Torque harmonic compensation in a synchronous reluctance motor

The torque behavior of a synchronous reluctance motor [including the permanent magnet (PM) assisted configuration] is deeply analyzed. An analytical model is developed, showing the dependence of the torque ripple on the rotor geometry. The results of this model allow to individuate the position of the flux-barrier ends so as to minimize the torque ripple. In addition, the proposed strategy to minimize the ripple is not only based on a suitable choice of the flux-barrier ends, but this choice is combined with the adoption of a rotor formed by two different laminations. This strategy allows an optimal compensation of the torque harmonics so that a smooth torque is achieved. Some motor prototypes have been manufactured and tested in a suitable testing bench. The torque versus position characteristics have been measured at very low speed, to avoid a reduction of the high-order torque harmonics. The experimental results confirm the effectiveness of the proposed strategy. Index Terms--Low torque ripple, permanent magnet (PM) assisted synchronous reluctance machine, synchronous reluctance machine.