Mercury discharge lamp

High pressure mercury lamp

Mercury discharge lamps are an electrical light source that uses a vapor gas discharge to generate optical radiation. Mercury vapor lamps are a type of gas discharge lamp. For the name of all types of such light sources in domestic lighting technology, the term "discharge lamp" (RL) is used, included in the International Lighting Dictionary, approved by the International Commission on Lighting. This term should be used in technical literature and documentation.

Depending on the filling pressure, a distinction is made between RL low pressure (RLND), high pressure (RLVD) and ultra-high pressure (RLSVD).

RLND includes mercury lamps with a partial pressure of mercury vapor in a steady state of less than 100 Pa. For RLVD, this value is about 100 kPa, and for RLVD - 1 MPa or more.

Low pressure mercury lamps (RLND) High pressure mercury lamps (RLVD)

RLVD are divided into lamps of general and special purpose... The first of them, which include, first of all, the widespread DRL lamps, are actively used for outdoor lighting, but they are gradually being replaced by more efficient sodium and metal halide lamps. Special-purpose lamps have a narrower range of applications, they are used in industry, agriculture, medicine.

Emission spectrum

Visible spectrum of a mercury lamp

Mercury vapors emit the following spectral lines used in gas discharge lamps:

The most intense lines are at 184.9499, 253.6517, 435.8328 nm. The intensity of the remaining lines depends on the mode (parameters) of the discharge.

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DRL type high pressure mercury lamps

DRL 250 lamp on a homemade test bench

DRL ( D ugovaya R mulberry L luminescent) - the designation RLVD adopted in domestic lighting engineering, in which, to correct the color luminous flux, aimed at improving color rendering, is used the radiation of a phosphor deposited on inner surface flasks.

For general lighting of workshops, streets, industrial enterprises and other objects that do not make high demands on the quality of color rendition and premises without the constant presence of people.

Device

DRL lamp with removed bulb

The first DRL lamps were manufactured with two-electrode technology. To ignite such lamps, a source of high-voltage pulses was required. A PURL-220 device (Starting Device for Mercury Lamps for a voltage of 220 V) was used as it. The electronics of those times did not allow the creation of sufficiently reliable igniting devices, and the PURL included a gas spark gap, which had a shorter service life than the lamp itself. Therefore, in the 1970s. the industry gradually discontinued the production of two-electrode lamps. They were replaced by four-electrode ones, which do not require external ignition devices.

To match the electrical parameters of the lamp and the power source, almost all types of radar lines with a falling external current-voltage characteristic need to use a ballast, which in most cases is a choke connected in series with the lamp.

The four-electrode DRL lamp (see the figure on the right) consists of an outer glass bulb 1 equipped with a threaded base 2. A quartz burner (discharge tube, RT) 3, filled with argon with the addition of mercury, is mounted on the lamp leg, mounted on the geometric axis of the outer bulb. Four-electrode lamps have main electrodes 4 and auxiliary (ignition) electrodes located next to them 5. Each ignition electrode is connected to the main electrode located at the opposite end of the RT through a current-limiting resistance 6. Auxiliary electrodes facilitate lamp ignition and make its operation more stable during the start-up period. The conductors in the lamp are made of thick nickel wire.

V recent times a number of foreign companies manufacture three-electrode DRL lamps equipped with only one ignition electrode. This design differs only in its greater manufacturability in production, having no other advantages over the four-electrode design.

Operating principle

The torch (RT) lamp is made of refractory and chemically resistant transparent material(quartz glass or special ceramics), and is filled with strictly dosed portions of inert gases. In addition, a metal is introduced into the burner, which in cold lamp has the form of a compact ball, or settles in the form of a deposit on the walls of the flask and (or) the electrodes. The luminous body of the RLVD is a column of an electric arc discharge.

The ignition process of a lamp equipped with ignition electrodes is as follows. When a supply voltage is applied to the lamp, a glow discharge occurs between the closely spaced main and ignition electrodes, which is facilitated by a small distance between them, which is significantly less than the distance between the main electrodes, therefore, the breakdown voltage of this gap is also lower. The appearance in the RT cavity of a sufficiently large number of charge carriers (free electrons and positive ions) contributes to the breakdown of the gap between the main electrodes and the ignition of a glow discharge between them, which almost instantly turns into an arc discharge.

Stabilization of the electrical and light parameters of the lamp occurs 10-15 minutes after switching on. During this time, the lamp current significantly exceeds the nominal and is limited only by the resistance of the ballast. The duration of the starting mode is highly dependent on temperature. environment- the colder, the longer the lamp will light up.

The electrical discharge in the torch of a mercury arc lamp produces visible blue or purple as well as powerful ultraviolet radiation. The latter excites the glow of a phosphor deposited on the inner wall of the outer bulb of the lamp. The reddish glow of the phosphor, mixing with the white-greenish radiation of the burner, gives bright light close to white.

A change in the supply voltage up or down causes a corresponding change in the luminous flux. A deviation of the supply voltage by 10 - 15% is permissible and is accompanied by a change in the luminous flux of the lamp by 25 - 30%. When the supply voltage decreases less than 80% of the nominal, the lamp may not light up, and when lit, it may go out.

The lamp becomes very hot when it burns. This requires the use of heat-resistant wires in lighting devices with mercury arc lamps, and makes serious demands on the quality of the cartridge contacts. Since the pressure in the burner of a hot lamp increases significantly, its breakdown voltage also increases. The supply voltage is insufficient to ignite a hot lamp. Therefore, the lamp must cool before re-ignition. This effect is a significant disadvantage of high-pressure mercury arc lamps, since even a very short interruption in the power supply extinguishes them, and re-ignition requires a long cooling pause.

Traditional scopes of DRL lamps

Lighting of open areas, industrial, agricultural and warehouse premises. Wherever this is due to the need for great energy savings, these lamps are gradually being replaced by NLVD (lighting of cities, large construction sites, high production workshops, etc.).

Enough original design Differing RLVD Osram of the HWL series (analogue of the DRV), having as a built-in ballast a conventional filament, placed in an evacuated cylinder, next to which a separately sealed burner is placed in the same cylinder. The filament stabilizes the supply voltage due to the bartering effect, improves color characteristics, but, obviously, it very noticeably reduces both the overall efficiency and the resource due to the wear of this thread. Such RLVDs are also used as household ones, since they have improved spectral characteristics and are included in a conventional lamp, especially in large rooms (the lowest-power representative of this class creates a luminous flux of 3100 lm).

Arc mercury metal halide lamps (DRI)

DRI lamps (Arc Mercury with Radiant Additives) are structurally similar to DRL, however, strictly dosed portions of special additives are additionally introduced into its burner - halides of some metals (sodium, thallium, indium, etc.), due to which it significantly increases light output(about 70 - 95 lm / W and higher) with a fairly good color of radiation. Lamps have ellipsoidal bulbs and cylindrical, inside which a quartz or ceramic burner is located. Service life - up to 8-10 thousand hours.

In modern DRI lamps, mainly ceramic burners are used, which are more resistant to reactions with their functional substance, due to which, over time, burners darken much less than quartz ones. However, the latter are also not removed from production due to their relative cheapness.

Another difference between modern DRI is the spherical shape of the burner, which allows to reduce the decline in light output, stabilize a number of parameters and increase the brightness of the "point" source. There are two main versions of these lamps: with E27, E40 sockets and soffit - with Rx7S sockets and the like.

To ignite DRI lamps, a breakdown of the interelectrode space with a pulse is required high voltage... In the "traditional" schemes for switching on these steam lamps, in addition to an inductive ballast choke, a pulsed ignition device is used - IZU.

By changing the composition of impurities in DRI lamps, you can achieve "monochromatic" glow different colors(purple, green, etc.) Thanks to this, DRI is widely used for architectural lighting. DRI lamps with an index "12" (with a greenish tint) are used on fishing vessels to attract plankton.

Arc mercury metal halide lamps with a mirror layer (DRIZ)

It is an ordinary DRI lamp, part of the bulb of which is partially covered from the inside with a mirror reflective layer, due to which such a lamp creates a directional stream of light. Compared with the use of a conventional DRI lamp and a mirror spotlight, losses are reduced by reducing re-reflections and light transmission through the lamp bulb. It turns out the same high accuracy focusing torch. In order to change the direction of radiation after screwing the lamp into the cartridge, DRIZ lamps are equipped with a special base.

Mercury-quartz ball lamps (DRSH)

DRSH lamps are ultra-high pressure mercury arc lamps with natural cooling. Are spherical and give a strong ultraviolet radiation.

High pressure mercury-quartz lamps (PRK, DRT)

High-pressure mercury arc lamps of the DRT type (Arc Mercury Tubular) are a cylindrical quartz flask with electrodes soldered at the ends. The flask is filled with a metered amount of argon; in addition, a metal one is introduced into it. Structurally, DRT lamps are very similar to DRL burners, and electrical parameters they are such that they allow the use of DRL ballasts of appropriate power for switching on. However, most DRT lamps are made in a two-electrode design, so special additional devices are required to ignite them.

The first developments of DRT lamps, which bore the original name PRK (Direct Mercury-Quartz), were carried out by the Moscow Electric Lamp Plant in the 1950s. In connection with the change in the normative and technical documentation in the 1980s. the designation PRK was changed to DRT.

The existing range of DRT lamps has wide range powers (from 100 to 12000 W). Lamps are used in medical equipment (ultraviolet bactericidal and erythemal irradiators), for air disinfection, food products, water, for photopolymerization of varnishes and paints, exposure of photoresists and other photophysical and photochemical technological processes... Lamps with a power of 400 and 1000 W were used in theatrical practice to illuminate decorations and costumes painted with fluorescent paints. In this case lighting equipped with UVS-6 ultraviolet glass filters, which cut off the hard ultraviolet and almost all visible radiation of the lamps.

An important disadvantage of DRT lamps is the intense formation of ozone during their combustion. If for bactericidal installations this phenomenon usually turns out to be useful, then in other cases the ozone concentration near the light device can significantly exceed the permissible sanitary standards... Therefore, rooms in which DRT lamps are used must have adequate ventilation to remove excess ozone.

In small quantities, ozone-free DRT lamps are manufactured, the bulb of which has an outer coating of quartz doped with titanium dioxide. Such a coating practically does not transmit the ozone-forming line of resonance radiation of 253.7 nm.

Notes (edit)

Links

Incandescent	Incandescent lamp Halogen lamp
Fluorescent	Fluorescent lamp (compact fluorescent lamp) Cathodoluminescent lamp Induction lamp Mercury lamp Black light lamp

Unlike fluorescent lamps, where the vapor pressure of mercury was fractions of a millimeter mercury column, in mercury DRL lamps a gas discharge in mercury vapor is used at pressures much higher than atmospheric. Such lamps are a thick-walled quartz tube (burner) with two or more electrodes, mounted in an outer bulb made of heat-resistant glass, the walls of which are internally coated with a phosphor. Inside the burner there is a metered drop of mercury and argon gas; tungsten electrodes are soldered into its ends. Argon facilitates the ignition of the discharge in the cold tube, and after the discharge is ignited, the process of evaporation of mercury begins, which turns into a vaporous state. When an arc discharge is established between the working electrodes, the density and temperature of mercury vapor along the tube diameter will be unequal; the temperature along the tube axis will be maximum. Due to this, the current density in the center of the tube is maximal, and the discharge has the form of a luminous cord located along the axis of the tube.
With an increase in the vapor pressure of mercury, the nature of the spectrum emitted gas discharge... The higher the pressure, the greater the brightness of the solid background. Due to the change in the emission spectrum, the color of the light created by the mercury lamp changes from blue-green at low pressures to white at high pressures... The use of DRL lamps for lighting turned out to be possible as a result of obtaining temperature-resistant phosphors, with the help of which it was possible to correct the chromaticity of the radiation of a mercury discharge. The fact is that the chromaticity of the discharge radiation in mercury vapor, which gives an intense light of a bluish tint, makes correct perception impossible. color shades: the faces of people become deathly pale, the lips become bluish-gray, the colors of the surrounding objects are distorted. Therefore, mercury lamps without a phosphor are considered practically unsuitable for lighting, even in cases where high requirements are not imposed on color reproduction, for example, when lighting streets. It was possible to get rid of this drawback with the help of a phosphor, which is applied to the inner surface of the outer bulb of the DRL lamp. This bulb has a shape that ensures the same temperature of the entire surface covered with a phosphor during operation of the lamp. The phosphor absorbs well the invisible ultraviolet radiation passing through the quartz walls of the tube, and converts it into an orange-red visible radiation, thereby correcting the color of the lamp radiation. In this case, the phosphor almost does not absorb the visible radiation of the mercury discharge.
DRL mercury lamps are produced in two modifications: two-electrode and four-electrode.
In two-electrode DRL lamps, a quartz burner is equipped with two working electrodes. The ignition voltage of these lamps is many times higher than the supply voltage. They ignite when applied to their electrodes. impulse voltage several kilovolts. Under the action of this voltage pulse, an electrical breakdown occurs between the electrodes, argon facilitates further development discharge. After the occurrence of a stable discharge in argon, the process of evaporation of mercury begins due to the heat released in the discharge. The ignition voltage is reduced and the main charge is established in the lamp. A significant drawback of these lamps is that their ignition voltage is several times higher operating voltage networks. To turn on a two-electrode lamp, a complex ballast is required, consisting of a reactor, a selenium rectifier, a spark gap, a capacitor and a resistor. The two-electrode lamp (Fig. 1, a) is a straight quartz tube (burner),
built into the external glass flask made of heat-resistant glass, covered from the inside with a layer of phosphor. Inside the burner there is a metered drop of mercury and argon gas; tungsten electrodes are soldered to its ends.

Rice. 1. Arc mercury Fluorescent Lamp DRL type with corrected chromaticity.
a - two-electrode lamp; b - four-electrode lamp; 1 - mercury quartz tube; 2 - outer flask; 3 - phosphor; 4 - threaded base; 5 - working electrodes; 6 - ignition electrodes; 7 - resistors.
When voltage is applied to the lamp (Fig. 2, a), the capacitor C is charged through the selenium rectifier B and the limiting resistor R. When the charge reaches the spark gap ignition voltage (180-200 V), the capacitor is discharged through the spark gap RZ to the additional reactor winding P (ignition winding ), as a result of which a high voltage pulse is induced at the ends of the main winding of the ballast reactor, igniting lamp L.
The insulation of the wires laid between the two-electrode DRL lamp and the ballast must be designed for a voltage of at least 3000 V. The desire to simplify ballasts and increase the reliability of operation has led to the creation of four-electrode lamps, which have now been wide distribution... These lamps are designed in such a way that they are ignited at the operating voltage of the mains.
In fig. 1.6 shows a four-electrode DRL lamp, it differs from a two-electrode lamp in that it has two additional ignition electrodes located in the immediate vicinity of the working electrodes.



Rice. 2. Schemes for switching on lamps of the DRL type.
a - a diagram of a two-electrode lamp; b - diagram of a four-electrode lamp with a reactor: c - diagram of a four-electrode lamp with an autotransformer; L-lamp type DRL; Р - reactor; and<д - дополнительная обмотка реактора (обмотка зажигания); РЗ- разрядник; В - селеновый выпрямитель; R - резистор; С - конденсатор; Ат - автотрансформатор.
The ignition electrodes are connected to opposite working electrodes through resistors located inside the outer bulb. There is a metered drop of mercury and argon gas inside the burner. The ignition electrodes in the lamp are designed to facilitate ignition of the lamp. When the lamp is turned on, a glow discharge occurs between the igniting and working electrodes, providing the necessary ionization of the gas. The discharge is established between the working electrodes, since the resistance of the gas gap is less than the resistance of the ignition electrode included in the circuit. As mentioned above, the ignition of four-electrode lamps can be carried out from the mains voltage. The schemes for their inclusion in the network are simple (Fig. 2, b). The reactor is switched on in series with the lamp. In some cases, when the lamps have to be ignited at extremely low outside temperatures, it is possible to use a ballast with an autotransformer, which provides the necessary increase in the supply voltage (Fig. 2, c).

A characteristic feature of DRL lamps is that after switching on the lamp to the network and igniting the discharge in it, it takes 3 to 10 minutes to establish a stationary mode of its operation, depending on the lamp power. This period can be called the lamp-on period. A stationary state occurs with the complete evaporation of mercury, after which all electrical and light parameters of the lamp do not change. The duration of the starting period of the lamp is influenced by the ambient temperature. At low temperatures, the start-up time increases.
It should be noted that after turning off the lamp, its re-ignition cannot be carried out until it cools down. This is due to the fact that the mercury vapor pressure of the uncooled lamp is increased and, as a result, the ignition voltage must be increased. It is only natural that the time it takes for the lamp to cool down before re-lighting it depends on the ambient temperature. This time is on average 5 to 8 minutes. For this reason, DRL lamps are not allowed to be used for emergency lighting.
DRL lamps are used in industrial premises with a height of more than 6 m, where correct color discrimination is not required, to illuminate roads in industrial areas with heavy traffic of people and vehicles and areas requiring increased illumination, to illuminate streets, roads and squares.
Table 5. Main characteristics of DRL lamps

Lamp type	Power, W	Lamp voltage, V		Luminous flux, lm	Dimensions, mm		Service life, h
						Full length
	Four-electrode (GOST 16354-77)
		Two-electrode

Notes: 1. The base of the DRL lamp with a power of 80 and 125 W is of the Ts27 type, for the rest - SHO.
2. For DRL lamps, ballasts are manufactured to be connected to a 220 V network.
The main electrical, light and technical characteristics of four-electrode and two-electrode lamps, as well as their dimensions are given in table. 5.
Control gears for switching on four-electrode DRL lamps are produced in two main types: built-in and independent. The first type of device is designed to be built into closed outdoor lighting fixtures and can be operated at ambient temperatures from -25 to + 35 ° C and relative humidity up to 95%. The second type of device is equipped with a protective casing and is installed separately from the luminaire and can be used in industrial premises with a normal environment with an ambient temperature of +5 to + 35 ° C and a relative humidity of up to 75%. Technical characteristics of ballasts for two- and four-electrode DRL lamps are given in table. 6.
Table 6. Main technical characteristics of ballast for DRL lamps for voltage of 220 V

Machine type	Lamp power, W	Lamp current, A		Dimensions, mm
			launcher
Two-electrode
1API-250-DR L / 220
1API-500-DRL / 220
1API-750-DRL / 220
1API-1000-DR L / 220
Four-electrode lamps
DBI-80/125-DR L / 220-V
DBI-250-2DRL / 220-V
1DBI-400-DRL / 220-V
1DBI-250-DRL / 220-N
1DBI-400-DRL / 220-N
1DBI-400-DRL / 220-N
1DBI-700-DRL / 220-N
1D BI-1000-DRL / 220-N

Notes: 1. Designations: B - built-in, for installation in the luminaire (ambient temperature from -25 to +35 ° С and relative humidity 95%); H - independent, for installation separately from the luminaire (ambient temperature from +5 to +35 ° С, relative humidity 75%).
2. Average power factor of ballast for all lamps is 0.5-0.45.

To illuminate large areas, a somewhat outdated but rather effective DRL lamp is often used. It can be seen on the streets of cities and towns, in the shops of enterprises and some other places. The abbreviation DRL can be deciphered as an arc device, mercury, phosphor.

What is a DRL device?

DRL lamps consist of:

• glass bottle;
• threaded base;
• mercury-quartz burner;
• main and additional electrodes;
• carbon resistor.

The burner, also called a tube, is filled with argon and a droplet of mercury. Additional electrodes are installed in four-electrode products. They greatly facilitate the ignition process of the appliance. Its combustion itself also becomes more stable.

The base is a structure for receiving electrical energy from the network. It has threaded and point current-carrying parts, which in the lamp holder are connected to the corresponding contacts and transmit energy to the electrodes.

The quartz burner is the main part of the product. This is a tube with electrodes. They are basic (2 pieces) and additional (also 2 pieces).

A glass flask is the outer shell of the device. A quartz burner is inserted inside it with conductors coming from the contacts of the base. Almost all mercury arc fluorescent lamps used for lighting have a bulb from which air is pumped out and nitrogen is pumped in instead. Limiting resistances are included in the circuit of additional electrodes. The inner side of the flask is covered with a phosphor layer.

The first device of this type had 2 electrodes. It required an additional trigger. It was soon discontinued. A modern four-electrode lamp only needs a choke. The process of its ignition looks like this:

• voltage is applied to closely spaced electrodes;
• a glow discharge arises between them;
• this discharge breaks through the distance separating the main electrodes, between which an arc discharge appears;
• after 10-15 minutes, the lamp starts to burn normally.

The time during which mercury lamps go to normal combustion depends on the air temperature. At lower temperatures, this time increases. Mercury lamps emit a visible blue color and fairly powerful radiation in the ultraviolet range. Ultraviolet radiation causes the phosphor to glow on the inner walls of the flask. As a result, mercury lamps glow bright white. The color may change slightly depending on the drop or increase in the line voltage.

Light bulbs get hot to high temperatures during operation. This requires high quality cartridges and product caps. This is the disadvantage of the products. The disadvantage of such lamps is that the gas-discharge device must cool down well before switching it on again.

General information about lamps

The DRL lamp device is considered. Now you need to get acquainted with the general information that may come in handy. These include some technical characteristics:

• the lamps and the lamps themselves are endowed with great resistance to various atmospheric influences and have a high luminous efficiency;
• DRL power ranges from 80 to 1,000 W;
• their service life is 10,000 hours.

The disadvantage of the products is the formation of an excess amount of ozone during operation. Therefore, a high-quality ventilation system must be present in the room, capable of removing the excess of this gas.

The marking of the lamp contains information about its power. They are indicated by the number that follows the letters. The marking is as follows:

• DRL 80;
• DRL 125;
• DRL 400;
• DRL 500;
• DRL 700;
• DRL 1,000.

Each of them has its own characteristics. For example, the DRL 250 lamp is used very often. Its characteristics:

• its power is 250 W;
• consumed current - 4.5 A;
• base - E 40;
• luminous flux - 13,000 Lm;
• light output - 52 Lm / W;
• color temperature - 3 800 K;
• burning period - 10,000 hours.

Each lamp has similar characteristics. On the basis of DRL today, special products are produced, which are called metal halide lamps. They include iodides of various metals, which change the color of visible radiation. They also increase the efficiency of the devices.

Conclusion on the topic

Mercury lamps of various types have long been used in production and in everyday life. They come in different powers and can emit visible rays of different colors. Their service life is very long, reaching 10 thousand hours. A certain mercury arc lamp with different caps is inserted into luminaires of different types. Repair of products is most often limited to their replacement, since worn-out lamps lose up to 50% of the emitted light. The lamps emit whirring sounds during operation.

The gas discharge lamp has its own varieties. The DRV is distinguished by the presence of a tungsten filament, which is both a light source and a voltage limiter. It turns on like an ordinary light bulb, without starting equipment. DRUF emits rays in the ultraviolet spectrum. DNaT 250 is a tubular product with sodium vapor. To start, you need to use special equipment. These products are used in lamps located on the streets, in industrial premises, and in floodlights.

On the windows of shops selling electrical goods, next to the usual incandescent lamps and spirals of "housekeepers", you can see unusual models with white opaque glass and a large E40 base (although there are options for E27). These are DRL lamps. Their technical characteristics are so high that, despite the very venerable age of the technology (the first were launched into series in the distant 50s), they are still in demand. They are actively used in industrial premises and for street lighting and even as a light source in the working area of ​​overhead cranes, since their resistance to electrode damage is higher than that of other lighting devices.

What is a DRL lamp

Let's start with the abbreviation: the abbreviation stands for "mercury arc lamp". Sometimes the letter "D" is deciphered as "throttle", but with the advent of throttleless modifications, this became only partly true. So, its outer flask is made of transparent glass, resistant to heating, covered on the inside with a layer of heat-resistant phosphor (a substance that converts ultraviolet radiation into light visible to the eye). By the way, hence the white color of the bulb. Inside it is a sealed tube made of high-strength quartz glass, into which two or four tungsten electrodes are inserted. This is sometimes referred to as a "torch" because the arc is formed here. This tube contains some liquid mercury in a high pressure argon atmosphere. The DRL mercury lamp is incredibly popular primarily due to its excellent performance characteristics. For example, a 500W incandescent light bulb has a luminous flux of about 8,400 lumens and a claimed life of just 1,000 hours.

For comparison: a 400 W DRL lamp produces 24,000 lm, and the burning time is at least 15 thousand hours. That is, to get the same glow, you need to install 3 incandescent bulbs of half a kilowatt each. Of course, in reality, such a long operating time is rarely achieved, since as the phosphor wears out, the glow decreases and the lamp is changed to a new one, even if it can still work. At the same time, the average incandescent light bulb burns out in the same way before the cherished 1000 operating hours are reached.

Principle of operation

In modifications with two electrodes, it is necessary to use start-up control equipment (PRA) - a spark gap, a capacitor, a rectifier and a reactor. Some of the elements are located inside the outer bulb. In fact, the task of the ballast is reduced to creating an initial voltage pulse of several kilovolts, which is necessary to ignite the lamp, as well as to further limit the current consumption. In order for the DRL lamp to light up, it is necessary to ensure that an electric arc appears between the electrodes of the inner quartz tube. And since the value of the breakdown voltage of the gas gap is much higher than the standard 220 V, it is precisely for a one-time jump that a ballast is required.

After the arc appears, the mercury in the tube turns into a gaseous form. Since the heating of the gas in the "burner" is non-uniform, the maximum current density falls on the central part - a kind of cord is formed. Radiation from the arc strikes the phosphor layer, causing it to glow.

Nuances of use

Although the spectrum of the electric arc is partially visible to the naked eye, ultraviolet radiation is also generated along with harmless light. Therefore, in the event of damage to the outer bulb, such a DRL lamp must be disposed of immediately. If the "burner" is broken, there is an additional hazard in the form of mercury vapor.

After lighting the lamp and until the steady glow intensity takes place from 2 to 10 minutes. During this time, there is a complete evaporation of mercury and temperature equilibration of the areas. At low ambient temperatures, the duration may increase. The time is also influenced by the power consumption. In addition, if the supply voltage is even removed for a short time, then the lamp does not re-ignite immediately, but only when the temperature of the bulb decreases. This is due to the fact that with increasing heating, the gas pressure increases, which, in turn, requires a higher voltage for the breakdown of the gap.

And, finally, it should be noted that the light emitted by the DRL lamp is pulsating. Since the mains frequency is 50 Hz, the arc changes direction twice per unit time, which ultimately gives about 100 Hz.

Although the phosphor partially mitigates the flicker, the use of such lamps in rooms with rotating assemblies (motor shafts) should be limited to avoid stroboscopic effects.

Modifications

There are several variations of these lamps. Above, we considered the classical scheme with two electrodes, but there are also more advanced, four-electrode models. Their main difference is that two more conductors are inserted into the central tube. Thanks to this, it is possible to abandon the use of an external control gear, using such a lamp in a conventional luminaire, suitable in size and type of base. Such models are called throttleless. When 220 V power is applied, a breakdown occurs between each main and nearby auxiliary electrodes. Mercury vapor is ionized, the resistance of the gas gap decreases, which is sufficient for the appearance of the main arc.

Key parameters

What should be taken into account when choosing DRL lamps? The characteristics, of course. And they are as follows:

• Electric power. Two-electrode modifications consume from 250 W to 1 kW. Four-electrode - from 80 to 1000 W.
• Base type. Usually, high-power ones are supplied with E40, and more economical ones - with E27.
• Current load on the network. Kilowatts consume up to 8 A.
• Luminous flux intensity. This is 3200 Lumens for 80W and 52000 for 1 kW.
• Service life and dimensions.
• The need to use ballasts.

Here's what DRL means:

• D - arc;
• P - mercury;
• L - luminescent (or luminous).

DRL design

This is one of the common designs of electric lamps. Its principle of operation is based on the phenomenon of an electric discharge in a gas flowing at a high pressure in the flask. This makes it possible to obtain a radiation source similar to a spiral in an incandescent lamp. But it is not a red-hot tungsten spiral, but a bright cord of glowing mercury vapor, which seems to be stretched between two electrodes.

Such a light source appears only at a sufficiently high pressure in the flask. This is a real voltaic arc, which determined the first word of the name of the lamp. Looking at the lamp, you can see a threaded base and an elliptical completely opaque white outer bulb, inside which there is a device that performs all the main functions and is not visible from the outside.

It . She identified the second word from the title.

It is in it that the voltaic arc appears. The electrodes between which it occurs are made of a refractory alloy and are located at the ends of a quartz tube. Their quality and lifetime mainly determine the lamp life as a whole. Burners can be either two or three to four electrodes. Two-electrode torches start glowing after applying a voltage pulse to the electrodes capable of breaking the spark gap between them.

This simplifies the burner design, but complicates the ballast layout (left image). The disadvantage of the two-electrode circuit is also the dependence on the humidity of the ambient air. In wet weather, breakdown may occur in the lamp base and it will not be able to ignite. Also, restarting the lamp with a two-electrode torch is the most prolonged in time.

Transient processes

The fact is that DRL lamps cannot quickly reach their nominal light emission mode. The reason for this phenomenon lies in the processes that occur in the burner after the breakdown of the spark gap. Mercury is the main source of radiation from the burner. And this metal under normal environmental conditions is in liquid form and the concentration of its vapors when the burner is first turned on is close to vacuum. And if the air temperature is below zero, the depth of this vacuum increases even more.

Argon is added to the burner to maintain spark gap penetration over a wide temperature range. After the breakdown of the gap between the electrodes, a glow appears in it due to the electric current between the electrodes. If current flows, then heat is generated. The burner heats up, and with it the mercury deposited on the inner surface of the burner bulb. The amount of vapor increases, the electric current, and the brightness of the glow also increases.

This process takes depending on the initial ambient temperature and can be longer than 5-10 minutes for high power lamps. At first, the mercury completely evaporates, and then its vapors are heated. When the pressure inside the torch bulb reaches its maximum value, determined by the current of the volt arc, the brightness of the torch light stabilizes. The parameters of the stable glow of the DRL are determined by both the burner and the ballast.

But if the supply voltage suddenly disappears for a time longer than the time parameters of the EMF of the ballast self-induction, the lamp will go out. And since the pressure in it can be about 100 kilopascals, it is impossible to break through such a spark gap with the voltage of starting the lamp. It needs to cool down. But the temperature drop in the outer flask occurs from about 400 degrees Celsius to the ambient temperature. And the burner inside it is in rarefied nitrogen with almost perfect thermal insulation.

The burner in nominal mode heats up to 800 - 900 degrees Celsius. Therefore, the lamp cools down for a rather long time, about the same as it starts up. A breakdown of heated mercury vapor between two electrodes is impossible. Therefore, the two-electrode torch cools down longer than the four-electrode torch. This is another drawback of it. In the four - electrode torch, one additional one is located near each of the main electrodes.

It is connected through a resistor to the bus of the opposite potential. Therefore, a small spark gap is obtained between the main and additional electrodes, which is easily punctured by the lamp supply voltage. And the circuit for switching on a four-electrode lamp consists of a conventional choke and the lamp itself:

Color rendition and design variations

The capacitor, which improves the start of the lamp, is structurally combined with a choke in one housing. Scheme b) used for areas with cold climates and severe frosts in winter. However, despite the brightness of the voltaic arc, in mercury vapor, it creates visible light of unacceptable color rendition with a predominance of blue tints.

Therefore, the ultraviolet radiation of the burner is converted into visible light by the phosphor. It is applied to the inside of the lamp bulb. Phosphor and its luminescence determined the third word in the name of the lamp. But, despite the luminescence similar to tubular and basement "energy-saving" lamps with a glow discharge in mercury vapor, it is impossible to obtain high-quality light in a DRL. The burner is shining too brightly and its spectrum is superimposed on the spectrum of the phosphor. And the delays in turning on and cooling down the lamp make it unacceptable for use in everyday life - at most in a garage for outdoor lighting.

Therefore, their use as part of emergency lighting is also unacceptable. DRL is best used to illuminate large areas, especially in the open air and with temperature differences in the range from -40 to +40. For high-quality street lighting, specialized DRLs are used. In them, the ballast replaces a resistor made in the form of a tungsten coil. It is housed inside an evacuated outer bulb together with a burner.

The combined emission of light by a tungsten coil, a phosphor and a burner has good color rendering. But this design of the lamp turns out to be less reliable and durable, since the life of the lamp is determined by the tungsten coil. The main characteristics of DRL are shown in the image below:

DRL lamps are an inexpensive and reliable source of bright white light. Therefore, there is always a place for them to work where they will be most effective.