Rotor strength analysis for high speed permanent magnet machines

Permanent magnet (PM) of the rotor is not mechanically strong enough to bear the centrifugal force resulted from the high rotational speed in a high speed PM machine, therefore, a nonmagnetic alloy enclosure is needed to cover the PM material. In this paper, according to the strength calculation of the solid cylinder PM rotor in the high speed PM machine, the rotor stress condition was simplified as a plane stress problem, and the analytical formulae for rotor strength was proposed based on the displacement method in polar coordinates. Compared with the results of finite element method (FEM), the analytical formulae proposed can accurately predict the stress and displacement of the motor rotor with high speed and temperature rising.