Magnetically levitated micro PM motors by two types of active magnetic bearings

This paper describes magnetically levitated micro permanent magnet (PM) motors by two types of active magnetic bearings. The micro PM motors consist of a cylindrical rotor (/spl phi/2.0 mm/spl times/10 mm), a pair of electromagnets, a pair of photodiodes, and an analog PD controller. The motors are characterized by the small rotor levitated without any mechanical contacts and one-axis controlled active magnetic bearing. Horseshoe-shaped and cylindrical electromagnets are applied to the active magnetic bearing. The rotor successfully rotates, levitating in the center of the electromagnets. In this paper, dynamic characteristics of the two types of micro PM motors, such as relationships between rotation speed and driving current, rotation speed and time, and acceleration and driving current, are discussed. As a result, it is found that the magnetically levitated micro PM motors by two types of active magnetic bearings are very different from each other and very promising.