Monitoring the rotor winding condition of a H.V. wound rotor induction motor that was driving a ball mill in a cement plant.

The combined application of MCSA and ATCSA revealed the existence of a significant asymmetry in the rotor winding.

Difficulty for localizing the exact source point of the asymmetry, given the greater constructive complexity of the rotor winding in these machines.

Finally, the root cause was localized in the slip ring-brushes system of one of the rotor phases.