Built-in permanent magnet synchronous motor

The invention discloses a built-in permanent magnet synchronous motor. A plurality of pairs of magnetic poles are uniformly distributed in the circumferential direction of a rotor core; each magnetic pole comprises an inner-layer permanent magnet group and an outer-layer permanent magnet group which are arranged in the radial direction of the rotor iron core, wherein the inner-layer permanent magnet group and the outer-layer permanent magnet group are symmetrically arranged by taking a rotor straight shaft of the magnetic pole as a symmetric line, and the inner-layer permanent magnet group is made of a low-coercive-force permanent magnet material; the outer-layer permanent magnet group is made of high-coercivity permanent magnet materials, and the two ends of any inner-layer permanent magnet group and any outer-layer permanent magnet group are respectively provided with a magnetic isolation groove; by applying the device, the tooth groove torque generated by the magnetic poles of the inner-layer permanent mag