What is the Working Principle of AC Generator

An AC generator is an electrical device that produces electricity by converting mechanical energy into electrical energy. It converts mechanical power into electrical power by using electromagnetic induction. This is achieved by two major parts of an AC generator, a rotor (rotating part) and a stator (stationary part).

Parts of AC Generator

The parts of an AC generator are as follows:

1. Armature: The rotating part of the AC generator is called an armature. It includes the commutator and coils that are mounted on the rotor with two opposite polarities.
2. Commutator: The contact where current leaves the brush to enter the armature windings is known as a commutator.
3. Brushes: These are conductors made of carbon, and they maintain contact between the stationary wire, known as a field, and moving parts covered by an armature. The brushes can be replaced if they wear out.
4. Field Windings: These windings are insulated from each other and from the ground, then placed around a core of soft iron or steel lamination. They are usually connected in series for providing direct current or in parallel for alternating current generators. If you want to build an A/C generator, you need to find at least one set of field windings around a core shaft. Their purpose is to create a magnetic field when electricity flows through them so that current can be generated by passing this magnetic field through coils using a rotating magnet inside them (the rotor).

Electricity Generation

Generating electricity is achieved through the process of converting mechanical energy into electrical energy. An AC generator works on the principle of electromagnetic induction and is used to generate electricity in power plants. The basic working principle of an AC generator and its construction are explained in this article.

AC generators are used in power stations to convert the mechanical energy of steam turbines or water flow (hydroelectricity) into electrical energy. 

An AC generator usually consists of two basic parts: rotor and stator. The rotor is the rotating part, while the stator is the stationary part of the AC generator. The rotor contains a field winding, while the stator contains an armature winding.

As the generator spins, it cuts through the magnetic field lines and generates an electric current in the wire. 

Current is defined as the amount of charge flowing past a given point in an electric circuit per unit of time. The magnitude of this current depends on how fast you spin the magnet and how many loops of wire you have around your cylinder.

Types of Generators

Every synchronous generator has some sort of rotary mechanism that connects to a fixed AC/DC power source through two brushes. This means that the rotary mechanism turns at the same rate as the current, which is fed into the generator first through an AC and then via a DC link.

The amount of current that passes through each brush depends on the speed at which they rotate. A common example is a fan which will turn faster if you put more water into it, meaning it’s rotating faster. Therefore, if we put in 100 Amps, or 1000 Watts for instance, then we’d get 1000 Watts of rotation speed out of the machine, which would be almost constant because it will have to push against the friction from moving around inside itself.

Working Principle of an AC Generator

A generator follows the working principle of electromagnetic induction. When a conductor is placed inside a magnetic field, an electric current is induced in the conductor. It moves from the lower potential to higher potential energy using mechanical energy. Thus, it acts as a source of electricity to drive electrical loads and to power devices.

An AC generator produces alternating current, which flows first in a particular direction and then reverses to flow in the opposite direction. Direct current (DC) can be produced by using a rotating magnet, while alternating current (AC) can be produced by using a rotating magnet or AC generator when it is used to create electricity.

The induced emf (electromagnetic field) is given by Faraday’s law of 

electromagnetic induction as

E = Blv

Here,

B is the strength of the magnetic field

l is the length of the moving conductor

V is the angular velocity of rotor with respect to stator

Thus, if we are able to increase either l or B, we can increase E, which means that emf can be increased by increasing the number of turns in the coil or increasing electron flux density. 

Advantages of AC Generators 

The following are the advantages of AC generators:

1. A single or two winding is sufficient for the generation of alternating current power.
2. The armature winding of an alternating current generator can be easily replaced and repaired as compared to the direct current generator.
3. The cost of a rotating converter is less than that of a commutator required in DC generators.
4. It is not necessary to lap or brush slip rings in an AC generator due to which this generator requires very little maintenance and it has high efficiency.
5. An important advantage of an AC generator is that it can supply power to all distances, whereas a DC Generator cannot supply power at such long distances due to losses that occur during transmission and distribution lines, which ultimately reduce its efficiency level. 
6.  AC generators are used exclusively for producing electric power in any large-scale central station, while DC Generators are used only when small amounts of electric power are required, particularly in laboratories and factories etc., where conversion from AC to DC is not feasible or practical.

Disadvantages of AC Generators

The following are the disadvantages of AC generators:

1. An AC generator produces more heat, which can cause fire and burn hazards.
2. A major disadvantage of an AC generator is that it needs a constant fixed strength of power supply.
3. AC generators are not very durable.

Applications of AC Generators

Generator sets are specified by the power they produce, which is measured in kilowatts (kW) or megawatts (MW)

Different types of AC generators are manufactured from small portable electrical generators to large backup generators that can run a whole city block depending on the purpose. Not all of them are suitable for every situation. 

For example, you would probably not pick a noiseless generator for an industrial setting where there is a lot of noise already. 

The portability of the generator is also an important factor, especially if it would be used as an emergency backup source. 

For example, if you need to take your generator with you while camping or driving, then you will want to choose a smaller type of AC generator that is easy to move around.

AC generators are used for:

1. Power generation
2. Motors
3. Battery charging
4. Control circuits
5. High voltage transmission lines
6. Electrical appliances (current transformer)

Welder generators

These are generators used for supplying welding current.

Portable residential generators 

Portable generators are used for home purposes and typically run on gasoline or liquid petroleum. They are used for refrigerators, pumps, furnaces and electrical equipment used in the yard.

Portable construction and industrial generators

These are used in industrial locations and are generally of two types: three-phase diesel and single-phase diesel or gas models.

Portable RV/Recreational Generators

This type of generator is noiseless and runs on gasoline. They are used in home equipment like computers, TV, music player, etc.

Conclusion

A generator works on the principle of electromagnetic induction. When a conductor is placed inside a magnetic field, an electric current is induced in the conductor. An AC generator produces an alternating current, which flows first in a particular direction and then reverses to flow in the opposite direction. Thus, it acts as a source of electricity to drive electrical loads and power devices.

The induced emf (electromagnetic field) is given by  Faraday’s law of electromagnetic induction as

E = Blv

Here, B is the strength of the magnetic fields

l is the length of the moving conductor 

V is the angular velocity of the rotor with respect to the stator.