Excitation Method : By using DC Generator
This is the old conventional method of exciting the field winding of synchronous generator. In this method, three machines, namely pilot excitor, main excitor, and the main 3-phase alternators are mechanically coupled and driven by the same shaft.
The pilot excitor is a d.c shunt generator feeding the filed winding of main excitor.
The main excitor is a separately excited d.c. generator
The output from the main excitor is given to the field winding of the alternator through brushes and slip rings as shown in figure. This is the old conventional method