SEE 3433

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SEE 3433 MESIN ELEKTRIK
SYNCHRONOUS MACHINESBasic principles
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General features
Doubly excited machine
Rotor field winding DC current
Stator Armature winding AC supply
e.g. operated as a generator
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Construction
Salient pole
If
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Construction
Cylindrical
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Salient rotor
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Stator under construction
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Synchronous generator non-salient pole
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Synchronous generators
Field current in rotor produce sinusoidal flux in
airgap
Rotating filed produced when rotor rotates
Rotating field induced 3? voltage in 3 phase
windings on stator
Similar to induction machine, the RMS of induced
voltage per phase is
Ef 4.44 f ? N Kw
Ef known as excitation voltage
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Synchronous generators
Open circuit characteristic (OCC)
Ef depends on

• speed

• Flux per pole hance If

• Exhibit saturation as flux in core saturated

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Synchronous generators
Application in power system
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Synchronous motors
Stator terminals connected to 3? supply
producing rotating magnetic flux
However, rotor wont be able to rotate or start
Due to inertia, rotor cannot catch-up with the
fast rotating field !
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Synchronous motors
Solved by
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Frequency is slowly increased from 0 using power
electronics converter
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Synchronous motors
Solved by
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(Damper winding)
Rotor has squirrel cage construction
At synchronous speed no current induced in the
winding