A New nalysis Method Based on Lumped Magnetic Circuit Model for Surface Permanent-Magnet Machines with Step-Skewed Rotor

This study proposes a new analysis method based on lumped magnetic-circuit for surface permanent-magnet machine (SPM) with overhang and step-skewed rotor. In SPM machine, the step-skew lowers the torque pulsation and makes the electromotive force sinusoidal, and the overhang structure increases the torque density. A time-consuming three dimensional (3-D) finite element method (FEM) is required to analyze axial components such as step-skew leakage flux and overhang flux. To deal with this problem, a new equivalent lumped magnetic-circuit model for each rotor step considering the axial leakage flux between the steps and the linkage flux by the overhang is introduced. The validity of the proposed method is verified by comparing a two-dimensional and 3-D FEM of skewed, non-skewed, overhang, and non-overhang SPMs.