**5. Patterns of failures**

A fault in any part of the machine is a decrease in this part performance when compared with the minimum requirements specified. Thus the fault results from natural wear, project errors, incorrect installation, poor use or a combination of all of them. If the fault is not identified in time and increases, failure may ensue (Thorsen & Dalva, 1999). Therefore, failure is the reason why the machine breaks down. This way, one tries to identify the fault before it becomes a failure, even when it is incipient.

Predictive Maintenance by Electrical Signature Analysis to Induction Motors 507

**Figure 12.** Static and Dynamic Eccentricities patterns

**Figure 13.** Rotational frequency pattern

**Figure 14.** Stator winding failure modes

Most induction motor stator failures are related to the windings. The occurrence of failures in the stator core is less frequent. In spite of being rare, this last problem can cause

considerable damages to the machine (Borges da Silva et al., 2009).

**5.2. Stator failure patterns** 
