3340903-UEE- UNIT-1.pptx

Prepared By:
MR. K.K.PATEL
(LECT. IN EE DEPT.)
(VPMP POLY TECHNIC, SECTOR-15
GANDHINAGAR)
1
As Per revised syllabus of GTU 4th Sem
3340903- Utilization of Electrical
Energy

2
UNIT -1
ILLUMINATION
SUBJECT CONTENT
1a. Define various illumination terminology
and its units
1b. Explain the laws of illumination and its
significance
1c. Describe the working and applications of
the various lamps and fittings in use.

 Introduction:
 As we know that almost all human activities
depends on light. Sun is a prime natural source
of light but artificial lighting plays almost main
role in our daily life. These artificial lights are
produced by mechanical lamps and electrical
lamps.
 But due to poor performance the mechanical
light are totally replaced by electrical lights. The
electrical lighting are mainly used for decorative
purpose, advertising, traffic control , medical
field and street lighting etc.

 Electrical Lighting
Electrical lighting has following advantages :
1. Cleanliness
2. Easy to control
3. Economical
4. Easy to handle
5. Steady output
6. Better reliability
7. Suitable for almost all purposes etc.

 Concept Of ILLUMINATION
 The electric lamps are preferred to other sources
of illumination for reasons of cleanliness,
convenience, steady light output and reliability.
When the light falls on a surface it is illuminated.
The illuminanation is defined as the luminous flux
received per unit area.
Illuminanation = lumens / area
 If the area is in meters the unit is lumens per
square meter.

 TERMS USED IN
ILLUMINATION
LIGHT:-
Light is also known as the radiant energy from a hot
body causing a visual sensation upon the human eye.
LUMINOUS FLUX:-
It is defined as the energy in the form of light waves
radiated per second from a luminous body in form of light
waves. It is measured in lumens. It is denoted by .
LUMINOUS EFFICIENCY OR RADIANT EFFICIENCY:-
It is define as the output lumens per watt of the power
consumed by the source of light . it is measured in lumen
per voltage.

Plane Angle
The angle subtended at a point by two converging lines lying in the same
plane is called plane angle. It is measured in radians and equal to the ratio
of the length of the arc too its radius,
θ = arc/ radius = l/ r radians 11/03/2013

Solid Angle
The angle subtended by the partial surface area of a sphere at its centre is
called as solid angle. It is measured in steradians and equal to the ratio of
area of the surface to the square of radius of sphere,
ω = area of surface/ square of radius = A/ r2 steradians 11/03/2013

LUMINOUS INTENSITY :-
Luminous intensity is defined as flux emitted by the source per unit
solid angle. if luminous intensity is represented by I.
I=dF / dw
LUMEN:-
It is the unit of flux and is defined as the luminous flux per unit angle
from a source of 1 candle power.
Lumen = candle power x solid angle
= C.P. x w
CANDLE POWER:-
Candle power is define as the number of lumens per unit solid angle.
C.P = lumens /w

ILLUMINATION:-
When the light falls on a surface it is illuminated. The illumination is
defined as the luminous flux received per unit area.
Illumination = dF/dA
= lumens/area
= C.P x w/Area
SPACE HEIGHT RATIO:-
It is defined as the ratio of horizontal distance between lamps and the
mounting height of the lamps. Or
Space Height Ratio =
The horizontal distance between lamps
Mounting height of lamps
In order to have a uniform illumination which can be only with
reflection, it is necessary that the value of this should be properly
chosen; when reflectors are used the value of this ratio is given as
between 1 & 2.

UTILIZATION FACTOR:-
The total light flux radiated out by the source is not utilized
on the working planes and utilization factor is given as
Utilization factor =
Total lumens utilized on working
planes
Total lumens radiated by lamp
The value of this co-efficient depends upon the
following conditions:-
 The area to be illuminated.
 Height at which the lamps are fitted.
 The colour of surrounding walls, ceiling, fitting etc.
 The type of lighting-direct or indirect

DEPRECIATION FACTOR:-
When the lamps are covered with dust, dirt and smoke,
they do not radiate out some amount of flux as when they
do at the time of fitting.
Similarly after some time the walls and surrounding at
which lamps are fitted are covered with dirt and dust, so
they do not reflect the same amount of light as compared
with the initial condition. The depreciation factor takes into
account all such losses of flux.
The depreciation factor =
Illumination under normal working condition
Illumination when every thing is clean

 MEAN HEMISPHERICAL CANDLE POWER (M.H.C.P) :-
It is the mean of the candlepower in all directions within
the hemisphere either above the horizontal plane or below
the horizontal plane.
 FOOT CANDLE:-
It is the unit of illumination and may be defined as the
illumination of the inside of spheres of radius 1 ft. at the
center of which there is a source of 1 C.P.
 LUX:-
It is a meter candle and is defined as the illumination of
the inside of the sphere of radius 1 meter at the center of
which there is a source of 1 C.P.

 NIT:-
It is an M.K.S. Unit of luminance or of degree of
illumination at the surface and is defined as
illumination of one candle per square meter.
 STILB:-
It is bigger M.K.S. Unit of luminance and equal to
illumination of one candle per square centimeter.
 GLARE:
It is defined as the brightens within the field of
vision of such a character as to cause any kind of
discomfort with vision.

 WASTE LIGHT FACTOR:-
A surface when illuminated by number of lamps,
there is certain amount of wastage due to over-
lapping of light waves. Its values for rectangular and
irregular areas are 1.2 and 1.5 respectively.
 SPACE HEIGHT RATIO: -
It is defined as the ratio of horizontal distance between
lamps and the mounting height of the lamps or space
height ratio,
=The horizontal distance between lamps / Mounting
height of lamps
When reflectors are used the value of this ratio is given
between 1 & 2.

 Absorption Factor:
It is the ratio of lumens available on the working
surface after absorption to the lumens output by the
lamps.
The value of this factor lies between 0.5 to 1.
 Refection Factor:
It is ratio between reflected light and incident light.
 Lamp factor:
It the ration of output luminous flux given by any lamp
to the electrical energy required to produce it.

 Two Components of
Illumination
 Light Sources
 Emission Spectrum (color)
 Geometry (position and direction)
 Directional Attenuation
 Surface Properties (Reflectors)
 Reflectance Spectrum (color)
 Geometry (position, orientation, and micro-
structure)
 Absorption
 Transmission

 Measurement of ILLUMINATION:
 For measurement of illumination various equipments
are used. Among them lux meter is the easier and
simplest portable equipment. It given direct reading of
illumination.

 LAWS OF ILLUMINATION:-
To find illumination at any surface, Two laws of
illumination:
 Inverse square law
 Lambert ‘s cosine law

 INVERSE SQUARE LAW:-
 Consider a point source of lights as shown in fig. let
within a solid angle w three parallel sources of areas
A1,A2 and A3 be placed at a distance d,2d and 3d
from the point source one by one as shown. Let I be
the intensity of illumination of the source in that
direction.

 This law is applicable only for Point Sources.
 From above figure,
Let,
S is the Point Source of Light,
A1 , A2 , A3 are Three Parallel Surfaces.,
d1, d2 , and d3 is distances of A1, A2 and A3
from Point source.
Assume that I is Illumination Intensity.
w is solid angle made by the surfaces.
Total flux of light on areas A1,A2and A3 is equal and
is given by,

 A1=Iw lumens
 Illumination on surface A1 is
E1 = Iw / A1
 Area of surface A1 = wd2
 illumination on surface A1 = --------(1)
E2 = Iw / A2
 Area of surface A2 = w(2d)2= 4wd2
 illumination on surface A2 = -----(2)
2
2
1
d
I
wd
Iw
E 

 
2
2
2
2
2
4
4 d
I
d
I
wd
Iw
E 



E3 = Iw / A3
 Area of surface A3 = w(3d)2= 9wd2
 illumination on surface A3 =
--------(3)
 From, above equations no 1,2, and 3 ,
E1 : E2 : E3 ::
 Hence the illumination of a surface is inversely
proportional to the square of the distance of the
surface of light . This is true only if the source is a
point source.
 
2
2
2
3
3
9
9 d
I
d
I
wd
Iw
E 


   2
2
2
3
1
2
1
1
d
d
d



 LAMBERT’S CONSINE LAW:
 “Illumination of a surface at any point is
dependent upon the cube of cosine of the
angle between the line of flux and the normal
at that point”.
 While surface was normal to the light flux, but
in practice this is not always possible .
Illumination for such cases is given by
lambert’s cosine law

 Let F be the total light flux falling on the area.
Thus in fig ( A) ,the angle between normal to the
surface
and line of flux is zero.
Intensity of Illumination,
E = F/(Area ABC) lumens/sq. m
Thus in figure ( B) The angle between the line of flux
and normal is 
Intensity of illumination
E= F/(Area abc) x cos
lumens/sq.m.

 Thus it will be observed that the illumination is
proportional to the cosine of angle between the
normal and the line of flux.
 Consider two small discs AB and CD as shown in
fig. Disc AB is normal to the light flux which is
inclined at angle  to the vertical.

 Illumination on surface AB
Flux in lumens/Area AB……….……..(1)
 Illumination on surface CD
= Flux in lumens / Area CD……..……...(2)
= Flux in lumens x cos/(Area AB)……(3)
Thus Illumination on surface CD
= Illumination on surface AB x cos……(4)

 Illumination of surface CD
= CP cos/R2 ………..……..(5)
 But cos = H/R ………………(6)
So,
 Illumination of surface CD =CP cos2/H2
 This law is also known as cos3 law.

Sources of Light
 Natural Source of Light
The light that is found in nature is known as natural light
Sun
Moon
Stars
Glow Bug
Anything that gives out light is called a light source.
We see objects when they reflect light rays into our eyes.

Artificial Sources of light
The source of light that is man made is known as artificial light.
Candle
Tube Light
Bulb

Luminous and Non-Luminous Objects
Luminous Objects : That gives their own light are called Luminous Objects
Sun
Bulb
Stars

Electrical method of producing Light
Following are the methods of producing light :
1. By developing arc between two electrodes
2. By passing a current through a filament
3. By electric discharge through vapors or gases
11/03/2013

Types of Lamps:
 The first ever practical model of the incandescent
lamp was invented in 1879. Since then, there has
been series of developments in the area of light
source and lighting technology. The first
incandescent lamp was made with a carbon
filament with a useful light output of only three
lumens per watt. A long time has gone by since
then and today there are about 200 thousand
different types of demands keeping in view the
wattage, size, applications, etc. It includes about
40,000 types of incandescent lamps alone.

 On 21-22 October 1879, Edison and
his staff conducted their first
successful experiments with a
carbon-filament lamp in a vacuum.
The filament was made from a piece
of carbonized thread. By New Year's
he was demonstrating lamps using
carbonized cardboard filaments to
large crowds at the Menlo Park
laboratory. A year later, Edison
began manufacturing commercial
lamps using carbonized Japanese
bamboo as filaments.

There Are Following Different Types
Of Electrical Lamps:
1. Incandescent lamp (GLS)
2. Fluorescent lamps (FTL)
3. High Pressure Mercury Vapour lamps (HPMVL)
4. Halogen lamps
5. High Pressure Sodium Vapour Lamps (HPSVL)
6. Low Pressure Sodium Vapour lamps (LPSVL)
7. Metal Halide lamps
8. Mercury Blended lamps
9. Compact Fluorescent lamps

INCANDESCENT LAMPS:-
 Incandescent lamp has a history of over a
century. The design of the lamp has changed
many times, but still it remains to be the most
popular type due to its simple construction, easy
replacement and cheap cost. Incandescent lamps
are available in wattage rating up to 1500W.

CONSTRUCTION:-
 Fig. illustrates the construction of a general
lighting service (GLS) lamp. Incandescent
lamps work on the principle that visible light
and infrared radiation are emitted as a result of
heating of the filament wire by a current
passing through it. These emissions become
noticeable above 500°C. Tungsten is usually
used as the filament material since it has high
melting point. The diameter of the filament wire
is determined by the operating current and the
length of the filament by the operating voltage.
For normal voltages, the length will be too
much and a coiled coil arrangement is adopted
to accommodate the long filament wire. The
filament is mounted on leads that carry the

Neon Lamp
Applications :
Neon lamps are generally used for advertising.
Most of letters having two ends at which
electrodes are placed. In letter having more than
two ends , the tube path is repeated for some
portion.
11/03/2013

Halogen Lamp
Halogen lamp is a special type of tungsten filament
lamp which was developed in 1959, in this lams, a
small amount of halogen vapor is added to the inert
gas of the bulb. Its glass bulb is small in size and
mechanically strong. It operates at high temperature
of 3000 oC .
11/03/2013

Halogen Lamp
When the supply is given to the lamp, a filament glows
and produce light. The halogen in addition to inert
gas causes the evaporated tungsten to resettle back
on the filament during cooling, that’s why lamp can
be operated at high temperature. It provides high
intensity light.
11/03/2013

Advantages of Halogen Lamp
1. It is smaller in size.
2. It does not need any blast.
3. Good colors can be obtained.
4. Excellent optical control.
5. Gives same output throughout life
6. It has long life
11/03/2013

Disadvantages of Halogen Lamp
1. During maintenance the handling of lamp is
difficult.
2. Radiant heat is more which heats the
surroundings.
3. Operating temperature is high which effects its
life.
11/03/2013

Fluorescent Tube
it is a low pressure mercury vapor lamp. It consists
of a glass tube 25 mm in diameter and 0.6 m, 1.2
m and 1.5 m in length. The tube contains argon
gas at low pressure about 2.5 mm of mercury. At
the two ends, two electrodes coated with some
electron emissive material are placed.
11/03/2013

Fluorescent Tube
The colors produce by this tubes are as :
Material Color
Zinc silicate Green
Calcium tungsten Blue
Cadmium borate Pink
Calcium Holo phosphate White or day light
Magnesium tungsten Bluish white
11/03/2013

Fluorescent Tube
Working :
A choke is connected in series with the tube which
act as a blast and provide a high voltage at starting
glow in the tube. During running condition the same
choke absorbs some supply voltage and remain a
voltage of 110 V across the tube. A capacitor is
connected to improve the power factor.
11/03/2013

Advantages of Fluorescent Tube
1. Voltage fluctuation has very small effect on light
output.
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.
11/03/2013

Disadvantages of Fluorescent
Tube
1. Its brightness is less.
2. Initial cost is more
3. Overall maintenance cost is high.
11/03/2013

Tungsten Halogen Lamps:-
 In incandescent lamps, the filament material
(tungsten) evaporates and gets deposited on the
inner surface of the bulb. This affects the
performance of the incandescent lamp. First it
erodes the filament material resulting in reduction of
current and hence the light produced. It also reduces
the life of the lamp. Also, tungsten deposited on the
glass bulb reduces its transparency resulting in lower
light output. These problems are solved to a great
extent in tungsten halogen lamps in which some
halogen is also introduced into the bulb along with
the filling gas. When a halogen is added to the filling
gas, the tungsten vapour and halogen molecules
combine to form tungsten-halogen molecules.

 The tungsten halogen
lamps have longer life
compared to incandescent
lamps. For the same
wattage, light output is also
higher compared to an
incandescent lamp. These
lamps are commonly used
as projector lamps,
photographic lamps,
automobile lamps etc. and
are also used for flood
lighting.

Fluorescent Lamps:-
 Fluorescent lamp is the most widely used
discharge lamp. It is an energy efficient lamp
available in low and medium wattage range
making it suitable for domestic and
commercial lighting purposes.

Construction:-
 The construction of a standard fluorescent lamp is
shown in Fig. c. It consists of a glass tube of around
36 mm diameter and a length of 1200 mm. The inner
surface of the tube is coated with a fluorescent
powder - usually phosphor coating. Tungsten wire
electrodes with bi-pin cap are provided at both ends.
There is an electrode shield around each electrode to
reduce the blackening of the tubes due to deposition
of evaporated tungsten. The tube is filled with an inert
gas such as argon to a pressure of 1.5 to 5 mm of
mercury. A small drop-let of mercury is also
introduced into the tube. During normal operation this
mercury vaporizes and helps to maintain the
discharge.

Compact Fluorescent Lamps:-
 Compact Fluorescent Lamps (CFLs) are now
becoming very popular. It is a smaller type fluorescent
lamp that is even more energy efficient. CFLs are
available in wattage ratings of 5W, 7W, 9W, 11W,
13W, 18W, 23W etc. and usually they come with an
adapter having a cap similar to the incandescent lamp
cap so that the lamp can directly be fixed into an
ordinary lamp holder.
 The adapter contains necessary circuits for startup
and normal operation of the lamp. The principle of
operation is very similar to ordinary fluorescent lamps,
but uses a thin tube. The tube may be U shaped or
having multiple folds. The light output of an 11W CFL
is equivalent to that of a 60W incandescent lamp. This

Mercury Vapour Lamps:-
 Mercury vapour lamp is a discharge lamp,
available in a wattage range of 50 to 1OOO W. It
is commonly used for street lighting, yard lighting
etc.

Construction and operation:-
 The lamp has an arc tube inside and an outer
envelope as shown in Fig. d The inner side of the
envelope has a phosphor coating. The actual
discharge takes place inside he arc tube. Fig. d
Mercury vapours lamp construction.
 The arc tube is made of quartz and is capable of
withstanding high temperature and pressure. Inside
the discharge tube there are two main electrodes
placed at both ends and an auxiliary electrode near
to one of the main electrodes. The tube contains a
mixture of mercury vapour and an inert gas - usually
argon. Initially, when the voltage is applied there will
be no discharge between the main electrodes, but the
same voltage is available between the auxiliary
electrode and the main electrode next to it.

Metal Halide Lamps:-
 Metal halide lamp is a modified form of mercury vapour lamp. In
this lamp, metals other than mercury are also added to the
discharge tube. Due to the spectral contribution of these metals,
light emission occurs over a wide range of visible spectrum and
hence the colour rendering index and efficacy are considerably
increased. Commonly used metals are sodium, scandium,
gallium thallium, indium etc. The selection of metals and the
composition are dependant on the type of emission required.

Sodium Vapour Lamps:-
 Sodium vapour lamp is also a discharge lamp. The discharge
tube of this lamp contains a mixture of sodium vapour and an
inert gas — usually neon. At normal temperature, the sodium
inside the tube shall be in solid state and therefore do not
contribute to discharge. The inert gas is added as a 'starting gas'
and the initial discharge shall be due to the presence of this gas.
 The radiation produced by sodium lamp is predominantly a
monochromatic yellow colored radiation at 589 nm wavelength.
This wavelength has a specialty that it is very near to the peak
of the eye sensitivity curve.

LED lamp:-
 Solid state LEDs have been popular as indicator lights since the
1970s. In recent years, efficacy and output have risen to the
point where LEDs are now being used in niche lighting
applications.
 Indicator LEDs are known for their extremely long life, up to
100,000 hours, but lighting LEDs are operated much less
conservatively (due to high LED cost per watt), and
consequently have much shorter lives.
 Due to the relatively high cost per watt, LED lighting is most
useful at very low powers, typically for lamp assemblies of under
10 W. LEDs are currently most useful and cost-effective in low
power applications, such as nightlights and flashlights. Colored
LEDs can also be used for accent lighting, such as for glass
objects, and even in fake ice cubes for drinks at parties. They
are also being increasingly used as holiday lighting.

Different types of lights have vastly
efficiencies and color of light:-

Electrical ballast:
 An electrical ballast is a device intended to limit
the amount of current in an electric circuit. A
familiar and widely used example is the inductive
ballast used in fluorescent lamps, to limit the
current through the tube, which would otherwise
rise to destructive levels due to the
tube's negative resistance characteristic.
 Ballasts vary in design complexity. They can be
as simple as a
series resistor or inductor, capacitors, or a
combination thereof or as complex as electronic
ballasts used with fluorescent lamps and high-
intensity discharge lamps.

Electromagnetic Ballasts
• The current lighting device is a reactor.
Supply voltage sufficient to start the lamp
• The starting voltage device is an auto transformer.
Supply voltage insufficient to start the lamp
• Operate the lamps at 50/60 Hertz

 Electronic Ballasts
Both starting and current limiting functions are
provided by electronic components.
Operate the lamp at 20kHz or greater.

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