Method for determining the expansion of a rotor and associated device

A device for determining expansion of a rotor of an electric machine, the rotor being supported by at least one magnetic bearing, the device comprising:

• an inductive position sensor measuring a position of the rotor,
• first determining means configured to determine a gap width separating the rotor from said inductive position sensor, said gap width being equal to a reference value of the gap width in a calibrating phase following installation of the rotor in the magnetic bearing,
• second determining means configured to determine the value of a current representative of the power being supplied to the inductive position sensor when the gap width separating the rotor from said inductive position sensor is equal to the reference value of the gap width, the value of said current being a reference value of said current in the calibrating phase following installation of the rotor in the magnetic bearing, and to determine the value of the current representative of the power being supplied to the inductive position sensor in a monitoring phase following at least one usage phase of the electric machine, and
• third determining means configured to determine the value of the expansion of the rotor based on the reference value of said current, on the present value of said current and on the value of the gap width.