Excitation Method : By Static Excitation
In this method, the excitation power for the main alternator field is drawn from output terminals of the main 3-4 alternator. For this a 3-phase transformer steps down the alternator voltage to the desired This 3-6 voltage is fed to the 3-6 full converter bridge.
The firing angle of the converter is controlled by means of a regulator which will take the signal from alternator terminals through PT & CTs as shown in figure.
The controlled unit power output is delivered to the field winging of main alternator through brushes and slip rings
For initiating the process of static excitation, first of all field winding is switched on to the battery bank to establish the field current in alternator. The alternator speed is adjusted to rated speed. After the output voltage from alternator has built up sufficiently, the alternator field winding is disconnected from the battery bank and switched on to the thyristor bridge output.