US2805364A

US2805364A - Apparatus for starting and controlling electric discharge devices

Info

Publication number: US2805364A
Application number: US241782A
Authority: US
Inventors: Moerkens Jozef Cornelis
Original assignee: US Philips Corp
Current assignee: US Philips Corp; North American Philips Co Inc
Priority date: 1950-09-22
Filing date: 1951-08-14
Publication date: 1957-09-03
Anticipated expiration: 1974-09-03

Description

Se t 3, 195/ .1. c. MOERKENS 2,805,364

APPARATUS FOR STARTING AND CONTROLLING ELECTRIC DISCHARGE DEVICES Filed Aug. 14, 1951 INVENTOR Jozef Cornelis Moerkens By WW Agen APPARATUS FOR STARTING AND CONTROLLING ELECTRIC DISCHARGE DEVICES Jozef Cornelis Moerkens, Eindhoven, Netherlands, as-

signor, by mesnc assignments, to North American Philips Company, Inc., New York, N. Y., a corporation of Delaware Application August 14, 1951, Serial No. 241,782

Claims priority, application Netherlands September 22, 1950 4 Claims. (Cl. 315--95) The present invention relates to a circuit arrangement for starting electric discharge tubes. More particularly, the invention relates to devices comprising a discharge tube which is connected in series with a capacitative im-v pedance and comprises at least one thermionic electrode, whose end remote from the connecting terminals of the device is connected to the other electrode of the tube prior to its ignition.

During operation such a tube takes a current leading the supply voltage. This permits an excellent power factor to be obtained if the device also comprises an inductively stabilized tube taking a lagging current. Furthermore, the stroboscopic effect of a single tube is greatly reduced with the use of leading and lagging tubes, because the dark periods of these tubes do not simultaneously occur.

nited States Patent '0 The warming up of the thermionic electrode. of a In order to heat the thermionic electrode of the capacii tatively stabilized tube rapidly to its emitting temperature, an auxiliary inductor, also termed compensator, is.usually inserted in the parallel circuit of the tube, i. e. in the electrode connection adapted to be interrupted and intended for ignition of the tube. The compensator is so proportioned that the preheating circuit of the thermionic electrode is traversed by a current exceeding 1.2 times and preferably 1.3 to 1.8 times the prescribed discharge current of the tube. On ignition the circuit of the compensator is interrupted, so that this element is out of action during normal operation of the tube.

The present invention provides other means for preheating thermionic electrodes with acurrentrnaterially exceeding the operating current.

According to the invention, the" papacitative seriesimpedance is so proportioned that, when connected directly to the supply, it consumes a current exceeding 1.2 times and preferably 1.3 to 1.8 times the operating current of the tube, at leastpart of the capacitative seriesirnpedance having connected in parallel with it an inductive branch which is interrupted during the preheating period of the thermionic electrode but closed during operation of the tube, and which is so proportioned that the tube is traversed only by approximately 1.0 times the operating current during normal operation.

In a particularly advantageous embodiment of the invention, the inductive parallel branch consists of an inductance in series with a second discharge tube also comprising at least one thermionic electrode, whose end remote from the connecting terminals of the device is adapted to be connected through a switch to the second electrode of this second tube, this switch being open during the passage of preheating current through the thermionic electrode of the first tube. The switch of the inductively stabilized tube may be a switch which is 2,805,364 Patented Sept. 3, 1957 2 open in the deenergized condition and the closing period of which corresponds to at least the preheating period of the thermionic electrode of the capacitatively stabilized tube.

In order that the invention may be readily carried into efiect, it will now be described in detail with reference to the accompanying drawing, in which the single figure is a preferred embodiment of the circuit arrangement of the present invention. The reference numeral 1 denotes a discharge tube, for example a fluorescent lowpressure mercury-vapour discharge tube. Through a capacitor 2 and an inductor 3 the tube is connected to terminals 4 and 5 intended to be connected to a source of alternating current, for example a power supply of approximately 220 volts at 50 cycles per second suitable for feeding the tube. The capacitance l/wC of the capacitor 2 exceeds the inductance @L of the inductor 3, so that at a frequency of 50 cycles per second the seriesconnection of these two elements constitutes a capacitative series-impedance of the tube. The tube comprises thermionic electrodes 6 and 7, Whose ends remote from the connecting terminals may be connected by means of a switch, for example a glow discharge switch that may be bridged by a small capacitor of approximately 10,000 microfarads. As is known, the glow discharge switch is a bimetallic switch located in a gaseous atmosphere said switch being open in the cold state and being so proportioned that its electrodes, when connected to the supply voltage, engage each other but do not contact upon connection to the tube voltage. V

In addition, the device comprises a discharge'tube 9 which is connected, through an inductor 10, in parallel with the inductor 3 and the capacitor 2. The point 11 between terminal 4 and inductor 3 may alternatively be located at a tapping point of they inductor .3 or between said inductor and the capacitor 2. The tube 9 comprises two thermionic electrodes 12, 13 whose ends remote from the connecting terminals 4 and 5 are adapted to be connected through a switch 14, which may also be a glow discharge switch bridged by a small capacitor.

The tubes 1 and 9 are, for example,'fluorescent tubes approximately 120 cms. long and about 318 mms in diameter, which during normal operation consume '40 watts energy with an operating voltage of approximately volts and a current of approximately 440 milliamperes and 420 milliamperes, respectively. The preheating of the thermionic electrodes to the emitting temperature requires a current materially exceeding the aforesaid prescribed operating current of approximately 440 milliamperes and 420 milliamperes, respectively. In order to Warm up the thermionic electrodes. 6 and 7 of tube 1, the elements 2 and 3am soiproportioned that a current of approximately 580 milliamperes .passes through said electrodes with closed switch and open switch 14.

The warming up of the thermionic electrodes 12 and 13 of tube 9 does not involve any appreciable diificulty. As is customary, the inductor 10 is so proportioned relatively to the magnetic saturation as ,to produce the desired pre-heating current through the thermionic electrodes 12 and 13 with closed switch 14 during normal operation of the tube 1.

When using glow discharge switches 8 and 14, which are open in the cold state and supplied from a source of current of approximately 220 volts at 50 cycles per second, the device operates as follows.

On connecting terminals 4 and 5 to the power supply, substantially the full supply voltage is operative across switch 8, thus producing a glow discharge therein, which causes said switch to close. Subsequently the thermionic electrodes 6 and 7 of tube 1 are warmed up either intermittently or continuously in accordance with the cons'truction of said swi'tch. As soon as the emitting temperatu're of the thermionic electrode is reached the tube 1 strikes on opening switch 8. In the closed state of switch 8, a glow discharge tending to close switch 14 also occurs. On reaching the closed state, the thermionic electrodes 12 and 13 of tube 9 are warmed up so that said tube is also adapted to strike. It is advisable that the closing period of switch 14 should be such as to correspond to at least the preheating period of the thermionic electrodes 6 and 7 of tube 1, since otherwise the ignition of the tubes is delayed.

From the foregoing it will be seen that the device does 'not comprise any reactive element which is not utilized during operation of the tubes.

Parallel connection of the inductive tube branch to part of the capacitative tube branch yields particular advantages which are evidentfrom the following:

During normal operation of the tubes a voltage of approximately 100 volts with a current of approximately 420 milliamperes is operative across the inductor 10, so that the power of this inductor is approximately 42 volt amperes; With a current of approximately 450 millia'mperes a voltage of approximately 100 volts is operative across the inductor 3 and a voltage of about 260 volts across the cpaacitor '2, likewise during normal operation. Consequently, the power of inductor 3 is about 45 volt amperes and that of the capacitor 2 about 120 volt amperes. With the same 40 watt tubes, when connected to 220 volts in tube branches independent of each other and lagging and leading respectively, the inductor of the lagging branch requires a power of about 70 volt amperes. The inductor of the leading branch requires a power of about 60 volt amperes and the capacitor of the last-mentioned branch a power of about 160 volt ampres. Consequently, in the device according to the invention, all the reactances for stabilizing the tubes are smaller and cheaper than in tubes supplied independently of one another.

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 skilledin the art without departing from the'spirit and scope of the invention.

What I claim is:

1. A circuit arrangement for starting electric discharge tubes, comprising a source of alternating current at a given frequency, a gas-filled electric discharge tube having a pair of electrodes at least one of which is thermionic and adapted to operate with a given current, a capacitative impedance connected in series with said source and 2. A circuit arrangement for starting electric discharge tubes, comprising a source of alternating current at a given frequency, a gas-filled electric discharge tube having a pair'of electrodes at least one of which is thermionic and adapted to operate with a given current, a capacitative impedance connected in series with said source and said tube, normally-open switching means interconnecting the electrodes of said tube in series with said capacitative impedance and said source, said capacitative impedance having an impedance at which a current exceeding 1.2 times said given current traverses the thermionic electrode when said switching means is closed, a predominantly inductive circuit connected in parallel with a portion of said capacitative impedance, said inductive circuit comprising an inductor, a second gas-filled discharge tube having a pair of electrodes at least one of which is thermionic connected in a series with said inductor, a normallyopen switch interconnecting the electrodes of said second tube and adapted to be closed a pre-determined time interval after the switching means is closed, said inductive circuit having an impedance at which a current of about 1.0 times said given current traverses said first tube when ignited, and means for closing said switching means to thereby effect ignition of said tube.

3. A circuit arrangement for starting electric discharge tubes, comprising a source of alternating current at a given frequency, a gas-filled electric discharge tube having a-pair of electrodesat least one of which is thermionic and adapted to operate with a given current, a capacitative impedance connected in series with said source and said tube, normally-open glow discharge switching means said tube, normally-open switching means interconnecting the electrodes of said tube in series with said capacitative impedance and said source, said capacitative impedance having an impedance at which a current exceeding 1.2 times said given current traverses the thermionic electrode when said switching means is closed, a predominantly inductive circuit connected in parallel with a portion of 'said capacitative impedance including a normally-open interconnecting the electrodes of said tube in series with said capacitative impedance and said source, said capacitative' impedance having an impedance at which a current exceeding 1.3 times said given current traverses the thermionic electrode when said switching means is closed, a predominantly inductive circuit connected in parallel with a portion of said capacitative impedance, said inductive circuit comprising an inductor, a second gas-filled discharge tube having a pair of electrodes at least one of which is thermionic connected in series with said inductor, a normally-open glow discharge switch interconnecting the electrodes of said second tube and adapted to be closed, a predetermined time interval after the switching means is closed, said inductive circuit having an impedance at which a current of about 1.0 times said given current traverses said first tube when ignited, whereby application of potential will close said switching means and thereby etfect ignition of said tube.

4. A circuitarrangement as :claimed in claim 3 in which the pre-deterrnined time interval after which the switch closes corresponds to the time for preheating the thermionic electrode of the first tube.

References Cited in'thefile of this patent UNITED STATES PATENTS 2,056,661 .Foulk'e' Oct. 6, 1936 2,298,935 Freeman Oct. 13, 1942 2,358,810 Karash Sept. 26, 1944 2,363,868 Karash Nov. 28, 1944 2,386,914 Slepian Oct. 16, 1945 2,423,031 Kurtz June 24, 1947