Using the Halbach magnet array to develop an ultrahigh-speed spindle motor for machine tools

摘要

This report describes the results of the authors' research on the optimum rotor configuration for an ultra high-speed machine tool spindle motor with a rated speed of 50,000 RPM and rated power of 11 kW. In this research, using an IPM (interior permanent magnet) motor with permanent magnets embedded in the rotor, they performed experiments based on calculations and a prototype machine to further clarify the optimum distribution of the permanent magnets in regard to both strength and magnetic path. Results indicate that to obtain the optimum rotor configuration for strength, the permanent magnets should be embedded at intervals of 60 degrees. Using this configuration, they repeatedly applied maximum stress at 50000 r/min (circumferential velocity was 233 m/s) and they were able to apply 57 kgf/cm, below the 82 kgf/cm breaking unit stress. Regarding magnetic stress, by optimum distribution of the Halbach magnet array at the boundary between the north and south poles, the authors were able to reduce torque pulsation to one half compared to not using the Halbach magnet array.