“SYNCHRONOUS GENERATOR
(ALTERNATOR)”
SYNCHRONOUS GENERATOR
(ALTERNATOR)
Contents: Introduction
What is the Alternators
Single Phase Alternator
Three phase Alternator
Advantages of Alternator
Synchronous Speed
Types of Construction
Use of Alternator
Specification of Alternator
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INTRODUCTION:Alternating current generating system were know in simple
form discovery of the magnetic induction of electric current.
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WHAT IS THE ALTERNATOR:• Synchronous generator or basically case machine and
or usually called alternators rotating machine.
• A Alternator is a machine for converting mechanical
power from a rime mover to A.C. electric power at a
specific voltage and frequency.
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SINGLE PHASE ALTERNATOR:• The two poles of the stator winding are connected to each other so
that the AC voltage are in phase so, they add as the rotor turnes it’s
poles will induce AC voltage in the stator (armature) winding.
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THREE PHASE ALTERNATORA three phase stator can also be connected so that the phase form a
delta connection.
In the delta connection the line voltage are equal to the phase
voltage but the line c/n will be equal to the vector sum of the phase
c/n.
VB
120O
120O
120O
VA
V
O
L
T
A
G
E
A
B
C
VC
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ADVANTAGES OF ALTERNATOR• Most alternator have the rotating field and the
stationary armature.
• This generated voltage may be high as 33 kv.
• The armature windings being station ary are not
subjected do vibration & centrifugal forces.
• The armature of large alternators are forced with
circulating gas or liquids.
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SYNCHRONOUS SPEED• The output frequency of an alternator depends on the number of
poles & the rotational speed.
Ns 
120 f
P
Where N s  synchronous Speed
F  Frequency
P  No.ofPolse
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TYPES OF CONSTRUCTIONThere of two types of construction.
(1) Stator Construction
(2) Rotor Construction two type
1. Salent Pole Rotor
2. Cylindrical rotor
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• Synchronous Generator
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• Synchronous Generator
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USE OF ALTERNATOR• Large Synchronous generators are used to generate
bulk power at thermal hydro & nuclear power station.
• Commonly used synchronous generator as rating of
500 MVA. Used in supper power thermal power
stations.
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Specification of alternator• Normally alternator rating depends on load power
factor which is normally lagging for inductive loads.
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