US2794938A

US2794938A - Low-pressure arc-discharge tube arrangement

Info

Publication number: US2794938A
Application number: US413881A
Authority: US
Inventors: Moerkens Jozef Cornelis
Original assignee: US Philips Corp
Current assignee: US Philips Corp; North American Philips Co Inc
Priority date: 1953-03-05
Filing date: 1954-03-03
Publication date: 1957-06-04
Anticipated expiration: 1974-06-04

Description

June 4, 1957 J. c. MOERKENS 2,794,938

Low-PRESSURE ARC-DISCHARGE TUBE ARRANGEMENT Filed March 3, 1954 INVE NTO R JOZEF CORNELIS MOERKENS LOW-PRESSURE ARC-DISCHARGE TUBE ARRANGE Jozef Cornelis Moerkens, Eindhoven, Netherlands, assignor, by mesne assignments, to North American Philips Company, Inc., New York, N. Y., a corporation of Delaware Application March 3, 1954, Serial No. 413,881 Claims priority, application Netherlands March 5, 1953 3 Claims. (Cl. 315-138) The present invention relates to a low pressure arc-discharge tube arrangement. More particularly, the invention relates to an arrangement without a starting switch for operating two low-pressure arc-discharge tubes, es-

pecially, but not exclusively, fluorescent lamps. Each comprises two activated main electrodes and at least one auxiliary electrode which is disposed within the discharge space on the wall of the discharge vessel, and is connected electrically within the discharge space to one of the main electrodes and is electrically insulated from the other main electrode and extending parallel to the discharge path. Each tube has, in addition, a rare gas filling at a pressure of a few mm. According to the invention, one tube is arranged for connection to an A. C. supply of the arrangement in series with a first inductance, the other tube being arranged for connection to said supply in series with a second inductance and with a capacitor, whose impedance exceeds that of the second inductance, and in series with part of the first inductance, in which arrangement the series-combination of the tube connected in series with the capacitor, of the second inductance and of said part of the first inductance is shunted by an auxiliary inductance.

, ited States Patent choke part 6, while the part 9293 is connected in series As a result of this arrangement the two tubes ignite at V a voltage exceeding the supply voltage, to the effect of attaining the arc-discharge condition very rapidly, whereby the number of times the tube can be brought into circuit is greatly increased.

Difficulties may, however, be experienced if one of the tubes becomes defective.

If, for example, the tube connected in series with the capacitor (that is to say the capacitatively stabilized tube) fails, only the supply voltage is available for igniting the other (inductively stabilized) tube, since the voltageincreasing influence of the capacitative tube branch is lacking. Due to this, the inductively stabilized tube will either not ignite or it will attain the arc-discharge condition in an undesirably slow manner and take a current smaller than the normal operating current.

If, in contradistinction thereto, the inductively stabilized tube is defective, the capacitatively stabilized tube will take a current exceeding the normal operating current.

According to another feature of the invention, said disadvantages are substantially eliminated if the auxiliary inductance constitutes the voltage-increasing secondary winding of a transformer, the primary winding of which is connected, in series with the capacitor, to the current supply of the arrangement.

At a supply voltage of approximately 220 volts it is advantageous for the number of primary turns of said transformer to be 82 to 95% of that of the secondary turns. In this case, the number of turns of the first inductance, connected in the two tube circuits, is 20 to 30% of the total number of turns of the first inductance.

In order that the invention may be readily carried into effect, it will now be described in greater detail with reference to the accompanying drawing, in which the single Patented June 4, 1957 ice rescent layer (not shown) comprise two main electrodes 11, 12 or 21, 22, which are activated by barium-strontium compounds, and an auxiliary electrode 13 or 23. The

auxiliary electrodes consist of a mixture of graphite and glaze and are applied to the inner surface of the tube wall in the form of a strip approximately 3 mins. wide running substantially the whole length of the tube. The strips are each connected to one of themain electrodes and have a resistance of approximately 20 to 30 ohms per cm. If desired, each tube may comprise a second auxiliary electrode connected to the other main electrode.

The tube 1 is connected across terminals 71 and 8 of an A. C. supply of 220 volts, 50 cycles per second through a choke 3. The tube 2 is connected through a capacitor 4, a choke 5 and a part 6 of the choke 3. Both tube circuits further comprise a part 9192 of an auxiliary choke 9 whose total number of turns 9193 is connected in parallel with the series combination of tube 2, choke 5 and with the capacitor 4 to the supply 71-8.

In this case, the auxiliary choke 9 consequently constitutes a transformer with the part 92-93 acting as a primary winding and the part'91--93 as a secondary winding.

When applying the invention only in part by connecting the terminal 71 of the supply to that end 91 of the auxiliary choke 9 which is connected to the choke 3, in-

stead of connecting it to the tapping point 92, the arrangement would operate as follows:

Upon connecting the arrangement to the supply, a current passing through the capacitor 4 and the auxiliary choke 9 produces a voltage of approximately 270 volts across said auxiliary choke and hence also across the tube 2. At this voltage the tube 2 strikes and attains the arcdischarge condition within a small fraction of a second. The phase-leading discharge current passing through the part 6 of the choke 3 sets up a voltage of approximately 255 volts across the tube 1, that is, a voltage in excess of the supply voltage of 220 volts of the arrangement,

whereupon this tube also attains the arc-discharge condition nearly at once. During normal operation, the inductively stabilized tube 1 takes a current of approximately 420 milliamperes at an operating voltage of approximately volts, while the capacitatively stabilized tube 2 takes a current of approximately 440 milliamperes at an operating voltage of about 110 volts. It is to be noted that each tube consumes approximately 40 watts; the slightly higher discharge current of the tube 2 resulting from the occurrence of higher harmonics in the capacitative circuit of this tube.

Should the tube 2 fail to ignite, no phase-leading current will pass through the part 6 of choke 3, so that only the supply voltage having a nominal value of 220 volts is set up across the tube 1 for ignition. It is not certain whether the tube 1 will ignite under such conditions, but if it does ignite, it will take a current much smaller than 420 milliamperes, since the reaction of the capacitative current branch of tube 2 is failing. If, however, the tube 1 becomes out of order, the tube 2 takes a current greatly exceeding 440 milliamperes, since the reaction of the inductive current branch of tube 1 is failing.

Said disadvantages are mitigated, or even substantially eliminated, according to the other feature of the invention, since the auxiliary inductance 9 constitutes the volt- In the that the terminal 71 of thesupplyisinot connectedtotpoint 91 but to point 92 of the auxiliary inductance 9. Y

It will be evident that,.as a result of this, the voltage set up across tube 1 will exceed 220 volts if tube 2.is out of order and that, in this event, the tube 1 will take :more currentthan it would without thevoltage-increasing efliect of the auxiliary inductance9. 1

The. connection of. the terminal .71 to point 92 also results, in case the tube 1 is defective, in the tube ,2 taking less current than if the terminal 71 is: connected to point 91. This will be readily appreciated whenconsidering that the tube 2 does nottakecurrentif the terminal 71 is connected to point93 :of the auxiliary inductance 9, and that said tube takes a maximum current with the terminal71 connected to point 91. If the terminal 71 is connected to an intermediate point,.for examplepoint 92, the current taken is smaller'than the. maximum value and exceeds zero.

In one particular case, the 'number of secondary turns was 2485, the number of primary turns was 220.0,,thatis, 88% of the number of secondary turns. Through the part 92-93 of the auxiliary choke '9 and thecapacitor 4 of 5.5 microfarads passed a .no-load current of 67 milliamperes; a no-load voltage of approximately .266 volts being setup across tube 2 and a no-load voltage of approximately 250 volts being set up :across tube .1. During operation of tube 2, a no-load voltage of approximately 262 volts was set up across the tube 1, a no-load voltage of approximately 25.6 volts beingset up across tube,2 during operationof tube 1.

During normal operation, .a current of approximately 32 milliamperes flowed through the part 92-93, approximately 460 milliamperes flowed through the part 91-92, approximately. 440 milliamperes flowed through tube 2, approximately 420 rnilliamperes flowed through tube 1, approximately 485 milliamlperes flowed through the capacitor 4, a voltage of approximately 1194 volts was set up across the part 91-93 of the auxiliary choke 9, a voltage of approximately 185 volts was set up across the choke 3, the overall current-taken was approximately 470 milliamperes and the power factor was approximately 0.95.

Each. of. said tube currents remained substantially independent of the .fact whether the other .tube was in or out of operation. In this case, the coil 3. had 1580 turns I The choke 5 was rated for 100 volts, 0.44 ampere and consequently had an impedance of approximately 230 ohms. 1

While the invention has been described by means of a specific example and in a specific embodiment, I do not Wish to be limited thereto, for obvious modifications will occur to those skilled in the art without departing from t the spirit and scope of the invention.

What is claimed is:

l. Acircuit-arrangement for operating two low-pressure arc-discharge tubes without a starting switch, each of said tubes comprising two activated main electrodes .and at least one auxiliary electrode disposed within the discharge space on the wall of the discharge vessel and connected electrically within the discharge space to one of said main electrodes and electrically insulated from the other of said main electrodes and extending parallel 'to the discharge .path of said tube, and each tube furtherand its part 6 had .3 turns, that is, approximately 25% 5 of the total number of turns.

more having arare-gas fillingat a pressure of a few millimeters, said circuit-arrangementcomprising a first series circuit including a first inductance and one of said two tubes, an alternating voltage source, a second series circuit'including a second inductance, a capacitor having an impedance exceeding that of said second inductance at the frequency of the voltage of said source, and the other of said twotubes, said second series circuit being connected between an intermediate point on said first inductance and one terminal of said voltage source, a connection from said one terminal ofsaid voltage source to the end ofthe one of said tubes .remote from said first inductance, and a transformer having a primary Winding connected in series with said capacitor across said voltage source and a voltage increasing secondary winding connected between the end of said first inductance remote from said one tube .and the terminal of said capacitor remote .from said .one terminal.

2. A circuit-arrangement as set forth in claim 1, whereinsaid primary winding has 82 .to percent of the number of turnsof that of saidsecondary winding.

3. A circuit-arrangement as set forth in claim 2, wherein said first inductance has 20 to 30 percent of its total number of turns disposed between said remote end and intermediate point of said first inductance.

References Cited in the file of this patent UNITED STATES PATENTS 2,301,671 .Abadie Nov. 10, 1942 2,314,311 Karash Mar. 16, 1943 2,462,336 Ruff Feb. 22, 1949