Permanent magnet synchronous motor permanent magnet field loss diagnosis method, device and system

The invention provides an excitation loss diagnosis method, device and system for a permanent magnet of a permanent magnet synchronous motor, and the method comprises the steps: controlling an isolation contactor disposed between an inverter and the permanent magnet synchronous motor to start, so as to cut off the electrical connection between the inverter and the permanent magnet synchronous motor; the motor rotating speed of the permanent magnet synchronous motor is obtained, the line voltage of the permanent magnet synchronous motor collected by a voltage sensor is received, and the permanent magnet flux linkage value of the permanent magnet synchronous motor is determined according to the motor rotating speed and the line voltage; and obtaining a permanent magnet field loss diagnosis result according to the permanent magnet flux linkage value and/or the line voltage of the permanent magnet synchronous motor. The permanent magnet flux linkage value is calculated by directly measuring the line voltage of th