Other typical problems interesting the dynamical study of the rotors is the balancing. For the balancing procedures we have to distinguish different behaviours. One is for rigid rotors and the other one is for flexible rotors. Rigid rotors are rotors in which the rated speed is sufficiently below the first critical speed of the rotor. Flexible rotors are rotors in which the first critical speed is below the rated speed, so they are operated above its first critical speed.

---