An analytical evaluation of rotor eccentricity effects on synchronous drives with surface mounted permanent magnet brushless motors

The paper deals with static eccentricity in synchronous PM motors with surface mounted magnets. Simple analytical expressions are proposed for the evaluation of the length of stator and rotor magnetic field lines in the air-gap as a function of rotor eccentricity. By means of some appropriate considerations, the analytical expressions of the flux-density distribution of armature and rotor across the air-gap is yield. They allow us to point out a mathematical model of the machine in terms of concentrated parameters. The model is then used in order to evaluate the variations that can occur in the armature currents or in some characteristic parameters of the machine in steady-state operating conditions, with respect to the case without eccentricity.