electric-generator.docx

lOMoAR cPS D| 2100 7711
KENDRIYA VIDHYALAYA NO.1
H.E.C COLONY RANCHI – 834004
AC GENERATOR
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NAME:
CLASS:
ROLL NO.:
SUBMITTED TO:

PHYSICS PROJECT
WORK
AC GENERATOR
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INDEX
CONTENT PAGE NO.
Certificate 4
Acknowledgement 5
Introduction 6
Theory and Working 7
Component of ACGenerator 8-11
Efficiency 12
Result 13
Uses 14
Losses in AC Generator 15-16
Precautions 17
Bibliography 18
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CERTIFICATE
This is to certify that of class –XII has
successfully complete the project on the topic AC
GENERATOR under the guidance of during
the year 2022-2023 in the partial fulfilment of the physics
practical examination conducted by the CBSE
SIGN. OF EXTERNAL EXAMINER SIGH OF TEACHER
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ACKNOWLEDGEMENT
I would like to express my immense gratitude to my physics teacher
for the help and
guidance he provided for completing this project.
I also thank my parents who gave their ideas and inputs in making this
project. Most of all I thank our school management, for providing us the
facilities and opportunity to do this project.
Lastly, I would like to thanks my classmates who have done this project
along with me. Their support made this project fruitful.
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INTRODUCTION
 An electric generator is a device that converts mechanical energy to
electrical energy.
 The AC Generator's input supply is mechanical energy supplied by
steam turbines, gas turbines and combustion engines. The output is
an alternating electrical power in the form of alternating voltage and
current.
 A generator forces electric current to flow through an external circuit. The
source of mechanical energy may be a reciprocating or turbine steam
engine, water falling through a turbine or waterwheel, an internal
combustion engine, a wind turbine, a hand crank, compressed air, or any
other source of mechanical energy.
 AC generators work on the principle of Faraday's law of electromagnetic
induction. When the armature rotates between the magnet's poles upon an
axis perpendicular to the magnetic field, the flux linkage of the armature
changes continuously.
 Generators provide nearly all of the power for electric power grids.
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THEORY AND WORKING
 The strong magnetic field is produced by a current flow through the
field coil of the rotor.
 The field coil in the rotor receives excitation through the use of slip rings
and brushes.
 Two brushes are spring-held in contact with the slip rings to provide the
continuous connection between the field coil and the external excitation
circuit.
 The armature is contained within the windings of the stator and is
connected to the output.
 Each time the rotor makes one complete revolution, one complete cycle
of AC is developed.
 A generator has many turns of wire wound into the slots of the rotor.
 The magnitude of AC voltage generated by an AC generator
is dependent on the field strength and speed of the rotor.
 Most generators are operated at a constant speed; therefore, the
generated voltage depends on field excitation, or strength.
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COMPONENTS OF AN AC GENERATOR
 Field
 Armature
 Prime mover
 Rotor
 Stator
 Slip rings
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FIELD:
The field in an AC generator consists of coils of conductors within
the generator that receive a voltage from a source (called excitation)
and produce a magnetic flux.
The magnetic flux in the field cuts the armature to produce a voltage. This
voltage is ultimately the output voltage of the AC generator.
ARMATURE:
The armature is the part of an AC generator in which voltage is produced.
This component consists of many coils of wire that are large enough.
PRIME MOVER
The prime mover is the component that is used to drive the AC generator.
The prime mover may be any type of rotating machine, such as a diesel
engine, a steam turbine, or a motor.
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ROTOR
The rotor of an AC generator is the rotating component of the generator, as
shown in Figure 1.
The rotor is driven by the generator’s prime mover, which may be a steam
turbine, gas turbine, or diesel engine. Depending on the type of generator,
this component may be the armature or the field.
The rotor will be the armature if the voltage output is generated there; the
rotor will be the field if the field excitation is applied there.
STATOR
The stator of an AC generator is the part that is stationary.
Like the rotor, this component may be the armature or the field, depending
on the type of generator.
The stator will be the armature if the voltage output is generated there; the
stator will be the field if the field excitation is applied there.
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SLIP RINGS
Slip rings are electrical connections that are used to transfer power to and
from the rotor of an AC generator.
The slip ring consists of a circular conducting material that is connected to
the rotor windings and insulated from the shaft. Brushes ride on the slip
ring as the rotor rotates. The electrical connection to the rotor is made by
connections to the brushes.
Slip rings are used in AC generators because the desired output of the
generator is a sine wave.
In a DC generator, a commutator was used to provide an output whose
current always flowed in the positive direction.
FIGURE-1
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POWER= VOLTAGE X CURRENT
EFFICIENCY
 Efficiency of an AC generator is the ratio of the useful power output to
the total power input.
 Because any mechanical process experiences some losses, no AC
generators can be 100 per cent efficient.
 Efficiency of an AC generator can be calculated using Equation.
 Efficiency = (Output /Input) X 100
OR
Efficiency = (POWER OUT/POWER IN) X 100
EFFICIENCY OF ELECTRIC GENERATOR
EFFICIENCY = POWER OUTPUT * POWER I/P
100
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RESULT
WHEN THE AXLE OF GENERATING MOTOR IS ROTATED, E.M.F. IS
PRODUCEDBY IT.
REASON: CHANGE IN FLUX THROUGH THE WINDING OF MOTOR.
THIS E.M.F. REMAINS IN THE CIRCUIT AS LONG AS AXLE IS ROTATED.
HENCE, FARADAY’S LAW OF ELECTROMAGNETIC INDUCTION IS
VERIFIED.
AS THE SPEED OF ROTOR IS INCREASED, THE VOLTAGE
AND CURRENT PRODUCED BY GENERATOR ALSO GET
INCREASED.
REASON: RATE OF CHANGE OF FLUX INCREASES.
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USES
Aircraft auxiliary power generation, wind generators, high speed gas
turbine generators.
Hybrid electric vehicle (HEV) drive systems, automotive starter generators.
An ac generator, or 'alternator', is used to produce ac voltages for
transmission via the grid system or, locally, as portable generators.
All of our household appliances run on ac current. Ex: Refrigerator, washing
machines, oven, lights, fan etc.
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LOSSES IN AC GENERATOR
1.) Internal Voltage Drop
The load current flows through the armature in all AC generators. The
armature has some amount of resistance and inductive reactance.
The combination of these make up what is known as the internal resistance,
which causes a loss in a n AC generator.
When the load current flows, a voltage drop is developed across the
internal resistance.
This voltage drop subtracts from the output voltage and, therefore,
represents generated voltage and power that is lost and not available to the
load.
2.) HYSTERESIS LOSSES
Hysteresis losses occur when iron cores in an AC generator are subject to
effects from a magnetic field.
The magnetic domains of the cores are held in alignment with the field in
varying numbers, dependent upon field strength.
The magnetic domains rotate, with respect to the domains not held in
alignment, one complete turn during each rotation of the rotor. This
rotation of magnetic domains in the iron causes friction and heat.
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The heat produced by this friction is called magnetic hysteresis loss.
After the heat-treated silicon steel is formed to the desired shape, the
laminations are heated to a dull red and then allowed to cool.
This process, known as annealing, reduces hysteresis losses to a very low
value.
To reduce hysteresis losses, most AC armatures are constructed of heat-
treated silicon steel, which has an inherently low hysteresis loss.
3.) MECHANICAL LOSSES
Rotational or mechanical losses can be caused by bearing friction, brush
friction on the commutator, and air friction (called windage), which is
caused by the air turbulence due to armature rotation.
Careful maintenance can be instrumental in keeping bearing friction to a
minimum.
Clean bearings and proper lubrication are essential to the reduction of
bearing friction.
Brush friction is reduced by ensuring: proper brush seating, proper brush
use, and maintenance of proper brush tension.
A smooth and clean commutator also aids in the reduction of brush friction.
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PRECAUTIONS
 Do all the connection carefully
 Fix all the component on cardboard with strong glue
 Do not take a high voltage LED bulb (1.5V preferred)
 Use only DC motor in making the model
 Before doing any experiment, please consult to
your subject teacher or lab assistance
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BIBLIOGRAPHY
 Wikipedia.com
 Google search engine
 Physics NCERT book
 www.youtube.com/c/knowledgecycle
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