Structure of one-axis controlled repulsive type magnetic bearing system with surface permanent magnets installed and its levitation and rotation tests

This paper deals with a new bearing structure of one-axis controlled repulsive type magnetic bearing system that has a motor function of a surface permanent magnet (SPM). We evaluated the magnetic bearing structures by using the 4-pole 4-segment type and 4-pole Halbach array, which were placed around cylindrical permanent magnet sets as field magnets. The comparison of magnetic flux density in the radial direction measured by finite-element analysis indicated that the Halbach array has advantages over the 4-segment type in terms of the total harmonic distortion and internal magnetic influence. Additionally, levitation and rotation tests were performed by implementing each bearing configuration in a newly developed equipment. In both bearing configurations, stable levitation at zero-power position was established and high-speed rotation up to around 16000 rpm was achieved. As a result, the Halbach array slightly saved electric power. Its total input power to the motor was approximately 1.2 W.