Alternating Current (AC) Generator

Working Principle

AC generator working principle is the concept of Faraday’s Law of Electromagnetic Induction. The movement of a conductor in a consistent electromagnetic field changes the magnetic flux linked with the coil, therefore generating an emf. If the load is connected, an alternating current starts flowing because of the induced emf. This is just how an AC Generator functions.

Parts of an AC Generator

An AC generator includes two sides i.e., is the north pole and south pole of a magnet to ensure that we have a uniform magnetic field. There is likewise a coil that is rectangular in shape that is the armature. These coils are linked to the slip rings and also affixed to them are carbon brushes.

The slip rings are made from metal and also are protected from each other. The brushes are carbon brushes and one end of each brush attaches to the ring and the other connects to the circuit. The rectangle-shaped coils rotate about an axis that is vertical to the magnetic field. There is also a shaft which revolves quickly.

Working of Alternating Current Generator

The coil is rotated in the magnetic field to generate a strong magnetic field. As the coil on one side moves up with the electromagnetic field, an emf is induced in one direction. As the turning of the coil continues and also this side of a coil relocates down and also an additional side of the coil moves up, an emf is generated in the reverse direction.

Fleming’s right-hand rule is utilized to figure out the direction of the caused emf. This process repeats for every cycle and also the emf generated is of the rotating kind.

Emf generated in an AC generator

• A – When the coil goes to 0 degrees, the coil moves alongside the direction of the electromagnetic field and also, therefore, generates no emf.
• B – When the coil goes to 90 levels, the coil moves at 90 ˚ to the electromagnetic field and thus induces maximum emf.
• C – When the coil goes to 180 degrees, the coil once again moves alongside the magnetic field and hence induces no emf.
• D – When the coil is at 270 degrees, the coil once more moves at 90 ˚ to the magnetic field as well as thus induces optimal emf. Right here, the generated emf is contrary to that of B.
• A – When the coil is at 360 degrees, the coil has actually completed one turn and also it relocates parallel to the electromagnetic field and also induces zero emf.

If the coil of N turn and also are A is turned at v revolutions per second in a consistent electromagnetic field B, after that the motional emf induced is ε = NωAB sin ωt, where we think that at time t = 0 s, the coil is perpendicular to the field. The direction of the induced emf is given by Fleming’s right-hand rule or Lenz’s law.

Calculation of Induced Emf

Let suppose the coil is rotating in an anti-clockwise direction with uniform angular velocity ω. By taking its top view let θ is the angle between magnetic field B and velocity v of the vertical side of AB loop.

So, the motional emf induced in AB is

ε_{ab =} v BL sin θ

motional emf inside CD

ε_{cd =} v BL sin θ

Motional emf induced in sides bc and da is zero because the force acting on the charges inside bc and da is not along the wire.

                                    ε_bc =ε_da = 0

Net motional emf

As both emfs in the side ab and bc drive current in the same direction around the loop, so the net emf in the loop is:

                                                            ε = ε_ab +ε_cd

                                                                        ε = v BL sin θ + v BL sin θ

                                                            ε = 2v BL sin θ

If there are number of turns in the coil is N then,

                                                            ε = 2N v BL sin θ

As the relationship between linear speed v and angular speedω is

v = r ω

here r is the distance of vertical wires from the center of the coil

                                    ε = 2N (r ω) BL sin θ

                                    ε = Nω(2rL) B sin θ

Now the area of a coil is A = 2r L and θ = ωt

                                                ε = NωAB sin ωt    

Types of AC Generators

Induction Generators:

Likewise referred to as Asynchronous Generators, these are a kind of Alternating current generators that operates on the exact same principle as that of a typical generator. The working principle is simply similar to a transformer the distinction is a transformer is a fixed device whereas the Induction generator is a revolving device.

The speed of the Induction generator is less than the simultaneous speed so, it is labeled as an asynchronous generator. These are generally utilized in little machines like mixer mills, and also as large devices utilized in Industries.

Synchronous Generator:

This is additionally a kind of Alternating Current Generator that revolves at a simultaneous rate. These are typically made use of in nuclear power plants because of their high efficiency. This generator also works with the principle of Faradays’ law of electromagnetic induction. An Emf is induced as a result of the movement of the conductor inside the magnetic flux.

Advantages and Applications

• Simple and easy to maintain
• Comparatively small in size
• Used in power generation in industries
• Transmission and distribution of electric energy in power plants

MCQs