Reduction of magnet eddy current loss in interior permanent magnet motors with concentrated windings

In this paper, we develop stator and rotor shapes of interior permanent magnet motors with concentrated windings in order to reduce eddy current loss of the magnets at high rotational speeds under field weakening control. First, main factors that cause the magnet eddy current loss in the motor are investigated from results of the three-dimensional finite-element method. The magnet eddy current loss is separated into three components due to their origins and the largest component is specified. With this result, an automatic shape optimization is carried out to determine the stator and rotor shapes, which reduce the magnet eddy current loss without significant decreases in the torque. Finally, the proposed stator and rotor are manufactured in order to confirm the characteristics. The advantages over the conventional motor are clarified.