US3648207A

US3648207A - Apparatus for starting and operating electric discharge lamps

Info

Publication number: US3648207A
Application number: US131474A
Authority: US
Inventors: Saverio Caltagirone
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1971-04-05
Filing date: 1971-04-05
Publication date: 1972-03-07
Anticipated expiration: 1989-03-07

Abstract

An electric discharge lamp ballast apparatus employing a high leakage reactance type of transformer with a shell-type magnetic core and with electrical coils wound of turns of generally round insulated wire which is flattened on the sides to form an essentially oblong cross section with the pair of flattened opposed sides extending in an axial direction with respect to the coil and adjacent to the layer insulation of the coil. The beginning turn or turns and the ending turn or turns of the coil not being flattened, such that they form generally round leads for the coil. Round leads for tap connections to be formed intermediate the ends of the coil are formed by a turn or turns of the coil interconnecting adjacent layers of the coil not being flattened.

Description

United States Patent Caltagirone Mar. 7, 1972 [51] Int. Cl.

[ 54] APPARATUS FOR- STARTING .AND

OPERATING ELECTRIC DISCHARGE LAMPS [72] Inventor: Saverio Callagirone, Danville, Ill.

- [73] Assignee: General Electric Company [62] Continuation of Ser. No. 11,454, Feb. 16, 1970, abandoned.

[52] US. Cl. ..336/206, 174/1 19 R, 336/223 .1101! 27/28 [58] Field oiSeareh ..336/l55, 165, 206, 223, 222; 174/119 R, 129, 133

[56] References Cited UNITED STATES PATENTS 2,735,979 2/1956 Coben ..336/223 3,237,136 2/19'66 Lord .......336/206X 3,501,728 3/1970 Barriball ..336/223X Primary Examiner-Thomas J. Kozma Attorney-John M. Stoudt, Ralph E. Krisher, Jr., Radford M. Reams, Frank L. Neuhauser, Oscar B. Waddell and Joseph B. Forman [57] ABSTRACT An electric discharge lamp ballast apparatus employing a high leakage reactance type of transformer with a shell-type magnetic core and with electrical coils wound of turns of generally round insulated wire which is flattened on the sides to form an essentially oblong cross section with the pair of flattened opposed sides extending in an axial direction with respect to the coil and adjacent to the layer insulation of the coil. The beginning turn or turns and the ending turn or turns of the coil not being flattened, such that they fonn generally round leads for the coil. Round leads for tap connections to be formed intermediate the ends of the coil are formed by a turn or turns of the coil interconnecting adjacent layers of the coil not being flattened.

10 Claims, 9 Drawing Figures PAIENTEDMAR 1 @912 SHEET 2 [IF 2 FIG-8 LQ ma I04 INVENTOR. Saver-Io Caltagw ronq At tor/veg.

APPARATUS FOR STARTING AND OPERATING ELECTRIC DISCHARGE LAMPS This application is a continuation of application, Ser. No. 1 l,454, filed Feb. I6, 1970, now abandoned.

CROSS-REFERENCES TO RELATED APPLICATIONS The following copending applications assigned to the same assignee as the present application, are related:

Apparatus for Starting and Operating Electric Discharge Lamps, Richard D. Barriball, Ser. No. 604,417, filed Dec. 23, 1966, now 0.8. Pat. No. 3,501,728.

Improved Method and Apparatus for Winding Electrical Coils Saverio Caltagirone, Ser. No. 11,445, filed on Feb. 16, 1970.

Apparatus and Method for Winding Electrical Coils Saverio Caltagirone, Ser. No. ll,456,filed on Feb. 16, 1970.

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to apparatus for operating electric discharge lamps and more particularly to an improved apparatus employing flattened wire coils having cylindrical or round leads.

2. Description of the Prior Art In the shell type of high leakage reactance transformers used in apparatus for starting and operating electric discharge lamps, i.e., fluorescent lamps, the coils containing the various windings are mounted on a center winding leg, and the side portions of the coils are positioned within the window space provided between the outer yoke members of the core and the center winding leg. The window space dimensions of the magnetic core restrict the cross-sectional dimensions of the coil. It will be appreciated that the cross-sectional area of a ballast case cannot exceed certain standardized cross-sectional dimensions, and thereby a limit is imposed on the cross-sectional dimensions of the core and coil assembly. In view of these dimensional restrictions, the core and coil assemblies of ballast transformers have a generally elongated configuration.

Coils commonly used in ballast transformers are constructed of superposed layers of insulated circular conductor wire with interleaved layers of paper layer insulation. The superposed layers of turns are formed by winding the circular conductor wire on a suitable rectangular shaped spool made of kraft paper. The paper spool on which the coil turns are wound serves to insulate the turns from the center winding leg of the magnetic core.

In such conventional coils it will be apparent that the window space available in the core is not efficiently utilized because of the circular shape of the conductor wire. Thus, there was a need in a ballast apparatus for a core and coil assembly that would allow more conductive material to be used in window space available in a given magnetic core design. It was further desirable for better utilization of the core window space to replace copper conductor wire with aluminum wire. Also, it was desirable in a ballast apparatus to reduce the ballast case temperature.

These objectives were generally realized in accordance with the invention set forth in the above-mentioned related application, Apparatus for Starting and Operating Electric Discharge Lamps, Richard D. Barriball, Ser. No. 604,417, filed Dec. 23, I966. Briefly, as taught in this related application, the objectives were realized by winding the electrical coils of turns of insulated wire flattened on the sides to form an essentially oblong cross section with opposed elongated interlayer insulatingportions extending in an axial direction with respect to the coil and adjacent to the layer insulation of the coil.

However, it has been found that when coils are wound from insulated wire flattened on the sides to form an essentially oblong cross section, that as the beginning and ending portion of a turn or turns are pulled from between the layer insulation to form the coil leads, that kinks are formed where the flattened wire was bent around a comer of the rectangular coil form. It was further found that the strength of the wire was greatly reduced at these kinks, presumably due to the stressing of the wire from the flattening, the bending in winding, and the further twisting in pulling the wire out to form the coil leads.

After the wire is pulled from the coil to form the coil leads, it must be further handled and manipulated in assembling the coil on the magnetic core, and in attaching the coil leads to terminals for electrically connecting the coil in the apparatus for starting and operating electric discharge lamps. It was found that the coil leads would frequently break at the kinks during this handling and manipulation, thereby either causing the coil to be scraped, or at considerable additional expense the coil might be salvaged, if possible, by again extending the lead to its required length by splicing.

SUMMARY OF THE INVENTION Consequently, the object of the invention is to provide an improved arrangement for extending leads from the coil of a core and coil assembly of a ballast apparatus, wherein the coil is wound of turns of wire flattened on the sides to form an essentially oblong cross section with the pair of flattened sides extending in an axial direction with respect to the coil and adjacent to the layer insulation of the coil.

In carrying out the object in one fonn, the portion of a turn or turns of the coil which are to form the leads of the coil are not flattened as are all of the other turns of the coil.

The subject matter which I regard as my invention is particularly pointed out and distinctly claimed in the concluding portion of the specification. The invention itself, however, together with further objects and advantages thereof, may be best understood by reference to the following description taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an enlarged sectionalized view in perspective of a coil assembly embodying a preferred form of the invention;

FIG. 2 is a magnified view of a cross section of a single conductor wire used in winding the coil assembly shown in FIG. 1;

FIG. 3 is a magnified view of a cross section of conductor wire flattened at four sides that can be used in winding a coil assembly as shown in FIG. 1;

FIG. 4 is a magnified view of a corner portion of a sectionalized coil assembly such as shown in FIG. I, but in accordance with the prior art, and before the coil leads are pulled;

FIG. 5 is a magnified view of a corner portion of the sectionalized coil assembly as shown in FIG. I, but before the coil leads are pulled;

FIG. 6 is a magnified view of a coil lead pulled from a coil assembly of the prior art as shown in FIG. 4;

FIG. 7 is a magnified view of a coil lead pulled from a coil assembly embodying a preferred form of this invention, as shown in FIG. 1;

FIG. 8 is an enlarged plan view of a magnetic core and coil assembly of the type in which coil assemblies as shown in FIG. 1 are utilized;

FIG. 9 is a schematic circuit diagram of a ballast apparatus utilizing a core and coil assembly as shown in FIG. 8.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings, and particularly to FIG. I, l have shown therein a view of a coil assembly 2 constructed in accordance with this invention, which is formed of a plurality of superposed layers of insulated conducting wire interleaved with insulation layers which are wound over an insulating spool 3. The conductor wire layers 4, 6, 8, l0, l2, l4, and 16 are of a generally oblong cross-sectional configuration, with at least a pair of flattened opposite sides, as is shown in FIGS. 4 and 5. Insofar as the coil assembly of the prior art shown in FIG. 4 and the coil assembly of the preferred form of this invention shown in FIG. 5 include identical elements, they will be referred to by the same identifying numerals. Corresponding elements which are not identical will be identified by the same identifying numerals, primed in FIG. 5. More specifically, the conductor wire has a cross-sectional configuration as shown in FIG. 2. The opposed interlayer insulation portions 18 and 20 as viewed in FIG. 2 are formed by flattening a round insulated metallic conductor 22 to provide the desired flattening ratio (ratio of the transverse length to the height of the wire cross section). The

interconductor insulating portions

24 and 26 are generally oval in shape and have a thickness that is slightly greater than the thickness of the interlayer insulting portions 18 and 20.

Wire which is flattened on four sides as shown in FIG. 3 may be used to further advantage to improve the space factor in a coil, and the teachings of this invention are equally applicable with either the wire flattened on two sides as shown in FIG. 2, or four sides as shown in FIG. 3. While for ease of illustration, wire flattened on four sides is shown in FIGS. 4 and 5, at the present time wire flattened on only two sides as shown in FIG. 2 would appear to be more feasible from a manufacturing viewpoint, even though the wire flattened on four sides would yield a better space factor in a coil.

The advantages of forming a coil of the type of this invention of flattened conductor wire is further set forth in the above-mentioned copending application entitled Apparatus for Starting and Operating Electric Discharge Lamps, Richard D. Barriball, Ser. No. 604,417 filed Dec. 23, 1966, which application is assigned to the same assignee as the present application.

The conductor wire layers 4, 6, 8, 10, 12, 14, and 16 are interleaved with

insulation layers

28, 30, 32, 34, 36, 38 and 40 which may in a typical application be formed of vegetable parchment approximately 0.002 of an inch in thickness. It will be appreciated that the paper insulation layers minimize the effect of voltage stress between conductor wire layers by providing an insulating barrier between the conductor wire layers. Further, it will be seen that the paper insulation layers extend beyond the outer turns in each conductor wire layer. These extensions of the insulation layers provide a spacing between the end turns and the adjacent parts of the magnetic core thereby preventing the end turns from grounding by contacting the magnetic core on which the coil is placed. In order to protect the outer conductor wire layer 16 of the coil, multiple insulation layers 40 and 42 are provided at the outer surface of the coil assembly 2. Strips of pressure

sensitive tape

44 and 46 prevent the outer insulation layers from unraveling.

It will be appreciated that it is necessary to bring leads out from the coil assembly in order to make electrical connections to the coil. Thus, in the coil shown in FIG. 1 a start lead 48, a tap 50 and a finish lead 52 are brought out from one end of the coil. The manner in which the conductor wire for these

leads

48, 50 and 52 is provided will be understood by making reference to FIGS. 4 and 5. Coils of the type shown herein may be wound on a multiple coil winding machine. In such a winding machine, a plurality of coils such as shown in FIG. 1 are wound in a side by side relationship, on a long insulating tube with common sheets of layer insulation between the wire layers. As is seen in FIG. 1, and in further detail in FIGS. 4 and 5, a margin is provided at each end of the coil, such that when the plurality of coils wound together are cut apart, it is only necessary to cut through the layer insulation and the spool, the wire conductors being spaced from the area to be cut.

In order to provide conductor wire for bringing out coil leads such as 48, 50 and 52 shown in FIG. 1, extra conductor wire turns are provided in one or more layers of the coil such that these conductor wire turns may be pulled out from between the insulation layers, or in the case of the start lead from between the spool 3 and the first insulation layer 28. Referring particularly to the prior art coil assembly shown in FIG. 4, in order to provide three coil leads 48, 50 and 52 as shown in FIG. 1, two additional turns are provided in conductor wire layers 4, I2 and 16. The conductor of these additional turns is pulled from between the insulation layers to extend from the coil as shown in FIG. 1. The two

extra conductors

54 and 56 provided in the first wire layer 4, form a start lead such as that shown as 48 in FIG. 1. To insure that when the conductor turns 54 and 56 are pulled from the first conductor layer to form the start lead 48, that additional turns are not also pulled out, it is a customary practice to anchor the following turns such as 58 and 60. For instance, after winding the conductor turns 54 and 56, a piece of adhesive tape 62 having its adhesive side facing upward, is Iayed over the top of conductor turns 54 and 56, along the right side of conductor turn 54 and on top of the layer insulation 64 wound over the spool 3. Thereafter the winding is continued, to wind conductor turns 58 and 60 over the adhesive tape. After these turns have been wound, but prior to completing the winding of the first conductor layer 4, the tap which was laying over conductor turns 54 and 56 is folded back over conductor turns 58 and 60 as shown in FIG. 4. Thereafter the layer insulation 28 is placed over the first conductor layer 4, and the succeeding conductor layer 6 wound thereover. Thus, when the conductor turns 54 and 56 are pulled from the left end of the coil to form the start lead 48 as shown in FIG. 1, the turn 58 will not be pulled out, wherein it will be retained by the adhesive tape anchor 62.

Similarly, extra conductor turns 68 and 70 are provided in winding layer 12 to provide a tap connection such as is shown as 50 in FIG. 1. Again, a piece of adhesive tape 71 is placed around the preceding conductors turns 72 and 74 in winding layer 12 to insure that they are not pulled from between the layer insulation with conductor turns 68 and 70. Wherein conductor turn 68 connects with first conductor turn 76 in the following conductor layer 14, an adhesive type anchor 75 is also placed around conductor turns 76 and 78 to insure that they are not pulled from between the insulation layers 36 and 38. In a similar manner adhesive tape anchor 79 secures conductor turns 80 and 82 in the last conductor layer 16 to prevent their being pulled from between the layer insulation with conductor turns 84 and 86 which fonn the finish lead 52.

As set forth hereinbefore, when a coil lead is pulled from a coil formed entirely of flattened conductor wire, such as is shown in FIG. 4, kinks will be formed in the flattened conductor lead as shown at 88, 90 and 92 in FIG. 6. One of these kinks will occur at each point where the conductor was bent in winding it in the coil.

Each of these kinks represents a portion of the coil lead which has been to a considerable degree work hardened. In each of these portions some work hardening is contributed by the flattening of the conductor, more is contributed by the bending in winding the coil, and still more is contributed by the twisting experienced as the conductor turn is pulled to form the coil lead. Subsequent operations to be performed in the assembly of the coil in a core and coil assembly and, the subsequent making of electrical connections to the coil leads subject the kinks such as 88, 90, and 92 to further bending stresses, which all too frequently lead to the breaking of the lead at one of the kinks.

In accordance with this invention, an improved flattened wire coil assembly has been provided which eliminates the frequent breakage problem of coil leads which have been pulled from between the layer insulations of the coil. However, the improved flattened wire coil assembly at the same time retains all of the benefits to be gained from the use of flattened conductor wire as hereinbefore set forth. Thus, in accordance with this invention, the extra conductor turns provided in the various conductor layers to form leads for a coil such as 48, 50 and 52 shown in FIG. I, are formed from round wires, while the remaining turns of the coil are formed of the desired flattened wire.

Referring to FIGS. 5 and 7, the improved flattened wire coil assembly of this invention will be described. As previously set forth, the same numerals as were used on FIG. 4 will be used on FIG. 5 to identify identical elements of the coil assembly. Where in accordance with this invention the elements are not identical, corresponding elements will be identified with the same numeral primed. In beginning to wind the first conductor layer 4 of the coil on the layer insulation 64, the first few conductor turns 54' and 56' which are provided to form the start lead 48 of thecoil as shown in FIG. 1, are wound with unflattened round conductor. At a point just prior to the application of the adhesive tape 62 which secures the conductor turns 58 and 60, the wire is flattened, and continues to be flattened as conductor layers 4, 6, 8, l0 and 12 are wound, until just after the adhesive tape anchor 71 is applied to secure conductor turns 72 and 74. After the insertion of the anchor tape 71, the winding of turns 72 and 74 thereover, and the folding back of tape 71 over turns 72 and 74, the conductor is no longer flattened, such that the turn 68' and 70 which form the tap connection 50, are formed of round conductor. Just prior to the application of anchor tape 75 under the conductor forming turns 76 and 78 in wire layer 14, the wire is again flattened, such that turns 76 and 78 are formed of flattened conductor. The conductor continues to be flattened throughout the winding of coil until just after the winding of turns 80 and 82 in the outermost conductor layer 16, and the folding back of the anchor tape 83 over these turns. At this point the conductor is again not flattened, such that the turns 84' and 86' forming finish lead 52 of the coil are formed of round conductor.

With the conductor turns 54', 56', 68, 70, 84 and 86' which form the coil leads 48, 50 and 52 shown in FIG. 1, formed of round conductor, when these turns are pulled from between the layers of insulation, the coil leads will be formed of round wire. Thus, the kinks which were present in the flattened conductor leads as shown in FIG. 6, will not be formed, but instead the leads will have the appearance of the round conductor 94 shown in FIG. 7.

It has been found that the breakage of coil leads in subsequent handling may be greatly reduced in the manner just described. Therefore, the round coil leads as formed in accordance with this invention are much easier to handle in the later assembly of the core and coil assembly and the connection of the coil leads in the electrical circuit of the ballast apparatus.

As embodied in this invention the entire conductor winding of the coil is formed from a single unspliced strand of round conductor. The entire strand'of round conductor is flattened to be wound in the conductor layers of the coil, except for those portions which are to form the coil leads. Various arrangements would be possible for forming a continuous strand of conductive material including longerportions of flattened conductor material, interspaced'at desired intervals with the round conductor material for forming the coil leads. However, a coil in accordance with this invention is most conveniently formed wherein the wire is flattened by a wire flattening mill just prior to its being wound in the coil on a coil winding machine. In such an arrangement, the operation of the wire flattening mill is synchronized with the operation of the winding machine, such that the pressure on the winding mill rollers which flattens the conductor is released so as to provide the round conductor at the desired intervals for providing the coil leads as shown in FIGS. 1 and 5. Such an apparatus for winding electrical coils is set forth in my above-mentioned related patent application entitled, Apparatus and Method for Winding Electrical Coils application Ser. No. 11,456, filed Feb. 16, 1970.

Referring now to FIGS. 8 and 9, the manner in which a coil assembly such as shown in FIG. 1 is used in an apparatus for starting and operating electric discharge lamps will be described. As shown in FIG. 8, a pair of

coil assemblies

102 and 104, constructed in accordance with this invention in the manner shown in FIGS. 1 and 5, are utilized in a magnetic core and coil assembly 106. The

coil assemblies

102 and 104 are mounted on a magnetic core 108 comprising a pair of

outer yoke members

110 and 112 and a center winding leg 114 on which the

coil assemblies

102 and 104 are supported. Core clamps 116 and 118 hold the

outer yoke members

110 and 112 and the center winding leg 114 in assembled relation. The

outer yoke members

110 and 112 and center winding leg 114 are formed of stacks of horizontally extending laminations punched from sheet magnetic material. The core and coil assembly 106 shown in FIG. 8 along with other components such as capacitors and resistors are encapsulated in an enclosure to form a ballast apparatus from which leads extend for connection to a power supply and to fixture terminals for energizing gaseous discharge lamps.

Referring now more particularly to the schematic circuit diagram illustrated in FIG. 9, I have identified the core and coil assembly by the same reference numeral 106. The core and coil assembly and the resistors and capacitors making up the ballast apparatus are shown enclosed in a dashed rectangle 120 which represents the ballast case. It will be appreciated that certain connections with coil assemblies, which are shown schematically in FIG. 9 are made by bringing out start and finish leads such as 48 and 52 in FIG. 1 to terminal pads. For a more detailed description of a typical terminal lead arrangement which may be used in making such circuit connections, reference may be had to US. Pat. No. 3,217,278 issued to G. W. Beckes et al., and assigned to the assignee of the present invention.

The parts of the core and coil assembly 106 are shown schematically in FIG. 9 and include the magnetic core 108, a primary winding P, and a secondary winding S, inductively coupled on the magnetic core 106, and cathode heating winding 11,, H and H A pair of

input terminals

121 and 122 are provided for connection to a suitable alternating power source (not shown) such as a 60 cycle, 120 volt alternating current pp y- 7 The

fluorescent lamps

124 and 126 operated by the ballast apparatus are of the rapid start type and are preferably positioned in close proximity to a grounded conductive fixture or plate 128 so that the

lamps

124 and 126 are disposed in capacitive relationship with respect to the fixture or plate 128. A flux leakage path is generally provided between the primary winding P, and the secondary winding S, and may be formed through nonmagnetic material, such as air, or through magnetic material.

Continuing further with the description of the circuit connections, it will be seen that the cathode heating windings H,, H and H continually supply the filaments of

fluorescent lamps

124 and 126 with heating current during operation. Cathode heating winding H,, which is an extension of the primary winding P,, is connected in circuit with filament 130 by

leads

132, and 134. Cathode heating windings H, and H, are connected in circuit with

filaments

136, 138 and 140 by

leads

142, 144, 146 and 148. Cathode heating windings H, and H, are preferably tightly coupled with the primary winding P, and may, if desired, be wound directly over the primary winding.

One end of the secondary winding S, is connected in circuit with the primary winding P, in autotransformer relationship. The other end of the secondary winding S, is connected in circuit with the series capacitor C,, which provides a net capacitive reactance in the lamp circuit. A starting capacitor C is connected across lamp 124 so that the open circuit starting voltage is initially applied across lamp 126. Resistors R, and R which shunt the series capacitor C, and the starting capacitor C are bleeding resistors and cause the charge to be bled oh the capacitors C, and C when the circuit is deenergized.

The advantages of the present invention can be realized in a ballast apparatus for starting and operating a single fluorescent lamp, as well as for starting and operating two or more fluorescent lamps. Further, it will be appreciated that the advantages for the present invention can be used with a magnetic core and coil assembly having one or any number of coil assemblies.

It should be apparent to those skilled present, the art that while I have described what, at present is considered to be the preferred embodiment of this invention in accordance with the Patent Statute, changes may be made in the disclosed apparatus without actually departing from the true spirit and scope of this invention.

What I claim is new and desire to secure by Letters Patent of the United States is:

l. A coil assembly comprising:

a. a spool of insulating material formed with an axial opening discharge lamp from an alternating current source, said ballast apparatus having a magnetic core and coil assembly with a magnetic core formed of laminations of magnetic material and including a winding leg, the improvement comprising at least one coil assembly including:

b. a plurality of turns of conductor wire forming a coil wound on said spool to form layers of conductor wire, said turns of conductor wire being formed from generally cylindrical wire which is flattened on at least two sides thereof to form an essentially oblong cross section,

c. layers of insulating sheets interposed between layers of said flattened conductor wire, and

d. at least a portion of a beginning turn in the first layer of said conductor wire and at least a portion of an ending turn in the last layer of said conductor wire not being flattened on at least two sides, such that said portion of a beginning turn and said portion of an ending turn when extended from said first layer and saidlast layer of said conductor wire form generally cylindrical leads for said coil of conductor wire.

2. A coil assembly as defined in claim 1 wherein at least a portion of a turn of conductor wire interconnecting adjacent layers of flattened conductor wire is not flattened on at least two sides, such that said at least a portion of a turn of conductor wire when extended from said layers of said conductor wire forms a generally cylindrical tap lead for said coil of conductor wire.

3. In a ballast apparatus for operating at least one electric a. a spool of insulating material formed with an axial opening and mounted on the winding leg of the magnetic core for supporting the coil assembly thereon,

d. at least a portion of a beginning turn in the first layer of 40 said conductor wire and at least a portion of an ending turn in the last layer of said conductor wire not being flattened on at least two sides, such that said at least a portion of a beginning turn and said at least a portion of an ending turn when extended from said first layer and said last layer of said conductor wire form generally cylindrical leads for said coil of conductor wire.

4. The ballast apparatus set forth in claim 3 wherein at least a portion of a turn of conductor wire interconnecting adjacent layers of flattened conductor wire is not flattened on at least two sides, such that said at least a portion of a turn of conductor wire when extended from said layers of said conductor wire forms a generally cylindrical tap lead for said coil of conductor wire.

5. A coil assembly comprising:

a. a plurality of turns of conductor wire forming a coil wound to form layers of conductor wire, said turns of conductor wire being formed from generally cylindrical wire which is flattened on at least two sides thereof to form an essentially oblong cross section,

b. at least a portion of a beginning turn in the first layer of said conductor wire and at least a portion of an ending turn in the last layer of said conductor wire not being flattened on at least two sides, such that said portion of a beginning turn and said portion of an ending turn when extended from said first layer and said last layer of said conductor wire from generally cylindrical leads for said coil of conductor wire.

6. A coil assembly as defined in claim 1 wherein at least a portion of a turn of conductor wire interconnecting adjacent layers of flattened conductor wire is not flattened on at least two sides, such that said at least a portion of a turn of conductor wire when extended from said layers of said conductor wire forms a generally cylindrical tap lead for said coil of conductor wire.

7. A coil assembly as defined in claim 5, with said turns of conductor wire being formed from generally cylindrical wire which is flattened on at least four sides thereof to form an essentially rectangular cross section.

8. In a ballast apparatus for operating at least one electric discharge lamp from an alternating current source, said ballast apparatus having a magnetic core and coil assembly with a magnetic core formed of laminations of magnetic material and including a winding leg, the improvement comprising at least one coil assembly including:

b. at least a portion of a beginning turn in the first layer of said conductor wire and at least a portion of an ending turn in the last layer of said conductor wire not being flattened on at least two sides, such that said at least a portion of a beginning turn and said at least a portion of an ending turn when extended from said first layer and said last layer of said conductor wire form generally cylindrical leads for said coil of conductor wire.

9. The ballast apparatus set forth in claim 3 wherein at least a portion of a turn of conductor wire interconnecting adjacent layers of flattened conductor wire is not flattened on at least two sides, such that said at least a portion of a turn of conductor wire when extended from said layers of said conductor wire forms a generally cylindrical tap lead for said coil of conductor wire.

10. A coil assembly as defined in claim 8, with said turns of conductor wire being formed from generally cylindrical wire which is flattened on at least four sides thereof to form an essentially rectangular cross section.

Claims

1. A coil assembly comprising: a. a spool of insulating material formed with an axial opening b. a plurality of turns of conductor wire forming a coil wound on said spool to form layers of conductor wire, said turns of conductor wire being formed from generally cylindrical wire which is flattened on at least two sides thereof to form an essentially oblong cross section, c. layers of insulating sheets interposed between layers of said flattened conductor wire, and d. at least a portion of a beginning turn in the first layer of said conductor wire and at least a portion of an ending turn in the last layer of said conductor wire not being flattened on at least two sides, such that said portion of a beginning turn and said portion of an ending turn when extended from said first layer and said last layer of said conductor wire form generally cylindrical leads for said coil of conductor wire.

3. In a ballast apparatus for operating at least one electric discharge lamp from an alternating current source, said ballast apparatus having a magnetic core and coil assembly with a magnetic core formed of laminations of magnetic material and including a winding leg, the improvement comprising at least one coil assembly including: a. a spool of insulating material formed with an axial opening and mounted on the winding leg of the magnetic core for supporting the coil assembly thereon, b. a plurality of turns of conductor wire forming a coil wound on said spool to form layers of conductor wire, said turns of conductor wire being formed from generally cylindrical wire which is flattened on at least two sides thereof to form an essentially oblong cross section, c. layers of insulating sheets interposed between layers of said flattened conductor wire, and d. at least a portion of a beginning turn in the first layer of said conductor wire and at least a portion of an ending turn in the last layer of said conductor wire not being flattened on at least two sides, such that said at least a portion of a beginning turn and said at least a portion of an ending turn when extended from said first layer and said last layer of said conductor wire form generally cylindrical leads for said coil of conductor wire.

5. A coil assembly comprising: a. a plurality of turns of conductor wire forming a coil wound to form layers of conductor wire, said turns of conductor wire being formed from generally cylindrical wire which is flattened on at least two sides thereof to form an essentially oblong cross section, b. at least a portion of a beginning turn in the first layer of said conductor wire and at least a portion of an ending turn in the last layer of said conductor wire not being flattened on at least two sides, such that said portion of a beginning turn and said portion of an ending turn when extended from said first layer and said last layer of said conductor wire from generally cylindrical leads for said coil of conductor wire.

8. In a ballast apparatus for operating at least one electric discharge lamp from an alternating current source, said ballast apparatus having a magnetic core and coil assembly with a magnetic core formed of laminations of magnetic material and including a winding leg, the improvement comprising at least one coil assembly including: a. a plurality of turns of conductor wire forming a coil wound to form layers of conductor wire, said turns of conductor wire being formed from generally cylindrical wire which is flattened on at least two sides thereof to form an essentially oblong cross section, b. at least a portion of a beginning turn in the first layer of said conductor wire and at least a portion of an endIng turn in the last layer of said conductor wire not being flattened on at least two sides, such that said at least a portion of a beginning turn and said at least a portion of an ending turn when extended from said first layer and said last layer of said conductor wire form generally cylindrical leads for said coil of conductor wire.