An interior permanent magnet (IPM) rotary machine comprises a rotor comprising a rotor yoke having bores and a plurality of permanent magnet segments disposed in the bores of the rotor yoke, each permanent magnet segment consisting of a plurality of magnet pieces. The rotor is assembled by inserting the plurality of unbound magnet pieces in each bore for stacking the magnet pieces, and fixedly securing the stacked magnet pieces in the bore.