Rotor assembly and permanent magnet synchronous motor

The rotor assembly comprises a rotor iron core and a plurality of magnetic poles arranged at intervals in the circumferential direction of the rotor iron core, each magnetic pole comprises a fixed permanent magnet and a movable permanent magnet, and the fixed permanent magnets are arranged on the rotor iron core; the movable permanent magnet is movably arranged on the rotor core, the movable permanent magnet has a first position and a second position on the rotor core, when the movable permanent magnet is located at the first position, the magnetic field direction of the movable permanent magnet is the same as that of the fixed permanent magnet, and when the movable permanent magnet is located at the second position, the moving direction of the movable permanent magnet is opposite to that of the fixed permanent magnet; the movable permanent magnet can move from a first position to a second position under the action of centrifugal force. The size of the air gap magnetic flux during high-speed operation of the