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In this paper, we develop stator and rotor shapes of interior permanent-magnet motors with concentrated windings in order to reduce the eddy-current loss of the magnets at high rotational speeds under field-weakening control. First, the main factors that cause the magnet eddy-current loss in the motor are investigated from the results of the 3-D 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.