US2940008A

US2940008A - Transformer for electrical discharge lamps

Info

Publication number: US2940008A
Application number: US816344A
Authority: US
Inventors: Jeanne E Strecker
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1959-05-27
Filing date: 1959-05-27
Publication date: 1960-06-07
Anticipated expiration: 1977-06-07

Description

June 7, 1960 c. E. STRECKER 2,940,008

TRANSFORMER FOR ELECTRICAL DISCHARGE LAMPS Filed May 27, 1959 United States Patent TRANSFORMER FOR ELECTRICAL DISCHARGE LAMPS late of Danville, Ill., b' executrix, Danville, Ill., assignor Company, a corporation of New Filed May 27, 1959, Ser. No. 816,344

11 Claims. (Cl. 315-97) This invention relates to electric discharge lamps and more particularly to ballast transformer apparatus for starting and operating such lamps.

It is a characteristic of electric discharge lamps, such as fluorescent lamps, that their internal resistance decreases as the current flow therethrough increases. It is, therefore, necessary in the installation of such devices to provide means which will limit the current flow through the device to, a desired value. In addition, it may also be desirable to provide a higher voltage for initially starting or causing a discharge in the device than is conveniently available. When electric discharge devices are operated on alternating current, it is conventional practice to provide a single high reactance ballast transformer to perform these two functions, i.e., current limiting and the provision of a high initial starting voltage. Such a transformer provides a high open circuit voltage for starting and also, byvirtue of its high reactance, provides impedance during normal operation to limit the current flow.

A high reactance transformer is one in which the primary and secondary windings are loosely coupled so that when the transformer is carrying load, there is a substantial amount of leakage flux and the voltages induced in the windings by this leakage flux cause the transformer to have a relative high effective series reactance, or what is commonly known as leakage reactance. The conventional way of constructing such a transformer is to arrange the primary and secondary windings on different parts of the magnetic core and to provide a magnetic shunt between the windings there? by providing a path for the leakage flux. This magnetic shunt is usually provided with an air gap so calibrated that the operating current of the secondary winding of the transformer will be limited to the desired value.

In co-pending application Serial No. 435,753, filed June 10, 1954, and assigned to the same assignee as the present invention, there is disclosed a ballasting transformer where a high starting voltage is achieved in a starting aid potential circuit by using the transformer windings connected as an autotransformer, i.e., the primary winding and the secondary windings are connected in series during starting so that their voltages are additive in an auxiliary starting aid potential circuit. This apparatus has proved successful'in actual practice, but it is sometimes desirable to use a higher starting voltage than is available by the additive voltages of the primary and the secondary windings alone.

It is, therefore, an object of this invention to provide an improved apparatus for starting and operating discharge lamps which will achieve relative high starting voltage for starting electric discharge lamps and which will thereafter operate the lamps at a lower voltage.

Another object is to provide a ballast transformer apparatus for starting a pair of serially connected lamps at high voltage and thereafter operating the lamps at a lower voltage,

Further objects and advantages of this invention will 2 become apparent and the invention will be better understood by reference to the following description and the accompanying drawings, and the features of novelty which characterize this invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

This invention,.in one embodiment thereof, includes a ballast transformer having a primary winding, a first or auxiliary starting secondary winding, and a second or operating secondary winding, all connected in a series circuit in autotransformer relationship so that their voltages are additive. Circuit means are provided for connecting the operating secondary winding across the discharge lamp .or lamps to be operated by the transformer. The additive voltages of the primary, the auxiliary starting secondary, and the operating secondary windings will be applied to one of 'the electrodes of each of the lamps in a starting aid potential circuit. The lamp or lamps are in capacitive relation to a conducting part or fixture grounded to the low potential side of the supply line as a starting aid. As is well-known, a fairly small current will flow from this high potential electrode of each lamp to the fixture, and the small current will bring about ionization in the area about the electrode. The increased ionization, which may be in cooperation with the heating of the electrodes, will cause a breakdown of the gas contained within the lamp. In a single lamp circuit the lamp will then start, and in a multiple circuit, first one lamp and then the other will start. Once the lamp or lamps start, the transformer will function substantially as an ordinary isolated secondary transformer rather than as an autotransformer. Due to the high impedance between the lamp and the fixture, the main part of the operating current will pass through the lamps and the operating secondary in closed circuit and the current from the lamp to the fixture will be minor with respect to the current through the lamps.

As explained thus far, the described circuit has a low power factor, drawing a lagging current through the transformer. The improvements herein described may be applied to a transformer drawing leading current or having near unity power factor by proper connection of power capacitors in the system as is well-known in the art.

It will be seen that by using the output of the primary, the auxiliary starting secondary and the operating secondary additively to start the lamps, the operating secondary of the transformer may be made smaller since the output voltage therefrom need not be as great. Also, the auxiliary secondary winding may be made of extremely fine wire since it carries no operating current; the auxiliary starting winding may, if desired, have a relatively high impedance and thereby act to limit the flow of current in the starting circuit in the event that a person handling the device accidentally comes in contact with the high voltage line and an electrode of the lamp or ground. The danger of a person receiving a lethal shock is eliminated when a sufiiciently high impedance is in the starting aid potential circuit to materially limit the current flow therethrough. The auxiliary starting secondary may be tightly coupled to either the primary winding or the secondary winding. Due to the high impedance between the lamp electrode and fixture, the autotransformer connection of the primary winding, the auxiliary starting secondary winding, and the operating secondary winding is not effective after starting to make. the voltages of the windings additive; but the transformer functions as a substantially isolated secondary during running of the lamps.

' In the drawing, Fig. 1 is a schematic diagram of an proved transformer for a discharge lamp according to, the instant invention;

Fig. 2 is a circuit similar to that shown in Fig. 1 but showing an equivalent connection of the low potential end of the primary with the lamp fixture;

Fig. 3 is a schematic diagram of a transformer for operating a pair of serially connected discharge lamps; and, v

Fig. 4 is a plan view of a ballast transformer apparatus according to the instant invention.

Referring to Figs. 1 and 4, there is illustrated the improved ballast transformer apparatus according to the instant invention for operating a s'ingledischa'rge lamp. The transformer apparatus includes a magnetic iron core 1 within a transformer case or housing 2. The core 1 includes a central Winding leg 3 and yokes 4 and 5. Disposed on the central winding leg 3 is a primary winding P, anauxiliary starting secondary winding S and an operating secondary winding S A pair of leads 6, 7 are connected to the primary for connection to a source of alternating current voltage 8, 9. As hereinafter explained, the low potential side 8 of the supply voltage is normally, but not necessarily, grounded as shown by ground 10. The low potential side of the starting secondary S is connected to the high potential side of the primary P in autotransformer relationship; the high potential side of the auxiliary starting secondary S is connected to the low potential side of the operating secondary S in autotransformer relationship. The primary P, starting secondary S and operating secondary S are, all connected in voltage adding relation.

The operating secondary S' is loosely coupled with the primary P by being spaced in sideby-s'ide relation therewith, and by the inclusion of high reluctance flux leakage paths within the core between the primary P and the foperating secondary S In other words, the transformer has high magnetic leakage between the windings and may be termed a high reactance ballast transformer. It will be understood that, depending upon the design of the transformer, the flux leakage paths or shunts may be formed either through non-magnetic material such as air, or through magnetic material as by the provision of the projecting shunt legs 11 formed on the core. It will be noted that there are gaps between the ends of the shunt legs 11 and the center leg 3 to provide high reluctance in the leakage paths of the illustrated transformer.

The auxiliary secondary winding S may be tightly coupledwith one of the other windings; as shown in Fig. 1, the starting secondary S 'is tightly coupled with the primary winding P, being wound over it. It will be understood, however, that secondary winding S could be placed closely beside one of the other windings with little fiux leakage therebetween in order to obtain the desired close coupling. End portions or extension windings 12, 13 at the respective ends of the operating secondary S form cathode heating windings. It is to be understood, however, that the cathode heating windings may be isolated windings on the same part of the core as either the primary or secondary windings.

A The operating secondary S has electrical circuit means for connection across the discharge lamp L. The lamp L, as described above, has cathodes or

electrodes

14, 15 in its respective ends. The'circuit means connecting the operating secondary S across the lamp L includes a first pair of output leads 16, 17 connecting the first cathode heating extension winding 12 across electrode 14; and a second pair of output leads 18, 19 connecting the second cathode heating extension winding 13 across the second electrode 15 of the lamp L.

The lamp L is in a conductive fixture 20 which, as hereinafter explained, is normally grounded through ground 21. This places the conductive fixture 20 in electrical circuit with the grounded low potential line .8 of the supply source. The conductive lamp L in close proximity to the'conducting fixture .20 resulfs'in acap'a'citive coupling of the lamp and fixture thereby completing a high impedance electrical circuit from the lamp to the fixture. It may be desirable, but not necessary, to ground the low potential side of the input line 6 to the ballast case 2 through a high ohmage resistor 22. The transformer case 2 is normally grounded through ground 23 to the conductive fixture, this connection assuring grounding of the low potential line Swith the conducting fixture thereby to complete an electrical circuit therewith.

With the above transformer structure in mind, the operation of the transformer vw'll now be described. When lines 6 and 7 are connected across the source of alternating currentvoltage 8, 9, the current will flow through the primary P so as to excite the auxiliary starting secondary S and the operating secondary S The open circuit voltage resulting in the starting secondary S and the operating secondary S will be a function of the number of turns of each secondary with respect to the number of turns of the primary P. The open circuit voltages produced in the starting secondary S and operating secondary S will be added to the voltage across the primary P due to the autotransformer connections therebetween. There will, therefore, be a relatively high voltage applied to electrode 14 of the lamp L with reference to the grounded low potential supply line 8 and grounded fixture 20. As fixture 20 is arranged to act with electrode 14 as a capacitor, a relatively small current will pass therebetween' due to the relatively high voltage which exists between the lamp L and the fixture 20. The current will preferably be in the order of a few microamperes which is sufficient to increase substantially the ionization of the gas within the lamp L around the electrode 14. The circuit is completed through the fixture 20, as previously explained, through the ground. During this time,

electrodes

14 and 15 are both being heated as a'result of the extension windings 12, 1-3. It may also be possible to omit these winding sections and provide cold cathode starting arrangements, as is well-known in the art. The heating of electrodes. 14 and 15 and the I ionization of the gas around electrode 14 will break down the gas and the lamp L and the current will arc across the electrodes to start the lamp.

Once the circuit has been completed between

electrodes

14 and 15, the lamp L will be kept in operation by the voltage of {the operating secondary S which will be in a closed series circuit with the lamp L. This occurs because af er the completion of the circuit across the electrodes, due to the high impedance between the lamp L and fixture 20, "the amount of current between electrode 14 and fixture 20 becomes minor with relation to the current between

electrodes

14 and 15. Consequently, the balla'st'transformer apparatus will, for practical purposes, act as an ordinary high reactance isolated secondary transform-er withthe operating secondary S being'excited by the primary P to provide sufiicient current to keep the lamp L in operation. The secondary voltage induced in the operating secondary S will drop, out: the arc is struck between

electrodes

14 and 15, to diminish even further the current flow through the fixture 20. The current flow in the starting aid circuit may be further decreased by the inclusion of a high resistance between the primary. winding P and the operating secondary S as more fully described in my aforesaid co-pendi'ng application. a

The inclusion 'of the starting secondary S has the effeet "of producing a high starting-voltage in the starting air loop but since the current flow between electrode 14 and'the fixture 26 becomes infinitesimal with relation to the current in the operating loop (including the lamp and the operating secondary S the starting secondary S issubstantially inoperative in the operating condition.

It will be seen from the foregoing that this circuit provides a high voltage for the starting of lamp L by connecting the "primary P, the auxiliary-starting'secondary S and the operating secondary S inautotrans former relationship withtheir voltages additive and applied to the lamp during starting thereof. The circuitry provided assures that the autotransformer connection between the operating secondary S and the primary P through the startring secondary S will cease to be effective once the lamp L has started.

The embodiment of 'Fig. 2 is similar to that of Fig. 1 except an equivalent electrtical circuit is used instead of the grounding of an input line and the grounding of the conducting fixture. Like numerals are used for parts which correspond to parts described in Fig. 1.

Normal residential and commercial distribution systems in this country have the low potential side of the supply line grounded. Moreover, it is customary to ground the conductive fixture which holds the lamp in capacitive relation. In such a system, the conductive fixture is in electric circuit with the low potential side of the supply line through the ground. However, in the event that the line is opened on the grounded side and the line ground is not effective, or for distribution systems where the low potential side of the line is not grounded, or for instances where the fixture of the device will not be grounded, a ground may be provided from the low potential side of the line to the lamp fixture. In this manner, the conductive fixture is placed in electric circuit with the low potential side of the supply source. One convenient method of obtaining this connection is to connect the low potential side of the supply line to the transformer case; the transformer is normally mounted on the conducting fixture. In this manner the conducting fixture is connected in the electrical circuit to the low potential side of the supply line through the ballast case. It maybe desirable, but not necessary, to provide a high resistance in the line connecting the low potential side of the supply line with the transformer case. While such a high resistance would not carry any current in a normally grounded system, it will afford certain safety measures under the abnormal operating conditions described above.

Referring to Fig. 2, the main difference in the embodiment of Fig. 2 is the provision of a line 24 electrically connecting the conducting fixture with the low potential lead 6 of the primary P. As heretofore explained, a high resistance 22 may be inserted in the line to afford the aforementioned safety features. An electrical con nection is thereby assured between the conducting fixture 20 and the .low potential side of the supply source.

Fig. 3 illustrates schematically a modification of the instant ballast transformer apparatus for starting and opcrating a pair of serially connected discharge lamps. The

ballasting transformer includes a primary winding P, a starting secondary winding 8,, and an operating winding 8;, all on a magnetic core 1. As in the modification of Fig. 1, one end of the starting winding S is connected to one end of the primary P in autotransformer relationship therewith; the other end of the starting secondary S is connected to one end of the operating secondary S in autotransformer relationship therewith. The windings P, S and S are wound and connected in voltage adding relation. Leads 6, 7 extend from the primary winding P for connection to a source of alternating current supply lines 8, 9, one line 8 of which may be grounded, as shown, by ground 10. As explained above, the low potential line 6 may be grounded to the transformer case 2 through ground 23 by means of a high ohmage resistor 22. It is to be understood that, if desired, the high ohmage resistor 22 and grounding of the low potential side 6 to the transformer case may be omitted in a normally grounded line and fixture system.

The transformer isadapted to operate a pair of serially connected lamps, comprising first lamp L and second lamp L Each lamp has an electrode in each end thereof; lamp L has electrodes 25, 26 in its ends respectively; and lamp L, has'electrodes 27, 28 in its ends respectively. The lamps are in close proximity and therefore in capacitive relation to a conductive fixture 20. As heretofore described, the conductive fixture 20 would normally be grounded as shown by ground 21; however, it is to be understood that if either the conducting fixture 20 or the low potential line 8 of the supply source is not grounded, then the conducting fixture may otherwise be placed in circuit relationship with the low potential side of the supply source as illustrated, for example, in Fig. 2 above. Also wound on the magnetic core 1 are cathode heating windings 29, 30 and 31. A pair of output leads 32, 33 extend from cathode heating winding 29 for connection across cathode 27 of lamp L Another pair of output leads 34, 35 extend from cathode heating winding 30 for connection across cathode 28 of lamp 1., and cathode 25 of lamp L A thirdpair of output leads 36, 37 extend from cathode heating winding 31 for connection across cathode 26 of lamp L Means including electrical leads 38, 39 serially connect the operating secondary S in a series operating circuit including the serially connected lamp L L The loads 38, 39 extending from the secondary S have their other end connected to the output leads 32 and 36, respectively, which extend from the cathode heating windings 29 and 31. A starting capacitor 42 is connected across lamp L in parallel therewith, by connection across output leads 32 and 34 extending from cathode heating windings 29 and 30.

Having thus explained the structure and circuit of the ballasting transformer apparatus according to the modification of Fig. 3, the operation of the circuit will now be described. When lines 6, 7 are connected across the source of alternating current voltage, the current will flow through the primary P so as to excite the starting secondary S and the operating secondary S The open circuit voltages resulting in starting secondary S and operating secondary S will be a function of the number of turns of the respective secondaries with respect to the number of turns of the primary P. In addition to the open circuit voltage produced in the starting secondary S and the operating secondary 8;, the voltage across primary P will be added thereto due to the autotransformer connections of the primary, starting secondary S and operating secondary S Specifically, a starting loop is formed including the primary winding P, the starting secondary S the operating secondary S through lines 38, 40 starting capacitor 42, lines 41 and 34, through electrode 25 of lamp L to the conducting fixture 20 and through the ground to primary winding P. There Will, therefore, be a relative high voltage applied to the electrode 25 of lamp L with reference to the grounded fixture 20. Fixture 20, as heretofore described, is arranged to act with electrode 25 as a capacitor, and a relatively small current will pass therebetween due to the additive voltages of the primary P, the starting secondary S and the operating secondary S This current will preferably -be on the order of a few microamps, which is sufficient to increase substantially the ionization of the gas Within the lamp L around the electrode 25. The circuit is completed through the fixture 20 which, as previously explained,

is in circuit relation with the low potential side 8 of the supply line through grounds 21 and 10.

During this time, all the electrodes 25, 26, 27 and 28 are being heated as a result of the output of the cathode heating windings. The voltage in operating secondary S will appear across the electrodes 25, 26 of lamp L through lines 38, 40, starting capacitor 42, lines 41, 34, through lamp L and lines 36 and 39. Starting capacitor-42 is of sufficient capacitance to permit the passage. of the small'amount of starting current necessary. It is of sufficient impedance, however, to limit the current flow therethrough to a very low value during the operation of lamp L The heating of the electrodes 25, 26- and' the ionization of the gas around electrode 25..will- 7. break down the gas in lamp L adjacent electrode 25. With the voltage of S appliedacross L and with the starting aid, current will arc across between the electrodes to start the device. 4 Once lamp L has started, the combined voltage of the primary P," the starting secondary S and the operating secondary S are applied. through lines 38 and 32 to electrode 27 of lamp L Electrode, 27 of lamp L is in capacitive relation with the conducting fixture 20 whereby the gas around electrode 27 will be ionized. Simultaneously, 'a voltage is'applied across the electrodes of lamp L from S through the loop including the operating secondary S and, the first lamp L Lamp L will arc across the electrodes and start in the same manher as described above with reference to lamp L After both lamps L and L have started, they will be kept in operation by the secondary S in a closed series circuit with the serially connected lamps L and L This occurs because, after starting of lamp L the amount of current which can flow from the operating secondary S through starting capacitor 42 to lamp L becomes infinitesimal with relation to the current required to operate the lamp. Likewise, the amount of current which can flow between either electrode 25 or electrode 27 and the grounded fixture 20 also becomes infinitesimal with relation to the current between the re spective electrodes of lamps L and L Therefore only a very minor circuit, from a current standpoint can be completed through the ground 21 to ground lll'or through the starting loop including the starting capacitor 42. Consequently, the ballast transformer apparatus will, for practical purposes, act as an ordinary high reactan'ceisolated secondary transformer with the operating secondary S being excited by the primary P to produce sufii' cient current to keep lamps L and L in operation. The

secondary voltage will drop, once the arc is struck between the electrodes of the lamp L and L to diminish even further the current ilow through the rounded conducting fixture 29. V n

It will be understood that while all the circuits shown utilize a ballast transformer having a high reactance, the invention may be advantageously used where a low reactance transformer is used with other ballasting means. It will also be understood that while all the circ'uits shown are lag circuits, i.e., draw lagging current through the transformer, a lead circuit may be provided, for example, by the addition of capacitors in series with the operating secondary S as is well-known in the art. Also, while a rapid start lamp circuit has been shown, that is, the electrodes are heated both before and after starting, the invention may be advantageously applied to other types of lamp circuits. Therefore, while this invention has been explained by describing particular embodiments thereof, it will be apparent that improvements and modifications may be made without departing from the scope of the invention as defined in the appended claims.

What is claimed as new and desired to be secured by Letters Patent of the United States is:

l. A ballast transformer apparatus for starting and operating at least one fluorescent lamp mounted near a conductive part and having two spaced electrodes at the respective ends of said lamp comprising a magnetic core having a primary winding, a first secondary winding and a second secondary winding thereon, means connecting said first secondary winding to said primary winding in autotransformer relation therewith and directly to said second secondary winding in autotransformer relation therewith, said windings being wound and'connected in voltage adding relation, a pair of input lines on said primary winding for connection to a source of alternating current, a pair of output lines on said second secondary winding for respective connection to the electrodes of said lamp, and means for connecting the low potential end of said prim-ary winding in circuit with said conductive part whereby said transformer apparatus provides autotransformer type starting voltage in an auxiliary circuit including said conductive part and isolated type running voltage for said lamp.

. 2. A ballasttransformer apparatus for starting and operating a fluorescent lamp mounted in a conductive fixture and having two spaced electrodes at the respective ends of said lamp comprising, a magnetic core having a primary winding, a first secondary winding and a second secondary winding thereon, means connecting said first secondary winding to said primary winding in autotransformer relation and directly to said second secondary winding in autotransformer relation, said windings being wound and connected in voltage adding relation, means providing leakage reactance between said primary winding and said second secondary, a pair of input lines on said primary winding for connection to a source of alternating current,,outp'ut lines on said second secondary windings for respective connection to the electrodes of said lamp, and means for connecting the 'low potential end of said primary winding in circuit with said conducting fixture whereby said transformer apparatus provides autotransformer type starting voltage and isolated type running voltage for said lamp. 7 3. A ballast transformer apparatus according to claim 2 wherein said means for connecting the low potential end of said primary winding in circuit with said conductive fixture includes a ground connection.

' 4. A ballast transformer apparatus for starting and operating a hot cathode fluorescent lamp mounted in a conductive fixture and having two spaced electrodes at the respective ends of said lamps comprising a magnetic core having a primary winding, a first secondary winding and asecond secondary winding thereon, said first secondary winding having one end connected in autotransformer relation 'with said primary winding and having its other end directly connected in autotransformer connection with said second secondary winding and having end portions at each end forming cathode heating windings, said windings being wound and connected in voltage adding relation, a pair of input lines on said primary winding for connection to a source of alternating current, a first pair of output lines connected to one end portion of said second secondary winding for connection across one of the V electrodes of said lamp and a second pair of output lines connected to the other end portion of the said second secondary winding for connection across the other electrode of said lamp whereby said second secondary winding is connected across said lamp and provides heating voltages for the electrodes thereof, and means for connecting the low voltage end of said primary winding in circuit with said conductive fixture thereby to complete an electrical path for said windings during starting, the current through said fixture circuit being minor with reference to the current through said lamp from said second secondary winding after starting thereof.

5. A ballast transformer apparatus for starting and operating a pair of serially connected fluorescent lamps mounted in a conductive fixture and each having two spaced electrodes at their respective ends comprising, a magnetic core having a primary winding, a first secondary winding and a second secondary winding thereon, means connecting said first secondary winding to said primary Winding in autotransformer relation and directly to said second secondary winding in autotransformer relation therewith, said windings being wound and connected in voltage adding relation, a pair of input lines on said primary winding for connection to a source of alternating current, a pair of output lines on said second secondary windingfor connecting said second secondary in a series circuit with said pair of serially connected lamps, and means for connecting the low potential end of said primary winding in circuit with said conductive fixture whereby said transformer apparatusprovides'autotransformer type starting voltage and isolated type running voltage for said lamp.

6. Ballast transformer apparatus according to claim above wherein said means for connecting the low potential end of said primary winding in circuit with said conductive fixture includes a ground connection.

7. Ballast transformer apparatus for starting and operating firstand second fluorescent lamps mounted in a conductive fixture and each having first and second spaced electrodes at their respective ends comprising, a magnetic core having a primary winding, a first secondary Winding and a second secondary winding thereon, said first secondary winding having one end connected to said primary winding in autotransformer relation and having its other end directly connected to said second secondary winding in autortansformer relation, said windings being wound and connected in voltage adding relation, means providing leakage reactance between said second secondary winding and said primary winding, a pair of input lines on said primary winding for connection to a source of alternating current, a starting capacitor, output lines on said second secondary winding for connection of said secondary winding in a series starting loop including the first discharge lamp and the starting capacitor, output lines on said second secondary winding for respective connection of said second secondary winding in a series starting and operating loop including the first discharge lamp and the second discharge lamp, and means for connecting the low potential end of said primary winding in circuit relation with said conductive fixture whereby said transformer apparatus provides autotransformer type starting voltage and isolated type running voltage for said lamps.

8. Ballast transformer apparatus for starting and operating first and second hot cathode type fluorescent lamps mounted in a conductive fixture, each lamp having first and second spaced electrodes at its respective ends, comprising a magnetic core having a primary winding, a first secondary winding, a second secondary winding, a first cathode heating winding, a second cathode heating Winding, and a third cathode heating winding thereon, said first secondary winding having one end connected to the primary winding in autotransformer relation and having its other end connected directly to said second secondary winding in autotransformer relation, said primary winding, said first secondary winding and said second secondary winding being wound and connected in voltage adding relation, a pair of input lines on said primary winding for connection to a source of alternating current, a first pair of output lines connected to said first cathode heating winding for connection across one of the electrodes of said second lamp, a second pair of output lines connected to said second cathode heating winding for respective connection to said second cathode of said second lamp and the first cathode of said first lam and a third pair of output lines connected to said third cathode heating winding for connection to said second cathode of said first lamp, a starting capacitor, circuit means connecting said second secondary in a series starting circuit with said first lamp and said starting capacitor, said second secondary being connected in a starting and operating series circuit with said first and second lamps, and means for connecting the low voltage end of said primary winding in circuit with said conductive fixture thereby to complete an electrical path for said primary winding, said first secondary winding, and said second secondary winding during starting, the current through said fixture circuit being minor with reference to the current through said lamps from said second secondary winding after starting thereof.

9. Ballast transformer apparatus for starting and operating first and second hot cathode type fluorescent lamps mounted in a conductive fixture, each lamp having first andsccond spaced electrodes at its respective ends, compnsmg a magnetic core having a primary winding, a first secondary winding, a second secondary winding, a first cathode heating winding, a second cathode heating winding, and a third cathode heating winding thereon, said first secondary winding having one end connected to the primary winding in autotransformer relation and having its other end connected directly to said second secondary winding in autotransformer relation, said primary winding, said first secondary winding and said second secondary winding being wound and connected in voltage adding relation, a pair of input lines on said primary Winding for connection to a source of alternating current, a first pair of output lines connected to said first cathode heating winding for connection across one of the electrodes of said second lamp, a second pair of output lines connected to said second cathode heating winding for respective connection to said second cathode of said second lamp and the first cathode of said first lamp, and a third pair of output lines connected to said third cathode heating winding for connection to said second cathode of said first lamp, a starting capacitor connected between a first output line from said first cathode heating winding and one output line from said second cathode heating winding, circuit means connecting said second secondary between said first output line from said first cathode heating winding and one output line from said third cathode heating winding, said second secondary being connected in a series starting circuit with said first lamp and said starting capacitor and in a starting and operating series circuit with said first and second lamps, and means for connecting the low voltage end of said primary winding in circuit with said conductive fixture thereby to complete an electrical path for said primary winding, said first secondary winding, and said second secondary Winding during starting, the current through said fixture circuit being minor with reference to the current through said lamps from said second secondary winding after starting thereof.

10. A lighting system comprising a conductive fixture, at least one fluorescent lamp mounted along side said fixture, a high reactance ballast transformer comprising a magnetic core having a primary winding, a first secondary winding, and a second secondary winding Wound thereon, .means connecting said first secondary winding to the high potential end or" said primary winding in said autotransformer relation therewith and directly to said second secondary winding in autotransformer relation therewith, said windings being wound and connected in voltage adding relation, said second secondary winding being connected across said lamp, and electric circuit means connecting the low potential end of said primary winding to said conductive fixture.

11. A lighting system comprising a conductive fixture, a pair of serially connected fluorescent lamps, a high reactance ballast transformer comprising a magnetic core having a primary winding, a first secondary winding, and a second secondary winding thereon, said first secondary winding having one end connected to the high potential side of said primary winding and having the other end connected directly to said second secondary Winding in autotransformer relation therewith, said windings being wound and connected in voltage adding relation, a starting capacitor, said second secondary winding being connected in a series starting circuit with one of said lamps and said starting capacitor, and connected in series starting and running series circuit across both said serially connected lamps, and an electric circuit connecting the low potential end of said primary winding to said conductive fixture.

References Cited in the file of this patent UNITED STATES PATENTS 2,008,514 Peterson July 16, 1935 2,056,647 De Bruin Oct. 6, 1936 2,820,180 Feinberg Jan. 14, 1958