Determination of the cogging torque sensitivity of brushless permanent magnet machines due to changes of the material characteristics of ferromagnetic components

This article is about the cogging torque sensitivity of brushless permanent magnet machines. Thereby, the sensitivity calculation of the On-/Off-method is used for determining the change of the cogging torque due to varying material behavior of the ferromagnetic parts of the motor. The results are obtained by using finite element calculations and the sensitivity is separately derived for each finite element. A practical example is examined, where two different machine designs are compared with respect to their nominal cogging torque values and their cogging torque changes for varying material characteristics. From the insights gained by this analysis it can be followed that sensitivity analyses will get more and more important for future machine design optimization.