US2946922A - Ballast apparatus - Google Patents

Description

l July 26, 1960 c. R. DOUGHERTY BALLAST APPARATUS Filed Aug. 31. 1959 United States Patent BALLAST APPARATUS Charles R. Dougherty, Danville, Ill., assignor to General Electric Company, a corporation of New York Filed Aug. 31, 1959, Ser. No. 837,231 1s claims. (ci. 315-100) vthrough this channel. Generally, the lixtures are arranged to accommodate two lamps and the ballast is also designed for use with two lamps.- There are, however, certainap plications in` which it isdesired to mount three lamps within a single fixture, for example, to obtain an increased illumination level, and-for these applications, theordinary two-lamp ballast is obviously unsuited. It could, of course, be used for two of the lamps with a separate ballast being provided for the third lamp, but this would entail considerable expense. Thus, for reasons of economy, it is desirable that a ballast be provided for the three lamp fixtures, which is capable of handling all three lamps.

The three-lamp ballast must, of course,.provide a good current balance between the lamps if the lighting eect from themis to be uniform. In other words, the ballast should cause approximately the same amount of current to flow through all three lamps to avoid objectionable differences in their light output. Also, for best operation with minimum power cost, it is ordinarily desirable that the ballast operate at unity power factor or at a slightly leading power factor. A further requirement of the ballast is that it -be relatively'srnall in .widthvand shallow inv height so that it can fit into the mounting channel in-the usual fixture. The ballast ycan be relatively elongated since the channel usually extends for the length 'of the xture, but ordinarily the size of the channel sets definite limits on the allowable height and width of the ballast.

Accordingly, it is a general object of my invention to provide a new and improved ballast for operating three fluorescent lamps; and it is a more specicvobject of my invention to provide a three-lamp ballast which is elongated and shallow for mounting within the iixture channel but yet gives a good current balance between the lamps and operates at high powerfactor.

Another object of my invention is to provide a threelamp ballast which incorporates standard core punchings usable in two-lamp ballasts whereby the three-lamp ballast may be produced without appreciable design, tooling and other expense for its magnetic core.

A further object of my invention is to provide an im.- proved arrangementof the windings in a ballast transformer, which is particularly advantageous for use in a three-lamp ballast but which may also be used in other ballast apparatus. Y

In carrying out my invention in one form thereof, VI provide a ballast apparatus for starting and operating threeuorescent lamps which comprises a high reactance transformer having a magnetic core, with an elongated winding leg vand `arl outer yoke member. A plurality of windings are disposed on the winding leg side by side re- 2,946,922 Y Patented July 1960 ary windings. The lead circuit secondary winding is autotransformer connected to the primary winding and is further connected in series circuit relation to a capacitive reactor to form a lead circuit for operating two of the lamps with leading current. The lag circuit secondary windings are electrically isolated from the primary wind-- ing and are serially interconnected to form a lag circuit for operating the third lamp with lagging current.

According to an `important aspect of my invention, the windings are-so arranged'on the winding leg that the proper ballasting elect is obtained in both circuits to provide a good current balance therebetween. In particular, the one lag circuit secondary is located between the primary windi'ng andthe lead circuit secondary, with the, other lag circuit secondary being located on the opposite side of the primary winding. A restricted section is provided in the winding leg under the last mentioned lag circuit secondary but otherwise the Winding leg is of suby stantially uniform cross-section throughout. With this arrangement of the windings and the winding leg, the proper voltages and ballasting impedances are provided in both circuits for uniform lamp operation. The side by side arrangement of the windings also results in an elongated ballast which is shallow in height and width as desired for use with most lamp fixtures. Y The subject matter which l regard as my invention is particularly pointed out and distinctly claimed in the concluding portion of this specification; My invention, however, both as to organization and method of operation, together with further objects and advantages thereof, may best be understood by reference to the-following description taken in conjunction with the accompanying drawing- Fig. 2 is a plan view of the ballast apparatus includedv in the circuit of Fig. 1. A

Referring now to the drawings, there is illustrated there- 1n an improved ballast apparatus 1 for operating three gaseous discharge lamps such as the lamps 50, 51 and 52.' The lamps S0, 51 and 52are all mounted within a singlev xture 5 and this lixture is preferably grounded as indicated at 6; The lamps are of the heated cathode type, each having a pair of lilamentary cathodes which are illustrated in the form of a coil of tungsten wire. for example, may be of the well-known rapid start type and their cathodes are continuously heated during operation as will be more fully described hereinafter.

The ballast apparatus for startingv and'operating the outer yoke or flux return member 5. The yoke member 5, as shown, consists of oppositely disposed sections 5aand- 5b which have end legs abutting the winding leg 4r at its opposite ends.

tions are both formed of a plurality of stacked laminatioris yof magnetic material, such as, for example, transformer' steel.

Arranged on the winding Yleg 4 within the Vyoke mem'- ber 5 are a plurality of windings or coil's for starting and operating the liuorescent'lamps 'S0-52. These windings include aprimary winding 6, a lead circuit secondary winding 7 and a pair of'lag circuit secondary windings- 8 and 9.Y As shown, the-windings are arranged in side by.

side relationship on the winding leg with the lag circuitv secondary9 being positioned between the primary 6 andr the lead Vcircuit secondary 7. The other lag circuit secondary -8 is positioned on the opposite side of the primary The lamps;

The winding leg and the yoke scc- 6 from the lag secondary 9, and between the lag secondary 8 and the primary, flux leakage legs or shunts 10 are provided on the yoke member 3. The flux leakage legs 10 provide a flux shunting path between the primary 6 and the lag secondary 8 and, as shown, a small air gap is provided between the end of each leakage leg and the winding leg to make this shunting path of relatively high reluctance.

Besides the shunt path 10 the core is also provided with another very important means forV controlling the flux linking the coil 8. This means comprises a slot or bridged gap 11 which is formed in the winding leg 4 in the region of the secondary 8. Specifically, in the illustrated embodiment, the bridged gap 11 is formed beneath the right-hand side of the coil. This bridged gap provides the winding leg witha portion of restricted cross-section, which determines the impedance ofthe coil' 8 and specially reduces its impedance over that which would be present without such a gap. The purpose and effect of this `bridged gap on the operation of the ballast apparatus will be explained in detaily hereinafter. In the construction of the transformer 2, the coils 6 9 are formed independently and are slipped onto the winding leg over the ends thereof. When the coils are in place, the yoke sections Sa and 5b are then placed over them and abutted against the ends of the winding leg to complete the core. As shown, the entire core structure is held together by means of clamps 12 and 13 which are fitted over the opposite ends of the core.

Referringr now to Fig. `1, it will be seen that the primary 6 is provided with suitable input leads 14 and 14a by which it may be connected to a suitable source of single phase alternating current such as is indicated by the supply lines 15 and 15a. The supply line 15 is shown as grounded and when the apparatus 1 is connected to a grounded supply, the input lead 14 should be connected to the grounded side of the line. The lead circuit secondary 7 is autotransformer connected to the primary 6 so that the two windings are placed inan additive voltage relationship. .As shown, the autotransformer connection is made at the lead 14.

' Besides being autotransformer connected to the primary, the lead circuit secondary 7 is also connected in series circuit relation to a capacitor 16 to form a lead circuit for energizing the lamps 50 and 51 with leading current. As shown, the lead secondary 7 is connected to the capacitor 16 by a lead 16a and'from the other side of the capacitor, an output lead V17 extends out of the ballast for connection to the upper cathode 18 of the lamp 50. The other output lead for the lead circuit comprises the lead 19 which is connected to the end of the primary remote from the autotransformer and extends out of the ballast for connection'to the lower cathode 20 of the lamp 51. The remaining two cathodes 21 and 22 of the two lamps are serially connected by means of the leads 23, 24 to complete the circuit for the lamps. It will be noted that in this circuit the primary 6, the lead secondary 7, the capacitor 16 and the lamps 50 and 51 are all connected in series circuit relation. As is shown in Fig. 2, the capacitor 16 is positioned at one end of the ballast case 53 which also encloses the high reactance autotransformer 2, and the connection 16a between the capacitor and the secondary 7 and the autotransformer connection between the primary and secondary 7 are both made within the case so that only the leads for the lamps extend out of the case.

As mentioned above, the lamps 5 0 and 51 are preferably rapid start lamps including heated cathodes, and suitable heating windings are mounted on the winding leg 4 for energizing the lamp cathodes during operation. Specifically, three heating windings or secondaries 25, 26 and 27 are provided on the Winding leg in the region of the primary 6 so that they are tightly coupled thereto. As is indicated in Fig. 2 these heating windings 25,-27 may be -wound directly over the primary 6. 'I'he rst heating winding 25 is connected across the cathode 18 by means of the leads 17 and 28 so that it continuously supplies heating current to cathode 18 during the lamp operation. The second heating winding 26 supplies heating current to the cathodes 21 and 22 through the leads 29, 30, 23 and 24. As shown, the cathodes 21 and 22 are connected in parallel across the heating winding 26 for heating purposes. The final heating winding 27 is connected across the cathode 20 by leads 19 and 31 so as to pass heating current through it. As shown, winding 27 may form an extension of the primary 6.

In order to start the lamps 50 and 51 sequentially, a starting capacitor 32 is connected between the leads 17 and 30 so that it is in parallel with the lamp 50. As indicated in Fig. 2, the starting capacitor '32 is preferably within the same can as the lead circuit capacitor 16. When the ballast apparatus is first placed in operation,

i.e., when the primary 6 is first energized, the combined' voltages of the primary 6 and the secondary 9 are applied across the lamp 5 1 through the capacitor 32. This causes the lamp 51 to ignite. Once the lamp ignites, current. of course, ows through the capacitor 32 which is of much greater impedance than the lamp 51 so that most of the voltage in the lead circuit then appears across it. This places a great enough voltage across the lamp 50 to cause it to ignite vwhich action occurs substantially immediately. After lamp 50 ignites, the lamps 50 and 51 are then operated in series with the lamp 50 effectively forming a low impedance bypass around the starting capacitor 32. Due to the capacitor 16 in the series circuit, the circuit draws a leading current through the lamps 50 and 51. The circuit of' lamps 50 and 51 therefore comprises what is known as a lead circuit,

Besides starting and operating the lamps Si) and 5l, the ballast 1 also serves the same function for the lamp 52. The lamp 52 is started and operated by the two lag circuit secondaries 8 and 9. As shown in Fig. l, the windings 8 and 9 are serially connected in additive voltage relationship by means of a connection 33 within the ballast case 53, At their ends, remote from the connection 33, the two lag secondaries are connected to the lamp 52 by means of the output leads 34 and 35, and it will be seen that by reason of these leads the two lag second aries 8 and 9 form a Series circuit with the lamp 52.

In order to heat the cathodes 46 and 37 of the lamp 52 during operation, there are provided a pair of heating windings 38 and 39 which are located on the core in the region ofthe lag secondary 8. The heating windings 33 and 39 are closely coupled to the lag secondary 8 and in the illustrated embodiment, they are wound directly over the lag secondary 8 as is indicated in Fig. 2. The winding 38 is connected across the cathode 36 by means of the leads 35 and 40, and the winding 39 is connected across the cathode 37 by means of the leads 34 and 41. With these connections the windings 38 and 39 continuously supply heating current to the cathodes 36 and 37 during the operation of lamp 52. The heating winding 38 may be Iformed as shown in Fig. 2 as an extension of the lag secondary 8.

In the series operating `circuit for the lamp 52 there is no reactance other than that provided bythe lag secondaries 8 and 9. In other words, there is only inductive reactance in this circuit and thereby a lagging current is drawn by the circuit, which current, of course, passes through the lamp 52. This circuit is thereby known as a lag circuit. Since this circuit draws lagging current while the circuit for lamps 50 and 51 is drawing leading current, the net result is that the ballast operates at quito a good power factor. In particular, in one embodiment of my invention, the ballast has been found effective to operate three F40Tl2/RS forty watt rapid start lamps with an input power factor of about 94%.

The construction and arrangement of the autotransformer 2 comprises a very important aspect of my invention, In particular, the successful operation of my ballast apparatus depends upon the positioning andarrangement o the various secondaries relative to primary 6. I have found that by positioning the lag secondary 9 between the primary 6 and the lead secondary 17 and by positioning the lag secondary S on the other side of the primary with a bridged gap beneath it, a proper ballasting impedance can be obtained in both the lead circuit and the lag circuit to provide a good balance between the lamps. With this arrangement of the windings, suiicient voltage is provided to start the lamps, and once the lamps are in operation, the correct ballasting eect is produced to give good current balance between them.

It will be noted that all of the secondaries 7-9 are l loosely coupled to primary, each having at least some therebetween. The leakage ux path for winding 8, of

course, comprises the shunt legs 10, while for windings 7 and 9, the ilux leakage path comprises the air space between the winding leg and the yoke member. Since the coil 7 is more remotely positioned from the primary than coil 9, there is more leakage area for it whereby it is less closely coupled to the primary than winding 9.

As is well-known in the art, leading current flowing through a loosely coupled secondary winding tends Vto create additional in-phase flux in the magnetic circuit of that winding. In other words, leading current owing through a loosely coupled winding tends to increase the voltage output of the winding. For this reason, it is ordinarily necessary to provide Ia bridged gap or other linx restriction in the magnetic circuit of a lead circuit secondary. However, by positioning the lag secondary 9 between the lead secondary 7 and the primary, I obviate the need for such a gap in the present ballast. The lagging current ilowing in the secondary 9 during lamp operation creates a magnetomotive force that vopposes the ux created by the primary 6 and thereby increases the reluctance of mutual flux path between the primary 6 andthe lead secondary 7. The primary ilux, instead of ii'nding .a low reluctance path to link the coil 7, rather tends to leak across the air gap in the region of the lag secondary 9, whereby a decoupling effect is provided between the primary 6 and the lead circuit secondary 7. In Oneembodiment Vot my invention including the illustrated arrangement of the windings, l have found that the voltage in the lead circuit secondary 7 rises only 33 percent from open circuit to operating conditions. This voltage rise is appreciably` less than that which would occur without the lag )circuit coil 9 between it andthe primary 7. At this condition, an insuiricient flux is created in the region of the secondary 7 to cause any considerable saturation of the winding leg 4 under secondary 7. Thus, the coil 7 presents a high ballasting impedanceduring operationj and together with the capacitor 16 serves to Vballast the lamps S and 51.

Without the positioning of the lag circuit secondary 9 between the lead circuit secondary 7 and the primary, the leading current in coil 7 together with the primary flux would very likely cause considerable saturation of the winding leg beneath the coill 7, thereby greatly reducing its impedance and allowing an over large current to flow in the lead circuit. Succinctly stated, the lag circuit secondary 9 by its magnetomotive force increases the l reluctance ot the mutual ux path between the primary 6 and thelead secondary 7 `at the point in each half cycle of operation` at which the .lead secondary and the primary wouldotherwise saturate the winding leg beneaththe lead secondary. By this eiect, the lag secondary 9 prevents the primary and the lead secondary 7 from saturating the winding leg beneath the lead secondary and thereby reduces its ballasting impedance. As a result,`no bridged gap or other restricted portion is needed in the winding leg in the region of the lead secondary 7.

Referring to the lag circuit, it will be understood that in order to obtain sufficient voltage for starting the lamp 52 in the lag circuit, the coil S must include a relatively large number of turns. However, unless a restriction is provided in the magnetic circuit of the secondary 8, its

inductive reactance or impedance will be such ias to limit of the secondary 8 and thereby causes it to present the desired impedance during operation. Besides determining the impedance of the winding S, the bridged gap also has the elect of reducing its generated voltage from open circuit to operating condition. However, I have found that the voltage in the other lag secondary 9 tends to go up somewhat from the open circuit conditions to operating conditions due to the effect of the lead circuit, whereby suliicientrvoltage is provided in the lag circuit during operation. The leakage legs 10, of course, pro.

vide a shunt path for the primary flux between the secondary 8 and the primary'6-during operation. Due to the impedance value of the coil 8 as determined by the bridged gap, together with the ris'e in voltage in the other lag secondary 9 when operating current -is flowing in both circuits, a current is produced in the lag circuit which is about the same magnitude as that in the lead circuit, thereby a good current balance is provided between the lamps with their light output being relatively uniform. i

From all of the above, it will be seen that I have provided an improved ballast for use with three fluorescent desirable for rapid start lamps.

lamps. This ballast provides operation of the lamps at a high power factor and with a good current balance` between the lamps. Further, by reason of the side by side relationships oi the winding within the core, the ballast may be relatively shallow in both height and width. This is, of course, Ydesirable for use with most lighting fixtures. Also, the ballast may utilize the same core as is used for certain two-lamp ballasts for operating instant start lamps. Thus, no design, tooling or other expense is involved for thecore, whereby the manufacturing cost of the ballast is very favorable.

In considering the operation of the lead and lag circuits, it will be noted that it is desirable for their proper reduction in the heating current does not, however, aect lamp operation or lamp life to an appreciable extent, and is much better in that regard than would be the increased heating current created if the heating windings 38 and 39 were wound over the other lag secondary 9. As pointed out above, the ilux linking secondary 9 is somewhat greater during lamp operation than during starting whereby if the lag circuit heating windings were associated with it, the heating current would 4increase after the lamps werestartedl This would' ordinarily quite adversely aiiect lamp life. It is generally impractical to wind the lag 'cir'- cuit heating windings over the primary since this would increase the number of leads`and connections required within the ballast, and alsok because of other problems,` such as insulating the heating windings from the primary anda lack of space in the primary winding of the core.

. Referring now to Figs. 1 land 2, I have shown therein a pair of starting aid resistors 42 and 43 through whichdesirable that the gas in the lamp envelope be ionized' around one or both of the cathodes. To effect such `ionization, the capacitance between the cathodes and the metallic fixture S is used to pass an auxiliary current from the cathode of the lamp to be ignited to the fixture whereby the gas is ionized in the region of the cathode. The resistors 42 and 43, which are of high resistance in the order of two megohms, appear in the circuits for creating these auxiliary currents as follows:

Referring first to the lag current, it will be seen that the resistor 43 ties the upper end of the secondary 8. to the ballast case 53 which is itself grounded tothe fixture through the case ground 44 and the fixture ground 6. Normally, of course, the grounding connection between the case and the fixture is accomplished simply through the bolting of the case to the fixture. Since the upper end of winding 8 is at ground potential, the full voltage'of the windings S and 9 thereby appears between the cathode 37 and the fixture 5 through the case ground 44 and the fixture ground 6. Normally, of course, the grounding connection between the case and the fixture is accomplished simply through the bolting of the case to the fixture. Since the upper end of winding 8 is at ground potential, the full voltage of the windings 8 and 9 thereby appears between the cathode 37 and the fixture 5 at the same voltage as it is initially applied across the cathodes and 37. With this voltage between the cathode 37 and the fixture, a small current thereby flows from the cathode 37 to the fixture through the distributed capacitance between them. This small current ionizes the gas around the cathode 37, and this ionization together with the potential applied between the cathodes is effective to ignite lamp 4. After the lamp starts, the current flowing through the auxiliary circuit is very minor compared to that between the lamp cathodes, whereby its effect on lamp operation is negligible.

Referring next to the lead circuit, it will be seen that with lead 14 connected to the grounded side 15 of the power supply, the Voltage of the lead s'econdary 7 will be applied between cathode 22 of lamp 51 and the fixture through capacitor 32 when power is first applied to the ballast. This will cause a small current to flow between the cathode 22 and the fixture ionizing the gas around the cathode. This, together with the voltage across the lamp cathodes causes it to ignite, and once the lamp S1 is ignited, the auxiliary current is negligible relative to the lamp circuit current between the cathodes. The same effect also occurs with regard to cathodes of lamp 50 to -aid it in igniting once lamp 51 has fired.

Now, however, suppose that the ballast is to operate from an ungrounded power supply. in this instance the resistor 42 appears in the starting aid circuit for the lead circuit lamps. The resistor 42, as shown, ties the primary lead 14a to the lag circuit heating winding 38 and the resistor 43 in turn ties the winding 38 to the ballast case S3 and thereby to the fixture 5. Thus, when power is first placed on the ballast, the combined voltages of the primary 6 and the secondary 7 appear between cathode 22 of lamp 51 and the conductive fixture 5. The same starting aid effect is again secured, i.e., the gas around cathode 22 is ionized by a small current ow between the cathode and the fixture to ionize the gas around the cathode. After lamp 51 is started, the gas around the cathodes of lamp 50 is likewise ionized by this circuit to aid in starting lamp 50.

It will be understood that due to the very high resistance of resistors 42 and 43, no shock hazard is introduced into the ballast due to the provision of the starting aid circuits. l

While in accordance with the patent statutes I have described what at present is considered to be the preferred embodiment of my invention, it will be obvious to those skilled in the art that various changes and; modifications may be made thereinwithout departing from the invention and it is therefore intended in the appended claims to cover all such modifications as fall within the true spirit and scope of the invention:

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

l. Ballast apparatus for starting and operating three tiuorescent lamps comprising a high reactance transformer having a magnetic core with an elongated winding leg and an outer yoke member, a plurality of windings disposed on said winding leg in side by side relationship, said windings including a primary winding for connection to an alternating current source, a lead circuit secondary winding and a pair of lag circuit secondary windings, a capacitive reactor, said lead circuit secondary winding being connected to said capacitive reactor in series circuit relation and to said primary winding in autotransfermer relation to form a lead circuit for operating two of said lamps with leading current, said lag circuit secondary windings being electrically isolated from said primary winding and being serially interconnected to form a lag circuit for operating the other of said lamps with lagging current, one of said lag circuit secondaries being located on said winding leg between said primary winding and said lead circuit secondary winding and the other of said lag circuit secondary windings being located on the opposite side of said primary winding, and said winding leg having a bridged gap beneath said other lag secondary winding, whereby said windings are effective to operate said lamps in said lead and lag circuits with a good current balance therebetween.

2. The combinaton of claim l in which said yoke member has a iiux leakage leg projecting toward said winding leg between said primary winding and said other lag circuit secondary Winding.

3. Ballast apparatus for starting and operating three fluorescent lamps of the heated cathode type, comprising a high reactance transformer having a magnetic core with an elongated winding leg and an outer yoke member, a plurality of windings disposed on said winding leg in side by side relationship, said windings including a primary winding for connection to an alternating current source, a lead circuit secondary winding and a pair of lag circuit secondary windings, a capacitive reactor, said lead circuit secondary winding being connected to said capacitive reactor in series circuit relation and to said primary winding in autotransformer relation to form a lead circuit for operating two of said lamps with leading current, said lag circuit secondary windings being electrically isolated from said primary winding and being serially interconnected to form a lag circuit for operating the other of said lamps with lagging current, one of said lag circuit secondaries being located on said winding leg between said primary windin g and said lead circuit secondary winding and the other of said lag circuit secondary windings being located on the opposite side of said primary winding, and said winding leg having a restricted portion in the region of said other lag secondary winding, whereby said windings are effective to operate said lamps in said lead and lag circuits with a good current balance therebetween, and means for heating the cathodes of said lamps comprising a plurality of heating windings located on said winding leg in the region of said primary winding for heating the cathodes of the two lamps connected in said lead circuit, and a pair of heating windings located on said winding leg in the region of said other lag secondary for heating the cathodes of the lamp connected in said lag circuit.

4. Ballast apparatus for starting and operating a plurality of fiuorescent lamps comprising a high reactance transformer having a magnetic core with an elongated winding leg and an outer yoke member, a plurality of windings disposed on said winding leg in side by side relationship, said windings including a primary winding for connection to an alternating current source, a lead circuit secondary winding and a pair of lag circuit secondary windings, a capacitive reactor, said lead circuit secondary winding being connected to said capacitive reactor in ananas series circuit relation to form a lead'circujit for operating at least 'one of said lamps -With leading current, saidl lag saidv leadand .lag circuits witha `good current balance therebetween. Y v

5. Ballast apparatus for starting and operating a plurality of fluorescent lamps comprising a high reactance transformer having a magnetic, core with an elongated winding leg and an outer yoke member, a first lag'circuit secondary winding, a primary winding, a second lag circuit secondary winding and a lead circuit secondary winding arranged on said winding leg in the order named, a

capacitivereactor, said lead vcircuit secondary being cennected to said capacitor reactor in series circuit relationY to form a lead circuit for operating at least one of said lamps with `leading current, said lag circuitY secondary` windings being serially interconnected to form a lag c ircuit for operating at least a `second ofsald lamps with.

lagging current, said winding leg having a .restricted .por-l tion in the region of said first lag circuit secondary wind-V ing and being otherwise of substantially" the same crossv section throughout its length.

6. Ballast apparatus for starting and operating threefluorescent lamps of the heated cathode type comprising a high reactance transformer having a magnetic core with an elongated winding leg and an outer yoke member, a irst lag .circuit secondary winding, la Primary Winding, a second lag circuit secondary winding and a lead'l circuit secondary winding arranged on said winding leg 1n the ondary vwindingsrto'said `casing and to one end of said primary-winding.

'18, Ballast apparatus for starting `and operating three I fluorescent lamps comprising a high reactance transformer having a.V magnetic core with an elongated winding leg and an outer yoke member, a plurality of windings disposed "on said winding leg in side by side relationship, said windings including aprimary winding for connection to lan alternating current source,Y a lead circuit secondary winding and a pair of lag circuit secondary windings, a capacitive reactor, said lead circuit secondary winding being connected to said capacitiveV reactor in series circuit relation and to said primary winding in autotransformer relationto form -a lead circuit for operating two of said lamps wit-h leading current,said lag circuit secondary windings being electrically isolated from said primary winding'and being serially interconnected to forni a lag circuit for operating the other of said lamps with lagging current, one of said lag circuit secondaries being located oni-said winding leg between said primary winding and said` lead circuit secondary winding and the other of said lag circuit secondary windings being located on the opposite jside of said primary, and means for heating the i V- cathode of said lamp comprising a plurality of heating windings located'on said winding leg in the region of said primary for heating the cathode of the lamps connected order named, a capacitive reactor, said lead circuit secondary being connected to said primary winding in autotransformer relation and to capaci-tor reactorin series circuit relation to form a lead circuit for operating two of said lamps with leading current, said lag circuit secondary winding being serially interconnected to form a -lag circuit for operating the other of said lamps with lagging current, said winding leg having a bridgedgap in the region of said iirst lag circuit secondary winding and being otherwise of substantially the same cross-section throughout its length, and means for heating the cathodes of said lamps comprising a plurality .of heating windings located on said winding leg in the region of said primary winding for heating the cathodes of the two lamps connected in said lead circuit, anda pair or heating windings located on said winding leg in the region of said other lag secondary Ifor heating the cathodes of the lamp connected in said lag circuit. n

7. Ballast apparatus for starting and operating a plurality of fluorescent lamps comprising a high reactance transformer having a magnetic core with an elongated winding leg and an outer yoke member, a iirst lag circuit secondary winding, a primary winding, a second lag circuit secondary winding and a lead circuit secondary winding arranged on said winding leg in the order n amed, a capacitive reactor, said lead circuit secondary being connected to said capacitor reactor in series circuit relation to form a lead circuit for operating at least one of said lamps with leading current, said lag circuit secondary winding being serially interconnected to form a lag circuit `for operating at least a second of said lamps with lagging current, said winding leg having a restricted por tion in the region of said lfirst lag circuit secondary winding and being otherwise of substantially the same crosssection throughout its length, a conductive casing enclosing said high reactance transformer and said capacitive reactor, and a pair of high ohmage resistors respectively connecting one end of one of the l-ag circuit secinesaid lead circuit, and a pair of heating windings 1ocated on said winding leg in the region of said other lag circuit-,secondary winding for heating the cathodes of the lamp connected in said lag circuit. i

9. Ballast Yappartus vfor starting and operating a plurality of iiuorescent lamps comprising a high reactance transformer having a magnetic core with an elongated winding `legand an outer yokemember, a first lag circuit secondary winding, aprimary winding, a second lag circuit secondary winding and a lead circuit secondaryv windingairanged on said winding leg in the order named, a leakage leg on said core located between said lrst lag secondary winding and said primary winding, a capacitive reactor, said lead circuit secondary being connected to said capacitor reactor in series circuit relation to form a lead circuit `for operating at least one of said lamps with leading current, said lag circuit secondary winding being serially interconnected Ato `form a lag circuit for operating at least a second of said lamps with lagging current, said winding leg having a restricted portion in the region of'said iirst lag circuit secondary winding and being otherwise of substantially the same cross-section throughout its length.

10. Ballast apparatus for starting and operating a plurality of liuorescent lamps comprising a high reactance transformer having a magnetic core with an elongated winding leg and an outer yoke member, a rst lag circuit secondary winding, a primary Winding, a second lag circuit secondary winding and a lead circuit secondary winding arranged on said winding leg in the order named, Ia capacitive reactor, said lead circuit secondary being connected to said capacitor reactor in series circuit relation to form a lead circuit for operating at least one of said lamps with leading current, said lag circuit secondary winding being serially inter-connected to for-m a lag circuit -for operating at least a second of said lamps with lagging current, and a leakage leg on said core located between said rst lag circuit secondary winding and said primary winding.

ll. Ballast apparatus for starting and operating three fluorescent lamps comprising a high reactance transformer having a magnetic core with an elongated winding leg and an outer yoke member, a plurality of windings disposed on said winding leg in side by side relationship, said windings including a primary Winding for connection to an alternating current source, a lead circuit secondary winding and a pair of lag circuit secondary windings, a

capacitive reactor, said lead circuit secondary winding being connected to said capacitive reactor in series circuit relation and to said primaryrwinding in autotransformer relation to form a lead'circuit for operating two of said lamps with leading current, said lag circuit secondary windings being electrically isolated from said primary winding and being serially interconnected to form a lag circuit for operating the other of said lamps with lagging current, one of said lag circuit secondaries being located on said winding leg -between said primary winding and said lead circuit secondary winding and the other of said lag circuit secondary windings being located on the opposite side of said primary winding, and said winding leg having a restricted portion in the region of said other lag secondary winding, and said core having a leakage leg between said primary winding and said one secondary windings, whereby said windings are elective to operate said lamps in said lead and lag circuits with a good current balance therebetween.

l2. Ballast apparatus `for starting and operating three fluorescent lamps comprising a high reactance transformer having a magnetic core with an elongated winding leg and an outer yoke member, a plurality of windings disposed on said winding leg in side by side relationship, said windings including a primary winding for connection to an alternating current source, a lead circuit secondary winding and a pair of lag circuit secondary windings, a capacitive reactor, said lead circuit secondary winding *being connected to said capacitive reactor in sexies circuit relation and to said primary winding in autotransformer relation to form a lead circuit for operating two of said lamps with leading current, said lag circuit secondary windings being electrically isolated from said primary winding and being serially interconnected to form a lag circuit for operating the other of said lamps with lagging current, one of said lag circuit secondaries being located on said winding leg between said primary winding and said lead circuit secondary winding and the other of said lag circuit secondary Wind- 12 ings being located on the opposite side of said primary, whereby said windings are effective to operate said lamps in said lead and lag circuits with a good current balance therebetween.

13. Ballast apparatus for starting and operating a plurality of fluorescent lamps comprising a high reactance transformer having a magnetic core with an elongated winding leg and an outer yoke member, a plurality of windings disposed on said winding leg in side by side relationship, said windings including a primary winding for connection to an alternating current source, a lead circuit secondary winding and a pair of lag circuit secondary windings, a capacitive reactor, said lead circuit secondary winding being connected to said capacitive reactor in series circuit relation to form a lead circuit for operating at least one of said lamps with leading current, said lag circuit secondary windings being serially interconnected to -forrn a lag circuit for operating at least a second of said lamps with lagging current, one of said lag circuit secondaries being located on said winding leg between said primary 'winding and said lead circuit secondary winding and the other of said lag circuit secondary windings being located on the opposite side of said primary winding, and said winding leg having a restricted portion in the region of said other lag secondary winding, whereby said windings are elfective to operate said lamps in said lead and lag circuits with a good current balance therebetween, and a conduc-tive casing enclosing said high reactance transformer and said capacitive reactor, and a` pair of high ohmage resistors respectively connecting one end of one of Ithe lag circuit secondary windings to said casing and to one end of said primary winding.

References Cited in the ile of this patent UNITED STATES PATENTS 2,788,469 Feinberg Apr. 9, 1957

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