US3704390A

US3704390A - Combined capacitor-inductor reactor device having transformer characteristics

Info

Publication number: US3704390A
Application number: US221113A
Authority: US
Inventors: Frederick W Grahame
Original assignee: Individual
Current assignee: Individual
Priority date: 1972-01-26
Filing date: 1972-01-26
Publication date: 1972-11-28
Anticipated expiration: 1989-11-28

Abstract

A combined capacitor-inductor reactor formed by spaced-apart layers of insulation and conductive foil rolled together around a core member to form a combined capacitor-inductor reactor. By connecting the input supply terminals to two different points on the same conductive foil and deriving the output from across a portion of the second foil which is coextensive with the part of the first coil intermediate the input terminals, the structure will exhibit capacitor connected transformer characteristics suitable for use as a fluorescent lamp starting and ballast circuit.

Description

' United States Patent Grahame 1151 3,704,390 1451 Nov. 28, 1972 1 COMBINED CAPACITOR-INDUCTOR REACTOR DEVICE HAVING TRANSFORIVIER- CHARACTERISTICS [72] Inventor: Frederick W. Grahame, 22 Grant Avenue, Glens Falls, NY. 12801- [22] Filed: Jan. 26, 1972 [21] Appl. No.: 221,113

Related US. Application Data I [63] Continuation of Ser. No. 40,272, May 25,

.1970, abandoned.

[52] US. Cl. 315/276, 315/282, 336/69, 336/90, 336/94, 336/100 [51] Int. Cl ..H01f 15/14, l -l0lf 27/02 [58] Field of Search ..336/96, 100,69, 70, 90, 92, 336/94, 150, 165; 315/276, 282

[56] References Cited UNITED STATES PATENTS 3,078,411 2/1963 Book ..336/150 X 3,210,648 10/1965 Lockie ..336/70 X 2,521,513 9/1950 Gray ..336/165 X 3,456,221 7/1969. Martin et al. "1336/69 7 366,544' 7/1887 Westinghouse, Jr.....336/96 x 3,210,706 10/1965 Book ..336/69 x 3,210,705 10/1965 Lockie ..336/69 x 3,210,703 10/1965 Lockie ..336/69 x 3,210,704 10/1965 Book ..336/69 x 3,077,946 2/1963 Wilkins ..336/100 x 3,161,843 12/1964 Hodges et a1 ..336/96 Primary Examiner-Thomas J. Kozma Attorney-James J Lichiello 1571 3 ABSTRACT A combined capacitor-inductor reactor formed by spaced-apart layers of insulation and conductive foil rolled together around a core member to form a combined capacitor-inductor reactor. By connecting the input supply terminals to two different points on the same conductive foil and deriving the output from across a portion of the second foil which is coextensive with the part of the first 'coil intermediate the input terminals, the structure will exhibit capacitor connected transformer characteristics suitable for use as a fluorescent lamp starting and ballast circuit.

6 Claims, 6 Drawing Figures PATENTEU NOV 28 I972 INPUT FIG.6.

INVENTOR: FREDERICK W. GRAHAME,

s ATTORNEY.

COMBINED CAPACITOR-INDUCTOR REACTOR DEVICE HAVING TRANSFORMER CHARACTERISTICS This is a continuation of application Ser. No. 40,272, filed May 25, 1970, now abandoned.

BACKGROUND OF THE INVENTION duction Apparatus, issued Sept. 5, 1950, discloses a number of different known constructions for combined capacitor-inductor reactor devices. These known devices, while suitable for a number of electrical applications, have not proven entirely satisfactory for certain uses because of their operating characteristics. The present invention makes available an improved, combined capacitor-inductor reactor device having capacitor connected transformer vcharacteristics, and is ideally suited for use as a starting and ballast circuit for fluorescent lamps.

SUMMARY OF THE INVENTION It is therefore a primary object of the invention to provide a new and improved combined capacitor-inductor reactor structure.

Another object of the invention is to provide such a structure which exhibits capacitor connected transformer characteristics and is suitable for use as a starting and ballast circuit for fluorescent lamps.

A still further object of the invention is the provision of a combined capacitor-inductor reactor structure having improved starting characteristics as well as improved sound deadening and heat distribution properties.

In practicing the invention a combined capacitor-inductor reactor device is provided which is of the type including at least first and second, spaced-apart, tapelike conductive foils having intervening layers of electrical insulation rolled together to form a combined capacitor-inductor reactor. The improvement comprises first terminal means connected to a point on one of the conducting foils and second terminal means connected to a different point on the same conductive foil with third and fourth terminal means being connected across at least a portion of the second conductive foil that is coextensive with the portion of the first conductive foil intermediate the first. and second terminal points. The point of connection of the first terminal means preferably is at one end of the first conductive foil with the second terminal means being connected at some point intermediate the length of the first conductive foil. The third and fourth terminal means are connected preferably across the respective ends of the second conductive foil in a manner such that the capacitor-inductor reactor device operates as a transformer having a fixed capacitor serially connected with its secondary winding. The turns ratio of this transformer is determined by the relative lengths of the first and second conductive foils intermediate the first and second terminal means and the third and fourth terminal means, respectively.

Preferably, the combined capacitor-inductor reactor device includes a magnetically permeable core member which is surrounded by the rolled turns of the tapelike conductive foils and intervening layers of electrical insulation. This entire structure including the core member then preferably is enclosed in a suitable liquid tight metal case providing electrical insulated terminal connections to the respective first through fourth terminal means, and the rolled conductive foils and interclosed in a second outer housing providing access to the insulated terminal connections and having the space intermediate the second outer housing and the metal case filled with a suitable ballast compoundsuch as sand-loaded asphalt for improved sound deadening and heat distribution. In preferred embodiments of the invention, the first and fourth terminals may in fact comprise a single, common terminal point that is suitable for grounding.

. BRIEF DESCRIPTION OF THE DRAWINGS Other objects, features and many of the attendant advantages of this invention will be appreciated more readily as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein like parts in each of the several figures are identified by the same reference character, and wherein:

FIG. 1 is a perspective view of a partially disassembled coil of tape-like, conductive foil having intervening layer electrical insulation and rolled together to form a combined capacitor-inductor reactor structure.

FIG. 2 is a schematic illustration of the structure shown in FIG. 1 if it were unrolled into a straight line structure, and depicts the manner in which the structure derives its capacitive characteristics.

FIG. 3 is a perspective view of the structure shown in FIG. I mounted on a suitable core member of magnetically permeable material.

FIG. 4 is a schematic physical illustration of the manner of connection of the input supply terminals and load deriving output terminals to the cap-reactor structure of FIG. 3.

FIG. 5 is an equivalent circuit diagram of the capreactor structure connected as shown in FIG. 4.

FIG. 6 is a partial sectional view of a complete, combined capacitor-inductor reactor structure including an improved liquid tight, sound proof, outer supporting casing constructed in accordance with the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a perspective view of a combined capacitorinductor reactor (hereafter referred to as a cap-reactor) formed by rolling together two tape-like sheets of conductive foil 11 and 12 with the conductive foils l1 and 12 being separated by intervening sheets of electrically

insulatingdielectric material

13 and 14. The conductive foils 11 and 12 may comprise aluminum foil or some other similar material and the sheets of dielectric material l3 and 14 may comprise any known electrically insulating dielectric which is capable of being fabricated in tape-like rolls. For example, the dielectric material may comprise paper of a suitable'thickness and dielectric strength suchas Kraft paper, linen paper or the like, sheets of a low loss dielectric resin such as Mylar (polyethylene-terephthalate), polypropylene, or.

other suitable, known dielectric material. The sandwiched layers of tape-like conductive foils l1 and 12 and intervening layers of electrically insulating

dielectric material

13 and 14 are rolled together to form the coil structure shown in FIG. 1. While only two conductive foils 11 and 12 and suitable intervening layers are described, it is believed obvious that additional foils and layers can be provided should such a structure be desired or required in order to obtain desired operating characteristics.

If the coil structure 10 of FIG. 1 were unrolled and laid out flat, it would appear schematically as shown in FIG. 2 where S, and 8, represent the start of the tapelike conductive foils 11 and 12, and F, and F, represent the'finish of each of the respective foils. When thus visualized, the manner in which the structure obtains its capacitive reactance characteristic can be more easily appreciated. Also, it is believed obvious from a consideration of the wound, interleaved, turns of the conductive foils l1 and 12 shown in FIG. 1 wherein the structure acquires its inductive reactance characteristics to thereby provide a combined capacitance-inductance reactance when employed in an electrical circuit.

The inductance of the coil 10 can be greatly increased by providing a magnetically permeable core member 15 to the structure asshown in FIG. 3. This can be accomplished by employing two E-shaped core members fabricated from laminated, E-shaped, magnetically permeable steel members. The E-shaped core members are arrayed in a manner such that the central leg 16 extends through a central opening in the coil 10. Suitable connecting arms 19 secured to the

outer legs

17 and 18 of the E-shaped core members hold the arrangement in assembled relation. Input and output terminal means to various points on the conductive foils are shown at T,, T, and T, and are connected as described hereinafter.

In order for a cap-reactor such as shown in FIG. 3 of the drawing to be connected in electrical circuit rela-' I tionship with a load, it must be specifically tailored or designed to serve that load. The particular embodiment of that invention described herein is specifically designed to serve as a starting and ballast circuit for a fluorescent lamp. For this purpose, the device must serve to supply a high voltage surge across the lamp terminals for starting purposes hence requiring that the device function as a step-up transformer to provide the higher than line voltage surge for starting. Thereafter, the device must serve to limit circuit current since a fluorescent lamp, while operating, exhibits negative resistance. The circuit also preferably should exhibit high power factor characteristics. In existing fluorescent ballast circuit using a conventional wire wound transformer and separate individually connected capacitors, the circuit arrangement often appears as shown by the equivalent circuit of FIG. 5. In this arrangement, the turns ratio between the secondary and the primary of the transformer supply provides the required voltage step-up for starting while the serially connected capacitor assures the creation of the desired starting voltage surge and high power factor correction.

FIG. 4 of the drawing illustrates the manner in which a capreactor such as shown in FIG. 3 may be physically connected to a source of supply potential and across a fluorescent lamp load so that it operates in accordance with the equivalent circuit shown in FIG. 5. In the arrangement shown in FIG. 4, both input leads T, and T, from a single phase supply of alternating current, such asa conventional, 60 cycle, -120 volt-l5 amp residential power supply, are connected to different points on the same conductive foil such as 11. The number of foil turns which are included between the points of connection of the terminals T, and T, in effect determines the effective inductance of the primary winding of the transformer. The output from the transformer thus comprised is obtained preferably by connecting the load 21, such as a fluorescent lamp, across the second conductive foil 12 between the finish point F, of the second conductive foil 12, which comprises the secondary of the transformer, and a terminal T, which is connected to the starting point S, of the first conductive foil 11. Since the starting point S, of foil 1 l is at the same potential as the input terminal T, and the output terminal T it will be seen that these two points are in fact at the same common potential and may be treated as a single, common terminal point which may be grounded.

In FIG. 4, the transformer action of the portion of the conductive foil 11 intermediate the terminal points T, and T acting as a step-up primary, induces a steppedup voltage from end to end of each of the foils 11 and 12, and which is taken off of foil 12 acting as a secondary and applied across load 21 serially through the effective interturn capacitance. This serial capacitance is determined by the overall length of the conductive foils l1 and 12, the width of the conductive foils, the spacing between the foils, the nature of the dielectric insulating layers separating the foils and the operating frequency of the circuit as is described more fully in the above referenced Gray US. Pat. Number 2,521,513. The inductance of the conductive foil 12 and serial capacitance provides both inductance and capacitance in series with the fluorescent lamp load 21. As a consequence, the structure will operate to provide the desired current limiting, high inductive starting voltage surges, and high power factor characteristic effects required for use as a fluorescent lamp starting and ballast circuit in the manner of the equivalent circuit shown in FIG. 5.

While in the particular embodiment of the invention disclosed a step-up transformer connection has been described in detail, it is believed obvious to one skilled in the art that a step-down transformer function readily could be obtained to satisfy the requirements of a different load by appropriate rearrangement of the points on the respective conductive foils l1 and 12 to which the input supply and output load terminals are connected. Further, it is believed obvious that the tapoff points on the second conductive foil 12 could be placed at some intermediate points along the length of foil 12 to thereby adjust the turns ratio of the secondary to the primary winding of the transformer.

One of the problems heretofore encountered in the use of capreactors is the desirability, and often the necessity, of using a liquid impregnated coil-capacitor system in order to obtain higher corona starting voltages and better thermal properties than can be obtained with an unimpregnated or solid-impregnated system. FIG.'6 of the drawings illustrates a preferred form of construction of the capreactor described hereinbefore in connection with FIGS. 1-5. In this preferred embodiment of the invention, the cap-reactor structure of FIG. 3 (connected in the manner illustrated in FIG. 4) is enclosed in a suitable liquid-tight, metal case 25 which completely encloses the rolled coil-capacitor conductive foils and intervening layers of electrical insulation together with magnetically permeable core member. Suitable, liquid-tight, electrically insulated lead-in conductors are provided to allow for connection to the supply and load terminals T T and T With the cap-reactor thus enclosed the rolled conductive foils and intervening electrically insulating dielectric layers may be liquid impregnated in a vacuum with a suitable dielectric liquid such as an askarel or other capacitor impregnant for improving the starting voltage and thermal properties of the system. By enclosing the entire core member, foil windings and insulating layers in a liquid-tight metal case that is outside most of the magnetic field of the structure, the metal case will not dissipate energy by acting as a shorted turn and at the same time will minimize magnetic coupling problems and leaks around the leads to the structure.

Because. the metal case enclosing the liquid impregnated, wound conductive foils and core member might produce an audible hum, the liquid impregnated and metal encased cap-reactor is further enclosed in a second housing 27 which may be of metal, plastic, or other suitable housing material having a traditional ballast shape. The space between metal case 25 and the outer housing 27 preferably is filled with a ballast potting compound 28 such as sand-loaded asphalt in order to provide improved sound deadening and heat distribution characteristics to the completed structure.

From the foregoing description it will be appreciated that the invention provides an improved, combined capacitor-inductor reactor structure that exhibits capacitor connected transformer characteristics and which is suitable for use as a fluorescent lamp starting and ballast circuit. By reason of the special design of the cap-reactor and its enclosure in a suitable liquidtight housing, the cap-reactor structure can be liquid impregnated to provide improved starting and thermal properties along with improved sound deadening and heat distribution characteristics.

Having described one embodiment of an improved, combined capacitor-inductor reactor device having capacitor-connected transformer characteristics constructed in accordance with the invention, it is believed obvious that other modifications and variations of the invention are possible in the light of the above teachings. It is therefore to be understood that changes may be made in the particular embodiment of the invention described which are within the full intended scope of the invention as defined by the appended claims.

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

1. In a combined constant current capacitor-reactor device of the type including spaced apart tape-like conductive foils with intervening layers of electrical insulation rolled together to form a combined capacitor inductor reactor, the improvement comprising:

a first conductive foil having a starting point and a finishing point;

a second conductive foil having an electrically isolated starting point and a finishing point;

first input terminal means connected to said starting point of said first conductive foil;

second input terminal means-connected to said first conductive foil at a connection point between said starting point and said finishing point of said first conductive foil; first output terminal means connected to said finishing point of said second conductive foil,said first conductive foil and said second conductive foil forming a predetermined capacitance which ele'ctrically appears in series with said finishing point of said second conductive foil; and

second output terminal means connected to said starting point of said first conductive foil.

2. A combined constant current capacitor-reactor device according to claim 1 wherein the distance between said starting point and said finishingpoint on said second conductive foil is a greater distance than the distance between said starting point and said connection point of said second input terminal means on said first conductive foil.

3. A combined constant current capacitor-reactor device according to claim 2 including a constant current load device and further including a magnetically permeable core member, a portion of said core member being surrounded by the rolled turns of the tape-like conductive foils and intervening layers of electrical insulation to provide a high reactance constant current device for said constant current load device.

4. A combined constant current capacitor-reactor device according to claim 3 wherein the rolled turns of conductive foils and intervening layers of electrical insulation are liquid impregnated with a dielectric liquid and the entire structure including the magnetically permeable core member is enclosed in a suitable liquid tight metal case providing electrically insulated terminal connections to said first input terminal means, said second input terminal means, said first output terminal means, and said second output terminal means, and wherein the liquid impregnated and metal encased capacitor-reactor structure is further enclosed in a second outer housing providing access to the insulated terminal connections, and having a space intermediate the second outer housing in the metal case filled with a suitable ballast compound, such as sand-loaded asphalt for improved sound deadening and heat distribution.

5. A combined constant current capacitor-reactor device according to claim 4 wherein said first input terminal means and said second input terminal means comprise primary input terminals for connection to a source of supply potentiaL and wherein said constant current load device is connected between said first output terminal means and said second output terminal means.

6. A combined constant current capacitor-reactor device according to claim 5 wherein said constant current load device is a fluorescent lamp connected

Claims

1. In a combined constant current capacitor-reactor device of the type including spaced apart tape-like conductive foils with intervening layers of electrical insulation rolled together to form a combined capacitor inductor reactor, the improvement comprising: a first conductive foil having a starting point and a finishing point; a second conductive foil having an electrically isolated starting point and a finishing point; first input terminal means connected to said starting point of said first conductive foil; second input terminal means connected to said first conductive foil at a connection point between said starting point and said finishing point of said first conductive foil; first output terminal means connected to said finishing point of said second conductive foil, said first conductive foil and said second conductive foil forming a predetermined capacitance which electrically appears in series with said finishing point of said second conductive foil; and second output terminal means connected to said starting point of said first conductive foil.

2. A combined constant current capacitor-reactor device according to claim 1 wherein the distance between said starting point and said finishing point on said second conductive foil is a greater distance than the distance between said starting point and said connection point of said second input terminal means on said first conductive foil.

5. A combined constant current capacitor-reactor device according to claim 4 wherein said first input terminal means and said second input terminal means comprise primary input terminals for connection to a source of supply potential, and wherein said constant current load device is connected between said first output terminal means and said second output terminal means.

6. A combined constant current capacitor-reactor device according to claim 5 wherein said constant current load device is a fluorescent lamp connected between said first output terminal means and said second output terminal means.