US2829311A - Low-pressure arc discharge tube arrangement - Google Patents

Description

April 1, 1958 .1. c. MOERKENS 2,829,311

LOW-PRESSURE ARC DISCHARGE TUBE ARRANGEMENT Filed April 24, 1955 INVEN TOR JOZEF conueus, MOERKENS AGENT United States Patent-- LOW-PRESSURE ARC DISCHARGE TUBE ARRANGEMENT Jozef Cornelis Moerkens, Eindhoven, Netherlands, as-

signor, by mesne assignments, to North American Philips Company, Inc., New York, N. Y., a corporation of Delaware Application April 24, 1953, Serial No. 350,807 Claims priority, application Netherlands May 15, 1952 4 Claims. or. 315-138) The invention relates to low-pressure arc discharge tube arrangements without any provision for ignition switches, more particularly to fluorescent lamps comprising two activated main electrodes and at least one auxiliary electrode arranged Within the discharge space on the wall of the discharge vessel, connected electrically within the discharge space to one of the main electrodes, insulated from the other main electrode and extending parallel to the discharge path, and comprising in addition a rare gas-filling at a pressure of a few mm.

' When a tube of the foregoing type is connected in series with a suitable stabilizing impedance to a current source of suitable voltage, a glow discharge occurs between the main electrode connected as the cathode and the end of the auxiliary electrode insulated therefrom,

which, emanating from the cathode, travels along the auxiliary electrode onto the main electrode electrically connected thereto. As soon as one of the main electrodes assumes emission temperature, the glow discharge is converted into an arc discharge between the main electrodes.

It has been observed that the life of such tubes is a voltage which exceeds the supply voltage, and since the discharge current of this tube traverses a portion of the first inductance, an increased voltage is also applied across the other tube connected in series with the entire first inductance.

The portion of the first inductance which is common to both tube circuits and the impedance ofthe auxiliary reactance are preferably proportioned such that the starting voltage of the tube connected in series with the capacitor exceeds the starting voltage of theother tube..

At a supply voltage of approximately 220 volts, the number of turns of the first inductance which are included in both tube circuits may be from 10 to 20% of the total number of turns thereof.

The invention will now be described with reference to the accompanying drawing, wherein the single figure is a schematic diagram of an embodiment of the circuit arrangement of the present invention.

Referring now to the figure, there are provided two low-pressure arc. discharge tubes 1 and 2, for example,

about 120 cms. in length, having an internal diameter" of approximately 35 mms. and containing an argon filling' at a pressure of approximately 3 mms. in addition to asrnall supply of mercury. The tubes 1 and 2, each of which has the inner surface of its discharge vessel coated with a fluorescent layer (not shown), each comprise two main electrodes 11, 12 and 21, 22 respectively,

which are activated by means of barium-strontium compounds, and an auxiliary electrode 13 and 23, respectively. 'The auxiliary electrodes consist of a mixture of. graphite and glazing and are applied to the inner-surface of the tube wall in the form of an approximately -3 detrimentally affected by the number of tube-starting operations. At a rated power supply voltage of 220 volts the tube can be started only several hundreds of times on an average, and if the tube is kept in use each time for a short period only, the result is an insufiiciently short life.

, According to the invention, it has been found that the number of times the tube can be ignited is increased as the period of time between the tube being energized and the arc discharge being efifected is decreased. It has also been found that at an effective A. C. voltage of approximately 240 volts or more, the said period of time is reduced to a small fraction of a second, and hence the number of times the tube can be started'is greatly increased. Moreover, at effective A. C. voltages exceeding approximately 280 volts, no appreciable supplementary 240 to 280 volts. One of the tubes is connected in series with an inductance to the A. C. supply of the system and the other tube is connected to this supply in series with a second inductance, a capacitor having a reactance which exceeds that of the second inductance, and a portion of the first inductance. The reactance more remote from the first inductance, i. e., the second inductance or the capacitor, is connected to the current supply in series with an auxiliary reactance which takes a current of the opposite sense.

The provision of the auxiliary reactance ensures that the tube connected in series with the capacitor ignites at mm. wide strip running substantially the whole length of the tube and which are connected to one of the main electrodes and exhibit a resistance of approximately .20 to 30 ohms per cm. If required, each tube may include a second auxiliary electrode connected to the other main electrode.

Connected across the terminals 7 and 8 of an A. C.;

supply of 220 volts, 50 cycles per second, are the tube 1 through a first inductance or choke 3 and the tube 2 through a capacitor 4, a second inductance or choke- 5 and a portion 6 of the choke 3. An auxiliary inductanceor choke 9 is connected in parallel with'the tube 2,'

the choke 5 and the portion 6 of the choke 3, and in series with the capacitor 4.

The choke 3 contains, for example, 1480 turns, and at a voltage of 175 volts across its ends carries a current of 0.42 ampere, thereby exhibiting an impedance of approximately 420 ohms. The portion 6 comprises 235 turns and, hence, approximately 16% of the total number of turns of the choke 3.

The capacitor 4 has a capacitance of, for example, 5 microfarads, that is to say, an impedance of approximately 635 ohms.

At a voltage of 100 volts, the choke 5 carries a current of 0.44 ampere so that its impedance is approximately 230 ohms.

At a voltage of 270 volts, the auxiliary choke 9 carries a current of 0.07 ampere and at a voltage of 180 volts it carries a current of 0.03 ampere, so that in these conditions its impedance is approximately 3850 and 6000 ohms, respectively. The voltage-ampere product deciding emen The phase-leading discharge current of the tube 2 passing through the portion 6 of the choke 3 produces a voltage of 255 volts across the tube 1, whereupon this tube,

also attains the are discharge condition almost at once.

All this ensues so quickly that the glow discharge periods.

of the tubes can o'nlybe observed at a greatly reduced voltage.

The number of turns of the portion of the choke 6 7 2strikes. has 220 volts applied to it and might ignite at this voltage,,is thus prevented from being kept in suspense in the glow discharge condition for an excessively long period.

Under normaloperating conditions, the voltage across the tube 1 is approximately 110 volts .at a tube current o'fl'approximatelyOAZ ampere; the'voltage across the tube 2 in this condition is approximately 110 volts at a tube current of approximately 0.44 ampere. In this case, the current passing through the auxiliary choke 9 is approximately 0.03 ampere, that passing through the capacitor 4 approximately 0.475 ampere, and the total current supplied by the current source approximately 0.45 ampere.

The wattless currents or apparent power of the tube circuitsiare of opposite sense, so that the power factor ofith'e arrangement has a high value. The stroboscopic effect ofth'e device is low, since the dark periods of the tubes do not occur. simultaneously.

With the invention, the life of the tubes is several thousands of tube starting operations.

1 While I have described myinvention in connection with specific embodiments and applications, other modifications thereofwill'be readily apparent to those skilled inlthi's'art without departing from the spirit and the scope offtlie invention as defined in the appended claims.

' What is claimed is:

l. A circuit arrangement comprising a pair of .low pressure arc-dischargev tubes each having a pair of activated main electrodes and an auxiliary electrode, a source of potential at a given alternating frequency, a firstinductance 'in series with said source and one of said tubes, asecond inductance and the other of said tubes connected in series circuit arrangernent, means for connecting said.

series circuit in series with a portion of 'said first 'inductance, a capacitative reactance connectedin series with said series circuit arrangement and said source, said capacitative reactance having-a'value exceeding the value of said second inductive reactance at said frequency, and an auxiliary inductive reactance connected in series with said source and said capacitative reactance.

.-2. An arrangement as claimed in claim 1, in which said .portion of saidfirst inductance and the impedance of the-auxiliary reactance are proportioned such that the starting voltage of said other tube exceeds the "starting voltage ofsaid one tube.

' 3. An arrangement as claimed in claim 2, in which the number of the turns of said portion of the-first 'inductance is from 10 to 20% of the total number of turns of the first inductance.

4. A circuit arrangement including a pair of low pres sure arc-discharge tubes each having a pair of activated main .electrodes, a pair of terminals connected respectively to said pair of main electrodes, an auxiliary electrode connected to one of said main electrodes and extending through the tube to the vicinity of but insulated from said other main electrode, and a rare gas-filling at a pressure of a few mm.; said arrangement further comprising a source of potential at a given alternating frequency, a first inductance in series with said source and I one of said tubes, a second inductive reactance connected to one terminal of the other-of said tubes and in seriesv with a portion only of said first inductance, a capacitative reactance connected to the other terminal of said other tube and in series with said second inductive reactance and said source, said capacitative reactance exceeding the value of said second inductive reactance at said given frequency, and an auxiliary inductive reactance connected to said other terminal of said other tube and in series with said source and said capacitative reactance.

References Cited in the file of this patent UNITED STATES PATENTS 2,025,471 Osborne Dec. '24, 1935 2,301,671 Abadie Nov. 10, 1942 2,314,311 Karash Mar. 16, 1943 2,504,549 Lemmers Apr. 18, 1950 2,518,767 Freeman Aug. 15, 1950 Hall Nov. 10, 1953

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