EP0027764A1 - Method and device for enhancing ionization in gas discharge tubes, and lighting installation relating thereto - Google Patents

Abstract

On the appearance of each alternation, there is applied to the electrodes of the lamp an exciting voltage which grows more rapidly, and tends towards a higher maximum value (Vm) than the peak value (Vc) of the supply voltage (Vr), and following arcing, the voltage across the electrodes of the lamp is permitted to return to the arc voltage (Va). Use in public lighting, lighting of warehouses, department stores or sorting stations, in order to permit reduction in energy consumption during off-peak periods. <IMAGE>

Description

The invention relates to a method for promoting the ionization - or ignition - of discharge lamps - or tubes -, such as fluorescent or metallic vapor lamps, or the like.

The invention also relates to a device for implementing this method.

The invention further relates to an installation comprising at least one discharge lamp and a device for promoting its ionization.

Faced with the increasing increase in the cost of energy, in general, therefore of electrical energy, in particular, and of a declining availability of said energy, it is sought to reduce consumption within the limit of the minimum acceptable.

Although the share of electrical energy consumption due to lighting is relatively low compared to total consumption, it is desirable to limit it as well.

In particular, so-called public lighting installations such as street lighting, marshalling yards, large commercial areas, or other, consume an appreciable amount of electrical energy, resulting in increasing expenditure. However, this consumption could be reduced during periods of less frequentation or less activity to become almost zero at certain hours or in certain circumstances.

The majority of these installations are equipped with discharge lamps so far alone capable of offering an intensity of luminous flux as well as a suitable output.

These lamps are distributed on networks currently supplied with industrial alternating current (50 or 60 Hz) and under low voltage (220 Volts, single-phase, nominal voltage, for example).

To reduce consumption during the hours hollow, one can consider reducing the supply voltage of the lamps.

Unfortunately, this method is, in practice, difficult to apply in view of the particular behavior of discharge lamps to which a voltage reduction is applied.

In fact, when the network voltage supplying a discharge lamp is reduced even by a small value, there is the appearance of an "arc reaction" resulting in a rapid increase in the arc voltage , which carries with it the ionization threshold voltage.

This phenomenon linked to the inertia of the plasma generated by the ionization will not disappear and, therefore, the arc voltage will not resume its equilibrium value until several minutes after the moment of the initial disturbance.

The variation of the arcing voltage being carried out in the opposite direction to that of the supply voltage, the potential difference then remaining available is reduced by an amount much greater than the variation imposed on the supply voltage.

Admittedly, it is known to stabilize the arc of discharge lamps, and this stabilization is generally carried out by means of an inductor mounted in series with the lamp.

In certain cases, the arc voltage of the lamp is too high compared to the voltage of the supply network, so that the operation of the lamp is impossible without an additional device raising the supply voltage.

Even if the discharge lamp is able to function correctly under mains voltage by means of the conventional mounting of an inductor in series, it nevertheless functions more stable if it is supplied from a voltage higher than the mains voltage. . Its arc current must then be stabilized by a higher inductance adapted to this higher voltage.

An autotransformer can be used for this purpose, taking care to adapt the inductance connected in series with the lamp to the higher voltage to stabilize the arc.

Under such conditions, it then appears possible to operate the lamp, in a stable manner, in slightly reduced power mode, by simple reduction of the supply voltage, for example using a voltage variator.

However, this reduction in power is in many cases insufficient and, in return for the advantages set out above, the mounting of a step-up autotransformer has many drawbacks.

The autotransformer transfers a relatively large power, approximately equal to the product of the overvoltage it generates by the arc current. The autotransformer is therefore bulky and expensive, and notably increases the energy consumption of the lamp, which goes against the desired objective.

The compensation capacity, as well as the stabilization inductance which constitute the supply apparatus - or ballast - are greater than those customary designed for the nominal voltage of the network, and their costs and size are therefore greater.

Such an autotransformer cannot therefore be connected directly to the supply apparatus.

The aging of discharge lamps leads to an additional difficulty due to ionization of the plasma (ignition) which becomes more and more difficult then, ultimately, no longer occurring, even under a nominal supply voltage.

The lamps which have reached this state can sometimes only rekindle if the supply voltage is appreciably increased, which goes against the aim sought.

• . elles manifesteront un cycle répétitif d'extinctions et de ré-allumage ;
• . elles s'éteindront définitivement la première manifestation étant, d'ailleurs, annonciatrice de la seconde.

If you want to reduce the tension power supply, even at a low rate of change, the aged lamps of a network will react, depending on their condition, in two possible ways:

• . they will manifest a repetitive cycle of extinctions and re-ignition;
• . they will be extinguished definitively the first event being, moreover, heralding the second.

This behavior of discharge lamps in the aged state makes it impossible to reduce consumption by reducing the supply voltage since, for reasons of physiological discomfort and / or safety, it is inadmissible to leave portions of space in the 'darkness.

The object of the invention is to remedy the drawbacks inherent in discharge lamps by proposing a method for promoting the ionization or ignition of these lamps, even when aged and with appreciable reduction in their supply voltage.

According to the invention, the method for promoting the ionization of discharge lamps, is characterized in that at the appearance of each alternation, a difference in excitation potential is applied to the electrodes of the discharge tube which increases more rapidly and tends towards a maximum value higher than the difference in operating potential normally produced by the supply voltage, in order to achieve the difference in ionization potential of the tube even when the supply voltage is significantly lower than the nominal supply voltage or when the discharge tube is in an advanced state of wear, and in that the return to the initial supply conditions is allowed when the current begins to build up in the discharge lamp.

The difference in excitation potential ensures the ignition of the lamp at the appearance of each alternation, since its rapid growth causes it to a level of potential at least equal to the ionization threshold potential of the lamp.

After birth, the ionization is maintained as long as a potential difference, even a relatively small one, is present between the two electrodes of the discharge tube.

According to another object of the invention, the device for promoting the ionization of discharge lamps, which comprises an autotransformer wound in voltage booster, and whose primary winding is intended to be supplied from a voltage source , and the secondary winding is intended to be mounted in series with the discharge lamp to be stabilized, is characterized in that this autotransformer comprises means for practically neutralizing, under load, the voltage raising function of the autotransformer, these means generating magnetic leaks manifested when charging the autotransformer.

When the lamp is off, the autotransformer operates at no load and provides the overvoltage favorable to the initial ignition or to the bi-periodic lamp restrikes.

On the other hand, under load, the overvoltage induced in the secondary winding as well as the inherent impedance of this winding, take a very low value.

Thus, the power of the autotransformer is practically zero, so that its dimensions, its price and its energy consumption are very reduced compared to the autotransformers employed in accordance with the state of the art.

It will be noted that the device according to the invention proceeds from a different approach from that taught by the state of the art which encourages to continuously increase the supply voltage of the discharge lamps; moreover, the person skilled in the art was dissuaded from making an autotransformer which did not provide an overvoltage under load.

According to a third object, the lighting system, which comprises at least one discharge lamp, an apparent _re i _ll supply age, and a device for promoting ionization of the above kind, is characterized in that that the switchgear is of the usual type suitable for the supply voltage and that the device is mounted between the supply switchgear and the lamp.

The device can be either attached to or integrated into conventional power supply equipment.

Other features and advantages of the invention will emerge from the description below.

• . la figure 1 est un graphique qui visualise le fonctionnement d'une lampe à décharge alimentée selon l'état de la technique, pendant une alternance ;
• . la figure 2 est un graphique montrant l'influence d'une baisse de la tension d'alimentation sur la lampe à décharge de la figure 1 ;
• . la figure 3 est un graphique montrant comment fonctionne une lampe à décharge alimentée selon l'état de la technique en fonction de la tension d'alimentation ;
• . la figure 4 est un graphique visualisant 1' application du procédé conforme à l'intention au cours d'une alternance ;
• . ]a figure 5 est une vue schématique d'une installation conforme à l'invention, à puissance d'éclairage variable ;
• . la figure 6 est une vue schématique d'une installation d'éclairage conforme à l'invention, à deux puissances d'éclairage ; et
• . la figure 7 est une vue d'une variante de l'installation de la figure 5.

In the appended drawings, given by way of nonlimiting examples:

• . FIG. 1 is a graph which displays the operation of a discharge lamp supplied according to the state of the art, during a half-cycle;
• . Figure 2 is a graph showing the influence of a drop in the supply voltage on the discharge lamp of Figure 1;
• . FIG. 3 is a graph showing how a discharge lamp powered according to the prior art works as a function of the supply voltage;
• . FIG. 4 is a graph showing the application of the method according to the intention during an alternation;
• . ] Figure 5 is a schematic view of an installation according to the invention, with variable lighting power;
• . Figure 6 is a schematic view of a lighting installation according to the invention, with two lighting powers; and
• . FIG. 7 is a view of a variant of the installation of FIG. 5.

In FIGS. 1, 2 and 4, the voltage V in Volts has been plotted on the ordinate, and the phase t in degrees of angle on the abscissa.

Figure 1 reproduces, for an alternation, what is observable, by means of an oscilloscope for example, at terminals of a discharge lamp with respect to the supply voltage V _r supplied by the network. In this figure, the discharge lamp is normally supplied via its stabilizing apparatus - or ballast - at a nominal network voltage (corresponding to 220 V rms, for example), and has reached its established speed.

The phase shift introduced by the ballast has been deliberately omitted in this figure in order to simplify the explanation, but it should however be noted that this phase shift complicates the phenomena described below.

It is noted that the voltage Ve at the electrodes of the lamp follows the curve of the supply voltage V until it reaches the ionization voltage Empties the lamp. Consequently, the voltage at the terminals of the lamp decreases then stabilizes at an arc voltage V while the supply voltage V _r increases to its peak value V. When the voltage V _r again becomes lower than the arc voltage V _a , the voltage V _e at the lamp electrodes again becomes identical to the supply voltage V.

If the effective voltage of the network supplying this lamp is reduced, even by a small value (Δ V _re ) (see FIG. 2), there is an "arc reaction" R a resulting in a rapid and appreciable increase of the arc voltage moving from V _a to V _a 'and bringing with it the ionization threshold voltage from V. to V'.

The variation AV and the arc reaction R being opposite in opposite directions, the potential difference remaining available between the new ionization threshold voltage V. and the reduced peak voltage V 'decreases by an amount much greater than Δ V _re . This amounts to saying that the potential difference developed at each instant between the electrodes of the discharge tube becomes smaller as a result of this phenomenon.

FIG. 3 represents the results of laboratory tests on mercury vapor lamps, nominal power equal to 250 W for an effective voltage of 220 V, having operated for 200 hours.

In this figure, the effective supply voltage is plotted on the abscissa and the power of the lamp on the ordinate.

From an effective voltage below 200 V, the operation of the lamp becomes unstable (point Pl), and below 180 to 185 V depending on the lamps tested, there is total extinction of the lamps, although the drop from the nominal voltage is only 15 to 20%.

It should however be noted that a slightly larger drop is possible without extinction if the voltage variation is slow.

• . même pour des lampes fortement vieillies ;
• . sous réduction appréciable (Δ V_re) de leur tension d'alimentation, de l'ordre de 50 % ;
• . sous un taux de variation de réduction (-A V_re/ A t) relativement important ou rapide, A t désignant le temps pendant lequel s'effectue la variation A V_re.

The aim sought by the process according to the invention consists in ensuring, with flexibility, the ignition (ionization) of the discharge lamps:

• . even for heavily aged lamps;
• . under appreciable reduction (Δ V _re ) of their supply voltage, of the order of 50%;
• . under a relatively large or rapid reduction variation rate (-AV _re / A t), A t designating the time during which the variation AV _{re takes place} .

• . on sait que l'ionisation du milieu (plasma) contenu dans le tube à décharge se maintient, après avoir pris naissance, tant qu'une différence de potentiel, même relativement faible, est présente entre les deux électrodes du tube à décharge ;
• . on sait aussi que l'ionisation ne prend naissance dans le milieu que si les électrons s'y déplaçant acquièrent une énergie cinétique suffisante pour provoquer avec les atomes présents des collisions telles qu'il y ait multiplication desdits électrons et ce, avec une telle densité que le milieu en devienne conducteur.

Two phenomena are known:

• . it is known that the ionization of the medium (plasma) contained in the discharge tube is maintained, after having arisen, as long as a potential difference, even a relatively small one, is present between the two electrodes of the discharge tube;
• . we also know that ionization does not arise in the medium unless the electrons moving there acquire sufficient kinetic energy to cause collisions with the atoms present such that there is multiplication of said electrons and this, with such density let the environment become its conductor.

It is the electric field, due to the difference of potential applied to the two electrodes of the discharge tube, which is proportionally responsible for the force vector fe applied to each electron (f = K.dv / dl, where K is a proportionality factor and dv / dl the voltage gradient between the electrodes ) and, consequently, of the increasing kinetic energy which is given to it during its displacement in the direction of the opposite charge electrode (momentarily positive in this case). If each electron thus moving strikes an ambient atom with sufficient kinetic energy it will result from this shock the creation of new electrons (secondary emission) in their turn accelerated by the electrostatic field with emission of photons producing light.

Therefore, for a given medium, the birth of ionization (initiation) depends on the potential gradient to which it is subjected and, in the case considered here, on the potential difference applied to the electrodes of the discharge tube.

• . la diminution de la différence de potentiel appliquée aux électrodes du tube à décharge d'une part, accompagnée d'une réaction d'arc en sens opposé d'autre part, n'ont d'autre effet que de réduire le gradient de potentiel effectif proposé aux électrons primaires chargés d'initier l'ionisation ;
• . les tubes à décharge vieillis se comportent selon l'une des deux hypothèses généralement admises suivantes :
• - soit la population des électrons primaires est insuffisante, bien que le gradient de potentiel proposé soit normal (tension nominale) ;
• - soit ces électrons acquièrent l'énergie cinétique convenable mais se meuvent dans un milieu devenu résistant pour des raisons qui ne sont pas encore toutes connues.

The observations made for a long time by those skilled in the art and recalled above can be summarized as follows:

• . the decrease in the potential difference applied to the electrodes of the discharge tube on the one hand, accompanied by an arc reaction in the opposite direction on the other hand, have no other effect than to reduce the effective potential gradient proposed to primary electrons responsible for initiating ionization;
• . aged discharge tubes behave according to one of the following two generally accepted assumptions:
• - either the population of primary electrons is insufficient, although the potential gradient proposed is normal (nominal voltage);
• - Either these electrons acquire suitable kinetic energy but move in a medium that has become resistant for reasons which are not yet all known.

In both cases, the desired electron density and necessary is not reached.

The process here described basically involves increasing the acceleration of the primary electrons initially t _e cores ionization in the subjecting, for a short time, a gradient of substantially higher potential to the usual value or "normal".

In practice, the method consists in applying, to the electrodes of the discharge tube, by an appropriate means, a potential difference increasing faster than, and tending towards a maximum value V _m greater than that normally produced by the normal nominal supply voltage. and this, from the onset (zero crossing) of each alternation (see Figure 4).

At the start of the alternation, the potential difference at the electrodes of the lamp (trace L of FIG. 4, observed with the oscilloscope) increases with a slope β greater than the slope α of the supply voltage V _r , and tends towards a value V _m greater than the peak value V _c resulting from the supply voltage V. As soon as the voltage V _i is reached, and that the ignition is consequently initiated, the potential difference at the electrodes of the lamp falls back to the value of the arc voltage V. Therefore, the discharge lamp operates under the conditions corresponding to the supply voltage.

In particular, if the ionization voltage of a discharge tube is aged, e.g., at V _{i s} di tan- that the peak voltage of the supply voltage V network intentionally reduced is at a level V lower than V _i , this tube will not be able to ionize under these conditions. The application of the method will have the effect, at time t., Of producing between the two electrodes of the discharge tube a potential difference in excess of the value V _i , thus initiating an ionization which will subsequently be maintained. .

It should be noted that the production of this excess voltage does not entail the need to accompany it with a notable reserve of energy. Indeed, the discharge tube being then extinguished, the amplified rise in the potential difference proposed to the discharge tube takes place in almost static conditions. The only tiny energy required is that corresponding to the initiation of the current in the plasma, that is to say the displacement of a population of electrons much lower than that which will subsequently maintain the ionization, therefore at a very low current.

If, after initiation of the ionization, the means creating this condition still has residual energy, this will be absorbed by the first charges moving in the plasma (hatched area of FIG. 4).

The ionization being initiated then called to maintain itself, the initial condition sought here can disappear without inconvenience. It is enough to recreate it at the start of the next alternation, a condition easily fulfilled since the low energy which this means must have, to create the operating conditions described above, is borrowed during the previous alternation of the proposed supply current. through the network. In other words, the low energy in question is borrowed from the alternation of rank (n-1) to be restored at the beginning (passage to 0 Volt) of the alternation of rank (n) in the form of a voltage of a pulse nature whose peak value V _m can clearly exceed that corresponding to the current of the network supplying the lamp and its equipment.

The previously described method is applicable by various means of different natures, the only action of which is to create, at the zero crossing of each half-wave, the overvoltage spike under low energy which is responsible for forcing the ionization in the discharge tube of the lamp.

We will now describe, with reference to FIG. 5, an example of a device for implementing this method.

The installation shown in Figure 5, which includes a discharge lamp 1, such as a mercury vapor lamp or other metal, is intended to be connected to the network by its terminals P (phase), N (neutral).

The stability of the operation of the lamp 1 is ensured by a device which comprises an autotransformer 2 wound in voltage booster, comprising a magnetic circuit 3 formed of a rectangular frame 4 and of a core 5 disposed substantially along the small median of the frame 4.

Around the core 5 are wound a primary winding 6 intended to be supplied through the switchgear of the lamp, from the terminals P, N, and a secondary winding 7 mounted in series with the lamp 1.

The autotransformer 2 includes means for ensuring magnetic leaks such that, on load, the voltage-raising function of the autotransformer 2 disappears almost completely.

These means reside in particular in the winding of the windings 6 and 7. While the primary winding 6 is wound tightly around the core 5 to make its magnetic leakage negligible, the secondary winding 7 is wound around the winding 6, substantially according to the same axis, and so that an annular space 8 of radial dimension D, remains between the windings 6 and 7 to allow magnetic leaks. In practice, a space 8 in which D = approximately 5 mm is sufficient in most cases.

On the other hand, the magnetic circuit 3 is free from shunt and air gap.

The primary winding 6 is supplied from the terminals P (phase) and N (neutral) for connection to the network, by means of a voltage variator 10 and a supply apparatus 9, 11.

The input terminals of the speed controller 10 are connected to the PN terminals, one of its output terminals is connected also at terminal N, while its other output terminal P 'is subjected to the adjustable potential.

The supply equipment comprises a capacitor 11 connecting the terminals P 'and N and an inductor 9 connected in series between the terminal P' and the primary winding 6. The other end of the winding 6 is connected directly to the terminal N.

The inductance 9 and the capacitor 11, which are components of current use for the standardized voltage capable of being applied to the terminals P, N, are generally associated from the outset with discharge lamps such as 1, one of the peculiarities of the invention being to allow their maintenance without modification.

Furthermore, the secondary winding 7 is connected directly to the lamp 1, the other terminal of which is itself directly connected to the terminal N.

• Tension d'arc 130 volts
• Tension d'amorçage 160 volts
• Section du fil de l'enroulement primaire : 0,1 mm2.
• Section du fil de l'enroulement secondaire : 0,5 à ₁ mm2.
• Impédance de l'enroulement primaire : 5000 à 6000 Ω.
• Dimension radiale D de l'espace de fuite : 5 mm.

In the case of a 250 W mercury vapor lamp, the following numerical values may be used, for example:

• Arc voltage 130 volts
• 160 volt ignition voltage
• Wire section of primary winding: 0.1 mm2.
• Section of the wire of the secondary winding: 0.5 to ₁ mm2.
• Primary winding impedance: 5000 to 6000 Ω.
• Radial dimension D of the leakage space: 5 mm.

Under these conditions, by adjusting the transformation ratio, an empty overvoltage of 40 effective volts can be reached.

• Quand la lampe 1 est éteinte, alors que les bornes PN sont sous tension, l'autotransformateur 2 fonctionne à vide et fournit une surtension A V entre ses bornes A et B.

The operation of the installation described above is as follows:

• When the lamp 1 is off, while the PN terminals are energized, the autotransformer 2 operates at no load and provides an AV overvoltage between its terminals A and B.

On the other hand, under load, as a result of magnetic leaks, the induced voltage of the secondary winding 7 is then very low.

Thus, the autotransformer 2 supplies the lamp with an AV no-load overvoltage, promoting its re-ignition and consequently its operating stability, and has practically no effect on its operation under load (lamp on), which results in a dissipated power. by the tiny autotransformer.

To decrease the power of the lamp 1, it suffices to adjust the dimmer 10 so as to reduce the voltage between the terminals P 'and N of the latter. Despite this Decreases Translation _n ution, the autotransformer 2 continues to supply a voltage capable of forcing the ignition of the lamp 1, provided that the threshold voltage ionization V _i does not exceed the maximum voltage V _m (Figure 4) that the autotransformer 2 can provide.

The location of the autotransformer 2 downstream of the inductor 9, on the side of the lamp 1, as shown in FIG. 5, is not an obligation.

In the case of switchgear comprising a starter in line with the inductor such as 9, it is advantageous not to disturb the high voltage HF emissions, to have the autotransformer 2 between this inductor and the capacitor 11.

The example of installation shown in FIG. 6 finds its application in public lighting in particular, where it is advantageous to provide two powers from which one chooses according to the time, depending on whether natural lighting is still sensitive or no, or that the frequentation of the place to be lit is important or not.

In this example, the installation is similar to that of FIG. 5, except that it further comprises, between the inductor 9 and the end of the primary winding 6 to which it is connected, a second inductor 39 mounted in parallel with a device 31 making it possible to short-circuit, or on the contrary to put this inductance 39 into service at will. On the other hand, the variator 10 has been eliminated.

The device 31 can be controlled manually, remotely or not, or else automatically by means, for example, of a photosensitive element.

To obtain a high lighting power, the inductor 39 is short-circuited using the device 31, so that only the inductor 9 is in circuit. To switch to a reduced lighting power, the inductor 39 is put into service.

Although the re-ignition voltage, or "no-load" voltage, remains equal to the supply voltage at the terminals P, N during the instantaneous series connection of the additive inductance 39, the lamp shows, for a relatively long time , a significant arc overvoltage which could cause its extinction in the absence of the autotransformer 2 or of another device implementing the method according to the invention.

In the installation example shown in FIG. 7, a capacitor 41 is connected between the terminals E and F of the discharge lamp 1, which are also the output terminals of the autotransformer 2, which is identical to that of the Figures 5 and 6. Furthermore, the installation of Figure 7 is identical to that of Figure 5, except that the drive 10 is deleted.

The capacitor 41 is not intended to produce the phenomenon of resonance by association with the inductances of the windings 6 and 7. Its role consists simply in storing a slight amount of energy during the alternation of rank (n-1) which, by restitution during the passage to zero beginning the alternation of rank (n), reinforces the desired overvoltage. This complement energy is then dissipated in the incipient discharge and thus contributes, by requesting with acceleration a greater number primary electrons, to better ensure its final establishment.

This feature is easily observed by means of an oscilloscope (connected to terminals E and F of the discharge tube) and corresponds to the hatched area presented in Figure 4.

• . impédance de l'enroulement primaire : 3000 ohms
• . rapport de transformation entre enroulements primaire (P) et secondaire (S), soit S/P = 0,1
• . capacité du condensateur : 0,5 microfarad
• . perte d'énergie, en charge dans le secondaire environ 4 volts-ampères.

The physical quantities chosen for the experimentation of the previous application and thanks to which the results presented in the table on page 18 were obtained are:

• . primary winding impedance: 3000 ohms
• . transformation ratio between primary (P) and secondary (S) windings, i.e. S / P = 0.1
• . capacitor capacity: 0.5 microfarad
• . loss of energy, in charge in the secondary approximately 4 volts-amperes.

These quantities are not critical. Comparable and similar results can be obtained with variations of these values of the order of 20 percent.

It is obvious that means different from that, very simple, just described, can be used for the same purpose.

The application of the method in the form previously described and according to the example of application (with capacitor) shows interesting results expressed by the table on page 18, below.

• . comparaison du comportement de la même lampe à décharge équipée de son même appareillage ballast, selon que le procédé est appliqué ou non ;
• . comparaison, dans les mêmes conditions, du comportement de deux lampes à décharge de même type dont :
  • - l'une est neuve mais préalablement vieillie pendant 200 heures de fonctionnement aux conditions nominales
  • - l'autre, totalement épuisée et ne s'allumant plus, même sous une tension d'alimentation portée à 240 Volts efficaces, provient d'une dépose pour remplacement.

This table allows a double comparison:

• . comparison of the behavior of the same discharge lamp equipped with its same ballast equipment, depending on whether the process is applied or not;
• . comparison, under the same conditions, of the behavior of two discharge lamps of the same type including:
  • - one is new but previously aged for 200 hours of operation at nominal conditions
  • - the other, completely exhausted and no longer lighting up, even under a supply voltage raised to 240 Volts effective, comes from a removal for replacement.

• . pour la lampe neuve : des tensions efficaces d'alimentation, correspondant à l'allumage et à l'extinction, nettement plus basses et une consommation, au seuil d'extinction, également très diminuée ;
• . pour la lampe usée : la possibilité de l'allumer même pour une tension efficace d'alimentation inférieure de plus de 25 pour cent à la tension nominale d'alimentation (220 Volts efficaces), ainsi qu'un seuil d'extinction identique à celui de la lampe neuve et une consommation correspondante également très diminuée. Il est à remarquer que le flux lumineux produit par cette lampe présente, dans ces conditions, une intensité très suffisante pour être exploitable.

It is easily observed, in the case of the application of the process:

• . for the new lamp: effective supply voltages, corresponding to switching on and off, significantly lower and consumption, at the switch-off threshold, also greatly reduced;
• . for the used lamp: the possibility of switching it on even for an effective supply voltage more than 25 percent lower than the nominal supply voltage (220 Volts rms), as well as an extinction threshold identical to that of the new lamp and corresponding consumption also greatly reduced. It should be noted that the light flux produced by this lamp has, under these conditions, a very sufficient intensity to be usable.

These results are preserved regardless of the number of samples of new or used lamps that are subjected to this experiment, the set of these values may vary somewhat (10 percent maximum) depending on the specific characteristics (dispersions in manufacturing) or the state of wear of the lamps.

• . il est possible, quand cela est désiré et faisable, de réduire considérablement la puissance consommée par les lampes en diminuant la tension du réseau qui les alimente (par des moyens connus et disponibles sur le marché) jusqu'à une valeur pratique de - 40 pour cent. Cette faculté se maintient tant pour les lampes neuves que pour celles ayant atteint ce qui, en conditions normales donc sans application du procédé, peut être considéré comme la limite d'usure ;
• . la durée de vie des lampes est prolongée de façon sensible par le fait que les lampes totalement usées continuent de fonctionner si le procédé leur est appliqué et, ceci, en manifestant de convenables performances de flux lumineux.

These results clearly show two major advantages offered by the application of the present process:

• . it is possible, when this is desired and feasible, to considerably reduce the power consumed by the lamps by reducing the voltage of the network which supplies them (by means known and available on the market) up to a practical value of - 40 for hundred. This ability is maintained both for new lamps and for those which have reached what, under normal conditions therefore without application of the process, can be considered as the wear limit;
• . the service life of the lamps is significantly extended by the fact that the totally worn lamps continue to function if the process is applied to them, and this, by demonstrating suitable performances of luminous flux.

This advantage is, moreover, reinforced by a consequence of the previous one because, the lifetime of these lamps being a function of the total energy (kilowatt-hours) they consume, the fact of being able, in part at least , operating them at reduced power also contributes to extending their service life.

Claims (11)

1. Method for promoting the ionization of discharge lamps, characterized in that at the appearance of each alternation, a difference in excitation potential is applied to the electrodes of the discharge lamp (1) which increases more rapidly and tends towards a maximum value (V _m ) higher than the operating potential difference (V) normally produced by the supply voltage, in order to reach the ionization potential difference (V _i ) of the lamp ( 1) even when the supply voltage (V) is significantly lower than the nominal supply voltage or when the discharge lamp (1) is in an advanced state of wear, and in that the return to the initial supply conditions when current begins to build up in the discharge lamp (1). 2. Method according to claim 1, characterized in that a difference in excitation potential is applied to the electrodes of the discharge lamp (1) capable of reaching the difference in ionization potential ( _V. ) of this lamp (1) when the supply voltage is at least 40% lower than the nominal supply voltage. 3. Method according to one of claims 1 or 2, characterized in that, to trigger the ionization, means are used having a tiny energy, so that, from the initiation initiated, the discharge lamp (1) operates under the conditions corresponding to the supply voltage used, therefore without overconsumption. 4. Method according to one of claims 1 to 3, characterized in that at each alternation, the priming charge necessary for the next alternation is taken. 5. Device for promoting the ionization of discharge lamps, by applying the method according to one of claims 1 to 4, comprising an autotransformer (2) wound in voltage booster, and of which the primary winding (6) is intended to be supplied from a voltage source, and the secondary winding (7) is intended to be mounted in series with the discharge lamp (1) to be stabilized, characterized in that that this autotransformer (2) comprises means (8) for practically neutralizing, under load, the voltage-raising function of the autotransformer (2), these means generating magnetic leaks manifested during the charging of the autotransformer (2 ). 6. Device according to claim 5, wherein the autotransformer comprises a core (5) around which the windings are wound (6, 7), characterized in that the aforementioned means comprise a primary winding (6) wound tightly around core, while the secondary winding (7) is wound around the primary winding and at a distance from the latter, so as to provide an annular space (8) sufficient for leaks between the two windings (6, 7). 7. Device according to claim 6, characterized in that it comprises a capacitor (41) connected to the output terminals of the autotransformer (2) and intended to store and then restore a low electric charge called to reinforce the initiation of the ionization phenomenon. 8. Device according to one of claims 5 to 7, characterized in that the autotransformer comprises a magnetic circuit free of shunt and air gap. 9. Lighting installation which comprises at least one discharge lamp (1), a supply apparatus (9, 11), and a device (2, 41) according to one of claims 5 to 8, characterized in that the apparatus (9, 11) is of the usual type suitable for the supply voltage, and in that the device (2, 41) for promoting the ionization of the lamp (1) is mounted between the apparatus supply (9, 11) and the lamp (1). 10. Lighting installation according to claim 9, characterized in that one end of the enrou- _e ment primary (6) is connected to a power supply terminal (P, _P ') via an inductor (39) connected in parallel with a device (31) enabling it to be put into service and short-circuited. 11. Lighting installation according to one of claims 9 or 10, characterized in that it comprises a voltage variator (10) mounted between the terminals (P, N) for connection to the network and the apparatus of power supply (9, 11).

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