Intensity of the native and additional harmonic components in cogging torque due to design parameters of permanent-magnet motors

High performance applications like power steering and robotics require motor drives that produce smooth torque with very low components of cogging torque. To fulfil such demands a variety of techniques are known to reduce native cogging torque components in permanent-magnet motors. However, motor designers usually do not consider that assembly tolerances in mass-production give rise to additional cogging torque components, which are not present in the case of a perfect motor. A finite element method (FEM) and Fast Fourier transformation (FFT) were used to analyse the sensitivity of several motor simulation models with regard to manufacturing assembly tolerances and material imperfections. The ascertainment that PM motor designs with higher values of the sensitivity parameter F are much more responsive to the phenomenon of additional harmonic components in cogging torque than the ones with lower values of parameter F is an important fact for the producers of PM motors, which must be seriously considered in the process of motor design optimization.