Abstract: Bearingless induction motors have been the focus of research work on high speed motors, as its rotor shaftcan be suspended by magnet ic force without conventional magnetic bear ings. Compared with magnetic bear ing motors, the axial lengt h of the rotor shaft is decreased, which results in an incr eased frequency of mechanical resonancein the flexible rotor and high power density. I n the paper, the principle of levitation force and the decoupling controlof torque and radial force ar e shown. An analog-digital hybrid controller based on DSP TMS320F240 is proposed.The t est results in a prototype motor validate t he per formance efficacy of the proposed contr oller in a steady state, aswell as in a transient state. And the maximum radial displacement is less than 50Lm.

Key words: bearingless induction motor, levitation, control system, prototype motor