In our age of widespread electrification, we are accustomed to considering an electric discharge as something wrong and, in some cases, even dangerous. Therefore, many people see a certain paradox in the words “gas-discharge lamp”.
Electricity has long ceased to be a curiosity. It surrounds us literally on all sides. There is wiring in the walls of houses and apartments through which electric current continuously flows, even if the TV is not turned on and all the light bulbs are turned off. The refrigerator still turns on quietly all the time and stores food for us, powered by the mains. The same goes for other devices: LEDs on switches - even if only a little bit, they transmit current. But the discharge in our networks is something extraordinary. If two wires in one socket are accidentally shorted, there will be a short circuit, that is, a discharge. And this is an accident and an instant shutdown of the network by protective automation. Or if we ourselves are charged, simply from the friction of clothing, then as soon as we touch something metal, there will be a discharge: a slight, but sensitive prick or even shake. But usually once. Well, a charged capacitor can give an electric shock, that is, discharge through us.
There are quite a lot of types of discharges. Most often we encounter a spark discharge, which is precisely what we don’t like. Although we know that in a car it makes the engine work.
Types of electrical discharges
From left to right: spark, arc, corona, smoldering. There are also exotic species - partial and Townsend (dark - not here).
We use some of them, we are just trying to put some of them into service, and we are struggling with some of them.
But the glow discharge, perhaps, is called so “softly” in order to convey: yes, this is a discharge, but not so terrible. Indeed, it does not strike, like a spark or lightning, in a split second and then stop immediately. It smolders, that is, it flows like an ordinary and familiar electric current to us all. And it not only flows, but also shines - these are all electric lamps where gas glows, not metal wire. These are gas discharge lamps.
The most interesting thing in this whole story is that they discovered the glow of gas under the influence of a discharge even before “real” electrical devices appeared. That is, devices in which electrical energy is guaranteed to work.
At first, the glow of the gas was shown as a focus. And the source of energy was not generators or batteries, but the electrification of objects through various tricks, which made it possible to cause some charge on the surface. Electrification has been known for a long time, they just tried to somehow strengthen it, in accordance with their understanding. For example, a large ball of sulfur mounted on a metal rod was twisted by hand, and “electricity” was obtained in quite a large amount, which made itself known by sparking or glowing gas. There were other experiments that were usually carried out from the stage for the public or in fashionable secular salons for a select society. They studied and demonstrated “animal magnetism,” alchemical transformations that were rooted in “hermeneutic philosophy.”
Accordingly, the collection of electricity for demonstration purposes could take place not on some kind of industrial equipment, but on things that rather belonged to the category of theatrical props.
However, a good thing came from such experiments: people saw not just a physical - that is, not a magical - phenomenon, but understood that it contained a certain power accessible to people, which could be accumulated and measured.
And since then, further study of electricity has gone in the direction of its domestication and widespread use of humanity for the benefit.
Many researchers of those times received a mysterious glow. For example, Lomonosov discovered a glow in a glass vessel of hydrogen gas. And not all of these glows were what is now called a “glow discharge.” The fact is that gas is able to receive energy in different ways, and then emit this energy in the form of light of a certain wavelength. This can be an external electrical voltage applied to two electrodes installed in a vessel with gas. At a certain voltage, as well as at a certain rarefaction of the gas, a flow of electrons will rush from the electrode with an excess of electrons to the electrode with an insufficient number of them. And, “bumping into gas atoms along the way,” the electrons activate them, and this results in a glow discharge.
But something similar can happen not only from a flow of running electrons. And, for example, directly from the influence of an external magnetic field. There will be a glow discharge, very similar to the aurora. I myself have seen this on fluorescent lamps that were disconnected from the power supply, but which were affected by a magnetic field from rotating magnetic drums. On older computers, sometimes there were such devices as large as a cabinet. It was in the darkness near such cabinets that fluorescent lamps produced interesting light patterns, similar to the Northern Lights.
The color of gas discharge lamps does not depend on the energy source. The gas usually consists of a homogeneous mass of simple molecules of one or two atoms (H2 - hydrogen, Ar - argon) and works as one atomic mechanism. In it, electrons, receiving energy from an external source, jump to another level - to an “excited” state, and then return back, throwing out their “excited” energy in the form of a light quantum of strictly defined wavelengths. This is how you get glows of the same color, monochrome. Or several colors corresponding to energy transitions of electrons in the electron shells of gas atoms. In this way, it is possible to obtain lamps that glow in specific colors, unlike the sun with its continuous spectrum or the flame of a fire, candle or incandescent light.
Energy processes are very simple and therefore very effective and have high efficiency. That is, an incandescent lamp produces a whole spectrum, which is obtained from the chaotic thermal movement of the molecules of a solid tungsten spiral. Molecules of hot tungsten rush like crazy around their places in the crystal lattice and frantically emit light quanta of all conceivable energies and frequencies in all possible directions. In this spectrum there is light that we can see, and there is infrared radiation that we cannot see. And there is also simply convection - the transfer of heat energy directly to the molecules of the gaseous medium of the lamp. This heats up the glass cylinder, which, in turn, heats the air in the room, the base, the socket, the wires... It turns out that only 5–10% of the energy goes into light from the incandescent lamp. Whereas gas light gives, according to various estimates, from 25 to 40%.
Types of gas discharge lamps
Gas-discharge lamps are a glass (made of glass of a special composition) cylinder, inflated with gas and with electrodes installed inside. Electrical voltage is supplied to it through the base. The gas inside may be at low pressure or high pressure. On this basis, low-pressure gas-discharge lamps, high-pressure lamps and ultra-high-pressure lamps are distinguished. The remaining differences relate mainly to the composition of the gas media inside the cylinder and the coating of the cylinder. The glow characteristics of the lamps depend on this.
Another important design feature of lamps (including gas-discharge lamps) is the design and size of the base, which determines the design of the lamp socket, and therefore the possibility of installing such lamps in lamps.
A, b – low pressure;
c, d – high pressure;
g – ultra-high pressure
a – sodium, b – luminescent, c – mercury, d – xenon, e – sodium
(with a special coating of the flask - polycrystalline aluminum oxide)
The inert gases with which the lamps are filled are capable of glowing with the colors of their own banded emission spectrum. The result is a colored glow, which advertisers immediately fell in love with, and they began to use it to make spectacular colorful inscriptions. Different inert gases give off different colors of glow.
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For ordinary lighting purposes, lamps containing a mixture of gases or a mixture of gases and metal vapors - mercury or sodium in particular - are usually used.
Gas light may contain ultraviolet components, in which case you can:
- use such lamps specifically as ultraviolet sources;
- change the radiation spectrum by another means: by spraying a special coating on the inside of the cylinder, which absorbs gas radiation and re-emits it with light that is more acceptable for consumption.
Such substances are called phosphors, and lamps are called phosphor or fluorescent.
Gas-light energy-saving lamps are also a type of fluorescent lamps that are now widely used.
Application
Energy-saving lamps come in different shades of color, but such that the human eye perceives it as natural as possible. At the same time, the shades of color or light temperature vary: from warmer to close to daytime white. Energy-saving lamps are produced in luminosity gradations in approximately the same way as is done with incandescent lamps; this system has developed over the years. Small incandescent lamps - 25 watts (table), larger ones - 60, 75 watts (chandeliers, floor lamps), 100-120 watts (halls, large rooms) and so on. Energy-saving lamps are produced similarly in terms of luminosity, although their power consumption is reduced by 2–4 times due to their higher efficiency. Another consequence of this is that they hardly get warm. And this also has many advantages: cartridges do not heat up, plastic lampshades do not melt, and so on
Other lamps provide strong directional light: for example, xenon lamps are used in floodlights and car headlights.
There are lamps of a color that is not very good for human eyes, but is effective when illuminating plants. These are sodium lamps of various wattages. They give a bright yellow glow, they make plants grow well, so they are used in greenhouses.
An energy-saving lamp is a lighting device that is more efficient than a conventional light bulb with an incandescent filament. Today, several types of devices fall under the definition. Let's talk about discharge and LED lamps and their varieties.
Energy saving concept for electric lamps
Note that the high light output of some types of lamps has been known for a long time. Since the advent of low-pressure mercury lamps with acceptable color rendering in 1938, it has become clear that the latter class of devices is the future. But now, when the first LED devices have come out, the competitiveness of relatively dim and complex discharge lamps is already being called into question. However, European standards divide equipment not on the basis of the technologies invested in it, but on the basis of energy saving.
The issue is addressed by Regulation No. 874/2012, issued on 12 July 2012, in support of Directive 2010/30/EU of the European Parliament. The document provides information about lamps that is useful or interesting to readers:
- The document applies to all types of household lamps: filament, fluorescent, discharge, LED. The last three groups are also considered energy saving.
- For each light bulb, the degree of energy efficiency is indicated with a colored sticker, like those shown in the photo. This part allows you to quickly understand what kind of light bulb it is and whether it is considered energy-saving.
The energy efficiency factor differs for directional and non-directional light sources. For example, the rules of the European Union provide buyers with information presented in the form of a table on a screenshot. From the above figures it is clear that the index of energy efficiency (IEE) for directional light sources can be higher and significantly greater than one. Devices of class A++ are recognized as the best, and class E as the least efficient. In everyday life, it is customary to call energy-saving lamps for which the parameter falls within the range of A and above.
Let's find out how the energy efficiency index is calculated. During the calculations, the real luminous flux of the light source is compared with the ideal one: I I E = Pcor / Pref. Where Pcor is the rated power consumption, which for devices with external drivers should be adjusted according to the data in the table presented in the figure. For other devices, the number is taken directly, without changes.
We remind you that a lamp driver is a module for converting the mains voltage to the desired format. For example, inside the E27 base there is often a switching power supply chip. This is a driver, and an internal one. Pref is a certain consumption of a standard, a kind of ideal lamp. It is calculated using the formulas presented in the figure, depending on whether the luminous flux is greater than 1300 lumens or less.
Don’t be afraid of complex expressions; the authors have edited the screenshots and provided relevant explanations. You will see that the rated power of the standard is calculated from the luminous flux of the experimental lamp using simple formulas. The table shows three options:
- Non-directional light sources.
- With a cone angle of 90 degrees or more, except for those bearing warning symbols on the packaging indicating the impossibility of use in the accent mode and with filaments.
- All other directional lamps.
The question is how to measure the luminous flux. Firstly, energy-saving lamps are often supplied with packaging in which a specific number is written, and secondly, with the help of instruments, the value is obtained in laboratory conditions. Energy efficiency is determined by test results; no difficulties arise. Actually, all the information in English is easy to read from screenshots. We translated it into Russian for better understanding.
Lamps classified as energy-saving
Today, two large classes of lamps fall under the definition of energy-saving lamps:
- LED.
- Bit.
LED energy saving lamps
By all indications, the energy-saving LED lamp will soon supplant other varieties. Judge for yourself: the efficiency is usually higher than A, the service life is in the range of luminescent devices. Typical values are from 20 to 50 thousand hours. It is easy to distinguish an LED model from others by two characteristics:
- An energy efficiency sticker will help distinguish pear-shaped models from filament lamps.
- Based on the shape of the bulb, it is easy to differentiate from fluorescent lamps, which are also considered energy-saving.
The lifespan of an incandescent light bulb is 1000 hours. If you look closely, on the pack (see photo) you will see an identity where one LED is equal to thirty regular ones. Here we mean a lifespan of 30,000 hours. This is enough for 10 years of intensive work. Moreover, this is far from the main reason for the popularity of LED light bulbs. The latter consume up to 10 times less electrical energy for the same total light flux in the visible range. A lot is saved due to the lack of heating. As a result, the infrared spectrum is noticeably poorer, however, humans do not need it.
It cannot be said that LED bulbs are much better than fluorescent ones, but with the same luminosity indicated on the packaging, the former create a visually more favorable impression. The difference is visible to the naked eye. The cost reduction is noticeable after the first month of operation. After the introduction of LED light bulbs into everyday use, the refrigerator becomes the main enemy of the family budget, followed by economical personal computers. Draw conclusions: when you buy a dozen LED light bulbs at a price of 180 rubles apiece, you save the price of one every month.
After about a year, in the case described above, it is already appropriate to talk about the return of funds invested in the illumination of the home. The most important thing is that you can forget about the issue of saving light and calmly turn on the light when necessary. Let's mention other advantages: the requirements for wiring and switches become much more lenient. Currents are reduced by 10 times, the copper cross-section can be reduced to a minimum, this is a direct increase to the budget for the next repair. It is permissible to purchase chandeliers that are less resistant to heat; these bulbs do not heat up to a fire hazard temperature. Emergencies do not count.
The authors tend to attribute the difficulty of repair to the only disadvantage of LED lamps. It is extremely difficult to get to the driver; as a result, it is impossible to repair the device. For fluorescent lamps, the base is simply removed, which increases the chances of bringing the product back to life.
The family includes all lamps where the glow is formed due to a slowly glowing discharge. The first successful version is probably considered to be Giesler pipes, which were used back in the 19th century in European entertainment establishments. This fact was mentioned earlier in the review about fluorescent lamps, today we will focus on the more practical part. At the turn of the 20th and 21st centuries, up to 80% of the luminous flux in developed countries came from discharge type devices. The service life is also quite long - from 10 to 50 thousand hours.
At the beginning of the development of the direction, it became clear that high-pressure mercury lamps and low-pressure sodium lamps were extremely good, but they did not dare to use them for domestic needs: color rendition was too poor. Human skin simply looked scary in such a neighborhood. Let us recall that the color rendering of an optical source is the degree of similarity of the various color shades illuminated by it to the true position on the spectral scale. By the way, LED lamps give amazing results.
For discharge lamps, the first acceptable effect was obtained with fluorescent fluorescent lamps (low pressure mercury). They appeared in 1938, and it became clear that the devices would gradually conquer the household segment. In the 50s of the 20th century, high-pressure mercury lamps (arc HRL) appeared. Then came high-intensity discharge lamps, where for the first time it was possible to overcome the efficiency of 100 lm/W. This greatly increased the attractiveness of the devices for the average person. The radiation spectrum is selected by filling the flask (gas, steam, mixtures thereof) or by arc burning conditions.
Fluorescent discharge lamps have become widespread, where the spectrum is obtained by irradiating a special substance (phosphor) with ultraviolet light. There was also considerable confusion. For example, halogen lamps are often classified as discharge lamps. But this is not always correct. For example, quartz heaters use filaments; there is no arc. But metal halides serve other purposes: tungsten evaporating from the spiral immediately enters into a compound that does not precipitate on the glass flask. As a result of the return of the molecule to the surface of the hot thread (due to random processes), the metal is restored. This significantly increases the service life.
Halides are also often used in discharge lamps. And for similar purposes. The key feature of metal halide discharge lamps (which appeared in the 60s of the 20th century) is a burning arc. In the latter case, halides (iodine, bromine, chlorine) play an additional role: they change the luminescence spectrum and create the required density of metals in the volume of gases and vapors. As a result, unique properties of light sources arise that are impossible under other conditions. A third property is known, which is not so obvious: certain metals with an attractive emission spectrum behave aggressively when a quartz flask is heated to 300 degrees Celsius. First of all, alkaline, cadmium, zinc. At the same time, their halides are much more inert, and destruction of the quartz flask no longer occurs.
A particularly remarkable effect is observed when mixing several types of substances. For example, metals of groups I and III of the periodic table give separate spectral bands in the range:
- Sodium – 589 nm (close to orange).
- Thallium – 535 nm (green).
- Indium – 410 and 435 nm (intense violet).
Scandium, lanthanum, yttrium and rare earth metals produce a spectrum of many bands that fill the visible spectrum. Some readers ask – why is this actually necessary? The point here is not only in the varied color rendition. The color temperature of the light bulb is important. In the photo, for example, there is a 4500 K LED. This is a cool shade, but it is far from daylight. The milestone starts at 6000 K.
By choosing the right color temperature, it is possible to set the circadian rhythms of the human psyche. The phenomenon means improved performance during the day, good sleep at night, calming or increasing tension. Below, the authors have provided a table showing color rendering indices and other parameters for metal halide lamps with different fillings. The DRI coding (and other similar ones) will help you quickly find a similar product on the counter.
Later we will talk about sodium lamps and ceramic burners, color rendering indices and the effect of temperature on the psyche. Any knowledge is limited, and only ignorance has no boundaries.
Fluorescent lamps are low-pressure gas-discharge lamps in which, as a result of a gas discharge, ultraviolet radiation invisible to the human eye is converted by a phosphor coating into visible light.
Fluorescent lamps are a cylindrical tube with electrodes into which mercury vapor is pumped. Under the influence of an electrical discharge, mercury vapor emits ultraviolet rays, which, in turn, cause the phosphor deposited on the walls of the tube to emit visible light.
Fluorescent lamps provide soft, uniform light, but the distribution of light in space is difficult to control due to the large surface area of the radiation. The shapes include linear, ring, U-shaped, and compact fluorescent lamps. Tubing diameter is often specified in eighths of an inch (for example, T5 = 5/8"" = 15.87 mm). In lamp catalogs, the diameter is mainly indicated in millimeters, for example, 16 mm for T5 lamps. Most lamps are of international standard. The industry produces about 100 different standard sizes of general purpose fluorescent lamps. The most common lamps are with a power of 15, 20,30 W for a voltage of 127 V and 40,80,125 W for a voltage of 220 V. The average lamp burning time is 10,000 hours.
The physical characteristics of fluorescent lamps depend on the ambient temperature. This is due to the characteristic temperature regime of mercury vapor pressure in the lamp. At low temperatures the pressure is low, which means that there are too few atoms that can participate in the radiation process. If the temperature is too high, the high vapor pressure leads to increasing self-absorption of the produced ultraviolet radiation. At a flask wall temperature of approx. 40°C lamps reach the maximum voltage of the inductive component of the spark discharge and thus the highest luminous efficiency.
Advantages of fluorescent lamps:
1. High luminous efficiency reaching 75 lm/W
2. Long service life, reaching up to 10,000 hours for standard lamps.
3. The ability to have light sources of different spectral composition with better color rendering for most types than incandescent lamps
4. Relatively low (albeit creating glare) brightness, which in some cases is an advantage
The main disadvantages of fluorescent lamps:
1. Limited unit power and large dimensions for a given power
2. Relative difficulty of inclusion
3. Inability to power lamps with direct current
4. Dependence of characteristics on ambient temperature. For conventional fluorescent lampsthe optimal ambient temperature is 18-25 C. When the temperature deviates from the optimal temperature, the luminous flux and luminous efficiency decrease. At temperatures below +10 C, ignition is not guaranteed.
5. Periodic pulsations of their light flux with a frequency equal to twice the frequencyelectric current. The human eye is unable to detect these flickers of light due to visual inertia, but if the frequency of movement of the part matches the frequency of the light pulses, the part may appear to be stationary or slowly rotating in the opposite direction due to the stroboscopic effect. Therefore, in industrial premises, fluorescent lamps must be switched on in different phases of three-phase current (the light flux pulsates in different half-cycles).
The following letters are used in the marking designations of fluorescent lamps: L - fluorescent, D - daylight, B - white, HB - cold white, TB - warm white, C - improved light transmission, A - amalgam.
If you “twist” the tube of a fluorescent lamp into a spiral, you get a CFL – compact fluorescent lamp. In terms of their parameters, CFLs are close to linear fluorescent lamps (luminous efficiency up to 75 Lm/W). They are primarily intended to replace incandescent lamps in a wide variety of applications.
Marking: D - arc P - mercury L - lamp B - turns on without ballast
Arc mercury fluorescent lamps (MAFL)
Fluorescent mercury-quartz lamps (QQL) consist of a glass bulb coated on the inside with a phosphor and a quartz tube placed in the bulb, which is filled with mercury vapor under high pressure. To maintain the stability of the properties of the phosphor, the glass flask is filled with carbon dioxide.
Under the influence of ultraviolet radiation arising in a mercury-quartz tube, the phosphor glows, giving the light a certain bluish tint, distorting the true colors. To eliminate this drawback, special components are introduced into the composition of the phosphor, which partially correct the color; These lamps are called color-corrected DRL lamps. Lamp service life – 7500 hours.
The industry produces lamps with a power of 80,125,250,400,700,1000 and 2000 W with a luminous flux from 3200 to 50,000 lm.
Advantages of DRL lamps:
1. High luminous efficiency (up to 55 lm/W)
2. Long service life (10000 hours)
3. Compactness
4. Non-critical to environmental conditions (except for very low temperatures)
Disadvantages of DRL lamps:
1. The predominance of the blue-green part in the spectrum of rays, leading to unsatisfactory color rendering, which excludes the use of lamps in cases where the objects of discrimination are human faces or painted surfaces
2. Ability to work only on alternating current
3. The need to switch on through a ballast throttle
4. Duration of flare-up when turned on (about 7 minutes) and the start of re-ignition after even a very short interruption in the power supply of the lamp only after cooling (about 10 minutes)
5. Pulsations of the light flux, greater than that of fluorescent lamps
6. Significant reduction in luminous flux towards the end of service
Arc metal halide lamps (DRI, MGL, HMI, HTI)
Marking: D – arc, P – mercury, I – iodide.
These are high-pressure mercury lamps with the addition of metal iodides or rare earth iodides (dysprosium (Dy), holmium (Ho) and thulium (Tm) as well as complex compounds with cesium (Cs) and tin halides (Sn). These compounds disintegrate in the center of the discharge arcs and metal vapors can stimulate the emission of light, whose intensity and spectral distribution depend on the vapor pressure of the metal halides.
Externally, metalogen lamps differ from DRL lamps in the absence of a phosphor on the bulb. They are characterized by high luminous efficiency (up to 100 lm/W) and a significantly better spectral composition of light, but their service life is significantly shorter than that of DRL lamps, and the switching circuit is more complicated, since, in addition, it contains an ignition device.
Frequent short-term switching on of high-pressure lamps reduces their service life. This applies to both starting lamps from a cold or hot state.
The luminous flux is practically independent of the ambient temperature (outside the lamp). At low ambient temperatures (up to -50 °C), it is necessary to use special ignition devices.
HMI lamps
HTI short-arc lamps - metal halide lamps with an increased wall load and a very short interelectrode distance have an even higher luminous efficiency and color rendering, which, however, limits their service life. The main areas of application for HMI lamps are stage lighting, endoscopy, film and video recording in daylight (color temperature = 6000 K). The power of these lamps ranges from 200 W to 18 kW.
For optical purposes, short-arc metal halide HTI lamps with small interelectrode distances have been developed. They are characterized by very high brightness. They are therefore used primarily for lighting effects, as positional light sources and in endoscopy.
Marking: D - arc; Na - sodium; T-tubular.
High-pressure sodium lamps (HPS) are one of the most effective groups of visible radiation sources: they have the highest luminous efficiency among all known gas-discharge lamps (100 - 130 lm/W) and a slight decrease in luminous flux over a long service life. These lamps have a discharge tube made of polycrystalline aluminum inside a glass cylindrical bulb, which is inert to sodium vapor and transmits its radiation well. The pressure in the tube is about 200 kPa. Duration of work - 10 -15 thousand hours. However, the extremely yellow light and the correspondingly low color rendering index (Ra=25) allow their use in rooms where people are located only in combination with other types of lamps.
Xenon lamps (DKsT)
DKsT xenon arc tube lamps, with low luminous efficiency and limited service life, are distinguished by the spectral composition of light closest to natural daylight and the highest unit power of all light sources. The first advantage is practically not used, since lamps are not used inside buildings, the second determines their widespread use for lighting large open spaces when installed on high masts. The disadvantages of lamps are very large pulsations of the light flux, an excess of ultraviolet rays in the spectrum and the complexity of the ignition circuit.
Gas discharge lamps are sources of radiation of light energy in the visible range. The main structural element of a gas-discharge lamp is a glass bulb with gas or metal vapor pumped inside. Electrodes are connected to the flask on both sides, between which an electric discharge occurs and burns.
Gas discharge lamps have a fairly broad classification. There are two main types:
- High pressure gas discharge lamps (GRLVD). They include DID, DRL, DKsT, DNAT.
- Low-pressure gas-discharge lamps (GLLD), which include various types of LLs, CFLs, and special LLs.
These light sources are successfully replacing obsolete incandescent lamps, which, nevertheless, are used in specific rooms where the installation of other lamps is impossible.
The advantages of gas discharge lamps are:
- Efficiency.
- High degree of light output.
- High degree of color rendering.
- Economical.
- Long service life
The disadvantages of gas-discharge lamps are as follows:
- Linearity of the emitted spectrum.
- Expensive.
- Dimensions.
- The need to install ballasts.
- Availability i.e. flickering radiation.
- High sensitivity to voltage changes.
- Toxicity.
- Works on alternating current only.
The quality characteristics of each gas-discharge lamp meet high requirements, such as:
- Operation - up to 20,000 hours of combustion.
- Efficiency - up to 220 lumens per kW of energy.
- Different colors of emitted light: natural, etc.
- allows you to create beams of high intensity light radiation.
The environment in which the combustion process of an electric discharge occurs can be filled with a variety of gases, such as argon, neon, xenon, krypton, as well as vapors of various metals, for example, mercury or sodium.
It is necessary to take into account that gas-discharge lamps of any type must be installed in closed luminaires equipped with special ballasts and ballasts. For successful operation of this type of light sources, special ballasts and ballasts should be installed.
Gas discharge lamps require high parameters of the electrical network to which they are connected. Large (more than 3%) deviations of network parameters from nominal are not allowed.
Gas discharge lamps can be used in production workshops and other premises of factories, in all kinds of shops and shopping centers, offices and various public spaces, as well as for buildings and pedestrian paths. In addition, they are widely used for highly artistic lighting of cinemas and stages, for which professional equipment is used.
The cost-effectiveness of gas-discharge lamps makes it possible to reduce costs for lighting equipment and its components.
A discharge light source or discharge lamp (RL) is an electric lamp in which light is created as a result of an electrical discharge in gas and (or) metal vapor (GOST 15049--81, ST SEV 2737--80).
The principle of the device and the types of discharges used.
The vast majority of discharge lamps are a cylindrical, spherical or other shaped bulb that is transparent to optical radiation. Two main electrodes are hermetically sealed into the flask, between which a discharge occurs. Sometimes additional electrodes are soldered in to facilitate ignition. The internal space of the flask, after removing air and thoroughly degassing the lamp (removing water vapor and other gases sorbed in the flask material and electrodes using heating under pumping), is filled with a certain gas (most often inert) to a different pressure or with an inert gas and a small amount of metal with high elasticity vapors, for example, mercury, sodium, etc. Since the mid-60s, lamps have become widespread, into which, in addition to inert gas and mercury, special emitting additives are introduced, which are mostly halides of various metals.
There is a category of discharge lamps with electrodes operating in an open atmosphere, in which the discharge occurs in the air and in the vapor of the electrode substance. These are carbon arcs. In this type of lamp, electrode material is consumed during operation. In special types of lamps, the discharge burns in flowing gas.
There are also lamps that use high-frequency electrodeless discharge. They are a sealed flask without electrodes containing the necessary gases or vapors.
In stationary radar, two types of discharge are usually used: glow and arc; in pulsed sources, the so-called pulse discharge. In accordance with this, glow, arc and pulse discharge lamps are distinguished.
The type of discharge established in the lamp after ignition is determined by the conditions in the external circuit (values of the supply voltage, ballast resistance), the type of cathode and the pressure of the gas or steam filling the lamp.
A glow discharge occurs at low current densities at the cathode and low gas or vapor pressures, not exceeding several thousand pascals (tens of mmHg). Its feature is a large voltage drop at the cathode, amounting to 50-400 V.
An arc discharge differs from a glow discharge by high current densities at the cathode (102-104 A/cm2) and a small near-cathode potential drop (5-15 V). It can occur over a wide range of pressures (from 0.1 to 1 * 107 Pa) and currents (from tenths to hundreds of amperes). Based on physical processes and the nature of radiation, it can be divided into near-electrode regions and a column. A column of low-pressure arc discharges is similar to a column of glow discharges, occurring at the same pressures, diameters and currents. A column of arcs of high and ultra-high pressure has a number of characteristic features discussed in Chapter. 4, 14--19.
A pulse discharge is a type of non-stationary discharge, characterized by a high power concentration and a short duration (not exceeding 5-10-3 s).
In stationary radar, arc discharges are most widely used, since with their help it is possible to create sources with very diverse characteristics that are highly efficient at relatively low operating voltages.
The vast majority of lamps use column radiation, which has a significantly higher efficiency compared to the radiation of the near-electrode parts and allows the size and characteristics of the luminous area to be varied within a wide range. Radiation from near-electrode areas, such as glow, is used only in special types of lamps.
Classification of PL can be carried out according to various criteria. Due to the wide variety of RL properties and the applicability of the same lamps in different areas, below is a classification according to physical characteristics that characterize all the basic properties of the discharge, such as the radiation spectrum, radiation intensity distribution in the spectrum, brightness, potential gradient, energy efficiency, etc. All these properties of the discharge are determined primarily by the composition of the gaseous medium in which the discharge occurs, the partial pressures of the components of the gas mixture and the current strength. Together with the type of discharge, the luminous area used and the dimensions of the gas gap, they determine the power and voltage, dimensions and design of the lamp and its components, their thermal regime, the choice of materials and related operating features and areas of application.
Based on the composition of the gas or vapor medium in which the discharge occurs, lamps are divided into lamps with discharge in gases, in metal vapors, and in vapors of metals and their compounds.
In terms of operating pressure - for low pressure (LP) lamps from approximately 0.1 Pa to 25 kPa, high pressure (HP) from 25 to 1 - 103 kPa and ultra-high pressure (SVH) more than 1 - 103 kPa.
By type of discharge - for arc, glow and pulse discharge lamps.
According to the area of the glow - to the area of the pillar and the area of the smoldering glow.
By type of radiation source - on:
gas or vapor light, in which the main source of radiation is excited atoms, molecules or recombining ions;
photoluminescent (called simply luminescent for brevity), in which the main source of radiation is phosphors excited by discharge radiation;
electrode-lighting, in which the main source of radiation is electrodes heated in a discharge to a high temperature.
For most photoluminescent and electroluminescent lamps, discharge radiation is mixed with the main type of radiation, so that they are essentially sources of mixed radiation.
Based on the shape of the bulb, pole lamps are divided into:
tubular or linear - lamps in cylindrical flasks, in which the distances between the electrodes are 2 or more times the internal diameter of the tube;
capillary - in tubes with an internal diameter of less than 4 mm;
“spherical” - lamps with a distance between the electrodes less than or equal to the inner diameter of the bulb (lamp bulbs are often spherical or close to it, which is where they got their name); they are also called lamps with a short or medium arc length.
Based on cooling, lamps are divided into lamps with natural and forced (air or water) cooling.
In some types of lamps, the discharge bulb, often called a burner, is placed in an outer bulb, which most often serves to provide thermal control for the burner, but may also perform other functions.
Areas of application of PL.
It has long been known that high-pressure mercury lamps and low-pressure sodium lamps have high luminous efficiency. However, attempts to use these lamps for lighting purposes were unsuccessful due to severe color distortion, especially the color of human skin. For the first time, this disadvantage was overcome in low-pressure mercury fluorescent lamps. Their appearance in 1938 marked a new stage in the development of discharge light sources. For the first time, LLs were created that produce radiation with a continuous spectrum of almost any composition and at the same time have a luminous efficiency and service life several times greater than the luminous efficiency and service life of incandescent lamps. The luminous output of modern LJIs reaches 85--90 lm/W, and the service life is 12--15 thousand hours or more. Currently, LLs are the most widespread discharge light source used for lighting. Their global production reaches almost 1 billion lamps per year.
In the early 50s, high-pressure mercury lamps with corrected color of the DRL type appeared. These lamps, with high luminous efficiency (45-60 lm/W) and a service life of 10-15 thousand hours, are now very widely used. Their global production reaches many tens of millions of lamps per year and continues to grow.
In the 60s, new, extremely fruitful directions were opened in the creation of high-intensity discharge lamps with a wide variety of radiation spectrum and higher efficiencies than those that existed before. For the first time, high-intensity lamps managed to cross the threshold of 100 lm/W. A large number of new types have already been developed and are being produced, which in many respects are significantly superior to high-pressure mercury lamps of the DRL type and occupy a prominent place in the family of discharge light sources. These are high-pressure sodium lamps in crystalline alumina bulbs, widely used for outdoor lighting, and various types of so-called metal halide lamps.
Along with lighting, discharge lamps find numerous and very important applications in many sectors of the national economy, in the latest technology and in military affairs, which is explained by the characteristics of the electric discharge, which make it possible to create radiation sources with a very diverse combination of parameters. By selecting the appropriate filling and discharge conditions, it is possible to create highly efficient radiation sources in almost any part of not only the visible, but also the UV and IR regions of the spectrum, and it is possible to obtain emission spectra consisting of single lines, multi-line and continuous.
This advantage of radars has opened up extremely wide possibilities for their use not only for lighting, but also for numerous special purposes. For example, in industry, agriculture, medicine and other sectors of the national economy, photoluminescence, photochemical, biological, bactericidal and other effects of UV radiation are widely used; Red neon radiation is used for signal lighting, IR radiation is used for radiant heating, signaling, communication, etc.
High- and especially ultra-high-pressure discharges have high brightness in various regions of the spectrum, tens and hundreds of times higher than the brightness of incandescent lamps, due to which they are successfully used in various light-optical devices and installations.
The low inertia of discharge radiation is a disadvantage for general lighting, since it leads to large pulsations of the light flux when operating in standard AC networks with a frequency of 50 Hz. At the same time, it opens up many special applications for radar where modulation of radiation is required.
Pulsed lamps are widely and widely used, producing flashes of extremely high brightness and very short duration. They are used in numerous instruments and installations for observing and studying fast-moving parts of machines and mechanisms (in stroboscopes), when photographing and studying fast processes, aerial photography, optical ranging, etc. Currently, flash lamps are widely used for optical pumping of lasers .
Along with many advantages, RLs also have disadvantages, the main one of which is some complexity of their inclusion in the network, associated with the characteristics of the discharge. Ignition requires higher voltages than steady combustion. To ensure a stable combustion mode, a ballast must be included in the circuit of each lamp, limiting the discharge current to the required limits.
The characteristics of lamps with a discharge in vapors of metals or substances depend on their thermal conditions, and their normal mode is established only some time after switching on. Re-ignition of lamps with a discharge in metal vapor at high and ultra-high pressures without special techniques is possible only after some time has passed after switching off.
