US3089980A

US3089980A - Ballast apparatus for starting and operating electric discharge lamps

Info

Publication number: US3089980A
Application number: US114068A
Authority: US
Inventors: Frank A Neusbaum
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1961-06-01
Filing date: 1961-06-01
Publication date: 1963-05-14
Anticipated expiration: 1980-05-14

Description

y 4, 1963 F A. NEUSBAUM 3,089,980

BALLAST APPARATUS FOR STARTING AND OPERATING ELECTRIC DISCHARGE LAMPS Filed June 1, 1961 2 Sheets-Sheet 1 May 14, 1963 F. A. NEUSBAUM 3,089,980

BALLAST APPARATUS FOR STARTING AND OPERATING ELECTRIC DISCHARGE LAMPS 2 Sheets-Sheet 2 Filed June 1, 1961 [/7 149/? 5'0): Framz A. A/eusaum,

United States Patent 3,089,980 BALLAST APPARATUS FOR STARTING AND ()PERATING ELECTRIC DISCHARGE LAMPS Frank A. Neusbauni, Danville, Ill, assignor to General Electric Company, a corporation of New York Filed June 1, 11961, Ser. No. 114,063 llti (Ilairns. (Cl. 315-97) This invention relates to ballast apparatus for starting and operating electric discharge lamps and more particularly to such a ballast apparatus for starting and operating gaseous discharge lamps such as fluorescent lamps employing an auxiliary starting aid circuit arrangement.

In most fluorescent lamp lighting applications, the ballast apparatus for the lamp is mounted within the lamp fixture. Each fluorescent lamp is positioned in a predetermined spaced relationship with the fixture so that a capacitive effect is produced between the lamp and the fixture. Although a grounded conductive strip such as a narrow ribbon of silver graphite deposited on the lamp bulb may be used in the same manner as a lamp fixture, the fixture itself is generally used as a starting aid for the lamp because it is a relatively inexpensive and simple arrangement.

The effect of grounding the fixture or conductive plate and grounding one side of the low potential side of the ballast circuit is to place the lamp fixture in electrical connection with the lova potential side of the ballast circuit. Further, it will be understood that if the low potential side of the distribution line is grounded as is the case in a normally grounded distribution system and if the ballast case and fixture are grounded, no auxiliary starting aid device will be needed in autotransformer connected ballast circuits. In the event the distribution system is not effectively grounded, or in the event that the lamp fixture is not grounded, a starting aid resistor is provided so that the low potential side of the ballast circuit is in electrical connection with the fixture and the auxiliary starting aid circuit forms a complete loop. The impedance provided by the resistor prevents a lethal current flow to the ballast case. Ballast circuits which utilize isolated primary designs must use some auxiliary means to return one end of the secondary circuit to the ballast enclosure, regardless of whether the primary distribution system is grounded.

The auxiliary starting aid circuit or loop is completed through ground from the conducting fixture to the low potential side of the primary winding of the ballast transformer. The low potential side of the primary is usually grounded through a resistor to the ballast case. Since the ballast case is generally connected to the lamp fixture, the fixture is thereby connected in electrical circuit with the low potential side of the primary winding. Because of the high impedance of the grounding resistor and of the capacitive coupling between the lamp and fixture, only a small amount of current will fiow in the starting aid circuit from the electrode to the fixture. However, this current is sufiicient to increase substantially the ionization of the gas in the vicinity of the lamp electrode. The increased ionization potential in the vicinity of the lamp electrodes permits the lamp to be started with lower starting voltages applied across the lamp terminals. The starting voltage at the output terminals of the ballast transformer is concurrently placed across the electrodes of the lamp with the starting aid potential until the lamp is ignited. Once the lamp has ignited, the starting aid circuit is substantially ineffective in the circuit because of the high impedance of the capacitive coupling between the lamp and fixture.

It is desirable that a ballast apparatus be provided wherein the starting aid circuit will provide a suflicient 3,089,980 Patented May 14, 1963 ionization potential voltage so that the ballast apparatus can be operated from a grounded or ungrounded power supply in conjunction with a grounded or ungrounded fixture. For these various grounded and ungrounded conditions of operation which are not infrequently encountered in practice, the starting aid resistor has not been entirely satisfactory. For example, in an installation where the primary winding of the ballast transformer is connected to an ungrounded power supply and the ballast case is ungrounded, the starting aid potential was actually decreased by an auxiliary starting aid circuit utilizing a resistor connected between the low potential end of the primary and the ballast case. Thus, in such an installation the starting resistor has a detrimental effect on starting. Further, the starting aid resistor is an additional component of the starting aid circuit and adds to the cost of the ballast apparatus. From a standpoint of economy, it is, of course, desirable to reduce the number of components used in any electrical circuit.

Accordingly, it is a general object of my invention to provide a new and improved auxiliary starting aid arrangement for a ballast apparatus for operating one or more gaseous discharge lamps.

Another object of my invention is to provide an improved auxiliary starting aid circuit arrangement in a ballast apparatus wherein the need for an auxiliary starting aid resistor is eliminated.

A further object of my invention is to provide a new and improved auxiliary starting aid circuit arrangement in a ballast apparatus wherein an increased starting aid potential is provided when the ballast circuit is operated from a grounded and ungrounded power supply.

Briefly stated, in accordance with one aspect of my invention, I have provided a ballast apparatus having a high leakage reactance transformer and a power factor capacitor connected in circuit with the secondary winding thereof. The capacitor container is connected to ground and the reactive impedance developed between the capacitor container and the capacitor outer foil is utilized in an auxiliary starting aid circuit. The lamp or lamps energized by the ballast apparatus are positioned in close proximity to a conducting fixture and disposed in capacitive relationship therewith. The auxiliary starting aid circuit applies at least the voltage developed across the secondary winding across the lamp electrode and the fixture capacitively coupled therewith. The grounded connection to the capacitor container solely provides a return path for the auxiliary starting aid current to the ballast apparatus. When the lamp is started, the reactive impedance between the capacitor case and the capacitor outer foil is sufficient to prevent any significant amount of current flow out of the ballast circuit.

The subject matter which I 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 mode of operation, together with further objects and advantages thereof, may be best understood by reference to the following description taken in conjunction with the accompanying drawings in which:

FIG. 1 is a schematic diagram ballast apparatus incorporating the features of the present invention;

FIG. 2 is a plan view of the ballast apparatus shown schematically in FIG. 1 in which the circuit connections have been omitted;

FIG. 3 is a schematic diagram of an improved ballast apparatus for operating a pair of serially connected discharge lamps in accordance with the invention;

FIG. 4 is a plan view of the ballast apparatus shown schematically in FIG. 3 wherein the circuit connections have been omitted; and

FIG. 5 is a view partly in section of a power factor capacitor such as is conventionally employed in a ballast apparatus with the capacitor assembly partially-unrolled.

Referring now to the drawings and more specifically to FIG. 1, a schematic circuit diagram of one form of applicants invention for operating a hot cathode type of fluorescent lamp L is shown. A ballast apparatus is contained within a ballast case 11 represented by dashed lines. The ballast apparatus 113 includes a high reactance transformer 12, a power factor capacitor 15 having a metallic or conductive container 9, and output leads 14, 15 connected to

cathodes

16, 17 of lamp L. A grounded conductive plate is identified generally in FIG. 1 by reference numeral 18 and in most applications is the lighting fixture. Lamp L is positioned in proximity to the conductive plate 18 so as to be icapacitively coupled therewith. A spacing of approximately /8 of an inch may be employed between the lamp L and the conductive plate 18.

The high reactance ballast transformer 12 includes a magnetic core 19, a primary winding P, a secondary winding S, cathode heating windings H H a magnetic shunt 20 and input terminal leads 21, 22. As shown in FIG. 2, the primary winding P and the secondary winding 5 are placed side by side on a central winding leg 23 of the mag netic core 19 and are separated by magnetic shunts 20. It will be appreciated that the leakage reactance of the ballast transformer 12 may be readily increased by the inclusion of a high reluctance leakage path or shunts of magnetic material between the primary winding P and the secondary winding S. In the exemplification of the invention shown in FIGS. 1 and 2, the flux leakage path is formed of inserted shunts 20. A high leakage reactance transformer is normally required in ballast circuits in order that the current How in the lamp circuit be limited because the discharge lamp L has a negative resistance characteristic. It will be understood that flux leakage paths may be formed either through nonmagnetic material, such as air, or through magnetic material by the provision of projecting shunt legs integrally formed with the yoke sections or insertable shunts 21) as are employed the illustrative embodiment of the invention.

Referring again to FIG. 2, it will be seen that magnetic core 19 has a central winding leg 23 and

yoke sections

24, 25 which are firmly held in assembled relation with the central leg 23 by the

clamping elements

26, 27. Primary winding P and cathode heating windings H H are included in coil assembly 28. Coil assembly 29 which includes the secondary winding S is disposed on the central winding leg 23 alongside of and spaced from coil assembly 2S.

Ballast apparatus 1% is housed in an elongated conductive ballast case 11 which is covered with a cover plate 30, only portions of which are shown. The capacitor 13 and container 9 are disposed at the other end of the ballast case 11 and container 9 is connected to the ballast case 11 by lead 31. As shown in FIG. 2, one end of the lead 31 is attached to the capacitor container 9 by some suitable attaching means such as solder and at the other end it is attached to an eyelet portion 32. When the cover plate 30 is assembled with ballast case 11, the lead 31 is engaged between eyelet portion 32 and the cover plate 30. Since the ballast case 11 is generally secured to a lamp fixture, which is shown schematically in the circuit diagram of PEG. 1, as the conductive plate 18 connected to a ground 33, the ballast case is also substantially at ground potential as shown by the connection of ballast case 11 to ground in FIG. 1.

As shown in FIG. 1, the capacitor container 9 is represented schematically by the dashed rectangle 9 and is connected by lead 31 to the ballast case 11. The reactive impedance developed between the capacitor container 9 and the capacitor outer foil of capacitor 13 is represented schematically in FIG. 1 by a capacitor 35 and connections 36, 37 shown in dashed lines. In effect, by connecting the capacitor container 9 to the grounded ballast case 11 or any other suitable ground, I have discovered that such an arrangement is equivalent to connecting one end of the secondary winding S in series circuit with one plate of the capacitor 35, the other plate of which is connected to ground. Thus, one end of the secondary winding S is grounded through a capacitor by connecting the container 9 of capacitor 13 in electrical circuit with ballast case 11, and the capacitive impedance in tr e circuit is isufficient to prevent any appreciable current flow from the ballast apparatus 10 to ground. Capacitor 13 has sufficient capacitive reactance as compared with the inductive reactance of a ballast transformer 12 to draw a leading current through the secondary winding S. A bleeder resistor R may be connected across capacitor 13, if desired.

As shown in FIG. 1, the primary winding P has a pair of input terminal leads 21, 22 for connection to a suitable alternating current supply line shown schematically by the dashed lines 39, 4'19, the low potential side being shown by the supply line at; which is grounded. Although the invention is described in connection with an alternating current supply that has one side grounded in accordance with the standard practice for normal residential and commercial power distribution systems, the ballast apparatus 10 of the present invention can be operated from supply sources which are not grounded.

During operation, the

cathodes

16, 17 of fluorescent lamp L are continuously supplied with cathode heating current by the cathode heating windings H H which are closely coupled with the primary winding P and connected in circuit with the

cathodes

16, 17 by

leads

14, 41 and 15, 42, respectively. The high potential end of the secondary winding S is connected with lamp L by the circuit means which includes the output lead 14. The low potential end of the secondary winding S is connected with lamp L by circuit means which includes the capacitor 13 and output lead 15.

In FIG. 3, -I have illustrated a ballast apparatus 54) suitable for operating a pair of fluorescent lamp L L capacitively coupled with a conductive plate or fixture 48 connected to ground 49. The ballast apparatus 50 includes the ballast case 51 shown schematically by the dashed rectangle, a high reactance ballast autotransformer 55, a power factor capacitor 56 and a starting capacitor 58 having a container 57, and output leads 59, 66.

The high reactance ballast transformer 55 includes a primary winding P a secondary winding S inductively coupled therewith on magnetic core 61, cathode heating windings H H H and magnetic shunts 62. A pair of input terminal leads 63, 64 are connected across primary winding P and are provided for connection to a suitable alternating current supply shown schematically by the dashed lines 65, 66, the low potential side of the power supply line 65 being identified by the ground connection 52. Cathode heating winding H is connected in circuit with the

cathodes

67, 68 by leads 69, 7t) and cathode heating windings H H are connected in circuit with cathodes 71, by leads 613, '72 and 59, 73, 74, respectively. Cathode heating winding H is an extension winding of primary winding P and cathode heating windings H H are tightly coupled with the primary winding P and may, if desired, be wound directly over the primary winding P The reactive impedance between

capacitors

56, 58 and container 57 and the outer foils of

capacitors

56, 58 is represented schematically by a capacitor 76 and

connections

77, 78 shown in dashed lines. Thus, in the exemplification of the invention shown in FIG. 3, the starting capacitor 53 and the power factor capacitor 56 are preferably contained within the same metal container 57, and the container 57 is connected by lead 83 to the ballast case 51, which is connected to a ground 47.

As shown in FIG. 4,

capacitors

56, 58 are contained in a single container 57 provided with three

terminals

80, 81, 82. The capacitor container 57 is connected in electrical circuit with the ballast case 51 by lead 83, which is attached to the ballast case 51 by solder at one end and at the other end is connected to an eyelet 84. When cover plate 85 of the ballast case is attached, the end of lead 83 at the eyelet 84 is brought in good electrical contact with the ballast case 51.

Continuing with the description of the components of the ballast apparatus Ell, as they are shown in MG. 4, it will be seen that cathode heating windings H H2, H and the primary winding P are included in coil assembly 85 mounted on a central winding leg 86. Secondary winding S is included in coil assembly 87 arranged on winding leg 86 adjacent to the coil assembly 81*? and separated therefrom by shunts 62. The shunts 62 provide a leakage path in the magnetic core 61 between the primary winding P and the secondary winding S It will be noted that the magnetic core 61 has a pair of yoke sections 88, 39 which are held in as sembled relation with the central winding leg 86 by clamping elements $4), 91 so that a closed magnetic circuit is formed.

The capacitors employed in the ballast apparatus of the invention are conventional static capacitors having liquid or solid dielectrics and a capacitor roll with interleaved sheets of paper and metallic foil, the roll and the dielectric being sealed in a metal container. Since the metal container is separated from the outer metallic foil by the dielectric within the container, a capacitance exists between the container and the outer metallic foil of the capacitor roll. The amount of this capacitance is a function of the area of the two surfaces, the spacing between the surfaces and the properties of the dielectric. I have discovered that the capacitance between the outer foil and the metal container is of sulficient magnitude in static capacitors normally used in ballasts and this capacitance can be eifectively utilized in the starting aid circuit by connecting the container to ground.

Referring now to FIG. 5, I have illustrated a conventional capacitor assembly 93 constructed in the usual manner. As is shown in FIG. 5, the assembly 93 is constructed of a capacitor roll 94 comprised of

metallic foils

95, 96, such as aluminum, in which metallic foils are interleaved with sheets of

paper

97, 98 to form foil layers 95, 96 separated substantially only by the paper layers.

As shown schematically in FIG. 1, the upper and lower plates of the capacitor correspond to the foil layers 95, 96, respectively. Tap straps 99, 160 are brought out from the foil layers d5, 96 and connected to the

outer terminals

101, 102. The wound assembly of foil layers 95, 96 and

paper dielectric spacers

97, 98 are placed in a metal container 163 having a cover 1% arranged thereon so as to hermetically seal the capacitor roll 94 and dielectric material 195. Because of the spacing which necessarily exists between the outer foil layer 96 and capacitor container 103, the capacitance exists between these two metallic surfaces since they are separated by dielectric material M5. As previously mentioned, the amount of capacitance depends upon the area of the surfaces, the spacing and the type of dielectric material used. In accordance with the invention, this capacitance is utilized to solely provide the impedance that is required in the starting aid circuit in FIGS. 1 and 3.

The operation of the circuit shown in FIG. 1 will now be more fully explained. When a voltage is applied to the input terminal leads 21, 22 of primary winding P, a voltage will be induced in the secondary winding S as determined by the respective turns ratio of the primary winding P and secondary winding S. The voltage across the secondary winding S is applied across lamp L by means of the output leads 14, connected in circuit thereto. Further, the

cathodes

16 and 17 are simultaneously supplied a heating current by cathode heating windings H H respectively. Also, the auxiliary starting aid circuit causes a potential to be applied in the immediate vicinity of cathode 16. The current flow in the auxiliary starting aid circuit follows a path from the cathode 16 to the capacitively coupled conductive plate 13, ground 33, lead 31, capacitor container 9, to secondary winding S, output lead 14 and to cathode 16. Thus, the lead 31 connected to capacitor container 9 solely provides a current path for the auxiliary starting aid current to the ballast apparatus. Due to the relatively high impedance presented by the capacitive reactance between the capacitor container 9 and the outer foil of the capacitor 13 and the high capacitive reactance between lamp L and the conductive plate 18, only an insignificant current in the order of a few microamperes will flow in this circuit. However, this current is sulficient to substantially increase the ionization of the gas in the vicinity of the cathode 16 and in conjunction with the voltage applied by the secondary winding S at the output leads 14, 15 causes lamp L to start.

When the lamp has started, the starting aid circuit is substantially ineffective in the operating circuit and any current flow in this circuit is insignificantly small as compared with the current flowing through the lamp L.

In the operation of the ballast apparatus 50 shown in FIG. 3, input terminal leads 63, 64 are connected across supply lines 65, 66 energized from a suitable supply of alternating current such as a 120 volt, 60 cycle commercial supply. Voltages are immediately induced in the cathode heating windings H H H and a cathode heating current is supplied to the

cathodes

67, 68, 71, of lamps L and L Also, the open circuit voltage developed across the primary winding P and the secondary winding S of the ballast transformer 55 is applied across lamp L the turns ratio of the transformer 55 being such that the open circuit voltage is of sufiicient magnitude to initially start lamp L At the same time, the auxiliary starting aid circuit applies the voltages across primary winding P and secondary winding S to cathode 71 of lamp L which is in capacitive relation with the conductive plate or fixture. A return ground with the conductive plate 48 is completed through ground 49 to either the ground 47 to which capacitor container 57 is connected or the ground of the low potential line 65.

After lamp L has started, the voltage across the starting capacitor 58 is applied across lamp L Lamp L also being in close proximity to the conductive plate 48 has an ionization potential applied to cathode 67 by the auxiliary starting aid circuit. The gas in the vicinity of the cathode 67 will ionize causing lamp L to become conductive and the open circuit voltage between cathodes 67, '75 causes a breakdown of the gas contained within lamp L thereby igniting lamp L The starting capacitor 58 has sulficient impedance so that no appreciable operating current will flow through it when both lamps L and L are ignited. Lamps L and L are operated in a series circuit relationship across the primary winding P and the secondary winding S of the ballast transformer 55. After the lamps L and L are ignited, only a negligible amount of current will flow from the lamp cathodes to the conducting fixture because of the high impedance of the capacitive coupling between lamps L L and the conductive plate 48.

In order to demonstrate the advantages of the present invention, the ballast apparatus Stl shown in FIG. 3 was constructed and tested by operating a pair of 40 watt fluorescent lamps from a volt, 60 cycle alternating current supply. The high reactance ballast transformer 55 was designed to provide a minimum open circuit voltage of 280 volts across the output leads 59 and 60. A power factor capacitor 56 having a rating of 4 microfarads at 300 volts AC. and a starting capacitor 58 having a rating of .05 microfarad was used. The capacitor container 57 was grounded to the ballast case 51.

During the measurements of the starting aid potential, the primary operating voltage was maintained at 108 volts or at minus 10 percent of the rated operating voltage in accordance with standard procedure. The starting aid voltage measurements were taken with a Rawson peak rectifier and a Rawson electrostatic voltmeter. The starting aid potential was measured by reading the voltage between the ballast case 51 and the output lead 60. For the circuit shown in FIG. 3, the starting aid voltage or potential between cathode '71 and the ballast case 51 was found to be approximately 360 volts when the conductive plate or fixture 48 was not grounded.

By way of comparison, similar starting aid voltage measurements were taken for an identical ballast circuit as shown in FIG. 3 wherein a conventional grounding resistor was connected in circuit with the low potential end of the primary P, and the ballast case 51. With a starting resistor and capacitor container in the circuit grounded, the starting aid voltage corresponding to a voltage of 108 volts across the primary winding was found to be 280 volts. Also, with the starting aid resistor installed but with the capacitor container ungrounded, it was determined that the measured starting aid voltage was approximately 278 volts. Thus, it will be seen that by grounding the capacitor container and by eiminating hte grounding resistor an increase of approximately 28.5 percent is obtained in the starting aid potential.

Where the fixture 4-8 was grounded as shown in FIG. 3, the starting aid voltage was measured at 304 volts with the capacitor container 51 grounded and without a starting aid resistor. By way of comparison, the ballast apparatus with a starting aid resistor connected to the low potential end of the primary P, and with the capacitor container ungrounded was tested. The starting aid voltage was measured at 260 volts. Further, with the starting aid resistor in the circuit and the capacitor container grounded, the starting aid voltage was measured at 262 volts.

Preferably, it was found that the capacitance between the capacitor container 57 and the outer foil of the capacitor should not be less than 880 picofarads. It was found that when the ballast apparatus 59 shown in FIG. 3 was operated from an ungrounded power supply and with the capacitor container 57 grounded that the auxiliary starting aid voltage began to decrease below 880 picofarads. The capacitor container 57 of

capacitors

56, 5% used in the circuit provided a capacitance between the container 57 and the outer foil of capacitors 56, 58' of approximately 1700 picofarads. However, where the circuit was operated with a normally grounded supply, it was noted that variations in the capacitance between the outer foil and container 57 did not have an appreciable effect on the starting aid potential.

From the foregoing description, it will be apparent that the auxiliary starting circuit arrangement of the present invention not only provides a significant improvement in the auxiliary starting aid voltage, but also eliminates the need for a grounding resistor.

It will be understood that while I have illustrated my invention by specific embodiments thereof, the invention has general applicability to ballast circuits which utilize an auxiliary starting circuit to aid in the starting of the fluorescent lamps. Thus, the invention may be employed in ballast circuits used to start and operate rapid start and instant start lamps. It will also be apparent to those skilled in the art that the auxiliary starting circuit arrangement in accordance wiht the invention can be employed in many other ballast circuit configurations other than those which have been illustrated herein by way of exemplification of the invention. While the present invention has been described by reference to specific exemplifications thereof, it is to be understood that modifications may be made by those skilled in the art without actually departing from the invention. It is, therefore, intended in the appended claims to cover all such equivalent variations that 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:

1. A ballast apparatus for starting and operating at least one fluorescent lamp disposed in a capacitive relation with a conductive fixture, said apparatus comprising a high reactance transformer having a primary winding and a secondary winding inductively coupled therewith On a magnetic core, a pair of input terminal leads connected across said primary winding, a circuit means including a pair of output leads for applying the output of said transformer across said lamp, a capacitor serially connected with said secondary winding to cause a leading current to iiow therethrough, a conductive ballast case, said high reactance transformer and capacitor being disposed in said ballast case, said capacitor including a capacitor roll having electrodes of interleaved foil layers and a conductive container for housing said capacitor and disposed in capacitive relation with the outer foil layer and circuit means for connecting said container in electrical circuit relationship with said ballast case, the capacitance between said container and said outer foil layer providing sufiicient impedance during operation to prevent any significant current flow from the apparatus to said ballast case and said circuit means for connecting said container providing the only return path within said ballast case for the auxiliary starting aid current.

2. The ballast apparatus set forth in claim 1 wherein said secondary winding is connected in isolated transformer relationship with said primary winding.

3. Ballast apparatus for starting and operating a gas eons discharge lamp from a source of alternating current, said lamp being mounted in a conductive fixture and disposed in capacitive relationship therewith, said apparatus comprising: a high reactance transformer having a. primary winding and a secondary winding inductively coupled therewith on a magnetic core and a pair of input leads for connection across the alternating current source; a power factor capacitor connected in series circuit relationship with said secondary winding to cause a leading current to flow therethrough, a ballast case, said power factor capacitor and said high reactance transformer being housed in said ballast case, said capacitor including a capacitor roll and a metallic container providing an enclosure for at least said power factor capacitor, circuit means connecting said container in electrical circuit relationship with the ballast case, said circuit means providing the only return path for the auxiliary starting aid current when said alternating current source is not grounded, the capacitive reactance between said capacitor roll and said container providing sufficient impedance to prevent any significant current flow from the apparatus to the ballast case thereby eliminating the need for a grounding resistor, and circuit means including electrical leads for connection across said lamp to apply the output of said high reactance transformer across said lamp.

4. A ballast apparatus for starting and operating at least one fluorescent lamp from an alternating current supply, said lamp being disposed in a capacitive relation with a conductive plate, said apparatus comprising: a high reactance transformer having a primary winding and a secondary winding inductively coupled therewith on a magnetic core, a pair of input terminal leads connected across the primary winding for connection to the alternating current supply, a capacitor connected in series circuit relationship with said secondary winding to cause a leading current to flow therethrough, a ballast case for housing said apparatus, said capacitor having a metallic container and a capacitor roll, said container being spaced from said roll and disposed in capacitive relation therewith and circuit means connecting said metallic container in electrical circuit relation with said ballast case and forming a low potential connection in the starting aid circuit, said capacitive reactance between said capacitor container and said roll providing sufficient reactive impedance to prevent any significant current flow to said ballast case, and said circuit means providing the only return path for the auxiliary starting aid current when said alternating current supply is not effectively grounded.

5. A ballast apparatus for starting and operating a gaseous discharge lamp from an alternating current supply, said lamp being mounted in a conductive fixture and disposed in capacitive relationship therewith, said apparatus comprising: a ballast transformer having a primary winding and a secondary winding inductively coupled therewith on a magnetic core, said secondary winding being in isolated transformer relationship with said primary winding, a pair of input leads for connection across the alternating current supply, said primary winding being connected across said input terminal leads, a capacitor connected in series circuit relationship with said secondary winding to cause a leading current to flow thereto, a ballast case for housing said apparatus, said capacitor having a metallic container and a capacitor roll formed of foil layers and dielectric layers, said roll being disposed in said metallic container, said metallic container being spaced from said roll and capacitively coupled with the outer foil layer of said roll and circuit means connecting said metallic container in electric circuit relation with said ballast case in order to provide a grounded connection for the ballast apparatus in a starting aid circuit, said capacitive reactance between said capacitor container and said outer foil layer providing suflicient reactive impedance to prevent any significant current flow from said ballast transformer to said ballast case and said circuit means providing the only return path for the auxiliary starting aid current from the conductive fixture.

6. A ballast apparatus for starting and operating a pair of fluorescent lamps from an alternating current supply, said lamps being disposed in capacitive relation with a conductive plate so that .an auxiliary starting aid current can flow thereto, said apparatus comprising: a high reactance transformer having a primary winding and a secondary winding inductively coupled therewith on a magnetic core, a pair of input terminal leads connected across the primary winding for connection to the alternating current supply, a power factor capacitor connected in series circuit relationship with said secondary winding to cause a leading current to flow therethrough, a starting capacitor, circuit means including electrical leads for connecting the output of said high reactance transformer across said fluorescent lamps and for connecting said starting capacitor across one of said lamps, said power factor capacitor and said starting capacitor being enclosed in a metallic container and having a capacitor roll formed of interleaved foil layers and dielectric layers disposed in said container, and grounding circuit means connecting said metallic container in electrical circuit relation with said ballast case in order to provide a grounded connection for the ballast apparatus in the auxiliary starting aid circuit, said capacitive reactance between said metallic container and the outer foil layer of said roll providing suflicient impedance to prevent any significant current flow from said ballast apparatus to said ballast case and said grounding circuit means providing the only return path for the auxiliary starting aid current from the conductive plate to the ballast apparatus.

7. A ballast apparatus for starting and operating a pair of serially connected fluorescent lamps from an alternating current supply, said lamps being disposed in capacitive relation with a conductive plate so that an auxiliary starting aid current can flow therethrough, said apparatus comprising: a high reactance transformer having a primary winding and a secondary winding inductively coupled therewith on a magnetic core, a pair of input terminal leads for connection to the alternating current source, said primary winding being connected across said input terminal leads, a capacitor connected in series circuit relationship with said secondary winding to provide a leading current therethrough, a ballast case for housing said apparatus, a starting capacitor, circuit means including electrical leads for connecting the output of said high reactance transformer across said serially connected lamps and for connecting said starting capacitor across one of said lamps, at least one of said capacitors having a metallic container and a capacitor roll having interleaved foil layers and dielectric layers disposed therein, the outer foil layer of said capacitor roll being spaced from said metallic container and in capacitive relation therewith, grounding circuit means connecting said metallic container in electrical circuit relation with said ballast case to provide a grounded connection for the ballast apparatus, the capacitive reactance between said capacitor container and the outer foil layer providing suflicient impedance to prevent any significant current flow from the high reactance transformer to said ballast case during operation and said grounding circuit means providing the only return path for auxiliary starting aid current from said conductive plate.

8. A fluorescent lamp lighting system comprising at least one fluorescent lamp, a conductive plate, said lamp being disposed in capacitive relation with said conductive plate so that an auxiliary starting aid current can flow thereto, a high reactance transformer having a primary and a secondary winding inductively coupled therewith on a magnetic core, a pair of input terminal leads connected across said primary winding, circuit means including electrical leads for connecting the output of said high reactance transformer across said lamp, a capacitor serially connected with said secondary winding to cause leading current to flow in said secondary winding, said capacitor including a capacitor roll having interleaved foil layers and dielectric layers and a metallic container disposed in capacitive relation with at least the outer foil layer of said roll, a ballast case for housing said apparatus, grounding circuit means connecting said capacitor container in electrical circuit relation with a ballast case for providing a grounded connection to form a starting aid circuit with said conductive plate, said capacitive reactance between said outer foil layer of said capacitor roll and said container providing suflicient impedance to prevent any significant current flow from said high reactance transformer to said ballast case during operation, and said grounding circuit means providing the only return path for the auxiliary starting aid current from said conductive plate to said ballast apparatus.

9. A fluorescent lamp lighting system comprising a pair of fluorescent lamps, a conductive plate, said lamps being disposed in capacitive relation with said conductive plate so that a starting aid current can flow thereto, said conductive plate being grounded, a high reactance transformer having a primary winding and a secondary winding inductively coupled therewith on a magnetic core, a pair of input terminal leads connected across said primary winding and provided for connection across an alternating current supply, a capacitor connected in series circuit relationship with said secondary winding to cause a leading current to flow therethrough, a starting capacitor, a ballast case for housing the ballast apparatus, circuit means including electrical leads for applying at least the voltage across said secondary winding across said lamps and for connecting said starting capacitor across one of said lamps, said starting capacitor and power factor capacitor having a metallic container and a capacitor roll formed of interleaved foil layers and dielectric layers, the outer foil layer of said capacitor roll being disposed in capacitive relation with said metallic container, the reactive capacitance between said container and said capacitor roll providing sufiicient impedance during operation to prevent any significant current flow from the high reactance transformer to said ballast case, grounding circuit means connecting said metallic container to said ballast case for providing a grounded connection, said grounding circuit means providing the only return path for the auxiliary starting aid current when said power supply is not grounded.

10. Aballast apparatus for starting and operating from an alternating current supply at least one gaseous discharge lamp disposed in a capacitive relation with a grounded conductive plate, said apparatus comprising a pair of input terminal leads for connection With the alternating current supply, a ballast means, a capacitor, said capacitor having a capacitor roll and a conductive container disposed in capacitive relation with said roll to provide a capacitance therebetWeen, circuit means including electrical leads for connection With said lamp, said circuit means connecting said input terminal leads, said ballast means and said capacitor in circuit with said electrical leads for connection with said lamps so that a leading current is supplied to said lamp and a current limiting impedance is provided for said lamp, a conductive ballast case for housing said apparatus and arranged for connection to said conductive plate, and circuit means connecting said container in electrical circuit with said ballast case, said capacitance providing sufficient impedance during operation to prevent any significant current fiow from the apparatus to said ballast case and said last mentioned circuit means providing the sole path within said ballast case for auxiliary starting aid current to said conductive plate and lamp.

References Cited in the file of this patent UNITED STATES PATENTS

Claims

1. A BALLAST APPARATUS FOR STARTING AND OPERATING AT LEAST ONE FLUORESCENT LAMP DISPOSED IN A CAPACITIVE RELATION WITH A CONDUCTIVE FIXTURE, SAID APPARATUS COMPRISING A HIGH REACTANCE TRANSFORMER HAVING A PRIMARY WINDING ANMD A SECONDARY WINDING INDUCTIVELY COUPLED THEREWITH ON A MAGNETIC CORE, A PAIR OF INPUT TERMINAL LEADS CONNECTED ACROSS SAID PRIMARY WINDING, A CIRCUIT MEANS INCLUDING A PAIR OF OUTPUT LEADS FOR APPLYING THE OUTPUT OF SAID TRANSFORMER ACROSS SAID LAMP, A CAPACITOR SERIALLY CONNECTED WITH SAID SECONDARY WINDING TO CASE A LEADING CURRENT TO FLOW THERETHROUGH, A CONDUCTIVE BALLAST CASE, SAID HIGH REACTANCE TRANSFORMER AND CAPACITOR BEING DISPOSED IN SAID BALLAST CASE, SAID CAPACITOR INCLUDING A CAPACITOR ROLL HAVING ELECTRODES OF INTERLEAVED FOIL LAYERS AND A CONDUCTIVE CONTAINER FOR HOUSING SAID CAPACITOR AND DISPOSED IN CAPACITIVE RELATION WITH THE OUTER FOIL LAYER AND CIRCUIT MEANS FOR CONNECTING SAID CONTAINER IN ELEC-