Exam Question

### (a) Explanation of Rotor Excitation
For a synchronous generator (alternator), the rotor must be supplied with direct current (DC) to create a steady magnetic field. This magnetic field, when rotated by the prime mover, induces an alternating electromotive force (EMF) in the stationary stator windings. The process by which this DC field is produced and supplied to the rotor is known as excitation. There are several methods, but they generally fall into two main categories:
**1. Excitation Systems utilising Slip Rings and Brushes (e.g., Static Excitation or DC Exciter):**
* **Concept:** In these systems, the DC current for the rotor field winding is supplied from an external or internal DC source via stationary carbon brushes making contact with rotating slip rings mounted on the rotor shaft.