Time harmonic investigation of flux density in the stator and rotor frame oriented to diagnostics of cage induction machines

Condition monitoring of electric machines is increasing in importance: the continuous assessment of the machine performance allows to schedule appropriately maintenance, so increasing machine operating life and reducing repair cost. The monitoring system must give an early indication of the onset of possible malfunctions. Therefore a great amount of study is in progress to associate an unambiguous symptom to the corresponding malfunction, so to obtain a univocal correspondence cause-effect. Among the different diagnostic techniques, the spectral components present in the machine variables allow the identification of several fault conditions. Here, the authors describe how the current spectrum and the flux density spectrum are widely considered in the diagnostic systems applied to induction machines