Validation of Rotor Magnets Demagnetization Detection in Six-Phase Surface-Mounted AC Permanent Magnet Synchronous Motors

The interest in multiphase machines is generally motivated by their intrinsic active phase redundancy, leading to a greater number of degrees of freedom compared to three-phase machines. Among multiphase machines, permanent magnet synchronous motors is an attractive alternative to induction machines, for a large variety of applications, principally because of their reliability and higher dynamic performances. In this context, rotor magnet anomalies diagnosis is crucial and is receiving an increasing attention to ensure the required application performances. In this paper, a newly developed technique for the detection of rotor magnet demagnetization, due to stator over currents in six-phase surface-mounted permanent magnet synchronous motors, is presented. The proposed approach is mainly based on the spectral analysis of the back-emf, leading to an effective detection of rotor magnet demagnetization. The performance of the proposed non-invasive approach has been, firstly, validated by means of two dimensional finite element analysis, and then by experimental results, showing a very good agreement.