Rotor strength analysis of high-speed surface mounted permanent magnet rotors

Abstract

© 2016 Chin. Soc. for Elec. Eng.During high speed operation, permanent magnets (PMs) cannot withstand tensile stress due to the large centrifugal force, and an alloy enclosure is commonly employed to protect the permanent magnets. In order to ensure the safe operation of permanent magnet rotors, it is necessary to calculate the stress in the alloy enclosures and PMs. Because of the slim characteristic of high speed permanent magnet rotors, analytical expressions of stress, strain and displacement were deduced based on the theory of the thick-walled cylinder. The validity of the theoretic analysis was verified by the finite element method (FEM). Based on the derived analytic expressions, the influences of static interference, the thickness of alloy enclosures and shaft material character on strength were analyzed, and the general design guidelines were derived. Using a high speed PM machine of 30000r/min and 15kW as an example, the design method of high speed PM rotor strength and a basis for protective sleeve design are given.