Magnetic field calculation in permanent magnet motors with rotor eccentricity: without slotting effect

An analytical technique for predicting the instantaneous magnetic field distribution in the air gap region of permanent magnet motors with rotor eccentricity is developed. The governing equations and associated boundary conditions are formulated and solved by a perturbation method. The predicted solutions are verified by the results of a corresponding finite element analysis. The results show the effectiveness of using the perturbation method for this eccentric field calculation. According to this study, the additional flux density due to rotor eccentricity is proportional to the amount of the eccentricity in a small range and has a quite different distribution from the normal flux density without rotor eccentricity. Accordingly, rotor eccentricity may cause undesirable effects on brushless permanent magnet motors