Effects of nonuniform airgap on the torque characteristics of a switched reluctance motor

In this paper, the results of a two-dimensional (2-D) finite element (FE) analysis carried out on a 8/6 switched reluctance motor for studying the effects of nonuniform airgap on the torque profiles are presented. Results of harmonic analysis of the static torque profiles for various nonuniform airgap conditions are presented. Effects of nonuniform airgap produced by relative eccentricity between the stator and rotor axes, concentricity error in the rotor geometry and motor with elliptical shape of rotor are presented. It is observed that nonuniform airgap results in different static torque profiles for different phases of the motor. With the increase in the relative eccentricity there is increase in the fundamental, 8^th, 10^th, 14^th, and 15^th harmonic torques. It is also observed that for positive concentricity error, motor having elliptical rotor produces more torque, compared to the motor with concentricity error in one half of the rotor.