UNIT 5

1. UNIT V
UTILIZATION OF ELECTRICAL POWER
BASIC ELECTRICAL,
ELECTRONICS AND
MEASUREMENTS ENGINEERING

2. INTRODUCTION
 Where there is no natural light, use of artificial light is
made.
 Artificial lighting produced electrically, on account of its
cleanness, ease of control, reliability, steady output, as
well as its low it is playing an increasingly important
part in modern everyday life.
 The science of illumination engineering is, therefore,
becoming of major importance.

3. NATURE OF LIGHT
 Light is a form of radiant energy.
 Various forms of incandescent bodies are the sources
of light and the light emitted by such bodies depend
upon the temperature of bodies.
 The heat of the body, as seen, can be classified as red
hot or white- hot.
 A hot body about 500-800°C becomes a red hot and
about 2,500-3,000°C the body becomes white hot.
 In a red hot higher wavelength and when white hot it
becomes low.
 The wavelength of the light waves varying from 0.0004
to 0.00075 mm, i.e. 4,000-7,500 Å (1 Angstrom unit =
10-10 mm).

4. RELATIVE SENSITIVITY
 The sensitivity of eye to yellow-green radiation is taken
as unity or 100% and the sensitivity to other
wavelengths is expressed as a fraction or percentage of
it.
 The relative sensitivity at a wave length is written k and
is known as relative luminosity factor.
 Visible light can have wave lengths of the light between
4,000A and 7,500A

5. ILLUMINATION
 Strictly speaking light is the cause and illumination is
the result of that light on surfaces on which it falls.
 Thus the illumination makes the surface look more or
less bright with certain colour and it is this brightness
and colour which the eye sees and interrupts as
something useful
 Light may be produced by passing electric current
through filaments as in the incandescent lamps,
through arcs between carbon or metal rods, or through
suitable gases as in neon and other gas tubes.

6. Terms used in Illumination
 1. Plane Angle:
 The angle subtended at a point in a plane by two
converging straight Lines. The largest angle subtended at
a point is ‘2π 'radians
 2. Radian:
 The angle subtended at a point by an arc whose length is
equal to the radius.
 3. Solid angle:
 A Solid angle is subtended at a point in space by an area
and is the angle enclosed in the volume formed by an
infinite number of lines lying on the surface of the volume
and meeting at the point.
 4. Light:
 It is defined as the radiant energy from a hot body which

7.  5. Luminous Flux (F):
 It is defined as total quantity of light energy emitted per
second from a luminous body and is measured in Lumens
 6. Luminous Intensity(I):
 It is the lumino flux per unit solid angle in a given direction
and is measured in (lumen/steradian or candela (cd)).
 7. Lumen:
 Luminous flux emitted by a source of one candle power in
a unit solid angle. Lumen= candle power of source X solid
angle
 8. Candle Power (C P):
 The candle power of a source is defined as the number of
lumens emitted by that source in a unit solid angle in a
given direction.
 9. Illumination (E):
 Illumination of a surface is defined as the luminous flux

8.  10. Brightness or Luminance (L):
 It is defined as luminous intensity per unit projected area of
a given surface in a given direction.
 11. Mean Horizontal Candle Power (M.H.C.P):
 It is defined as the mean of candle power in all directions
in the horizontal plane containing the source of light.
 12. Mean Spherical Candle Power (M.S.C P):
 It is defined as the mean directions and in all planes from
the source of light.
 13. Mean Hemi-Spherical Candle Power (M.H.S.C.P):
 It is defined as the mean of candle power in all directions
above or below horizontal plane passing through the
source of light.
 14. Reduction Factor:
 Reduction factor of a source of light is the ratio of its mean
spherical candle power to its mean horizontal candle

9.  15. Lamp Efficiency:
 It is defined as the ratio of the luminous flux to the power
input. It is expressed in Lumens / Watt.
 16. Space Height Ratio:
 it is the ratio of horizontal distance between lamps and the
height of their mountings.
 17. Utilisation Factor or Co-efficient of utilisation
(UF):
 It is the ratio of total lumens reaching the working plane
and the total lumens given out by the lamp.
 18. Maintenance Factor (MF):
 It is the ratio of illumination under normal working
conditions to the illumination under clear and clean
conditions.
 19. Depreciation Factor (DF):
 It is the ratio of initial illumination to the maintained

10. BASIC RADIOMETRIC AND
PHOTOMETRIC MEASUREMENT
 The Inverse Square Law
 As a surface that is illuminated by a light source moves
away from the light source, the surface appears dimmer.
 In fact, it becomes dimmer much faster than it moves
away from the source.
 The inverse square law, which quantifies this effect,
relates illuminance (Ev) and intensity (Iv) as follows:
 Ev = I v / d
 Where d = the distance from the light source.

11.  Lambert’s Cosine Law
 Lambert’s cosine law states that the illuminance falling
on any surface depends on the cosine of the light’s
angle of incidence, 𝞱.
 “Reflection,” that the angle of incidence is measured
from a line normal to the surface. E q = Ecos 𝞱

12. Lambertian Emission and
Reflection
 A lambertian surface reflects or emits equal (isotropic)
flux in every direction.
 Figure shows a lambertian reflection from a surface.
Notice that the reflection follows the cosine law — the
amount of reflected energy in a particular direction (the
intensity) is proportional to the cosine of the reflected
angle.

13. ARTIFICIAL SOURCES OF
LIGHT
 Illumination by electricity is mainly classified into three
types they are:
 1. By temperature incandescence (incandescent lamps)
 2. By producing an arc between electrodes (arc lamps)
 3. By discharge of electrons (fluorescent lamps and
vapour lamps).

14. Incandescent Lamps
 Electric current is passed through a filament of thin wire
placed in vacuum or an inert gas.
 The current generates sufficient heat to raise the
temperature of the filament to luminosity.
 Their output depends on the temperature of the
filaments so they are termed as “Temperature
Radiators”.
Construction
 It consists of evacuated glass globe structure. The
evacuation is to:
 - To prevent oxidation and
 - Convectional currents of filament.
 - To prevent decrease of temperature by radiation.

15.  Common shapes of incandescent lamps

16.  The coiled- coil filament is the heart of the lamp, where
the light is created. It is supported at two intermediate
points by fine molybdenum wires, slightly springy.
 The electrical current is carried to the filament by a pair
of nickel plated steel lead-in wires
 In one or both of these outer leads there is a fuse wire
section. The lead wires are held in a glass assembly
called the stem, through which a smaller glass tube, the
exhaust tube is also sealed.
 The terminals are insulated from each other by a
special black glass called vitrite

17. Properties of filament made of
ideal material:
 -High melting point.
 -High resistivity.
 -Low temperature coefficient.
 - Low vapour pressure.
 -Ductility
 -Sufficient mechanical strength to withstand
vibrations during use

18.  Clear gas filled incandescent lamps:
 They facilitate light control. It is used where lighting
units are to be distributed accurately.
 They are used in flood lights, projectors, car head lights.
 Inside frosted gas filled lamps:
 They produce soft shadows and practically eliminate glare
from filaments.
 Used in industrial open fittings located in line of sight at
low mounting heights.
 Inside silica coated lamps
 They are less glaring and produce soft shadows.
 The brightness of reflection from shiny surfaces is
minimized.
 Halogen filled incandescent lamps:
 When the bulb is filled with halogen vapour is filled along
with filling gas it restores a part of evaporated filament due

19. Advantages:
 life time is about 2000 hrs
 Very high operating temperature.
 increased luminous efficiency from 22 to
33lumen/watt
 Reduced blacking effect.
 No depreciation of lumens.

20. ARC LAMP
 Working Principle of Arc Lamp
 The working principle of the Arc lamp mainly depends on
the light output as well as stable electrical power.
 The lifetime of the lamp can be reduced by thermal
cycling. This problem can be reduced through specially
used electrode designs. One of the best examples of this
is a carbon arc lamp.
 The electrodes in these lamps are in contact with the air so
that a low voltage can cause to get an arc.
 After that, the electrodes are gradually separated.
 Consequently, the current within this will get heated & the
arc can be maintained among the electrodes.

21.  The high brightness light can be generated through the
carbon vapor within the arc as it is highly luminous.
 Arc Lamp Advantages
 It generates Bright light
 It is used to generate lighting for a large length of streets
 These lights are cheaper than street lights

22.  Arc Lamps Disadvantages
 The electrodes in the lamp need to replace after a short
period of time
 These lamps generate dangerous rays like UV-A, UV-B &
UV-C
 When the light burns, then it generates flickering & buzzing
sound.
 It will damage when he sparks or excessive heat emit
 Applications of Arc Lamp
 Camera flashlights
 Lights at floods & outdoor
 Microscope lighting
 Blueprinting
 Endoscopy
 Projectors in cinema halls

23. Discharge Lamps
 An electric current is passed through a gas or
vapour which renders its luminous.
 The light is produced by the process of gaseous
conduction.
 The commonly used elements are Neon, Mercury,
Sodium vapours.
 Discharge lamps are categorized into two types
 Vapour discharge lamps.
 Fluorescent lamps

24. High-Pressure Mercury Vapour
Lamps
 In a high-pressure mercury vapor lamp, light is produced
by an electric discharge through gaseous mercury.
 Xenon may also be used in high-pressure mercury
vapor lamps to aid starting time, and does not
significantly change the visible spectrum of the lamp.

25. High-Pressure Sodium Lamps
 Light is produced in a HPS lamp by an electric discharge
through combined vapors of mercury and sodium, with
the sodium radiation dominating the spectral emission.
 The hard glass outer bulb may be clear, or its inner
surface may be coated with a diffuse powder to reduce
the brightness of the arc tube.

26. FLUORESCENT TUBES
 High lighting intensities without excessive temperature
rise.
 The efficiency of fluorescent lamp is about 40 lumens
per watt , about three times the efficiency of an
equivalent tungsten filament lamp.
 The fluorescent tube consists of a glass tube 25mm in
diameter and 3.38m-1.52m in length.
 The inside surface of the tube is coated with a thin layer
of fluorescent material in the form of a powder.
 The coating material may consist of zinc silicate,
cadmium ,silicate or calcium tungstate.
 The tube contains small quantity of argon gas at a
pressure of 2.5mm mercury. It is provided with two
electrodes coated with electron emissive material.

27.  A starting is provided in the circuit . Which puts the
electrodes may get heated and emit sufficient electrons.
 A stablishing choke is connected in series with it, which
act as a starting. A capacitor is to improve the power
factor.
 The starting switches are of two types , namely the
thermal type and the glow type .
 Incorporating a Thermal Type Starter as shown

28.  The thermal starter is a current operated device
 Consists of two metallic strips and a heater coil.
 The bimetallic strips are in contact with each other
when the lamp is not in operation.
 When the supply is switched on, the two electrodes
get connected in series through the thermal switch,
the relatively large current rising them to incandescent
 The current also flows through the heater elements as
a result of which bimetallic strikes break contact.
 This causes interruption in the current flow through
the circuit.

29.  Incorporating a Glow Starter as shown

30.  The glow of starter is a voltage operated device and
consists of two bimetallic electrodes enclosed in a glass
bulb filled with a mixture of helium and hydrogen.
 When the supply is switched on, the potential across
bimetallic electrodes causes a small glow discharge at
a small current not enough to heat up the tube
electrodes.
 This discharge is enough, however, to heat the
bimetallic strips of the switch causing them to bend and
make contact.
 The result is a large current through the electrodes,
their temperature being raised to incandescence and
the gas in the immediate neighbourhood is ionized.
 After one or two seconds the bimetallic strips cool down
and the contacts open.

31. Circuit for Instant of Starting of
Fluorescent Tube

32. Fluorescent Lamps for DC
Supply
 The available supply is dc some special accessories
and circuit modification will be required.
 The choke coil has low impedance on dc and
therefore , a ballast resistance is connected in series
with the choke.
 On system below 220V, starting becomes less certain only
thermal type starters should be used.
 The positive end become relatively dark on account of
the tendency of the mercury vapour to migrate towards
the negative end of the tube .In order to overcome this
defect a reversing switch is included in the circuit between
the supply and the fitting.
 No problem of power factor correction. Its disadvantages
are low efficiency due to power loss in ballast series
resistance, increased cost of the ballast resistance and

34. Colour of Fluorescent Light:
 Colour of fluorescent light depends upon the fluorescent
powder used and the vapour pressure in the lamp
 Daylight.- industrial applications
 Warm-White - street lightning
 Warm-White Deluxe - illuminating rooms of large
gathering such as shops, restaurants and dwelling houses.
 White - offices, drawing offices, school and factories
 White-Deluxe- officers, schools and shops
 The normal life of a fluorescent lamp is 7,500 hours .
The average life is for three burning hours per switching
operation. The actual may vary from5,000 to 10,000
hours depending upon the operating conditions. Light
output is reduced by 15-20% after 4,000 hours of
operations

35. Performance Curve:

36. Operating Instructions:
 A fluorescent lamp should start up with little blinking.
Blinking indicates a defective starter. Both the choke
and the starter will get damaged due to overheating , if
this conditions is allowed to persist .The tube or the
starter must be replaced immediately.
 Correct voltage must be ensured
 The starter should be replaced every time a tube is
changed. A bad starter shortens the life of the tube.
 Frequency switching operations should be avoided.
 Merits
 High luminous efficiency, long life, low running cost, low
glare level and less heat output.
 Demerits
 small wattage requiring large number of fittings and

37. COMPACT FLUORESCENT LAMPS
(CFLs)
 CFLs can replace incandescent that are roughly 3-4
times their wattage, saving up to 75% of the initial light
energy.
 Although CFLs costs 3-10 times more than comparable
incandescent lamps, they last about 10 times as long
(10,000 hours).
 CFLs are most cost effective in areas where lights are
ON for long periods of time.
 CFLs as a means of reducing electric demand,
encouraging the adoption of CFLs in place of
incandescent lamps.
 Like all fluorescent lamps, CFLs contain mercury, which
makes their disposal complicated.

38. Operation
 They consist of two components: a gas-filled tube, and
a magnetic or electronic ballast.
 The gas in the tube glows with ultraviolet light when
switched ON and electric current from the ballast flows
through it.
 This in turn excites a white phosphor coating on the
inside of the tube, which emits visible light throughout
the tube surface.
 CFLs with magnetic ballasts flicker slightly at start.
 The tubes will last about 10,000 hours and the ballast
about 50,000 hours.
 Electronic ballasts contain a small circuit board with
rectifiers, a filter capacitor and usually two switching

39.  CFLs are designed to operate within a specified
temperature range. Temperatures below the range
cause reduced output.
 Types of CFLs
 CFLs are available in a variety of styles or shapes.
 Some have two, four, or six tubes while others have
circular or spiral-shaped tubes.
 Some CFLs have the tubes and ballast permanently
connected. Other CFLs have separate tube and ballasts
which facilitates in replacement of tube without
changing the ballast.
 CFLs are of two types:
 integrated - combine a tube, an electronic ballast
 non-integrated lamps- permanently installed in the
luminaire, and only lamp is usually replaced at the end of
life.

40. Tubular Type Compact Fluorescent Lamp
Helical Integrated CFL

41. REFRIGERANTS
 The suitability of a refrigerant for a certain application is
determined by its physical, thermodynamic, chemical
properties and by various practical factors.
 There is no one refrigerant which can be used for all
types of applications
 Desirable properties
 Low boiling point.
 High critical temperature.
 High latent heat of vaporization.
 Low specific volume of vapour.
 Low specific heat of liquid.
 Easy to liquefy at moderate pressure and temperature.
 It should be noncorrosive, noninflammable and non-toxic

42.  Various types of refrigerants used for domestic
purposes and various industrial utilities.
 Classified as primary refrigerants and secondary
refrigerants.
 Primary refrigerants are those working mediums or
heat carriers which actually traverse the whole cycle of
evaporation, compression, condensation and
liquidification
 Secondary refrigerants are those circulating cold
substances which only transfer heat from a remote point
to the evaporator of the refrigeration system

43. DOMESTIC REFRIGERATOR
 The main purpose of this type of refrigeration is to
provide low temperature for storage and distribution of
foods and drinks
 Electrical Circuit of a Refrigerator

44.  Refrigerator is provided with a door push switch, which
closes on opening of refrigerator and puts the lamp on.
 Capacitor-start single phase induction motor is used in
open type refrigerators and split-phase single phase
induction motor is used in sealed unit refrigerators.
 Electromagnetic relay is provided to connect auxiliary
winding on the start and disconnect it when the motor is
pick up the speed.
 Thermal overload release is provided to protect the
motor from the damage against flow of overcurrent
 Thermostat switch is provided to control the
temperature inside the refrigerator. Temperature inside
the refrigerator can be adjusted by means of
temperature control screw.

45.  To protect the motor against undervoltage use of
automatic voltage regulator is essential since
incase of fall in applied voltage, motor will draw
heavy current to develop the required torque and
will become hot, thermal overload relay will,
therefore, repeatedly disconnect and connect the
motor to supply, eventually burning it out.

46. Domestic refrigerator employing vapour compression
refrigeration system is shown in Figure

47. AIR CONDITIONING
 The important factors involved in a proper, efficient and
complete air conditioning systems are:
 Temperature Control
 Humidity Control
 Air-movement and Circulation
 Air-filtration, Cleaning and Purification

48. Room Air Conditioners
 It is a common type of air conditioner used to condition
the air of a particulars space occupied by human
beings
 It has automatic operation to cool and humidity the air.
 A window type air conditioner is shown in Figure

49.  It consists of a case divided into two parts by a partition
with a small opening at the top as the outdoor part and
indoor part.
 The outdoor portion consists of a hermetically sealed
motor compressor unit, condenser, motor driven fan and
a tray.
 This portion partitioned by a portion L into two parts is
provided with a left hand side opening.
 The indoor portion consists of evaporator, motor driven
fan, remote bulb, refrigerant, control, a control panel, an
air filter, power connector and a tray.
 This portion is further subdivided into two parts by
opening on the right hand side.
 A pipeline connects the two trays in the inner and outer
parts. A capillary line control through a refrigerant filter

50.  Evaporator is connected to the compressor by a suction
pipeline.
 The front and back of the inner and outer portions of the
cooler is fitted with shutters.
 These shutters are adjustable at different inclinations
according to the requirements.
 As the unit is put into operation, the low pressure
vapour through the suction pipeline is drawn from the
evaporator and passed to the compressor.
 The compressor delivers it at high pressure to the
condenser. In the condenser, the vapour gets
condensed and the heat is removed from the refrigerant
vapour.
 The liquid refrigerant collected at its lower coils is
passed through the filter into the capillary tube control

51. Main advantages of room air
conditioners are
 Saving in installation and field assembly labour.
 Exact requirement of each separate room is met
whereas a central system cannot meet the individual
needs of separate rooms.
 Zoning and duct work is eliminated.
 Low initial cost.
 Flexibility of operation.
 Failure of unit affects a single room where as all the
rooms are affected when failure occurs in the central
system.

52. Central Air Conditioning
Systems
 The central air conditioning systems serving the needs
of large building or space are generally called the year-
round air conditioning systems.
 They have a cooling capacity of 25 tones and circulate
about 300 m3 /minute of conditioned air.
 Depending upon its type such a system may contain
some of the following equipments:
 Heating coils supplied with steam or hot water.
 Cooling and dehumidifying coils
 Blower and driving motor
 Sprays for cooling and dehumidifying
 Air-cleaning equipment containing filters, electrostatic
precipitators, odour removing equipment and germicidal
lamps

53.  The various factors affecting the choice of the
equipment for design and installation of the central
air-conditioning systems are capacity of the plant, filters
and mixing plenums, refrigeration and heating
equipment, insulation, noise and vibration.
 1. Capacity of the plant.
 2. Filters and mixing plenums
 3. Refrigeration and Heating Equipment
 4. Insulation
 5. Noise and Vibration