Automatic Voltage Regulators (AVRs) control power in a diode or what?

Automatic Voltage Regulators (AVRs) control power in a diode or what?

• A. Diode bridge
• B. Transformer bridge
• C. Silicon Controlled Rectifier (SCR) bridge
• D. Thyristor bank

Answer: (C)

AVRs regulate the generator’s voltage by controlling the rotor’s excitation current. To do this, they need a rectifier that can vary the DC fed to the field. A fixed diode bridge would give a constant DC output based on the AC input, with no way to adjust it, so it cannot regulate excitation. An SCR bridge, on the other hand, uses silicon-controlled rectifiers whose firing angle is controlled by the AVR. By delaying or advancing when the SCRs conduct during each AC cycle, the AVR changes the average DC sent to the field, thereby increasing or decreasing excitation and stabilizing the terminal voltage. The transformer in the AVR helps with sensing and isolation, but the actual means of regulation is the SCR bridge. A thyristor bank is essentially the same device family, but the conventional description for this function is an SCR bridge.

AVRs regulate the generator’s voltage by controlling the rotor’s excitation current. To do this, they need a rectifier that can vary the DC fed to the field. A fixed diode bridge would give a constant DC output based on the AC input, with no way to adjust it, so it cannot regulate excitation. An SCR bridge, on the other hand, uses silicon-controlled rectifiers whose firing angle is controlled by the AVR. By delaying or advancing when the SCRs conduct during each AC cycle, the AVR changes the average DC sent to the field, thereby increasing or decreasing excitation and stabilizing the terminal voltage. The transformer in the AVR helps with sensing and isolation, but the actual means of regulation is the SCR bridge. A thyristor bank is essentially the same device family, but the conventional description for this function is an SCR bridge.