Fluorescent lamps

Different kinds fluorescent lamps

Fluorescent Lamp- gas-discharge light source, the luminous flux of which is determined mainly by the glow of phosphors under the influence of ultraviolet radiation from the discharge; the visible glow of the discharge does not exceed a few percent. Fluorescent lamps are widely used for general lighting, while their luminous efficiency several times more than incandescent lamps for the same purpose. The service life of fluorescent lamps can be up to 20 times longer than the service life of incandescent lamps, provided that sufficient quality of power supply, ballast is ensured and restrictions on the number of switchings are observed, otherwise they quickly fail. The most common type of such sources is a mercury fluorescent lamp. It is a glass tube filled with vapor, coated with inner surface layer of phosphor.

Application area

Corridor illuminated by fluorescent lamps

Fluorescent lamps are the most common and economical light source for creating diffuse lighting in rooms public buildings: offices, schools, educational and design institutes, hospitals, shops, banks, enterprises. With the advent of modern compact fluorescent lamps, designed for installation in ordinary E27 or E14 sockets instead of incandescent lamps, they began to gain popularity in everyday life. The use of electronic ballasts instead of traditional electromagnetic ones makes it possible to improve the characteristics of fluorescent lamps - get rid of flickering and hum, further increase efficiency, and increase compactness.

The main advantages of fluorescent lamps compared to incandescent lamps are their high light output (a 23 W fluorescent lamp provides the same illumination as a 100 W incandescent lamp) and a longer service life (2000 -20,000 hours versus 1000 hours). In some cases, this allows fluorescent lamps to save significant money, despite the higher initial price.

The use of fluorescent lamps is especially advisable in cases where the lighting is switched on for a long time, since switching on for them is the most difficult mode and frequent switching on and off greatly reduces their service life.

Story

The first ancestor of the lamp daylight There was a lamp by Heinrich Geissler, who in 1856 obtained a blue glow from a gas-filled tube that was excited by a solenoid. In 1893, at the World's Fair in Chicago, Illinois, Thomas Edison demonstrated luminescence. In 1894, M. F. Moore created a lamp that used nitrogen and carbon dioxide to produce a pink-white light. This lamp was a moderate success. In 1901, Peter Cooper Hewitt demonstrated a mercury lamp that emitted light blue-green color, and was thus unsuitable for practical purposes. It was, however, very close to modern design, and had much more high efficiency than Geissler and Edison lamps. In 1926, Edmund Germer and his associates proposed increasing the operating pressure within the flask and coating the flasks with a fluorescent powder that converts the ultraviolet light emitted by the excited plasma into a more uniformly white-colored light. E. Germer is currently recognized as the inventor of the fluorescent lamp. General Electric later bought Germer's patent, and under the leadership of George E. Inman, brought fluorescent lamps into widespread commercial use by 1938.

Principle of operation

When a fluorescent lamp is operating, a glowing electric discharge occurs between two electrodes located at opposite ends of the lamp. The lamp is filled with mercury vapor and the passing current leads to the appearance of UV radiation. This radiation is invisible to the human eye, so it is converted into visible light using the phenomenon of luminescence. The inner walls of the lamp are coated with a special substance - phosphor, which absorbs UV radiation and emits visible light. By changing the composition of the phosphor, you can change the shade of the lamp's glow.

Connection features

From the point of view of electrical engineering, a fluorescent lamp is a device with negative differential resistance (the more current passes through it, the lower its resistance, and the lower the voltage drop across it). Therefore, when directly connected to electrical network the lamp will fail very quickly due to the huge current passing through it. To prevent this, the lamps are connected through special device(ballast).

In the simplest case, this can be an ordinary resistor, however, a significant amount of energy is lost in such ballast. To avoid these losses, when powering lamps from an alternating current network, reactance (capacitor or inductor) must be used as ballast.

Currently greatest distribution received two types of ballasts - electromagnetic and electronic.

Electromagnetic ballast

The electromagnetic ballast is an inductive reactor (choke) connected in series with the lamp. To start a lamp with this type of ballast, a starter is also required. The advantages of this type of ballast are its simplicity and low cost. Disadvantages - flickering of lamps with double the frequency of the mains voltage (mains voltage frequency in Russia = 50 Hz), which increases fatigue and can negatively affect vision, relatively long startup (usually 1-3 seconds, the time increases as the lamp wears out), higher consumption energy compared to electronic ballast. The throttle may also produce a low-frequency hum.

In addition to the above disadvantages, one more can be noted. When observing an object rotating or oscillating at a frequency equal to or a multiple of the flickering frequency of fluorescent lamps with electromagnetic ballast, such objects will appear motionless due to the strobing effect. For example, this effect may affect the spindle of a lathe or drilling machine, circular saw, kitchen mixer stirrer, vibrating electric razor blade block.

To avoid injury at work, it is prohibited to use fluorescent lamps with electromagnetic ballast to illuminate moving parts of machines and mechanisms without additional lighting with incandescent lamps.

Electronic ballast

electronic ballast

Electronic ballast is electronic circuit, converting mains voltage to high frequency (20-60 kHz) alternating current, which powers the lamp. The advantages of such ballast are the absence of flicker and hum, more compact dimensions and lower weight compared to electromagnetic ballast. When using an electronic ballast, it is possible to achieve an instant start of the lamp (cold start), however, this mode adversely affects the service life of the lamp, so a scheme with pre-heating of the electrodes for 0.5-1 seconds (hot start) is also used. The lamp lights up with a delay, but this mode allows you to increase the life of the lamp.

Lamp starting mechanism with electromagnetic ballast

IN classic scheme inclusions with electromagnetic ballast for automatic regulation In the process of igniting the lamp, a starter is used, which is a miniature gas-discharge lamp with neon filling and two metal electrodes. One electrode of the starter is stationary and rigid, the other is bimetallic, bending when heated. In the initial state, the starter electrodes are open. The starter is switched on parallel to the lamp.

At the moment of switching on, the full mains voltage is applied to the electrodes of the lamp and starter, since there is no current through the lamp and the voltage drop across the inductor is zero. The lamp electrodes are cold and the mains voltage is not enough to ignite it. But in the starter, a discharge occurs from the applied voltage, as a result of which current passes through the electrodes of the lamp and the starter. The discharge current is small to heat the lamp electrodes, but is sufficient for the starter electrodes, causing the bimetallic plate, when heated, to bend and close with the hard electrode. The current in the common circuit increases and heats up the lamp electrodes. IN next moment the starter electrodes cool down and open. An instantaneous break in the current circuit causes an instantaneous voltage peak across the inductor, which causes the lamp to ignite; this phenomenon is based on self-induction. A miniature capacitor of small capacity is connected in parallel to the starter, which serves to reduce the generated radio interference. In addition, it influences the nature of transient processes in the starter so that it facilitates the ignition of the lamp. The capacitor, together with the inductor, forms an oscillatory circuit that controls the peak voltage and duration of the ignition pulse (in the absence of a capacitor, when the starter electrodes are opened, a very short pulse of large amplitude occurs, generating a short-term discharge in the starter, maintaining which consumes most of the energy accumulated in the inductance of the circuit ). By the time the starter opens, the lamp electrodes are already sufficiently warmed up. The discharge in the lamp occurs first in an argon environment, and then, after evaporation of the mercury, takes on the appearance of mercury. During the combustion process, the voltage on the lamp and the starter is about half the network voltage due to the voltage drop across the inductor, which eliminates the re-activation of the starter. During the lamp ignition process, the starter sometimes fires several times in a row due to deviations in the interrelated characteristics of the starter and the lamp. In some cases, when the characteristics of the starter and/or lamp change, a situation may arise when the starter begins to operate cyclically. This causes a characteristic effect when the lamp periodically flashes and goes out; when the lamp goes out, the glow of the cathodes heated by the current flowing through the triggered starter is visible.

Lamp starting mechanism with electronic ballast

Unlike electromagnetic ballast, electronic ballast often does not require a separate special starter to operate. such ballast is generally capable of forming required sequences stress itself. Exist different technologies starting fluorescent lamps with electronic ballasts. In the most typical case, an electronic ballast heats the cathodes of the lamps and applies a voltage to the cathodes sufficient to ignite the lamp, most often alternating and high-frequency (which at the same time eliminates the lamp flickering characteristic of electromagnetic ballasts). Depending on the design of the ballast and the timing of the lamp startup sequence, such ballasts can provide, for example, a smooth start of the lamp with a gradual increase in brightness to full brightness in a few seconds, or instantaneous switching on of the lamp. Often there are combined starting methods when the lamp starts not only due to the fact that the cathodes of the lamp are heated, but also due to the fact that the circuit in which the lamp is connected is an oscillatory circuit. The parameters of the oscillatory circuit are selected so that, in the absence of a discharge in the lamp, the phenomenon of electrical resonance occurs in the circuit, leading to a significant increase in the voltage between the cathodes of the lamp. As a rule, this also leads to an increase in the heating current of the cathodes, since with such a starting scheme, the filament coils of the cathodes are often connected in series through a capacitor, being part of an oscillatory circuit. As a result, due to the heating of the cathodes and the relatively high voltage between the cathodes, the lamp ignites easily. After the lamp is ignited, the parameters of the oscillatory circuit change, the resonance stops and the voltage in the circuit drops significantly, reducing the filament current of the cathodes. There are variations of this technology. For example, in the extreme case, the ballast may not heat the cathodes at all, instead applying enough high voltage to the cathodes, which will inevitably lead to almost instantaneous ignition of the lamp due to gas breakdown between the cathodes. In essence, this method is similar to the technologies used to start cold cathode lamps (CCFL). This method is quite popular among radio amateurs because it allows you to start even lamps with burnt-out cathode filaments that cannot be started by conventional methods due to the impossibility of heating the cathodes. In particular, this method is often used by radio amateurs to repair compact energy-saving lamps, which are a regular fluorescent lamp with a built-in electronic ballast in a compact housing. After a small modification of the ballast, such a lamp can serve for a long time despite the burnout of the heating coils, and its service life will be limited only by the time until the electrodes are completely atomized.

Ballast from a burnt-out energy-saving lamp is connected to a T5 lamp

Reasons for failure

The electrodes of a fluorescent lamp are tungsten filaments coated with a paste (active mass) of alkaline earth metals. This paste provides a stable glow discharge; if it were not there, the tungsten filaments would very soon overheat and burn out. During operation, it gradually falls off the electrodes, burns out, and evaporates, especially with frequent starts, when for some time the discharge occurs not over the entire area of ​​the electrode, but on small area its surface, which leads to overheating of the electrode. Hence the darkening at the ends of the lamp, often observed closer to the end of its service life. When the paste burns out completely, the lamp current begins to drop and the voltage, accordingly, increases. This leads to the fact that the starter begins to constantly work - hence the well-known blinking of failed lamps. The lamp electrodes constantly heat up and eventually one of the filaments burns out, this happens after about 2 - 3 days, depending on the lamp manufacturer. After this, the lamp burns for a minute or two without any flickering, but these are the last minutes of her life. At this time, the discharge occurs through the remains of a burnt-out electrode, on which there is no longer any paste made of alkaline earth metals, only tungsten remains. These remnants of the tungsten filament heat up very strongly, due to which they partially evaporate or crumble, after which the discharge begins to occur due to the traverse (this is a wire to which the tungsten filament with the active mass is attached), it partially melts. After this, the lamp begins to flicker again. If you turn it off, re-ignition will not be possible. This is where it all ends. The above is true when using electromagnetic ballasts (ballasts). If electronic ballast is used, everything will happen a little differently. The active mass of the electrodes will gradually burn out, after which they will become increasingly heated, and sooner or later one of the threads will burn out. Immediately after this, the lamp will go out without blinking or flickering due to the electronic ballast design that automatically turns off the faulty lamp.

Phosphors and spectrum of emitted light

Typical spectrum of a fluorescent lamp.

Many people find the light emitted by fluorescent lamps to be harsh and unpleasant. The color of objects illuminated by such lamps may be somewhat distorted. This is partly due to the blue and green lines in the emission spectrum gas discharge in mercury vapor, partly due to the type of phosphor used.

Many cheap lamps use halophosphate phosphor, which emits mainly yellow and blue light, while less red and green are emitted. This mixture of colors appears white to the eye, but when reflected from objects, the light may contain an incomplete spectrum, which is perceived as a color distortion. However, such lamps usually have a very high luminous efficiency.

More expensive lamps use “three-band” and “five-band” phosphors. This allows for a more uniform distribution of radiation across the visible spectrum, resulting in a more natural reproduction of light. However, such lamps usually have a lower luminous efficiency.

There are also fluorescent lamps designed to illuminate rooms in which birds are kept. The spectrum of these lamps contains near ultraviolet, which makes it possible to create lighting that is more comfortable for them, bringing it closer to natural, since birds, unlike people, have four-component vision.

Lamps are produced for lighting meat counters in supermarkets. The light of these lamps has pink tint As a result of such lighting, the meat takes on a more appetizing appearance, which attracts buyers.

Execution options

According to standards, fluorescent lamps are divided into bulb and compact.

Flask lamps

Soviet fluorescent lamp with a power of 20 W (“LD-20”). The modern European analogue of this lamp is T8 18W

They are lamps in the form of a glass tube. They differ in diameter and type of base and have the following designations:

• T5 (diameter 5/8 inch=1.59 cm),
• T8 (diameter 8/8 inch=2.54 cm),
• T10 (diameter 10/8 inch=3.17 cm) and
• T12 (diameter 12/8 inch=3.80 cm).

Application

Lamps of this type can often be seen in industrial premises, offices, shops, transport, etc.

Compact lamps

Universal Osram lamp for all types of G24 bases

They are lamps with a bent tube. They differ according to the type of base:

• G24
  • G24Q1
  • G24Q2
  • G24Q3

Lamps are also produced for standard E27 and E14 sockets, which allows them to be used in conventional lamps instead of incandescent lamps. The advantages of compact lamps are resistance to mechanical damage and small size. The base sockets for such lamps are very easy to install in conventional lamps; the service life of such lamps ranges from 6,000 to 15,000 hours.

G23

The G23 lamp has a starter located inside the base; to start the lamp, only a choke is additionally needed. Their power usually does not exceed 14 watts. Main Application - desk lamp, often found in fixtures for showers and bathrooms. The base sockets of such lamps have special holes for installation in ordinary wall lamps.

G24

Lamps G24Q1, G24Q2 and G24Q3 also have a built-in starter, their power usually ranges from 11 to 36 Watts. They are used in both industrial and household lamps. Standard plinth G24 can be mounted either with screws or on the dome ( modern models lamps).

Disposal

All fluorescent lamps contain (in doses from 40 to 70 mg) a toxic substance. This dose can cause harm to health if the lamp breaks, and if you are constantly exposed to the harmful effects of mercury vapor, it will accumulate in the human body, causing harm to health. At the end of its service life, the lamp is usually thrown away anywhere. Individual consumers in Russia do not pay attention to the problems of recycling these products, and manufacturers strive to get rid of the problem. There are several lamp recycling companies, and large ones industrial enterprises are required to recycle lamps.

The service life of fluorescent lamps is 10,000 hours, but at the end of the service life the luminous flux of the lamp decreases to 60% of the original.

The service life of fluorescent lamps, if they are manufactured properly, is several times longer than the service life of incandescent lamps. Therefore, application in installations street lighting fluorescent lamps has all the prerequisites for the widest development.

The service life of fluorescent lamps is longer than that of incandescent lamps; it reaches 2000 - 3000 hours.

The service life of fluorescent lamps is 5000 hours, after which their luminous flux decreases to 60% of its initial value.

The service life of fluorescent lamps is reduced by 20 - 30%, and incandescent lamps and DKsT - by 2 times. This necessitates strict voltage stabilization at the terminals of light sources. Voltage stabilization can dramatically increase the efficiency of using lighting installations at industrial enterprises.

The service life of fluorescent lamps established by standards is 5 times, and mercury lamps are 3 times longer than the service life of incandescent lamps. Hence, gas discharge lamps efficient and economical to illuminate the vast majority of production premises railway transport enterprises.

Fluorescent lamps have the following advantages over incandescent lamps: a) they are much more economical: with the same power, the luminous flux of a fluorescent lamp is several times greater than that of an incandescent lamp; b) fluorescent lamps provide light close in spectrum to daylight, which is extremely necessary in some cases (for example, in the printing and textile industries, in rooms without natural light, etc.); c) the temperature of the bulb does not exceed - f - 50 C, this makes the lamp relatively fireproof; d) the service life of a fluorescent lamp is 2 - 2 5 times longer than that of an incandescent lamp.

Below we describe the main methods of illuminating the control room with fluorescent lamps, since when using them it is possible to sharply increase the level of illumination due to their high luminous efficiency. In addition, the service life of fluorescent lamps is many times greater than the service life of incandescent lamps.

The efficiency of fluorescent lamps, excluding losses in the ballast choke, ranges from 30 to 50 lm/W, and their luminous efficiency is 2-5 times higher than that of incandescent lamps. The choke is necessary, firstly, to stabilize the discharge and, secondly, because the lamp voltage is significantly lower than the mains voltage. The service life of fluorescent lamps is 2500 - 3000 hours versus approximately 1000 hours for incandescent lamps. The cause of damage to a fluorescent lamp is usually sputtering of the cathode.

The disadvantages of regulating illumination by turning off individual groups of light sources include the complexity of networks (the need to lay additional lighting lines), the use of software control devices with the priority of turning off and turning on individual groups of light sources negatively affects their service life. From repeated switching on of light sources (in three-shift work, some of the light sources are switched off in the periods between shifts 3 times a day or about 1000 times a year), so-called switch-on wear occurs, which significantly reduces the service life of some types of lamps. The service life of incandescent lamps with a number of starts of about 2500 practically does not decrease. The reduction in the service life of fluorescent lamps for each switching on is approximately 2 hours; with three-shift operation per year, the service life is reduced by 2000 hours, which is 17% of the nominal service life.

Content:

Artificial lighting has long been firmly established in daily life modern people. Lighting devices are constantly being improved and modernized. Thus, conventional incandescent lamps are being replaced by fluorescent or energy-saving lamps with a higher efficiency. They belong to the category of gas discharge lamps low pressure. Ultraviolet radiation is generated by a gas discharge and becomes visible light using a special phosphor coating. Thus, a luminous flux of fluorescent lamps is created, the intensity of which depends on the power of a particular lighting source.

Main types of fluorescent lamps

All lamps of this type are divided into two main categories. The first type is presented lighting fixtures general purpose, the power of which is in the range of 15-80 W. The color and spectral characteristics of these lamps make it possible to imitate various shades of natural light as much as possible.

The second type refers to light bulbs special purpose. To classify them we use various parameters. According to power they are divided into lamps low power- up to 15 W and high power - more than 80 W. These lamps different type discharge, so they come in arc discharge, as well as with glow discharge and glow. According to the light emitted, special lamps can be natural light, colored, ultraviolet radiation and with individual emission spectra. The distribution of light occurs in different ways, that is, in the form of directional and non-directional light emission. The first option is represented by reflector, panel, slot and other light sources.

Marking of fluorescent lamps

All fluorescent light bulbs are marked with letters. The letter L corresponds to the main name. Other letters are written according to the color of the radiation:

• D - daytime color;
• ХБ - cold white;
• TB - warm white;
• B - regular white;
• E - naturally white.
• Other letters, for example, K, Zh, Z, G, S - correspond certain colors- red, yellow, green, blue and blue.
• The UV symbols indicate ultraviolet light.
• Lamps with improved color rendering quality are designated by the letter C, placed after the first color letters.
• The CC symbol indicates particularly high quality.

Design features are displayed in letters placed at the very end of the marking:

• A - amalgam,
• B - with quick start,
• K - ring,
• R - reflex and others.

The numbers following the letters indicate the power of the fluorescent lamp in watts.

Lamp parameters and mains voltage

There are tables that show in comparative form the characteristics of the most common fluorescent lamps. For example, if the voltage in the electrical network drops below permissible limits, the restart process is significantly deteriorated. And, conversely, if the voltage increases significantly, this can lead to overheating of the cathodes and overheating of the ballasts. In all cases where normal operating conditions are violated, the service life of fluorescent lamps is significantly reduced.

	Power P (W)	Lamp voltageU(IN)	Lamp currentI(A)	Light flowR(lm)	Luminous outputS(lm/W)

The characteristics of all other types of fluorescent lamps are displayed in the same way. It should be remembered that lamps with the same markings may have significantly different parameters due to differences in their overall dimensions.

Influence of external temperature and lamp cooling conditions

During operation, the temperature of the tube may change and deviate from optimal value. That is, it increases or decreases, leading to a decrease luminous flux. At the same time, starting conditions deteriorate, and the service life of products is noticeably reduced.

The drop in the reliability of starting conventional light bulbs becomes especially noticeable when the temperature reaches -5 0 C and below, especially if such a decrease is accompanied by. For example, with a network voltage of 180 V instead of the required 220 V and a temperature of -10 degrees, the number of failures to start fluorescent lamps can range from 60 to 80% of their total number. This dependence makes the use of these light sources ineffective in conditions low temperatures and power surges.

The reasons for the increase in temperature may be environment and closed fittings. In both cases, overheating occurs. In these cases, the luminous flux also decreases, and color changes are also possible.

The electrical characteristics of lamps can change during their operation, that is, during the combustion process. The reason is the additional activation of the cathodes, as well as the release and absorption of various impurities. These unpleasant manifestations usually end within the first hundred hours. In the future, changes in characteristics will be very minor and almost imperceptible. During operation, the brightness of the glow gradually decreases, and the luminous flux of fluorescent lamps decreases. Sometimes after 300-400 hours of burning, the appearance of dark spots and deposits on the ends of the tube becomes noticeable on the bulbs. This indicates possible sputtering of the cathodes and poor quality the lamps themselves.

Other types of fluorescent lamps

Nowadays it is increasingly practiced wide application energy-efficient fluorescent lamps (FLLs). They are used in general lighting and can be completely interchanged with ordinary products, power 20, 40 and 65 watts. ELLs are suitable for all existing lighting installations. Thus, all lamps and ballasts remain in place. All main characteristics of ELLs remain the same as those of standard lamps when the power is reduced to 10%. Appearance is also different as the tubes are 26mm in diameter instead of the standard 38mm. This allows you to reduce the consumption of glass, phosphor, mercury, gases and other materials.

Along with standard products, there was a large number of all kinds of compact fluorescent lamps (CFLs). Their power averages 5-25 W, luminous efficiency is 30-60 lm/W, and their service life reaches 10 thousand hours. Certain types of CFLs can directly replace incandescent light bulbs in a conventional socket. Their design includes built-in ballasts and a standard threaded one.

The advent of compact light bulbs became possible when narrow-band phosphors with high stability appeared. To activate them, rare earth elements are used with the ability to operate at a surface irradiation density that exceeds this value for conventional light bulbs. This made it possible to significantly reduce the diameter of the discharge tube. The total length was reduced by dividing the tubes into separate short sections, located parallel and interconnected. Other options use bent tubes or welded connections.

It should be noted that there are electrodeless compact lamps in which the glow of phosphors is excited by a discharge in a mixture of mercury vapor and inert gases. The required charge is maintained by the energy of the electromagnetic field created directly near the discharge mixture. Such lamps were created using microelectronics, on the basis of which inexpensive and small-sized energy sources were created high frequency with good efficiency.