Basic characteristics of a permanent-magnet type bearingless motor with positive salient pole

Various types of permanent-magnet type bearingless motors, which have integrated magnetic bearings with permanent magnet synchronous motors, have been developed actively. However, these motors cannot effectively generate electromagnetic suspension force for rotor shaft suspension, because suspension flux is attenuated owing to passing through high magnetic reluctance of permanent magnets. Accordingly, the authors have proposed a novel permanent-magnet type bearingless motor with positive salient pole that inductance L_d in the q-axis direction is greater than inductance L_q in the q-axis direction. In previous papers, it was shown with 2D-FEM that the proposed motor can generate the suspension force effectively, because the suspension flux does not pass through the permanent magnets. This paper introduces basic characteristics of torque and suspension force in the proposed motor with test results of a prototype machine.