Low pressure mercury arc lamps. High pressure gas discharge lamps. High and ultra-high pressure mercury lamps

DRL lamps are high-pressure fluorescent mercury discharge lamps with corrected color rendering. Don't be fooled by the definition. The color rendition of DRL lamps is not very good.

Story

Historically, low-pressure lamps were the first to appear, where the discharge occurred in sodium vapor. What is meant is not the process of invention, but the industrial development of lighting devices. Generally speaking, the commercial sense of using discharge lamps for lighting was brought into industry by Peter Cooper Hewitt. And this happened in 1901. The lamps, filled with mercury, seemed so successful to the creator that in the new year the researcher organized a company with the support of George Westinghouse. The enterprises of the latter were engaged in production.

The move seems logical for the simple reason that George Westinghouse, along with Tesla, led the fight for the introduction of alternating current. And he rejoiced at every useful invention, the operation of which required the mentioned type of electricity. The sodium lamp appeared in 1919, thanks to the efforts of Arthur Compton. A year later, borosilicate glass was added to the design. Characterized by a low coefficient of thermal expansion, it has excellent resistance to aggressive environment sodium vapor. The practical use of lamps on city streets dates back to the early 30s (in the Netherlands - from July 1, 1932).

Power luminous flux sodium lamps was 50 lm/W, which was considered a decent indicator. Despite the specific yellow-orange color of the radiation. In the USSR, the development of low-pressure sodium lamps did not proceed. Mercury ones were considered more acceptable. In addition, high-pressure sodium lamps appeared. The described models are characterized by incorrect color rendering. What was said concerned living objects and humans. The disadvantage was partially overcome in 1938 by introducing low-pressure mercury lamps into industrial production. Key Features:

1. Luminous efficiency – 85 – 104 lm/W.
2. Service life – up to 60 thousand hours.
3. Perspective emission spectrum.

DRL lamps appeared in the early 50s. Their performance characteristics do not reach those given above (output 45 - 65 lm/W, service life 10 - 20 thousand hours), but are acceptable. DRL lamps are used for outdoor and indoor lighting. Next step in the development of RLVI (high intensity) discharge lamps. The key difference was increased efficiency. In the first samples the indicator was already 100 lm/W. High pressure sodium lamps are superior in performance to DRL models.

Features of the discharge lamp with corrected color rendition

Bulb brightness

It was said above that some discharge (and fluorescent) lamps are characterized by low color rendering. The world around us becomes slightly distorted, which quickly tires the psyche. An additional factor is the physiological sensitivity of the eyes. It is not the same visible spectrum, some people are able to see an aura. But for most individuals, the maximum susceptibility occurs at a wavelength of 555 nm ( green color). And towards the edges, the sensitivity of the eyes decreases.

Therefore, researchers call for adjusting the lamp power to the physiological characteristics of a person. As a result, 1 W at 555 nm is equivalent to 10 at 700 nm. Infrared radiation is not perceived by humans. Brightness is assessed based on luminous flux, taking into account the effect of each wavelength. The unit of measurement became the lumen, equivalent to a power of 1/683 W for a wavelength of 555 nm. And luminous efficiency (lm/W) shows what fraction of the power in the light bulb becomes optical radiation. The maximum value reaches 683 lm/W and is observed exclusively at a wavelength of 555 nm.

We cannot ignore the unit of illumination - lux. Numerically equal to 1 lm/sq.m. Knowing the luminous flux, the installation height of the lamp, its opening angle, it is possible to calculate the illumination. The parameter for premises is standardized according to GOST. In light of the above, it is clear why DRL lamps with corrected color rendition are still found on the market, despite their relatively unenviable characteristics.

A locus is used to evaluate color rendering. This is a figure resembling an inverted parabola, slightly tilted to the left side. In it, color shows two coordinates from 0 to 1. For a lamp to exhibit good color rendering, the position of its integral radiation tends to the center of the locus. Let's add that increasing the color temperature will mix the spectrum from red to violet:

• 2880 – 3200 K – warm yellow;
• 3500 K – neutral white;
• 4100 K – cool white;
• 5500 – 7000 K – daylight.

In this regard, yellow-orange low-pressure sodium lamps are considered bad choice. They cause a chemical imbalance in the retina of the eye that causes fatigue. However, remember that the decisive role is still played by the spectrum, not the color temperature: any light bulb is inferior to the Sun. Therefore, in the poor spectrum of a low-pressure sodium lamp (two spectra in the yellow region), objects appear black, gray or yellow. This is called incorrect color rendering.

It is customary to characterize a parameter with an index based on a visual comparison of samples illuminated by a light bulb with a standard. The value falls within the range from 1 (worst case) to 100 (ideal). In practice, the maximum you can find is a lamp in the range of 95 - 98. This will help you choose a DRL lamp on the counter (typical value 40 - 70).

Color correction

A discharge glows in an ionized gas environment. The whole operating principle. The rest comes down to the conditions for obtaining an arc between the electrodes. Ionization conditions require the presence high voltage, which will no longer be needed in the future. Often discharge lamps require a ballast. The atmosphere is filled with an inert gas and a small amount of elastic metal vapors (mercury, sodium, and their halides). In practice, lamps mainly use the following types of discharges:

1. Glowing - with a low current density at low gas or steam pressure. The voltage drop across the cathode reaches 400 V. Dark spots in the cathode area are visually visible.
2. Arc – with high current density at different pressures. The voltage drop across the cathode is relatively small (up to 15 V). The low pressure arc column is like a smoldering one.
3. High intensity arcs are a specific phenomenon used in floodlights. For example, they were used to identify enemy air targets during the Second World War. It is based on a special mode of operation of the coal rod, discovered in 1910 by G. Beck.

The spectrum of a mercury discharge lies in the ultraviolet region by 40%. The phosphor converts this area into a red glow, while allowing most of the violet and blue to pass through freely. The quality of spectrum correction is determined by the red ratio (increases with increasing layer thickness, as does the price, required parameters determined experimentally due to the complexity of the calculation). The mercury burner is made of quartz glass (does not emit gaseous substances during operation), and the outer flask, coated on the inside with a phosphor, is made of ordinary, but refractory. Edison base. Europium-activated yttrium vanadate phosphate is used as a phosphor. The material detects a glow spectrum of four red bands: 535, 590, 618 (max), 650 nm. The optimal operating mode is achieved at a temperature of 250 to 300 degrees (release time is about a quarter of an hour).

Before application, the phosphor is ground and calcined. Yttrium vanadate phosphate was chosen for a reason; it withstands processing very well. The considerable cost is often offset by joint use with other materials. For example, strontium-zinc orthophosphate. They better absorb the wavelength of 365 nm, and it is possible to achieve acceptable characteristics (taking into account the specific application in the field of industrial lighting at an installation height of 3 to 5 meters).

There are known cases of using magnesium fluorogermanate activated by tetravalent manganese. Luminous efficiency and red ratio (6-8%) are slightly reduced. The optimal temperature regime is set around 300 degrees Celsius. With further heating, the effectiveness of the device decreases. In all respects, except price, the material is inferior to yttrium vanadate phosphate: it absorbs part of the violet-blue region of the spectrum, detects a luminescence spectrum in the far red region (where the eye shows low sensitivity), and loses brightness during processing.

The design usually includes one or two ignition electrodes, the distance from which to the cathode is relatively small. So no external ballast is required. In combination with a standard base, you get a convenient replacement for incandescent light bulbs with increased efficiency. The flask becomes very hot during operation due to intense absorption of radiation by the phosphor. The geometric shape is calculated based on this parameter. On the one hand, it is required that the burner radiation falls on the phosphor, on the other hand, the temperature in operating mode should not exceed the optimal one (see above).

The flask is often filled with argon. It is cheap and introduces little heat loss. Add 10-15% nitrogen to increase the breakdown voltage. The total pressure is approximately equal to atmospheric pressure. The ingress of oxygen (destroys metal parts) or hydrogen (increases the arc ignition voltage) is unacceptable. Any burning position is allowed, but horizontal is not encouraged. The arc bends slightly, the quartz glass is in an unfavorable temperature regime. The temperature of the medium affects the breakdown voltage. In winter, it is more difficult to ignite an arc, the mercury settles, and the process takes place in an environment of almost pure argon (for this reason, starting devices sometimes have to be used).

DRL lamps have a relatively hot base. The temperature can exceed the boiling point of water. This must be taken into account when selecting a socket and a chandelier (lantern) for installing a lamp. It’s time to remember the advice of the authors of the patent for the first halogen lamps. The burner temperature is relatively low, but will easily melt aluminum.

Marking

In domestic practice, the number following the DRL means power consumption in W. Next comes the red ratio: the ratio of the red flux (from 600 to 780 nm) to the total - expressed as a percentage. The development number is indicated with a hyphen. The red ratio characterizes color rendering; values ​​above ten are considered good.

According to the international standard IEC 1231, the ILCOS system is used. These are competitors of the German LBS marking and the pan-European ZVEI. There is complete chaos in the market. According to ILCOS:

1. QE stands for ellipsoidal bulb shape.
2. QR denotes a bulb with an internal reflective layer, mushroom-shaped.
3. QG stands for spherical flask.
4. QB stands for products with built-in ballast.
5. QBR denotes products with built-in ballast and a reflective layer.

Philips has its own view of things, but General Electric doesn’t want to hear about either. Actually, it is better to rely on reference books or read the information on the packaging. Remember that the base comes in standard sizes and in other sizes. The share of DRL lamp production is continuously decreasing, so there is no point in studying complex designations in too much detail. And given the entry of LEDs into the market, it is better to find something modern and constantly evolving for your home and garden. As for efficiency, the dispute will clearly not be resolved in favor of discharge lamps, although for some time they successfully deposited the filament.

Mercury lamps type DRL

The quartz burner discussed in the article “Operation of a DRL lamp” is subject to strong influence external environment, on which the cooling conditions depend. The stability of the lamp with such a burner is ensured by placing it inside the outer bulb. The inner surface of the outer flask is covered with a layer of phosphor, which, due to the absorption of the ultraviolet part of the radiation of the mercury discharge, adds to the visible radiation of this discharge the radiation missing in the red region of the spectrum. To ensure cooling of the quartz burner not only by radiation, but also by convection and heat transfer, the outer flask is filled with gas, which must be inert with respect to the phosphor and lamp mounting parts. A mixture of argon and nitrogen is used as a filling gas.

The structure of the DRL lamp is shown in Figure 1. The lamps are connected to the network using threaded sockets similar to those used for incandescent lamps: E27 - for lamps with a power of up to 250 W and E40 - for lamps of higher power. To facilitate ignition, the lamp is made of three or four electrodes. In the latter, the main and auxiliary electrodes are connected through resistors.

The shape and dimensions of the outer flask and the position of the burner in it are chosen so that all the ultraviolet radiation of the burner falls on the phosphor layer and during operation and during operation of the lamp the phosphor layer has an optimal temperature for its operation.

Heating of the outer flask occurs due to the absorption of part of the discharge radiation by the layer of phosphor applied to it and glass, as well as heat transfer through the inert gas filling the flask. Cooling occurs due to radiation from the heated glass and heat transfer through the surrounding air.

Uniformity of the flask surface temperature can be achieved if, neglecting to a first approximation the convection of the inert gas filling the flask, it is designed in the form of a surface that ensures uniform irradiation. Calculations show that the central part of the flask should have a surface close to an ellipsoid of rotation, with a major axis coinciding with the axis of the burner. Correction for convection forces a slight increase in the diameter of that part of the bulb that is at the top when the lamp is operating. Since the lamps are practically used in any position, no corrections are made to the shape of the bulb.

In a number of lamp designs, the bulb plays the role of optical element, redistributing the light flux. In this case, the shape and size of the bulb must be calculated, as is done for lamps, and its thermal regime must also be taken into account in the calculation.

To correct the color of DRL type lamps, they use different kinds phosphors. The use of phosphate-vanadate-yttrium phosphor instead of magnesium fluorogermanate made it possible to improve the parameters of DRL type lamps.

The use of a phosphor applied to the inner wall of the outer flask, on the one hand, leads to the addition of missing red radiation in the spectrum, and on the other hand, causes the absorption of part of the visible radiation in this layer. As the thickness of the phosphor layer increases, the lamp radiation flux has a maximum at a certain layer thickness, while the discharge luminous flux passing through the phosphor layer gradually decreases. To resolve the issue of the optimal thickness of the phosphor layer and a general assessment of its effectiveness for characterizing DRL type lamps, the concept of “red ratio” was introduced. The red ratio is the percentage ratio of the red luminous flux added by the phosphor to the total luminous flux of the lamps, expressed as a percentage. Obviously, the best would be a phosphor and a layer of it that, when creating a red ratio sufficient to ensure correct color rendering, provide the maximum luminous flux of the lamp as a whole, that is, the greatest luminous efficiency.

The red ratio is usually expressed as a percentage by dependence

Where φ (λ) - spectral flux density of the lamp; V(λ) - relative sensitivity of the eye.

The red ratio for DRL type lamps with the optimal thickness of phosphor made of fluorogermanate and magnesium arsenate reaches 8%, and the luminous flux is 87% of the luminous flux of a lamp without phosphor. The use of zinc orthophosphate phosphors with the addition of strontium makes it possible to obtain a luminous flux that is 15% higher than the luminous flux of a lamp without a phosphor, and r kr = 4 - 5%.

During the ignition of lamps, cathode sputtering of the active substance of the cathode and the rod part of the electrode takes place. In steady combustion mode at alternating current Due to the re-ignition of the discharge in each half-cycle, sputtering of the rod part of the electrode continues. This worsens over time the emissive properties of both parts of the electrodes, and the voltage required to ignite the lamps increases accordingly. Sputtering of the electrodes simultaneously leads to the absorption of molecules of the inert gas filling the lamp, the initial pressure of which was selected from the conditions for ignition of the discharge. These processes lead to the formation of a dark coating on the walls of the burner from particles of sprayed electrodes, which absorbs radiation, especially its ultraviolet component, and the red ratio decreases. Stopping ignition determines the full service life of DRL type lamps, and the normalized decrease in luminous efficiency determines their useful service life.

Figure 2. High-pressure mercury lamp burner design details: 1 - main electrode; 2 - molybdenum foil inputs of the main electrode and ignition electrode; 3 - additional resistor in the ignition electrode circuit; 4 - ignition electrode circuit

The symbol for DRL lamps is deciphered as follows: D - arc, R - mercury, L - fluorescent. The numbers after the letters correspond to the power of the lamp in watts, then in parentheses the red ratio is given as a percentage and separated by a hyphen - the development number. The vast majority of DRL type lamps are produced with four electrodes, that is, with additional electrodes to facilitate ignition (see Figure 2). Such lamps are lit directly from the mains voltage. Small part DRL lamps are made with two electrodes; special ignition devices are used to ignite them.

DRL lamps are used in outdoor lighting installations and for lighting high rooms of industrial enterprises, where there are no strict requirements for the quality of color rendering.

Effect of temperature environment affects primarily the ignition voltage of the lamps. At negative temperatures, ignition of DRL type lamps is difficult, which is associated with a significant decrease in mercury pressure, as a result of which ignition occurs in pure argon and requires higher voltages than in the presence of mercury vapor. According to GOST 16354-77, DRL type lamps of all powers must be ignited at a voltage of no more than 180 V at an ambient temperature of 20 - 40 ° C; at a temperature of -25 °C, the ignition voltage of lamps increases to 205 V, at -40 °C, the ignition voltage for lamps with a power of 80 - 400 W is no more than 250 V, with a power of 700 and 1000 W - 300 V. For the light and electrical parameters of DRL type lamps Changes in external temperature have virtually no effect. Table 1 shows the parameters of DRL type lamps. The lamps have two modifications with a red ratio of 6 and 10%.

Table 1

Main parameters of DRL type lamps according to GOST 16357-79

Mercury-tungsten lamps

The difficulty of igniting DRL lamps at subzero temperatures, the use of inductive ballasts, as well as the need to correct the color of the radiation, led to the creation of high-pressure lamps with ballast in the form of an incandescent lamp filament. Note that the large power losses in the active ballast, which is an incandescent filament, compared to losses in the inductive ballast, are compensated by the simplicity of the active ballast with the possibility of simultaneously obtaining the missing red radiation with its help.

By placing a ballast filament in an external flask in which a quartz burner is placed to reduce the dependence of its parameters on the external temperature, it was possible to obtain a lamp suitable for direct connection to the network. The design of such a lamp is shown in Figure 3. Placing the filament inside the lamp bulb creates the additional advantage of reducing the burn-up period due to the heating of the burner by the radiation of the coil.

The main thing when calculating mixed light lamps, as mercury-tungsten lamps are sometimes called, is the choice of filament parameters. The filament power is selected based on the condition for stabilizing the mercury discharge. The luminous output of the filament has to be reduced in order to obtain a sufficiently red ratio, while at the same time ensuring a filament service life commensurate with the service life of quartz burners. During the start-up period, the network voltage falls entirely on the coil, but as the mercury lamp burns up, the voltage on it increases, and the voltage on the ballast coil decreases to the operating value. The luminous efficiency of mercury-tungsten lamps is 18 - 20 lm/W, since about 50% of the power is spent on heating the coil. Therefore, in terms of efficiency, these lamps cannot compete with DRL lamps and other high-pressure lamps. Their use is limited to specialized areas, such as radiation technology.

DRVE type lamps have an outer bulb made of special glass that transmits ultraviolet radiation. Such lamps are used for combined lighting and irradiation, for example in greenhouses. The service life of such lamps is 3 - 5 thousand hours, it is determined by the service life of the tungsten filament.

Tubular mercury lamps

In addition to lamps operating on the basis of a high-pressure discharge in mercury vapor and intended for lighting purposes, several types of radiation sources are manufactured, the development of which is associated with the need to use not only visible, but also ultraviolet radiation. As is known, ultraviolet radiation has chemical and biological effects. Actinicity of ultraviolet radiation, that is, the effect on photosensitive materials used in the printing industry, is widely used. Powerful streams bactericidal radiation, greater than that of bactericidal ones, allow the use of high-pressure mercury lamps for the purpose of disinfecting water and other substances. Chemical activity of ultraviolet radiation and ability to concentrate high power radiation on small surfaces has led to widespread use high-pressure mercury lamps in chemical, woodworking and other industries.

Lamps of this type require bulbs made of mechanically strong and refractory quartz glass. The quartz glass used, which transmits ultraviolet radiation starting from a wavelength of 220 nm, that is, almost the entire radiation spectrum of a mercury discharge, allows you to change the radiation parameters only by changing the operating pressure. The opacity of quartz glass for resonant radiation with a wavelength of 185 nm is of no practical importance, since ultraviolet radiation of this wavelength is almost completely absorbed by air.

This led to the creation of high-pressure mercury lamps, which differ in design depending on the operating pressure and area of ​​application. the main parameters of high-pressure lamps are given in table 2.

table 2

Main parameters of high-pressure mercury tube lamps according to GOST 20401-75

The industry produces mercury lamps of the DRT type (mercury arc tube) with a pressure of up to 2 × 10 5 Pa in the form of straight tubes with a diameter of 14 - 32 mm. Figure 4 shows a general view and dimensions DRT type lamps different power. Both ends of the tubes have extensions of smaller diameter, into which molybdenum foil is soldered, serving as inputs. WITH inside lamps, tungsten activated self-heating electrodes are welded to the inputs, the design of which is shown in Figure 5. For fastening the lamps in the fittings, the lamps are equipped with metal clamps with holders. The spout in the middle of the flask is the remnant of the plug, sealed off after vacuum treatment of the lamp. To facilitate ignition, the lamps have a special strip to which the ignition pulse is applied.

Figure 4. General form DRT type lamps (mercury vapor pressure up to 0.2 MPa) power, W:
A - 230; b - 400; V - 1000

Figure 5. Electrodes (cathodes) of high-pressure mercury lamps:
1 - active substance (oxide); 2 - tungsten core; 3 - spiral

Tubular xenon lamps

High-pressure tubular lamps also include lamps that use xenon radiation at pressures ranging from hundreds to millions of pascals. A characteristic feature of a discharge in inert gases at high pressures and high current densities is a continuous emission spectrum, which provides good color rendition of illuminated objects. In the visible region, the spectrum of a xenon discharge is close to that of the sun with a color temperature of 6100 - 6300 K. Important feature of such a category is its increasing volt-ampere characteristics at high densities current, which allows you to stabilize the discharge using small ballast resistances. Xenon tubular lamps of considerable length can be connected to the network without any additional ballast. The advantage of xenon lamps is the absence of a burn-up period. The parameters of xenon lamps are practically independent of ambient temperature down to temperatures of -50 °C, which allows them to be used in outdoor lighting installations in any climatic zone. However, xenon lamps have high voltage ignition and require the use of special ignition devices. The small potential gradient led to the use of more massive bushings in lamps.

The luminous efficiency of lamps increases with increasing specific power and diameter of the discharge tube. At high current densities, a discharge in inert gases has a very high brightness. According to theoretical estimates, the maximum brightness of a discharge in xenon can reach 2 × 10³ Mcd/m². The main parameters of high-pressure xenon lamps are shown in Table 3. Tubular xenon lamps operate with both natural and water cooling. The use of water cooling made it possible to increase the luminous efficiency of lamps from 20 - 29 to 35 - 45 lm/W, but somewhat complicated the design. The burner of water-cooled lamps is enclosed in a glass vessel, and distilled water circulates in the space between the burner and the outer cylinder vessel.

Table 3

Main parameters of high pressure xenon lamps

High tube temperatures (about 1000 K) require the use of quartz glass and appropriate molybdenum bushing designs designed to withstand high currents. The lamp electrodes are made of activated tungsten. One design of a water-cooled xenon lamp is shown in Figure 6.

Figure 6. General view of a 6 kW water-cooled tubular xenon lamp

The parameters of ballastless xenon lamps are strongly influenced by the mains voltage. When the mains voltage deviates by ±5% of the nominal value, the lamp power changes by approximately 20%.

The designation of the lamps consists of the letters D - arc, Ks xenon, T - tubular, V - water-cooled and numbers indicating the lamp power in watts and, separated by a hyphen, the development number.

High Pressure Discharge Lamps

This group of ICs includes high-pressure mercury lamps (HRL), metal halide lamps (DRI), sodium lamps (DNaT), xenon lamps (DKsT, DKsSh).

Electric discharge in mercury vapor is accompanied by electromagnetic radiation in the visible region of the spectrum and in the near ultraviolet region, not only at low vapor pressures (which is used in LL), but also at fairly high pressures - about 10 5 Pa. This discharge is used in high and high mercury arc lamps. ultra high pressure which are often called high intensity lamps.

High and ultra-high pressure mercury lamps for a long time were the most common and numerous group of IS among high and ultra-high pressure RL. This is due to the fact that with the help of a mercury discharge it is possible to create very effective sources in the ultraviolet, visible and near-visible infrared regions of the spectrum. These ICs have wide range rated power, burning duration is tens of thousands of hours, they are quite compact, and, if necessary, have very high brightness.

Based on the design features, high-pressure (RLVD) and ultra-high-pressure (RLSVD) mercury lamps are divided into the following groups:

– RLVD (DRT type);

– RLVD with corrected color (such as DRL and DRVE);

– tubular RLSVD with natural cooling;

– capillary radars with forced (air or water) cooling;

– spherical RLSVD with natural cooling.

Most types of RLVD and RLVD have a specific application and are not used for lighting purposes. Thus, RLVDs, being effective sources of ultraviolet radiation, are used in medicine, agriculture, measuring and photocopying equipment. The areas of application of RLSWD are beam oscilloscopes, photolithography, projection systems, luminescence analysis, i.e. those cases when sources are required high brightness in the visible and near ultraviolet regions of the spectrum.

A characteristic feature of a discharge in mercury vapor under high pressure is practically complete absence radiation in the red wave region of the spectrum. The discharge has a line spectrum and contains only 4 lines in the visible region. Therefore, the task arises of correcting the color of the discharge of a mercury lamp. This problem can be solved in one of the following ways:

– the use of phosphors - such lamps are called DRL (mercury arc fluorescent);

– adding emitting additives to the discharge tube - halides (metal halide lamps of the DRI type);

– a combination of a phosphor with a radiating additive (DRIL lamps);

– combining a mercury lamp with an incandescent lamp (DRVE lamp - arc mercury-tungsten erythema).

Mercury-tungsten lamps, in which, along with a mercury burner, there is a tungsten spiral, which simultaneously acts as an active ballast, are used in irradiation installations for erythemal (redness of the skin, which is replaced by pigmentation - tanning) lighting of people (for example, in solariums) and animals.

Arc mercury fluorescent lamps(DRL)

DRL lamps (Fig. 57) are a tube (burner) 7 made of transparent quartz glass, designed for an operating temperature of about 800 ° C and secured with a crossbeam 3 inside the outer ellipse-shaped flask 2 (this shape ensures uniform temperature distribution). After carefully removing foreign gases, a strictly dosed amount of mercury and argon are introduced into the tube at a pressure of 1.5...3 kPa. Argon serves to facilitate the discharge and protect the electrodes from sputtering in the initial stage of lamp flaring, since at room temperature the mercury vapor pressure is very low.

Two activated (coated with a layer of alkaline earth metal oxides) self-heating tungsten electrodes 4 are soldered at the ends of the burner and next to each of them there is one additional ignition electrode 5 2 mm long. Such lamps are called four-electrode lamps, in contrast to the previously produced two-electrode lamps, which did not have igniting electrodes. The presence of ignition electrodes ensures the ignition of unheated lamps at a voltage not lower than 90% of the nominal voltage, since the initial discharge occurs between the adjacent working and ignition electrodes. Voltage is supplied to the electrodes through the threaded base 1. After a discharge occurs in the lamp, the igniting electrodes do not affect its operation, because a current-limiting resistance 6 is included in their circuit.

The outer flask is coated on the inside with a phosphor and filled with a mixture of argon and nitrogen to prevent oxidation and remove heat from the burner. The phosphor converts ultraviolet radiation from a high-pressure mercury discharge, accounting for 40% of the total radiation flux, into the missing radiation in the red part of the spectrum. The quality of color rendition correction of DRL type lamps is determined by its “red ratio”, i.e. the share of the luminous flux in the red region of the spectrum (600...780 nm) in the total luminous flux of the lamp. In general, DRL lamps, even with the most great value“red ratio” are significantly inferior to LL in color rendering. The color rendering index of these lamps is one of the lowest - 40...45.

DRL lamps are connected to the network in series with a ballast choke (Fig. 58), the power loss in which is approximately 10% of the lamp power. Only when low temperatures environment (below –30 °C), it is necessary to use a pulsed ignition device (IZU), which ensures its ignition at temperatures up to –45 °C.

The ignition of DRL lamps is characterized by a burn-up period reaching five to seven minutes (Fig. 59). During this period, the main characteristics of the lamp undergo a change due to changes in the pressure of mercury vapor in the burner - for 80 W lamps the pressure increases to 10 6 Pa, for 1000 W lamps - to 2.5 10 5 Pa. In particular, the starting current of the lamp is twice the rated current.

Due to the fact that after the DRL lamp is turned off, the vapor pressure remains high, it can be re-ignited only after cooling down after 5...10 minutes. Therefore, DRL lamps are not used in emergency lighting networks.

If the supply voltage disappears for half a cycle or drops below 90% of the nominal voltage for two periods, the lamp will go out and light up again when it cools down.

The pulsation of the light flux of these lamps is very significant (pulsation coefficient is 63...74%).

Optimal position The lamp is vertical. In a horizontal position, the luminous flux decreases by 2...5%.

DRL lamps are produced with powers from 50 to 2000 W. Their luminous efficiency ranges from 40 to 60 lm/W.

The average burning time is up to 20,000 hours. By the end of its service life, the luminous flux is reduced to 60% of the nominal value (after 100 hours of combustion). When the supplied voltage changes from 90 to 110%, the burning duration changes from 140 to 70%, and the luminous flux changes from 65 to 130%.

It is important to emphasize that in Lately DRL lamps are being replaced by other RL lamps, as they are inferior to them in the most important characteristics.

IN symbol DRL type lamps indicate their power, red ratio (in parentheses) and development number, for example, DRL400(6)-4, where 6 is the proportion of rays in the red wave region of the spectrum.

Mercury arc lamps with emitting additives (mg)

Metal halide lamps (MHLs) appeared in the 60s of the twentieth century. and thanks to its high luminous efficiency, acceptable emission spectrum and sufficient high power are one of the most promising light sources.

Correcting the color of MGL radiation is based on the fact that chemical compounds are introduced inside the discharge tube, which make it possible to correct the spectral composition of the radiation of the mercury discharge itself without the use of a phosphor. This is facilitated by the fact that the halides of many metals evaporate more easily than the metals themselves and do not destroy quartz glass. Therefore, in addition to mercury and argon, as in RLVD, alkaline (sodium, lithium, cesium) and other aggressive metals (cadmium, zinc) are additionally introduced into the MGL discharge flasks in the form of halogen compounds (compounds with iodine, bromine, chlorine), which pure form cause very rapid destruction of quartz glass. After ignition of the discharge, when it is reached working temperature flasks, the halides partially transform into a vapor state. Once in the central zone of the discharge with a temperature of several thousand degrees Kelvin, the halide molecules dissociate into halogen and metal. Metal atoms become excited and emit their characteristic spectra. Diffusing outside the discharge channel and entering a zone with a lower temperature near the walls of the flask, they recombine into halides, which evaporate again. The use of halides sharply increased the number of chemical elements introduced into the discharge tube and, as a result, made it possible to create MGLs with a variety of spectra.

Most MGLs are produced with only two working electrodes and do not have (or have one) ignition electrodes. For this reason, they are connected to the network through a pulsed ignition device (IZU) and are ignited by a pulse of increased voltage, close to 2 kV (Fig. 60).

Depending on the application there are:

1) MGL general purpose(type DID);

2) tubular and spherical (DRISH type) MGLs with improved color rendering quality, used for color television and film shooting;

3) MGL for numerous special applications, mainly technological, for example, for irradiating plants.

Metal halide lamps for general lighting type DRI

DRI type lamps are similar in design to DRL type lamps with burners. The outer bulb, unlike DRL lamps, of most types of DRI lamps is not coated with phosphor, but sometimes standard bulbs of DRL lamps with a phosphor coating (DRIL type) are used.

The burning position significantly affects the parameters of DRI lamps, therefore some types of MGLs are produced in various modifications designed for different position combustion (vertical and horizontal).

The pulsation of the light flux of DRI lamps is significantly lower than that of DRL lamps and is about 30%.

Ambient temperature has a slight effect on the ignition process and the operation of DRI lamps.

When the supply voltage changes, the characteristics of DRI lamps change more noticeably than those of DRL type lamps: a change in voltage for each percent leads to a change in the luminous flux by approximately 2.5%.

DRI lamps are produced with power from 125 to 3500 W and, given their small volume, have a high power density. The luminous efficiency of DRI lamps is comparable to the luminous efficiency of the best LLs - more than 100 lm/W and in the future should reach 120 lm/W. The average burning time is 10,000...12,000 hours. The color rendering index is low, but higher than that of DRL lamps - from 45 to 65. In lamps with tin halides and dysprosium iodides, the color rendering index is from 80 to 90.

Some DRI lamps (type DRIZ) are produced in mirror reflective bulbs.

In terms of cost, DRI lamps are significantly inferior to other high-power RLs. The price (2006) of DRI250 is 900 rubles, versus 115 rubles. for DRL 250 and 325 rubles. at DNAT250.

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The emission spectrum of a mercury lamp has a maximum at a wavelength of 365 nm.  

The emission spectrum of mercury lamps has a line structure, and upon exposure of photosensitive layers containing diazo compounds, light with wavelengths of 3650, 4050 and 4358 A is active. In the intervals between these lines, the lamp radiation (continuous radiation background) is insignificant and only at high and ultrahigh sources pressure, the background value reaches 0 1 - 0 25 the radiation intensity of the main lines. From the above it follows that even with a slight shift in the absorption region of the diazo type material relative to the position of the main lines of the spectrum of mercury, a decrease in the sensitivity of the material is possible. Turner 77 ] observed, in particular, significant discrepancies between the experimentally found and calculated values ​​of the output energy when irradiating a diazo compound with monochromatic light with a wavelength of 3650 A and found that the relative sensitivity at 3130 A was only 25% of the sensitivity at 3650 A.  

The emission spectrum of medium-pressure mercury lamps has many high-intensity lines, but the intensity of the 253 7 nm line decreases sharply.  

In the emission spectra of mercury lamps, along with the lines, as the pressure increases, the continuous spectrum, the so-called background, becomes increasingly intense. At very high pressures (several tens of atmospheres), the spectra become continuous with individual maxima in those places where lines were located at low pressures.  

The results of these experiments and other observations allow us, with some approximation to the truth, to conclude that hexachlorane extinguishes that part of the emission spectrum of a mercury lamp that promotes the formation of the y-isomer.  

The radiation spectrum of mercury lamps has a line structure, and upon exposure of photosensitive layers containing diazo compounds, light with wavelengths of 3650, 4050 and 4358 A is active. In the intervals between these lines, the lamp radiation (continuous radiation background) is insignificant and only at high and ultra-high pressure sources The background value reaches 0 1 - 0 25 the intensity of the main lines. From the above it follows that even with a slight shift in the absorption region of the diazo type material relative to the position of the main lines of the spectrum of mercury, a decrease in the sensitivity of the material is possible. Turner observed, in particular, significant discrepancies between the experimentally found and calculated values ​​of the output energy when irradiating a diazo compound with monochromatic light with a wavelength of 3650 A and found that the relative sensitivity at 3130 A was only 25% of the sensitivity at 3650 A.  

Often in instruments, the wavelength drum associated with the mechanism for rotating the prism or grating is calibrated in relative units. The standard spectrum in the visible and ultraviolet region is the emission spectrum of a mercury lamp, which consists of a small number of intense lines. Such calibration with a standard substance should be repeated periodically, since the established compliance is violated during operation.  

For this purpose, instead of sunlight the sample is illuminated with lamps, the intensity of which can be compared with direct sunlight. Typically, luminaires are carbon arc or high-pressure xenon lamps; Sometimes mercury lamps are used. The radiation spectrum of mercury lamps is dominated by ultraviolet rays, which are the most active component daylight in the process of fading; Therefore, the use of these lamps further speeds up testing. Extrapolation of correlation results for unknown materials may lead to errors.  

Before starting measurements, the installation is calibrated according to wavelengths. To do this, the input part of the spectrograph, YSP-51, is illuminated with a light source that has a line spectrum with widely spaced lines, the wavelengths of which are well known. Next, the emission spectrum of the mercury lamp is recorded and deciphered and the relationship is established between the wavelengths of its individual lines (peaks on the recorder form) and the divisions of the drum connected to the motor rotating the prism part of the spectrograph. Based on these data, a dispersion curve of the installation is constructed.