PRESENTED BY:
AMIT HAZRA

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What is Excitation System ?
The Magnetic field created in the Alternator is known as Excitation System.
It is created using direct current (DC) field.
The DC field obtained from external source is called an Exciter.
Principle
The Alternator is working on the principle of Fleming’s right Hand rule.
As the rule says, “When a motional conductor is placed in a magnetic field (direction of motion is perpendicular to the magnetic field), then an induced emf is produced, which circulate a current in the close loop of the motional conductor.”
Illustration
Its Importance
As far as importance is concerned it is very much essential for alternator.
Without DC excitation field an alternator can’t produce electricity.
HOW AN ALTERNATOR WORK ?
HOW THIS MAGNETIC FIELD PRODUCED ?
It is produced by wound a coil on rotor slots.
Rotor is either cylindrical type or projected pole type.
In cylindrical rotor the windings are placed on rotor slots.
In projected poles the coil is placed on the rotor projectors.
Types of Exciter
WORKING
Normally the Alternators required the excitation field of 200 V DC.
In conventional exciters a Pilot Exciter & a Main Exciter is required.
The pilot exciter is a self-excited DC generator & main exciter is a separately excited DC generator.
Battery backup is also use for excitation purpose.
A thyristor bank is used as the associate of the excitation circuit.
EXCITATION FACTOR
Excitation factor means on which factor excitation depend.
Excitation = f ( Load Pf. )
If the Pf. Load is reactive lagging, then the excitation requirement is more than unity Pf. Load.
If the Pf. Load is leading, then the excitation requirement is less than unity Pf. Load.
ADVANTAGES & DISADVANTAGES
As far as advantages & disadvantages is concerned, there is no advantages or disadvantages of excitation system for an alternator.
It is very much essential for alternator.
Without this the alternator is dead.
So it is just as the “HEART” of alternator.
Maintenance
Regular
Eye site visit.
Fault check.
Vibration & hauling of rotating parts.
Working, controlling & protection circuit continuity.
Periodical
Lubrication of rotating parts.
Cleaning.
Sparking parts should be clean.
Working, controlling & protection circuit healthiness.
Circuit elements maintenance, like relay, breaker, contactor, etc.
Circuit controlling PCB.
CONCLUSION
By this time we know how an Excitation System & an Exciter work for Alternator & how much essential. If it is looking so simple yet it is very much essential for production of electricity by an Alternator.