An alternator or AC generator produces an AC supply. In other words, the generator or alternator converts mechanical energy into electrical energy. The rotor rotates at a synchronous speed. Therefore, we call the AC generator a synchronous generator. On the basis of design, the alternators are classified into two categories.
- Salient pole type
- Cylindrical rotor type.
The alternator works on the principle of Faraday’s law of electromagnetic induction. The rotor of the alternator has field winding, and it produces the magnetic flux. When we rotate the rotor by a turbine or a mechanical engine, then the rotating magnetic field produced in the air gap links to the armature coils. The linked flux to the stator or armature winding produces AC voltage.
The armature of the alternator has coils placed 120 degrees electrically apart. The magnitude of the AC voltage produced in the stator or armature of an alternator or synchronous generator depends on the magnetic flux, its frequency, and the number of turns in the stator winding.
Derivation of alternator or AC Generator EMF equation
Let us derive the EMF equation of the alternator, AC generator, or synchronous generator.
The speed of the rotor is ‘N’ RPM. The rotor completes the ‘N’ revolution in 1 minute or 60 seconds. Therefore, the rotor will complete one revolution in N/60 seconds. In one revolution, the total flux linked to the conductor is equal to φP.
According to Faraday’s law of electromagnetic induction,, the emf induced in the conductor is proportional to rate of change of flux.
Please what is the defrent between the speed of the rotor (N) and frequency (F) and please how can we find the flux (Q)