Prediction of cogging torque using the flux-MMF diagram technique

An improved approach to predicting cogging torque in permanent magnet motors using the flux-MMF diagram technique is presented and validated. A brief review of cogging torque calculation and minimization techniques is included. It is shown that the flux-MMF diagram can be constructed for any one pole of a permanent magnet machine using the demagnetization characteristic of the permanent magnet; then by applying the principle of virtual work, cogging torque can be predicted. It is also shown that the flux-MMF diagram technique is a truly universal technique of cogging torque prediction and gives greater insight into many of the methods used for cogging torque minimization.