What is a common cause of overvoltage in a generator?

• A. Excess excitation or sudden loss of load causing an increase in terminal voltage; AVR or governor misadjustment.
• B. Decreased engine speed with automatic load shedding.
• C. Too much fuel causing over-torque.
• D. Logger miscalibration.

Answer: (A)

Overvoltage happens when the generator’s electrical output rises above the rated terminal voltage due to the excitation level being too high for the current load, or because a sudden loss of load removes the voltage drop that kept the voltage in check. When the field current is excessive, the generated emf increases and pushes the terminal voltage higher. If the automatic voltage regulator (AVR) or the governor is misadjusted, they may fail to limit that excitation properly, allowing the voltage to spike even more.

Other scenarios don’t typically cause a true overvoltage: decreasing engine speed with load shedding mainly affects frequency and overall output balance rather than pushing voltage above the set point; too much fuel affects mechanical torque, not the electrical regulation directly; and a miscalibrated logger would distort readings rather than create an actual rise in voltage.