How to monitor the rotor condition and identify the rotor fault?

In general it is not necessary for damage diagnosis of the rotor, but for better interpretation of the FFT or spectrum of the rotor vibration signal, it is necessary to know which fault can excite which frequency. Therefore by looking at to the related papers in literature by which the model has been used for understanding the exact behavior of the rotor vibration when there is a fault, you can use just practical spectrum of the vibration signal for finding the rotor fault.

The rotor will be safe if it will be monitored always with a healthy bearings and acceptable air gap limits, as well faults will be prevented from it and especially you should always ensure that your terminals are tight and at the right torque and no loose connections.