AC Generator: Overview, Questions, Preparation

An AC generator, also known as an alternator, is a clever device that simply converts mechanical energy into electrical energy (in the form of alternating current) using principles of electromagnetism. The induced EMF in an AC generator can be defined as follows:

 

Mathematical representation –

Magnetic Flux through a coil can be given by :

ϕ=BAcos(ωt)

Where,

ϕ=Magnetic Flux

B = Magnetic Field (SI Unit =tesla)

A = Surface Area (SI Unit = m^2)

Ω = Angular Speed (SI Unit = radians/sec)

T = time (SI Unit = seconds)

Hence, the Induced EMF =

e=−dϕ/dt

e=−d/dt(BAcos(ωt))​

e=BAωsin(ωt)

emax=NBAωsin(ωt) …………… [if the coil has N number of turns]

let us dive into the essential components responsible for the functioning of an AC generator

• Armature/Coil: A rectangle shaped wire having $N$ no. of turns laid on a soft iron core.
• Magnets: Installed to offer continuous magnetic field to the AC generator.
• Slip Rings: Two rotating metallic rings tied at each end of the coil.
• Brushes: Stationary block of carbon bits who maintain the point of contact with the slip rings.
• Shaft: It rotates the coil by converting electric energy into mechanical energy.

Look at the step by step procedure which clearly explains the working of an AC Generator:

• First, the coil starts rotating with the help of an engine or a turbine which uses water, steam etc.
• This rotation produces an electric current in the circuit due to which the magnetic flux keeps on changing continuously.
• The EMF induced changes after every half turn with the help of slip rings.
• Carbon brushes offer the slip rings a point of connection to the circuit, because of which the induced EMF flows into the circuit.
• Due to all these movements, the current's direction keeps on changing continuously which leads to the generation of Alternating Current as per the name suggests.

The table given below summarizes the basic difference between AC and DC generators:

AC Generator	DC Generator
Direction of current changes periodically	Current flows constantly in 1 direction only
Uses slip rings	Uses slip ring commutator
Simple Design	Complex Design
Lower maintenance	Higher maintenance
Used in power plants and alternators	Used in batteries and DC motors

Some of the key applications of AC generators which are used in our day to day lives are mentioned as follows:

• Hydro Power Plants
• Automobile Industry
• Induction Motors
• Electric Generators
• Wind Turbines
• Batteries