Suspension performance of a two-DOF actively positioned consequent-pole bearingless motor with a wide magnetic gap

A two-degrees-of-freedom actively positioned consequent-pole bearingless motor with a wide magnetic gap of 8 mm and a gap factor (gap/rotor radius) of 0.2 is proposed. Experimental results of the magnetic suspension tests at a rotational speed up to 6000 r/min have been demonstrated. The axial and passive stiffnesses are sufficient for stable magnetic suspension while rotation. To improve the suspension performance, the notch filter as a function of a rotational speed is applied into the control system to remove the undesirable periodic sensor noise, which is caused by interference between a sensor detection coil and the leakage flux from the consequent-pole rotor. The proposed variable notch filter has effects of the increased maximum speed and the decreased power consumption for magnetic suspension.