Department of Computer Science Engineering
B. P. Poddar Institute of Management & Technology
Laboratory Report on
Basic Electrical Engineering Laboratory
(ES-EE191)
Name: _____________________________
Name: _____________________________
University Roll No: _____________________
University Roll No: _____________________
College Roll No: _______________________
College Roll No: _______________________
Year: ___________
Semester: _________
Year: ___________
Semester: _________
Section: _________
Group: ___________
Section: _________
Group:____________
Session: _____________________________
Session: _____________________________
General Information
Course Name
Basic Electrical Engineering
Laboratory
Course Code
Course Credit
Semester
1st
ES-EE191
Year with
stream
CSE, 1st Year
1
Session
2023-2024
Faculty
Instructor/s
Class hours and
total class load
2 hours/week per batch in
odd semester
Technical
Assistant/s
Laboratory
Room No. 104 (B-Block)
Program Specific Outcomes:
PSO1: Students will have proficiency in fundamental engineering and computing techniques and
knowledge on contemporary topics like artificial intelligence, data science and distributed computing
towards development of optimized algorithmic solutions.
PSO2: Students will have capabilities to participate in the development of software and embedded
systems through synergized teams to cater to the dynamic needs of the industry and society.
Course
Objectives
Understand the basic concept of various measuring instruments along with real
life circuit parameters.
Get knowledge of construction of different electrical machines.
Acquire knowledge of series and parallel ac circuits and its resonance condition.
Understand the need of calibration of measuring instruments
Get concept of process to measure power of three phase unbalanced circuit.
Acquire knowledge of working of single phase transformer along with its different
tests.
2
Safety Norms and precautions
1. Use of mobile phones during laboratory sessions is forbidden.
Do not
2. Late arrival is not permitted.
3. Under no circumstances is equipment to be removed from the lab.
1. You are expected to comply with instructions, written or oral, that the
instruction given you during the course of the laboratory session.
2. Students must familiarize themselves with the evacuation procedure.
Do
3. Observation book of the present lab experiment should be corrected on
the same day and record should be corrected on the next scheduled lab
session.
4. Prepare for the viva questions. At the end of the experiment, the lab
faculty will ask the viva questions and marks are allotted accordingly.
Course policies
1. Attendance
Attendance is compulsory. Please be respectful to your classmates by being on time. Cell phones
should be turned off and kept out of sight.
2. Calculator policy
You may need a calculator device
3. Plagiarism
Collaboration on performing the experiments and taking measurements is strongly encouraged;
however, the lab report you hand in must be solely your own. Sharing written work beforehand is
considered as academic dishonesty
4. Disability Support
If you have a disabling condition which may interfere with your ability to successfully complete this
module, please contact Faculty in charge
5. Make-up Experiment
Make-up for a missing experiment will not be offered, normally. The only exceptions to that are
illness or emergency (e.g., death in family, a traffic accident, etc.), in which case you may contact
your faculty in charge.
6. Experiments Outside Curriculum
As per policy you have to perform at least two innovative experiments from the list of innovative
experiments to be provided
7.Innovative Micro-project
One innovative Micro-project is to be performed during the semester and the report is to be
submitted at the end of the session.
8.Instruction Set
Complete instruction sets has been provided at the end of the report.
3
Course Assessment Process
Continuous Assessment (40)
A. Laboratory Reports [15%]
Experiment number, Objective, theory, procedure, results, discussion and conclusion
B. Laboratory Performance [50%]
Attendance and Day to day performance etc.
C. Questions and Quizzes at the end of each experiment (15%)
D. Internal Assessment Test (20%)
Assessment During End Semester Examination (60)
A. Circuit Preparation and Laboratory Performance during Semester Examination
[33%] Experiments are allotted to the students randomly on lottery basis during examination
which they have to complete within stipulated time.
B. Viva Voce [33%]
There is a viva-voce during examination.
C. Answer Script of Laboratory Examination [33%]
A brief description on allotted experiment along with data and results must be submitted at the
end of the examination.
Grading Scale
Recommended
books
Grade
Percent score
O
≥ 90
E
≥ 80 and < 90
A
≥ 70 and < 80
B
≥ 60 and < 70
C
≥ 50 and < 60
D
≥ 40 and < 50
F
< 40
1. D. P. Kothari and I. J. Nagrath, “Basic Electrical Engineering”,
Tata McGraw Hill, 2010.
2. D. C. Kulshreshtha, “Basic Electrical Engineering”, McGraw Hill,
2009.
3. V. D. Toro, “Electrical Engineering Fundamentals”, Prentice Hall
India, 1989.
4
List of experiments:
Exp.
No.
Name of Experiment
1
General Laboratory rules and
precautions for electrical safety.
2
Introduction and uses of the
following:
i) Voltmeter ii) Ammeter iii) Multi
meter iv) Oscilloscope.
Demonstration of real-life resistors,
capacitors with color-code,
inductors and auto-transformers.
3
Demonstration of cut-out section of
machines.
4.
Calibration of Ammeter & Watt
meter
5.(a)
5.(b)
6.
Transient response of series R-L
Network.
Transient response series of R-C
Network.
Determination of steady state
response of R-L-C circuit and
calculation of impedance and
power factor.
7.
Resonance of R-L-C series circuit
8.
i) Open-circuit and short-circuit test
of 1-ф transformer
ii) Load test of 1-ф transformer
9.
10.
Page
No.
Measurement of power in a three
phase balanced and unbalanced
circuit by two wattmeter method.
Experiment outside curriculum.
5
Date of
Experiment
Grade
awarded
Signature
Experiment No: 1
Title: General Laboratory rules and precautions for electrical safety.
Objective:
1. To understand the rules of the electrical laboratory.
2. To describe the basic precaution for electrical safety.
Theory:
Following general rules and precautions are to be observed all times in the laboratory.
1.
There must be at least two people in the laboratory while working on live circuit.
2.
Shoes must be worn at all the times.
3.
Remove all lose conductive jewelry which may come in contact with the exposes circuit.
4.
Do not wear long loose tie, scarf and other loose clothing around machine.
5.
When taking measurement, form the habit of using only one hand at a time.
6.
No part of live circuit should be touched by bare hand.
7.
Keep the body out of the circuit where interconnecting wires and cables are involved.
8.
In the work area, the benches and the space should be kept clean. Clear the item which is
not used in the experiment.
9. Always check to see whether the power switch is off before plugging in the outlet. Then turn
the Instrument /equipment off before unplugging from the outlet.
10. When unplugging the power cord, pull the plug not on the table.
11. When keys are inserted in a circuit, first remove source of power.
12. No underground electrical and electronic apparatus are to be used in the laboratory unless
they are doubly insulated.
13. Report any damage to the equipment, partial hazard to laboratory instructor.
14. If in doubt about electrical safety ask the laboratory instructor properly.
15. Regarding specific equipment consult the manual provided by the manufacturer of the
equipment.
6
Outcome of the experiment:
PO1
PO2
PO3
PO4
PO5
PO6
PO7
PO8
PO9
PO10
PO11
PO12
Questionnaires:
Grade awarded
Lab record:
Lab Performance:
Viva:
Teacher’s signature with date_______________________
7
PSO1
PSO2
Experiment No: 2
Title: Introduction and uses of the following: i) Voltmeter ii) Ammeter iii) Multi
meter iv) Oscilloscope.
Demonstration of real life resistors, capacitors with color-code, inductors and
auto-transformers.
Objective:
1. To explain the uses of voltmeter, ammeter, multimeter, oscilloscope.
2. To demonstrate real life resistors, capacitors with color code, inductors and
autotransformers.
Theory:
Meters are tools used to measure different parameters in the circuit. They are very useful instrument
that can be utilized in a number of field. There are two type of meter. One begin the analog and other
is the digital. The primary difference between the two is, the display of an analog meter uses a needle
to show the value while a digital meter will show the result as number on screen.
Most analog electric meters make use of a galvanometer .A galvanometer is a device constructed
such that deflection of needle is proportional to current through a coil around the base of a needle. It
is used to find direction of current and its magnitude. The resistance of a galvanometer is usually
several ohms. Typically a current of a fraction of one milliamp will cause full scale deflection. Therefore
it cannot measure high value of voltage and current.
Voltmeter: Voltmeter is an electrical measuring device which is used to measure potential difference
between two points in a circuit. In order to convert a galvanometer in to voltmeter a very high resistance
known as “series resistance” is connected in series with the galvanometer.
Let, resistance of galvanometer Rg, Resistance Rx is connected in series to it. The combined
resistance= (Rg+Rx).If potential between the points to be measured=V and if galvanometer gives full
scale deflection when current Ig passes through it, then
V= Ig (Rg+Rx)
Rx= (V-IgRg)/Ig
Ammeter: Ammeter is an electrical measuring device which is used to measure electric current
through the circuit. In order to convert a galvanometer in to an ammeter a very low resistance known
as “shunt” resistance is connected parallel to galvanometer is converted in to ammeter. An ammeter
is connected in series to a circuit.
Let, resistance of galvanometer Rg, and it gives full scale deflection when current Ig is passed through
it. Then
Vg=IgRg ………………...... (i)
Let a shunt of resistance is connected in parallel to galvanometer. Then the current through shunt
Is = (I - Ig). Vs=Is Rs
Vs = (I-Ig) Rf .................... (ii)
Vs=Vg
(I-Ig) Rs=Ig Rg
Rs= Ig Rg / (I-Ig)
8
Multi meter: A digital multi meter or DMM is one of the most widely used pieces of test equipment
today. The standard and basic measurement performed by multi meter are the measurement of amp,
volt and ohm. A parts from that these digital multi meters perform many additional measurement by
using digital and logic technology. These may include temperature, frequency, continuity, Capacitance
etc. The new improved integrated circuit of digital multi meter are more efficient and work with a large
accuracy as compared to an analog multi meter.
Oscilloscope: The oscilloscope is an electronic instrument widely used in making electronic
measurement. The main component of the oscilloscope is the cathode ray tube or CRT. The CRT
consist of a vacuum tube in which electrons are boiled off a cathode and accelerated using an electric
field toward a phosphorescent screen. When the electrons strike the screen, a burst light is given off.
The beam is deflected along the way by vertical and horizontal plates that use electric fields to deflect
the electrons. The screen of the oscilloscope has a grid on it called a gradecule. The dials on the
oscilloscope give the scale of the gradecule in volts in the vertical direction and second in the horizontal.
Autotransformer: It is an electrical transformer with only one winding. Same portion of the winding
act as primary and secondary sides of the transformer. It works as a step-down transformer i.e. bring
out a high voltage into a low voltage automatically.
REAL LIFE RESISTORS:
When real resistors are made, the goal is that the component that is being created should be as close
as performing the ideal resistor equation based on ohm’s law which says, V=IR.
The resistance value of a resistor depends on:
(a) The material of the wire.
(b) The shape of the wire.
The bulk material affects as how difficult it is for electrons to pass through. This property is known as
resistivity and it’s reciprocal as conductivity. Again a longer resistor has high resistance than a shorter
one because as the electrons suffer more collision as they pass through the atoms of the material.
Resistor with greater cross sectional area has lower resistance because electrons have a greater
number of available paths to follow.
A real resistor breaks down if the power dissipated by the resistor is greater than what construction
material can withstand.
9
COLOUR CODE OF RESISTORS:
Color
Black
Brown
Red
Orange
Yellow
Green
Blue
Purple
Gray
White
Gold
Silver
Band1
0
1
2
3
4
5
6
7
8
9
Band2
0
1
2
3
4
5
6
7
8
9
Band3
0
1
2
3
4
5
6
7
8
9
Multiple
100 (1Ω)
101 (10 Ω)
102 (100 Ω)
103 (1000 Ω)
104 (10 KΩ)
105 (100 KΩ)
106 (1 MΩ)
107 (10 MΩ)
108 (100 MΩ)
109 (1 GΩ )
10 -1 (100 MΩ)
10 -2 (10 MΩ )
Tolerance
= ± 1%
= ± 2%
= ± 0.5%
= ± 0.25%
= ± 0.1%
= ± 0.05%
= ± 5%
= ± 10%
REAL LIFE CAPACITORS:
While making capacitors, the component should be close to performing the ideal capacitor equation,
I=C dv/dt.
A capacitor is constructed from two conducting surface placed close to each other between the
plates, there can be air or any insulating material. The capacitance value depends on the area of
plates, thickness of insulator and physical properties of insulating material.
Tolerance
Tolerance Temperature
Band Color Digit A
Digit B
Multiplier D
T>10pf
T<10pf
Coefficient
Black
0
0
x1
± 20%
± 2.0pF
Brown
1
1
x10
± 1%
± 0.1pF
-33×10-6
Red
2
2
x100
± 2%
± 0.25pF
-75×10-6
Orange
3
3
x1,000
± 3%
-150×10-6
Yellow
4
4
x10,000
± 4%
-220×10-6
Green
5
5
x100,000
± 5%
Blue
6
6
x1,000,000
Violet
7
7
Grey
8
8
x0.01
+80%,-20%
White
9
9
x0.1
± 10%
Gold
x0.1
± 5%
Silver
x0.01
± 10%
± 0.5pF
-330×10-6
-470×10-6
-750×10-6
10
± 1.0pF
REAL LIFE INDUCTORS:
It is a coil or choke which is a passive two terminal electrical component that stores energy in a
magnetic field when electric current flows through it. The working component of the inductor should
be based on the ideal inductor equation, V=L di/dt.
Result:
11
Outcome of the experiment:
PO1
PO2
PO3
PO4
PO5
PO6
PO7
PO8
PO9
PO10
PO11
PO12
Questionnaires:
Grade awarded
Lab record:
Lab Performance:
Viva:
Teacher’s signature with date_______________________
12
PSO1
PSO2
Experiment No: 3
Title: Demonstration of cut-out section of machines.
Objective:
1. To explain different parts of a D.C. Machine and their equivalent features.
Theory:
1. DC Machine: A DC Machine is an electro-mechanical energy conversion device. There are two
types of DC machines; one is DC generator, and another one is known as DC motor. A DC
generator converts mechanical power (ωT) into DC electrical power (EI), whereas, a DC motor
converts d.c electrical power into mechanical power. Generally a D.C. machine consist of the
following parts.
Yoke: It is made of cast iron or cast steel. It provide magnetic flux path, holds the structure and protect
the machine from environment. It carries half of the flux produced by the pole.
Field: The salient poles are bolted to the inner periphery of the yoke. Poles are bolted to the inner
Periphery of the yoke. Poles are made of stack of steel stamped of thickness 1-1.5mm.Field
winding consist of a number of terms of enamel insulated cu wires. The windings, concentric in
nature and are of two types. The first shunt field is mounted over pole core and is of high
resistance. The second, series field is mounted over shunt field for better cooling purpose and
convenient for construction. It has a low resistance. The pole shoe is also laminated to reduce eddy
current losses.
Brushes & Brush holders: It is made of graphite for low voltage machine and it is of cu to reduce
voltage drop across resistance.
Armature: The armature is made up of stack of soft iron with circular lamination of thickness 0.5 mm.
The periphery of this lamination is slotted to receive the distributed armature winding. They are
insulated from each other by cast iron of furnish to reduce eddy current losses. The lap connected
armature winding is used for high current low voltage machine. Whereas the wave connected armature
winding is used for low current high voltage machine.
Commutator: It is made of a wedge shaped hard drawn cu. The number of commutator segments are
equal to the number of armature coils. The cu segments are insulated from each other by a layer of
mica.
Shaft & Bearings: Shaft is made of mild steel and supported at the end on bearing.
13
CUT SECTION OF DC MACHINE:
2. Induction Motor: An induction motor is a type of electric motor that converts electric power into
rotary motion. An induction motor uses the principle of electromagnetic induction to cause the rotor
to turn. The induction motor was created and patented by Nikola Tesla in 1888. Electric current is
supplied to the stator, which induces a magnetic field that rotates. The rotating magnetic field
interacts with the rotor, inducing current in the rotor. The interaction of the two magnetic fields
results in a torque, turning the rotor within the motor casing. Because the induction motor does not
use brushes like DC motors, there is less wear of the internal parts.
Different parts of an Induction Motor are:
Stator: The stator is the stationary portion of the motor and delivers a rotating magnetic field to
interact with the rotor. One or more copper windings make up a "pole" within the stator, and there
is always an even number of poles within a motor. The electric current alternates through the poles,
resulting in a rotating magnetic field.
Rotor: The rotor is the central component of the motor, and is fixed to the shaft. The rotor is
generally constructed of copper or aluminum strips attached at each end to a circular fixture. This
configuration is called a "squirrel cage rotor" because of its appearance. The magnetic field
generated by the stator induces a current in the rotor, which then creates its own magnetic field.
The interaction of the magnetic fields in the stator and rotor results in a mechanical torque of the
rotor. In some induction motors, the copper bars are replaced with slip rings and copper windings
that behave in the same way.
14
Bearings: The rotor shaft is held in place by bearings at either end of the motor casing. The
bearings minimize the friction of the shaft connection to the casing, increasing the efficiency of the
motor.
Casing: The casing of the induction motor contains all of the motor components, provides electrical
connections and allows for ventilation of the motor parts to reduce heat buildup. The casing design
often includes fins to assist with heat dissipation.
CUT SECTION OF INDUCTION MOTOR:
3. Synchronous Machine: In a synchronous generator, a DC current is applied to the rotor winding
producing a rotor magnetic field. The rotor is then turned by external means producing a rotating
magnetic field, which induces a 3-phase voltage within the stator winding.
Field windings are the windings producing the main magnetic field (rotor windings). Armature
windings are the windings where the main voltage is induced (stator windings).
A synchronous machine is an AC machine whose satisfactory operation depends upon the
maintenance of the following relationship.
Where,
• Ns is the synchronous speed in revolution per minute (r.p.m)
• f is the supply frequency
• P is the number of poles of the machine.
When connected to an electric power system, a synchronous machine always maintains the above
relationship shown in the equation (1).
15
If the synchronous machine working as a motor fails to maintain the average speed (Ns) the
machine will not develop sufficient torque to maintain its rotation and will stop. Then the motor is
said to be pulled out of step.
In case, when the synchronous machine is operating as a generator, it has to run at a fixed speed
called Synchronous speed to generate the power at a particular frequency. As all the appliances
or machines are designed to operate at this frequency. In some countries, the value of the
frequency is 50 Hz.
CUT SECTION OF SYNCHRONOUS MACHINE:
16
OBSERVATIONS:
Sl.No.
Name of the part
1.
Slots(number of slots)
2.
Length of commutator
3.
No. of segments
4.
Width of commutator
5.
Depth
6.
Pole pitch
7.
Length of armature
8.
Shoe width
9.
Yoke width
10.
Length of shaft
11.
Core
Measurement
Outcome of the experiment:
PO1
PO2
PO3
PO4
PO5
PO6
PO7
PO8
17
PO9
PO10
PO11
PO12
PSO1
PSO2
Questionnaires:
Grade awarded
Lab record:
Lab Performance:
Viva:
Teacher’s signature with date_______________________
18
Experiment No: 4
Title: Calibration of Ammeter & Watt meter
Objective:
1. To calibrate Test Ammeter & Watt meter with a Standard Ammeter and Voltmeter.
Theory:
An Ammeter is an instrument that measures electric current and a wattmeter is an instrument that
measures electric power.
For pure resistive load P=V×I where P is power consumed by the load. V is voltage across and I is
current through the load.
To calibrate, the reading of the test instruments are compared with a standard instrument. The
difference is called error. The error may be positive or negative.
The error may be calculated as, (standard reading - test reading).
The percentage error is calculated as,
％error=(standard reading - test reading)/standard reading ×100%
Circuit Diagram:
Procedure:
1. Connection is made as shown in the figure.
2. The load is disconnected. The reading of ammeters and wattmeter are noted for no load condition.
3. Any zero error of test meters can be adjusted now. If it is allowed to remain, it would only give a
19
definite offset to the error.
4. The load is connected by setting the switch on.
5. The supply voltage is varied with the help of variac and ten sets of observations are noted covering
the entire range of various meters.
Devices under test:
Name of
device
Quantity
Type
Rating
Maker`s
SL.no
name
Ammeter
Wattmeter
Apparatus used:
Name of
apparatus
Quantity
Type
Rating
Maker`s
name
Voltmeter
Ammeter
Variac
Load
20
SL.no
Experimental Data:
S.
no.
Input
voltag
e
Test
ammete
r
VS
AT
(V)
(A)
Standard Test
Standard
Error
ammeter wattmeter wattmeter
Ammeter Wattmete
WS
AS
WT
r
(watt)
(A)
(watt)
1
2
3
4
5
6
7
8
9
10
Calculation:
21
%Error
Ammete
r
Watt-meter
Outcome of the experiment:
PO1
PO2
PO3
PO4
PO5
PO6
PO7
PO8
PO9
PO10
PO11
PO12
Questionnaires:
Grade awarded
Lab record:
Lab Performance:
Viva:
Teacher’s signature with date_______________________
22
PSO1
PSO2
Experiment No: 5(a)
Title: Transient response of R-L Network.
Objective:
1. To study the response of a series R-L circuit, where R=5 Ω, L=1H.
Theory:
Analysis of behavior of electric circuit reveals that as soon as a circuit is switched from one condition
to another either by change of source or by alteration of circuit elements, branch currents and voltage
drops change from their initial values to new values. These changes take a short spell of time to settle
to permanent values (steady state) till further switching or circuit alteration is attempted. This brief spell
of time is called transient time and the value of the variables (current and voltage drop) during this
period is called transient value.
Let us consider the circuit as shown in the diagram.
When switch is connected, the R-L combination is suddenly put across the voltage of V volt. It is found
that current does not reach its maximum value instantaneously but takes some finite time.
We will now investigate the growth of current i through such an inductive circuit. Applying KVL, we can
write, V= (VR+VL) = (iR=L di/dt)
After derivation, we get,
iL=(V/R).(1-exp-(Rt/L)
γ = L/R is known as the time constant of the circuit and is defined as the time at which the current rises
to 63% of its steady state value which is V/R.
Circuit Diagram:
23
Circuit Diagram in Pspice simulation:
24
Graph:
25
Outcome of the experiment:
PO1
PO2
PO3
PO4
PO5
PO6
PO7
PO8
PO9
PO10
PO11
PO12
Questionnaires:
Grade awarded
Lab record:
Lab Performance:
Viva:
Teacher’s signature with date_______________________
26
PSO1
PSO2
Experiment No: 5(b)
Title: Transient response of R-C Network.
Objective:
To simulate and study the transient response of a series R-C circuit, where, R=5 Ω, C=1F
Theory:
Let us consider the circuit as shown in the diagram.
When switch is closed, the capacitor C is charging from the battery. The voltage across C does not
rise to V instantaneously but builds up slowly i.e. exponentially and not linearly. Charging current iC
is maximum at the start i.e. When C is uncharged, then it decreases exponentially and finally ceases
when potential difference across capacitor plates become equal and opposite to the battery voltage
V.
The applied voltage V is always equal to the sum of:
(i) Resistive drop (iC R) and (ii) voltage across capacitor (VC).
V= (iC R) +VC.
After derivation, we get voltage across capacitor,
VC=V [1 – exp (-t/RC)]
.................................... (i) and current
iC= IO[ exp (-t/RC)]
.....................................ii)
T=RC is known as the time constant of the circuit and is defined as the time at which the current falls
to 37% of its steady state value which is V/R.
Circuit Diagram:
27
Circuit Diagram in Pspice simulation:
28
Graph:
29
OUTCOME OF THE EXPERIMENT:
PO1
PO2
PO3
PO4
PO5
PO6
PO7
PO8
PO9
PO10
PO11
PO12
Questionnaires:
Grade awarded
Lab record:
Lab Performance:
Viva:
Teacher’s signature with date_______________________
30
PSO1
PSO2
Experiment No: 6
Title: Determination of steady state response of R-L-C circuit and calculation of
impedance and power factor.
Objective:
•
•
•
To determine different parameters (e.g., Resistance, Inductance & Capacitance) of an
Electrical circuit.
To determine total circuit impedance.
To determine power factor & phase angle for a given circuit
Theory:
A circuit is referred as series circuit if same current flow through all the parameters of the circuit (i.e.,
R,L and C).An alternating voltage of r.m.s. value(v) when applied to an R-L-C series circuit, it produces
alternating current having r.m.s. value (I) given by
I=V⁄Z
where, impedance (Z) = √ (R2 + X2)
X=XC-XL,
XC> XL
and
X=XL-XC,
XL> XC
Note: where X= Net Reactance, XL= Inductive Reactance, XC = Capacitive Reactance.
In a 1-φ A.C. Circuit,
Power, P = V I Cos φ
=Voltage × Current ×Power factor.
Here, Power factor = (Total circuit Resistance) / (Total circuit Impedance)
Cos φ = R / Z
φ=Cos-1 (R/Z)
Where, “φ” is the angle between voltage and current called power factor angle.
Power factor is lagging when XL > XC. Since the current I lags behind V by angle φ. But power factor
is leading when XC > XL , since the current I leads voltage V at an angle φ.
31
Circuit Diagram:
Apparatus used:
SL.NO.
Name of the
Apparatus:
Range
32
Maker’s name
Maker’s serial
no:
Experimental Data:
Sl.N
o
Applied
Voltage
Circuit
Current
(V)
(I)
In volts
In amps
Voltage
Voltage
drop across
across
Resistance Choke(VChoke)
(VR)
In Volts
In Volts
Voltage
drop
across
Resistanc
e & Choke
(VRL)
In Volts
Calculation:
33
Voltage
across
Capacitan
ce(VC)
In Volts
Power
(P) in
Watts
Outcome of the experiment:
PO1
PO2
PO3
PO4
PO5
PO6
PO7
PO8
Questionnaires:
34
PO9
PO10
PO11
PO12
PSO1
PSO2
Grade awarded
Lab record:
Lab Performance:
Viva:
Teacher’s signature with date_______________________
35
Experiment No: 7
Title: Resonance of R-L-C series circuit
Objective:
To determine the frequency, band width and Q-factor of R-L-C series circuit.
Theory:
If such a R-L-C circuit be connected across an a.c source of constant voltage V but of frequency
varying from zero to infinity then there would be a certain frequency of the applied voltage, which would
make XL equal to XC in magnitude. In that case X=0 and Z=R. under this condition the circuit is said to
be in electrical resonance. XL-XC = 0, XL=XC=2ᴫf*L= 1/2ᴫf*C.
Resonance is a particular condition when reactance becomes zero. The circuit impedance will be
minimum for series resonance R-L-C circuit at unity power factor.
In above R-L-C series circuit the voltage source is connected between nodes 1 & 0, Inductor is
connected between nodes 1 & 2, the capacitor is connected between nodes 2 & 3 and resistor is
connected between nodes 3 & 0.
The resonating frequency, fr = 1/2ᴫ√ (LC) and from the graph plotted for frequency against voltage
across resistor we get, Q = fr / ∆f, ∆f = (f2-f1)
Circuit Diagram:
36
Observations:
Input Voltage Vin =
SL.NO
Frequency(HZ)
Output Voltage across R
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
37
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
Calculation:
38
Outcome of the experiment:
PO1
PO2
PO3
PO4
PO5
PO6
PO7
PO8
PO9
PO10
PO11
PO12
Questionnaires:
Grade awarded
Lab record:
Lab Performance:
Viva:
Teacher’s signature with date_______________________
39
PSO1
PSO2
Experiment No: 8
Title: i) Open-circuit and short-circuit test of 1-ф transformer
ii) Load Test of 1-ф transformer
Objective:
To obtain the Open-circuit characteristic (magnetization curve) and the short circuit characteristics of
1-ф transformer. Also to find the parameters of it. Electrical equivalent circuit and then to determine
its regulation and efficiency.
Theory: A transformer is a static electromagnet device by which the voltage level of a source of
alternating current can be increased or decreased. From these view point there are two types of
transformers - step up transformer and step down transformer.
Transformer can transfer electric power from one circuit to another circuit without change of frequency.
It can electrically isolate secondary circuit from primary circuit.
From electrical point of view, transformer has mainly two parts i.e., core and windings. Windings are
made up of conducting material copper. Core is made up of magnetic material, generally silicon steel.
Open Circuit Test:
It is performed to measure the iron losses.HT side kept open & rated voltage is applied at LT side.
No load current = 𝐼𝑂
Iron losses
= 𝑊𝑂
Voltmeter reading = 𝑉𝑂
𝐼𝑒 =
𝑊𝑂
𝑉𝑂
𝐼𝑒 = energetic component/core loss component
𝐼𝑚 = √(𝐼𝑂 2 − 𝐼𝑒 2 )
𝑅𝑂 = 𝑉𝑂 /𝐼𝑒
𝐼𝑚 = magnetizing component
&
(𝑅𝑂 ,𝑋𝑂 refer to LT side)
𝑋𝑂 = 𝑉𝑂 /𝐼𝑚
Short Circuit Test:
It is performed to measure the equivalent resistance & the leakage reactance of the transformer.LT
winding is short circuited & a low voltage is gradually applied at the HT side.
Let the various readings are 𝑊𝑠𝑐,𝑉𝑆𝐶 , 𝐼𝑆𝐶 .
𝑅 𝑒𝑞 = 𝑊𝑠𝑐/𝐼𝑆𝐶 2
𝑍𝑒𝑞 = 𝑉𝑆𝐶 /𝐼𝑆𝐶
(𝑅 𝑒𝑞 ,𝑋𝑒𝑞 , 𝑍𝑒𝑞 are referred to HT side)
𝑋𝑒𝑞 = √(𝑍𝑒𝑞 2 − 𝑅 𝑒𝑞 2 )
Load Test: Load Test helps to determine the total loss that takes place, when the transformer is loaded.
40
Unlike the tests described previously, in the present case nominal voltage is applied across the primary
and rated current is drown from the secondary.
Load test is used mainly
1. To determine the rated load of the machine and the temperature rise
2. To determine the voltage regulation and efficiency of the transformer. Rated load is determined by
loading the transformer on a continuous basis and observing the steady state temperature rise.
The losses that are generated inside the transformer on load appear as heat. This heats the
transformer and the temperature of the transformer increases. The insulation of the transformer is the
one to get affected by this rise in the temperature. Both paper and oil which are used for insulation in
the transformer start getting degenerated and get decomposed. If the flash point of the oil is reached
the transformer goes up in flames. Hence to have a reasonable life expectancy the loading of the
transformer must be limited to that value which gives the maximum temperature rise tolerated by the
insulation. This aspect of temperature rise cannot be guessed from the electrical equivalent circuit.
Further, the losses like dielectric losses and stray load losses are not modeled in the equivalent circuit
and the actual loss under load condition will be in error to that extent. Many external means of removal
of heat from the transformer in the form of different cooling methods give rise to different values for
temperature rise of insulation. Hence these permit different levels of loading for the same transformer.
Hence the only sure way of ascertaining the rating is by conducting a load test
Circuit Diagram:
Open Circuit Test:
41
Short Circuit Test:
Apparatus Used:
SL.
NO.
Name of Apparatus
Quantity
Range
42
Maker’s name
Maker’s serial no.
Procedure:
For open circuit test:
1. H.V.winding of the transformer is made open.
2. Supply is given to the L.V. side.
3. The applied voltage is varied gradually up to rated voltage.
4. The reading of𝑉𝑂 ,𝐼𝑂 ,𝑊𝑂 ,𝑉2 are noted down.
For short circuit test:
1. The L.V.winding of the transformer is kept shorted.
2. Supply is given to the H.V. side
3. The applied voltage is varied gradually to get rated current.
4. The reading of𝑉𝑆𝐶 , 𝐼𝑆𝐶 ,𝑊𝑆𝐶 are noted down.
For Load Test:
1. Supply is given to the L.V. side and kept as 115V through Variac.
2. HV side is connected with the load box.
3. The reading of load voltage, load current and power consumed are noted down.
43
Observations:
For open circuit test
SL.NO.
VO
IO
WO
V2
For short circuit test
SL.NO.
Vsc
Isc
Wsc
For load test
SL.NO.
Vin
Vout
IL
44
WL
Calculation:
Outcome of the experiment:
PO1
PO2
PO3
PO4
PO5
PO6
PO7
PO8
45
PO9
PO10
PO11
PO12
PSO1
PSO2
Questionnaires:
Grade awarded
Lab record:
Lab Performance:
Viva:
Teacher’s signature with date_______________________
46
Experiment No: 9
Title: Measurement of power in a three-phase balanced circuit by two wattmeter method.
Objective: To measure the power in a balanced 3-ф circuit using two 1-ф wattmeters.
Theory: Two Wattmeter Method can be employed to measure the power in a 3 phase, three wire star
or delta connected the balanced or unbalanced load. In Two wattmeter method the current coils of the
wattmeter are connected with any two lines, say R and Y and the potential coil of each wattmeter is
joined on the same line, the third line i.e. B as shown below in figure.
The total instantaneous power absorbed by the three loads Z1, Z2 and Z3, are equal to the sum of the
powers measured by the two wattmeters, W1 and W2.
Considering the above figure (A) in which Two Wattmeter W1 and W2 are connected, the
instantaneous current through the current coil of Wattmeter, W1 is given by the equation shown below.
Instantaneous potential difference across the potential coil of Wattmeter, W1 is given as
Instantaneous power measured by the Wattmeter, W1 is
The instantaneous current through the current coil of Wattmeter, W2 is given by the equation
Instantaneous potential difference across the potential coil of Wattmeter, W2 is given as
Instantaneous power measured by the Wattmeter, W2 is
47
Therefore, the Total Power Measured by the Two Wattmeters W1 and W2 will be obtained by adding
the equation (1) and (2).
Where P – the total power absorbed in the three loads at any instant.
Circuit Diagram:
48
Apparatus used:
SL.NO.
Name of
apparatus
Type
Range
Makers name
Procedure:
1.
2.
3.
4.
Make the connections as per the circuit diagram.
Switch on AC supply.
For balanced load conditions, measure the values of wattmeters, ammeters, voltmeters.
Switch off all the loads and supply.
49
Phasor Diagram of 3-ф power measurement by two-wattmeter method.
50
Observations:
SL.
NO.
Voltmeter
reading
(V)
Ammeter
reading(A)
Wattmeter
reading(W1)
51
Wattmeter
reading(W2)
Total power in
Watts (W1+ W2)
Percent error
(%)
Calculation:
52
Outcome of the experiment:
PO1
PO2
PO3
PO4
PO5
PO6
PO7
PO8
PO9
PO10
PO11
PO12
Questionnaires:
Grade awarded
Lab record:
Lab Performance:
Viva:
Teacher’s signature with date_______________________
53
PSO1
PSO2
54
55
56
57
58
59
60