What does a "brown-out" or reduced voltage indicate in a generator under load?

• A. Potential AVR control issue, over/under excitation, or a heavy load causing voltage drop
• B. Generator is brand new
• C. Oil temperature is too low
• D. Ambient humidity is high

Answer: (A)

A brown-out on a generator under load means the output voltage is dropping, and the cause is tied to how the generator regulates voltage or how much load is being asked of it. The automatic voltage regulator (AVR) controls the field current to keep the generated voltage at its set level. If the AVR has a control issue, or the excitation is not providing the right amount of field current (under-excitation, or erratic regulation), the generated EMF can’t hold the terminal voltage steady, so it sags when you apply load. Likewise, if the load is heavier than the machine can sustain at its rated voltage, the voltage will fall due to the generator’s internal impedance and the drop across the windings as more current is drawn. So a brown-out under load most typically signals a regulation/excitation problem or simply insufficient generator capacity for the load.

The other options aren’t about voltage regulation under load: a brand-new generator isn’t inherently leading to a brown-out, oil temperature being too low doesn’t directly cause a voltage sag at the terminals, and ambient humidity isn’t a direct driver of under-voltage in this context.