| CPC H02K 1/276 (2013.01) [H02K 5/16 (2013.01); H02K 15/03 (2013.01)] | 17 Claims |

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1. A laminate plate for a rotor of an interior permanent magnet (IPM) electric machine, comprising:
a disk-shaped plate defining a plurality of elongated apertures;
wherein each of the elongated apertures has a first side and a second side forming opposed first and second sides, and a first end and a second end forming opposed first and second ends;
wherein the first end is disposed towards an axis of rotation of the disk-shaped plate, and wherein the second end is disposed towards an outer periphery of the disk-shaped plate;
wherein the second end includes a corner portion and a load bearing portion;
wherein the load bearing portion is arranged perpendicular to the first side;
wherein the corner portion has an edge that defines a void area that is recessed into the first side;
wherein the edge includes a convex portion having a first radius R1 arranged in series with a concave portion having a second radius R2, and wherein the first radius R1 is greater than the second radius R2;
wherein the convex portion is connected to the first side;
wherein the concave portion is connected to the load bearing portion of the second end; and
wherein the edge minimizes a stress concentration in the corner portion that is induced by centrifugal force when the rotor is rotating in the IPM electric machine.
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