The Demagnetization Harmonics Generation Mechanism in Permanent Magnet Machines With Concentrated Windings

Partial demagnetization is a condition that may occur in Permanent Magnet machines due to overloading or thermal stress. Whenthis happens, the magnetic field locally weakens leading an asymmetry of air-gap field. This will cause harmonics, which be expressed as extra losses and mechanical oscillations. Moreover, since becomes weaker, more current required serve load less efficiency, increased consequently increase temperature, further progression severity until total machine breakdown. Several methods have been proposed literature for online detection demagnetization, however they not related fault manufacturing characteristics machine, play important role on expected harmonic index associated signatures. paper presents first time detailed analytical investigation harmonics stator spectrum case function winding number poles. The results are verified by extensive simulations via finite element method experimental testing.