What type of discharge is in gas discharge lamps. Types and principles of operation of modern LED lamps. Operating principle of a gas discharge lamp

Areas of use

Due to the line spectrum of radiation, gas-discharge lamps were initially used only in special cases when obtaining a given spectral composition of radiation was a factor more important than the value of luminous efficiency. A wide range of lamps has emerged, intended for use in research equipment, which are united under one general name - spectral lamps.

Figure 1. Spectral lamps with sodium and magnesium vapor

Possibility of creating intense ultraviolet radiation, characterized by high chemical activity and biological effects, led to the use of gas-discharge lamps in the chemical and printing industries, as well as in medicine.

A short arc in gas or metal vapor at ultra-high pressure is characterized by high brightness, which has now made it possible to abandon the open carbon arc in searchlight technology.

The use of phosphors, which made it possible to obtain gas-discharge lamps with a continuous emission spectrum in the visible region, determined the possibility of introducing gas-discharge lamps into lighting installations and displacing incandescent lamps from a number of areas.

The features of isothermal plasma, which provides a radiation spectrum close to that of thermal sources at temperatures inaccessible in incandescent lamps, led to the development of ultra-powerful lighting lamps with a spectrum almost identical to that of the sun.

The practical inertia-free nature of a gas discharge has made it possible to use gas-discharge lamps in phototelegraphy and computer technology, as well as to create flash lamps that concentrate enormous light energy in a short-term light pulse.

Video 1. Flash tubes

Requirements for reducing energy consumption in all areas National economy are expanding the use of economical gas-discharge lamps, the production volume of which is constantly growing.

Glow lamps

As is known, a normal glow discharge occurs at low current densities. If the distance between the cathode and the anode is so small that the discharge column cannot be accommodated within it, then cathode glow and negative glow occur, covering the surface of the cathode. The power consumption in a glow discharge lamp is very small, since the current is low, and the voltage is determined only by the cathode drop. The luminous flux emitted by the lamp is insignificant, but it is absolutely sufficient for the ignition of the lamp to be noticeable, especially if the discharge occurs in a gas that produces colored radiation, for example, neon (wavelength 600 nm, red color of radiation). Such lamps various designs widely used as indicators. The so-called digital lamps were previously integral part many automatic devices with digital indicators.

Figure 3. Glow lamp designed to display numbers

With a long gas-discharge gap with a distance between the electrodes significantly greater than the near-cathode region, the main radiation of the discharge is concentrated in the discharge column, which in a glow discharge differs from the column in an arc discharge only in its lower current density. The radiation of such a column can have high luminous efficiency over a long length. The high value of the cathode voltage drop in a glow discharge led to the development of lamps for high supply voltages, that is, the voltage on them significantly exceeds the voltage considered safe under operating conditions in indoors, especially household ones. However, such lamps are successfully used for various kinds of advertising and signaling installations.

Figure 4. Lamps with a long glow column

The advantage of a glow discharge lamp is the simplicity of the cathode design compared to the cathode of an arc discharge lamp. In addition, the glow discharge is less sensitive to the presence of random impurities in the gas-discharge space, and therefore more durable.

Arc lamps

Arc discharge is used in almost all gas-discharge lamps. This is due to the fact that during an arc discharge the cathode voltage drop weakens and its role in the lamp energy balance decreases. Arc lamps can be manufactured for operating voltages equal to the voltages electrical networks. With small and medium density arc discharge current, as well as at low pressure in the lamp, the source of radiation is mainly the positive column, and the glow of the cathode has practically no significance. By increasing the pressure of gas or metal vapor filling the burner, the cathode region gradually decreases, and at significant pressures (more than 3 × 10 4 Pa) it practically does not remain at all. By increasing the pressure in the lamps, high radiation parameters are achieved at small distances between the electrodes. High light output values ​​at very short distances can be obtained at ultra-high pressures (more than 10 6 Pa). With increasing pressure and decreasing distance between the electrodes, the current density and brightness of the discharge cord greatly increases.

With an increase in pressure and current density, an isothermal plasma is formed, the radiation of which mainly consists of non-resonant spectral lines that arise when an electron in an atom passes to lower, but not fundamental, levels.

Arc discharge is used in a wide variety of gases and metal vapors from the lowest pressures to ultra-high ones. In this regard, the designs of arc lamp bulbs are extremely diverse both in shape and in the type of material used. For ultra high pressure lamps great importance acquires the strength of flasks under conditions high temperatures, which led to the development of appropriate methods for their calculation and study of parameters.

After the appearance of the arc discharge, the bulk of the electrons are knocked out of the cathode spot. The luminous cathode part of the discharge begins with a cathode spot, which is a small luminous point on the spiral. There are several cathode spots. In self-heating cathodes, the cathode spot occupies a small part of its surface, moving along it as the oxide evaporates. If the current density is high, local thermal overloads occur on the cathode material. Due to such overloads, it is necessary to use cathodes of special complex designs. The number of cathode designs is varied, but they can all be divided into low pressure, high pressure and ultra high pressure lamp cathodes.

Figure 5. Low Pressure Tubular Discharge Lamp

Figure 6. High pressure discharge lamp

Figure 7. Ultra-high pressure discharge lamp

A variety of materials used for arc lamp bulbs, large values currents require solving the issue of creating special bushings. You can read in detail about the designs of gas-discharge lamps in specialized literature.

Lamp classification

Similar to incandescent lamps, gas-discharge lamps differ in their area of ​​application, type of discharge, pressure and type of filling gas or metal vapor, and the use of phosphor. If you look through the eyes of gas-discharge lamp manufacturers, they may also differ in design features, the most important of which are the shape and dimensions of the bulb (gas-discharge gap), the material used from which the bulb is made, the material and design of the electrodes, the design of the caps and terminals.

When classifying gas-discharge lamps, some difficulties may arise due to the variety of characteristics on the basis of which they can be classified. In this regard, for the classification of the currently accepted and used as the basis for the designation system for gas-discharge lamps, a limited number of characteristics have been defined. It is worth noting that low-pressure mercury tubes, which are the most common gas-discharge lamps, have their own designation system.

So, to designate gas-discharge lamps, the following main features are used:

1. operating pressure(ultra-high pressure lamps - more than 10 6 Pa, high pressure - from 3 × 10 4 to 10 6 Pa and low pressure - from 0.1 to 10 4 Pa);
2. composition of the filler in which the discharge occurs (gas, metal vapors and their compounds);
3. name of the gas or metal vapor used (xenon - X, sodium - Na, mercury - P and the like);
4. type of discharge (pulse - I, glow - T, arc - D).

The shape of the flask is indicated by letters: T – tubular, Ш – spherical; if a phosphor is applied to the lamp bulb, then the letter L is added to the designation. Lamps are also divided according to: area of ​​luminescence - glow lamps and lamps with a discharge column; according to the cooling method - for lamps with forced and natural air cooled, water-cooled lamps.

Mercury tubular fluorescent lamps low pressure is usually denoted more simply. For example, in their designation the first letter L indicates that the lamp belongs to this species light sources, the subsequent letters - and there may be one, two or even three of them - indicate the color of the radiation. Chroma is the most important parameter designations, since color determines the area of ​​use of the lamp.

The classification of gas-discharge lamps can also be carried out according to their significance in the field of lighting technology: high-pressure arc lamps with corrected color; high pressure tube arc lamps; high pressure arc; arc sodium lamps low and high pressure; high pressure arc; ultra-high pressure arc balls; xenon arc tube and ball lamps; low pressure fluorescent lamps; electrode-lighting, pulsed and other types of special gas-discharge lamps.

A gas discharge lamp is a light source that emits energy in the visible range. Physical basis is an electric discharge in gases. Gas discharge lamps are also simply called discharge lamps.

Gas discharge lamps: types and types

Types (types) of gas discharge lamps:

Device:

1. flask;
2. base;
3. burner;
4. main electrode;
5. ignition electrode;
6. current limiting resistor.

Principle of operation

In the filler located inside the flask, an electrical discharge occurs between the electrodes. This energy becomes the light that is scattered and transmitted through the glass bulb.

The diodes are equipped with a ballast for stabilization, current limitation, and ignition. For all gas-discharge lamps, the light output is not instantaneous - about two to three minutes are needed for the device to accumulate full power.

Classification of GL

They differ:

• by type of discharge;
• by type of gas;
• composition of metal vapors;
• internal pressure;
• use of phosphor;
• scope of application.

They also differ according to the classification of manufacturing plants in the characteristic design features:

1. shape and size of the flask,
2. design of electrodes,
3. materials used,
4. internal design of the base and outputs.

There are a lot of criteria by which gas-discharge lamps are usually classified. To avoid getting completely confused, we recommend going through the list:

• type of internal gas (metal vapors or combinations thereof - xenon, mercury, krypton, sodium and others, as well as gases);
• internal working pressure (0.1 - 104 Pa - low, 3 × 104 - 106 Pa - high, 106 Pa - ultra-high);
• type of internal discharge (pulse, arc, glow);
• shape of the flasks (T - tubular, W - spherical);
• cooling method (devices with water, natural, forced cooling);
• The application of phosphor to the flask is marked with the letter L.

According to the light source, GLs are divided into:

1. fluorescent lamps (LL) with light coming out from the phosphor layer that covers the diode;
2. gas-light with light coming out from a gas discharge;
3. electrode-lighting, which uses the glow of electrodes (they are excited by a gas discharge).

By pressure value:

• GRLVD - high pressure gas discharge lamps;
• GRLND - low pressure gas discharge lamps.

Discharges are characterized by high transformation efficiency electrical energy into the light.

Model	Description
	Substance: mercury metal vapor. A variety of gas discharge lamps, electrical source light, a gas discharge in mercury vapor is used directly to generate optical radiation.
	Substance: mercury metal vapor. Electric mercury discharge lamp oriented to obtain UV radiation, with a quartz glass flask. There are also mercury-quartz lamps.
	Substance: mercury metal vapor. A type of high pressure gas discharge lamps (GRL).
	Substance: mercury metal vapor. A type of electric diodes, widely used for lighting large and voluminous areas (factory workshops, streets, sites), where there are no requirements for the color rendering of lamps, but high luminous efficiency is required, DRL lamps, as a rule, with a power of 50 to 2000 W, are initially designed for work in electrical networks alternating current with supply voltage 220 V.
	Substance: mercury metal vapor. Similar in principle to working with mercury and sodium, but with an advantage. The tungsten spiral allows you to turn on the lamp without a ballast; they are used in lighting devices aimed at lighting industrial facilities, streets, open spaces, park areas
	Substance: sodium. A sodium gas discharge lamp is an electric light source, the luminous body is a gas discharge in sodium vapor. The dominant in the spectrum is the resonant radiation of sodium, the light is bright orange-yellow.
	Substance: inert gases. They are filled inside under low pressure with neon, emitting an orange-red glow.
	Substance: inert gases. They are classified as sources of artificial light; in their flask filled with xenon, an electric arc glows and emits bright white light, the spectrum close to daylight.
	Substance: neon with mercury. Filled with neon and mercury, they act as an indicator, in normal mode the glow of mercury is not visible, but when a discharge is ignited on the electrodes that are as far apart as possible, it becomes noticeable, the indicator ones are characterized by an orange-red glow, the electrode materials are molybdenum, iron, aluminum, nickel. The cathode is coated with an activating substance to reduce the ignition threshold. It is connected to the network of the appropriate voltage through a ballast resistor, which prevents the transition of a glow discharge into an arc discharge; in this case, for certain types of lamps, a current-limiting resistor is built into the base, and the lamp itself is connected directly to the network.

Model	Description
D2S	Diode with base. A good replacement for the car's standard lensed optics. Installed in headlights for low beam and high beam - illuminates both the road and the side of the road. Average service life is 2800-4000 hours. Earthquake resistant, high light quality. Luminous flux – 3000-3200 lm. Color temperature – 4300 K. Power consumption – 35 W.
D1S	Xenon light. Mounted in car headlights for high and low beam. With a base. Also designed for lensed optics. Luminous flux – 3200 lm. Power consumption – 35 W. Color temperature – from 4150 to 6000K. Service life – at least 3000 hours.
	Gas-discharge mercury with E40 base. Installed in lamps with E40 socket. Used for external and interior lighting.Functions in conjunction with ballasts. Service life 5000 hours. Rated power 250 W. Color temperature 5000K.
D4S	Reliable and high-quality light source. Environmentally friendly. Installed in car headlights. Characterized by a wide spectrum of radiation. Rated power 35 W. Luminous flux – 3200 lm, service life – 3000 hours. Color temperature – from 4300 to 6000 K.
D3S	Original lensed optics with a socket. Rated power 35 W, luminous flux – 3200 lm. Service life – 3000 hours. Color temperature – from 4100 to 6000K. Service life 3000 hours. No mercury. Designed for car lighting.
H7	Base for halogen lamps.
	Gas discharge mercury lamp high category. Installed in luminaires with an E40 socket, used for external and internal lighting, and functions in conjunction with ballasts. Rated power 250 W, luminous flux – 13000 lm. Color temperature – 4000 K, base E40.
	GL with an ellipsoidal flask shape. Used for external and internal lighting. Base E27. Luminous flux – 6300 lm. Power 125 W. Color temperature – 4200 K.
	GL with an ellipsoidal flask shape. Used for external and internal lighting. Base E40. Luminous flux – 22000 lm. Power 400 W. Color temperature – 4000 K.
	GL is used for external and internal lighting. Base E40. Luminous flux – 48000 lm, power 400 W. Color temperature – 2000 K.
	GL DNAT, an efficient light source with reduced UV radiation. Power 400 W. Tubular with a one-sided flask-shaped base. Base E40. Color temperature – 2100 K. Luminous efficiency – 120lm/W. Used in closed lamps and for lighting plants. Service life – 20,000 hours.
	Belongs to the line of monochromatic sodium GLNDs. High efficiency up to 183 lm/W. Emits a monochromatic warm yellow light. Designed to illuminate roads with maximum brightness and minimal energy consumption, to illuminate pedestrian crossings instead of fluorescent and mercury light sources. Color temperature – 1800 K, base 775 mm.
	Metal halide high-quality light sources, double-ended. Specially designed for devices that create light fluxes. The lamps are filled with mercury and rare earth elements, which creates a beam of high brightness light with a fairly good color rendering index. Low level of infrared radiation, high luminous efficiency, mechanical strength, excellent light characteristics, color temperature stability, hot restart capability. Power 575 W. Luminous flux 49000 lm. Color temperature - 5600 K, service life - 750 hours.
	Original number D1S.
	Efficient light source, high quality, luminous flux 48000Lm. Color temperature - 2000 K, service life - 24,000 hours. Base E40. Tubular with a one-sided flask-shaped base. Luminous efficiency – 120 lm/W. Power 400 W. It is applied for artificial lighting flower beds, greenhouses, plant nurseries.
	Original number D3S low beam. Used for car lighting.
	Xenon lamp. Power 35 W. Base D2S. Glow temperature 4300 K. Emits light close to daylight. Long service life, turns on without delay, designed for use in a car.
	Xenon diode High Quality with a power of 35 W. Base D1S. Used in cars for low beam headlights.
	High quality xenon lamp with a power of 35 W. Mounted in double headlights.

Scope of application of GL

Characterized by a wide range of applications:

1. street lighting in urban and rural areas, in lanterns for illuminating parks, squares and pedestrian paths;
2. lighting public premises, shops, production facilities, offices, trading floors;
3. as illumination for billboards and outdoor advertising;
4. highly artistic lighting of stages and cinemas using special equipment;
5. for lighting Vehicle(neon);
6. in the lighting of the house.

Spotlight: scope and types

For open spaces, for lighting:

• industrial areas;
• sports complexes and stadiums;
• quarries;
• facades of buildings and various structures;
• monuments;
• memorials;
• entertainment shows;
• livestock complexes.

IMPORTANT! Spotlights are distinguished by the shape of the reflector and the radiation beam.

• asymmetrical;
• symmetrical.

How to check a gas discharge lamp?

Several rules must be followed:

• do not rush to insert a new usable lamp in place of the old one, you must make sure that the choke is not closed, otherwise two spirals will burn out at once;
• First install a diode with intact spirals, but not a working one, in which the gas blinks or glows dimly. If the spirals remain intact, then you can install new light bulb, if they burn out, change the throttle;
• if repairs are necessary, you should start with the starter, which fails more often than other components of the lamp;

  Incandescent lamps

  1. low luminous efficiency;
  2. service life about 1000 hours;
  3. unfavorable spectral complex, distorting light transmission;
  4. endowed with high brightness, but do not provide a uniform distribution of light flux;
  5. The filament should be covered to prevent direct light from entering the eyes and causing harmful effects on them.

  What is the difference between GRL (read above) and LED?

  LED:

  • high energy efficiency;
  • environmentally friendly, do not require special conditions for maintenance and disposal;
  • service life – continuous operation of at least 40-60 thousand hours;
  • the luminous flux is stabilized over the entire supply voltage range from 170-264 V, without changing the illumination parameters;
  • fast ignition;
  • no mercury;
  • absence of starting currents;
  • there is the possibility of main power adjustment;
  • excellent color rendition.

In accordance with new lighting standards, it is recommended to use gas-discharge lamps first of all for lighting installations as they are the most economical.

Rice. 1.5. Current-voltage characteristic of the gas-discharge gap:
1 - quiet discharge; 2 - transition region; 3 - normal glow discharge; 4 - anomalous glow discharge; 5-arc discharge.
The operation of gas-discharge light sources is based on the use of an electric discharge in a gaseous environment and metal vapor. Most often, argon and mercury vapor are used for this. Radiation occurs due to the transition of electrons of mercury atoms from orbit with high content energy into a lower energy orbit. In this case, several types of electrical discharges are possible (for example, quiet, smoldering, arc). An arc discharge has the highest electric current density and, as a result, creates the greatest luminous flux.
Figure 1.5 shows the current-voltage characteristic of an electric discharge in a gas when the current changes from zero to the limit value.
At certain current densities, the nature of the ionization process of the interelectrode gap is avalanche-like. In this case, with increasing current, the resistance of the interelectrode gap sharply decreases, which leads, in turn, to an even greater increase in current and, as a consequence, to an emergency mode. This mode can occur if you connect a gas-discharge light source directly to the network. As the voltage increases from zero to the value (Fig. 1.5), the current gradually increases. A further increase in voltage to the value UT leads to an unstable point at, after which the current increases sharply due to a decrease in the gap resistance during avalanche-like ionization. You can limit this current, and therefore stabilize the operating mode in area 5, by turning on a current-limiting resistance, called ballast, since the power on it is wasted uselessly. The value of the ballast resistance can be determined graphically. To do this, having the current-voltage characteristic of the gas-discharge radiation source, it is necessary to set the operating point A and the value of the network voltage Uc.
Then
(1.17)
Point A is characterized by two types of resistance: static
and dynamic


Rice. 1.6. Changing the position of the operating point when changing the network voltage (a) and ballast resistance (b).
Rice. 1.7. The influence of the Ua/Ue value on the stability of the gas-discharge lamp np and changes in the supply voltage.
The dynamic resistance in the falling section of the ampere characteristic under consideration is negative.
The position of operating point A can be changed either by changing the resistance R (Fig. 1.6,6) or by changing the network voltage Uc (Fig. 1.6, c). In this case, both the static Rlc and the dynamic Rld resistance of the lamp change. It should be noted that the static resistance of the lamp Rld together with the resistance of the ballast determines the operating current at each point, and the dynamic resistance determines the stability of the arc. The stability of the arc is determined from the condition
(1-18)
This condition is met in the section of the current-voltage characteristic to the right of point D. Moreover, the further to the right the operating point is from point D, the more stable the arc burns, since the response of the current to random small changes in the network voltage Uc decreases.
Operation of a gas-discharge lamp at any operating point is possible at different values ​​of the network voltage Uc. To do this, it is necessary to select the ballast resistance so that the operating current remains constant (Fig. 1.7). However, the stability of the lamp will vary. The higher the supply voltage Uc and, accordingly, the ballast resistance Rb, the less the effect voltage deviations have on the lamp current. But it should be remembered that this increases power losses in the ballast resistance. Taking this into account, in practice it is recommended to take the ballast resistance in such a way that the condition is met that allows one to obtain sufficient stability of the operation of gas-discharge lamps with minimal losses in the ballast.
To operate on direct current, active ballasts are used, on alternating current - inductive and capacitive (sometimes active).
All gas-discharge sources according to the operating pressure are divided into low, high and ultra-high pressure lamps.
Low-pressure fluorescent lamps are a glass cylindrical bulb, the inner surface of which is coated with a phosphor. Glass legs are welded into the ends of the flask. Tungsten electrodes in the form of bispirals are mounted on the legs, coated with a layer of oxide (alkaline earth metal oxide), which ensures good electron emission. To protect against bombardment during the anodic period, wire screens are welded to the electrodes. At the ends the flask has caps with pins. The air was evacuated from the lamp bulb and argon was introduced into it at a pressure of about 400 Pa with a small amount of mercury (30-50 mg.).
In fluorescent lamps, light energy arises as a result of double conversion of electric current energy. Firstly, an electric current flowing between the electrodes of the lamp causes an electrical discharge in mercury vapor, accompanied by radiation (electroluminescence). Secondly, the resulting radiant energy, most of which is ultraviolet radiation, acts on the phosphor applied to the walls of the lamp bulb and is converted into light radiation (photoluminescence). Depending on the composition of the phosphor, visible radiation of different spectral composition is obtained. Our industry produces five types of fluorescent lamps: daylight LD, daylight with improved color rendering LDC, cold white light LCB, white light LB and warm white LTB. Bulbs of fluorescent lamps most often have rectilinear, shaped and ring shapes. Fluorescent lamps are available in wattages of 15, 20, 30, 40, 65 and 80 W. IN agriculture Lamps with a power of 40 and 80 W are mainly used (Table 1.3).
Table 1.3
Characteristics of fluorescent lamps used in agriculture

Currently, new lamps with improved color rendering of the LE type are being produced.
Compared to incandescent lamps, fluorescent lamps have a more favorable spectral composition of radiation, greater luminous efficiency (60 ... 70 lm-W-1) and a longer service life (10,000 hours).
In addition, special low-pressure lamps are used in agriculture: phytolamps for growing plants, erythemal lamps for UV irradiation of animals and birds, bactericidal lamps for disinfection installations. Erythemic and phytolamps have a special phosphor, bactericidal lamps do not have a phosphor (Table 1.4)
All low-pressure fluorescent lamps are connected to the network through a ballast resistor.

Characteristics of erythema, bactericidal and phytolamps

It should be remembered that fluorescent lamps are ignited without special measures at voltage U3, which is usually greater than the mains voltage Uc. One way to reduce the U3 ignition voltage is to preheat the electrodes, which facilitates the emission of electrons. This heating can be carried out using starter and non-starter circuits (Fig. 1.8).

Rice. 1.8. Low pressure fluorescent lamp connection diagram:
1 - mains voltage terminal; 2 - throttle; 3, 5 - lamp electrodes; 4 - tube; 6, 7 - starter electrodes; 8 - starter.
The starter is a miniature neon lamp, one or both electrodes of which are made of bimetal. When heated, these electrodes can close together. In the initial state they are open. When voltage is applied to terminals 1, all of it is practically applied to the starter terminals 6 and 7 and a glow discharge occurs in its bulb 8. Due to the current flowing in this case, heat is released, which heats the movable bimetallic contact 7, and it closes with the fixed contact 6. The current in the circuit in this case increases sharply. Its value is sufficient to heat the electrodes 5 and 5 of the fluorescent lamp, made in the form of spirals. In 1...2 s, the lamp electrodes heat up to 800...900°C. Since there is no discharge in the starter flask at this time, its electrodes cool down and open.
At the moment the circuit breaks in throttle 2, e.g. d.s. self-induction, the value of which is proportional to the inductance of the inductor and the rate of change of current at the moment the circuit breaks. Formed due to e. d.s. self-induction, an increased voltage (700... 1000 V) is applied to the electrodes of the lamp, prepared for ignition. An arc discharge occurs between the electrodes, and lamp 4 begins to glow. In this mode, the resistance of the lamp turns out to be approximately the same as the resistance of the series-connected choke and the voltage on it drops to approximately half the mains voltage. The same voltage is applied to the starter connected in parallel with the lamp, but the starter no longer ignites, because its ignition voltage is set within

Thus, the starter and throttle perform important functions during the ignition and operation process. The starter: 1) closes the “spiral of electrodes - choke” circuit, the current flowing in this case heats the electrodes, facilitating ignition of the lamp due to thermionic emission; 2) breaks after heating the lamp electrodes electrical circuit and thereby causes a pulse of increased voltage on the lamp, providing breakdown of the gas gap.
The choke: 1) limits the current when the starter electrodes close; 2) generates a voltage pulse to break down the lamp due to e. d.s. self-induction at the moment of opening the starter electrodes; 3) stabilizes the arc after ignition.
Since the starter is the most unreliable element in the ignition circuit, starterless circuits have also been developed. In this case, preheating of the electrodes is carried out from a special filament transformer.
For low-pressure fluorescent lamps, special ballasts (ballasts) are produced.
Starter ballasts are designated 1UBI, 1UBE, 1UBK (the number indicates the number of lamps operating from one ballast, U - starter, B - ballast, I - inductive, E - capacitive; K - compensated, i.e. increasing the power factor of the lighting installation to 0.9...0.95). For two lamps, respectively, 2UBI, 2UBE, 2UBK.
Starterless devices have the letter A in their designation: ABI, ABE, ABK. For example, the brand PRA 2ABK-80/220-ANP stands for: two-lamp starterless device, compensated, power of each lamp 80 W, mains voltage 220 V, anti-stroboscopic (A), for independent installation (N), with reduced noise level (P) .
One of the disadvantages of gas-discharge lamps is the pulsation of the light flux, which causes a stroboscopic effect - the flickering of a fast moving object. To reduce the pulsation of the light flux, it is recommended to turn on the lamps at different phases or use special anti-stroboscopic ballasts.

Rice. 1 9. DRT lamp (a) and its connection diagram (b):
1 - quartz glass tube; 2 - electrode; 3 - clamp with holder; 4 - conductive strip.
Rice. 1.10 Four-electrode lamp DR-S (a) and its connection circuit (b):
1 - mercury-quartz burner; 2 - flask; 3 - phosphor; 4 - igniting electrodes; 5 - main electrodes; 6 - current-limiting resistors.
When fluorescent lamps are switched on at a higher frequency voltage, their luminous output increases, the size of the ballast and losses in it decrease, and the pulsation of the light flux decreases.
High pressure gas discharge lamps. The most common lamps in agricultural production are DRT lamps - arc, mercury, tubular and DRL - arc, mercury, fluorescent.
The DRT lamp is a straight tube 1 made of quartz glass (Fig. 1.9a), into the ends of which electrodes 2 are soldered. The tube is filled with argon and a small amount of mercury. Since quartz glass transmits UV radiation well, the lamp is mainly used for UV irradiation of animals and poultry and for the disinfection of water, food, air, etc.
The lamp is connected to the network through a choke (Fig. 1.9.6). Ignition is carried out by briefly pressing the S button. In this case, current flows through the inductor L and capacitor C1. When the button is opened, the current decreases sharply and due to e. d.s. The self-induction of the choke sharply increases the voltage on the electrodes of the lamp, which promotes its ignition. The metal strip I, connected through capacitor C2, ensures redistribution of the electric field inside the lamp, which facilitates ignition of the lamp.
DRL lamps are used for lighting. They can be either two- or four-electrode. Currently, only four-electrode lamps are produced, the design and connection diagram of which are shown in Figure 1.10. Mercury-quartz burner I is a source of UV radiation. The flask 2 is made of heat-resistant glass and is coated on the inside with phosphor 3, which converts the UV radiation of the burner into light. To facilitate ignition, the four-electrode lamp has ignition electrodes 4. The discharge occurs first between the ignition and main electrodes 5, and then between the main electrodes (working gap).
High-pressure metal halide lamps of the DRI type are promising for lighting. Sodium, thallium and indium iodides are added to the bulbs of these lamps, which makes it possible to increase the light output by 1.5...2 times compared to DRL lamps.
For use in greenhouses based on the DRL lamp, special phytolamps such as DRF and DRLF have been developed. The bulb of these lamps is made of glass that can withstand splashes of cold water when heated and is coated with a special phosphor that has increased phyto-return. A reflective layer is applied to the top of the bulb.

Areas of use

Due to the line spectrum of radiation, gas-discharge lamps were initially used only in special cases when obtaining a given spectral composition of radiation was a factor more important than the value of luminous efficiency. A wide range of lamps has emerged, intended for use in research equipment, which are united under one general name - spectral lamps.

Figure 1. Spectral lamps with sodium and magnesium vapor

The possibility of creating intense ultraviolet radiation, characterized by high chemical activity and biological effects, has led to the use of gas-discharge lamps in the chemical and printing industries, as well as in medicine.

A short arc in gas or metal vapor at ultra-high pressure is characterized by high brightness, which has now made it possible to abandon the open carbon arc in searchlight technology.

The use of phosphors, which made it possible to obtain gas-discharge lamps with a continuous emission spectrum in the visible region, determined the possibility of introducing gas-discharge lamps into lighting installations and displacing incandescent lamps from a number of areas.

The features of isothermal plasma, which provides a radiation spectrum close to that of thermal sources at temperatures inaccessible in incandescent lamps, have led to the development of heavy-duty lighting lamps with a spectrum almost identical to that of the sun.

The practical inertia-free nature of a gas discharge has made it possible to use gas-discharge lamps in phototelegraphy and computer technology, as well as to create flash lamps that concentrate enormous light energy in a short-term light pulse.

Video 1. Flash tubes

The requirements for reducing energy consumption in all areas of the national economy are expanding the use of economical gas-discharge lamps, the production volume of which is constantly growing.

Glow lamps

As is known, a normal glow discharge occurs at low current densities. If the distance between the cathode and the anode is so small that the discharge column cannot be accommodated within it, then cathode glow and negative glow occur, covering the surface of the cathode. The power consumption in a glow discharge lamp is very small, since the current is low, and the voltage is determined only by the cathode drop. The luminous flux emitted by the lamp is insignificant, but it is absolutely sufficient for the ignition of the lamp to be noticeable, especially if the discharge occurs in a gas that produces colored radiation, for example, neon (wavelength 600 nm, red color of radiation). Such lamps of various designs are widely used as indicators. So-called digital lamps were previously an integral part of many automatic devices with digital indicators.

Figure 3. Glow lamp designed to display numbers

With a long gas-discharge gap with a distance between the electrodes significantly greater than the near-cathode region, the main radiation of the discharge is concentrated in the discharge column, which in a glow discharge differs from the column in an arc discharge only in its lower current density. The radiation of such a column can have high luminous efficiency over a long length. The high value of the cathode voltage drop in a glow discharge led to the development of lamps for high supply voltages, that is, the voltage on them significantly exceeds the voltage considered safe under working conditions in enclosed spaces, especially domestic ones. However, such lamps are successfully used for various kinds of advertising and signaling installations.

Figure 4. Lamps with a long glow column

The advantage of a glow discharge lamp is the simplicity of the cathode design compared to the cathode of an arc discharge lamp. In addition, the glow discharge is less sensitive to the presence of random impurities in the gas-discharge space, and therefore more durable.

Arc lamps

Arc discharge is used in almost all gas-discharge lamps. This is due to the fact that during an arc discharge the cathode voltage drop weakens and its role in the lamp energy balance decreases. Arc lamps can be manufactured for operating voltages equal to the voltages of electrical networks. At low and medium arc discharge current densities, as well as at low pressure in the lamp, the source of radiation is mainly the positive column, and the glow of the cathode has practically no significance. By increasing the pressure of gas or metal vapor filling the burner, the cathode region gradually decreases, and at significant pressures (more than 3 × 10 4 Pa) it practically does not remain at all. By increasing the pressure in the lamps, high radiation parameters are achieved at small distances between the electrodes. High light output values ​​at very short distances can be obtained at ultra-high pressures (more than 10 6 Pa). With increasing pressure and decreasing distance between the electrodes, the current density and brightness of the discharge cord greatly increases.

With an increase in pressure and current density, an isothermal plasma is formed, the radiation of which mainly consists of non-resonant spectral lines that arise when an electron in an atom passes to lower, but not fundamental, levels.

Arc discharge is used in a wide variety of gases and metal vapors from the lowest pressures to ultra-high ones. In this regard, the designs of arc lamp bulbs are extremely diverse both in shape and in the type of material used. For ultra-high-pressure lamps, the strength of the bulbs at high temperatures is of great importance, which led to the development of appropriate methods for their calculation and study of parameters.

After the appearance of the arc discharge, the bulk of the electrons are knocked out of the cathode spot. The luminous cathode part of the discharge begins with a cathode spot, which is a small luminous point on the spiral. There are several cathode spots. In self-heating cathodes, the cathode spot occupies a small part of its surface, moving along it as the oxide evaporates. If the current density is high, local thermal overloads occur on the cathode material. Due to such overloads, it is necessary to use cathodes of special complex designs. The number of cathode designs is varied, but they can all be divided into low pressure, high pressure and ultra high pressure lamp cathodes.

Figure 5. Low Pressure Tubular Discharge Lamp

Figure 6. High pressure discharge lamp

Figure 7. Ultra-high pressure discharge lamp

The variety of materials used for arc lamp flasks and large current values ​​require solving the issue of creating special bushings. You can read in detail about the designs of gas-discharge lamps in specialized literature.

Lamp classification

Similar to incandescent lamps, gas-discharge lamps differ in their area of ​​application, type of discharge, pressure and type of filling gas or metal vapor, and the use of phosphor. If you look through the eyes of gas-discharge lamp manufacturers, they may also differ in design features, the most important of which are the shape and dimensions of the bulb (gas-discharge gap), the material used from which the bulb is made, the material and design of the electrodes, the design of the caps and terminals.

When classifying gas-discharge lamps, some difficulties may arise due to the variety of characteristics on the basis of which they can be classified. In this regard, for the classification of the currently accepted and used as the basis for the designation system for gas-discharge lamps, a limited number of characteristics have been defined. It is worth noting that low-pressure mercury tubes, which are the most common gas-discharge lamps, have their own designation system.

So, to designate gas-discharge lamps, the following main features are used:

1. operating pressure (ultra-high pressure lamps - more than 10 6 Pa, high pressure - from 3 × 10 4 to 10 6 Pa and low pressure - from 0.1 to 10 4 Pa);
2. composition of the filler in which the discharge occurs (gas, metal vapors and their compounds);
3. name of the gas or metal vapor used (xenon - X, sodium - Na, mercury - P and the like);
4. type of discharge (pulse - I, glow - T, arc - D).

The shape of the flask is indicated by letters: T – tubular, Ш – spherical; if a phosphor is applied to the lamp bulb, then the letter L is added to the designation. Lamps are also divided according to: area of ​​luminescence - glow lamps and lamps with a discharge column; according to the cooling method - lamps with forced and natural air cooling, lamps with water cooling.

Low-pressure mercury tube fluorescent lamps are usually designated more simply. For example, in their designation, the first letter L indicates that the lamp belongs to a given type of light source, the subsequent letters - and there may be one, two or even three of them - indicate the color of the radiation. Color is the most important designation parameter, since color determines the area of ​​use of the lamp.

The classification of gas-discharge lamps can also be carried out according to their significance in the field of lighting technology: high-pressure arc lamps with corrected color; high pressure tube arc lamps; high pressure arc; low and high pressure sodium arc lamps; high pressure arc; ultra-high pressure arc balls; xenon arc tube and ball lamps; low pressure fluorescent lamps; electrode-lighting, pulsed and other types of special gas-discharge lamps.

Electrical devices consisting of a transparent container in which gas is powered by voltage, causing the glow process to occur, are called gas discharge lamps. We propose to consider the differences between high-pressure gas-discharge lamps and incandescent lamps, how this device works and where to buy them.

Operating principle of a gas discharge lamp

A discharge lamp is a glow source that generates light by creating an electrical discharge through ionized gas. Typically, these lamps use gases such as:

• argon,
• neon,
• krypton,
• xenon, as well as mixtures of these gases.

Many lamps are filled with additional gases such as sodium and mercury, while others use metal halide additives.

When power is applied to the lamp, an electric field is generated in the tube. This field forms inclusions of free electrons in the ionized gas, i.e. ensures the collision of electrons with gas and metal atoms. Some electrons orbiting these atoms provide collisions into a higher energy state. In such cases, photon energy is released. This light can be anything from infrared visible to ultraviolet radiation. Some lamps have a fluorescent coating on the inside flasks for converting ultraviolet radiation into visible light.

Some tube-shaped lamps contain a special source of beta radiation to ensure ionization of the gas inside. In these tubes, the glow discharge provided by the cathode is minimized, in favor of the so-called positive energy column. Most shining example Such technologies include energy-saving neon lamps, gas-discharge pulsed IFC and fluorescent lamps.

Gas discharge lamps and types of cathodes

Many people have heard the term CCFL cold cathode fluorescent lamps and hot cathode lighting fixtures. But what is the difference, what is their labeling and which ones to choose?

Hot cathode

Hot cathodes generate electrons from the thermionic emission electrode itself. That is why they are also called thermionic cathodes. The cathode is usually an electrical filament made of tungsten or tantalum. But now they are also coated with a layer of emissive material, which can produce less heat and light, thereby increasing the efficiency and lumen output of the discharge lamp. In some cases where AC buzzing is a problem, the heater is electrically isolated from the cathode. This method is widely used by gas-discharge metal halide lamps (hpi-t plus, deluxe, hid-8) and low-pressure lamps.

Hot cathode light sources produce significantly large quantity electrons than cold cathodes with the same surface area. They are used by indicator devices, microscopes, and even such lamps are used to modernize electron guns.

Cold cathode

With a cold cathode there is no thermionic emission. High-voltage lamps in this case operate on electrodes that generate a strong electric field (for example, make brand), which ionizes the gas. The surface inside the tube is capable of producing secondary electrons, and at the same time reducing their “drop” to a minimum. Some pipes contain special grounding that improves electron emission.

Another method of operation of cold light devices is based on the generation of free electrons without thermionic emission, due to field electron emission. Field emission occurs at electric fields, which create very high voltage. This method is used in some X-ray tubes, microscopes operating by electric fields, and it is also used in gas-discharge sodium lamps (lhp, dnat 400 5, dnat 70, dnat 250-5, dnat-70, hb4).

The term "cold cathode" does not mean that it remains at ambient temperature all the time. The operating temperature of the cathode may increase in some cases. For example, when using alternating current, due to which the electrodes swapped places - the cathode became the anode. Some electrons can also cause localized heat. For example, fluorescent lamps: after starting, the tungsten wire is cold, the lamp operates with a cold cathode, and the phenomenon described above is used to heat the filament. When it has reached the desired level of light, the lamp operates normally, as with a hot cathode. A similar phenomenon can be demonstrated by some DRL gas-discharge xenon bulbs (d2s, h4 category d).

The cold cathode of the device requires high voltage, but a high-voltage power supply is not required. This phenomenon is often called CCL inverter. The inverter's job is to create a high voltage to create the initial space charge and the first electric arc of current in the tube. When this happens internal resistance tube decreases and increases the current. The converter reacts to such differences, and if the temperature exceeds the norm, it turns off. Most often, such systems are installed for street lighting.

Cold radiation lamps are often found in electronic devices. CCFLs (cold cathode fluorescent lamps) are used as diode light bulbs for computers, modems, multimeters, gas-discharge indicators in-14, in 18 and nv 3, and other things. In addition, they are widely used as LCD backlight. Another example of widespread use is Nixie pipes.

Types of gas discharge lamps

Before you buy any device, you should definitely study all its characteristics.

High Pressure Discharge Lamps

Low pressure lamps

These lamps contain gas inside the tube at a lower pressure than atmospheric pressure. Classic way fluorescent lamps belong to this category, the now well-known neon lamps, as well as low-pressure sodium lamps, which are used for street lighting. They all have very good efficiency, but the most effective among all gas-discharge lamps are son sodium lamps. The problem with this type of lamp (r7s base) is that it only produces an almost monochromatic yellow light (the exception is chokeless fluorescent lamps).

High-intensity discharge lamps

In this category, there are lamps that emit light using an electric arc between electrodes (e-27). The electrodes are usually tungsten electrodes, which are located inside a translucent or transparent material. There are many various examples HID (High Intensity) lamps, which are sold in our country, such as halogen (ipf h4 x-41, mn-kh7s-150w, hq-t), xenon arc, and ultra-high performance (UHP) lamps.

Disadvantages of discharge lamps

Any device has its drawbacks, and gas-discharge lamps are no exception:

• if the network voltage is less than 220 V (let's say 100), then metal halide lamps (hmi-1200) will not work;
• prohibition of use in educational institutions;
• Halogen lamps become too hot during operation. They pose a certain fire hazard, and in addition require very careful care - 1 drop of fat on the surface can cause it to explode;
• neon lamps emit light (especially if the UV series, model n4), which is harmful to the eyes with prolonged contact.

Application area

Automotive high-intensity gas-discharge lamps, including neon ones, are widely used; diode lighting is also sometimes used for cars (their price is slightly lower). The discharge of a car headlight is filled with a mixture of xenon gas and metal halide salts (as for example used by Toyota Corolla - d2r for Toyota Estima 2000, or BMW 5, for Opel Astra J)). Light is created by striking an arc between two electrodes. The lamp has a built-in igniter.

For lighting industrial premises (gu-23a, ld30, tn-0, 3, gu26a), street areas (olympiad 250, Silviana made in Ukraine), billboards, building facades, also high-pressure discharge lamps for daylight in apartments and houses (GOST 500 -9006-083) and in the control gear.

Installation and connection diagram are exactly the same as during installation simple lamps incandescent