Patent ID: 7504754

Claim:
A rotor for an electric machine, the rotor comprising: a rotor core constructed of magnetically-permeable material, the rotor core including a first cavity having a first curved end portion, and a second cavity having a first curved end portion disposed adjacent the first curved end portion of the first cavity; a third cavity having a first curved end portion disposed adjacent a second curved end portion of the first cavity; wherein from their first curved end portions, the second and third cavities extend away from one another as they extend toward an outer perimeter of the rotor; a fourth cavity disposed between the second cavity and the third cavity, a fifth cavity disposed between the second cavity and the third cavity, the fifth cavity having a first end portion disposed adjacent a first end portion of the fourth cavity; wherein, from their first end portions, the fourth and fifth cavities extend away from one another as they extend toward the outer perimeter of the rotor; and a permanent-magnet cluster, the permanent-magnet cluster including a permanent-magnet layer that substantially magnetically isolates a portion of the rotor core disposed inside the permanent-magnet cluster from portions of the rotor core disposed outside the permanent-magnet cluster, the permanent-magnet layer including a plurality of permanent-magnet pieces disposed in the first cavity, wherein the plurality of permanent-magnet pieces disposed in the first cavity include a first permanent-magnet piece having a perimeter composed of substantially straight surfaces and a second permanent-magnet piece having a curved surface extending substantially contiguous with the first curved end portion of the first cavity, the first permanent-magnet piece being a first type of magnet material and the second permanent-magnet piece being a second type of magnet material, one or more permanent-magnet pieces disposed in the second cavity, one or more permanent-magnet pieces disposed in the third cavity, one or more permanent-magnet pieces disposed in the fourth cavity, and one or more permanent-magnet pieces disposed in the fifth cavity.