Post-demagnetization characteristics of permanent magnet synchronous machines

This work investigates post-demagnetization characteristics of permanent magnet synchronous machines (PMSMs). A combination of closed-form analysis using a magnetic equivalent circuit model and finite element (FE) analysis is used to provide physical insights into the flux paths associated with demagnetizing electromotive force (MMF). Post-demagnetization behavior in several types of PMSMs is studied to better understand post-fault PM machine performance and the key characteristics that can be used to monitor demagnetization faults. Topics include the key role of magnet flux leakage paths in interior PM machines for attenuating the negative impact of demagnetizing stator MMF, and the particular vulnerability of PM machines with fractional-slot concentrated windings to progressive accumulated degradation following exposure to multiple demagnetization events. FE analysis is used to build confidence in the demagnetization predictions of the developed model and to provide more insights that are difficult to obtain using the analytical model.