Metal halide lamp. Metal halide lamps: their types and applications What is the difference between a metal halide lamp and a halogen lamp

Today, the lighting market is more diverse than ever. Therefore, sometimes certain difficulties arise when choosing a lighting source for your apartment or house.
Many people prefer to use metal halide and halogen lamps as a light source.

This article will help you with such a difficult choice and will tell you what these lamps are and why they are so popular.

A little about the products

A halogen lamp is a type of incandescent lamp. Inside, such a lamp contains, in addition to the filament itself, also halogen pairs. The halogens can be chromium, iodine, fluorine or bromine.
The principle of operation of such a lamp is that the electric charge coming through the filament enters into a chemical reaction with the halogens and tungsten atoms of the filament. Moreover, in the presence of high temperatures, such a compound disintegrates. As a result, the vast majority of tungsten particles settle on the filament body. This prevents particles from settling on the inside of the flask. The principle of “restoring” the filament is based on this process. This reaction is called the regenerative tungsten-halogen cycle.
Due to the presence of such a regenerative reaction, the service life of halogen lamps has increased significantly compared to other lighting devices. Such lamps can last up to 12,000 hours. At the same time, the main advantage of such a lamp is its energy efficiency while reducing the size of the bulb itself.
In general, the following positive aspects can be highlighted for such products:

long period of work;
compact dimensions;
reduction of energy consumption;
excellent color rendering performance;
the color spectrum is in the range of 2800-3000K;
warm or neutral shades of light.

In addition, like everything in the world, the halogen type of lamps also has some disadvantages. These include:

fire hazard, which is present due to the fact that the lamp bulb can heat up to 500°C and above;
sensitivity to voltage changes;
The light bulb is sensitive to grease-containing contaminants. Therefore, you can only twist and screw it through a napkin or protective gloves.

But still, despite the shortcomings, such lamps are quite common today.

Variety

One of the varieties of halogen lamps are metal halide lamps. They are also called HID lamps.

Metal halide lamps

They belong to the group of gas-discharge light sources. Here, inert gas (argon and xenon), halides of certain metals or mercury are used as a filler with which the discharge tube is filled. The source of optical radiation in light bulbs is plasma from an electric arc discharge. This plasma results from ionization from evaporating metal halides or mercury particles. In turn, ionization appears as a result of the influence of electric current.
This operating principle allows you to obtain a source of quite bright and powerful light flux. At the same time, color rendition remains at a fairly high level.
Metal halide light bulbs have the same advantages and disadvantages as their halogen counterparts.

Note! The service life of metal halide lamps is slightly longer than that of halogen light sources. It is approximately 10,000-15,000 hours.

Metal halide light sources are significantly more efficient than halogen lamps. And at the same time they do not require special ballasts for installation.
But there are also disadvantages of exclusively this type of light source:

somewhat extended switching period. For such bulbs, maximum brightness is achieved only 5-10 minutes after switching on;
The minimum interval for restarting is approximately 10-15 minutes.

These products are produced in a fairly wide power range: from 20 W to 20,000 W.
In addition, metal halide lamps can have a different color spectrum:

daytime white;
Blue colour;
red, etc.

Different color combinations are achieved by using different halides (salts).

Connection features

For HID light sources, it is worth remembering that their connection to electronic ballasts (or ballasts) is carried out using a high-voltage cable. In this case, the cable must have a breakdown voltage for insulation of at least 6 kV. As a result, the output voltage for igniting the electronic ballast will be 5 kV.

Note! For the secondary circuit of electronic ballasts (ballasts), household network cables are not allowed.

Lamp connection diagram

These devices are necessary in order to maintain the operating mode of the light bulb at the required level. Therefore, the quality of lighting and luminous flux directly depends on which ballast model was used in the connection diagram.
In all other respects, the connection diagram is not very different from other types of lighting devices. Nuances appear in the type of installation.
Depending on the type of installation, metal halide lamps come in several types:

built-in The principle of embedding a lighting fixture is used here. In this way, you can fix the lamp on a suspended ceiling structure;
invoices. In this situation, the installation principle involves simply “placing” the device on the work surface;
track. Such lamps have special reflectors. They can be used for accent or general lighting;
hanging.

Depending on the type of lamp chosen, their installation is carried out according to a certain scheme.
In this case, metal halide bulbs can simply be screwed into spotlights. This method is considered the simplest.
Note! Installation of such a lamp can only be done while wearing protective gloves or using a cloth.

This is a must, because the material from which the light bulb is made reacts with the fatty layer of the hands and, with further use, can lead to an explosion or malfunction of the lighting device.

In other situations, ballasts should be used. However, some manufacturers produce this equipment in disassembled form. Therefore, additional complexity arises when assembling the device yourself. In general, the lighting kit has the following components:

lighting fixture housing;
metal halide lamp;
Ballast or ballast.

Note! When screwing the light bulb into the base, ensure that they make perfect contact. If even one gap remains, the lamp may quickly burn out. In this case, before installation, you should check the quality of the base itself, since its shortcomings can also lead to burnout.
To get high-quality lighting, use only proven, licensed equipment and light sources. It is better to buy products from well-known manufacturers who have been working in the lighting market for a long time.

Purpose

Metal halide and halogen lamps are mainly used in situations when there is a need for a combination of the following qualities:

power;
efficiency;
compactness.

Light from a lamp

Moreover, these products can be used to create lighting both at home and outdoors. The use of such light sources allows you to create lighting in open spaces. Therefore, they are often used for lighting:

industrial workshops;
personal plots;
theaters and museums;
spacious rooms in houses and apartments.

At low power, such light bulbs are used for office or advertising lighting. In addition to all this, such lamps can be found in greenhouses, greenhouses and even aquariums.
Also, this type of light bulbs is actively used in green landscapes for decoration and emphasizing certain design ideas. With such lighting, your garden plot will become a real work of art.
As you can see, metal halide and halogen lamps are widely used today. Due to their properties and undeniable advantages, they are used for a variety of purposes.

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Short-lived and ineffective incandescent lamps are today being replaced by modern analogues with good light intensity and a wide power range.

Such representatives of the new generation of lighting technology are metahalogen lamps.

Thanks to its long service life and good color rendering, coupled with low heat dissipation and high light intensity, metal halide lamps have found their application in almost all spheres of human life, from illuminating plants to lighting shop windows and stadiums. The possibility of choosing a design also played a big role here - tubular with quartz or ceramic burners, double-ended bayonet or threaded, suitable for easy installation, single-ended with an internal or external bulb (the latter are most often used by photographers due to the almost perfect quality of light), with an aluminum reflector and simply compact - the features of a particular model depend on the required power and purpose of use.

Such lamps are turned on using a special one. Within two minutes, they reach maximum brightness of light emission, emitting a soft buzzing sound. However, it takes about five to ten minutes to relight them as they need to cool completely. This feature limits the use of metal halide lamps in some industries.

Usually, metal halide lamps cannot be used without indoor light due to their UV radiation. However, there are models with a built-in UV filter that are absolutely safe for humans.

Very durable, working up to 15,000 hours, with stable brightness throughout the entire period of operation, metal halide lamps will allow you to reduce costs for electricity, installation and technical support of any facility. Such bright and economical light sources cannot be purchased in regular stores, but on our website www.site you can choose the option that is right for you.

Halogen lamps are a type of ordinary incandescent lamps, with one significant difference - while in ordinary lamps a high degree of vacuum is fundamental, then in halogen lamps a certain amount of gas is introduced - bromine or iodine vapor. What is the essence of this change? The operating principle of an incandescent lamp is to heat a tungsten filament with an electric current. During its service life, part of the metal from the surface of the spiral evaporates, which leads to a decrease in the thickness of the thread in some areas and, as a consequence, to an increase in the resistance of these areas. Increased resistance leads to increased temperature and, again, increased evaporation. This process is avalanche-like in nature, which ultimately leads to burnout of the spiral. In addition, the evaporated metal settles on the inner surface of the bulb, causing it to darken and reduce light transmission. The introduction of halogen vapor makes it possible to organize the so-called halogen cycle. It is based on the chemical reaction of the interaction of halogen vapors with evaporated metal. This compound is not stable and when exposed to high temperature of the coil, it decomposes into metal and halogen. The peculiarity of this reaction is that decomposition occurs near the most heated sections of the spiral, that is, where the thickness is smallest. The use of a halogen cycle can significantly increase the service life and increase the temperature of the coil, which leads to an increase in the quality of the luminous flux. Halogen lamps are smaller in size compared to incandescent lamps.

Features of operation.

The surface of the halogen lamp bulb has a high temperature and is made of special quartz glass. During operation, do not touch the surface of the glass with your hands. The slightest traces of fat burn at high temperatures, leaving blackening on the surface, which leads to local overheating of contaminated areas and failure of the halogen lamp. To prevent this, the glass flask must be washed with alcohol after installation, using a cloth that does not leave lint particles on the surface.
High temperatures also increase fire safety requirements.
Turning on halogen lamps together with a dimmer to adjust the brightness leads to a decrease in their temperature. This disrupts the halogen cycle and deposits metal on the inner surface. To avoid this, it is necessary to periodically turn on the lamp at full heat for several tens of minutes.
The high luminous efficiency and small dimensions of halogen lamps allow them to be successfully used in car headlights.

Low voltage halogen lamps.

Lamps are available in different supply voltages. The use of low voltage lamps (usually 12 V) as lighting requires the use of step-down transformers. A transformer for halogen lamps can be made either traditionally, on a metal core (electromagnetic transformer), or using radio-electronic elements (electronic transformer). When meeting the maximum power requirements, electromagnetic transformers have very high reliability, but at the same time they have a high weight, which increases with increasing power. Electronic transformers are free from this drawback. However, if performed poorly, they can serve as strong sources of radio interference. In any case, the transformer for halogen lamps must have some power reserve.

Metal halide lamps.

Metal halide lamps have a completely different operating principle. In these lamps, the light source is an electrical discharge in a gas environment. Metal halide lamps (MHLs) are a further stage in the development of high-pressure gas-discharge lamps. They are known as DRL (mercury arc fluorescent). The basis of the operation of these lamps is an electric discharge in mercury vapor and inert gas. Since such a discharge produces mainly ultraviolet radiation, the inner surface of the bulb is coated with a layer of phosphor, which converts ultraviolet radiation into visible light. Using different coating compositions, you can obtain different shades of glow.

The introduction of additives in the form of compounds of various metals with halogens makes it possible to change the color characteristics of MGL without using phosphors. Also, the introduction of halogen compounds makes it possible to almost completely get rid of such a drawback of DRL as difficulty igniting a lamp that has just been turned off, since the high pressure of heated mercury vapor does not allow a discharge to occur.
How the MGL is ignited can be seen in this video.

MGL design.

The main difference between most types of metal halide lamps and other types is the presence of two glass bulbs. The external bulb makes it possible to reduce the dependence on ambient temperature, which is important for the stability of the light parameters of the MGL.

Features of operation.

Since cold MGLs contain mercury, they are subject to specific requirements for their spatial location. MGLs are produced designed for installation in both vertical and horizontal positions.
Failure to comply with these requirements does not guarantee normal operation of the MGL. Lamps made with two bases are widely used in floodlights and allow only horizontal installation. Some types of MGL can be installed in different positions.

MGL connection.

The operating features of metal halide lamps require the use of specific equipment. The occurrence of an electrical discharge requires increased voltage and, at the same time, the physics of discharge in a gaseous environment have a greater dependence of the magnitude of the flowing current on the supply voltage, which forces the use of current-limiting elements. The starting and current limiting equipment is called starting and regulating equipment - ballasts. There are both transformer control gears, based on electromagnetic transformers with increased magnetic dispersion, and electronic ones. The latter have significantly smaller dimensions and weight. Electronic lamp control units must strictly correspond to the type of lamps used.
Information on IGL is well covered in the video:

Areas of use.

Increased light output, efficiency and small dimensions allow the use of metal halide lamps in various lighting equipment. The majority of lighting spotlights use MGLs.
The currently widespread car xenon headlights also belong to MHL. The presence of xenon serves mainly for the initial occurrence of the discharge. Further, during operation, the discharge occurs in mercury and halogen vapors.

MGLs are often incorrectly called metal halides. This name does not correspond to language norms. Also the name “metal halide” is a misnomer. This name is sometimes used as a result of reading the English name “metal halide lamp”.

Metal halide lamps (MHLs) are one of the types of high-pressure gas-discharge lamps (GRLs). The light bulb differs from other GRLs in that emitting additives (EAs) - metal halides - are dosed into the MGL burner to correct the spectral characteristics of the arc discharge in mercury vapor. Among light sources they are the most compact and powerful.

Metal halide lamps: what is important to know before buying?

Photo 1 - HPS lamp 70W/2000K 5800Lm E27 10t.h. (156x39) HPSL-70-E27-T IEC

Use MGL:

in construction;
in architectural design;
for illumination of greenhouses.

Types of metal halide lamps:

single-base;
double-ended;
universal.

Photo 2 - Osram G12 70W

In single-base cartridges, the cartridge is located on one side; double-base - double-sided, which allows it to be installed only in a horizontal position; The universal design can be installed both horizontally and vertically.

Most often, single-ended screw-type lamps are used, but double-ended lamps are considered more economical - their energy consumption is minimal.

Lamps are distinguished by burner type:

quartz;
ceramic.

IMPORTANT! Pay attention to the BLV MGL for the lines HITLITE, HIT-ULTRALITE, C-HILITE, TOPSPOT G12, TOPSPOT SHROUD, TOPSPOT G8.5, C-TOPSPOT, TOPLITE, TOPLITE SHROUD, TOPFLOOD.

Technical characteristics of MGL


Power	affects the luminous flux and brightness of the lamp; power - from 20 to 18000 W; supply voltage 220 and 380 V.
Base type	from destination - E27, E40, double-sided Rx7S, two-pin G12.
Light flow	Compared to traditional light bulbs (with a power 3-4 times higher), they tend to lose up to 30% of the luminous flux over time.
Colorful temperature	differ in shade: cold light is given by MGL around 6400 K, warm light - around 2700 K, 4200 K - neutral white.
Life time	at least 9000 hours.

Lamps according to GOST must be designed so that their characteristics are reliable when used correctly.

Operating principle of MGL

Photo 3 - TDM DRI 70 6000 K Rx7s SQ0325-0012

The operating principle is based on the passage of an electric arc discharge in a gaseous environment, similar to that used in mercury lamps. The gas used in MGL is mercury and inert argon. The sodium and scandium iodides present in the gas ensure the passage of the arc discharge.

These substances do not react with the lamp bulb material (quartz glass). In the absence of a discharge, halides cover the walls of the product with a film. When the contact is closed, the temperature rises and an arc discharge is observed, which promotes the evaporation of halides and their decomposition into iodine and metal ions.

The glow of the lamp, visible to the eye, causes the presence of ions in the gas. In this case, the movement of ions from the hot zone of the lamp to the colder walls is observed - the connections are restored and condensation occurs on the walls in the form of a film. The lamp operates on a closed cycle principle.

Connecting light bulbs

Connecting the lamp to the network is carried out according to the rules, due to the design features and operating principle of the MGL. The peculiarity is that they depend on voltage, so the lamps require the inclusion of a current-limiting element (ballast) in a sequential order.

Most MGLs operate with serial ballasts designed for gas-discharge lamps (mercury or sodium arc lamps). There are ballasts with a built-in IZU with the functions of igniting the light source and limiting the current.

Photo 4 - MASTER CDM-T 70W/942 G12 PHILIPS 871150019927015

As the lamp warms up, the voltage and current in it fluctuate, so special requirements are placed on the design and quality of the current-limiting element. Poor quality causes low voltage and when turned on the lamp will begin to go out.

How to check?

Photo 4 - HQI-TS 150W/NDL EXCELLENCE RX7s-24 OSRAM 4008321678386

You can check the performance of the MGL in the usual way - turn on the lamp: if it lights intermittently, the lamp is faulty. You should check that the connection is correct, perhaps this is the reason.

If the lamps show unstable operation - they light up, go out, cannot flare up to the full expected power - you need to measure the voltage in the network. Metal halide lamps operate unstable at a voltage of 190 V.

Please pay attention to the correct connection in the power cable connector: the connection is correct if the voltage is normal and the phases correspond to the designations.

You also need to check:

serviceability of the power cable (it may be broken);
whether the power supply was inserted into the track correctly;
correct connection to the panel.

If more than 20 lamps are mounted on a lighting structure consisting of several busbars, you should check whether they have enough power from the line supplying the structure. If the power is insufficient, unstable operation of metal halide lamps and ballasts (ballast control) is possible.

Base G9

Suitable for small metal halide lamps and equipped with two pins spaced 9mm apart. The socket is a socket with holes at the same distance, so installing a light bulb in a lamp looks like a regular plug-socket connection.

IMPORTANT! The service life of some types of modern MGLs reaches 15,000 hours. They are produced with different radiation colors and color rendering quality.

Photo 5 - HQI-T 400W/N E40 OSRAM 4008321526786

To turn on the lamp, special ignition devices are required, since a voltage of several kilovolts is required to ignite the discharge. MGL, like all gas-discharge lamps, can only operate with a ballast choke, which creates a phase shift between current and voltage, therefore power factor compensation will be required, that is, the inclusion of a compensating capacitor.

The power supply current for 12 V lamps is quite large.

The radiation spectrum is of great importance, especially in greenhouses for growing seedlings and plants. The ability to correct the spectrum from warm white to yellow distinguishes them favorably from the xenon discharge with its cool white color.

Shelf life of MGL

Photo 6 - TDM DRI 250 6000 K E40 SQ0325-0016

Depends on:

quality of quartz burners;
processing quality;
manufacturing company;
storage conditions.

For example, Lisma lamps have a shorter shelf life under equal conditions than Osram or GE. As a rule, if storage conditions are met, MGLs are stored for decades, the main thing is that they do not leak.

Application of MGL

MGL, like sodium, is used in industry for lighting or landscape design. Gas-discharge MGL is often used on streets, squares and parks in night lighting devices, to illuminate monuments or buildings.

Photo 7 -

It is an invariable attribute of stadium lighting, lighting design of circuses and arenas, office buildings and retail, advertising and other structures. Floodlight systems are the upper limit of power.

MGLs are not only plant-friendly, but also suitable for aquariums. A lamp with MGL provides high luminous flux and excellent color rendering throughout the entire operating period of the lamps.

MGLs are powerful lamps operating at high pressure and temperature. They are used with ballasts in special-purpose lamps. Typically, the MGL kit with built-in electronic ballasts includes a ballast starting device (required for arc lamps). Usually this is a large throttle and ignition device.

MGL power

Kinds	Peculiarities
	interior spaces, shop windows; color stability; wide range of uses; power 70 W; base g12; color temperature 4100K.
	for lighting large objects (stadiums, highways, shopping centers); in small rooms - for organizing lighting functions for photo and video areas, cages with animals and aquariums; base rx7s.
	for warehouse and industrial premises, external lighting of buildings; borosilicate glass tube equipped with a quartz burner; power 70 W; An appropriate inductor is required for connection.
	for lighting of domestic premises; high light output; long shelf life; color temperature 3000K; transparent or matte design of the flask; base E27.
	for external floodlighting, architectural lighting, internal lighting of industrial facilities, retail and commercial offices and premises; high light and color rendering; long service life.
	in lighting devices for internal and external lighting of shop windows, for large objects, museums, pavilions, sports facilities; powerful and compact light source; base - Rx7s.
150 W 4000K E27	for lighting shop windows, public buildings and offices, as decorative outdoor lighting, high luminous efficiency and color rendering; color stability and minimal reduction in luminous flux; used with ballasts; base E27; voltage 220V; color temperature 4000K (cool white light).
	used in combination with ballasts; high energy efficiency; base E40; lighting of open areas, industrial, agricultural and warehouse premises; for lighting open areas, agricultural, warehouse, and industrial premises.
	good color rendering and bright white light; ceramic burner and outer transparent tubular flask; used in combination with ballasts; high energy efficiency; 400 W E40 with stable color temperature; base E40.
	for lighting industrial workshops, large auditoriums, libraries, conference rooms, fair and exhibition pavilions, pedestrian areas, metro and railway stations; high pressure; tubular flask type; base E40; connects via ballast; color temperature 5500K (cold).
	for lighting shopping centers, city squares, residential and pedestrian areas, road lighting, as flood lighting; good color rendering and bright white light; ceramic burner and outer transparent tubular flask; used in combination with ballasts; high energy efficiency; long service life.
	used to illuminate large areas; service life 6000 hours; base E40; luminous flux 88000 lm; glow color - white.
	for lighting large public places - retail stores, spacious offices, lobbies, halls, airport terminals; power 100 W; color temperature 4300K; luminous flux 7800 lm; base E27; Long service life up to 15,000 hours.
GU6.5 20-35W	for creating accent lighting and lighting for retail store windows, for general and decorative lighting of premises and zoned outdoor lighting; miniature lamps with a simple base and ceramic burner; vibrant white light with a high color rendering index.

Optimal conditions for metal halide lamps

When igniting the MGL, the conditions are very important, which directly affect the type of ballast used with a specific type of lamp. MGL require to adjust the value:

ballast resistance current;
supplying the correct voltage to the arc-creating electrodes.

For ballast-lamp systems, ANSI standards contain values for all required parameters for all components. A starter operating from an alternating current network is also important for the ignition device. It differs in straightening parameter and size. Ballast for electromagnetic type starters.

An ignition unit is required in any arc discharge lamp. There are two types for MGL:

electronic ballasts (electronic);
EmPRA (electromagnetic).

Metal halide lamps (MHLs) are high-power lighting sources with relatively low energy consumption. Such devices are a type of high-pressure gas-discharge elements. The formation of a light flux occurs in the plasma of an arc discharge due to the fact that there are halides of certain metals inside the bulb.

How does a metal halide lamp work?

The main component of a metal halide lamp is the burner. This discharge vessel, made of quartz glass, emits harmful ultraviolet radiation during operation. To retain it, an external flask is used, inside of which the burner is located.

Another purpose of this outer shell is to reduce heat loss. The outer flask is made of resistant borosilicate glass. Also inside this element are mercury vapor and electrodes that create an arc discharge.

Operating principles of a metal halide lamp

MGLs are filled with halides - special additives in the form of inert gases. Complex compounds of cesium, rare earth metals and tin are used as emitting components. It is as a result of the occurrence of electrical discharges in metal vapor that glow occurs. Depending on the content of one or another inert gas inside the burner, the cost of a metal halide lamp is determined.

If the lighting element is inoperative, emitting additives settle on the walls of the discharge bulb. When the metal halide lamp is turned on, the surface of the burner heats up. As a result, the deposited chemical elements begin to evaporate and fall into the action zone of the arc discharge that occurs between the electrodes. Here the halides are exposed to high temperature and break down into ions. Due to the excitation of metal particles, a glow is formed.

Classification of metal halide lamps

Metal halide lamps can be classified depending on the power, color of the radiation, design and type of base.

The power of lighting sources can be as follows: 20, 35, 50, 70, 150, 250, 400, 700, 1000, 2000 and 3500 Watts. Each of these lamps requires its own mains voltage. Elements with a power of 2000 and 3500 W require 380 V to operate. And all other lighting sources, for example, a 400 W metal halide lamp, are connected to a network with a voltage of 220 V.

The color index of light sources varies from warm white at 3000 K to daylight at 6500 K. There are also colored metal halide lamps in the following shades: blue, green, orange and purple.

According to their design, these lighting elements can be baseless, single-base or double-base (soffit).

The base type can be as follows:

E27 and E40. Standard threaded form for lighting elements with power from 250 to 2000W.
G8.5 and G12. Used for light sources of low power, such as, for example, a 70W metal halide lamp.
RX7s. Used in lighting elements with two bases.

Connecting metal halide lamps

A metal halide lamp is not able to work if it is connected directly to the power system. In order for such a light source to function correctly, it is necessary to use a special ballast and a pulsed ignition device, since the lighting element operates from alternating current. The high-voltage discharge can be provided by an electronic or electromagnetic ballast.

The first option is preferable, because when used, the lamp service life increases, the emitted light is more even, and the current during start-up and operation is significantly reduced.

Advantages of metal halide lamps

Such lighting elements have the following advantages:

Disadvantages of metal halide lamps

The main disadvantages of these light sources include the following:

Significant heat generation. In this regard, it is recommended to install metal halide lamps at a certain height, and the more powerful the lamp, the greater this value.
Long ignition time. Low wattage lamps require about three minutes to reach maximum brightness, while higher wattage light sources require about ten minutes to achieve maximum brightness.
Impossibility of dimming. Metal halide lamps are not designed to be dimmable.
High price. Good light sources are more expensive than traditional incandescent lamps, but it is difficult to find replacements that are of suitable quality and at a lower price.

Metal halide lamps provide high-quality lighting and have good color rendering. Due to this, their scope of application is wide. Such lamps are used to illuminate both outdoor and indoor sports facilities, stadiums, industrial buildings, and concert halls. They are also used in shopping centers, hotels, restaurants, schools, offices and for architectural lighting of buildings.