PPP/AITRC/UEE/22626 Department of Electrical Engineering (Polytechnic)

Topic 1: Illumination
Contents:
 Definition of Light , Luminous flux, Intensity, Lumen, Candle Power, Illumination, Lux or meter
Candle, MHCP, MSCP, MHSCP, Reduction factor, lamp efficiency, Specific Consumption, Glare,
Space-Height ratio, Utilization Factor, Maintenance Factor , Depreciation Factor, Waste light Factor,
Absorption Factor & Reflection Factor, Solid Angle.
 Working principle, Construction, Operation and applications of: Fluorescent Tube, CFL, Mercury
Vapour, Sodium Vapour and Metal Halide lamps
 Types of Lighting Schemes: - direct, Semi-Direct, Indirect & semi- Indirect lighting Schemes with
Applications.

4. Illumination
Winter 2014
1. Describe with neat diagram construction and working of high pressure mercury
vapor discharge lamp.
2. State and explain laws of illumination.
3. Define the following terms related to illumination:
1) Utilization factors
2) Maintenance factors
3) Depreciation factor and
4) Luminous efficiency.

Summer 2015
1. State the laws of illumination.
2. Describe the construction of high pressure mercury vapour lamp with neat sketch.
3. Describe through illustration following types of lighting scheme:
i) Direct lighting ii) Indirect lighting.
Winter 2015
1. Define the following terms: i) Luminous intensity ii) Lumen iii) Candle power iv)
Waste light factor.
2. Explain the operating principle and working of a fluorescent lamp. Mention the
function of following components:
i) Electrodes ii) Choke iii)Capacitor in glow type starter iv) Capacitor connected
across input terminals.
Illumination
PPP/AITRC/UEE/22626 Department of Electrical Engineering (Polytechnic)

3. Draw the following types of lamp fittings and lighting systems with the help of
light distribution graphs and its applications:
i) Direct lighting ii)Indirect lighting iii)Semi-direct lighting iv)Semi-indirect
lighting
Summer2016
1. Define:i) Luminous flux ii) Luminous intensity iii) Space to height ratio
iv) Utilization factor.
2. State the laws of illumination.
3. Explain in brief the construction and working of sodium vapour lamp.
SQP
1. Describe through illustrations the following types of lighting scheme: (i) Semi-
direct (ii)Semi-indirect.
2. Define the following terms related to illumination systems:
i) Utilization factor ii) Depreciation factor iii) Space to height ratio iv) Absorption
factor
3. State any four salient features of sodium vapor lamp.
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1) Light (Q):-
It is defined as the radiant energy from a hot body that produces the visual sensation upon the
human eye. And it is expressed in lumen-hours or analogous to watt-hour and its unit is „Q‟
OR
That part of radient energy from a hot body which produced the visual sensation on human
eye is called light

2) Luminous flux (F):-

The total energy radiated by a source of light in all directions in unit is called
Luminous flux. And its unit is Lumen
OR
Luminous flux is commonly called light output and is measured in lumens (lm).

Illumination
PPP/AITRC/UEE/22626 Department of Electrical Engineering (Polytechnic)

3) Lumen:
It is defined as the luminous flux emitted by a source of one candle power per unit solid angle in
all directions OR
It is unit of luminous flux. One lumen is defined as luminous flux emitted per unit solid angle
from a point source of candle power.

4) Candle power:
The candle power is the radiation capacity of the light source in the given direction. The
candle power is always given in lumens output per unit solid angle of the given light source.
Lummens
C.P  , ( Where w  Solid Angle)
w
5) Luminous intensity:-
The luminous intensity in any particular direction is the luminous flux emitted by source
per unit solid angle is called the luminous intensity of the source. And its unit is Candela


OR I  (Where   lu min ous flux , w  Solid Angle)
w
14) Glare:
Glare is defined as, which causes discomfort and interference in vision due to more brightness and
improper angle to human eyes. OR
Glare is defined as the brightness within the field of vision of such a character so as to cause
discomfort and interface in vision
6) Illumination:-
The illumination is defined as the luminous flux falling on per unit area of the given surface
on the working plane OR
When light falls on surface, it becomes visible, this phenomenon is called as illumination
The unit Illumination is lumens/ m2 or lux
7) Lux :-
It is unit of illumination and it is defined as luminous flux falling per unit area
8) MHCP (Mean Horizontal candle Power (MHCP) :
MHCP is defined as the mean of the candle power of source in all directions in horizontal plane

Illumination
PPP/AITRC/UEE/22626 Department of Electrical Engineering (Polytechnic)

9) MSCP (Mean Spherical Candle power):

It is the average of all candle powers in all direction in all planes.

OR

Total Lu min ous lux in lumens

MSCP 
4

10) MHSCP (Mean Hemispherical candle Power (MHSCP) :

MHSCP is defined as the mean of the candle power of source in all directions above or below
the horizontal plane.
OR

Total lux emitedinHemispher

MHSCP 
2
11) Reduction Power:
It is ratio of mean spherical candle power to the mean horizontal candle power.
M S CP
Re ductio Power ( factor) 
M HCP
12) Lamp η (lamp efficiency):-
It is defined as the ratio of the total luminous flux emitting from the source to
Its electrical power input in watts.
13) Specific Consumption:
It is defined as ratio of electrical power input to its average candle power.
15) Space-Height ratio:
Space between lamps
Space height ratio 
Height of lamps above working plane

16) Utilization factor:-

It is defined as the ratio of total lumens reaching the working plane to the total
lumens given out by the lamp. Its value is always less than one.

17) Waste light factor:

When a surface is illuminated by several numbers of the sources of light, there is certain
amount of waste due to overlapping of light waves,
The waste of light is taken into account depending upon the type of area to be illuminated.
The value of waste Light factor 1 to 1.5
18) Absorption factor:

Illumination
PPP/AITRC/UEE/22626 Department of Electrical Engineering (Polytechnic)

Total lumens after absorption

Absorption Factor 
TotalLumens given out by the lamp
Its value is always less than one.

19) Reflection factor:-

It is defined as the ratio of luminous flux leaving the surface to the luminous flux incident on it.
OR
Re flected light
Re flection factor 
incident light
Its value is always less than one

20) Maintenance factor ( Light loss factor):-

It is defined as the ratio of illumination under normal working conditions to the
illumination when everything is clean. OR
Illu min ation under normal working condition
Ma int enacefactor 
Illu min ation under every thing is clean

Its value is always less than one.

21) Depreciation Factor:

It is defined as the ratio of initial illumination to the ultimate maintained illumination on
the working plane. OR
1
Depreciati on factor 
Ma int ennace Factor

Its value is always more than one.

22) Solid angle:-
It is the ratio of area of the surface to its square of radius of sphere.

23) Plane Angle

It is the ratio of length of arc to its radius

Illumination
PPP/AITRC/UEE/22626 Department of Electrical Engineering (Polytechnic)

24) Quality of Light:

This means that the illumination should not be harmful to the viewers. It should be galre free, Shadow
less and contrast free

25) Colour Rendering Index (Ra):-

Colour rendering is the ability of a light source to show surface colours as they should be at
actul.
The colour rendering index (Ra) scale from 0 to 100: a value of 0 means it is impossible to
discern colours at all, while a score of 100 means no colour distortion (i.e. at actul).
(CRI below 50 Poor, CRI 50-70 Fair, CRI 70-80 Good and CRI 80-90 Excellent)

State the laws of illumination.

Inverse Square Law:-

Intensity of illumination produced by a point source varies inversely as square of the distance
from source.

Illumination
PPP/AITRC/UEE/22626 Department of Electrical Engineering (Polytechnic)

I
E 
d2
Where,
I = intensity and d = Distance

Lamberts Cosine Law:

According to this law, Illumination at any point on a surface is proportional to the

cosine of the angle between the normal at that point and the direction of luminous flux

What factors should we consider while designing the lighting scheme? / State and explain the factors
to be considered while designing lighting scheme.
Illumination
PPP/AITRC/UEE/22626 Department of Electrical Engineering (Polytechnic)

List Factors designing a lighting scheme:

1. Designe illumination scheme should be very simple.

2. Area of the working plane.
3. Find out application of working plane
4. Decided lux level on working plane as per application.(Illumination level)
5. Find out total lumens required on working plane.
6. Decide the type and wattage of lamp which is to be used for that particular application
7. Quality of light
8. Assume waste light Factor
9. Assume utilization Factor
10. Assume deprecation Factor
11. The illumination scheme is designed in such a way that there should be less glare.
12. The illumination scheme is designed in such a way that there should be minimum shadows.
13. The control of light intensity is possible.
14. Assume the illumination efficiency of those specific lamps which are to be used.
15. To provide safety and prevent accident.
16. Take care to achieve desired energy saving.
17. Choose lamp with higher luminous efficiency, better color, and longer life
18. For any type of illumination scheme the maintenance & repairing should be less.
19. The cost of the designed illumination scheme should be low.

Recommended lux levels :

Illumination
PPP/AITRC/UEE/22626 Department of Electrical Engineering (Polytechnic)

What are different characteristics are to be considered when choosing a lamp for an application.

Following characteristics are to be considered when choosing a lamp for an application.

1) Luminous efficacy
2) Total luminous flux
3) Lamp power and ballast losses
4) Lamp life
5) Lumen depreciation during burning hours
6) Quality of light
7) 7.Correlated color temperature(CCT)
8) 8.Color rendering index
9) 9.Effect of ambient circumstances
10) Voltage variations
11) Ambient temperature
12) Switching frequency
13) Switch-on and restrike time
14) Lamp size, weight and shape
15) Auxiliaries needed (ballast, starter, etc.)
16) Purchase and operation costs
17) Lamp life

Illumination
 PPP/AITRC/UEE/22626 Department of Electrical Engineering (Polytechnic)

State the factors which affect the amount of light reaching the work plane

Many factors affect the amount of light reaching the work plane are as below:

1. The size and proportion of the room.

2. The height of the light fixtures above the work plane.
3. The reflectance of wall and ceiling surfaces.
4. The nature of the light fixture and its distribution of light.
5. Light loss due to ageing, dust collection and yellowing.
6. Atmospheric particles such as smoke or dust

Explain effect of each of following on design of illumination .

The following points if not considered result in inadequate / improper illumination design.

i) Shadows: - Shadows should be minimum.

ii) Glare: - Glare should be minimum.

iii) Uniformity: - uniform distribution of light throughout the working plane.

iv) Colour of light: - Choose fitting which produces colour like a day light e.g. Fluorescent tube

State Different types of lighting schemes / List different types of lightings used for interior
illumination and explain any one in detail.

Lighting schemes are classified according to the location, requirement and purpose etc. are as under

1. Direct lighting

2. Indirect lighting

3. Semi direct lighting

4. Semi indirect lighting

5. General lighting

Illumination
PPP/AITRC/UEE/22626 Department of Electrical Engineering (Polytechnic)

1. Direct lighting:

As is clear from the name, in this system almost 90 to 95 % light falls directly on the object or
the surface. The light is made to fall upon the surface with the help of deep reflectors. Such type of
lighting scheme is most used in industries and commercial lighting. Although this scheme is most
efficient but it is liable to cause glare and shadows.

2. Indirect lighting:

In this system, the light does not fall directly on the surface but more than 90 % of light is
directed upwards by using diffusing reflectors. Here the ceiling acts as a source of light and this light
is uniformly distributed over the surface and glare is reduced to minimum. It provides shadow less
illumination which is useful for drawing offices and composing rooms. It is also used for decoration
purposes in cinema halls, hotels etc.

3. Semi direct lighting:

Illumination
PPP/AITRC/UEE/22626 Department of Electrical Engineering (Polytechnic)

This is also an efficient system of lighting and chances of glare are also reduced. Here
transparent type shades are used through which about 60 % light is directed downward and 40 % is
directed upward. This also provides a uniform distribution of light and is best suited for room with
high ceilings.

4. Semi indirect lighting:

In this system about 60 to 90 % of total light is thrown upward to the ceiling for diffused
reflection and the rest reaches the working plane directly. A very small amount of light is absorbed
by the bowl. It is mainly used for interior decoration.

5. General lighting:
This system employs such type of luminaries, shades and reflectors which give equal
illumination in all the directions. This method is commonly used in various residential, commercial
and Industrial installations
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Illumination
PPP/AITRC/UEE/22626 Department of Electrical Engineering (Polytechnic)

Electrical Method of Producing Light:

Following are the methods of produces Light:

1. By developing arc between two electrodes.

2. By passing a current through a filament
3. By Electric discharge through vapors or gases

Comparison between different lamps

Illumination
PPP/AITRC/UEE/22626 Department of Electrical Engineering (Polytechnic)

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1. Construction and operation of FTL (Fluorescent tube light) :-

Construction:-
Fluorescent tube consists of tube, choke, starter & power factor improvement capacitor.

Function:

i) Choke: For providing high voltage at the time of starting and limit the current.

ii) Starter: To make and break the circuit to start the tube.

iii) Capacitor: To improve the power factor, To minimize the radio interference.

The colors produce by this tubes are as:

S.No Material Color

1 Zinc silicate Green
2 Calcium tungsten Blue
3 Cadmium borate Pink
4 Calcium Holo phosphate White or day light
5 Magnesium tungsten Bluish white

Operation:
 When switch is ON current flows through the choke.
 At that time choke induces high voltage which is applied to two filaments
 Due to this there will be ionization so that light will be emitted through the tube.

Advantages:
1.Voltage fluctuation has very small effect on light output.

Illumination
PPP/AITRC/UEE/22626 Department of Electrical Engineering (Polytechnic)

2.The luminous efficiency is more as length of rod is more.

3.It gives light close to natural light.
4.Heat radiations are negligible.
5.Long life

Disadvantages:
1. Its brightness is less.
2. Initial cost is more
3. Overall maintenance cost is high.
4. Stroboscopic effect
5. Contain mercury (A single FT contains enough mercury to pollute more than 30,000 liters of
water.) so not to be disposed of like normal waste
6. Light output decreases with age
7. Need of auxiliary ballast and starter

CFL

Construction:-
 CFL is basically a low pressure mercury vapor lamp having two electrodes placed in a glass
tube.
 The tube is coated internally with some fluorescent material in the form of powder.
 In the tube one drop of mercury and argon gas is filled at low pressure.
 And consist of an electronic ballast circuit

Operation:-

 The electronic ballast circuit takes a 220 V input from external power source and sends high

frequency supply is applied to that two terminals of CFL

 This ionizes the argon and mercury vapor particles.

 The ionized particles emit ultra violet radiations which strike with the fluorescent layer of

material coated on the tube.

 In turn, fluorescent material spread a white light which lights up the room.

Illumination
PPP/AITRC/UEE/22626 Department of Electrical Engineering (Polytechnic)

Advantages of CFL:-
1) Available in any shape
2) Power consumption is less
3) Illumination efficiency is high
4) Life in working hours is large as compare to incandescent lamp.
5) Compact tube size as compare to fluorescent tube.
6) Can be available in various colours.
7) Smooth light and low maintenance.
8) Low running cost
9) Attractive look
10) High color rendering index (CRI)
11) No stroboscopic effects.
Disadvantages of CFL:-
1. Glare is more
2. Ultra violet rays more
3. Lux level reduces due to ageing.
4. High cost
5. Contain mercury

Size and ratings:-

These lamps are available in different sizes and designs. They have single rod, double rod,
triple rod or spiral rod. These lamps are available in different power rating e.g. 5, 7, 9, 11, 18 and 24
watt, 220 V

CFL Applications:-

Excellent applications for fixtures utilizing CFL Lamp sources are Residential, retail stores,
warehouses, distribution centers, light manufacturing, gymnasiums, food processing, wet location, and
hazardous applications.

Why CFL Lamps are becoming more popular nowadays? Discuss technically.
Illumination
PPP/AITRC/UEE/22626 Department of Electrical Engineering (Polytechnic)

Because of following Advantages CFL lamps becomes more popular:-

2) Available in any shape
2) Power consumption is less
3) Illumination efficiency is high
4) Life in working hours is large as compare to incandescent lamp.
5) Compact tube size as compare to fluorescent tube.
6) Can be available in various colours.
7) Smooth light and low maintenance.
8) Low running cost
9) Attractive look
10) High color rendering index (CRI)
11) No stroboscopic effects
12)

Explain construction of high pressure mercury vapor discharge lamp with neat sketch.

Construction:-
 MV lamps consist of an arc tube (inner) enclosed by an outer tube.
 Vacuum is created between the inner & outer glass tube to prevent heat loss/ the space
between the two is filled with nitrogen.
 The inner bulb contains neon or argon gas with certain quantity of mercury.
 Arc tube also contains two electrodes and starting electrode.
 It requires a ballast to give high voltage at staring to produce the arc.
 The capacitor is used to improve the power factor.
Illumination
PPP/AITRC/UEE/22626 Department of Electrical Engineering (Polytechnic)

Operation:
 When the lamp is turned on, a high voltage at staring is applied, lamp start with a small arc
between the starting electrode and the main electrode,
 An arc which discharges through argon gas (starting gas) and vaporizes mercury vapor
 The energized mercury vapor atoms emit light.
 After 5 minutes, the lamp gives full light.
 It gives greenish blue color light
OR

 Advantages of high pressure mercury vapor lamp.

1) Good luminous efficiency.

2) Long life

3) Compact size

4) Clear white light output

5) Color rendering is better than that of high pressure sodium street lights

6) Suitable for indoor & outdoor applications

 Disadvantages of high pressure mercury vapor lamp

1) Starting time is more.

2) Initial cost is more

3) Stroboscopic effect is more

4) The disposal of mercury vapor lamps will require special disposal methods because of
the mercury inside the lamp.

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PPP/AITRC/UEE/22626 Department of Electrical Engineering (Polytechnic)

5) Use of MV Lamps should be discouraged (Avoided).

6) They are no more efficient than MH lamp, SV lamp.

Colours:

It gives greenish blue color light

Applications:

1. Replacing incandescent lamps

2. General indoor lighting
3. General outdoor lighting
4. Security lighting
5. Parking lots
6. Aquarium lighting
7. Landscape lighting
8. Plant lighting
9. Factories and gymnasiums lighting
10. Workshops, halls, hangars, Factory floors

Such lamps are typically not used in retail stores, schools, hospitals and other similar
commercial applications.

Construction and principle of operation of sodium vapour lamps :

Sodium Vapour Lamp diagram:

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PPP/AITRC/UEE/22626 Department of Electrical Engineering (Polytechnic)

Construction

 HPS lamps consist of an arc tube (inner) enclosed by an outer tube.

 Vacuum is created between the inner & outer glass tube to prevent heat loss.
 The arc tube is made from a special glass that can withstand to high temperatures
 Arc tube is U Shape
 The arc tube contains xenon / neon gas (starting gas), sodium and mercury and two electrodes.
 IT require a ballast to give high voltage at staring to produce the arc (The ballast provides a high-
voltage pulse (2,500 V) for one microsecond for lamp start.)
 There is an igniter which sends a pulse to start the discharge.
 To improve the power factor a capacitor is connected across the supply. (P.F. is low @ 0.3 lag.)
 HPS lamps do not have starting electrodes.

Working Principle:

 When the lamp is turned on, a high voltage at staring is applied across two electrodes, to initiate
an arc which discharges and vaporizes xenon /neon gas (starting gas), sodium and mercury.
 The energized metal atoms emit light.
 After 2 to 5 minutes lamp will glow 100 %.
 For running the lamp low voltage of about 165 v is sufficient.
 The color of light produce is yellowish.

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PPP/AITRC/UEE/22626 Department of Electrical Engineering (Polytechnic)

Types:-

There are two types –

1. Low pressure S.V. lamp

2. High pressure S.V. lamp

Colour of light:

1. It produces yellowish light

Application:

1. All applications where colour is less not important.

2. Mainly used for street lighting

3. Floodlighting

4. Area lighting

5. Airport lighting

6. Parking lots

7. Industrial lighting

8. Ideally suited for fog, dust and rainfall condition

Rating: - 50 w, 70w, 100w, 150w, 250w, 400w, 600w, 1000w

Metal Halide lamp:

Illumination
PPP/AITRC/UEE/22626 Department of Electrical Engineering (Polytechnic)

Construction is similar to mercury lamp.

 MH lamps consist of an arc tube (inner) enclosed by an outer tube.
 Vacuum is created between the inner & outer glass tube to prevent heat loss.
 The inner arc tube contains the electrodes and various metal halides, along with mercury and
inert gases that make up the mix.
 MH lamp has three electrodes – two for maintaining the arc and a third internal starting electrode
 OR Pulse-start MH lamps do not have a starting electrode. An igniter in the pulse start system
delivers a high voltage pulse (typically 3 to 5 kilovolts) directly across the lamp‟s operating
electrodes to start the lamp
 IT require a ballast to give high voltage at staring to produce the arc
 The capacitor is used to improve the power factor.

Operation:
 When the lamp is turned on, a high voltage at staring is applied across two electrodes, to initiate
an arc which discharges and vaporizes argon gas (starting gas), mercury vapor and chemical
components called “metal halides”
 The energized metal atoms emit light.
OR

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 PPP/AITRC/UEE/22626 Department of Electrical Engineering (Polytechnic)

Advantages of Metal halide lamp:

1. Metal halide generates light closer to day light.
2. High quality white light
3. Low running cost
4. High Efficiency
65-115 lumens per watt.
5. Long Life Metal halide lamps have an average life of 15,000-20,000+ hours.
6. Metal halide lamps are relatively unaffected by ambient temperature.
7. Metal halide lamps can be designed to produce almost any color (Specialty colors, including
blue, green, aqua and pink, can also be produced.)
8. Excellent Color Rendering Index.

 Disadvantages of metal halide lamp:

1. High inital cost

2. Control gear is required

3. Lamp takes several minutes for start and restart (2-5 min.)

4. Light pollution: The light is so bright that it produces much more light pollution than HPS.
Loser to daylight in

Types:
There are two types
1. MH lamps Clear lamps
2. MH lamps Phosphor-coated versions
Colour:
1. MH lamps Clear lamps produce slightly bluish-white colour light.
2. Phosphor-coated versions produce a warmer-looking white light (Day light).
Main applications:
Used where colour is important
1. MH lamps are effective replacements for MV lamps.
2. for the tennis board.
3. for the cricket stadium
4. for the ancient building & museums
5. for the water falls
6. Large wattages are used for floodlighting, street lighting, large industrial areas and sports areas.
7. Smaller wattages are used in assembly spaces, schools and public buildings.
8. Clear lamps are used for colour TV broadcasting, colour photography, industrial/commercial
lighting.
9. Phosphor-coated lamps are used for industrial/commercial indoor lighting, area lighting.

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PPP/AITRC/UEE/22626 Department of Electrical Engineering (Polytechnic)

State the function of main components used in fluorescent discharge lamp

1) Ballast:-

The ballast provides the following functions:

a) It provides starting voltage and, in some cases, ignition pulses.

b) The ballast limits the current through the lamp once it has started.

(Fluorescent lamps are a negative resistance device (as more current flows, the resistance
decreases allowing even more current to flow), so the lamps require a ballast to control the
current to the lamp.)

c) The ballast regulates the lamp‟s current when there is line voltage variations, thereby increases
life and performance of lamp.

d) The ballast provides sufficient voltage to sustain the lamp as it ages.

2) Ignitors (Starters):

a) When the lighting system is energized, the ignitor provides the required high voltage pulse
until the lamp arc is established and automatically stops pulsing once the lamp has started.

b) The ignitor provides a pulse of at least 2500 volts peak to initiate the lamp arc

c) It also furnishes the pulse continuously when the lamp has failed or the socket is empty.
An ignitor is an electronic component that must be included in the circuitry of all high
pressure sodium, low wattage metal halide (35W to 150W) and pulse start metal halide (175W to
1000W) lighting systems.
The ignitor should always be mounted near the ballast but not on the ballast.

3) Capacitor:

To improve the power factor a capacitor is connected across the supply.

Two types of capacitors are currently in use:

1) Dry metalized film and

2) Oil-filled.

Present capacitor technology has allowed all but a few capacitor applications to be dry film.
Oil-filled capacitors are used only when dry film technology cannot satisfy capacitor voltage
requirements.

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PPP/AITRC/UEE/22626 Department of Electrical Engineering (Polytechnic)

4) Outer tube:
1) To give mechanical protection to inner tube

2) To avoid heat loss surrounding to inner tube for this vacuum is created between outer and inner
tube.

3) Inside surface of glass coated with phosphors which absorbs the UV and radiates the energy as
visible light outside the lamp.

By combining various types of phosphors in different ratios, manufacturers

can offer "warm white", "cool white" and "daylight" types of lamps

6) Arc tube:-

A gas discharge tube is a tube (usually glass), with two (or more) electrodes inserted into
it, that has been evacuated and filled with a gas or gas (argon, neon, Xenon) mixture usually at
somewhat less than atmospheric pressure.

It is made from (Quartz or ceramic glass) hard glass to with stand at high temperature of arc

Sr.No. Sodium vapor lamp Metal halid lamp

1. The color of light produce is yellowish. warmer-looking white light (Day light)./
slightly bluish-white colour light
2. The arc tube contains xenon / neon gas The inner bulb contains various metal halides,
(starting gas), sodium and mercury along with mercury and inert gases that make
up the mix.
3. Arc tube also contains two electrodes Arc tube also contains two electrodes and
and there is no starting electrode. starting electrode. OR only two electrodes if
igniter is used
4. It require Igniter at starting It does not require Igniter at starting if starting
electrode is used.
5. Color rendering index (CRI) is poor Color rendering index (CRI) is better than
than that of metal halide lamp that of high pressure sodium street lights
6. Luminous efficiency Lm/w 80-100 Luminous efficiency Lm/w 50-100
7. Life more 12000-16000 hrs. Life less than SV lamp 6000-12000 hrs.
8. Suitable for outdoor illumination Suitable for indoor and outdoor illumination
9. Correlated colour temperature (CCT) Correlated colour temperature (CCT) higher.
lower.

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PPP/AITRC/UEE/22626 Department of Electrical Engineering (Polytechnic)

SR.no. Sodium vapor lamp Mercury vapor lamp

1. The color of light produce is yellowish. It gives greenish blue color light
2 The arc tube contains xenon / neon gas The inner bulb contains neon or argon gas with
(starting gas), sodium and mercury certain quantity of mercury.
3 Arc tube also contains two electrodes Arc tube also contains two electrodes and
and there is no starting electrode. starting electrode.
4 It require Igniter at starting It does not require Igniter at starting
5 Color rendering index (CRI) is poor Color rendering index (CRI) is better than
than that of Mercury vapor lamp that of high pressure sodium street lights
6 Luminous efficiency Lm/w 80-100 Luminous efficiency Lm/w 40-60
7 Life more 12000-16000 hrs. Life less than SV lamp 12000 hrs.
8 Cost of installation high Cost of installation moderate
9 Cost of operation moderate Cost of operation low
10 Suitable for outdoor illumation Suitable for indoor and outdoor illumation
11 Correlated colour temperature(CCT) Correlated colour temperature(CCT) higher.
lower.
12 Specially used for street lighting. Not recommended for street lighting.

Comparison of Tungsten filament lamp and fluorescent tube light (FTL)

S.No. Points of comparison Tungsten FTL

1 Quality of light Good Best
2 Capital cost Less More
3 Running cost More Less
4 Lamp efficiency Less ( 12 to 15 lm/w) More ( 20 to 50 lm/w)
5 Colour index Very good Good
6 Life Less More

S.No High Pressure mercury lamp Filament Lamp

1 It is works on high frequency & High The incandescent lamp works on heating effect.
voltage ionisation Whenever temperature surrounding the filament
increases more than 18000C then light will be
emitted.
2 The cost of high pressure mercury vapour It is cost is low
lamp is high.
3 The maintenance for this HPMV is more. The maintenance for this lamp is less.
4 The P.f. of this HPMV is electrical choke is The P.f. of this lamp is unity.
poor
Illumination
PPP/AITRC/UEE/22626 Department of Electrical Engineering (Polytechnic)

5 After the switch on the light will be emitted After the switch on the light will be emitted
after some time delay through the HPMV immediately through the filament.
lamps
6 In the HPMV the choke is acting as ballast Due to supply voltage variation the light

so that light intensity will not changes. intensity may changes it means flicker

7 There is a need of P.F. improvement There is a No need of P.F. improvement

capacitors. capacitors

8 Life of lamp is very high. (minimum 1200- The Life of this lamp is less. (500 to 700

1500 working hrs) ( maximum7500 to working hrs)

10000 hrs)

9 By using the various chemical powders in By this lamp we cannot get multicolour light.

inert gases the various colours can be

achieved in the lamp.

10 The stroboscopic effect is more. The stroboscopic effect is less.

11 There is humming in this tube due to the There is humming is less or no humming in this

electrical choke lamp.

12 The illumination/lumens efficiency is The illumination/lumens efficiency is very less.

more.( 40 to 60 lumen/watt) ( 5 to 18 lumens/watt)

Compare the sodium vapour lamps and CFL lamps

S.No. Points Sodium vapor lamp CFL Lamp

1 Efficiency 80 to 100 lumens/watt 40 to 65 lumens/watt

2 Lumen output More Less

3 Cost High Low

4 Life span 12000-16000 hours 6000-12000 hours

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Illumination