AC machine performances in faulted operations

Abstract

The detection of anomalous operating conditions of electrical machines at an early stage allows maintenance to be scheduled in order to increase the machine operating life and to reduce the repair cost. The synthesis of the fault conditions is a hard task, therefore the problem is generally examined by means of analysis procedures. To this purpose the analysis of anomalous operations of asynchronous and synchronous machines has been developed by many authors in order to study-the tolerance of the drive to the faults and to find the correlation between faults and anomalous variables. This correlation constitutes the basis of a diagnostic system to detect faults. The presence of an electrical asymmetry in the stator windings of the synchronous and asynchronous machines gives rise to space and time deformations in the air-gap induction and time harmonic components in the stator and rotor currents. The current harmonic content is different for the two machines also because of the different physical structure (the healthy rotor is symmetric in the asynchronous machine and asymmetric in the synchronous one), but the interactions between different space and time harmonics are similar in both cases. In this paper a mathematical model based on the space-vectors theory is used to study AC machines with stator faults. Such an approach allows an easy handling of the mutual interactions between the different harmonic fields. Finally, numerical computations of the harmonic currents and of the performances of two faulted synchronous and asynchronous machines are compared. >