Permanent magnet rotor

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PROBLEM TO BE SOLVED : To prevent the demagnetization of a permanent magnet, to prevent the failure of a sensorless start due to a reduction in the amount of a main magnetic flux, to prevent an increase in a starting current, and to prevent a drop in the efficiency of a motor in a permanent-magnet rotor which is constituted by burying a permanent magnet in every pole so as to be a concave shape toward the outer circumferential part of a rotor core. SOLUTION : Groove parts 20 which are cut out toward end parts are formed in such a way that narrow-width core parts are left between end parts of permanent magnets 3a, 3b on the outer circumferential part of every rotor core 2a. As a permanent magnet, a ferrite magnet material or a rare-earth magnet material is used. As its cross-sectional shape, a nearly arcuate shape, a nearly chevron shape or the like can be selected. The proper number of layers is buried and constituted in the radial direction of a rotor in every pole.