LAMPS, REFLECTORS AND LUMEN REQUIREMENTS

−By Dhaval Shukla (141080119050)−Elements of Electrical Engineering−Mechanical Branch−2nd Semester

LAMPS According to principle of operation the light

sources may be classified as follows:1. Incandescent or Filament Lamp2. Halogen Lamp3. Fluorescent Lamp4. Metal Halide Lamp5. Sulfur Lamp6. Sodium Lamp7. Light Emitting Diode

LAMPS1. 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)

LAMPS2) High resistivity3) Low temperature coefficient of resistance4) Sufficient mechanical strength to withstand

vibrations during use5) 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.

LAMPSii. 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.

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.

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 Types2) Architectural use: In R7S3) 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

LAMPS3. 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.

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.

LAMPS Uses:1) In Kitchen, Basements or Garages2) For Stage Lighting purposes4. 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.

LAMPS Uses:1) General Lighting Purposes2) Automobile Headlights3) Photographic Lighting5. 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.

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

LAMPS6. 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.

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 Lights2) In Office Buildings

LAMPS7. 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.

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.

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.

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.

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.

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.

REFLECTORS4. 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.

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.

REFLECTOR7. 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.

LUMEN REQUIREMENTSType of lamp Lumen (per watt)

Incandescent 15 – 25Fluorescent 55 – 85Compact fluorescent light (CFL)

45 – 60

Mercury Vapor 50 – 60High pressure sodium vapor 75 – 130