Self-excitation and Speed Hysteresis of A Bearingless Slice Motor

In this paper we investigate the undesired self-excitation and speed hysteresis behavior observed in a dipole interior permanent magnet (IPM) bearingless slice motor. Experimental testings and finite-element analysis (FEA) indicate that a four-pole flux induced due to the rotor eccentricity can interact with four-pole suspension flux due to the winding currents to generate a self-excitation torque. This self-excitation torque can maintain rotor speed even if the torque command is zero. We resolve this issue by suppressing the peak of the suspension loop sensitivity function, so as to reduce the maximum rotor eccentricity during the rotation.