MuSt ReFer OnCe...

2.  Natural Illumination:
• Sources of light existing naturally in the
environment.
• E.g. Sun, Stars, etc.
 Artificial Illumination:
• Produced Electrically.
• Steady output, aesthetic appearance,
clean, reliable and low-in-cost.

3.  Light: Electromagnetic Energy radiated from
a hot body or substance.
 Luminous Flux: Light energy emitted per unit
time. UNIT: Lumens
 Luminous Intensity: Intensity of emission of
luminous flux. UNIT: Candela
 Illumination: Phenomenon of light falling on
any surface.

4.  Direct Lighting:
• About 80% to 90% of the total light flux is made to
fall directly upon the working plane with the help of
suitable reflectors.
• Used for general outdoor lighting.

5.  60%-90% of the total light flux is made to fall
directly downwards with the help of semi-direct
reflectors.
 Remaining light is used for illuminate ceilings and
walls.
 Causes soothing brightness.

6.  60%-90% of the total light flux is thrown upwards to
the ceiling for diffused reflection by using inverted
reflectors.
 Used for indoor light decorations.

7.  More than 90% of the total light flux is thrown
upwards to the ceiling for diffused reflection by bowl
reflectors.
 Used in cinemas, hotels,
theatres, etc.

8.  Causes diffused and glare-less lighting, same
illumination in all directions.
 For this scheme, fluorescent lights are used.

9.  Aspects to be kept in mind:
• Adequate illumination
• Uniform light distribution all over the working plane.
• Light of suitable color.
• Minimum hard shadow and glare.

10.  Electric lamps :-
• Incandescent lamps
• Discharge lamps
 Incandescent lamps:-
• Vacuum lamps
• Gas filled lamps

11.  Vacuum Lamps:
• Current is passed through FILAMENT.
• Lamps are used below 40 W.
• Higher amount of light radiated.
• Heat energy is emitted, as wire glows.
 Gas Filled Lamps:
• The bulb filled with an inert gas-mostly N2 ,Ar.
• Used for 40W-500W.
• Low initial cost, low energy consumption &
convenience.
• Use coiled filaments.

12.  High & Low Pressure Mercury Lamps:
• Under low pressure, mercury lamps emit UV radiation.
• The pressure is increased we get light having bluish
tinge.
• Replaced by Sodium Vapour Lamps.

13.  Sodium Vapour lamps:
• Must operated at horizontal position to keep the
sodium uniform throughout.
• Efficiency=40–50 lumens per Watt
• Average life=about 3000 hours
• Not affected by voltage variations

14.  Neon Tube:
• Widely used for decoration & ads purposes.
• Can be bent into desirable shape
• Made to emit different colours like orange, red, etc. by
mixing chemicals with neon gas.
• Operating temperature=573 K
• Thus, are known as Cold Cathode Discharge Lamps.

15.  Compact Fluorescent Lamps.
 Compact size, saves space.
 Saves 70-80% energy.
 Life Is 10 times as compared to
incandescent lamps.
 Starting and working is flicker-free.

16.  Provides amenities to the workers & increasing
productivity ,avoiding accidents.
 200 Lumens/ m2 = day-light.
 Light of suitable colour must be distributed all
over the working plane.
 In large machine shops, the height of light must
be above level of machines.

18.  Mercury & Sodium lamps are suitable for this
purpose.
 Initial cost high, power consumption low.
 Economical compared to filament lamps.
 Used for clearly visible traffic, surrounding
,obstructions on road.
 Also for attractive look of area

20. Sr. No Class Of The Street Illumination (lux)
1. A1: Imp. Roads with heavy traffic 30
2. A2: Main roads with Mix Traffic, city streets,
etc.
15
3. B1: Roads like shopping streets, Localized
Traffic routes, etc.
8
4. B2: Secondary Roads with Light Traffic, By-
Lanes, etc.
4

21.  Images from Google.
 Reference Text: Elements Of Electrical
Engineering--- J. N. Swamy
 N. V. Sinha
 (8th Edition)