Induction motors generate multitple vibration frequencies that are inherent to their design and application. As we will be seen in this chapter, the magnitude of the vibration at a given frequency depends on the magnetic field generated in the motor and the dynamic response of each machine component. Both the magnetic field and the dynamic response may vary due to changes in the machine.

It is therefore good practice to monitor the vibration spectrum of critical machines in order to identify possible changes that could be indicative of the occurrence of problems caused by wear, looseness or other causes of mechanical deterioration.