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Synchronous generator ( Alternator)

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Topic includes

- Synchronous alternator
- Definition, construction
- Working , application
- Difference between alternator and generator
- About them with hunting
- key points 

Synchronous generator ( Alternator)


Synchronous Generators


It consists of a stator and rotor . The stator provides the armature windings whereas rotor provides the rotating magnetic field.

Definition: 

The synchronous generator or alternator is an electrical machine that converts the mechanical power from a prime mover into an AC electrical power at a particular voltage and frequency. The synchronous motor always runs at a constant speed called synchronous speed.

Essential elements are ..
Prove mover, stator, rotor,  exciter


Construction of Synchronous Generator

The rotor and stator are the rotating and the stationary part of the synchronous generator.

They are the power generating components of the synchronous generator. The rotor has the field pole, and the stator consists the armature conductor. The relative motion between the rotor and the stator induces the voltage between the conductor.


Working Principle of Synchronous Generator

The synchronous generator works on the principle of Faraday laws of electromagnetic induction. The electromagnetic induction states that electromotive force induced in the armature coil if it is rotating in the uniform magnetic field. The EMF will also be generated if the field rotates and the conductor becomes stationary. Thus, the relative motion between the conductor and the field induces the EMF in the conductor. The wave shape of the induces voltage always a sinusoidal curve.

Applications of Synchronous Generator

The three-phase synchronous generators have many advantages in generation, transmission and distribution. The large synchronous generators use in the nuclear, thermal and hydropower system for generating the voltages.

The synchronous generator with 100MVA power rating uses in the generating station. The 500MVA power rating transformer use in the super thermal power stations. The synchronous generators are the primary source of the electrical power. For the heavy power generation, the stator of the synchronous generator design for voltage ratings between 6.6 kV to 33 kV.

Difference Between Alternator & Generator

The major difference between the alternator and the generator is that in alternator the armature is stationary and the field system rotates whereas in the generator armature rotates and field is stationary. The armature of the alternator is mounted on the stationary element called stator and field winding on a rotating element. While the connection of a generator is just the reverse of it.

About generator and alternator

 Alternator and generator both works on the principle of Faraday law of electromagnetic induction. The generator induces both the alternating and direct current and the alternator produces only alternating current. The rotor of the generator is placed inside the stationary magnetic field. The stationary magnetic field is produced by the magnetic poles. The rotor moves inside the magnetic field, intersects the magnetic line of force which induces the current in the wire.

Every half rotation of rotor changes the direction of the current which causes the alternating current. For getting the alternating current, the ends of the circuit is directly connected to the load. But for producing the direct current, the ends of the wire is connected to the commutator. The commutator converts the alternating current into direct current.

Hunting of alternators 


When two alternators are operating in parallel, any instantaneous reduction in the angular velocity of one machine cause..
A change in load division between them.
A circulating current.

The circulating current acts as additional load on one machine and lightens the load on the other. This retards the former and permits the latter to accelerate until the two are once more in the proper relative phase positions where no circulating current flows if the excitations have been equal.
The change to correct phase positions cannot be accomplished without some overshooting on the parts of the rotors, accomplished by a retardation, with a repetition of entire cycle. That is the alternator hunt their actions being exactly equivalent to those of the synchronous motors under similar Conditions .


Key Differences Between Alternator & Generator

An alternator is a machine which converts the mechanical energy from a prime mover into the AC, whereas the generator converters the mechanical energy from the prime mover into an AC or DC.

The alternator induces the AC, whereas the generator causes both the AC and DC power. The generator produces the alternating current which is converted into DC by the help of the commutator.
The alternator has a rotating magnetic field, whereas the generator has a rotating magnetic field for the high voltage generation and low voltage stationary magnetic field is used.
The alternator takes input supply from the stator whereas the generator takes input supply from the rotor.

The armature of an alternator is stationary, and in the case of the generator, it is rotating.
The output EMF of the alternator is variable, and the output voltage of the generator is constant.
The alternator has a wide range of RPM whereas the generator has a narrow range of RPM (rotation per minute).

The alternator does not charge the completely dead battery whereas the generator charges the dead battery.

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