Evaluation of the Magneto-Elastic Effect on the High-Speed Capability of Rotors in Synchronous Machines with Buried Permanent Magnets

Buried permanent magnets are secured against centrifugal forces by the rotor lamination sheets. The magnet bridges have to guarantee the mechanical strength of the rotor at high-speed operation. However, a large bridge thickness leads to increased leakage flux within the rotor, hence reduces the efficiency of the machine. The permeability of electrical steel reduces with mechanical stress due to the magneto-elastic effect. The consideration of this effect in the design process could allow larger bridge thicknesses and therefore increased mechanical strength at constant leakage flux. The effect is evaluated based on a V-arrangement of permanent magnets where the bridge thicknesses and the magnet angle are varied.