Rotor temperature monitoring method and system for permanent magnet synchronous motor

A system for monitoring a temperature of a rotor of a permanent magnet synchronous motor, comprising:

• a first current sensor configured to acquire an a-phase line current of a stator of the permanent magnet synchronous motor as a first line current;
• a second current sensor configured to acquire a b-phase line current of the stator as a second line current;
• a voltage sensor configured to acquire a line voltage between the a-phase and the b-phase of the stator;
• a tachometer configured to acquire a rotating speed of the rotor of the permanent magnet synchronous motor;
• and
• a calculation and derivation module configured to substitute the first line current, the second line current, the line voltage, the rotating speed, an inductance parameter of the permanent magnet synchronous motor and a temperature characteristic equation of a permanent magnet of the rotor into a preset rotor temperature expression, to calculate the temperature of the rotor,
• wherein the calculation and derivation module comprises:
• a first detection unit,
• a second detection unit, and
• a logic operation unit, wherein
• the first detection unit is configured to measure and record a current ambient temperature as a first rotor temperature under a condition that the permanent magnet synchronous motor is in a complete cold state;
• the second detection unit is configured to drag the permanent magnet synchronous motor to a rated rotating speed in an open-circuit state, and measure a line voltage of the permanent magnet synchronous motor as a first line voltage;
• the first detection unit is further configured to run the permanent magnet synchronous motor to rated power, and measure a temperature of the stator of the permanent magnet synchronous motor as a second rotor temperature after the temperature of the permanent magnet synchronous motor is stable;
• the second detection unit is further configured to, after the permanent magnet synchronous motor runs at the rated power, make the permanent magnet synchronous motor unloaded and keep the permanent magnet synchronous motor running at a rated rotating speed, and measure a line voltage of the permanent magnet synchronous motor as a second line voltage;
• and
• the logic operation unit is configured to calculate the temperature characteristic equation based on the first rotator temperature, the first line voltage, the second rotator temperature, the second line voltage and the rated rotating speed.