This PPT is a complete description about the Function,principle,Types and working of Excitation System.

1. THE EXCITATION SYSTEM
D. Sai Vinay Guptha 15C11A0256
M.Saketh 15C11A0257
T.BalaRaju 15C11A0209
R.JayaKrishna 15C11A0220
GUIDE:
Mr. T. RAGHU M . Tech( Ph. D)
Associate Professor

2. ABSTRACT
The Excitation System is a key Component in the process
of generating power from alternators and without it
there is no term called generation and it satisfies the
Faraday’s Laws of Electromagnetic Induction, which is a
the working principle of Alternator. Here we made a
detailed study on Excitation System , Various aspect
regarding Selection of Excitation system and its working
principle.
In detail we covered the Purpose, Types, working and
necessity of Excitation System in the prospect of
Alternator and power generation.

3. Contents
oAlternator Excitation System
oFunctions of Excitation System
oTypes of Excitation System
oElements of Excitation System
oDe-Excitation and Protection Of Excitation System

4. Alternator Excitation system
Input to the Alternator:
1. Mechanical Energy to rotate the rotor
2. Excitation current in field winding.
“Excitation System provides the DC electric
current, which is necessary to magnetize
the Generator Rotor. ”
Reason for using DC current
To make the rotor magnet fixed polarity.
Power requirement:
In large alternator : 0.3% to 0.6% of
total power.
Around 250-500V, 10-15 Amp per MW
normal load

5. FUNCTION OF EXCITATION
SYSTEM
 Supply Direct Current to the Field
Winding for Creating Magnetic Field
 Control Voltage & Reactive Power
 Perform Protective Function

6. Types Of Excitation System
Excitation System
AC Excitation Static Excitation
Rotating
Thyristor
Excitation
System
DC Excitation
Brushless
Excitation
System

7. DC EXCITATION SYSTEM
DC EXCITATION
TWO SMALL D.C.GENERATORS ARE USED AS EXCITERS. They are
1.Main Exciter
2.Pilot Exciter
It is the oldest of all. Due to various problem now a days it
is not conventionally used for large alternators

8. Working
The main and the pilot exciters are
Mechanically coupled to the main shaft .
The Pilot Exciter is a DC SHUNT
Generator.
The Output of the Pilot Exciter is fed to
Main Exciter.
 Main Exciter then supplies DC current
to the Field winding of Alternator

9. Drawbacks:
High Maintenance Cost.
It is Difficult to provide Cooling
for DC Excitation System.
It is not Reliable, Since it is too
Conventional.

10. A.C. EXCITATION SYSTEM
It Consists Of A.C. Generator And Thyristor Rectifier
Bridge Directly Connected to the Alternator Shaft or
driven by separate motor.
IT IS OF TWO TYPES
1.BRUSHLESS EXCITATION SYSTEM
Main exciter is self excited
2.ROTATING THYRISTOR EXCITATION SYSTEM
Main exciter is seperately excited

11. This system supplies rotor field current
without using slip ring and carbon brush. This system supplies rotor field current
without using slip ring and carbon brush.
Brushless Excitation System
 This system supplies Excitation
Current without using slip ring’s and carbon brush’s.
This is made possible since the Exciter rotates with Rotor.
 Suitable For Higher Rating Alternator

12. Schematic diagram
AC
DC
DC
AC

13. Working:
Pilot and Main exciter are Mechanically
Coupled to the Main Shaft along with Rectifier
wheel.
Pilot Exciter is a Permanent Magnet Generator,
which has Permanent magnets on the rotor and
Armature Winding on Stator.
Main Exciter has Armature winding on rotor
and Field winding on rotor.
Output of Main Exciter is AC which is then
converted in to DC by the Rectifier Wheel.
Output of Rectifier Wheel is then fed to the
Field Winding of the Alternator.

14. Rotating Thyristor Excitation System
Schematic diagram
DC
DC
AC
DC
AC

15. Working:
Initially AC Exciter’s Field winding is Energized
by a Battery.
AC Exciter is coupled with Main Shaft along
with Alternator Field Rectifier.
Therefore as the Shaft rotates,Exciter and
Rectifier rotates.
Thus due to the Generator action,Exciter
generates AC current and this is then Converted
in to Dc by the Thyristor Bridge.
In order to Trigger the Thyristor bridge and
firing Pulses are provided by the voltage
Regulator.

16. A
Advantage’s of AC Excitation:
 Elimination of brush’s & slip ring’s
 Less maintenance
Fast response time

17. STATIC EXCITATION SYSTEM
There Is No Rotating Part In This Excitation
System. S Loss & Small Size.
Suitable For Medium & High Capacity Alternator
STATIC EXCITATION SYSTEM
There Is No Rotating Part In This Excitation
System. So No Windage Loss & Small Size.
Suitable For Medium & High Capacity
Alternator

18. Circuit Diagram
DC
AC
A
C

19. Advantages of Static Excitation System
Simple in design and provides fast response
characteristics.
As there is no separate rotating type exciter,
the system is free from friction, windage and
commutator loss .
Improved system performance
Extreme Control is Possible, because of
Thyristor bridge.

20. ELEMENTS OF EXCITATION SYSTEM
Figure .2 General Elements of Excitation System
1.Excitor
2.Regulator
3.Terminal Voltage
Transducer and
Load Compensator
4.Power System
Stabilizer
5.Limiters and
Protective Circuits

21. EXCITOR:
It provides dc power
to the generator field
Winding.
Regulator:
It processes and
amplifies input
control signals to a
level and form
appropriate for
control of the exciter

22. Terminal Voltage Transducer:
It senses generator
terminal voltage, rectifies
and filters it to dc quantity
and compares with a
reference.
Load Compensator
Load compensator may be
provided if desired to hold
voltage at a remote point.

23. Power system stabilizer:
It provides additional input
signal to the regulator to damp
power system oscillations.
Limiters and protective circuits:
It ensure that the capability
limits of exciter and generator
are not exceeded.

24. F
DE-EXCITATION
De-excitation
quickly
cuts off power flow
to
the rotor and
consumes
the energy of
magnetic
field stored in
excitation winding.
It operates during Emergency shut down.
DE-Excitation for Alternator safety and safe operation of
Power systems
Fig. DE-Excitation Circuit

25. CONCLUSION
In Conclusion Brushless Excitation is
more Efficient then compared to other
Schemes and Selection of excitation
system depends on various factors
Alternator Power
Alternator Size
Alternator Speed
Maintenance Cost
Operating Environment

26. References
Salah, Mohamed; Bacha, Khmais; Chaari, Abdelkader;
Benbouzid, Mohamed El Hachemi (2014-09). "Brushless
Three-Phase Synchronous Generator Under Rotating Diode
Failure Conditions". IEEE Transactions on Energy
Conversion.29 (3): 594–
601. doi:10.1109/tec.2014.2312173. ISSN 0885-8969
Static Excitation System-Working Principle by
Electricalbaba,an online portal for Electrical concepts
T. W. Eberly, R. C. Schaefer, "Minimum/Maximum
Excitation Limiter Performance Goals for Small
Generation", IEEE PES Panel Session, 1994-July.

27. Thank you