Unbalance causes a moment which gives the rotor a wobbling movement characteristic of vibration of rotating structures.
[5] The measurement of existing vibration and calculation of the change of mass required is typically carried out using some form of balancing machine.
Unfortunately, it is the theoretical value assuming the rotor was spinning in free space so it does not relate to actual operating conditions.
where ω = angular velocity (radians per second) eper = permissible residual specific unbalance This constant is quality grade G. Balance Grades are used to specify the allowable residual imbalance for rotating machinery.
A rotor balanced to G2.5 will vibrate at 2.5 mm/s at operating speed if rotating in a suspended state with no external influences.