Which of the following indicates a more severe imbalance in a rotor?

Increasing amplitude of vibration is an indicator of a more severe imbalance in a rotor. As imbalance occurs, the forces acting on the rotor increase, leading to greater vibrations. When the amplitude of these vibrations rises, it signifies that the rotor is experiencing significant dynamic forces that are not being effectively damped or managed. This can be due to a heavy weight distribution on one side of the rotor, which results in enhanced movement and, consequently, larger amplitude fluctuations in the vibration output.

Constant speed would not provide information about imbalance severity; it merely indicates the rotor's operational condition and does not reflect any changes in vibration levels. A decreasing load can sometimes even alleviate the effects of imbalance rather than indicate its severity. Stable frequency indicates that the rotor's operational characteristics are not changing, which does not relate to the severity of any imbalance conditions present. Thus, the increase in vibration amplitude is the most direct indicator of worsening imbalance conditions.