Behavior of a five-phase surface-mounted permanent magnet motor under magnet demagnetization

The condition monitoring of magnets status in permanent magnet synchronous motors is critical for industrial applications, and then it is receiving more and more attention. Multiphase motor drives are an attractive technology for high power applications. They have many degrees of freedom that can be used for many purposes, such as power density improvement, monitoring, and so on. In this paper, a characterization of rotor faults for five-phase surface-mounted permanent magnet synchronous motors is presented. The considered rotor fault is the demagnetization of the rotor magnet trailing edges, due to large stator currents. The non-invasive detection method is based on a Fourier transform of the back-emf induced in the α-β planes, and exploits the large number of degrees of freedom of a multiphase motor drive. The proposed approach is validated by means of a finite element analysis.