Magnetic flux estimate

A method for controlling a synchronous motor using a variable speed drive, the motor comprising a permanent magnet rotor generating a magnetic flux, the method comprising:

• when the motor is at rest, applying a predefined electrical command signal to the motor;
• estimating a motor speed in response to the applying of the predefined electrical command signal;
• iteratively adapting a value of the predefined electrical command signal as a function of an updated motor speed estimation at least until reaching a desired estimated motor speed that indicates that the motor is operating in a stable manner;
• waiting from when the predefined electrical command signal is applied when the motor is still at rest until reaching the desired estimated motor speed;
• in response to reaching the desired estimated motor speed, estimating a parameter related to the magnetic flux of the permanent magnet rotor, wherein the parameter is the magnetic flux of the permanent magnet rotor;
• recording the estimated parameter;
• and
• taking the recorded estimated parameter into account for driving the synchronous motor.