3.1. LIGHTING SOURCES :
There are three (3) basic types of light sources used today; incandescent, fluorescent and high-intensity discharge lamps.
3.1.1 INCANDESCENT LAMPS :
- Incandescent lamps produce light by electrically heating high-resistance tungsten filaments to intense brightness.
- Overall efficacy ranges from about 15 to 23 lumens per watt.
- Lamp life ranges from 750 to 1000 hours for standard general purpose lamps.
- It is important that incandescent lamps conform to the supply voltage a change of only a few volts seriously affects both life and light output.
- Incandescent lamps emit the majority of the energy in the red and infrared area.
- Different types of incandescent lamps:
3.1.2. FLUORESCENT LAMPS :
- Fluorescent lamps produce light by establishing an arc between two (2) electrodes in an atmosphere of very low pressure mercury vapor in a chamber (the glass tube).
This low pressure discharge produces Ultraviolet radiation at wave lengths which excite crystals of phosphor (the white powder) lining the tube wall. The fluorescent phosphor powder convert the ultraviolet energy into visible (light) energy.
- Efficiency ranges from about 45 to 80 lumens per watt.
- Rated life ranges from about 7500 hours to 30,000 hours.
- Lamp performance is influenced by the character of the ballast and luminaire, line voltage, ambient temperature, burning hours per start and air movement.
- Control gear for fluorescent lamps
3.1.3. HIGH INTENSITY DISCHARGE LAMPS :
- High-intensity electrical discharge lamps produce light when a high pressure arc is passed through a gas vapor
-Three (3) types of lamps are of the high-intensity discharge type; mercury, metal halide and high-pressure sodium.
3.1.3.1 MERCURY LAMPS:
- The early mercury vapor lamps emitted a characteristically blue-green color of light, which was
practical only for industrial areas, street lighting, and general outdoor applications where color quality of the light was not too important.
- General lighting mercury lamps are now available in wattages from 50 to 1000 watts
- Typical efficiencies range from 30 to 63 lumens per watt, not including ballast power loss.
- "Clear" mercury lamps produce light rich in yellow and green tones but almost entirely lacking in red. Phosphor coated lamps provide improved color and have been
popular.
- TYPES OF MERCURY VAPOUR LAMPS :
3.1.3.2. METAL HALIDE LAMPS:
- This lamp employs iodides of sodium, thallium and indium, in addition to mercury, and results in a lamp design, which generates more than 50% more light than mercury lamps, and with a much better color quality.
- Metal halide lamps are similar in construction to mercury lamps. They differ in that the arc tube contains various metal halides in addition to mercury.
- They are available with either clear or phosphor coated bulbs from 175 to 1500 W.
- Present efficiency range from 70 to 125 lumens per watt, not including ballast power loss
-Compared to a clear mercury lamps, the metal halide additives improve the efficiency and color. Further color improvement is achieved with phosphor coatings
- Types of metal halide lamps :
3.1.3.3. HIGH PRESSURE SODIUM LAMPS:
- The high pressure sodium lamp has the highest light producing efficiency of any commercial source of white light.
- High pressure sodium lamps produce light by electricity passing through sodium vapor.
- They are presently available in sizes of 50 to 1000 W.
- Typical initial efficiencies are about twice that of mercury vapor: from 80 to 140 lumens per watt, not including ballast power loss.
-The color of light produced by this lamp is golden white.
- Types of high pressure sodium lamps :
3.2. LIGHTING SCHEMES :
Hi. I’m Designer of Mawsoo3a Blog. I’m Electrical Engineer And Blogger Specializing In Electrical Engineering Topics. I’m Creative.I’m Working Now As Maintenance Head Section In An Industrial Company.
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