Outer Rotor Consequent-Pole Bearingless Motor With Improved Start-Up Characteristics

In this paper, a novel structure of a prototype machine is proposed for enhanced start-up characteristics in a bearingless motor. The bearingless motor has two-axis active position regulation with only one unit. Passive magnetic bearings are constructed for improved stiffness in passively regulated movements. The passive magnetic bearings have influence in active two axis movements. A serious situation occurs at a start-up process from touched down condition. An optimization of machine design has been carried out in 3D-FEM analysis and an improved structure is proposed. Based on the design, a prototype bearingless motor is developed. It is shown that a successful start-up is achieved from the touch down displacement of 0.3 mm in experiment.