Contents

• Introduction• Principle of operation• What is parallel operation ?• Why required connect in parallel ?• Necessary Conditions• Syncronization method • procedure• Advantages • Summery

Alternator An alternator is an electrical generator that converts mechanical energy to

electrical energy in the form of alternating current.

[1] For reasons of cost and simplicity, most alternators use a rotating magnetic field with a stationary armature.

[2] Occasionally, a linear alternator or a rotating armature with a stationary magnetic field is used. In principle, any AC electrical generator can be called an alternator, but usually the term refers to small rotating machines driven by automotive and other internal combustion engines. An alternator that uses a permanent magnet for its magnetic field is called a magneto. Alternators in power stations driven by steam turbines are called turbo-alternators.

Principle of operation A conductor moving relative to a magnetic field develops an electromotive force (EMF)

in it, (Faraday's Law). This emf reverses its polarity when it moves under magnetic poles of opposite polarity. Typically, a rotating magnet, called the rotor turns within a stationary set of conductors wound in coils on an iron core, called the stator. The field cuts across the conductors, generating an induced EMF (electromotive force), as the mechanical input causes the rotor to turn.

The rotating magnetic field induces an AC voltage in the stator windings. Since the currents in the stator windings vary in step with the position of the rotor, an alternator is a synchronous generator.

The operation of connecting an alternator in parallel with another alternator or with common bus-bars is known as synchronizing. Generally, alternators are used in a power system where they are parallel with many other alternators. It means that the alternator is connected to a live system of constant and constant frequency.

WHAT IS PARALLEL OPERATION ?

Often the electrical system to which the alternator is connected, has already so many alternators and loads connected to it that no matter what power is delivered by the incoming alternator, the voltage and frequency of the system remain the same. In that case, the alternator is said to be connected to infinite bus-bars.

Why this system required.

uninterrupted continuous power supply. For fulfill the load requirement. Provide increase the overall efficiency. For reduce per unit generating cost.

PARALLEL OPERATION OF ALTERNATORS

Alternators are connected in parallel to

(1) increase the output capacity of a system beyond that of a single unit,

(2) serve as additional reserve power for expected demands, or (3) permit shutting down one machine and cutting in a standby

machine without interrupting power distribution. (4) When alternators are of sufficient size, and are operating at

different frequencies and terminal voltages, severe damage may result if they are suddenly connected to each other through a common bus.

(5) To avoid this, the machines must be synchronized as closely as possible before connecting them together. This may be accomplished by connecting one generator to the bus (referred to as bus generator), and then synchronizing the other(incoming generator) to it before closing the incoming generator’s main power contactor. The generators are synchronized when the following conditions are set:

NESESSARY CONDITION FOR PARALLEL OPERATION OF ALTERNATORS

Before connecting an alternator into grid, following conditions must be satisfied:

1. Equal voltage: The terminal voltage of incoming alternator must be equal to the bus-bar voltage.

2. Similar frequency: The frequency of generated voltage must be equal to the frequency of the bus-bar voltage.

3. Phase sequence: The phase sequence of the three phases of alternator must be similar to that of the grid or bus-bars.

4. Phase angle: The phase angle between the generated voltage and the voltage of grid must be zero.

To satisfy the conditions of equal frequency and identical phases, one of the following two methods can be used:

(i) Synchronization using incandescent lamp

(ii) Synchronization using synchroscope.

Syncronization method

SynchronizationOf Alternator Using Incandescent Lamp

 

Synchronization Of Alternator Using Synchroscope

TWO BRIGHT ONE DARK LAMP METHOD:-

VECTOR DIGRAM:-

procedure of alternator connect in parallel

In the operation there are two alternators connected in parallel.

Bus-bar, (to which a number of alternators are connected.)

The process of connecting an alternator in parallel with another alternator or with common bus-bar is called synchronizing.

The system is establish on the base of requirement of load.

In the process of A.C generator mechanical input is provided to rotate the alternator.

Advantages of Parallel Operation of Alternators:

Continuity of Supply and Maintenance:

Efficiency:

It is easier for maintenance when smaller individual generating units are used, since we can schedule the maintenance of each unit one after the other without affecting the continuity of power generation.

You might have seen the efficiency versus load current curve of the generator, according to that the generator unit must run on full load, since efficiency is maximum when the load is 100%.

Expansion Plans

Suppose the current capacity of the power plant is 500 MW, if after 2 year it plans to expand the capacity to 700 MW then it will be much costlier to replace the whole single generator setup and to buy a bigger unit.

Size of Alternators:

More the rating of the generator, huge is the size of the setup. It is very difficult to manage a single large alternator which may range around 1000 MVA or more.

Application of alternator

SummeryIn the parallel operation of alternators, we have learn about

the hole system. And know the main advantages by this and how we do in our electricity system, here we also studied about the process of parallel operation and the applications of these type of system.

Behind of everything there are one term that is WHY and here we know about this and how we utilize it in our system and what are the main work for complete the task of electricity.

References

www.google.com www.wikipedia.com www.electrical4u.com www.electricaleasy.com www.youtube.com

Any Question…..?

THANK YOU