Patent ID: 8193666

Claim:
An interior permanent magnet brushless direct current (BLDC) motor comprising: a stator having a plurality of slots; and a rotor positioned in the stator, configured to rotate with respect to the stator, and having a rotor core, a plurality of permanent magnets positioned in the rotor core, a plurality of vent holes positioned between a center of the rotor core and the permanent magnets, and a plurality of coupling holes positioned between the permanent magnets and a periphery of the rotor core, wherein the rotor has four poles, wherein the plurality of permanent magnets are four in number, wherein each permanent magnet has a shape of a rectangular plate, wherein the rotor core comprises a plurality of permanent magnet insertion portions in which the permanent magnets are inserted, respectively, wherein the plurality of permanent magnet insertion portions are perpendicular to one another, wherein a center of at least one vent hole is positioned within a range of an electrical angle between 80° and 100° from a magnet central line of the rotor, and wherein a cross-sectional area of at least one vent hole corresponds to 6% to 8% of a cross-sectional area of the core.