This study estimates the axial magnetic suspension loss and efficiency of a one-axis actively positioned single-drive bearingless motor in the rotational speeds of 1000 to 30 000 r/min. Bearingless motors have the advantage of enhanced efficiency owing to the absence of friction loss caused by mechanical ball bearings. In this study, the input powers of a bearingless motor with radial passive magnetic suspension and that of a motor with ball bearings were measured. Moreover, the mechanical ball

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... bearing loss was also measured. Furthermore, the axial magnetic suspension loss in the single-drive bearingless motor was estimated. The efficiencies of both test motors were compared. Additionally, the ratios of the axial magnetic suspension loss and the ball bearing loss with respect to their input powers were evaluated.