Study of cogging torque in permanent magnet machines

Cogging torque is produced in a permanent magnet machine by the magnetic at traction between the rotor-mounted permanent magnets and the stator. It is an undesired effect that contributes to the machines' output ripple, vibrat ion, and noise. This paper analyzes various cogging torque minimization tec hniques as applied to a permanent magnet machine used in an electric power steering system. A 6-pole, 18 slot, surface-mounted, rare earth type, brush less permanent magnet machine is analyzed. The resultant cogging torque val ues are computed using a two-dimensional finite element analysis package.