Sizing rectifier excitation systems
Synchronous machines - Excitement

The power source of the excitation systems must be able to withstand the stresses associated with voltage regulation operation and the abnormal regimes to which the synchronous machine may be subjected. Because of their low thermal inertia, rectifiers must be designed for the amplitude and duration of these stresses.

• In terms of voltage withstand, ceiling operation does not represent the most severe stress. The main disturbances giving rise to overvoltage are :

  • out-of-sync operation due to reduced excitation current;

  • false coupling ;

  • and, in the case of self-excitation :

  • power surges from the network ;

  • rapid de-excitation.

  For all these disturbances, the maximum overvoltage is of the order of 5 times the nominal excitation voltage at load, and rectifiers are...