Luminescent gas-discharge lamp under high pressure

These lamps have an internal pressure about the bar to ten bar. It results from it that the ionized gas responsible for the light output is much more brilliant and hot. The plasma generated between the electrodes is similar to the flash of a Orage. Thus, of stronger powers can be dissipated in a space of a few centimetres. The first lamps of this type were created at the beginning of the 20th century and gather mainly:

the mercury discharge lamps;
lamps with metal halides;
the lamps sodium vapor high pressure.

==Les lamps with vapor of mercure==

History

The first lamp using of the mercury under high pressure for the light output was invented by Way, in Great Britain in 1860. It was about a Arc to carbon functioning in an atmosphere of air and mercury. It was necessary to await 1906 to see the development by Küch and Retschinsky, of a lamp in quartz which will find an application mainly in medicine and physics, although a version adapted for industrial lighting will be born in 1909 (lamp “silica” of Westinghouse).

It is only in 1932 that the era of the mercury discharge lamps under high pressure will start. This year, the General Electric Company will be the first to propose a completely sealed lamp with dry steam, of 400 Watts, intended to replace the sources with incandescence of 1000 Watt, very much used for the lighting of the streets and industries. The success of these lamps will be fulgurating and, as of 1935, all the major producers of lamps (Siemens, GE, Osram, Philips, etc) will propose them with the sale. These first lamps had a steam pressure of mercury limited to an atmosphere owing to the fact that glass Aluminosilicate was used for the construction of the tubes to arc. It is only of 1933 with 1935 that C. Bowl, of Philips, and D. Gabor of Siemens will invent sealings Tungstène - quartz which will allow the use of lamps steam pressure up to 80 bars. In practice this one will not exceed the 15 bars in the lamps with use general.

These quartz lamps since underwent many changes which made it possible to increase their lifespan up to 28.000 hours, although in practice this duration is often exceeded. Among the notable changes, the use of a fluorescent powder is reproduced on the internal surface of the envelope, transforming the radiation UV emitted by the arc with mercury into red light. The latter fills a vacuum in the spectrum of mercury, made up mainly of seven blue, green and orange lines, giving to the skin a cadaveric aspect. In spite of this modification, weak IRC (Ra50) of these lamps hold them mainly for utility applications where the quality of the light is not a big factor. The IRC can nevertheless be improved by the use of a layer of fluorescent powder thicker, of different nature or with a brown-gilded filter, but that results in a notable fall of the output of the lamp.

===Technologie===

The lamp

The mercury discharge lamps high pressure are made up of a tube with discharge out of quartz, enclosed in a bulb filled with nitrogen. The tube with discharge is equipped with two tungsten electrodes at each end, as well as one or two small electrodes of starting connected to the principal electrodes via resistances. This tube is filled of argon under low pressure, and a mercury drop which will be completely vaporized in normal circumstances operation. The mixture Argon - mercury and the use of electrode S auxiliaries allows the starting of these lamps the tension of the sector in Europe. In other country, like the the United States or the Japan, the tension sector is not sufficiently high.

The tube with discharge is localized in a second bulb, broader, in order to avoid the oxidation of the supplies of current in Molybdène. Moreover, the external bulb protects the tube with arc from any external contact and blocks radiations UV Cancérogène S emitted by the discharge. All the current lamps have a fluorescent coating of Phosphovanadate of yttrium recovering the internal surface of the external bulb. This coating is excited by emissions UV of the arc to mercury, and radiates a red light which, combined with the spectrum of mercury, gives a white light of cold color.

Certain lamps (known as with mixed light) have also a filament of Tungstène series-connected with the tube to discharge. This filament controls the current of the lamp, with the result that no other regulating circuit is necessary. Moreover, the red light emitted by incandescence improves the general color of these lamps.

Power supplies

In Europe and in the other countries or the tension sector is higher than 200 V, these lamps are connected in series with a self inductance which controls the current of discharge. The Dephasing armature between the current and the tension of lamp is compensated by a Condensateur, chosen so that the power-factor is at least equal to 0,80.

In the countries or the tension sector is only about 100-120 V, one has recourse to auto-transformers with dispersion of flows which control the current of lamp and allow him to start correctly.

Product range

The currently available sources have a power spreading out of 40/50 Watts up to 1000 Watts, with models of 2000 Watts still available to Japan but in the process of disappearance. To date there exist four types of lamps for industrial and public lighting:

standard standard The fluorescent coating is yttrium phosphovanadate, giving to the lamp a temperature of color of 3550 K to 4200 K, with a moderated IRC with Ra50 which limits the use of these lamps to industries and public highways.

50 W 1800 lm 36 lm/W 4200 K 100 V 0,6 has
80 W 3800 lm 48 lm/W 4100 K 115 V 0,8 has
125 W 6300 lm 50 lm/W 4000 K 125 V 1,15 has
250 W 13000 lm 52 lm/W 3900 K 130 V 2,15 has
400 W 22000 lm 55 lm/W 3800 K 135 V 3,25 has
700 W 40000 lm 57lm/W 3550 K 140 V 5,4 has
1000 W 58000 lm 58 lm/W 3550 K 145 V 7,5 has

standard of luxury A larger thickness of fluorescent powder confers on these lamps a hotter color, located in first half of 3000 K. These sources are appropriate more for lighting of zones for strong population density, well their IRC of Ra57 does not allow a regular commercial practice.

50 W 2000 lm 40 lm/W 3300 K 100 V 0,6 has
80 W 4000 lm 50 lm/W 3200 K 115 V 0,8 has
125 W 6500 lm 52 lm/W 3200 K 125 V 1,15 has
250 W 14000 lm 56 lm/W 3100 K 130 V 2,15 has
400 W 24000 lm 60 lm/W 3000 K 135 V 3,25 has

standard super of luxury A brown filter gilded is used in order to decrease the importance of the light blue and green in the radiation of these lamps, which gives a color of hottest. However, the IRC remains modestly in Ra60 and the apparent brightness leaves strongly decreased but remains from there close to twice higher than that to an incandescent lamp.

50 W 1600 lm 32 lm/W 3000 K 100 V 0,6 has
80 W 3400 lm 43 lm/W 3000 K 115 V 0,8 has
125 W 5700 lm 46 lm/W 3000 K 125 V 1,15 has

standard with mixed light In these lamps, an incandescent filament is connected in series with the tube to arc. This filament plays the part of ballast, with the result that the lamp can be connected on the sector without equipment. Moreover, the light of the arc to mercury and filament give to the lamp a tepid color of suitable quality with an IRC of Ra68, it at the price of a relatively bad apparent brightness. These lamps are appropriate for the replacement of incandescent lamps in industrial facilities.

160 W 3100 lm 20 lm/W 3600 K 235 V 0,8 has
250 W 5600 lm 23 lm/W 3800 K 235 V 1,2 has
500 W 14000 lm 28 lm/W 4100 K 235 V 2,3 has

In addition to this range, there exist models of special use. Four types of lamps are distinguished:

standard with black light These lamps are equipped with an envelope out of glass of Wood (containing a strong concentration of oxide nickel and iron) who absorbs the visible radiation and transmits to the cluster lines UVA of mercury to 365 Nm.

standard solar radiation These lamps have an external bulb out of hard glass which transmits the GRAPE radiation and UV-B as well as the visible light. These lamps are used for the study of the artificial ageing of materials and the reproduction of documents. standard UV courts Composed of a quartz envelope, these sources are used for the disinfection of water and the hardening of adhesives and inks.

standard spectral They are lamps of laboratories, radiant in UV or not, used for the experiments of fluorescence and the spectroscopy.

Remarks

If these lamps were very popular in the Années 1950 - 60, they now make place with the sources with sodium vapor high pressure and with the metal halides whose outputs are much better and the color of the more pleasant emitted light. However, the ease of use of the lamps to mercury like their low costs and their durability make that they will be employed still a long time in the installations of public lighting and industrialist.

Lamps with metal halides

History

The mercury discharge lamp never really was essential apart from industrial and road lighting, because the emitted light remains poor in term of quality, even with the use of fluorescent powders. Various solutions were studied in order to improve these lamps. As of 1912, C. Steinmetz proposes the addition of Cadmium and Zinc in the arcs with mercury in order to provide a richer spectrum, in particular in the red, but resulted invariably in a considerable reduction in the apparent brightness.

It is only at the end of the Fifties that independent studies show that the metal salt addition makes it possible either to increase the apparent brightness, or to improve quality of the emitted light, but not both. In 1961, General Electric presents the first lamp to the metal halides commercial, which is, in fact, a mercury discharge lamp with Iodure of sodium, whose orange red radiation supplements the spectrum of mercury. This new lamp was not entirely satisfactory because, if returned colors were better, the emitted light had a rather pink color. It is only starting from 1965 that one succeeds in obtaining a good color of light while even doubling tripling the apparent brightness.

Since the Années 1970 there were relatively few improvements of this technology. The major exceptions are the introduction of the compact lamps in 1981, sources used for the commercial lighting (shops, windows etc), and employment, in 1994, of tubes with arc (burner) in Alumine sintered, allowing a profit of 30-50 % on the apparent brightness with the best returned colors. An alternative of this technology also appeared in 1991 : the headlights with the Xénon which equip the motor vehicles henceforth top-of-the-range and will replace certainly in the long term the lamps halogen for the lighting of power of the vehicles.

Today, the sources with metal halides provide the best compromise between the quality of light and the apparent brightness. However, the price of these lamps is higher than the sources with mercury, and require also a more complex equipment. Moreover, metal salts corrode the material of the tube with arc, with the result that the lifespan is shorter. In spite of these disadvantages, these lamps very largely were essential in the commercial lighting and sportsman where a great quality of light is necessary, while guaranteeing substantial energy saving vis-a-vis the incandescent lamps. The constant improvement and miniaturization of the lamps to ceramic burner and of their electronic food, make that these lamps will be essential even more, and this in fields up to that point reserved for the compact halogenous lamps.

Technology

Lamps

The majority of the lamps with metal halides have a construction similar to that of the mercury discharge lamps high pressure. A tube with discharge out of quartz, provided with two tungsten electrodes, is locked up in an external bulb. In addition to argon and mercury, the tube with discharge is proportioned with various metal salts, whose composition and quantity depend on the type of light and the performances desired. The electrode spacing is shorter than for the mercury discharge lamps in order to allow a greater dissipation of power per centimetre of arc. The ends of the tube with discharge are also covered with a white deposit of Oxyde of zirconium or aluminum in order to increase the temperature of the coldest point. All these measurements make it possible to obtain a steam pressure of metal salts as high as possible in order to maximize the light output.

Another technology of tube with discharge polycrystalline use of alumina sintered instead of quartz. This material change allows a greater operating temperature and a profit from 20 to 30% on the apparent brightness. The geometry of these tubes as well is controlled better than that of the quartz tubes, it results from it that the dispersion of the temperature of color in a group of lamps is considerably reduced.

The presence of metal salts in these lamps has as a consequence gas mercury the progressive halide pronation in the tube with discharge. This gas being electronegative, the tension of starting tends to grow with time. So in Europe and in the majority of the other countries one use of the high voltage to start these lamps, those of North America are equipped with electrodes auxiliary, similar to those of the lamps to mercury, and are started with weaker tensions.

Power supplies

The lamps with metal halides of the countries whose tension sector is higher than 200 V are supplied by a self inductance series-connected with the lamp. An electronic igniter is connected in series or parallel and generates impulses of 3-4 Kv in order to make start the lamp. The countries whose tension sector is about 100-120 V use auto-transformers with dispersion of flow, whose no-load voltage is about 350 V. This voltage is sufficiently high to allow the lamps provided with auxiliary electrodes to start correctly.

The electronic use of ballasts becomes now increasingly current, and is almost systematic in the luminaries of the stores and shopping malls. The use of electronics makes it possible to improve the performances of the lamps, and offers options like the variation of the luminous intensity or the automatic control of end-of-life of the lamp.

Product range

There exists a whole range of lamps to the metal halides whose filling corresponds to a particular light and thus a specific use. The temperature of color spreads out of 2700 K (white heat) up to 6500 K (light of day) and more for special uses. In term of power, the range extends from 10 Watts, for torch of deep-sea diving, up to 3500 Watts for the lighting of stages and big spaces.

Remarks

The lamps with metal halides present the future of the gas-discharge lamps high pressure, because their evolution in term of performance does not cease increasing; each month there are a new lamp of this type, or an improvement which is introduced, whereas in other technologies the evolution reached a plate. If no major innovation occurs in the field of mercury and the sodium vapor lamps, then the sources with metal halides will be essential without division in the urban lighting of center town, and perhaps even in domestic lighting.

The lamps sodium vapor

The interest of the use of sodium is known since the years 1930, when the first lamps functioning with this vapor under low pressure were born. If these lamps have the best possible output well today, their very bad returned rather broad colors and their dimensions limits their applications to the lighting of public highways. So it was very early planned to increase the steam pressure in order to dissipate more power per unit of length, and to enrich the spectrum emitted in order to make the light more pleasant to the eye.

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