Which statement best describes the primary function of the Automatic Voltage Regulator (AVR) in a synchronous generator?

Which statement best describes the primary function of the Automatic Voltage Regulator (AVR) in a synchronous generator?

• A. The AVR senses terminal voltage and controls the excitation system to regulate terminal voltage.
• B. The AVR measures frequency and adjusts the governor input to maintain speed.
• C. The AVR controls the mechanical input to the turbine.
• D. The AVR monitors line impedance to protect the generator.

Answer: (A)

The main idea here is how a generator keeps its output voltage steady. The Automatic Voltage Regulator does this by sensing the terminal voltage and adjusting the excitation of the generator’s rotor. It compares the actual voltage at the terminals to a set reference and, if the voltage drifts due to load changes or other conditions, it changes the field current. More excitation strengthens the magnetic field and raises the generated voltage; less excitation lowers it. This creates a feedback loop that maintains the terminal voltage at the desired level, which is essential for stable operation of the electrical system. Frequency control, on the other hand, is handled by the turbine governor, which adjusts mechanical input to the turbine to keep speed (and thus grid frequency) close to the target. The AVR doesn’t regulate turbine input or frequency. Protection-related actions, like monitoring line impedance to guard against faults, are done by protective relays, not the AVR.

The main idea here is how a generator keeps its output voltage steady. The Automatic Voltage Regulator does this by sensing the terminal voltage and adjusting the excitation of the generator’s rotor. It compares the actual voltage at the terminals to a set reference and, if the voltage drifts due to load changes or other conditions, it changes the field current. More excitation strengthens the magnetic field and raises the generated voltage; less excitation lowers it. This creates a feedback loop that maintains the terminal voltage at the desired level, which is essential for stable operation of the electrical system.

Frequency control, on the other hand, is handled by the turbine governor, which adjusts mechanical input to the turbine to keep speed (and thus grid frequency) close to the target. The AVR doesn’t regulate turbine input or frequency. Protection-related actions, like monitoring line impedance to guard against faults, are done by protective relays, not the AVR.