The document discusses the workings of an AC generator, explaining its components such as the armature, field, rotor, and stator, as well as the principle of electromagnetic induction it operates on. It addresses efficiency factors, losses that occur during operation, and various applications, including household appliances and renewable energy sources. The seminar was submitted by Himanshu Dubey to Mr. Manoj Srivastva under the supervision of Mr. Alok Mishra at Banyan Tree School in Jagdishpur, Amethi.

1. BANYAN TREE SCHOOL
JAGDISHPUR AMETHI
SEMINAR TOPIC
ELECTRIC GENERATOR
SUBMITTED TO
MR. MANOJ SRIVASTVA
(HOD,PHYSICS DEPARTMENT)
UNDER THE SUPERVISION
OF
MR. ALOK MISHRA
SUBMITTED BY
HIMANSHU DUBEY

2. CONTENT
• INTRODUCTION
• PARTS AND FUNCTION
• EFFICIENCY
• RESULT
• WORKING
• LOSSES
• USES

3. INTRODUCTION
• AC generator is a machine that converts mechanical energy into
electrical energy. The AC Generator’s input supply is mechanical
energy supplied by steam turbines, gas turbines and combustion
engines. The output is alternating electrical power in the form of
alternating voltage and current.
• AC generators work on the principle of Faraday’s law of
electromagnetic induction, which states that electromotive force –
EMF or voltage – is generated in a current-carrying conductor that
cuts a uniform magnetic field. This can either be achieved by
rotating a conducting coil in a static magnetic field or rotating the
magnetic field containing the stationary conductor. The preferred
arrangement is to keep the coil stationary because it is easier to
draw induced alternating current from a stationary armature coil.

4. PARTS AND FUNCTION
• 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.

5. .
•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.
•ROTOR
•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.
•STATOR
•Like the rotor, this component may be the armature or the field, depending
on the type of generator.

6. • SLIP RINGS
• In a DC generator, a commutator was used to provide an output whose
current always flowed in the positive direction.
• Slip rings are used in AC generators because the desired output of the
generator is a sine wave.
• 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 electrical connections that are used to transfer power to
and from the rotor of an AC generator.

8. EFFICIENCY
• Expression for Instantaneous E.M.F Produced:
• Let position of the coil at any time t. It make angle q with vertical .
• If w is uniform angular speed of the coil.
• Then q = wtB
be the strength of magnetic field n be the number of turns in the coil and A area of the
coil then magnetic flux with the coil in this position is given by:
f = nBA Cos q = nBA Cos wt.
Differentiate w.r.t. time
= nBA (-Sin wt) w
= -nBA w Sin wt
e = - (-nBA w Sin wt)
maximum value of e.m.f. say E0
e = E0 Sin wt.

9. • 1) Efficiency of an AC generator is the ratio of the useful power output to the
total power input.
• 2) Because any mechanical process experiences some losses, no AC
generators can be 100 percent efficient.
• 3) Efficiency of an AC generator can be calculated using Equation.
• 4) Efficiency =(Output /Input )x 100
•

10. RESULT
• WHEN THE AXLE OF GENERATING MOTOR IS ROTATED, E.M.F. IS PRODUCED BY 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.

11. Working of An Electric Generator
The working of the transformer is explained.
All metals contain a movable substance called "electric charge". Even
uncharged wires are full of charge ! After all, the atoms of the metal are made
half of positive protons and half of negative electrons .Metals are special
because their electrons don't stay connected to the metal atoms, instead
they fly around inside the metal and form a type of electric "liquid”inside the
wires. All wires are full of electric fluid. Modern scientists call this the
"electron sea" or "electron gas." It is not invisible, it actually gives metals their
silvery shine. The electron gas is like a fluid. When a circle of wire surrounds a
magnetic field, and the magnetic field then changes ,a circular "pressure"
called Voltage appears.

12. ARMATURE
This is a basic law of physics, and it is used by all coil/magnet electric
generators. When the circuit is closed and the magnet is moving, charges
in the metal are forced to flow. The charges of the light bulb's filament are
pushed along. When the charges within the copper wire pass into the
thin light bulb filament, their speed greatly increases.

13. LOSSES IN AC GENERATOR
• 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.
• HYSTERESIS LOSSES
• Hysteresis losses occur when iron cores in an AC generator are subject to effects from a
magnetic field.

14. • 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 do mains in the
iron causes friction and heat.
• The heat produced by this friction it is called Hysteresis losses .
• 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.

15. 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.

17. REFERENCES
• Wikipedia
• Slideshow
• Byju’s.com
• Vedantu.com

18. •THANK YOU