Основы светотехники на английском языке, страница 6

Thesymbols used have the following meanings:z„‹Three-band fluorescent lamps:de-Luxe fluorescent lamps:Standard fluorescent lamps:η = 96 lm/W, colour reproduction stage 1Bη = 65 lm/W, colour reproduction stage 1Aη = 83 lm/W, colour reproduction stage ≤ 21.4.4.4 Sodium vapour low-pressure lamps (Na lamps)The highest luminous efficiency can be achieved with sodium vapour low-pressure lamps (183 lm/W). Thespectrum of Na lamps consists only of monochromatic yellow light with a wavelength of λ = 589 nm whichis close to the brightness sensitivity of the human eye.Figure 1.4.4.4 shows the normal structure of an Na lamp. Na lamps usually comprise a U-shaped dis-3charge tube in which the discharge takes place at a pressure of 10 mbar.

The sodium is solid metallic inthe cold state of the lamp and must first be vaporised by the effect of heat during the starting process.First an auxiliary discharge is introduced with neon gas (reddish light colour). After a relatively long burn-intime of about 10 to 15 minutes the sodium is fully vaporised and the lamp reaches its rated light technicalvalues.

The discharge tube may reach a temperature of up to 350 °C and must therefore be insulated withan external vacuum bulb for reasons of heat protection.outside bulbdischarge tubeFigure 1.4.4.4 Structure of a sodium vapour low-pressure lampThese small 18 W lamps are immediately re-ignitable in the hot state. Lamps with a greater power (from35 W) require a cooling time of a few minutes.A special choke coil with a tap and an ignition capacitor (5 µF) are required for operating small 18 Wlamps. Lamps with greater powers (up to 180 W) require a higher voltage (500 V to 600 V) than the mainsvoltage for ignition. Stray field transformers which also limit the current to its rated value are usually usedto achieve these ignition voltages.Sodium vapour low-pressure lamps are used, because of their monochromatic light, where it is not necessary to distinguish colours such as street lighting, lighting systems in heavy industry and illumination ofbuildings.Properties of sodium vapour low-pressure lamps:•Luminous efficiency:max.

183 lm/W•Life:approx. 10000 h•Start time:approx. 10 min•Light colour:simple yellow lightFundamental Principles of Lighting EngineeringLight Sources1.4.523High-pressure discharge lampsUnlike low-pressure discharge lamps, high-pressure discharge lamps operate from approx. 0.3 bar to10 bar. The discharge vessels are shorter and have a smaller volume with a high lighting density. Examples of high-pressure discharge lamps are:xxxSodium vapour high-pressure lampsMercury vapour high-pressure lampsHalogen metal vapour lampsBecause of the high vapour pressure and the hot re-ignition, these lamps can only be ignited with specialignition devices. The operation and function are basically the same as the low-pressure discharge lamps.All lamps require start-up times of a few minutes.Please bear in mind that lamps with a high light yield have poor colour reproduction properties and lampswith a low light yield good colour reproduction properties.1.4.5.1 Sodium vapour high-pressure lampsSodium vapour high-pressure lamps are available in three versions (figure 1.4.5.1.1):1.

Tubular form with clear glass bulb (figure 1.4.5.1.2):6 power stages:50 W ... 100 W2Ligting densities:up to 600 cd/cmLight currents:up to 130 klmLuminous efficiency:up to 140 lm/W2. Festoon form with clear glass bulb, can only be used inhorizontal position:3 power stages:70 W ... 400 W2Lighting densities:up to 550 cd/cmLight currents:up to 48 klmLuminous efficiency:up to 120 lm/W1burnerAl2O333. Elliptical form with coated outside bulb forreducing the lighting density:8 power stages:50 W ... 1000 W2Lighting densities:up to 30 cd/cmLight currents:up to 120 klmLuminous efficiency:up to 120 lm/WThe vapour pressure in these lamps is about 0.25 bar, aburner temperature of about 1200 °C. The discharge tube ismade of ceramic, high-sintered aluminium oxide Al2O3.

Immediate re-ignition is only possible in the festoon form with special high-voltage ignition devices. Lamps in tubular and elliptical form re-ignite within a few minutes when normal ignitiondevices are used.In certain lamp types with the appropriate ballasts, it is possible toreduce the power for night-timeoperation. These lamps start upbest at rated power.

In reducedpower operation the light colourbecomes yellower and the colourreproduction is poorer.2Figure 1.4.5.1.1 Designs of sodium vapour high-pressure lampsFigure 1.4.5.1.2 Sodium vapour high-pressure lamp in tubular form24Fundamental Principles of Lighting EngineeringLight SourcesProperties of sodium vapour high-pressure lamps:•Luminous efficiency:40 ...

150 lm/W depending on design•Life:approx. 10000 h•Start time:4 min … 5 min•Light colour:warm white (ww), colour temperature approx. 2200 K, colour reproductionstage 2 to 4•Power:50 W ... 1000 W•Applications:Street lighting, squares and parks1.4.5.2 Mercury vapour high-pressure lampsMercury vapour high-pressure lamps are very cost-effective due to their long life and relatively high lumiUNnous efficiency. No ignition devices are necessaryto operate them which makes them easier to install.Figure 1.4.5.2.1 shows the principle structure ofmercury vapour high-pressure lamps.

Thee light isgenerated in a quartz glass discharge tube. Thedischarge (auxiliary discharge) is induced by anauxiliary electrode (with bias resistor) and argongas. Mercury is used as a filling gas for generatingthe light. This produces so many charge carriersthat the discharge between the main electrodescan also ignite (main discharge). The mercurywhich is vaporised during the start-up process bythe discharge heat generates the full light currentafter about 3 to 5 minutes.

The pressure of the discharge tube is between 2 bar and 9 bar.Dglass bulbdischargetubewarm whitelightHEIn the event of power failures > 10 ms the discharge is extinguished and the lamp can only reignite after a cooling time of a few minutes.The operating current is limited by a choke coil. Anignition device is not necessary in these lamps because the mains voltage is sufficient for ignition.However, a ballast is always needed.Mercury vapour high-pressure lamps are availablein three versions (figure 1.4.5.2.2):1. Elliptical form:nw for road lighting and factory hall lighting, wwfor representative traffic zone lighting, pedestrian zones, foyers, shopping malls, rooms forthe public, effective lighting with downlights andwall washers.2.

Reflector and mushroom form with directedlight current and light colour ww or nw. Together with a choke, these lamps can also beused instead of filament lamps, e. g. for illuminating plants.3. Spherical form with golden-brown filter coatingfor decorative indoor and outdoor lighting.Ewhite lightfluorescentfilter coatingFigure 1.4.5.2.1 Structure of mercury vapour highpressure lamps123Figure 1.4.5.2.2 Designs of mercury vapour highpressure lampsFundamental Principles of Lighting EngineeringLight Sources25Properties of mercury vapour high-pressure lamps:•Luminous efficiency:32... 58 lm/W•Life:approx.

15000 h•Start time:approx. 3 min ... 4 min (ballast required).•Light colour:bluish-white with high yellow and green content, low colour reproduction•Lighting density:approx. 4 cd/cm in small lamps, up to 16 cd/cm in large lamps•Power:50 W ... 1000 W221.4.5.3 Incandescent arc lampsIncandescent arc lamps are a combination of mercury vapour highpressure lamp and filament lamp in a common glass bulb. The helixacts as a bias resistor and is connected in series with the mercuryfilled discharge tube as shown in figure 1.4.5.3 which means that noballast is required. The inside of the outer glass bulb is coated with afluorescent material which converts the UV light of the mercury discharge into longer wave light with neutral white light colour and average colour reproduction property.GWZEZWLHgfilament helixignition electrodeignition resistorfluorescent materialmercury vapour discharge vesselGWProperties of Incandescent arc lamps:ZWAbbreviations in figure 1.4.5.3:ZE•Luminous efficiency:10 ...

28 lm/W•Life:approx. 5000 h•Light colour:similar to daylight•Start current:up to 1.5 times the rated currentIncandescent arc lamps can be used without any problem in existinglights in place of filament lamps of the same power. They are therefore used mainly for modernising existing systems (e. g. factory installations, street lighting, sports fields, etc.HgLFigure 1.4.5.3 Structure of a incandescent arc lamp1.4.5.4 Xenon high-pressure lampsXenon high-pressurelamps (figure 1.4.5.4) arealso gas dischargelamps. The dischargevessel is made of quartzglass and is filled with therare gas xenon under afew atmospheres ofpressure.electrodequartz glass bulbFigure 1.4.5.4 Structure of a xenon high-pressure lampelectrodesocket26Fundamental Principles of Lighting EngineeringLight SourcesThe lamp is installed in a protective housing because of the high gas pressure and the very short-waveradiation.Xenon high-pressure lamps are usually used on DC voltage. They need their own high-frequency ignitiondevice for ignition.

The lamps can be re-ignited immediately after switching off.Xenon long arc lamps have greater rated powers, e. g. 6 kW, 10 kW and 20 kW. They are used for illuminating large areas (e. g. floodlight systems).Properties of xenon high-pressure lamps:•Luminous efficiency:20 ... 25 lm/W•Life:approx. 1200 h ...