A Rotating Thyristor Excitation System for Hydroelectric Generators

A contemporary approach to the high response excitation system for hydroelectric generators is described. This approach eliminates the conventional mechanical commutator, the main generator field collector rings, and many field power connections and switching devices external to the generating unit. Excitation power generation, and commutation are accomplished by using an AC exciter and thyristor rectifier bridge directly connected to the generator shaft. These elements, in combination with a sophisticated static regulator depending only on electrically derived inputs, provide improved positive damping of electric power system oscillations by proper control of excitation. This system was first applied to three 142,105 KVA, 90 RPM generators now in commercial operation.