THIS IS ABOUT THE DERIVATION OF THE EMF EQUATION IN A AC GENERATOR AND THE OPERATIO PRINCIPLE

1. ELECTRICAL DC MACHINES
RAGHU ENGINEERING COLLEGE
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PRESENTED BY
P.SANJAY KUMAR

2. INDEX
S.r no Topic Name
1 INTRODUCTION
2 PRINCIPLE OF OPERATION
3 CONSTRUCTION
4 WORKING
5 CLASSIFICATION
6 APPLICATIONS
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3. INTRODUCTION
• The Device which Converts the Mechanical Energy into
Electrical Energy is called Generator.
• There are Two types of Generators
1. D.C Generator:- The Generator which converts the
Mechanical Energy into D.C Form of Electrical Energy is called
D.C Generator.
2. A.C Generator:- The Generator which converts the
Mechanical Energy into A.C Form of Electrical Energy is called
A.C Generator.
• Both of the Generator Works on the Principle of Faraday’s
Law of Electromagnetic Induction.
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4. PRINCIPLE OF OPERATION
• In 1831, Michael Faraday, an English physicist gave
one of the most basic laws of electromagnetism
called Faraday's law of electromagnetic induction.
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5. CONSTRUCTION
• Important Parts of D.C Generator
1. YOKE
2. POLES
3. FIELD WINDING
4. ARMATURE
5. COMMUTATOR,BRUSHES and GEAR
6. BEARINGS5

6. YOKE
• Yoke is also called as frame. It provides
protection to the rotating and other
parts of the machine from moisture, dust
etc.
• Yoke is an iron body which provides the
path for flux
• It provides the mechanical support for
the poles.
• Materials used for yoke are cast iron,
silicon steel, cast steel, rolled steel etc.
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7. POLE
• Pole produce the magnetic flux when the field
winding is excited.
• Materials used for Pole is cast steel or cast iron.
• Pole is a Part on Which Field
Winding is Wound Over.
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8. FIELD WINDING
• The field winding is also called as exciting winding.
• Current is passed through the field
winding in a specific direction ,to magnetize the pole.
• The metal is used for the field
conductor is copper.
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9. ARMATURE CORE
• All these slots are parallel to the
shaft axis.
•Armature conductor are placed in
these slots.
•Armature core provides a low
reluctance path to the flux produced
by the field winding.
•Cast steel or cast iron are used for
the armature core.
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10. COMMUTATOR
• The commutator converts the alternating emf generated
internally in a D.C. voltage .
• It collects the current from
the armature conductors
and passes it to the external
load via brush.
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11. ROTOR
• The Rotor is the moving part of a
D.C. generator.
• The rotor rotates because the
wires and magnetic field of the
motor are arranged so that a
torque is developed about the
rotor’s axis.
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12. WORKING of DC GENERATOR
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13. • The Dc Generator Converts Mechanical Energy into Electrical
Energy.
• In this DC Generator the Single Turn Alternator is used.
• The Coil can Rotate in Clockwise or Anticlockwise
Direction.
• The Commutator Brush is Connected to the Coil.
• Commutator is Divided into Two Parts A and B.
• The Coil is Suspended between the Field Poles.
• The Coil is Given the Mechanical Energy which Results in
the Rotation of it.
• As the Commutator Segments A&B is Connected with
Conducting Coil ab and cd Respectively they Rotate
Together.
• Due to Which the Flux is Produced Resulting in the
Generation of Electric Current.
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14. • As the Commutator has the Property of Converting
the Bidirectional Emf(AC) into Unidirectional Emf
(DC) .
• The DC Current is Generated by the DC Generator.
• Which can Directly Used by Connecting the Output
across the Load or it Can be stored inatteries and Can
be used Later on.
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15. Derivation for Induced EMF of One Armature
Conductor
For one revolution of the conductor,Let,
Φ = Flux produced by each pole in weber
(Wb)
P = number of poles in the DC generator.
therefore,
Total flux produced by all the poles
Time taken to complete one revolution
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16. Now, according to Faraday’s law of induction, the induced emf of
the armature conductor is denoted by “e” which is equal to rate of
cutting the flux.
DERIVATION FOR INDUCED EMF FOR DC GENERATOR
Induced emf of DC generator
E = emf of one conductor × number of conductor connected
in series.
Induced emf of DC generator is
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17. Simple wave wound generator
Numbers of parallel paths are only 2 = A
Induced emf for wave type of winding generator
is
Here, number of parallel paths is equal to number of conductors in one
path
P = A
Induced emf for lap-wound generator is
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19. CLASSIFICATION
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20. APPLICATIONS
• Shunt generator:
Lighting loads
Battery charging
• Series generator:
For the arc lamps
As constant current generator
As boosters on D.C. generator
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21. • Separately Exicted generator:
The application of these generator have limitations , because
they need a separate excitation for the field winding.
Some of the application are electro-refining of materials or
electroplating
• Cumulative compound generator:
Used for domestic lighting
For energy transmission over a long distance.
• Differential compound generator:
• Its important application is electric arc welding
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