US2945987A

US2945987A - Electrical discharge apparatus

Info

Publication number: US2945987A
Application number: US816341A
Authority: US
Inventors: Jeanne E Strecker
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1959-05-27
Filing date: 1959-05-27
Publication date: 1960-07-19
Anticipated expiration: 1977-07-19

Description

July 19, 1960 c. E. s-rREcKER ELECTRICAL DISCHARGE APPARATUS Filed may 2v, 195s u we . ELECTRICAL DISCHARGE APPARATUS' Charles E. Strecker, deceased, late of Danville, Ill., by Jeanne E. Strecker, executrix, Danville, Ill., assigner to General Electric Company, a corporatlon of New York Filed May 27, 1959, Ser. No. `816,341 6 claims. (cl. 315-100) This invention relates generally to circuits and apparatus for starting and operating gaseous electric dlscharge lamps from an alternating current source, and more particularly Lemmers, and assigned tothe same assignee as the instant application. y

Two or more heated cathode'discharge lamps are frequently connected in series with a ballast across a relatively high voltage supply source, but of insuiclent voltage to start either lamp; for example, across a 460 volt source available for industrial distribution. As is'wellknown, normal residential and commercial distribution voltage is in the range from 110 to 240 volts; industrial l voltages are generally distributed at 220 4to14'80 voltsl The circuit apparatus for two such serially connected lamps normally includes a cathode heating transformer,`

for supplying heating current to the lamp cathodes, a starting capacitor for starting rst one and then the other of such discharge lamps, a power correcting capacitive reactor for improving input power factor, and an induc-` tive ballasting impedance which limits the current ow through the discharge lamps during operation, and which is required due to the negative current characteristicof the lamp.

In such apparatus, it has been common practice to connect the primary Winding of the cathode heating transformer directly across the supply line r across the lamps. This has resulted in a transformer having a low current, high voltage primary requiring a primary Winding of very line wire and which is, in general, expensive to manufacture. In order to reduce the cost of the apparatus,.it would be desirable if a cathode heating transformer vcould be used having a low voltage, high current primary.

Certain improved apparatus described `and claimed in an application tiled by Wesley W. Brooks and me on even date herewith, entitled Electric Discharge Apparatus, and assigned to the-same assignee as the present invention, overcomes the aforementioned difliculties for a lighting system for connection to a high voltage source of sufcient voltage to start and operate the lamps, such asa 550 volt source. However, the aforementioned invention is not adapted for use where the source of high voltage is insuicient to start the lamps. The instant invention is an improvement'over the invention described in the aforesaid Brooks et al. co-pending application and has as its object the provisionrof an improved apparatus having especially good lamp current regulation suitable for operating at least one discharge lamp from a source of high voltage insuicient to start the lamp.

ilnited States Patent cathode heating transformer 2 having a primary winding` Another object of this invention is to prdvid'e anl proved electrical circuit and apparatusA forlstartmgand operating electric discharge lampswhere the cathodeheat ing transformer is connected for energization' at a relative! ly low lvoltage and which results in particularly .good

lamp current regulation.

Another object is the provision of an improved electricall circuit 'and apparatus for operating a pair of seriallyV con-` nected discharge lamps from a source of high voltageinfA suicient to start either lamp.

IBrieiiy stated, according to the presentl invention, the

improved electrical circuit and apparatus for startingand operating at least one disch-arge lamp comprises a cathode heating transformer-having a primary winding in series,

circuit relation with a capacitive reactor across a high voltage supply source of insufiicient voltage to start the lamp. v

The capacitive'reactor has sufficient capacitance with reference to the inductance of the transformer to drawaleading current throughthe transformer primary. Asis well-1 known, avleading current through anindu'ctance .causes a,` voltage ,rise` inthe inductance. A `,starting and operating Y' loop includes the transformer primary and the` lamp nfa series circuit across the source of alternating current. Thel rise 'in `voltage across the inductance vcreates, Va voltage across the lamp greater thanthe sourcevoltage. increased voltage is suicient tol start the lamp.

The invention, together' with additional objects and atl-y vantages thereof, will be best Yunderstood from .thenfolf lowing description of specific embodiments, read in con-` nectionwith the accompanying drawing, in which:

Fig. l1 is a schematic diagram of an improved discharge Y circuit and apparatus according to the invention; andl Fig. 2 is a schematic diagram of 4an improved discharge circuit and apparatus illustrating another embodiment of the invention.

Referring toy the modification of Fig. 1,: thelimproved ballast transformer apparatusl'includes ar lovy.V voltage 3 and secondary cathode heating windings 4, 5, and 6 on a'magnetic core 7. A pair of leads 8, 9 extend fromv the ballast transformer apparatus` 1 for connection across av source of alternating current voltage 10, 11. One lead 8 is connected tovafrst'end ofV the .primary winding 3. `The other end of the primary winding 3 isVV connected 'by` means of line 12 to one end of a current limiting inductive reactor 13.

. primaryvwinding 43 and the b'allasting'` winding l13 is'cou lamp has a heated cathode in nectedto a capacitive'reactr 15;l the othericndof the@ capacitivevreactor 15 is connected to lead 9; v

The ballast transformer apparatus 1 is connected vto operate a pair of seriallyconnected lamps 16,17. f. Each 16 has cathodes 1,8 and-19 in the ends thereof; lamp. 17

16.: Cathode heating winding 6 has aipair of leads 26,'27,

which, in conjunction with lead 9, connect cathodeA heating lamp 17.V Connec'ted'j,j across the second lamp 17 is a low capacitancfctarting winding 6 across cathode 21 of capacitor 28in `parallel with the second lamp 171"I The reactance of capacitive reactor 15 is selected magnitude with respect to the inductance reactancefof transformer 2 so that when no current is owing through lamps 16 and 17, the capacitive reactance of capacitive reactor 15 is such with respect to the inductive reactance` of ytransformer 2 'that a leading current will flow in `a series circuit across the source 10, 11 of alternating current volt-f age including the prim-ary 3 of the transformer Zand the capacitive reactor 15. The source 10, 11 of alternatingd:

Fat'ented July 19,

The junctionll at theY second' end of the...

its respective lend;` lamp Y current voltage is, as heretofore described, of insucient voltage to start the lamps 16, 17. However, as is wellknown, when a leading current is drawn through an inductance, the voltage appearing across the inductance will generallybe additive to the supply voltage. Therefore, as

the capacitive 'reactor 15'is suiicient to draw a leadingy current through the.transformer 2, the voltage appearing.

tricalcircuit 'relation to lthejlow potential side 11 'ofthe supplysource ;10, 11.` Since normal residential and commercial electrical' distribution systems in this `country have their low potential side grounded, as shown by ground 30, the fixture 29 may-be an electrical circuit with the low potential side 11 of the supply source 10, 11 through grounds 30 and131. f

Prior to starting `of thelamps 16, 17, when the circuit is 'firstenergized neither lamp is conducting. However, asmall amount of current will be drawn in the series circuitV including the transformer primary 3 and the capacitive reactor 15 thereby creating an increase in voltage as Yexplained above. A first series starting circuit or loop will` include the primary 3',.the current limitingreactor 13,

the'first lamp 16, andthe starting `capacitor 28, connected L inra series circuit across thesource 10, 11 of alternating current voltage. in the circuit, there is no significant voltage drop,across the starting capacitor 28,jand the increased voltage across the primary winding 3 is sufiicient to start lamp. 16. Once lamp 16 has started, the voltage will he placed across the second lamp 17 in a second starting loop including the primary winding 3 of the cathode heating transformer, the current limiting reactor 13, the first lamp 16 (which has now started), and the second lamp 17, in a series circuit across the source 10, 11 of alternating current voltage. The voltage across lamp 17 is adequate to start-thelamp and lamp 17 now starts. The operating current across the electrodes of the lamps is large with respect to the current flow through the starting. capacitor 28; the current tiow through the starting capacitor will be minor'with reference to the operating circuit. Thev impedance of current'limiting reactor 13 is sutiicient to ballast the lamps. and to limit the operating voltage dropl across the primary winding 3 -to a relatively value, there-- by obtaining the benefits describedabove.

In atypical circuit according to the modification of- Fig'. l, the lamps 16, 17 `may .each be a 0.8 amperelamp,`

General Electric Company Catalogue No. 96T12; the supply. voltage .may consist'of a 460 volt,` 60. cycle 4distribution system. The currentV limiting'reactor 13 may have aninductive impedance of 1.0 henries to limit the current tiow through the lamps, after starting, to 0.8. R.M.S. amperes, and torestrict the voltage drop across the primary 3 of the cathode heating transformer 2 to 66- volts. A 3.9 mfd, capacitive reactor 15 will produce the desired .power factor correction and current phase; starting .capacitor 28 may have value of 0.075 `mfd. The cathode heating transformer `IZ'is arranged with the-proper turns ratio so that 3.5'volts potentiall is supplied to each cathode. The above described circuit, according to the instant inventonf will .consume approximately` 305 :voltamperes in reactor 13, 44^voltamperes in the cathode heatingV transformer 2; and 550 -volt-amperes in capacitive reactor 15.

The modification of Fig. Zis similar to that illustrated in Fig. 1, exceptthe cathode heating` transformer 2a (of Fig., 2) is on a saturable.core.7a thereby producing a saturable transformer. The core 17a does not operate in thefully saturatedfarea; but, contrary, would `under normal lconditions operate in the nonlinear portion Ol- K114i@ Since no operating current is owing.

' voltage variationsof the source 10, 11.

assess? of the saturation curve. Such a nonlinear transformer 2a has certain advantages which makes it particularly useful in the disclosed circuit.

In the modification of Fig. 2, it is necessary that the capacitive reactance of capacitor 15 be sufficiently large with respect to the inductive reactance of the transformer 2a so that a leading current is drawn through the transformer primary 3.both during starting and while operating. When a leading current is drawn through the primary 3, a: nonlinear transformer 2a willtend to keep the voltage across-the-lamps 16, 17 more nearly constant during Assume, for example, that the-source voltage 10, 11 decreases so that a low voltage condition exists. The magnetizing reactance of the transformer 2a riseswhen-the source voltage 10, 11 falls. As the reactance rises, the voltage across the nonlinear transformer 2a tends to increase due to the leading lcurrent through the transformer. As the` voltage across the primary is additive to the line voltage, the voltage across the lamps 16, 17 will remain relatively constant. In other words, if the source voltage 10, 11 drops the increased voltage rise across the transformer 2a provides a counterbalancing effect giving good voltage regulation across the lamps. where the source voltage rises. In such instance, the reactance of the transformer 2a drops since the core 7a becomes more nearly saturated as the current tends to increase. This decreasing reactance of the transformer results ina voltage drop across the primary 3 of the-A SinceA In accordance with the patent statutes, I have described what at present are considered to be the preferred embodiments of my invention. However, it will be obvious to those skilled in the art that various changes and modifications may be made in the disclosed structure without departing from the true spirit and scope of my invention, and it is, therefore, aimed in the appended claims to cover all such changes and modifications that fall within the true spirit and scope of my invention.

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

1. Apparatus for operating at least oneheated cathode discharge lamp from a source of alternating current of insufficient voltage to start and operate the lamp, comprising input means adapted4 to be connected to the` source of supply current, a cathode-heating transformer having a magnetic core, a primary winding on said core, means for connecting said lampin series with said primary winding across said input means, cathode heating secondary windings on. said core having leads for supplying cathode.

heatingcurrent to the cathodes of said lamp, anda capacitivereactorof greater capacitive reactance than the inductive reactance of said transformer at leastduring startingof said lamp and -connected across said lamp in a seriescircuit with said primary winding across said input means, whereby leading current is drawn through saidV primary winding-during starting of .said lamp.

2. Apparatus according to claim l wherein said magnetiecore operates in the nonlinear saturation area, and wherein said capacitivereactance is greater than the inductive reactance of said transformer during bothA startingandoperating of said lamps whereby leading current is drawn through said'primary winding during both startingand operation of said lamps.

3.' Apparatusforoperating at` least two serially connected, heated cathode discharge lamps, from asource of alternating current. of insufcient voltage to start and operate the lamps, comprising input means adapted to be Now assuming the condition` connected to the source of supply current, a cathode heating transformer having a magnetic core, a primary Winding on said core, a current limiting reactor serially I connected to said primary winding, means for connecting said serially connected lamps in a series circuit with said primary winding and said reactor across said input means, cathode heating secondary windings on said core having leads for supplying cathode heating current to the cathodes of the lamps, a starting capacitor having means for connection across one of said lamps to eiect sequential starting thereof, and a capacitive reactor of greater capacitive reactance than the inductive reactance of said transformer at least during starting of said lamps and connected in a series circuit with said primary winding across said input means and in series circuit with said current limiting reactor across said lamps, whereby leading current is drawn through said primary winding during starting of said lamps.

4. Apparatus according to claim 3 above wherein said magnetic core operates in the nonlinear saturation area, and wherein said capacitive reactance is greater than the inductive reactance of said transformer during both starting and operating of said lamps whereby leading current is drawn through said primary winding during both starting and operation of said lamps.

5. Apparatus for operating a pair of serially connected, heated cathode discharge lamps from a source of alternating current supply voltage of insu'icient Voltage to start and operate the lamps, comprising a pair of input leads adapted to be connected to the source of supply current, a cathode heating transformer having a magnetic core, a primary winding on said core with one end connected to one of said input leads, a current limiting reactor having one end connected to the other end of the primary winding in series circuit therewith and having means for connecting its other end to the cathode of one of said serially connected lamps, the second of said input leads having means for connection to the cathode at oneV end of the other serially connected lamp, a first cathode heating secondary winding on said core having leads for supplying cathode heating current yto one of the cathodes of the first lamp, a second cathode heating secondary winding on said core having leads for supplying cathode heating current to the other cathode of said rst lamp and one cathode of said second lamp, and a third cathode heating secondary winding on said core having leads for supplying cathode heating current to the other cathode in said second lamp, a capacitive reactor having one end connected to the connection between said transformer primary and said current limiting reactor and having the other end connected to said second input lead, the capacitive reactance of said capacitive reactor being greater than the inductive reactance of said primary winding at least during starting of said lamps whereby leading current is drawn through said primary winding during v starting of said lamps, and a starting capacitor for connection across one of said lamps.

6. Apparatus according to claim 5 above wherein said core operates in the nonlinear saturation area, and Wherein said capacitive reactance is greater than the inductive reactance of said transformer during both starting and operating of said lamps whereby leading current is drawn through said primary winding during both starting and operation of said lamps.

References Cited in the ile of this patent Y Great Britain Oct. 1, 1952 Y CERTHHCATE OF CORRECTHN Patent Nog 2,945,987

Charles E. Strecker, deceased by Jeanne E. Strecken, executrix It is hereby certified that error appears i of the above num d specification bered patent requiring corre Patent should read as corrected below.

July 19,'1960 Column 3, line 49,

after "relatively" insert low Signed and sealed this 31st day of January l96l (SEAL) Attest:

Commissioner of Patents