Exam Question

(a) In an AC generator, excitation of the rotor is a process that involves creating a magnetic field in the rotor, leading to the generation of alternating current in the stator windings. Excitation is necessary to induce the flow of electric current within the generator.
There are typically two main types of excitation systems in AC generators: brushless excitation systems and brush excitation systems.
Brushless Excitation System: In brushless excitation systems, the rotor is equipped with a rotating field winding. The excitation process involves the following steps:
AC Voltage Generation: The stator windings of the generator produce an initial AC voltage. This voltage is often derived from an auxiliary AC power source or from the generator itself during initial startup.