1. LAMPS, REFLECTORS AND LUMEN
REQUIREMENTS
−By Dhaval Shukla (141080119050)
−Elements of Electrical Engineering
−Mechanical Branch
−2nd Semester
2. LAMPS
According to principle of operation the light sources
may be classified as follows:
1. Incandescent or Filament Lamp
2. Halogen Lamp
3. Fluorescent Lamp
4. Metal Halide Lamp
5. Sulfur Lamp
6. Sodium Lamp
7. Light Emitting Diode
3. LAMPS
1. Incandescent Lamp:
− The figure L.1 shows the
Incandescent Lamp which are also
called Filament Lamp as they
consist of tungsten filament
between two lead wires.
− Tungsten filament has following
properties for which they are used
in this type of Lamp:
1) High melting point (3400 degree
Celsius)
4. LAMPS
2) High resistivity
3) Low temperature coefficient of resistance
4) Sufficient mechanical strength to withstand
vibrations during use
5) Ductility
− The light output of incandescent lamp decreases
gradually with age. This is due to two reasons:
i. Evaporation of the filament tends to cause the
bulb to blacken.
5. LAMPS
ii. Evaporation makes the diameter of the filament to
decrease slowly which increases the resistance of the
filament. Therefore, the old filament lamp draws less
current and operates at low temperature which reduces
the light output.
2. Halogen Lamp:
− In ordinary incandescent lamps, evaporated tungsten
mostly deposits onto the inner surface of the bulb,
causing the bulb to blacken and the filament to grow
increasingly weak until it eventually breaks.
6. LAMPS
− The halogen, however, sets up a
reversible chemical reaction cycle
with this evaporated tungsten.
− The halogen cycle keeps the bulb
clean and causes the light output to
remain almost constant throughout
the bulb's life.
− Halogen lamps are manufactured
with enough halogen to match the
rate of tungsten evaporation at
their design voltage.
7.
8. LAMPS
− Increasing the applied voltage increases the rate of
evaporation, so at some point there may be
insufficient halogen and the lamp goes black.
Uses:
1) Automotive Lamp Types
2) Architectural use: In R7S
3) Cooking: Special Halogen Ovens uses this lamp
to generate heat.
4) Home use: MR16 (10-50 Power-Watt ratings)
5) Stage Lighting: For lightening in theatre or studio
9. LAMPS
3. Fluorescent Lamp:
− A fluorescent lamp or a fluorescent
tube is a low pressure mercury-
vapor gas-discharge lamp that
uses fluorescence to produce
visible light.
− An electric current in the
gas excites mercury vapor which
produces short-
wave ultraviolet light that then
causes a phosphor coating on the
inside of the bulb to glow.
10. LAMPS
− As in all mercury-based gas-filled tubes, mercury is
slowly adsorbed into the glass, phosphor, and tube
electrodes throughout the life of the lamp, until it can no
longer function.
− The filaments can burn at the end of the lamp's lifetime,
opening the circuit and losing the capability to heat up.
− Both filaments lose function as they are connected in
series, with just a simple switch start circuit a broken
filament will render the lamp completely useless.
11.
12. LAMPS
Uses:
1) In Kitchen, Basements or Garages
2) For Stage Lighting purposes
4. Metal Halide Lamp:
− A metal-halide lamp is an electric
lamp that produces light by
an electric arc through a gaseous
mixture of
vaporized mercury and metal
halides (compounds of metals
with bromine or iodine).
− It is a type of high-intensity
discharge (HID) gas discharge lamp.
13.
14. LAMPS
Uses:
1) General Lighting Purposes
2) Automobile Headlights
3) Photographic Lighting
5. Sulfur Lamp:
− The sulfur lamp (also sulphur
lamp) is a highly efficient full-
spectrum electrode less
lighting system whose light is
generated by sulfur plasma that
has been excited by
microwave radiation.
15.
16. LAMPS
− The sulfur lamp consists of a golf ball-sized
(30 mm) fused-quartz bulb containing
several milligrams of sulfur powder and argon gas
at the end of a thin glass spindle. The bulb is
enclosed in a microwave-resonant wire-mesh cage.
Uses:
1) Reflectors
2) Light Pipes used in US Air Force museum
17. LAMPS
6. Sodium Lamps:
− A sodium-vapor lamp is a gas-
discharge lamp that
uses sodium in an excited state to
produce light.
− There are two varieties of such
lamps: low pressure and high
pressure.
− Low-pressure sodium lamps are
highly efficient electrical light
sources, but their yellow light
restricts applications to outdoor
lighting such as street lamps.
18.
19. LAMPS
− An amalgam of metallic sodium and mercury lies at
the coolest part of the lamp and provides the
sodium and mercury vapor that is needed to draw
an arc.
− The temperature of the amalgam is determined to a
great extent by lamp power. The higher the lamp
power, the higher will be the amalgam temperature.
Uses:
1) Street Lights
2) In Office Buildings
20. LAMPS
7. Light Emitting Diodes (LED):
− A light-emitting diode (LED) is a two-
lead semiconductor light source. It is
a PN-junction diode, which emits light
when activated.
− When a suitable voltage is applied to
the leads, electrons are able to
recombine with electron holes within
the device, releasing energy in the
form of photons.
− This effect is
called electroluminescence, and the
color of the light (corresponding to the
energy of the photon) is determined
by the energy band gap of the
semiconductor.
21.
22. LAMPS
Uses:
1) Visual Signals: To give signals or message which
can’t be directed through human-eye.
2) Illumination: Where light is reflected from objects
to provide information about it.
3) Measuring and interacting no human vision
processes.
4) Narrow band light sensors: LEDs operate in
reverse bias mode and respond to incident light,
instead of emitting light.
23. REFLECTORS
With most light sources, it is desirable
to use some additional equipment to
direct the whole of the light output on
to the surface to be illuminated, to
diffuse the light in order to prevent
glare or to change its color.
Various types of reflectors are
commonly used are described below:
1. Dispersive Type Reflector:
− A typical fitting of this type is shown in
the figure aside.
24. REFLECTORS
− It is considered a universal fitting for all types of
industrial uses.
− Such reflectors are constructed of heavy gauge
steel finished with vitreous enamel green outside
and white inside.
− They are type of the standard type of lamps from
60-1500 W.
− The spacing should be 1.5 times the height of
lamp filament above the working plane.
25. REFLECTORS
− It is combination of concave and
cylindrical reflecting surfaces in the form
of a deep bowl of wide dispersive
powder.
− It gives maximum intensity between 0-45
degrees.
2. Diffuser Type Reflectors:
− An industrial diffusing unit has a
slightly lower efficiency than dispersive
type reflector, but the appearance is
better and it is particularly useful to
minimize the glare reflected from
polished surfaces.
26. REFLECTORS
− The maximum light intensities are from 0-45 degrees.
− Uniform illumination is obtained with a space-height ratio
of one and a quarter one.
3. Concentrating Type Reflectors:
− In this type of reflector, the reflecting surface is
designed in the shape of a deep parabola.
− This type of reflector is suitable for high mounting
height as required in industries and shops.
− These reflectors are used for lamps from 60 to 1500 W.
27. REFLECTORS
4. Parabolitical or Elliptical Angle
Reflectors:
− Elliptical angle reflector is suitable for
side illumination.
− Normal overhead lamps cannot
provide illumination on vertical
surfaces. Hence these reflectors are
used for such applications.
5. Extensive Type Reflectors:
− These are constructed in steel with
vitreous enamel finish.
− The bowl is in the form of hyperbolic
curve.
28. REFLECTORS
− The maximum light intensities are obtained between 0-45
degrees.
− Spacing should be 1.5 times the mounting height.
6. Intensive Type Reflectors:
− This is similar to extensive type, the difference lying in
the shape of the reflector bowl which is a combination
of convex and concave curves.
− This is also a local lighting reflector.
29. REFLECTOR
7. Benflux Reflector:
− A wide distribution fitting is made in vitreous
enamel with a glass diffusing shade enriching the
lamp.
− Small apertures are left above the glass shade to
ensure adequate ventilation.
− Space-height ratio should be 1:2/3.
