Permanent magnet synchronous machines (PMSMs) can provide excellent performance in terms of torque density, energy efficiency and controllability. However, PMs on the rotor are prone to the centrifugal force which may break their physical integrity, especially at high-speed operation. Typically, PMs are bound with carbon fiber or retained by alloy sleeves on the rotor surface. This paper is concerned with the design of a rotor retaining sleeve for a 1.12-MW 18-krpm PM machine; its electromagnetic performance is investigated by the 2D finite element method (FEM). Theoretical and numerical analysis of the rotor stress are carried out. For the carbon fiber protective measure, the stresses of three PM configurations and three pole filler materials are compared in terms of operating temperature, rotor speed, retaining sleeve thickness, and interference fit. Then a new hybrid protective measure is proposed and analyzed by the 2D FEM for operational speeds up to 22 krpm (1.2 times the rated). The rotor losses and machine temperatures with the carbon fiber retaining sleeve and the hybrid retaining sleeve are compared and the sleeve design is refined. Two rotors using both designs are prototyped and experimentally tested to validate the effectiveness of the developed techniques for permanent magnet machines. The developed retaining sleeve makes it possible to operate MW PM machines at high speeds of 22 krpm. This opens doors for many high-power high-speed applications such as turbo-generators, aerospace and submarine motor drives.

Electromagnetic design of a 1.12-MW, 18,000-rpm high-speed permanent-magnet motor (HSPMM) is carried out based on the analysis of pole number, stator slot number, rotor outer diameter, air gap length, permanent magnet (PM) material, thickness and pole arc. The no-load and full-load performance of the HSPMM is investigated in this paper by using 2-D finite element method (FEM). In addition, the power losses in the HSPMM including core loss, winding loss, rotor eddy current loss and air friction loss are predicted. Based on the analysis, a prototype motor is manufactured and experimentally tested to verify the machine design.

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The high-speed permanent magnet(HSPM) machines are extensively concerned in industries due to simple structure, high power densityand high frequency. This paper introduces a kind of hybrid rotor with Halbach configuration and graphite composite sleeve. The hybrid cooling technology of stator water cooling and rotor fo rced air cooling is adopted to prevent the PM from demagnetization at high temperature. A HSPM machine with 1.12 MW, 18000 rpm fo r direct driving of compressors is designed based on the multi-physics coupled analysis such as electromagnetic / temperature / stress / fluid fields. The experimental measurements validate the correctness of some methods.

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