In Plane Numerical Analysis of Mechanical Stress in a Synchronous Reluctance Machine

Abstract

The distortion due to the mechanical stresses from manufacturing issues and the operation of electrical machines are known to have adverse effect on the magnetic properties of electrical iron core and due to the stress dependency of iron core losses, it is therefore imperative that we account for the stresses from the different conditions causing mechanical stresses in a rotating electrical machine.

This work presents a 2-D FE-analysis of the mechanical stresses due to shrink fitting, centrifugal forces and the magnetic forces in a 4-pole, 3-phase synchronous reluctance machine at rated frequency of 50 Hz. The stresses due to shrink fitting and centrifugal forces were computed by solid mechanics method, while the stresses due to magnetic forces were computed using both magnetic field method and solid mechanics method. The total mechanical stress distributions from all stress sources were obtained using a weakly coupled approach. It was found that shrink fitting causes a very large tensile stress at the rotor core and compressive stress in most part of the stator yoke, but have almost no effect at the stator teeth. The centrifugal forces also contribute to the total tensile stress of the rotor core. The magnetic forces have the least effect on the total stress distribution of the machine.

The combined stresses obtained are mostly tensile at the rotor core and compressive at most part of the stator yoke, while the stator teeth were under low tensile stress due to the magnetic forces. The presence of flux barriers between flux paths at the rotor core causes large stresses to distribute at the bridge between flux barriers near the fit interface. Increase or decrease of the radial interference and/or frequency increases or reduces the total mechanical stress distribution of the machine.