Основы светотехники на английском языке (989259), страница 5

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A slight undervoltage considerably prolongs thelife, unfortunately at the cost of thelight current.Fundamental Principles of Lighting EngineeringLight Sources17Properties of filament lamps:•Luminous efficiency: 10 ... 15 lm/W•Life:The life of a filament lamp depends greatly on the luminous efficiency.

The average life of a filamentlamp is about 1000 h.•Light colour:The light colour is yellow-red. The reproduction of blue and green shades is too weak, of yellow andred shades too strong.•Lighting density:Filament lamp (40 W ... 100 W), clear glass:Filament lamp, matt glass:Opal lamp (argenta, silica):•Area of application:Filament lamps can be used for almost all purposes. Almost all requirements can be met by the widerange of powers and special lamps.•Vibration and impact resistance:Filament lamps with 115 V / 230 V are also manufactured as impact-resistant lamps. Lamps up to65 V are „insensitive to impact“ because of their very short helix.•Light waviness:Filament lamps above 40 W and at mains frequency no longer have any light waviness.•Inrush current:The inrush current of filament lamps may be many times the rated current.1.4.3100 ...

2000 cd/cm210 … 50 cd/cm21 … 5 cd/cm2Halogen filament lampsHalogen filament lamps are also temperature radiators similar to the filamentlamps. However, they operate at a higher temperature and therefore generatewhiter light with a colour temperature of 2800 to 3100 K. The higher temperature also causes a greater luminous efficiency up to 25 lm/W.These temperatures cause vaporising of the filament, however. To prevent thevaporised tungsten being deposited on the glass bulb, additives of iodine orbromide are contained in the glass bulb.

These create a recycling processwhich returns the tungsten-iodine mixture (tungsten-iodide) to the filament helix.>250 °C25341Because of the high temperatures of the filament helix and the small distancefrom the glass bulb, quartz glass is used.Halogen filament lamps are used mainly for car headlamps, slide projectors,daylight projectors, film projectors and in tube form for floodlights. They arealso suitable for lighting in film and TV production.Figure 1.4.3.1 shows the schematic diagram of the halogen recycling processof a halogen filament lamp.

The numbers mean:12345Tungsten helixGlass bulbIodine atomTungsten atomTungsten halogenideFigure 1.4.3.1Halogen filament lampFundamental Principles of Lighting EngineeringLight Sources18Figure 1.4.3.2 Overview of the designs of halogen filament lampsProperties of halogen filament lamps:•Luminous efficiency: 14 … 25 lm/W•Life:At rated voltage 1500 h ... 4000 h. Different voltages influence the life and light current considerably.•Light colour:The light colour is brilliant white, very similar to daylight, with a good colour reproduction.•Area of application:Can be used as car lamps, slide projectors, film projectors, daylight projectors, for lighting in film andTV productions and for floodlights.•Vibration and impact resistance:Halogen filament lamps with short helixes (projection lamps) are insensitive to vibrations.

Halogenfilament lamps with long helixes (floodlights) are more sensitive.•Light waviness:No visible light waviness at mains frequency.•Inrush current:The inrush current of halogen lamps may be many times the rated current.1.4.4Low-pressure discharge lampsAll gas discharge lamps have the same function in principle. They generate the light not by temperatureradiation but by a discharge process in ionised gases. These are usually metal vapours and/or rare gasesin a glass tube.1.4.4.1 Functional principle of fluorescent lampsA fluorescent lamp consists of a long stretched, rod-like glass cylinder.

A distinction is made between fluorescent lamps with a ballast and neon lamps with a stray field transformer.Fundamental Principles of Lighting EngineeringLight Sources19In practical lighting engineering the fluorescent lamp as a low-pressure discharge lamp is most important.Its advantages are:•••••••high luminous efficiencylong liferelatively low lighting densitywide choice of light coloursvery good colour reproduction propertieswide choice of types and powersvery good price/performanceFigure 1.4.4 shows that the discharge which takes place in the mercury vapour (low-pressure) at current,generates small light but a high UV radiation which causes the fluorescent coating on the insides of thetube to light.

The fluorescent coating of the tube absorbs this UV radiation and converts it into visible light.The composition of the fluorescent allows the light colour to be changed over a wide range.socket pinhelixfluorescentglass tubeHg-ionelectronHg-atompinch basesocket capFigure 1.4.4 Schematic diagram of the function of a fluorescent lampOperation of fluorescent lamps requires special electrical installations (ballasts). The consumed currentmust be limited by a choke for example. Igniters, usually glow igniters, are required to fire the dischargelamps which are prescribed by energy supply companies (compensation systems).Properties of fluorescent lamps:••Luminous efficiency:Table 1.4.4 shows colour reproduction stageand luminous efficiency of the most importantlamp types.

Three-band fluorescent lamps witha very high luminous efficiency and very goodcolour reproduction properties are often usedtoday.Life:Under normal operating conditions approx.8000 hColour reproduction stageLamp typeLight yieldη1A very goodde Luxe≤ 65 lm/W1Bthree-band96 lm/W2A gooduniversal white69 lm/W2Bstandard white83 lm/W3 averagestandard warmtone83 lm/W•Table 1.4.4Temperature dependence of the light current:The light current drops from temperatures< 20°C.

Cold-resistant fluorescent lamps should therefore be used for outdoor lighting.•Light colour:The light colour is chosen to suit the purpose and area of application, e. g. daylight, white, warm toneand deluxe warm tone.•Vibration and impact resistance:Impact-resistant fluorescent lamps are also manufactured, the shorter the helix the less sensitive thelamp is to impact.•Light waviness:An annoying stroboscopic effect may occur with moving or rotating solids. Suitable circuits (e. g.

duocircuits) can be installed to remedy this effect.•Inrush or start current:The inrush current of fluorescent lamps may be double the rated current (pre-heating current).20Fundamental Principles of Lighting EngineeringLight Sources•Re-ignition:Immediate re-ignition is possible at the end of the starter time.•Radio interference suppression:Interference capacitors are used to prevent radio interference.1.4.4.2 Start and ignition process of fluorescent lampsA starter has the job of building up a pre-heating circuitfor the start process, disconnecting it again after ignitionand at the same time generating high voltage surge witha choke.GThe glow starter shown in figure 1.4.4.2 basically consists of a glass tube filled with rare gas R and two bimetal strips B melted into it. When voltage is applied tothe starter, a glow discharge G is produced between thetwo bimetals which generates a certain heat so that thebimetal strips bend and touch each other.

This closesthe circuit and the lamp electrodes a re pre-heated. During this pre-heating time, the glow discharge is extinguished in the glass tube, the bimetal strips cool down,bend open and the circuit is open again.This process causes an induction voltage at the chokecoil with which the fluorescent lamp is ignited.BCThe built-in capacitor C serves for radio interferencesuppression and supports the ignition process additionally.Several ignition attempts are usually necessary until astable burning voltage has been set on the fluorescentlamp. The ignition process therefore usually takes about2 seconds. When the ignition process has ended, theburning voltage of the lamp stays much smaller than themains voltage and the glow discharge is no longer activated.

This means the starter remains off.Glow starters are cheap and are therefore used frequently.RThe disadvantages of glow starters are however: frequent ignition attempts at undervoltage which causes increased wear of the lamp electrodes as well as constantignition attempts when the lamp is deactivated and thestarter and choke are overloaded.Safety starters and electronic starters are also used often in addition to glow starters.Safety starters have an additional diode, an NTC resistorand a bimetal thermo-switch to the glow starter. Thisprotects the starter and the choke coil in fluorescentlamps which are unwilling to ignite.Figure 1.4.4.2 Schematic structure of a glowstarterIn electronic starters a ballast is used in place of the glow starter which causes immediate ignition of thefluorescent lamp. Control and monitoring of the starting process is taken over by an electronic circuit inthese starters.Fundamental Principles of Lighting EngineeringLight Sources211.4.4.3 Applications of different fluorescent lampsNot all fluorescent lamps can be used for every application depending on the lighting requirements withregard to economy, colour reproduction property and individuality of the light colour:•••Warm white (ww) is used where a warm, cosy atmosphere similar to the light of a filament lamp isdesired.Neutral white (nw) is between daylight white and warm white.

It is mainly used in work rooms.Daylight white (tw), with a strong blue-white light, is used where a cool lighting atmosphere is desired.Area of applicationDaylightneutral whitewarm whiteOsram11122021222530313241Philips86953384942529839382Office and administrationzOffices and hallways‹zConference roomszzIndustry, trade and commercezElectrical engineeringTextile productionz„Timber processingz„‹„z‹Steelworks and rolling millsGraphic art trade, laboratorieszz„‹z„Colour testing„‹Warehouses and despatchz‹Classrooms and training roomsLecture and classrooms, playschoolszzzLibraries and reading roomszzzzzzSales roomsFood halls, generalzzBread and confectioneryCool counters and refrigeratorszzCheese, fruit and vegetableszFishMeatTextiles and leatherOsram 76z„„Furniture and carpetsSports, toys and stationeryzz„„Photographic, watches and jewelleryz„zz„zz„z„„Cosmetics and hairdressing„FlowerszDepartment stores and supermarkets„zz„z„zCommon roomsRestaurants, pubs and hotelszTheatre, concerts halls, foyers,zEvent hallsExhibition hallszSports and multifunction hallszGalleriesz„z„‹z„z„zClinics and practicesDiagnosis and treatment roomsPatient wards and waiting roomsApartmentsLiving roomsKitchen, bathroom, hobby and cellarz„‹Outdoor lightingStreets, paths and pedestrian zonesTable 1.4.4.3‹‹„z„z22Fundamental Principles of Lighting EngineeringLight SourcesTable 1.4.4.3 gives an overview of the application possibilities of the different fluorescent lamps.

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