Permanent magnet type motor and compressor comprising it

Abstract

For the purpose of preventing demagnetization of a magnet () without any cost increase and improving the max torque and the efficiency of an electric motor () by suppressing deterioration of magnetic flux density, a permanent magnet-type electric motor () comprises a stator () and a rotor () disposed in the stator (), in which a plurality of permanent magnets (), () forming a magnetic pole are inserted in magnet insertion portions (), () of a yoke () in such manner that the magnets (), () form in line in the circumferential direction thereof, wherein each magnet () is divided into a central magnet () that is positioned at the central portion in the width direction of the magnet insertion portion () and end magnets (), () that are positioned at end portions of the magnet insertion portion (), and the end magnets (), () have greater coercive forces than the central magnet (), whereas the central magnet () has a greater magnetic flux density than the end magnets (), (). Because the end magnets (), () easy to be demagnetized by the reverse magnetic filed caused by the stator current have greater coercive forces, demagnetization of the magnet () can be prevented as a whole. In the meantime, because the central magnet () difficult to be demagnetized has a greater magnetic flux density, the max torque and the efficiency of the electric motor () can be improved by such great magnetic flux density.