What is the significance of synchronous speed in synchronous generators?
The synchronous speed refers to the constant rotational speed at which the frequency of the output voltage remains same. It is important to maintain the rotor speed precisely at synchronous speed for proper synchronization.
What is the effect of varying the field current in a synchronous generator?
Increasing the field current strengthens the main magnetic field, which increases the induced emf. However, beyond a point further increase in field current leads to saturation and then emf starts decreasing. This behavior is represented by the V-curve of a synchronous generator.
What are the advantages of using permanent magnet synchronous generators over normal synchronous generators?
Permanent magnet synchronous generators have advantages like higher efficiency, reduced size, absence of separate DC excitation system and elimination of copper losses in field windings. However, the output voltage cannot be controlled.
What is the emf equation of a synchronous generator?
The emf equation of a synchronous generator is E = Kφω, where E is the induced emf, K is a constant, φ is the magnetic flux through one turn of the coil, and ω is the angular velocity.
Why are cylindrical rotors preferred over salient pole rotors for large generators?
Cylindrical rotors are preferred for large generators as they can withstand higher mechanical stresses due to uniform air-gap flux distribution compared to discrete poles in salient pole rotors. They are also easier to manufacture for higher power ratings.