Performance improvement of a bearingless motor by rotation about an estimated center of inertia

Eccentric mass unbalance of the electric motor causes vibration of the shaft and the whole system, when the rotational speed increases. This paper considers rotation about an estimated center of inertia for a bearingless motor to reduce the vibration and power consumption for magnetic suspension. A 12-slot/10-pole bearingless SPM motor is selected for the performance test, because it has low suspension force ripple. The equation of motion for a bearingless motor with one-point mechanical support is derived. The mathematical model is derived to estimate the center of inertia. The prototype was built and tested, and the rotor rotates about an estimated center of inertia. The experimental results show effectiveness of the proposed method for performance improvement of the bearingless motor.