Electrical and Electronics lab manual

DEPARTMENT OF ELECTRICAL ENGINEERING
LAB-MANUAL
I SEM ALL BRANCHES
108 ELECTRICAL &
ELECTRONICS
LAB
CONTENTS
USB/Department of Electrical Engineering/EEE LAB 108 Page 1

Sr. No. Title Page No.
1 RTU Syllabus
2 Experiment List
3 Lab Ethics
4 Instructions
5 Experiment-1
6 Experiment-2
7 Experiment-3
8 Experiment-4
9 Experiment-5

RTU Syllabus
Electrical lab
1. Assemble house wiring including earthing for 1-phase energy meter, MCB, ceiling fan, tube
light, three pin socket and a lamp operated from two different positions. Basic functional study
of components used in house wiring.
2. Prepare the connection of ceiling fan along with the regulator and vary the speed.
3. Prepare the connection of single phase induction motor through 1-Phase Auto-transformer and
vary the speed.
4. Prepare the connection of three phase squirrel cage induction motor through 3-Phase
Autotransformer and vary the speed.
5. Prepare the connection of Fluorescent Lamp, Sodium Vapour and Halogen Lamp and measure
voltage, current and power in the circuit.
Electronics lab
1. Identification, testing and application of Resistors, Inductors, Capacitors, PN-Diode. Zener,
Diode, LED, LCD, BJT, Photo Diode, Photo Transistor, Analog/Digital Multi- Meters and
Function/Signal Generator.
2. Measure the frequency, voltage, current with the help of CRO.
3. Assemble the single phase half wave and full wave bridge rectifier & the analyze effect of L,
C and L-C filters in rectifiers.
4. Study the BJT amplifier in common emitter configuration. Measure voltage gain plot gain
frequency response and calculate its bandwidth.
5. Verify the truth table of AND, OR, NOT, NOR and NAND gates.
ELECTRICAL LAB MANUAL

List of Experiment
Rotor# 1
1. a) To basic functional study of components used in house wiring and to make house wiring
connections which includes 1-phase energy meter, MCB, ceiling fan, tube light, three pin socket
etc.
b) To make a connection for stair case wiring which can operate a lamp from two different
positions?
2. To study the construction and working of ceiling fan and connections of ceiling fan with
regulator.
3. Prepare the connection of single phase induction motor through 1-Phase Autotransformer and
vary the speed.
4. Prepare the connection of three phase squirrel cage induction motor through 3-Phase
Autotransformer and vary the speed.
5. a) To study the construction, circuit, working and application of the Fluorescent lamp.
b) To study the construction, circuit, working and application of the Sodium vapour lamp and
Halogen lamp.
.
LAB ETHICS

DO’s
1. Enter the lab on time and leave at proper time.
2. Keep the bags outside in the racks.
3. Utilize lab hours in the corresponding experiment.
4. Make the Supply off the Kits/Equipments after completion of Experiments.
5. Maintain the decorum of the lab.
Don’ts
1. Don’t bring any external material in the lab.
2. Don’t make noise in the lab.
3. Don’t bring the mobile in the lab.
4. Don’t enter in Faculty room without permission.
5. Don’t litter in the lab.
6. Don’t carry any lab equipments outside the lab.
We need your full support and cooperation for smooth functioning of the lab.

INSTRUCTIONS
BEFORE ENTERING IN THE LAB
1. All the students are supposed to prepare the theory regarding the present
Experiment.
2. Students are supposed to bring the practical file and the lab copy.
3. Previous experiment should be written in the practical file.
4. Object, Apparatus Table & Brief Theory of the current practical should be written in
the lab copy.
5. Any student not following these instructions will be denied entry in the lab and
Sessional Marks will be affected.
WHILE WORKING IN THE LAB
1. Adhere to experimental schedule as instructed by the faculty.
2. Record the observations in lab copy & checked by the faculty.
3. Each student should work on his assigned table of the lab.
4. Take responsibility of valuable accessories.
5. Concentrate on the assigned practical and be careful.
6. If anyone is caught red-handed carrying any equipment of the lab, then he will have
to face serious consequences.

EXPERIMENT # 1(A)
OBJECT:
To make house wiring including Earthing for 1 Phase Energy Meter, M.C.B, and a Lamp
operated from two different positions.
APPARATUS REQUIRED:
S.NO. ITEMS RATING QUANTITY
1. Two way switch 6 ampere – 250 volt 2
2. Switch 6 ampere – 250 volt 4
3. Indicator ------------------------- 1
4. M.C.B. 6 ampere ,250 volt, DPST Type 1
5. Holder -------------------------- 2
6. Bulb 100 watt , 250 volt 2
7. Tester 100 watt , 250 volt 1
8. 3 Pin Socket 6 ampere , 250 volt 1
9. Tube light 40 watt , 250 volt 1
10. Fan with Reg. 12 Pole, Sweep 1200mm 220-230 volt 1
11. Energy Meter 1 Phase , 250 volt 1
12. Wire Stripper 100 mm 1
THEORY:
A network of wires connecting various accessories for distribution of electrical energy from the
supplier’s meter board to the numerous electrical energy consuming devices such as lamps, fans
and other domestic appliances through controlling and safety devices is known as wiring system.
The supplier’s service cable feeding an installation terminates in what is usually called the service
fuses. In an ordinary house the service fuse is called as service cutout. Such cutouts including
service meters remain the property of the supplier and represent the furthest point of the supplier
responsibility. The point at which the consumer's wiring is connected into cutout is known as point
of commencement of supply or consumer's terminals. From consumer terminals onwards the
supply cables are entirely under the control of consumer's and so laid out as per his selection. A
typical house wiring circuit is shown in fig. 2.1

Fig 2.1 Connection diagram of House wiring
Fig 2.2 Distribution Board System
In distribution board system, which is most commonly adopted for distribution of electrical energy
in a building, the fuses of various circuits are grouped together on a distribution board, sometimes
simply known as fuse board. The two copper strips, known as bus-bars, fixed in a distribution
board of hard wood or metal case are connected to the supply main through a linked switch so that
the installation can be switched off as a whole from both the poles of supply if required. A fuse is
inserted in the +ve or phase pole of each circuit so that each circuit is connected up through its
own particular fuse.
In large buildings, however, if only one distribution board were used, some of the points would be
at a considerable distance from it and in such cases it is advisable to employ sub-distribution
boards either to save cable or to prevent too great voltage drop at the more distant points (lamps or

fans or other appliances). In such cases main distribution board controls the circuit to each sub-
distribution board from which the sub-circuits are taken, as shown in fig. (a)
The number of circuits and sub-circuits are decided as per number of points to be wired and load to
be connected to the supply system. For determination of load of an installation the following
ratings maybe assumed unless the values are known or specified.
a) Fluorescent lamps — 40 watts.
b) Incandescent lamps, fans, and socket outlets — 60 watts.
c) Power socket-outlets — 1,000 watts.
d) Exhaust fans — as per capacity of exhaust fans.
There are number of methods of installing a wire system.
 Cleat wiring
 Casing Wiring
 T.R.S. Wiring
 Metal Sheathed Wiring
 Conduit Wiring
 PVC Conduit Wiring
Generally, for wiring in the house 20 SWG wire is used and for Earthing 14 SWG is used.
HOUSE WIRE LAYOUT- Two wire from RSEB Pole bring 230 volt A.C. to our house. Our
house is Phase (P) and other is neutral.
ENERGY METER- It may be disk type, Conduction Meter or Electronic Meter.
SOCKET- Socket has three types of terminals-
 Neutral,
 Phase ,
 Earthing
Earthing is of big size and other two are same.
M.C.B. (Miniature Circuit Breaker) normally, in House wiring, 2 Pole M.C.B. is used. As we
know the fuse and M.C.B. are in fact is used to isolate a system from supply in case of:-
 Over load
 Short circuit
EARTHING:-
We know that Earthing is provided for the safety of both, Human Beings and Equipments. It is of
two types-
 Plate earthing
 Pipe earthing

FACTOR AFFECTING EARTH RESISTANCE:-
The earth electrode resistance depend on electrical resistivity of soil which in turn depends upon-
 Nature of soil
 Extent of moisture
 Presence of suitable salt in moisture
EARTH ELECTRODE
It is of two types-
 rod and pipe electrode
 plate electrode
CIRCUIT DIAGRAM:
Fig 2.3 Circuit Diagram of House Wiring with Earthing
OBSERVATION TABLE:
S.No. Devices Switches
1 Bulb B1
2 Fan B2
3 Tube Light B3
4 5 Amp,3 pin socket B4
RESULT:

We make connection and get result as shown in Observation Table.
PRECAUTIONS:
1. Connections should be right and tight.
2. Do not touch any wire.
3. Do not keep any joint open.
4. Use M.C.B. and switches of proper current rating.
EXPERIMENT # 1(B)
OBJECT:

To wiring for a lamp to be controlled from two positions (stair-case wiring).
APPARATUS REQUIRED:
Sr. No.
Apparatus Required Rating
Type Quantity
1. Lamp Holder 6Amps, 250 volts 1
2. Lamp 100 Watts,15 Watts 1
3. Switches( Two-way) 5 Amps, 250 Volts 2
4. Connecting Leads
-
- As Reqd.
5. Screw Driver - - As Reqd.
THEORY:
STAIR-CASE wiring is a special type of wiring ,which is different from ordinary wiring due
to field of application.
In staircase wiring ,bulb used for lightening the staircase can be switched ON and OFF from
both sides, upstairs and downstairs , for this kind of arrangement circuit is shown in fig.
When both the switches are in up position bulb gets neutral at both points hence it will be
in OFF-STATE . Now if position of any of the switch is changed the phase is applied to
one end of bulb and it becomes ON. Now if the position of other switch is also changed,
the bulb becomes OFF as phase gets applied at both the ends of bulb. Now if again
position of any off switch is changed ,the bulb becomes ON again.
A Different arrangement for stair-case wiring is shown in fig. In fig(a) Neutral(N) is
directly connected to the bulb and for Phase(P), cross connection are made in the two
switches. In fig.(b) neutral(N) is directly connected to the bulb and for phase(P) straight
connections are made in the two switches.
In cross connection, if both switches have same position( i.e. either at A or either at B)
lamp would not glow. Whereas in straight connection; if both switches have same position
of either switch has been changed, lamp change its position.

CIRCUIT DIAGRAM:
Fig 2.4 Circuit Diagram of Stair case wiring
OBSERVATION TABLE
POSITION
OF SWITCHES &
LAMPS
POSITION
OF SWITCHES
& LAMPS
POSITION
OF SWITCHES
& LAMPS
POSITION
OF SWITCHES
& LAMPS
S1 S2 LAMP S1 S2 LAMP S1 S2 LAMP S1 S2 LAMP

RESULT:
We studies about the house wiring and made connections for different house wiring
application viz. Stair-case wiring and a room wiring.
PREACAUTIONS:
1. No any connections should be loosed.
2. Do not touch any wire.
3. Do not keep any joint open.
4. Use M.C.B. and switches of proper current rating
EXPERIMENT # 2
OBJECT:

To study the construction and basic working of ceiling fan and connections of ceiling fan
with regulator.
APPARATUS REQUIRED:
S.No. Name of apparatus Range/Rating Type Quantity
1
Fan motor
(stator/rotor)
60W,0.6A,350rpm,230±10
%volts
1- squirrel cageᶲ
induction motor
1
2 Capacitor 2.5MFD±5%,440V AC
50Hz,MAX. temp.85
+
-| (--
1
3
Fan assembly
(Canopy/suspension
rob, blades etc.)
- - 1
4 Fan regulator (0 -350)rpm Resistance/electronics 1/1
5 Test lamp 200W 1
6 Different tools - - As per
requirement
7 Multimeter Analog/digital - 1
8 Voltmeter (0 -300)volts Moving coil 1
9 Ammeter (0 – 1) Amp. Moving coil 1
10 Connecting leads - - As per
requirement

THEORY:
CEILING FAN:
A ceiling fan is a propeller blades and having two or more blades, directly driven by an electric
motor and intended for use with free inlet & outlet. It is provided with a device for suspension
from ceiling of a room so that the blades rotate in a plane to give uniform air circulation in the
room.
According to the electric motor used, ceiling fans can be classified as follows:
1. DC FANS: DC fans uses series motors and generally used where dc supply is easily
available as like trains, buses etc.
2. AC FANS: AC fans are most commonly used domestic devices, which is generally known.
AC fans use single phase squirrel cage induction motor.
DIFFERENT PARTS OF CEILING FAN:
1. Motor
2. Capacitor
3. Blades
4. Canopy
5. Ball-bearings
6. Speed regulators
Fig 3.1 Construction Daigram of ceiling fan

Construction:
Main parts of a ceiling fan are:
(a) Winding
(b) Capacitor &
(c) Regulator
Winding of the motor can be done manually or by automated machine. Regulator may be
electronic type or resistance type. Electronic type regulator has negligible power loss and compact
size. But in the case of resistance type, resistances are connected in series with the circuit; this may
cause power loss as heat.
In table fan one permanent split capacitor run (PSC) motor is the heart of a fan. This motor
consists of two windings one as starting winding and other as running winding.
Starting winding of this motor has high resistance and low reactance but running winding has low
resistance and high reactance. One capacitor is connected in series with the starting winding and
whole of this circuit is put in parallel across running winding. In the case of ceiling fan these two
windings are placed in stator in the inner side of the fan.
Rotor has no winding; it is the outer body of the fan. Ceiling fan motor operates just in opposite
manner as compared to general motor. That is actual rotor of the motor is blocked and the stator is
free to rotate. So ceiling fan runs in anticlockwise direction. At the same time table fan motor is
operated as normal case and so it runs in clockwise direction. Capacitor connected in series with
the starting winding should be value 2.5 micro farad. Pyranel insulated foil paper capacitor is using
for this purpose. It helps to provide a split phase effect from single phase AC supply.
CIRCUIT AND WINDING DIAGRAM:

Fig 3.2 winding diagram of Ceiling fan Fig 3.3 circuit diagram of Ceiling fan
WORKING PRINCIPLE:
AC ceiling fan has single phase induction motor, which comprises two distributed windings stator
and a rotor (squirrel cage) when current is given to the motor , the magnetic field is experience a
force in the rotor to move it right angle to the field at the blades attached with the rotor displace the
air.
OBSERVATION TABLE:
Test for Condition of lamp Test result
1. Running winding
2. Starting winding
3. Earth test of fan
4. Capacitor
(a) Open test
(b) Short test
(c) Continuity test
RESULT:
We studied about the ceiling fan and performed various testing and get result as shown in
observation table.
PRECAUTIONS:
1. Do not touch any live wire or contact.
2. Make the proper connection as given in circuit diagram and it should checked by lab in
charge before switch ON the supply.

3. Save the winding of fan for any damage.
4. Handle the equipments carefully, which are used in the experiment.
5. Use only 200W lamp for testing purpose for saving any damage to windings due to high
current.
EXPERIMENT # 3
OBJECT:
Prepare the connection of single phase induction motor through 1-Phase Auto-transformer
and vary the speed.
APPARATUS REQUIRED:
Sr. No. Name of
Apparatus
Type Range Quantity
1. Single phase
Induction
Motor
Squirrel
Cage
230V, 2HP 1500 rpm 50 Hz 1
2. Voltmeter M I (0-600 V)/(0-300 V) 1/1
3. Ammeter M I 2A/5A 1/1
4. Auto
Transformer
Single Phase 230V/(0-270)V 1
5. Techo-meter Digital 0-2000rpm 1
6. Wattmeter Dyanmo-
meter
10/20A,300/600V,1800W/2000
W
2
THEORY:
Single Phase Induction Motor:
Most small power (generally below 2 kW) induction machines have to operate with single-phase
a.c. power supplies that are readily available in homes, and remote rural areas. When power
electronics converters are used three phase a.c. output is produced and thus three phase induction
motors may still be used. However, for constant speed applications (the most frequent situation),

the induction motors are fed directly from the available single-phase a.c. power grids. In this sense,
we call them single phase induction motors. To be self-starting, the induction machine needs a
travelling field at zero speed. This in turn implies the presence of two windings in the stator, while
the rotor has a standard squirrel cage. The first winding is called the main winding while the
second winding (for start, especially) is called auxiliary winding. Single phase IMs may run only
on the main winding once they started on two windings. A typical case of single phase single-
winding IM occurs when a three IM ends up with an open phase. The power factor and efficiency
degrade while the peak torque also decreases significantly. Thus, except for low powers (less than
¼ kW in general), the auxiliary winding is active also during running conditions to improve
performance. Three types of single-phase induction motors are in use today:
Fig 4.1(a) Circuit Diagram of spilt phase induction motor Fig 4.1(b) Phasor Diagram
SPLIT-PHASE INDUCTION MOTORS:
The split phase induction motor has a main and an auxiliary stator winding displaced by 90 or up
to 110-120 degrees (Figure 4.1a). The auxiliary winding has a higher ratio between resistance and
reactance, by designing it at a higher current density, to shift the auxiliary winding current I ahead
of main winding current I (Figure 4.1b). The two windings-with a 90 space displacement and a γ ˜
20-30 current time phase shift-produce in the air gap a magnetic field with a definite forward
travelling component (from m to a). This travelling field induces voltages in the rotor cage whose
currents produce a starting torque which rotates the rotor from to a (clockwise on Figure 4.1).
Once the rotor catches speed, the starting switch is opened to disconnect the auxiliary winding,
which is designed for short duty. The starting switch may be centrifugal, magnetic, or static type.
The starting torque may be up to 150% rated torque, at moderate starting current, for frequent
starts long-running time applications. For infrequent starts and short running time, low efficiency

is allowed in exchange for higher starting current with higher rotor resistance. During running
conditions, the split-phase induction motor operates on one winding only and thus it has a rather
poor power factor. It is used below 1/3 kW, generally, where the motor costs are of primary
concern.
CAPACITOR INDUCTION MOTORS:
Connecting a capacitor in series with the auxiliary winding causes the current in that winding I to
lead the current in the main winding Ia by up to 90. Complete symmetrization of the two windings
m.m.f. for given slip may be performed this way. That is a pure travelling air gap field may be
produced either at start (S = 1) or at rated load (S = S) or somewhere in between. An
improvement in starting and running torque density, efficiency and especially in power factor is
brought by the capacitor presence. Capacitor motors are of quite a few basic types:
SHADED POLE INDCUTION MOTOR:
Shaded pole motors have only one main winding and no start winding. Start winding means of
design that ring a continuous copper loop around a small portion of the motor pole. This “shaded”
that portion if the pole, causing the magnetic filed in the shaded area to lag behind the field in the
unshaded area. shaded pole motor impractical for most industrial or commercial use.
DIAGRAM:
Fig 4.2 Cross section of Single phase Induction motor

PROCEDURE:
1. Make connection as shown in fig.
2. Put input voltage at Zero.
3. Now slowly vary input voltage and measure the speed by tachometer.
4. Record the value of speed at various voltage.
OBERVATION TABLE:
S.No Input Voltage Speed(rpm)
1 50
2 100
3 150
4 175
5 200
6 230
RESULT:
Study the construction and basic working of ceiling fan, single phase induction motor and three
phase squirrel cage induction motor. Connect ceiling fan along with regulator and single phase
induction motor through auto-transformer to run and vary speed.
PRECAUTIONS:
1. Connection should be right and tight.
2. Main switch , starter and motor should be earthed.
3. Use of proper range of voltmeter and ammeter.
4. Don’t touch the shaft of the running motor.

EXPERIMENT # 4
OBJECT:
Prepare the connection of three phase squirrel cage induction motor through 3-Phase Auto-
transformer and vary the speed.
APPARATUS REQUIRED:
Sr. No. Name of
Apparatus
Type Range Quantity
1. Three phase
Induction
Motor
Squirrel
Cage
415V 50 Hz2 HP 1500 rpm 1
2. Voltmeter M I (0-600 V)/(0-300 V) 1/1
3. Ammeter M I 2A/5A 1/1
4. Auto
Transformer
Single Phase 230V/(0-270)V 1
5. Techo-meter Digital 0-2000rpm 1
6. Watt meter Dyanmo-
meter
10/20A,300/600V,1800W/2000
W
2
THEROY:
Three phase induction motor consists of silicon steel slotted core in which three phase copper wire
winding is done and connection brought out on terminal box. The motor is also made of silicon
steel stampings core slotted in which copper or aluminum bars are inserted and shorted by copper
or aluminum short circuiting rings on both sides .
The body is made of cast iron on which channel given by a fan fitted on the shaft of the motor on
rear side. The fan is covered by a sheet steel cowl . The connections of stator winding is made inter
is star or in delta . Low HP motors are connected in star , medium and high HP motors are
connected in star to delta or delta to star.

Fig 4.1 Three phase Induction motor
The three phase motor works on mutual induction principle. The three phase stator when supplied
with three phase acts as primary produces three rotating magnetic field links the rotor induces emf
in rotor and the current circulates in rotor bars through short circuiting rings , then force is exerted
on rotor conductors and the rotor rotates in the direction of rotation of the magnetic field and so
the three phase induction motor is hence self starting.
The directions of rotation of three phase rotating magnetic field can be reversed by inter changing
any two phases of the supply.
Construction Diagram of three – phase Squirrel Cage Induction Motor :
Fig4.2 Three- phase squirrel cage induction motor

CIRCUIT DIAGRAM:
Fig4.3 Circuit diagram of three phase induction motor
OBSERVATION TABLE:
S.No Input Voltage Speed(rpm)
1 80
2 200
3 260
4 300
5 360
6 400
RESULT:
We have study constructions’ and connection of moving coil & moving iron ammeters &
voltmeters, dynamometer type wattmeter and analog & digital energy meter) and constructions’ of
3-phase squirrel cage induction motor.
PRECAUTIONS:
1. Connection should be right and tight.

2. Main switch , starter and motor should be earthed.
3. Use of proper range of voltmeter and ammeter.
4. Don’t touch the shaft of the running motor.
EXPERIMENT # 5(A)

OBJECT:
To study the construction, circuit, working and application of the Fluorescent lamp.
APPARATUS REQUIRED:
THEORY:
A fluorescent lamp or fluorescent tube is a gas-discharge lamp that uses electricity to excite
mercury vapour. The excited mercury atoms produce short-wave ultraviolet light that then causes a
phosphor to fluoresce, producing visible light. A fluorescent lamp converts electrical power into
useful light more efficiently than an incandescent lamp. Lower energy cost typically offsets the
higher initial cost of the lamp. The lamp is more costly because it requires a ballast to regulate the
flow of current through the lamp while larger fluorescent lamps have been mostly used in
commercial or institutional buildings, the compact fluorescent lamp is now available in the same
popular sizes as incandescent and is used as an energy-saving alternative in homes.
The fluorescent lamps are a type of gas discharge device . The gas in the tube consists of some
inert gases (e.g. Argon) and a few drops of mercury at very low pressure . The inside of the tube is
coated with a phosphor substance or fluorescent powder. It convert U.V. radiation into visible light
. Since electric discharge of the inert gas at low pressure gives ultra – violet radiations . the
electrodes are in the form of oxide – coated tungsten filaments at both ends of tube.
Starter:
It’s appearance like a small glass bulb which consist of two electrode, one is fixed and other is
made up of U-shade bimetallic strips. Such type of starter is know as ‘glow type starter’ . A paper
capacitor may also be placed in parallel with a the to metallic strips . To avoid the welding up
S.N
o
Name of
Apparatus
Range Type Quantity
1. Fluorescent tube 40W,230V,50Hz,120cm. Tubula
r
1
2. Choke coil 40W,230V,cosΦ=.5 1
3. Starter Glow type for 20/40/65/80W tube 2
4. Test lamp 15/100/200W 1/1/1
5. Connecting leads As Per
Reuired

together of strips , we use resister and to avoid interference in radio and T.V. at the time of
switching the tube line ON.
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.7.1(a). 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 evapourated 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 vapourizes and helps to maintain the discharge.
CONSTRUCTION DIAGRAM:
Fig.7.1(a) Fluorescent Lamp

Fig.7.1(b) Fluorescent Lamp Inside View
Operation:
Fluorescent lamps are designed for switch start operation. A typical switch start circuit is shown in
Fig. c. The starter consists of two bimetallic contacts, housed in a small glass bulb filled with a
noble gas at low pressure. The contacts are positioned with a narrow separation between them.
When the normal voltage is applied, it creates a glow discharge between the bimetallic contacts
and due to heating they bend towards each other. The contacts touch each other for one or two
seconds and the current path is completed through the inductive ballast and the filament electrodes.
This current results in preheating the electrodes. As the bimetallic contacts touch, the glow
discharge stops and now the contacts cool down and leave apart to open the circuit. The sudden
break of current will induce a high voltage (600-1500V) in the ballast and is applied across -the
tube, which in turn trigger the discharge through the tube. The capacitor, which is connected across
the starter contact, is provided to reduce the radio interference due to switching operations. The
starter has no function once the lamp is started. Like other discharge lamps, fluorescent lamps are
also having a negative temperature coefficient of resistance. This means the resistance of the tube
decreases when temperature is increased, resulting in increase of current. Therefore the ballast is
essential during normal operation also to regulate the lamp current. When the ballast is connected
in series with the circuit, it regulates the lamp current. The capacitor across the supply line is for
power factor improvement.
When there is a discharge through the lamp, it produces radiations mainly in the ultraviolet region.
This radiation is converted to visible radiation by the phosphor coating on the inner side of the
glass tube.

Performance:
The luminous efficiency of the fluorescent lamp is around 75 lumens/watt, which is much higher
than incandescent lamps. The colour rendering index of this lamp is in the rage of 50-60 and this is
sufficient for normal domestic or commercial lighting.
Fluorescent tamps have an expected life varying from 6000 to 20000 hours. One disadvantage with
this lamp is that the power factor of the circuit is low (around 0.5), but this problem can be solved
to some extent by connecting a capacitor across the supply.
CIRCUIT DIAGRAM:
Fig.7.2 Fluorescent tube light circuit diagram

Fluorescent tube verses incandescent lamp
S.NO. POINT OF
CONSIDERATION
FLUORESCENT TUBE OR
LAMP
INCANDESCENT OR
FILAMENT LAMP
1 Initial cost High Low
2 Running cost Low, i.e. more economical
working
High
3 Life More (about 7500 working
hours)
Low (about 1000 working
hours)
4 Luminous efficiency High (40 lumens /watt) Low( 10 lumens /watt)
5 Heating effect Nil Lot of heat is evolved
6 Starting trouble May be there Nil
7 Illumination Gives shadow less diffused light
with no glare or glitter
Gives light with glare, and
shadow of dark, and bright
patches
8 Effect of frequent
switching on & off
Life reduced, since the coating
on the electrodes is destroyed at
each starting.
There is no such problem.
9 Fixing process Fixing, and fault finding is
somewhat difficult
Very easy process
10 Effect of voltage
fluctuations
Causes flickering of the tube Only intensity of light alters
11 Effect of voltage
supply
(1) its supply voltage is low
then the tube may blink a
number of times before
staring, and this process
reduces the life of tube.
(2) If voltage is high, then it
reduces the life of tube by
rapid deterioration of
cathode coating.
(1) an increase of 5% in
voltage increases light
output by 15%, but
reduces the life of the
bulb to half.
(2) A decrease of 5% in
voltage decreases the
output by 15%, but
increase the life of
bulb by about 100%.
12 Problem during
running condition
(1) it can produce humming
sound.
(2) A defective choke or
starter makes the staring
difficult, and shortens the
life of the tube.
No problem

RESULT:
To study the construction, circuit, working and application of the Fluorescent lamp have been
done.
PRECAUTIONS:
1. Tools should be used carefully.
2. Fitting should be tightly fitting.
3. Connection should be tight.
4. Wire should be on the conduit, power gripped properly.
EXPERIMENT # 5(B)
OBJECT:

To study the construction, circuit, working and application of the Sodium vapour lamp and
Halogen lamp.
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 coloured radiation at 589 nm
wavelength. This wave length has a specialty that it is very near to the peak of the eye sensitivity
curve.
Construction and operation:
There are two variants of sodium vapour lamps - low pressure and high pressure types. There is
slight difference in the construction of these two types.
Fig.7.3 (a) Low pressure sodium vapour lamp

Fig.7.3 (b) High pressure sodium vapour lamp
Above figure shows the construction of a low pressure sodium vapour lamp. The vapour pressure
of sodium is about 0.1 Pa for this type. The discharge tube is a U shaped glass tube. The inside of
the arc tube is coated with a sodium resistant glass layer. At the two ends of the tube, there are
coiled electrodes. When the lamp is not burning, the sodium will be in solid state deposited on the
inner side of the tube. At startup the lamp functions like a neon lamp with a characteristic pink
colour. As the temperature builds up, the sodium vapourizes and starts radiating yellow light. The
lamp shall give it full brightness within a few minutes.
There is an outer envelope for the lamp and the space between the discharge tube and the envelope
is vacuum. Vacuum is necessary to reduce the heat loss from the discharge tube. It is also
important to maintain the temperature of the discharge tube at around 260° C for generating proper
radiation.
In high pressure sodium vapour lamp, the vapour pressure is much higher (about 7000 Pa). At this
pressure, the radiation from the discharge covers a good part of the visible spectrum and therefore
the colour rendering properties improves. The temperature of the discharge tube is around 1300°
C. Fig 7.3(a) shows a typical construction of a high pressure sodium vapour lamp. The operating
temperature is much higher compared to the low pressure type. The arc tube is made of a
translucent ceramic material. This material is particularly selected because it does not react with
sodium or loose its shape even at higher temperatures. There is an outer envelope for the lamp and
the space between the arc tube and the envelope is vacuum or an inert gas filling.
Sodium vapour lamps are also having a negative temperature coefficient of resistance and
therefore require a ballast to control the current during normal operation. The lamp has another

requirement that for starting, it requires a higher voltage than the normal operating voltage. For
low pressure
Sodium vapour lamp, the starting voltage is around 450V and for high pressure type the striking
voltage is between 1000 and 4000 V. Fig. 7.3.(b) shows a typical circuit suitable for low pressure
sodium vapour lamp. An autotransformer with high leakage reactance is used for starting and to
control the current during normal operation. High leakage reactance results in higher voltage
regulation. At start the lamp current will be low and the high voltage required for starting will be
available from the auto transformer. As the sodium vapourized, the lamp current increases and due
to the high regulation of the autotransformer, the voltage falls to the normal operating voltage.
These circuits have low lagging power factor between 0.3 and 0.4 and to improve the power factor,
a capacitor is connected across the input.
Electronic igniters are available now for all types of discharge lamps. These igniters are designed
to give the high startup voltage required by discharge lamps.
Performance:
Low pressure sodium vapour lamps have very high efficacy of 100 to 180 lumens/watt. This is
mainly because the radiation produced is in the visible spectrum. On the other hand these lamps
have extremely low colour rendering index since the light output is monochromatic. Low pressure
sodium vapour lamps are available in the range of 18-180 W.
The colour rendering index of high pressure sodium lamps is better than low pressure type (about
25%), but the efficacy is slightly less (65 to 140 lumens/watt).
High pressure sodium vapour lamps are available in the range of 35 - 1000 W.
Due to the low colour rendering properties, the application for sodium vapour lamps is limited to
street lighting, security lighting etc where the colour discrimination is not important. The life of
these lamps is about 20000 hours.
Halogen Lamp:
The halogen lamp is the latest member in the family of incandescent lamp. It posses numerous in
the advantage over the ordinary incandescent lamp. As already stated the life and efficiency of an
incandescent lamp fall of with use-partly due to slow evapouration of the filament and partly due
to black deposit formed on the inside of the bulb. The addition of small amount of halogen vapours
to the filling gas restores port of the evapourated tungsten vapours back to filament by means of
chemical reaction i.e. there is a sort of regeneration cycle.

Fig 7.4 Halogen lamp
Advantage :
Halogen lamp posses the following advantage:
1. No blacking of lamp, hence no depreciation of lumens output.
2. High operating temperature with increased luminous efficiency varying from 10 lumens/watt to
33 lumens/watt.
3. Reduced dimension of lamp miniature size.
4. Long life-2000 hours.
OBESERVATION TABLE:
S.No
.
Lamp Lamp Turn
ON Time
Colour of Light Lamp Turn
OFF Time
Initial Final
1. HPSV Lamp
2. Halogen Lamp
RESULT:
The study of the construction, working & circuit of the sodium vapour lamp and halogen lamp
have been done.

PRECAUTIONS:
1. Lamps should be handled carefully.
2. All the connections should be tight.
3. Lamps should be kept & connected properly (horizontally/vertically).
4. Circuit must be get checked before switching on the supply.
5. Do not touch live wire/parts.
6. Switch off the supply, when not used.

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