Imagine you have a smartphone and your smartphone is about to discharged and you are notified that electrical authority are gonna to be power cut for 3 days in your locality due to a major short circuit in the transformer.
After listening this news, how do you feel? May be you become sad. You may feel sad because You can’t able to charge your phone during this three days interval. For today’s generation electricity become a lifeline. Without electricity peoples start feeling bored and they feel that they miss something.
But have you ever thought where does this electricity came from. How does it produces?
Electricity produced by several means, some are listed below –
1). Hydroelectric power plant – by rotating turbines
2). Geological heat
4). Nuclear Power plant
5). DC Generators
6). AC Generators
7). Burning of coal etc.
You will have seen that when electricity goes, peoples starts Generators to fullfill the requirement of electricity. So have you think what are these Generators? How does its work? If you didn’t think about then don’t worry.
Today we are going to talk AC Generator in detail.
WHAT IS AC GENERATOR
AC Generator is a machine, which convert mechanical energy into electrical energy by rotating the coil in magnetic field by some external means. AC Generator is famous electricity producing Machine all over the world. And it is far far better than DC Generator. AC Generators are also called alternators.
PRINCIPLES BEHIND AC GENERATOR
The principles behind the working of AC Generator is – whenever the magnetic flux linked with the coil changes , an EMF is induced in the coil and this induced EMF gives the induced current in the coil.
And the phenomenon by which EMF is induced in the coil by changing the magnetic flux linked to the close circuit is called electromagnetic induction.
Construction of AC Generator is not very complicated, anyone can make AC Generator at home, but it is necessary that the person know some elementry knowledge in electromagnetism.
Here you can see the basic construction of AC Generator.
PARTS OF AC GENERATOR
The main basic parts of AC Generator are –
1) Two permanent magnets
2). Soft iron core
3). Armature coil
4). Slip rings
6). Prime mover
Now let’s talk about their functions in detail –
TWO PERMANENT MAGNETS
This is very very important part of AC Generator. You can’t imagine a AC Generator without this magnets.
This magnets are curved in shape and attached to the wall of stator (A stator is the stationary part of AC Generator in which armature coil rotates). The main purpose of these two permanent magnets are to create magnetic field.
SOFT IRON CORE
Soft iron core is the material which protect and support the coil. The binding of coils is done on this soft iron core. It is done because soft iron core can concentrate the magnetic field as much as 50,000 times more intense than air core. So it is used to increase the strength of the magnetic field.
It is the coil of copper which is bound on the soft iron core. Soft iron core with copper coiling form a armature of cylindrical shape which rotates in between the stator and cut magnetic field lines. This armature coil is also called rotor. Due to magnetic flux change induced EMF and current formed in this coil.
These are hollow rings which are connected to the end point of the armature coil. Slip rings are the point of transmission of induced current through the brushes to the external electrical equipments. It is insulated from inside and fixed on the axle or shaft and it helps in smooth rotation of the armature or rotor.
Brushes are made up of stationary graphite and metal contact (brush). It is connected to the slip rings and used for collecting the induced current from it. When armature rotates in between the stator then slip rings also rotates and when slip rings rotates this brushes rub on its outer curved surface and collect the induced current.
Prime mover is the external machine having diesel or kerosene tank, which is used for rotating the rotor (armature coil) in stator. This prime mover can be a diesel engines or electric motors. When prime mover starts, it creates a very loudly noisy sounds.
WORKING OF AC GENERATOR
Now let’s understand the working of AC Generator, basically the AC Generator works on the principles of Michael Faraday laws of electromagnetic induction.
When armature coil or rotor rotates in the magnetic field by the external machine like diesel engines or electric motors. The magnetic flux linked to the coil changes continuously. This continuously changing magnetic flux in the coil give the induced current or EMF. And this induced current transmitted by the slip rings through the brushes to run the electronic machines.
This induced current is formed due to the changing magnetic flux linked to the coil, if any current which are formed due to changing of magnetic flux then the this type of current is also changing, it means changing magnetic flux induced only changing current and this changing current is called alternating currents. Then we can say that any current which are formed due to the process of electromagnetic induction are alternating currents.
Here you can watch the video for better understanding.
DERIVATION OF INDUCED EMF AND CURRENT
According to the Michael Faraday laws of electromagnetic induction.
Whenever the amount of magnetic flux linked to the circuit changes an EMF is induced in the circuit.
Mathematically , it is given as –
e = -(dΦ/dt) , if N is the number of turns in the coil then-
e = -N(dΦ/dt). …… (1)
Magnetic flux (Φ) is given as –
Φ = B.A = BAcosθ. …….. (2)
Put the value of Φ in equation …(1)
e = -N[d(BAcosθ)/dt]. ………. (3)
θ is the angular displacement of the rotor, and it is given as product of angular velocity and time.
θ = ωt ………. (4)
Put the value of θ in equation …..(3)
e = -N[d(BAcosωt)/dt]
e = -NBA[d(cosωt)/dt]
e = NBAωsinωt
e = e0sinωt where e0 = NBAω , called peak alternating voltage
e = NBAωsinωt is the induced EMF in the armature coil.
I = e/R
I = (NBAω/R)sinωt
I = I0sinωt , where I0 = NBAω/R called peak alternating current.