Low pressure sodium lamps characteristics. General information about sodium lamps

Compared to other sources of artificial lighting, sodium lamps demonstrate the highest efficiency - close to 30%. To save money, it is recommended to buy high pressure light bulbs. The light emitted by high-pressure sodium lamps makes it possible to distinguish colors in almost the entire range, except for short-wavelength, in which the color fades somewhat. Let's talk today about the emergence, application and connection of sodium lamps with our own hands.

Historical reference

High-pressure sodium discharge lamps, which are the main obstacle to astronomical observations, have made the largest contribution to street lighting. Let's delve into history to understand what they are. Tubular lamps, which exhibit low mercury pressure, were invented in the pre-war period.

Similar fluorescent lamps were widely adopted quickly. But it was not possible to obtain a discharge in sodium vapor for a long time, this was due to the low partial pressure of sodium at a low temperature. After a complex of technological tricks, sodium lamps were created that worked at low pressure. But due to the complex design, they are not widely used.

But the fate of sodium lamps, which operate at high pressure, has developed more successfully. Initially, all attempts to create lamps in a shell of quartz glass ended in failure. At high temperatures, the chemical activity of sodium increases and, as a result, the mobility of its atoms. Therefore, sodium in quartz burners quickly penetrated through quartz, destroying the shell.

The emergence of sodium lamps

The situation changed dramatically in the early sixties, when General Electric patented a previously unknown ceramic material that can operate in sodium vapor at high temperatures. He received the name "lucalos". In our country, this pottery is known to the inhabitants as “policor”.

This ceramic is produced by high temperature sintering of alumina. For lighting purposes, only one modification of its crystal lattice is considered suitable - the alpha form of the oxide, which has the densest packing of atoms in the crystal.

The sintering process of such ceramics is very capricious, because it must be chemically resistant to sodium vapor and must have high transparency so that most of the light is not lost in the walls of the discharge tube. Sodium vapor, which serves as a gas-discharge medium in sodium lamps, gives a bright orange light when glowing. From the presence of sodium in the lamp, the abbreviation DNAT came into use, which means arc sodium lamps.

Advantages and disadvantages of sodium lamps

Sodium lamps shine twice as efficiently as ordinary fluorescent lamps of the same power - this can be explained by the small size of the emitter, the light rays from which are much easier to direct in the right direction and other design features.

In addition, with sodium arc lamps, you can recreate much greater illumination. Its ceiling for daylight fixtures reaches 50 watts per square foot, and with the help of sodium lamps, you can achieve 3 times more without any problems!

From an economic point of view, sodium lamps are more profitable - they need to be changed only once every six months, and 1 DNAT-400 lamp can successfully replace 20 LDS at 40 V. It is also much more convenient to work with an average ballast than with 15 small ones. Since sodium lamps use electricity twice as efficiently, when using them, a certain result is achieved at half its cost.

The efficiency of sodium lamps is directly dependent on the ambient temperature, and this, in turn, limits their use a little, because they shine worse in cold weather. Also, the fact that they are more environmentally friendly than mercury lamps is not entirely unambiguous, since most sodium lamps use a combination of sodium and mercury, sodium amalgam, as a filler.

Use of sodium lamps

Typical sites where sodium lamps are used: highways, streets, squares, stretch tunnels, airfields, traffic intersections, sports facilities, construction sites, airports, railway stations, architectural structures, warehouse and industrial premises, pedestrian areas and roads, as well as additional sources lighting.

If you want to somehow decorate your personal plot, then you can buy sodium lamps, which have also found their application in landscape design. Due to the characteristics of sodium lamps, warm and bright orange light, they are used for auxiliary purposes for a kind of decorative effect that mimics an open flame or sunset.

The purchase of sodium lamps is useful if the owner grows seedlings, has a winter garden, greenhouse or conservatory. Of course, sodium lamps will not replace natural light and sunlight, but your plants will not depend on changes in weather conditions and cloudy days if flowers are illuminated with such lamps.

The principle of operation of a sodium lamp

Inside the external cylinder of HPS "a" there is a "burner" - a tube that is made of aluminum ceramics and filled with rarefied gas, in which an electric arc is created between two electrodes. Sodium and mercury are introduced into the burner, and in order to limit the current, an inductive ballast or electronic ballast is used .

To ignite a cold sodium lamp, there is not enough mains voltage, so the principle of operation of a sodium lamp is to use a special IZU - a pulsed igniter. Immediately after switching on, it generates pulses with a voltage of several thousand volts, which is guaranteed to create an arc. The main radiation flux is generated by sodium ions, so their light has a characteristic yellow color.

The burner heats up during operation to 1300 degrees Celsius, so the air is pumped out of the external cylinder to keep it intact. In all sodium lamps, without exception, the temperature of the cylinder exceeds 100 degrees Celsius during operation. The lamp shines weakly after the arc occurs, all the energy is spent on heating the burner. The brightness increases as it warms up and after ten minutes it reaches a normal level.

Types of sodium lamps

If it is more important for you to keep the light running economically for a long time, then it is best to purchase low-pressure sodium lamps, which are characterized by high reliability in operation, light output over a long period of time and energy efficiency.

Sodium lamps are ideal for organizing street lighting, because they are able to emit the monochromatic yellow color familiar to people, but at the same time they do not have sufficient transmission of the light spectrum.

For other purposes, the use of low-pressure lamps is considered difficult, because the colors of objects that are illuminated by such a lamp cannot be distinguished. The color perception of objects indoors is distorted (for example, the green color is converted to dark blue or black), and the design appearance of the premises is lost.

To save money, it is recommended to buy high pressure sodium lamps. The connection of high pressure sodium lamps is most suitable for sports halls, industrial and commercial complexes. The light emitted by high-pressure sodium lamps makes it possible to distinguish colors in almost the entire range, except for short-wavelength, in which colors may fade somewhat.

Installation of sodium lamps

Sodium lamps are widely used today in various sectors of the economy, however, due to the insufficient transmission of the color spectrum, they are most often used as street lighting. Sodium light bulbs, unlike metal halide bulbs, do not care in which position to function.

However, based on many years of practice, it is believed that the horizontal position of the lamp is more effective, because it emits the main stream of light to the sides. To connect any gas discharge lamp, a ballast is required. Sodium lamps in this sense are no exception, the ballast is required for their "warm-up" and normal operation.

ballast

For sodium lamps, the ballast is a ballast, an electronic control gear and a pulse igniter. Undoubtedly, electronic ballasts are rightfully considered the best, which have a number of advantages over inductive ballasts, losing to the latter in terms of cost: at present, their price is quite high.

The most common ballasts are ballast inductive chokes, which are necessary to limit and stabilize the current. The necessary ballast, which is connected to the lamp in the right way, is already in them, so the connection scheme for sodium lamps is reduced solely to supplying voltage to the terminals of the lamp.

Today, two-winding chokes are obsolete, so you should give preference to single-winding ones. A conventional domestic-made choke can be bought at a company for about $ 10, and on the market for half the price.

It must be intended specifically for HPS and have the same power as the lamp. It is necessary to install a “native” choke, otherwise the lamp life may be reduced several times, or the light output will drop catastrophically. It is also possible to "flash" when the sodium lamp goes out immediately after warming up, then cools down, and everything starts again.

Pulse igniter

IZU are required, as described above, to ignite the lamp. IZU manufacturers produce devices with 2 and 3 pins, so the sodium lamp switching circuit may be slightly different. But usually it is depicted on each IZU body. Of the domestic IZUs, the most convenient is UIZU, it is suitable for a lamp of any power and is able to work with all ballasts.

In this case, you can place UIZA next to the ballast and near the light bulb, connecting it to its contacts. Polarity when connecting UIZU does not play a special role, but it is recommended that the "hot" red wire is connected to the ballast.

Noise suppression capacitor

Arc sodium lamps are consumers of reactive power, so it makes sense in some cases (in the absence of phase compensation) to include an interference suppression capacitor C in the sodium lamp circuit, which significantly reduces the starting current and prevents unpleasant situations. For DNaT-250 (3A) chokes, the capacitance of the capacitor should be 35 microfarads, for DNaT-400 (4.4A) chokes - up to 45 microfarads. Dry-type capacitors with a nominal voltage of 250 V should be used.

It is customary to make connections with a thick stranded wire of a large cross section; the network cable must also count on a large current. Make soldering reliable. Tighten the screws tightly, but without excessive force - so as not to break the block.

When connecting sodium lamps on your own, you should take into account such a recommendation - you must not exceed the length of the wires that connect the ballast to the sodium lamp for more than one meter.

Security questions

If you assembled the lamp yourself, make sure that its connection diagram is absolutely correct. If the connection diagram is not drawn on your ballast, or the number of legs on the ballast / IZU does not match the diagram, you should consult with the seller of these parts or an experienced electrician. The consequences of such an error are catastrophic: burnout of one of the 3 circuit elements, knocking out traffic jams, lamp explosion and fire.

If there is grease or dirt on the bulb of the sodium lamp, it may burst due to uneven heating immediately after warming up. Therefore, do not touch the lamp with your hands and wipe it with alcohol just in case after installation in the socket. If drops of water or other liquids fall on the switched on lamp, then this provokes an explosion with a 100% probability!

Using a fan, it is worth checking that it blows and rotates where it should. It is necessary to hang the lamp securely in order to avoid falling - a sodium lamp is heavy and can break something if it falls. When repairing a lamp, some measurements should be taken with the device turned on - do not do this yourself unless you have sufficient experience with high voltage devices.

During the operation of the sodium lamp, once a month, dust off the lamp and reflector and check the condition of the fan. Sodium lamps are recommended to be changed every 4-6 months, since by the end of their useful life their light output drops significantly.

Malfunctions of sodium lamps

Sodium lamps, as they age, acquire the habit of “flashing”: the lamp turns on, warms up as usual, then goes out unexpectedly, and everything repeats after a while. If you notice this behavior behind your lamp, you should try changing the bulb. If changing the lamp did not help, you need to measure the voltage in the network, maybe it is slightly lower than usual.

If the flashing of the sodium lamp occurs irregularly, the reason lies in poor contact or power surges in the network. The most unpleasant situation is a short circuit in the ballast between the turns of the winding, then it must be changed. Sometimes new lamps may also flash, but this passes after a few hours.

Often you can hear how the IZU cracks after turning on the lamp (a sign of work), but the lamp does not even try to light up. This happens most often due to breakdowns in the wire that goes to the lamp from the IZU, or indicates a burnt out lamp. A broken wire between the lamp and the ballast or a burnt IZU may be to blame.

You can try changing the wire between the lamp and the IZU. It is also worth paying attention to the contacts of the IZU and their condition. If that doesn't help, change the bulb. If this does not help, turn off the IZU, because it is able to burn the voltmeter with its impulses, and measure the voltage on the lamp cartridge - it should correspond to the mains voltage at HPS. If there is voltage on the cartridge, change the IZU.

If the sodium lamp does not give any signs of life at all: the IZU does not buzz, the lamp does not glow - most likely the contact is broken in the power cord or the fuse is knocked out. Maybe the IZU burned out, or a winding breakage occurred in the ballast - check the ballast, if it is intact - it is worth changing the IZU.

The ballast can be checked with an ordinary ohm meter. They have a normal resistance of 1-2 ohms. If the indicator is much higher, it means that there was a break in the winding or the contact between the connecting block and the winding terminals was broken (tighten the screws).

Everything is more complicated with an interturn circuit - it affects the DC resistance very little, so it is difficult to detect, while more power is supplied to the lamp than necessary. When there is an overdose of power on a sodium lamp, the lamp overheats quickly and goes out, as a result, “flashing” can also be observed.

Now you know how to connect a sodium lamp! In conclusion, it is worth noting that sodium arc lamps are one of the most efficient categories of visible radiation sources, because they are characterized by the highest light output among all gas discharge lamps known to mankind and a slight decrease in luminous flux with a long useful life.

One of the lighting devices used in the lighting system and widely used are sodium lamps. Sodium vapor is placed inside a glass flask under low pressure. Under the action of an electric discharge, a bright yellow glow is created, the wavelength of which is 590 nm. Due to this, sodium lamps have a very high luminous efficiency. The maximum effect was obtained after the invention of high-pressure sodium lamps. Their principle of action resembles, and sodium is used as a light-emitting additive.

The action of sodium lamps

Burners for sodium lamps are not made of quartz, but of polycrystalline alumina, which is a thin-walled tube with a diameter of 5-9 mm. This design is associated with the high chemical activity of sodium and the high temperature in the discharge.

Inputs for current are caps or disks that are hermetically soldered into thin-walled tubes. The electrodes themselves are made of thorium-activated tungsten. The entire structure of the burner is in the interior of the flask, where a strong vacuum is created. An inert gas in the form of argon or xenon is pumped into the flask, and an alloy of sodium and mercury is introduced in a small amount.

During the operation of the lamp, the walls of its burner heat up due to the effect of the discharge current. At the same time, sodium and mercury evaporate, their vapor pressure begins to rise, resulting in a glow of bright yellow light. The tube-burner transmits light through the glass with almost no loss, which is why a high light output is obtained.

Where are sodium lamps used?

With a very high luminous efficiency, the quality of the color rendering of sodium lamps is at a low level. This circumstance determined their application for other open areas. Sodium lamps are increasingly being used to illuminate certain types of industrial premises where there are no strict requirements for color reproduction.

These types of lamps give a good effect in illuminating the roadway, since the yellow light is well distinguished by drivers. They have high thermal and chemical resistance, allowing to increase the service life up to 28.5 thousand hours.

In addition to low color rendering, sodium lamps have the disadvantage of a luminous flux with a large depth of pulsations. During the entire life of the bulb, the voltage in the light bulb begins to increase every 1000 hours, by approximately two volts. As a result, the lamps at the end of their work simply stop lighting up.

The HPS lamp is today considered one of the most economical among other light sources.

general description

They are used everywhere, you can choose the power ranging from 70 to 400 watts. They can be found mainly in street lighting systems, this includes highways, stations, airfields, tunnels, industrial areas. Thus, the lamps of this type are applicable in those places where there is a need to provide contrast visibility in all weather conditions. The HPS lamp is used in greenhouses and flower beds.

Connection Features

The described lamps should be connected in a special way. Initially, this will require a ballast, which is otherwise called an electronic or electromagnetic ballast. You will also need a pulse ignition device. All of these accessories can be purchased together with the lamps in the specialty departments. However, a number of manufacturers produce sodium lamps that do not require the use of IZU. They use a starting antenna, made in the form of a wire, and also wrapped around the so-called burner.

Main technical characteristics

The HPS lamp has many advantages. Among them, one can single out a long service life, which is limited by a limit of 1200 to 25,000 hours; economy and high light output. The latter indicator can reach the figure of 130 lm / W. However, some technical features of such lamps significantly limit the scope of their use. If we take into account the characteristic that is expressed in color rendering, then HPS, whose power can be equal to 250 or 400 watts, does not act as the best choice in all cases. This is due to the fact that the use of such lamps is advisable only with minor requirements for color rendering.

Among other things, the HPS lamp, whose power is 70, 150, 250 and 400 watts, implies a very long on time, which is from 6 to 10 minutes. It should be noted that the efficiency directly depends on the ambient temperature, which limits the use. For example, at low temperatures, the lamp shines worse. Experts say that environmental friendliness is an ambiguous parameter compared to mercury lamps. This is due to the fact that sodium amalgam, which is a compound of mercury with sodium, is used as a filler in most HPS.

Additional features

If we are talking about sodium lamps of impressive pressure, then they have a high efficiency, which is 30%. If we take into account the spectral analysis of the light emitted by HPS, then the wavelengths ranging from 550 to 640 nm account for the most impressive radiation, which is close to human perception.

If you change the supply voltage, the operating voltage of the lamp will change, as well as other parameters. For this reason, it must be taken into account that the manufacturer advises operating such lamps with a small change in the supply voltage, which changes by 5% on both sides of the nominal value.

Application

HPS lamps, the characteristics of which are described in the article, have the most important characteristic, which is expressed in power. The choice of feature should be appropriate for the area of ​​use. Thus, the DNaT 250 lamp, as well as 70, 150 and 400 watts, can be used when artificial lighting is required for greenhouses, plant nurseries and flower beds. Plants feel most comfortable under the influence of lamps with a power of 150 and 250 watts. If you decide to use a power of 400 watts, then the lighting devices should not be brought closer to the plants than 50 centimeters.

More powerful lamps should not be installed in flower beds and greenhouses for the reason that they can simply burn the plants. The HPS lamp is used, as mentioned above, in underground passages, for street lighting and in closed complexes. However, the most commonly used power for this is 70 or 150 watts. During operation, it is important to ensure that the surface of the lamp is protected from moisture and dust. Therefore, for outdoor use, it is recommended to select IP 65.

What else you need to know about HPS lamps

If you yourself want to connect the HPS lamp, then the information presented in the article above will help you. However, before purchasing such a product, it is important to know about all the features. For example, these light sources are gas-discharge, which indicates that their glow is the result of a gas discharge in a gas mixture of significant pressure. This process is carried out in an external flask, which is a burner filled with a gas buffer mixture.

These are used to illuminate industrial and residential premises for the reason that caustic yellow light is accompanied by a significant pulsation coefficient. Such a spectral composition can significantly reduce visual ability. As a result, there is a risk of getting fatigued quickly.

The power of HPS lamps is selected depending on the purpose of use. Considering the light output, one cannot but note the effect of aging. Thus, by the end of the lifetime, the light output can be reduced by 2 times. It is possible to operate such lamps only at a certain temperature regime, which varies from -30 to +40 degrees.

Conclusion

A luminaire with a HPS lamp cannot be used if it is necessary to illuminate industrial and domestic premises, but it has found its wide distribution in other areas. Before purchasing, it is important to familiarize yourself with the technological features of the device in more detail. Consumers may even consider the HPS lamp circuit before making a purchase. This information will not be redundant. In addition, it is important to ask the seller how the lamp is suitable for use in certain conditions. Perhaps the purchase will not be appropriate if the device is subjected to constant exposure, for example, to extremely low or extremely high temperatures during the entire period of operation. As a result, you will encounter the problem of rapid failure of the lamp, which will entail unforeseen expenses.

The designs of the first lighting devices were quite primitive. They consisted of two electrodes, between which an arc discharge burned. These designs had two significant drawbacks: due to burnout, the electrodes needed constant adjustment, and the radiation spectrum captured a significant fraction of the ultraviolet. Therefore, incandescent lamps, and later sodium lamps, very quickly occupied their niches in indoor and outdoor lighting.

In fairness, it must be said that even today these lighting devices still compete with brands of more economical LED lamps.

But there are areas where the use of sodium lamps will be a priority for a long time. Optimism is added by the high radiation flux in, the duration of the service life and the high efficiency of these devices.

Design and principle of operation

The action of a sodium gas discharge lamp is based on the property of sodium vapor, which is capable of emitting monochromatic bright light in the yellow-orange spectrum. This gaseous substance is enclosed in a special flask (tube) called a burner. Since sodium vapor heated to a high temperature acts aggressively on glass surfaces, the tube is made from more stable substances - borosilicate glass or polycrystalline aluminum oxide (depending on the type of lamp).

On each side of the burner are electrodes designed to create arc discharges that heat sodium vapor. This design is housed in a vacuum glass flask ending in a threaded base.

Here it is appropriate to note that there are two types of such lighting devices: NLND (low pressure) and NLVD (high pressure). The design described above gives a general idea of ​​the design of gas-discharge sodium lamps of both types. These lamps differ in the design of the burners and the working vapor pressure inside the tubes.

In low-pressure sodium lamps, its value does not exceed 0.2 Pa, and in LLP - about 10 kPa. Accordingly, the operating temperatures of sodium vapor also differ: 270–300°C for NLND and 650–750°C for high-pressure burners. From this it is clear that NLVD burners have sufficiently high levels of light flux, that is, they shine quite brightly.

There is nothing surprising in the fact that high-pressure sodium lamps gradually replaced NLND-type lighting products from the market. Although the light spectrum corresponding to low pressure is more pleasing to the eye, NLND burners have given way to more powerful models with a fairly high light emission.

Given this circumstance, we will focus on lamps of the NLVD type. The design of such a light source is shown in Figure 1. Here is a diagram of a tubular HPS lamp.

Rice. 1. HPS device

The numbers indicate:

• 1 - outer flask;
• 2 - nickel-plated base;
• 3 - contact plates;
• 4 - gas discharge tube (burner);
• 5 - molybdenum electrodes;
• 6 - sodium vapor with an admixture of inert gases (argon or xenon);
• 7 – sodium amalgam;
• 8 - compacted niobium input;
• 9 - metal conductors;
• 10 - molybdenum plates;
• 11 - getters (getters).

On fig. 2 shows a photo of a sodium lamp of this type.

Rice. 2. An example of a photo of a high pressure sodium lamp (NLVD)

The flasks of sodium lamps are cylindrical (as in Figure 2), elliptical, coated from the inside with a thin layer of light-scattering substance (DNaS). They can be frosted (DNaMT) or contain a mirror reflector next to the burner (DNaZ).

Operating principle.

The ignition of the burner of a sodium lamp occurs from an electric arc that occurs between the electrodes. A stream of charged particles from sodium vapor is formed in the electric discharge channel. Strictly speaking, inside the discharge tube is not pure sodium, but a mixture of gases. For better ignition of the arc, argon or xenon or mercury vapor is added.

Mercury-free lamps already exist today. They still have a more complex design, but development continues and they will probably someday replace conventional mercury lamps.

After a high pulsed voltage is applied to the cathodes, the NLVD is ignited. For a while, the lamp glows dimly. After about 7 - 10 minutes, after the sodium vapor has warmed up to operating temperature, the lamp switches to the mode of maximum luminous efficiency.

The principle of operation is similar to the operation of mercury lamps, but to turn on a lamp filled with sodium vapor, a higher impulse voltage is required than to turn on. After the burner has warmed up, the impulse currents must be limited. Therefore, for this type of lighting fixtures, NLVD manufacturers have developed special ballasts with built-in pulse igniters. Without the use of IZU, it is impossible to light a sodium lamp by connecting it directly to the electrical network.

Classification of sodium lamps

As noted above, sodium lamps are of two types: NLND and NLVD. They can also be classified according to the type of bulb, the composition of impurities, and the radiation power. Since the pressure of sodium vapor directly affects the light output of the lamp, we will make a brief review of the lamps in this parameter.

Low pressure (NLND)

The first to appear was LLND (low burner pressure). They provide low color rendering, but have a pleasant radiation spectrum for humans. They were massively used in the 30s of the last century. Low pressure lamps can still be found today, but they are being replaced by more advanced sodium lamps, which we will discuss in more detail.

High pressure (HLPH)

The high efficiency of NLVD made them a leader among other gas-discharge light sources. The light output of such lamps reaches 150 lumens / watt. They can work up to 28500 hours. True, at the end of their service life, their light output decreases, and the color shifts to the red side of the spectrum.

In a number of parameters, NLVDs are superior to the qualities of fluorescent lamps that emit a cold glow and metal halide lamps that consume a lot of electricity. Among modern electric light sources, there are few lamps that can compete with sodium lamps.

Advantages and disadvantages

The advantages of sodium lamps are as follows:

• efficiency of tubular lamps;
• long service life;
• stability of electrical parameters throughout almost the entire service life;
• warm shades of sodium radiation (see Fig. 3);
• a fairly wide temperature range at which sodium lamps work stably - from -60 to +40 degrees Celsius.

Unfortunately, there are disadvantages that limit the scope of NLVD:

• annoying flickering light frequency;
• inertia when turned on;
• explosiveness of NLVD;
• the presence of mercury content in most models;
• resonant radiation weakens during operation;
• increase in power consumption as the end of service life approaches;
• the need to use ballasts to connect lamps.

Ballasts are sometimes a source of noise and consume up to 60% of the power consumed. They also require additional maintenance.

Despite the presence of these disadvantages, in some areas where the color rendering of the light source is insignificant, the use of NLVD is very beneficial, and in some cases simply irreplaceable.

Application area

The yellow-orange light of the lighting devices is pleasing to the eye, but its monochromaticity muffles the colors of the interior paints. Therefore, sodium lamps are not used in residential areas as the main lighting device. They can serve only as elements of decorative lighting.

Figure 3 shows a photo of such a backlight.:

Figure 3. Sodium lamp light

Studies have shown that the yellow glow tends to have a beneficial effect on the development of plants. At the same time, their growth increases, the yield increases. In summer, the vegetation receives such illumination from the sun's rays. But in greenhouses where vegetables are grown in winter, there is clearly not enough sunlight. NLVDs are ideal for this purpose (see Figure 4).

The use of sodium lamps for lighting greenhouses not only increases yields, but also saves energy.

Figure 4. Greenhouse lighting with high pressure sodium lamps

Pay attention to the monochromatic light of sodium lamps. The muted color of the plants indicates that almost all the light from the lamps is spent on the production of chlorophyll.

Monochromaticity is very useful in street lighting. Such light does not scatter in fog. The use of street lamps to illuminate motorways improves traffic safety. Park areas and paths with street lighting based on NLVD, which have a yellow luminescence spectrum, increase the comfort of vacationers at night.

Figure 5. Street lighting using NL

Less often, such lamps are used in industrial premises (usually in warehouses), as well as in the design of advertising signs and decorations.

Connection

Since a high pulse voltage (sometimes up to 1000 V) is required to ignite the burner, this complicates the connection schemes for sodium lamps. You have to use additional equipment. There are two types of control gear for NLVD: EMPRA (electromagnetic) and electronic control gear (electronic).

IZUs are connected in parallel to the lamp circuit, and chokes are connected in series, sometimes through a pulse igniter.

Figure 6 shows the connection of the NLVD.

Figure 6. NLVD connection diagram

Pay attention to how the choke (ballast) and IZU are connected.

Please note that when connecting yourself, you must comply with the requirement: the length of the wire from the choke to the lamp base should not exceed 100 cm.

Some foreign manufacturers supply sodium lighting devices with built-in starting devices in the lamp bulb to the market.

Safety and Disposal Considerations

Risks in the operation of sodium lamps are associated with high pressure and temperature inside the burner. Even the surface of the flask heats up to 100 °C and can cause burns if handled carelessly. There is a possibility of rupture of the flask under the influence of hot gases escaping from the burner.

In order to protect against the consequences of destruction, lamps are made in which the lamps are behind thick glass. Pay attention to the design (Fig. 5).

Due to the presence of mercury in sodium lamps, special disposal requirements apply. Used appliances must not be disposed of in general waste bins. They must be sent to special enterprises for neutralization and processing.

Video in addition to the article

Gas-discharge sodium lamps are the most efficient among the existing light sources in terms of light output to energy expended, but their spectrum is uncomfortable for the human eye. The absence of blue color forms a monochrome picture of the surrounding space. Because of this feature, sodium lamps, despite their excellent efficiency, are used to a limited extent - mainly for street lighting. Meanwhile, the predominance of the yellow-red "solar" and green spectra has a beneficial effect on the growth of all types of plants, which is widely used in greenhouses.

What are sodium lamps

They belong to gas-discharge lamps by analogy with halogen, xenon "brothers". The source of the glow is gaseous sodium combined with other elements, pumped into a glass flask. Under the influence of an electric arc, sodium is heated to high temperatures and begins to glow with a bright yellow-orange light, turning into a red spectrum by the end of the lamp life.

Characteristics

The power of sodium lamps is the highest in the class - up to 200 Lm/W (Lumens per Watt). Characteristic features are the low color temperature (2100-2700 K) and the dominance of the yellow-red emission spectrum with a minimum amount of blue. This combination leads to the fact that lamps of this type fill the surrounding space with monochrome yellow-orange light, as a result of which the human eye does not distinguish colors and outlines of objects well enough. They lose depth, volume, orientation and estimation of distances to objects becomes difficult. But for plants at certain stages of growth, the "solar" spectrum of radiation is just necessary.

Types of lamps

According to the principle of operation, they are divided into two main classes:

• High pressure sodium lamps (HPS - HighPressure Sodium).
• Low-pressure sodium lamps (LPS - Low-Pressure Sodium).

LPS lamps were developed in the 30s of the last century. They have the highest efficiency (180-200 Lm / W), however, due to structural imperfections, these lamps turned out to be capricious and even dangerous. Ordinary quartz glass is defenseless against the aggressive effects of sodium: it quickly evaporated, and if the lighting fixture is broken, the gas can explode (ignite) when reacting with oxygen.

In the 1960s, General Electric developed ceramics using aluminum oxide (polycor, loucalos) that could resist sodium at high temperatures. This breakthrough allowed a return to the production of this type of lighting device, which has excellent efficiency. To improve the glow of the gas, it is pumped under high pressure. The electrical circuit is simpler than that of the LPS. Unfortunately, the increase in gas pressure and other factors led to a significant decrease in light output - up to 50-150 Lm / W (depending on its power), but the color rendering index (CRI) increased from 20 to 85 and higher (from insufficient to good) .

Application area

Luminaires with low-pressure sodium lamps are not widely used in the world. In the USSR and the USA, they relied on more technologically advanced mercury light systems. In a number of European countries, they are actively used to illuminate roads.

High pressure sodium lamps are more common. We use them to illuminate city streets, in landscape design, to illuminate architectural objects. Used in industrial premises where bright light is not required. Recently, leading corporations (Philips, General Electric and others) have significantly improved the design and consumer qualities of these lamps: their spectral coverage has expanded significantly, the color temperature has increased (from 2100 to 2700 K) - some models are already suitable for lighting residential (industrial) premises . Of particular note is the use of sodium lamps in greenhouses.

Classification

Sodium lamps differ in several important parameters. According to the constructive type, they are divided into:

• Arc sodium mirror (DNaZ).
• Arc sodium matted (DNaMT).
• Arc sodium in a light-scattering flask (DNaS).
• Arc sodium tubular (DNaT).

Lamps are also distinguished by the current consumed (220V and 380V), which, in turn, are divided by power: from 50 to 1000 W.

Sodium lamps for greenhouses

An analysis of the energy consumption of greenhouses showed that the processes of irradiation and heating of plants are the most energy-intensive. About 40% of the electricity consumed by greenhouses is used for irradiation. Therefore, farmers achieve an increase in vegetable production through the introduction of energy-saving lighting devices.

Of great importance, in addition to the optimal parameters of the microclimate of greenhouses, is the quality of plant irradiation. Therefore, it is also relevant to study the influence of qualitative lighting parameters on the growth and morphological development of seedlings. The use of fundamentally new light sources in plant irradiation technologies - modern sodium lamps in combination with other sources of illumination (for example, LEDs) - can significantly increase the final yield.

Scientific approach

The Dutch corporation Philips is the leader in improving greenhouse lighting, which is not surprising, given the leading position of the greenhouse industry in the Netherlands. The company conducted scientific and practical studies (in 2012 in Ukraine, in 2013 in Holland), which proved that sodium lamps are the most preferable for plants. They are more efficient than compact fluorescent lamps, which have a lower light output and do not provide an optimal light spectrum. In parallel, it has been proven that incandescent lamps and mercury lamps consume too much electricity to be economically viable.

Even better performance is achieved if the plants are illuminated not only from above, but also on the sides, in the aisles. Economical light-emitting diodes (LEDs) are quite suitable for this. The combination of sodium lamps with LEDs contributes to higher yields. In 2012, the first industrial greenhouse was created in Uman (Ukraine), where these types of lighting fixtures were combined. The plot area under mixed illumination with LED and sodium lamps was 6000 m 2 . In total, 1230 LED modules and 870 lamps with HPS lamps were installed in the greenhouse. The experiment showed that the yield of tomatoes (subject to other requirements) can reach 73 kg / m 2 annually.

Then, thanks to a similar experiment in the Netherlands (2013), the combined use of HPS and SD led to a 30% increase in yield. Subsequently, the technology was adopted in England, Denmark, Canada, Japan, China and other countries.

Technology

As a rule, industrial greenhouses are made of transparent materials so that the plants are illuminated by the sun. However, at latitudes greater than 40° (closer to the poles), natural light is only enough for 4-5 months (May-September). The rest of the time, additional lighting is needed. Moreover, at different stages of the growing season and for different crops, their own radiation spectrum is required.

A lamp for a sodium lamp is placed on top - it charges the plants with yellow-red "sunshine" light (the green spectrum, also emitted by these lighting devices, is not so important). LEDs (or fluorescent lamps) are useful as an additional tool for side irradiation, the main advantage of which is that, being in the lower part of vertically grown plants, the light falls on the lower tiers of leaves, which receive insufficient upper light. This combination increases the intensity of photosynthesis, favors the growth and proper development of plants. Supplementary lighting is useful at stages when crops require a blue spectrum of light, which is almost absent from sodium lamps.

How it works

For the absorption of light photons in plants, special pigments are responsible - carotenoids, a- and b-chlorophylls. Carotenoids absorb light exclusively in the blue range, chlorophylls - blue and red. However, the absorption maxima of chlorophylls - the main photosynthetic pigments - are in the range of 640-680 nm, and carotenoids - in the range of 470-480 nm. According to these parameters, the most efficient light sources for greenhouse conditions are high-pressure sodium lighting lamps (HPLL) with an operating range of 500-700 nm. Their stability, service life, luminous efficiency, economic efficiency are the most optimal.

Lamps with a power of 50-150 W are less reliable and have a low stability of parameters over their lifetime than lamps of medium power (250 W or more). The reasons for this are the presence of a noticeable rectifying effect when igniting low-power lamps, which can reach 2 minutes. In this case, an increased current passes through the lamp, resulting in intensive sputtering of cathode materials and the formation of an opaque coating on the inner surface of the discharge tube. The ignition pulse and the magnitude of the starting current affect the significance of the rectification effect, so the pulse energy must ensure a quick transition from a glow discharge to an arc one. To prevent the effect of current rectification, devices are used to block direct current. Therefore, in greenhouses, NLVD with a power of 250 W or more is more often used.

However, numerous theoretical and experimental studies of the processes in the discharge, on the electrodes, and in the near-electrode sections of gas-discharge lamps have shown that there are a number of issues that require further improvement. For NLVT, which are used in greenhouse crop production, it is necessary, first of all, to optimize the spectral composition of the radiation for specific light crops and reduce the mercury content in the discharge tube, preventing possible environmental pollution by mercury vapor from devices that are out of order.

Environmental issues

The creation of modern technologies for growing greenhouse plants is associated with the use of high-intensity discharge lamps, in particular sodium ones. Their widespread use is a positive factor in the intensification of this production, although it is associated with a serious environmental problem. The composition of the vast majority of modern discharge lamps includes a toxic substance - mercury. Sodium lamps, for example, may contain sodium amalgam (an alloy of mercury). If such a lamp breaks above the plantings inside the greenhouse, the plants placed under it (greens, vegetables, seedlings, indoor flowers) become unusable.

The main direction of improving environmental friendliness is the creation of highly efficient mercury-free gas-discharge lamps. Recently, these works have been carried out by individual lighting companies, including those in the CIS countries. Sodium lamps with reduced mercury in the discharge tube and completely mercury-free models already exist and are increasingly being used in the greenhouse industry.