage of the Horn construction was in that the magnetizing fluxes of the primary and the leading reactor, which is actually one of the secondaries, thread the identical portions of the core and combine to result in at least partial saturation of the iron in the vicinity of the leading secondary. Obviously this results in destruction of the desirable sinusoidal wave form of the current in the leading secondary with consequent impairment of lighting eiiiciency in the fluorescent tube connected in series therewith.

The Berger construction corrected the principal defect of the Horn constructed by providing high reluctance means in the common magnetic circuit of primary and leading secondary in the form of a non-magnetic gap, thereby decreasing the flux density in the iron core thereat, and eliminating the tendency towards saturation. The resulting wave shape was more nearly sinusoidal, thereby giving increased lighting efficiency in the manner heretofore explained.

Again, certain disadvantages were engendered by the Berger construction, which it is desired to alleviate by my invention. These arise when it is desired to use a transformer of this type (wherein the leading and lagging reactors of a given arrangement are actually the secondaries of an auto-transformer the primary of which is mounted upon the same iron core mounting said secondaries) for the generation of high voltages in order to ignite instant-start lamps. These lamps need much higher voltages for ignition than are required by the ordinary pre-heated filament type which use the well-known thermostatic starting switches. Under such conditions, 1. e., with higher volt-ampere output, it is advantageous to decrease the number of primary turns to eliminate as much as possible the attendant increase in copper losses which adversely affect overall efficiency. The magnetic field required to produce a given open circuit voltage is dependent upon the magneto-motive force produced by the primary, and in order to attain such a field it is necessary to increase the magnetizing current to compensate forthe decrease in turns (since magneto-motive force is directly proportional to the number of turns and the magnetizing current). In the Berger type of construction, the added reluctance of the gap in the magnetic circuit of the primary penalizes any efforts to increase the cross sectional area and decrease the turns in order to achieve the higher voltages because there is necessitated an increase in the primary current. Thus there is a large reactive current in the primary which serves no useful end and may even overload the primary.

Accordingly, it is a further important object of my invention to eliminate this great disadvantage by providing a construction in which the gap in the primary circuit is materially decreased and even eliminated in order that the transformer can be constructed having relatively larger cross sectional core area without the attendant reduction in efficiency and increase in the primary losses. and without the danger of overloading the primary.

Many of the objects of my invention and the advantages thereof are achieved by so arranging the coils of the transformer as to cause the flux from the lagging reactor or secondary to oppose the flux from the leading reactor or secondary to prevent saturation, thereby eliminating the need for a relatively large non-magnetic gap and its attendant difficulties.

Other important objects and advantages of the invention are achieved by providing a construction which prevents saturation in the event that one of the lamps becomes extinguished destroying the flux balance described above. This is achieved in a manner to be described in detail in which a portion of the leading secondary is mounted in reinforcing relationship to the lagging secondary, such as for example by winding same upon the lagging secondary so ..s to utilize the identical magnetic circuit.

Other objects flow from the invention as will become obvious, and in particular great economy is achieved by a decrease in the overall amount of wire andiron used than ordinarily would be necessary.

In the drawings which illustrate preferred embodiments of my invention:

Fig. 1 is a schematic view of a brick type transformer showing the association of parts thereof.

Fig. 2 is a circuit diagram showing the manner of connecting the brick type transformer into a fluorescent tube lighting circuit.

Fig. 3 is a schematic view of a transformer showing the association of the parts thereof, said transformer being constructed in accordance with my invention but without the bucking coil.

Fig. 4 is a circuit diagram showing the manner of connecting the transformer of Fig. 3 into a fluorescent tube lighting circuit.

Fig. 5 is a schematic view of a transformer showing the association of the parts thereof, said transformer being constructed in accordance with my invention using a bucking leading coil.

Fig. 6 is a circuit diagram showing the manner of connecting the transformer of Fig. 5 into a fluorescent tube lighting circuit.

In order best to describe my invention I have shown the brick type of transformer in Figs. 1 and 2 of the drawings and pointed out the advantages of my invention thereover. The reference character In designates generally the brick" type transformer, same comprising a centrally positioned auto-transformer ll having a primary coil l2 and a secondary coil I! mounted upon the elongate iron core Id. The auto-transformer I l is arranged within a completely closed magnetic circuit comprising top leg 15, bottom leg I6, and side legs I! and I8, there being a central winding leg I! as well. At the right end of the core H the lead reactor 20 is positioned upon an E-shaped core 2| whose leg ends abut the side leg 18, while at the left end of the core H the lagging reactor 22 is positioned upon an E-shaped core 23 having its leg ends abutting against the side leg l1. Non-magnetic gaps 21 and 28 provide essentially linear characteristics for reactances 20 and 22.

The lead reactor 20 does not readily saturate its core 2| because the voltage induced by the auto-transformer ll therein is extremely low due to the non-magnetic gap 28 and leg ll. Consequently, the wave shape of the current in the lead reactor approaches sinusoidal formation. As will be noted in Fig. 2, the primary I2 of the auto-transformer H is connected across a source of voltage; the reactors 2. and 22 are connected in parallel to the secondary l2; the reactor 20 is connected in series with a condenser 24 and a lamp 25 to one side of the line; and the reactor 22 is connected to a second lamp 26 to the same side of the line. Each of 'the lamps 25 and 26 is provided. with a conventional starter switch S in parallel circuit, same being ordinary preheated fllament type lamps.

Considering the brick type of transformer, note that the core I4 is formed of a plurality of parts which must be held together by some type of clamping means not shown in Fig. 1. Note also that the auto-transformer is a complete element including a secondary l3. The overall device requires a greater amount of copper and iron than one constructed in accordance with my invention. Initially it may be mentioned that a "brick" type transformer constructed to produce the voltages required for instant-start lamps will weigh approximately 21 pounds to supply two 96" T 12 lamps at .425 amp. (where the line voltage is 110) and a comparative transformer constructed in accordance with my invention will weigh between 12 and 15 pounds.

In Fig. 3 I have shown a simple form of my invention which comprises a transformer designated generally as 30. There is an outer shell core 3| having central inwardly extending legs 32 and 33 on opposite sides thereof and having an elongate central winding leg 34 the ends of which abut against the ends 35 and 36 of the shell 3|. The legs 3| and 32 do not abut against the sides of the winding leg 34 but are spaced therefrom in order to provide non-magnetic gaps 31 and 38 which may be filled with cement, fibre, or other non-magnetic material in order to prevent vibratory noise caused by the magnetic flux pulling at the gaps.

At the left end of the transformer 30 there is provided a winding 39 which is connected as the primary of an auto-transformer. In the center of the transformer 30 there is provided a secondary winding 40 and at the right end there is another secondary winding 4|. The winding 40 is connected in series with a condenser 42 and hence comprises the lead secondary. Both secondaries are connected to one side of the primary 39 which is connected across the line. The secondaries are thus in parallel and each is connected to alamp as shown at 43 and 44 which in turn are connected to the second side of the line. It should be noted that no switches are shown in connection with the lamps 43 and 64 since it is intended that the transformer 33 will provide a large initial voltage sufl'icient to ignite the lamps.

There is no gap in the primary as in the Berger construction and hence there is sufficient flux in the primary circuit to enable the generation of high voltages without great copper losses and high magnetizing current. Decreasing the primary turns can be offset by increasing the cross section of the core 3|, which actually has been done.

Considering the flux in the transformer 30, note that the lead secondary and the primary produce fluxes that have large components that are reinforcing, i. e., in the same direction, while the reactive component of the flux of the lag secondary 4| is in opposite direction. The bucking effect of the flux of the secondary 4i reduces the effect of the flux of the lead secondary 40 and prevents primary flux traveling the entire magnetic circuit (not shown) from reinforcing the lead flux so as to cause bad wave shape.

Proper proportioning of the gaps 31 and 33 and adjustment of the cross sectional area of the legs 32 and 33 will result in excellent wave shape of the secondary currents. It can be said that the two secondaries are arranged side by side in bucking relationship so as to balance any tendency of the flux from either, when combined with the primary flux, to saturate any part of the iron core, thereby giving good wave shape.

The above construction is quite satisfactory so long as both lamps 43 and 44 are operating. If either of the lamps becomes inoperative, however, the flux balance is upset, and there may be a saturation condition which will not give the remaining lamp suflicient light producing current to render the same effective.

Let us presume that the lag lamp 44 becomes extinguished and inoperative. The bucking flux of the lag secondary 4| is now no longer present and the lead secondary flux is reinforced to a great extent by the flux of the primary 39 producing saturation of the core 3| adjacent the secondary ill.

In the event that the lead lamp 43 becomes extinguished, there is a considerable drop in the magneto-motive force tending to maintain the voltage on the lag lamp and there is a drop in the current of the lag secondary caused by an increase in the reactance of the lag secondary. This decreases the light output of the lamp 4, and while it is beneficial since it does not tend to overload the primary, nevertheless it is unsatisfactory, be-

cause it is desired that the lamp 44 maintain its brilliance in the event that lamp 43 is extinguished.

The form of my invention shown in Figs 3 and 4 provides the necessary requirements for a high voltage transformer under normal conditions by the expedient of causing the flux from the two secondaries to balance one another for maintaining low flux density in the transformer core Under abnormal conditions, however, no provision has been made to provide for an upset of the balance caused by the extinguishment of one of the lamps 43 or M In Figs. 5 and 6 I have shown a refinement of my invention which does compensate for abnormal changes.

The transformer 50 includes an outer shell 5| having center inwardly extending legs 52 and 53,

a central winding leg 54, end portions 55 and 55, and gaps 51 and 58. At the left end there is provided an auto-transformer 59 which consists of a primary winding 60 and a relatively small secondary winding Bl. In the center of the transformer so there is provided the lead secondary 62, but all of the lead secondary is not wound upon leg 55 in the center. A small portion of the lead secondary is wound in reverse relationship on the right hand end of the transformer as shown at 63, and the lag secondary 64 is provided at the same position. The relation between transformer 59 and the secondaries 62 and 64 is identical with the relation between primary 39 and secondaries 4i] and ll of Figs. 3 and 4. The flux from the transformer 59 and the secondary 62 are reinforced and are together bucked by the flux of secondary B4. In addition, however, the lead secondary flux is bucked by flux from a. portion of its own winding, namely by the flux from bucking lead secondary 63.

The effect of the bucking lead secondary is as follows:

Since the flux of secondary 63 is in phase with the flux of the secondary 64, it serves to increase the reactance of the lagging secondary 64 and arcane thus decrease the operating current of said secondary N, when both lamps, shown at BI and II, are in operation. Any change in current which might be occasioned by the lead lamp is becoming extinguished will be compensated for by use of proper proportion of leading secondary coils. In other words, the transformer is constructed so that the balance described in connection with the embodiments of Figs. 3 and 4 is maintained at leastin part by reason of the bucking lead seconddry 83. The drop in magneto-motive force of the secondary 62 when lamp 66 becomes extinguished, is neutralized by the drop in magneto-motive force of secondary 63, opposite in direction, at the same time. The net effect is a minimum or, if desired, can be adjusted so that there is a small drop in the current of secondary 84 so as not to overoad the transformer primary 60 if lamp 88 becomes extinguished, or if desired by over compensation the current in lamp 65 may actually be increased.

Obviously, in the event that lamp 65 becomes extinguished, the bucking lead secondary 63 maintains opposing flux serving to prevent saturation of the core 5| in the same manner as described in connection with the constructions of Figs. 3 and 4. There is a magneto-motive force produced opposing that of the lead secondary 62 by its own reverse wound section 83.

The above described construction thus provides balance, irrespective of which lamp becomes extinguished, and hence, not only enables the transformer 50 to be used with high voltage, but also preserves satisfactory wave form under practically all conditions.

By reason of my construction, certain variations from ordinary, can be made in circuit constants, which gives rise to economy in construction as well as efiiciency in operation. It is ad vantageous to lower the inductance of the lead secondary 62 in order to adjust the flux balance. This decrease of inductance must be balanced, from a power factor correction standpoint, by a corresponding increase in the capacitance of condenser Bl. The voltage drop now appearing across the condenser 61 is lower, hence a lower voltage rate and cheaper condenser can be used.

Another effect of lowering the inductance of the lead secondary 62 is a drop in open-circuit, or ignition voltage. This condition can be alleviated by adding a few windings to the primary 60 in auto-transformer relationship giving rise to the closely coupled secondary 6|.

It was found that the lagging secondary 64 could be adjusted for proper open circuit voltage and current by removing turns from the lagging secondary and adding them to the closely coupled secondary 6|, or vice-versa.

It is desired at this point to emphasize that the use of a closely coupled secondary 6| is a refinement to my construction. Transformers can be constructed in accordance with my invention without the use thereof. I have found, however, that the use of such a secondary enables the elimination of much copper and iron because, within certain limits, each turn of the closely coupled secondary 6| corresponds to a turn on each of the lag and lead secondaries, and in addition the wire of the closely coupled secondaries can be made finer than the wire of either secondary 62 or 64 because the out of phase currents from lag and lead secondaries correct one another to lower the effective current in said closely coupled secondary.

A limiting factor in the substitution of lag and 8 lead secondary turns for closely coupled secondary turns is preservation of amount of inductance in the secondaries to retain good wave shape, and properly limit the operating current after ignition of the lamps.

It will be noted that the legs 52 are considerably narrower than the legs 53. This has been found to be an advantageous expedient for forcing the flux from the primary 60 to induce the necessary currents in the lagging and leading secondaries without sacrificing wave shape or without using a wider gap at 51 which would give rise to noise. By spacing coils 59 and I2 sufficiently far apart the same effect can be achieved but with increase in the possibility of noise and additional steel required.

It will be seen that the embodiment of my invention shown in Figs. 5 and 6 and described in connection with said figures, comprises an elongate iron core having a primary winding at one end, a central lead secondary winding, a lag secondary winding at the end opposite the primary, and a bucking lead secondary connected in series with the lead secondary and wound in reverse relationship and closely coupled with the lag secondary so that the fiux therefrom bucks that of the lead secondary and reinforces that of the lag secondary. There are inwardly directed extensions of the core between the primary and lead secondary and between the lead secondary and lag secondary, and non-magnetic gaps in the extensions, or other means providing loose coupling can be used. Refinements of the construction comprise a closely coupled auto-transformer winding in connection with the primary, and the extension between the primary and lead secondary being relatively narrow. In operation, transformer constants are adjusted so that there is a flux balance between lag and lead secondaries not readily upset by extinguishment of either lead or lag lamp.

I have constructed successful embodiments of my invention and by way of example, I have described hereinafter a transformer of the type shown in Figs. 5 and 6 and intended to ignite and operate two' 96 inch long instant-start fluorescent lamps, known in the trade as T-12's, and a current of .425 amp. from a volt A. C. line. The shell 5| was approximately 7 inches by 3 inches, the central winding leg 54 was approximately one inch wide; and the peripheral frame of the shell 5| was slightly less than onehalf inch wide. The legs 52 were .175 inch wide, while the legs 53 were .738 inch wide. The gaps 51 and 58 were .035 inch and .060 inch respectively. The winding openings were approximately 2 inches in length for the end windings and approximately l inches for the central winding opening. I found that once I had arrived at a satisfactory lamination configuration, same could be used for different examples of the same general type of lamp merely by changing the height of stack, and making appropriate changes in the windings. For the lamps referred to, the stack was made 1% inches high.

As for the windings, the primary 60 comprised 357 turns of number 20 wire; the closely coupled secondary 6| comprised 690 turns of number 27 wire; the lead secondary 62 comprised 1520 turns of number 27 wire; the bucking lead secondary 63 comprised 500 turns of number 27 wire; the lag secondary comprised 1314 turns of number 27 wire. The usual and well-known insulating means, cannister, pitch, etc., were used in assembly. along with a 1.25 microfarad condenser decreased from normal.

8| rated at 925 volts and connected in series with bucking lead secondary 63,

The above described example gave excellent results, both as to cool operation as well as electrical performance. The brilliance of either lamp operating alone was in no perceptible way While certain theories have been used to explain the results achieved, it is' desired to point out that such explanations have been made with a view towards assisting in an understanding hereof and not by way of limitations.

I claim:

A transformer for operating a, plurality of separately operable gaseous discharge devices and supplying the same with relatively high ignition voltages and leading and lagging currents respectively, comprising an elongate core having a primary winding at one end, a lead secondary winding upon said core next to the primary winding and loosely coupled thereto and adapted to be connected in series with a capacitive reactance to supply a leading current to one of said devices, and a lag secondary upon said core'next to the lead secondary but loosely coupled thereto, and mounted upon the end of the core opposite to the primary, and adapted to be connected with a second of said devices and supply a lagging current thereto, both of said secondaries being connected to the primary in autotransformer relationship, and a bucking lead secondary connected in series with said lead secondary and being closely coupled with the lag secondary and wound in reverse relationship to the lead secondary to cause the flux thereof to reinforce the flux produced by the lag secondary.

2. A transformer for operating a plurality of separately operable gaseous discharge devices and supplying the same with relatively high ignition voltages and leading and lagging currents respectively, comprising an elongate core having a primary winding at one end, said core providing a magnetically uninterrupted path for flux from said primary throughout the-length thereof, a lead secondary winding upon said core next to the primary winding and loosely coupled thereto and adapted to be connected in series with a capacitive reactance to supply a leading current to one of said devices, and a lag secondary upon said core next to the lead secondary but loosely coupled thereto, and mounted upon the end of the core opposite to the primary, and adapted to be connected with a second of said devices and supply a lagging current thereto, both of said secondaries being connected to the primary in autotransformer relationship, and a bucking lead secondary connected in series with said lead secondary and being closely coupled with the lag secondary and wound in reverse relationship to the lead secondary to cause the flux thereof to reinforce the flux produced by the lag secondary, the secondaries being constructed to provide a flux balance in the core during the operation of said gaseous discharge devices to provide a good wave form in the currents supplied to said devices, and being arranged to preserve substantially flux balance in the event of extinguishment of either of said devices.

3. A transformer for operating a plurality of separately operable gaseous discharge devices and supplying the same with relatively high ignition voltages and leading and lagging currents respectively, comprising an elongate core having a primary winding at one end, said core providing a magnetically uninterrupted path for flux from said primary throughout the length thereof, a, lead secondary winding upon said core next to the primary winding and loosely coupled thereto and adapted to be connected in series with a capacitive reactance to supply a leading current to one of said devices, and a lag secondary upon said core next to the lead secondary but loosely coupled thereto, and mounted upon the end of the core opposite to the primary, and adapted to be connected with a sec- 0nd of said devices and supply a, lagging current thereto, both of said secondaries being connected to the primary in autotransformer relationship, and a bucking lead secondary connected in series with said lead secondary and wound in reverse relationship to the lead secondary to cause the flux thereof to reinforce the flux produced by the lag secondary, there being a magnetic shunt between the primary winding and the lead secondary, and another such shunt between the lead secondary and the lag secondary.

4. A transformer for operating a plurality of separately operable gaseous discharge devices and supplying the same with relatively high ignition voltages and leading and lagging currents respectively, comprising an elongate core having a primary winding at one end, said core providing a magnetically uninterrupted path for flux from said primary throughout the length thereof, a lead secondary winding upon said core next to the primary winding and loosely coupled thereto and adapted to be connected in series with a capacitive reactance to supply a leading current to one of said devices, and a lag secondary upon said core next to the lead secondary but loosely coupled thereto, and mounted upon the end of the core opposite to the primary, and adapted to be connected with a second of said devices and supply a lagging current thereto, both of said secondaries being connected to the primary in autotransformer relationship, and a bucking lead secondary connected in series with said lead secondary and wound in reverse relationship to the lead secondary to cause the flux thereof to reinforce the flux produced by the lag secondary, there being a magnetic shunt between the primary winding and the lead secondary, and another such shunt between the lead secondary and the lag secondary, the bucking lead secondary being disposed upon the same side of said last mentioned shunt as said lag secondary.

5. A transformer for operating a plurality of separately operable gaseous discharge devices and supplying the same with relatively high ignition voltages and leading and lagging currents respectively, comprising an elongate core having a primary winding at one end, said core providing a magnetically uninterrupted path for flux from said primary throughout the length thereof, a lead secondary winding upon said core next to the primary winding and loosely coupled thereto and adapted to be connected in series with a capacitive reactance to supply a leading current to one of said devices, and a lag secondary upon said core next to the lead secondary but loosely coupled thereto, and mounted upon the end of the core opposite to the primary, and adapted to be connected with a second of said devices and supply a lagging current thereto, both of said 4 secondaries being connected to the primary in ondary and wound in reverse relationship to the lead secondary to cause the flux thereof to reinforce the flux produced by the lag secondary, there being a magnetic shunt between the primary winding and the lead secondary, and another such shunt between the lead secondary and the lag secondary, the shunt between the windings com prising extensions of the core and each having a non-magnetic gap therein.

6. A transformer for operating a plurality of separately operable gaseous discharge devices and supplying the same with relatively high ignition voltages and leading and lag ing currents respectively, comprising an elongate core having a primary winding at one end, said core providing a magnetically uninterrupted path for flux from said primary throughout the length thereof, a lead secondary winding upon said core next to the primary winding and loosely coupled thereto and adapted to be" connected in series with a capacitive reactance to supply a leading current to one of said devices, and a lag secondary upon said core next to the lead secondary but loosely coupled thereto, and mounted upon the end of the core opposite to the primary, and adapted to be connected with a second of said devices and supply a lagging current thereto, both of said secondaries being connected to the primary in autotransformer relationship, and a bucking lead secondary connected in series with said lead secondary and wound in reverse relationship to the lead secondary to cause the flux thereof to reinforce the flux produced by the lag secondary, there being a magnetic shunt between the primary winding and the lead secondary, and another such shunt between the lead secondary and the lag secondary, the shunt between the windings comprising extensions of the core and each having a non-magnetic gap therein, the shunt between the lead secondary and the primary winding having substantially one fourth the area of that between the secondaries.

7. Apparatus for supplying a high ignition voltage to a pair of separately operable fluorescent lamps and for supplying a lagging and leading 40 current respectively to said lamps, and comprising a transformer including an elongate iron core having a primary winding at one end thereof, a

central lead secondary winding adapted to supply the leading current to one of the lamps, and a lag secondary winding at the end opposite the primary and adapted to supply a lagging current to the second of said lamps, a bucking lead secondary connected in series with the lead secondary and wound in reverse relationship thereto and closely coupled with the lag secondary so that the flux therefrom bucks that of the lead secondary and reinforces that of the lag secondary, said secondaries being connected in autotransformer relationship with the primary, said primary having a closely coupled secondary for increasing the open-circuit voltage produced by said transformer, and said lag and lead secondaries being comiected in series therewith.

- 8. Apparatus for supplying a high ignition voltage to a pair of separately operable fluorescent lamps and for supp y ng a lagging and leading current respectively to said lamps, and comprising a transformer including an elongate iron core having a primary winding at one end thereof, a central lead secondary winding adapted to supply the leading current to one of the lamps, and a lag secondary winding at the end opposite the primary and adapted to supply a lagging current to the second of said lamps, a bucking lead secondary connected in series with the lead secondary and wound in reverse relationship thereto and closely coupled with the lag secondary so that the flux therefrom bucks that of the lead secondary and reinforces that of the lag secondary, said secondaries being connected in autotransformer relationship with the primary, said primary having a closely coupled secondary supplying substantially one-half of the total opencircuit voltage producedby said transformer.

ALBERT E. FEDIBERG.

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

UNITED STATES PATENTS Number Name Date 2,352,073 Boucher et a1 June 20, 1944 2,382,638 Keiser et al. Aug. 14, 1945 2,404,254 Short July 16, 1946

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