Effective approach for calculating critical speeds of high-speed permanent magnet motor rotor-shaft assemblies

An effective approach is presented for large errors in calculating critical speed of rotor-shaft assembly with the commercial finite element software, is intended to develop the discrete model of the rotor-shaft assembly by using lumped mass method, which is supported by active magnetic bearings. The first two bending critical speeds are analysed by optimising the flexural rigidity coefficient based on transfer matrix method. Compared with experimental modal testing and finite element analysis, the results of the transfer matrix method are in good agreement with modal measurement, the percentage errors of the first two bending natural frequencies are 0.21 and 2.1%, respectively. Owing to the higher accuracy and numerical stability, the method used in this study is an effective way to calculate the critical speed of the rotor-shaft assembly.