Analytical comparison of synchronous reluctance and surface permanent magnet machines with rotor eccentricity

This paper deals with the unbalanced forces due to the rotor eccentricity. It describes two analytical models suitable for surface permanent magnet machine and synchronous reluctance machine, suitable to predict the flux density with a non-uniform air gap. The radial force on the rotor of the two machines is estimated in case of different rotor eccentricities, at no load and under load conditions. Both uniform and non-uniform eccentricity along the axial length of the machine are considered. For the purpose of comparing the two machine topologies, two 36-slot 4-pole machines are considered. The main geometrical dimensions are the same. Finite element analysis confirms the results achieved by means of both analytical models.