A Design Approach to Reduce Rotor Losses in High-Speed Permanent Magnet Machine for Turbo-Compressor

Recently, high-speed centrifugal turbo-compressors have been under intensive research and development. Since, compared to conventional compressors, high-speed centrifugal compressors have numerous qualities such as simple structure, light weight, small size, and high efficiency, etc. In order to maintain the mechanical integrity of a high-speed permanent magnet (PM) machine rotor intended for high-speed operation, the rotor assembly is often retained within a stainless steel or carbon-fiber sleeve. The sleeve is exposed to fields produced by the stator from either the slotting or the mmf harmonics that are not synchronous with the rotor. These non-synchronous fields cause the significant rotor losses. An optimum design of PM machines requires the accurate prediction for these rotor losses. On the basis of analytical field analysis and 2D finite element analysis (FEA), this paper deals with the rotor losses in high-speed PM machine. In particular, the difference of the rotor losses between the Inconel718 and Carbon-Fiber/Epoxy sleeve is quantitatively made clear in this work.