Reducing cogging torque in interior permanent magnet machines without skewing

This paper proposes a technique to reduce the cogging torque and to improve the magnetic flux waveform in interior permanent magnet machines without skewing the stator teeth or the rotor magnets. In the proposed technique, the reduction of the cogging torque as well as the improvement of the flux waveform is achieved by suitably shaping the geometry of the polar piece. The feasibility of the proposed technique is confirmed either by finite element analysis and by the experimental results obtained with a laboratory prototype.