US2348739A

US2348739A - Gaseous discharge lamp circuit

Info

Publication number: US2348739A
Application number: US411279A
Authority: US
Inventors: George B Horn
Original assignee: WHEELER INSULATED WIRE Co
Current assignee: WHEELER INSULATED WIRE Co; WHEELER INSULATED WIRE COMPANY Inc
Priority date: 1941-09-18
Filing date: 1941-09-18
Publication date: 1944-05-16
Anticipated expiration: 1961-05-16

Description

l GASEOUS DISCHARGE LAMP CIRCUIT Filed Sept. 18, 1941 INVENTOR George How/v ATTORNEYS Patented May 16, 1944 GASEOUS DISCHARGE LAMP CIRCUIT George B. Horn, F 'airiield, Conn, assignor, by

.mesne assignments, to The Wheeler Insulated Wire Company; Incorporated,

Bridgeport,

Conn., a corporation of Delaware v Application September 18, 1941, Serial No. 411,279 (Ci. 315-96) V 9 Claims.

This invention relates to electric gaseous discharge lamps or fluorescent tube circuits having a plurality of lamps or tubes therein, and is an improvement over the device disclosed and claimed in my Patent No. 2,241,261.

In that patent. there is disclosed an arrangementusing an autotransformer for operating a plurality of fluorescent tubes which is satisfactory for many installations. However, it has been found that under certain conditions the tempera: ture rise in the transformer becomes too great and the current requirements for operating the tubes too high. It has also been found that the wave form in the leading or capacitive tube deviated substantially from a sine wave.

These difficulties have been overcome by the present invention by inserting a single choke in the primary circuit in. series with and between the common point of connection and the alternating supply therefor.

When the circuit is so arranged, the starting current in both the leading and lagging tubes is reduced to substantially the minimums as set up by the Electrical Testing Laboratories, Inc.,' the running current of the leading tube is reduced, the temperature rise of the transformer is greatly reduced, and the wave form of the current in the leading tube is changed to' substantially a sine wave without in any way affecting the wave form of the lagging tube which is practically a sine wave. 7

The value of the impedance of'the choke so inserted in the circuit is small and, within a rea-' I sonable range, not critical as the position of the coils on the transformer may be shifted tocompensate for such variations in the value of the choke, together with suitable changes in the condenser in the circuit. a

Other features and advantages of the invention will be apparent from the specification and claims when considered in connection with the drawing, in which:

Figure 1 shows a diagram of the fluorescent tube circuit of the present invention.

Figure 2 shows a comparison of the waveforms of the current in the leading tube as produced in an oscillograph. I

In the illustrated form of the invention, the circuit includes two electric gaseous discharge lamps r fluorescent tubes in and II having filaments Ina, llib, and ilaand lib, at opposite ends thereof.

The filaments are connected in series by means of I starter switches diagrammatically shown at I00 and i lc. These switches preferably are of the type which automatically close the filament circuit to heat the filaments to activate the tubes and upon opening cause the tubes to are over.

Each switch remains in open circuit condition as long as there is an electron flow through the tube between the filaments.

Power for operating the tubes is supplied by a transformer l2 having an elongate core i3, a primary winding I4 and a .pair of secondary windings I 5 and IS. The windings i4, i5 and ii are shown as being connected to form an autotransformer with the secondary winding l5 connected to energize the filaments of tube III and the secondary winding l6 connected to the filament circuit "of tube Ii to energize them. A

condenser I! is included in one of the tube circuits.

The currents for the two tubes are thus electrically displaced so that one is leading current and the other lagging. Herein the tubes are referred to as leading or capacitive tubes and lagging or inductive tubes.

The circuit thus iar described is the same as described in my patent noted above and is highly satisfactory under normal conditions. However, it has been found, under certain conditions, that the temperature rise in the transformer is vtoo great and that the operating currents are too high.

,I have "discovered that these difficulties are overcome by inserting a choke coil IS in series with, and between, the common terminal of the primary and its connection to a sourceof alternating current indicated at l9.

{The impedance of the choke is relatively low and its value, within reasonable limits, is not critical as the position of the transformer windings can be adjusted-on the core and the value of. the condenser l1 varied to compensate for slight variations thereof.

The improved results obtained with this new circuit can best ,b shown by a comparative test of it with a circuit omitting the choke. For example, in a test conducted on a circuit having 40 watts output at the tubes, it was found that a 12 to 15% decrease in temperature rise was obtained when the choke is included in the circuit. When devices of this type are used in places'where ventilation and cooling conditions are bad, this is a substantial advantage.

With regardto the current requirements of the tubes, the running current in the lagging tube of the circuit without the choke, which we shall call the former circuit, was ,40 amp., and

with the present circuit was also .40 amp.. in-

F' icE i high maximum value.

dicating that by putting the choke in the circuit there was no change in the value 01' the running circuit for the lagging tube. However, the current in the leading tube in the former circuit was .44 amp., whereas with the new circuit it was only .40 amp. Thus it will be seen a substantial drop in the normal running current in the leading tube circuit is produced in the present arrangement.

The starting current for the tubes is greatly affected by the inclusion of the choke in the circuit. The Electrical Testing Laboratories, Inc., has established the minimum and maximum starting currents which are acceptable to tube manufacturers. These limits are minimum .55 amp. and maximum .75 amp. With the former circuit, the starting current was .70 amp. in the lagging tube and .65 amp. in the leading tube. It will be noted that although within the limits specified by the Electrical Testing Laboratories, Inc., these values are closer-to the upper limits.

With the new circuit, however, the starting current in the lagging tube is reduced to .58 amp. and in the leading tube to .56 amp., which val- .ues are approximately the minimum specified values.

This reduction of the starting current is particularly valuable in the case where the starter circuit contacts stick and fail to open the circuit and also when the tubes become deactivated, that is, where there is no electron flow between the filaments at the opposite ends of the tube. When this occurs, the starting circuit automatically attempts to bring the filaments to that temperature at which the tube will become activated, and, since the tube will not are over, a

periodic closing and opening of the starting switch will take place with the attendant flow of starting current.

' With the new circuit, the current demand is substantially reduced and naturally the temperature of the unit is reduced.

The wave forms of the currents in the two circuits were examined by means of an oscillograph. The current in "the" laggin tube was found to be substantially a sine wave and was not visibly aflected by the inclusion of the choke in the primary circuit. The current in the leading tube,however, in the former circuit was not a sine wave, but had a shape as shown in Fig. 2 by the dot and dash line 20. It will be noted that it is generally peaked and has a relatively With the choke in the primary circuit, however, the wave form of the current in the leading tube took the form shown by the solid line II in Fig. 2, which, it will be noted, was substantially a sine wave. This new wave i'orm was substantially thewave form of the current in the'lagging tube. The wave forms in Fig. 2 were traced from an actual comparison test on the oscillograph. I

This change in wave form is important from an operating standpoint as the leading tube no longer has a high or peak value but is substantially the same as that of the lagging tube.

The foregoing comparison has been made by way of example only and is not intended to limit the scope of the invention.

While the circuit of the transformer is illustrated as that of an autotransformer of the type disclosed and claimed in my patent, the present invention is not to be limited to a circuit employing only this transformer, but may be used with other transformer connections so long as a choke or the like is included in the primary assanso circuit which affects the secondary supp yi l the leading tube.

Variations and modifications may be made within the scope of this invention and portions of the improvements may be used without others.

I claim:

1. In a circuit for energizing a pair of electric gaseous discharge lamps, means for producing electrically displaced energizing currents, a leading current for one lamp and a lagging current for the other lamp; a transformer having a primary cbil and a pair of secondary coils, all oi said coils having a common terminal, one secondary coil being connected to each lamp; and a choke coil in a supply line connected to the common ter- 'minal of the transformer, said choke reducing the operating current requirements for said tubes.

2. A fluorescent tube circuit having a leading tube and a lagging tube therein; a source of alternating current; an autotransformer connected to said source and having a primary coil and a pair of secondary coils, one of the secondary coils being connected to the leading tube and the other secondary coil being connected to the lagging tube to operate said tubes, said primary and secondary coils having a common terminal; and a choke coil connected in series between the common terminal of the primary or the transformer and the source of alternating current, said choke coil reducing the starting and running current required to operate said leading and lagging tube.

3. A fluorescent tube circuit having a leadin tube and a lagging tube therein; a source of alternating current; an autotransformer connected to said source and having a primary coil and a pair of secondary coils, one of the secondary coils being connected to the leading tube and the other being connected to the lagging tube to operate said tubes; and means for reducing the temperature rise in the transformer for a given watt output including a choke coil connected in series with and between the common terminal of the transformer and the source of alternating current.

4. A fluorescent tube circuit having a leading tube and a lagging tube therein; a source of alternating current; an autotransformer connected to said source and having a primary coil and a pair of secondary coils, one secondary coil being connected to the leading tube and the other being connected to the lagging tube to operate said tubes. all of said coils having a common terminal; and means for producing substantially a sine wave in the/.eurrent in the leading tube comprising a choke coil connected to the common terminal and in series with the source of alternating current.

5. .A fluorescent tube circuit having a leading tube and a laggin tube therein; means for supplying alternating current; an autbtransiormer connected to said means and having a primary coil and a pair of secondary coils, one secondary coil being connected to the leading tube and the other connected to the lagging tube to operate said tubes, all of said coils having a common termi. nal; and means connected to the primary coil of the autotransformer for varying the wav form or the leading tube without aflecting the wave form of the lagging tube, said means including a choke coil connected in series between the com-- connected to the lagging tube to operate said tubes, all of said coils having a common terminal; and means for reducing the operating current in the tubes for a given watt output at the tubes comprising a choke connected between said common terminal of the transformer and the source of alternating current.

7. A fluorescent tube circuit having a leading tube and a lagging tube therein; a source of alternating current; an autotransformer connected to said source and an autotransi'ormer connected having a primary coil and a pair of secondary coils, one secondary coil being connected to the leading tube and the other connected to the lagging tube to operate said tubes,

ternating current;

a all of the coils having a common terminal; and means for reducing the running current in the to said source and having a primary coil and apair of secondary coils, one secondary coil being connected to the leading tube and the other being connected to the lagging tube to operate said tubes, all of said coils having a common terminal; and means for reducin the starting current in both the leading and lagging tubes for a given watt output at the tubes comprising a choke connected in series between the common terminal of the transformer and the source of alternating current.

8. A fluorescent tube circuit having a leading tube and a lagging tube therein; a source of alleading tube for a given watt output at the tubes comprising a choke connected in series with the common terminal of the transformer.

9. A fluorescent tube circuit having a leading tube and a lagging tube therein; a supply of alternating current; an autotransformer having a core, a pair of secondary coils on the core and a primary coil connected to said source of altemating current, one of the secondary coils being connected to the leading tube and the other connected to the lagging tube, all of said coils having a common terminal; and means including a choke conected in thesupply line to the common terminal for reducing the current requirements of each tube for a given watt output at the tubes.

; GEORGE B. HORN.