Explain various types of excitation systems for synchronous generators
with diagram if possible
One type is the Brushless excitation system. It has a rotating exciter machine and an automatic voltage regulator to deal with the synchronous generator. Another type is the static excitation system that feeds the rotor directly from the Thyristor Bridge through its brushes. Read more on http://www.abb.com/industries/db0003db004332/c12573e700330587c12570420054aea2.aspx.