Patent ID: 6946766

Claim:
An interior permanent magnet machine comprising: a rotor stack defining adjacent magnet retention slots; a plurality of permanent magnets positioned within the interior of the rotor, wherein a radial thickness of the rotor that is above a given magnet retention slot transitions from a first radial thickness to a bridge region having a second radial thickness that is less than the first radial thickness, the first and second radial thicknesses being measured along imaginary adii from an outer edge of the rotor to a center of the rotor, the bridge region being positioned between the two magnet retention slots, wherein such transition occurs within an area falling within an angular expanse that is between approximately 148 electrical degrees and 150 electrical degrees from an imaginary radius extending through the midpoint of the magnet retention slot, where the angle in electrical degrees is equal to the angle in mechanical degrees multiplied by the total number of permanent magnets; and an area of low magnetic permeability positioned at a point radially below the bridge region between the ends of the adjacent permanent magnets.