Windings monitoring of wound rotor induction machines under fluctuating load conditions

This paper deals with a time-scale method for stator winding asymmetry fault and rotor winding asymmetry fault detections in wound rotor induction machines. An initial study of the rotor asymmetry in induction machines has been based on the energy evaluation of a known low frequency bandwidth with time-scale analysis. It has been shown that both the stator current space vector magnitude and the instantaneous magnitude of stator current are both good candidates to be used as an indicator for this typical fault detection in steady-state condition. In this paper, a new frequency bandwidth associated with the stator winding asymmetry fault in the rotor current signature has been introduced leading to a general form of load independent winding asymmetry detection in wound-rotor induction machines. Furthermore, the previous technique has been improved in order to detect any winding asymmetry in any fluctuating load condition for wound rotor induction machines. The proposed technique has been validated with experimental tests on a 90W wound rotor induction machine.