Rotor Natural Frequency in High-Speed Permanent-Magnet Synchronous Motor for Turbo-Compressor Application

For permanent-magnet synchronous motors driven by high-frequency drives, the rotor speed is normally above 30 000 rpm, and it may exceed 100 000 rpm. Designing high-speed motors from both in an electromagnetic and a mechanical aspect requires a different approach from designing conventional motors with low-medium operation speeds. This paper deals with rotor natural frequencies that are particular to high-speed permanent-magnet synchronous motors for turbo-compressor applications. It is very important to accurately predict rotor natural frequencies at the design stage in order to minimize operational failure. On the basis of the finite element method (FEM), this paper predicts the natural frequencies of a designed and manufactured permanent magnet rotor. The experimental results confirm the validity of the FEM calculations of the proposed design process.