Amplidyne voltage regulator for turbine generators

THE USE AND DEVELOPMENT of voltage regulators over the past 50 years has produced the modern amplidyne voltage regulator. This regulator includes a voltage-sensitive circuit composed of static elements, such as transformers, reactors, resistors, capacitors, and metallic rectifiers. These are all reliable, conservatively designed components with long life expectancy. The voltage-sensitive circuit controls the voltage introduced by a rotating amplifier, called an amplidyne, into the shunt field circuit of the self-excited exciter for a large turbine generator. The regulator controls exciter voltage, by varying the amplidyne voltage to aid or oppose the flow of current through the exciter shunt field, to maintain the generator terminal voltage essentially constant. A minimum excitation limit circuit is employed to guard against reduction of generator excitation below values which will safely avoid loss of synchronism. This limit circuit responds to generator underexcited reactive current, and it can be adjusted to allow larger values of this current at low kilowatt loads than at high kilowatt loads. The limit circuit is composed of static components similar to those used in the voltage-sensitive circuit.